Fibers doi: 10.3390/fib14050059

Authors: Ana Torre Pedro Espinoza Sorín Ramírez Luisa Shuan

Artificial intelligence (AI) has become a powerful tool for machine-learning-based forecasting from available data. This study evaluates several artificial neural network (ANN) architectures and the traditional multiple linear regression (MLR) method to predict the compressive strength of steel-fiber-reinforced concrete (SFRC). The input parameters considered in the models included electrical resistivity, concrete age, water-to-cement ratio (w/c), and cement content. Fifty-four concrete mixes were designed by varying the w/c ratio (0.45, 0.50 and 0.60), the nominal maximum size of the coarse aggregate (1″, 3/4″ and 1/2″) and the type of metallic fiber (Sika® Fiber CHO 65/35 [F1] and Sika® Fiber CHO 80/60 [F2]). Cylindrical specimens were cured in accordance with ASTM C31 and tested at 7, 14, and 28 days. Compressive strength was determined in accordance with ASTM C39. Electrical resistivity was measured at 7, 14 and 28 days using the Wenner method. Using this dataset, six ANN architectures were trained and the multiple linear regression (MLR) equation was calculated using Matlab R2018a software. The ANN models outperformed the MLR approach in predictive accuracy. Optimal performance was achieved with a three-layer ANN comprising 50 neurons in the first hidden layer, 20 in the second, and a single output neuron. The activation functions used were f(s) = tanh(s) for the first two layers and g(s) = s for the third layer. This ANN architecture achieved a correlation coefficient (R) of 0.98157 and the lowest error metrics, reported as percentages: mean absolute error (MAE), mean absolute percentage error (MAPE), mean squared error (MSE), and root mean squared error (RMSE) of 2.37%, 2.52%, 0.124%, and 3.52%, respectively. These findings demonstrate that ANN models can accurately predict the compressive strength of metal fiber reinforced concrete from electrical resistivity measurements and the variables mentioned above.

Fibers doi: 10.3390/fib14050058

Authors: Chanel Angelique Fortier Michael Santiago Cintron

There is growing concern about the ubiquitous presence of microfibers in waterways, atmosphere, and soil. Thus, the study of microfibers is of interest. Presently, there is no standard method for quantifying microfibers, so the objective of the current study was to employ a Fiber Quality Analyzer 360 (FQA) to examine microfibers with image analysis. In this study, two surfactants, Teric 169 and Surfonic LF-17, have been independently added to synthetic and natural microfiber suspensions to investigate their impact on arithmetic length and fiber count measurements. Herein, it has been observed that surfactants with pulsed sonication were shown to positively impact the synthetic microfibers suspensions, yielding statistically different higher fiber counts compared to the controls. However, the natural microfibers were found to produce fiber counts independent of the surfactant addition when compared to controls. In addition, the arithmetic lengths for polyester and nylon increased compared to a previous study, whereas the acrylic microfibers only changed marginally. Clearly, these results indicated that, with the pulsed sonication and surfactant addition pretreatment to water suspensions of microfibers, the FQA can be used to quickly and easily examine synthetic and natural microfibers in a single research study.

Fibers doi: 10.3390/fib14050057

Authors: Wafa Mahjoub Sarangoo Ukhnaa Jean-Yves Drean Omar Harzallah

Cashmere is recognized as one of the most valuable natural fibers due to its softness, fineness, and valuable properties. However, the production of fine cashmere yarns remains technically challenging due to the intrinsic variability of fiber characteristics and the presence of coarse guard hairs within the fleece. This study investigates the optimization of spinning conditions for the production of fine cashmere yarns by analyzing the influence of fiber preparation and spinning technology on yarn structure and performance. Cashmere fibers with an average diameter of approximately 16 µm were processed through several preparation stages to improve fiber alignment and reduce the proportion of short fibers. Yarns with linear densities ranging from 10 to 12.9 tex were produced using both conventional ring spinning and compact spinning systems. Yarn quality was evaluated through measurements of irregularity, yarn defects, tensile properties, and hairiness. The results indicate that improved fiber preparation significantly enhances sliver regularity and spinning stability, while compact spinning technology reduces yarn hairiness. However, the results also show that residual defects such as neps remain the main limiting factor for spinning performance, even under optimized conditions. The findings highlight the importance of optimizing both fiber preparation and spinning technology to enhance the spinnability and overall quality of fine cashmere yarns.

Fibers doi: 10.3390/fib14050056

Authors: Frederico Barbosa Filipe Miguel Margarida F. Domingues João Carlos Silva

The limited regenerative capacity of articular cartilage (AC) following injury has led to a high prevalence of degenerative AC-related disorders, including osteoarthritis (OA). Current clinical treatments for OA have failed to halt disease progression, driving growing interest in cartilage tissue engineering (CTE) strategies aimed at developing biomimetic substitutes to regenerate damaged AC tissue. Among the available biofabrication techniques, electrospinning has gained attention due to its ability to generate fibrous scaffolds that closely mimic the architecture of the native AC extracellular matrix, while also serving as versatile drug delivery platforms with high surface area and elevated drug loading efficiency. Small molecules, low-molecular-weight therapeutic agents capable of interacting with both cell membrane and intracellular components, can be incorporated into these scaffold systems to target the underlying mechanisms of OA. This review examines the current state of the art of small molecule-loaded electrospun scaffolds for CTE applications. Small molecules targeting pain, inflammation, and cartilage function restoration show considerable therapeutic potential, and their incorporation into coaxial and other advanced electrospinning setups enables controlled and sustained drug release. Recent examples of small molecule-loaded electrospun scaffolds for AC repair demonstrate enhanced chondrogenic differentiation and neo-cartilage formation, supporting their potential as viable CTE strategies. Nevertheless, challenges related to drug release kinetics, scaffold load-bearing properties, manufacturing scalability, reproducibility, and regulatory approval remain critical barriers to clinical translation. Emerging fabrication strategies, AI-assisted optimization, personalized medicine approaches, and stimuli-responsive drug delivery systems offer promising avenues to overcome these limitations and advance the clinical adoption of these platforms.

Fibers doi: 10.3390/fib14050055

Authors: Johnson I. Humphrey Stephen Dobreh Md Mostafizur Rahman Ayomide Sijuade Okenwa I. Okoli

The demand for materials that can operate reliably in extreme environments, including rocket nozzles, re-entry heat shields, sharp leading edges, high-velocity impact, and high-temperature energy systems, continue to drive advances in thermal–structural materials. Carbon/Carbon composites remain a leading baseline because of their low density, high-temperature mechanical retention in inert atmospheres, and excellent thermal-shock tolerance. However, long-term durability is constrained by rapid oxidation in air at elevated temperatures, limited fracture toughness and elastic modulus in many architectures, and high manufacturing cost driven by multi-cycle densification and stringent quality assurance. Consequently, contemporary strategies increasingly rely on modifying Carbon/Carbon composites with ultra-high-temperature ceramics and adopting accelerated or simplified manufacturing routes. This review synthesizes recent progress in the design, manufacture, and application of high-performance modified Carbon/Carbon composite systems for extreme aerospace environments, emphasizing composition/architecture selection, oxidation, and ablation protection, toughening concepts, and cost-aware densification. Because extreme environments performance is governed by coupled aerothermal loading, gas–surface chemistry, internal transport, recession, and thermomechanical response, the review also consolidates the multiscale modeling and software toolchains increasingly used to size thermal-protection systems, interpret experiments, and guide down-selection. Key challenges and future directions are further discussed for reusable materials and validated performances beyond ~2000 °C.

Fibers doi: 10.3390/fib14050054

Authors: Yakubova Dilfuza Turaev Khayit Alikulov Rustam Mukumova Gulvar Norkulov Fayzulla Kholboeva Aziza Ahatov Behzod

Healthcare-associated infections (HAIs) remain a significant global challenge, affecting approximately 7% of patients in developed countries and over 10% in developing regions, according to the World Health Organization. Medical textiles, particularly hospital bed linens and pillowcases, play a critical role in the transmission of pathogenic microorganisms due to their porous structure and moisture-retaining properties, which support microbial survival and proliferation, including bacteria such as Staphylococcus aureus and Escherichia coli. Conventional disinfection methods, including laundering and thermal treatments, provide only temporary protection, leading to rapid recontamination during use. In recent years, various antimicrobial agents and functionalization techniques have been developed to impart long-lasting antiseptic properties to textile materials. However, these approaches differ significantly in terms of antimicrobial efficiency, durability, cost-effectiveness, and environmental impact, making the selection of optimal strategies challenging for practical healthcare applications. This review provides a comprehensive comparative analysis of antimicrobial agents used in healthcare textile functionalization, including metal-based nanoparticles, organic compounds, and bio-based materials. In addition, it evaluates key modification methods such as coating, padding, and in situ synthesis, with particular emphasis on their influence on antimicrobial performance, wash durability, and practical applicability. Furthermore, this review discusses major challenges associated with the use of antiseptic coatings, including toxicity, environmental concerns, and economic limitations. Based on the analysis, promising directions for the development of safer, cost-effective, and durable antimicrobial textile systems are highlighted, offering valuable insights for future research and real-world healthcare applications.

Fibers doi: 10.3390/fib14050053

Authors: Azad Gull Anil Kumar Mysore Nagaraj Thomas Braxton Amit Kumar Dhaneshwar Padhan Rubia Bukhari Swathi Koppa Rameshjois Ravindra Aurade

Non-textile application of silk fiber is the major focus of the present scientific communities. Characteristics, i.e., structural, mechanical, are the key advantages of silk protein to make it promising candidates for its variable application. Keeping this in view, the present investigation has been conducted to understand the structural and mechanical variability of silk breeds, i.e., CSR2 × CSR4 (single hybrid), PM × CSR2 (cross breed) and FC1 × FC2 (double hybrid) for their respective promising non-textile application. It is envisaged that FC1 × FC2 (double hybrid) has the highest tensile strength (431.47 ± 28.46 MPa), Young’s modulus (5.92 ± 0.45 GPa) and β-sheet content (46.62 ± 1.45%). The lowest nano-crystallite size (3.34 ± 0.22) and elongation % (10.85 ± 0.77) were also observed in the FC1 × FC2. Further, significant positive correlation was observed between β-sheet with crystalline % (p *** < 0.001; r = 0.95), crystalline % with tensile strength (p *** < 0.001; r = 0.91) and Young’s modulus with tensile strength (p * < 0.001; r = 0.80). This indicates that the higher the β-sheet content is, the higher the tensile strength and higher crystalline phase of the fiber will be. Crystallite size has a negative correlation with the β-sheet content, crystalline %, tensile strength and Young’s modulus, which shows that the lower the crystallite size, the more the compactness and strength will be.

Fibers doi: 10.3390/fib14050052

Authors: Niwanthi Dissanayake Vidura D. Thalangamaarachchige Edward L. Quitevis Zeyad Zeitoun Noureddine Abidi

This study explores the influence of anion hydrogen-bond basicity, quantified by the Kamlet–Taft β parameter, on cellulose dissolution in imidazolium-based ionic liquids (ILs). A series of ILs sharing the common cation 1-benzyl-3-methylimidazolium were synthesized with varying anions, including chloride, acetate, formate, methoxyacetate, and methylphosphonate. The hydrogen-bond accepting ability (β) of each IL was experimentally determined and correlated with cellulose dissolution performance. Dissolution capability was evaluated by solubilizing 5 wt% cotton cellulose at 90 °C and monitoring under polarized light microscopy. Among the studied systems, 1-benzyl-3-methylimidazolium acetate (β = 1.01) demonstrated the highest dissolution efficiency, highlighting the critical role of strong hydrogen-bond basicity in disrupting the cellulose hydrogen-bonding network. To support the experimental observations, COSMO-RS simulations were conducted to probe the molecular-level interactions between anions and cellulose. Parameters such as anion size, theoretical density, viscosity, and surface charge density distribution were analyzed to elucidate their contributions to dissolution behavior. The regenerated cellulose was further characterized using scanning electron microscopy (SEM) and Fourier transform infrared (FTIR) spectroscopy.

Fibers doi: 10.3390/fib14050051

Authors: Maria Concetta Cocchiara María Isabel Prieto Alfonso Cobo Fernando Israel Olmedo

This research aims to study the compressive behavior of concrete with partial replacement of fine aggregate by recycled rubber. In addition, the mechanical capacity of these concretes will be analyzed when reinforced by carbon fibers (CFRP) and basalt (BFRP) confinement. To carry out the work, 48 cylindrical test specimens were made, corresponding to 4 mixes, with different percentages of recycled rubber by volume (0%, 10%, 20%, and 30%). The compressive behavior of unreinforced concrete with and without recycled rubber, reinforced concrete made from concrete with and without recycled rubber previously taken to failure, and reinforced concrete with and without recycled rubber without prior failure were evaluated in order to assess the influence of concrete quality before placing the reinforcement. The results show that replacing fine aggregate with recycled rubber in concrete reduces its strength and stiffness, increasing its ductility, with the optimum replacement percentage being 10%. On the other hand, confining concrete with FRP (BFRP and CFRP) improves its strength and ductility compared to unconfined concrete, obtaining similar values regardless of the initial strength of the reinforcing concrete. Confining concrete with CFRP achieves strength improvements of 26% compared to reinforcement with BFRP.

Fibers doi: 10.3390/fib14050050

Authors: Lahbib Abenghal Dan Belosinschi Hamid Lamoudan Aleksandra Mikhailidi François Brouillette

Natural fibers are among the most extensively exploited bio-based materials in industry due to their abundance, affordability, and biodegradability. However, their intrinsic properties often require improvement through chemical, mechanical, or enzymatic treatments to expand their applications. Phosphorylation is a highly effective chemical modification that enables the covalent grafting of phosphate groups onto the fiber backbone. These functionalities enhance hydrophilicity, anionic charge density, swelling capacity, and water uptake, while significantly improving flame-retardant performance. In addition, phosphorylation can reduce energy consumption and production costs in the manufacture of functionalized micro- and nanofibrillated fibers, as the increased swelling facilitates fibrillation. Consequently, phosphorylated fibers are suitable for water treatment, biomedical devices, construction materials, and other advanced materials. Dozens of reagents and various synthetic routes have been explored to perform this reaction, each producing materials with distinct properties. Phosphorus content remains the primary parameter used to assess modification efficiency. This literature review examines existing phosphorylation methods, including reagents, substrates, and characterization techniques, and discusses applications such as flame retardancy, thermal insulation, ion exchange, energy storage, electrodes, and battery recycling. It also briefly addresses key challenges, including limited hydroxyl accessibility, control of the degree of substitution, potential cellulose degradation, and scalability constraints.

Fibers doi: 10.3390/fib14050049

Authors: Fabíola Martins Delatorre Allana Katiussya Silva Pereira Gabriela Fontes Mayrinck Cupertino Álison Moreira da Silva Michel Picanço Oliveira Damaris Guimarães Daniel Saloni Ananias Francisco Dias Júnior

Polyester resin biocomposites containing biochar have attracted attention for improving mechanical strength and thermal stability while promoting sustainability. The pyrolysis temperature of biochar and its proportion in the polymer matrix are key factors affecting biocomposite performance. This study examined how biochar pyrolysis temperatures (400, 600, 800 °C) and incorporation levels (10, 20, 30 wt.%) influence the physical, chemical, mechanical, flammability, and morphological properties of polyester-based biocomposites. The samples were analyzed for density, water absorption, FTIR, XRD, flexural and tensile strength, ignition time, structural degradation, volumetric loss, and SEM microstructure. Biocomposites with 30 wt.% biochar produced at 800 °C showed the best mechanical properties, with a flexural strength of 95.3 MPa and an elastic modulus of 4417.4 MPa, representing increases of 14.5% and 45.7%, respectively, over the control. FTIR and XRD results revealed decreased aliphatic groups and increased aromaticity at higher pyrolysis temperatures, improving interactions between the matrix and biochar. These biocomposites also demonstrated enhanced thermal stability, with an ignition time of approximately 963 s, delayed structural degradation, and reduced volumetric loss (~19.3%). Overall, pyrolysis temperature and biochar content significantly influence the structural, mechanical, and thermal properties of polyester biocomposites, showing that biochar serves as a sustainable, performance-enhancing component in thermoset polymer matrices.

Fibers doi: 10.3390/fib14050048

Authors: Zahra Gholami Johan Persson Kateryna Liubytska Angeles Blanco Fritjof Nilsson Birgitta A. Engberg

Fibre properties significantly influence paper quality. This study investigates fibre property development along an industrial pulp production line, analysing morphological distributions and rheological behaviour to enhance refining performance indicators. Understanding these developments is critical for optimising resource efficiency and increasing industrial sustainability. Softwood thermomechanical pulp (TMP), from high-consistency (HC) and low-consistency (LC) refining, and bleached hardwood kraft pulp (BHKP) were examined. Fibre morphological properties were characterised using an optical fibre analyser, while suspension rheology was assessed using a pulp viscometer, supported by computational fluid dynamics (CFD) and discrete element method (DEM) simulations. Results demonstrate that fibre property distributions provide deeper insights into refining effects compared to average values alone. Systematic trends showed that HC-refined TMP from the first and second refining stage required significantly greater torque to break the fibrous network and fluidise the pulp compared to pulp that was also LC refined. This indicates that alterations in fibre properties, especially shortened fibre length resulting from different refining processes, govern fibre interactions in the three-dimensional network of the pulp suspensions and, therefore, their flow behaviour. In conclusion, combining morphological distribution analysis with specialised rheological measurements offers a robust tool for better understanding and monitoring mill-scale refining processes, enabling improved process optimisation in pulping and papermaking.

Fibers doi: 10.3390/fib14050047

Authors: Bianca Purgleitner Barbara Liedl Christoph Burgstaller

The global expansion of wind energy increases the need for sustainable recycling strategies for glass fiber-reinforced plastic (GFRP) from end-of-life wind turbine blades (WTB). Mechanical recycling is currently the most economically and ecologically viable technology. This study compares post-industrial (PI) waste from laminate cutoffs and post-consumer (PC) GFRP waste from end-of-life WTBs to investigate the influence of waste origin, pretreatment of shredded GFRP, different particle sizes and various matrix formulations on the tensile modulus and tensile strength of pressed bulk molding compounds produced with virgin epoxy resin. Thermogravimetric analysis showed a fiber content of up to 70 wt.%, but the resin residues on the embedded glass fibers dimmish a sufficient bonding of the new matrix system. Finer GFRP fractions consistently yielded higher tensile modulus and strength, with PI and pretreated PC materials performing best. The findings of this study demonstrate that controlled particle size distribution, impurity removal and optimized resin viscosity are key factors to achieve reliable mechanical performance and enable high-value recycling routes for glass fiber composite waste.

Fibers doi: 10.3390/fib14050046

Authors: Feng Yue Xiaofeng Xue

Fuel vapor can be ignited by lightning through various means, particularly through hot spot formation on fuel tank skins. The wing fuel tank cover and its surrounding outer plates together form part of the aerodynamic shape of an aircraft. The lightning protection design of the fuel system, including wing fuel tank, is of great significance for ensuring the aircraft safety. Based on the Joule heating and implosion effect, the damage response of a composite fuel tank cover subjected to lightning strikes is analyzed in this paper. The adopted method combines electrical–thermal coupling with explicit dynamics analysis. Firstly, a finite element model of the fuel tank cover is established using electrical–thermal coupling elements, and the lightning current impact simulation is carried out under given electrical boundary conditions and thermal boundary conditions. On one hand, the ablation criterion is determined by the Joule heating effect and the sublimation temperature of materials. The thermal damage of composite materials subjected to transient high currents is obtained through transient thermal analysis. On the other hand, special implosion elements are selected according to the temperature distribution obtained from the electrical–thermal coupling analysis. The original composite material model in the implosion region needs to be replaced with a new material model described by the high-explosive material model and the JWL equation of state. The von Mises stress distribution and pressure distribution on the structure after implosion are discussed in detail. The results show that concave pits are formed near the implosion zone. Unlike the thermal damage morphology defined by the ablation criterion, the implosion effect makes the damage distribution deviate from the initial fiber direction of each layer. The implosion dynamic method reveals the internal damage and pit and bulge phenomenon around the lightning attachment area to a certain extent.

Fibers doi: 10.3390/fib14050045

Authors: Pavlo Kryvenko Igor Rudenko Oleksandr Gelevera Oleksandr Konstantynovskyi

The paper deals with the concept of how to regulate structure formation in the interfacial transition zone (ITZ) between the Ordinary Portland Cement (OPC) matrix and basalt to ensure the durability of basalt fiber-reinforced concretes. It has been demonstrated that the alkali–silica reaction (ASR) can be transformed from a destructive (negative) process into a constructive one in OPC concrete through activation by sodium water glass combined with the incorporation of an Al2O3-containing additive, namely metakaolin. Alkaline activation increased the compressive strength of OPC basalt fiber-reinforced concrete by 1.6–1.9 times. The formation of stable zeolite-like hydration products within the Na2O-CaO-Al2O3-SiO2-H2O system promoted self-healing of the ITZ. This resulted in a 5.6-fold increase in ITZ microhardness compared to the cement matrix, as well as transforming expansion into shrinkage of concrete with a final value of 0.01 mm/m after 360 days. The structure-forming processes in the ITZ ensured a 1.14-fold increase in the compressive strength of 180-day alkali-activated OPC basalt fiber-reinforced concrete compared to its 30-day strength, in contrast to a 0.92-fold decrease in the strength of the non-modified OPC analog under conditions accelerating the development of ASR.

Fibers doi: 10.3390/fib14040044

Authors: Nusrat Bibi Imran Ahmad Khan Kashif Javed Asfandyar Khan Tayyab Naveed Mainul Morshed Fiaz Hussain Muhammad Junaid Saleem

This study investigates the fabrication of microcapsules using Nigella sativa (N.S.) oil as the core and alginate as the shell material. The N.S. oil microcapsules were prepared using the sol–gel method with different oil concentrations. The microcapsules were applied to the cotton fabric by the pad–dry–cure method, and their attachment was evidenced by scanning electron microscopy (SEM). Air permeability measurements were conducted for all developed samples, revealing that the sample with 8 g loading of N.S. oil and 4.5 g alginate exhibited a 43% reduction compared to the pristine sample. To further investigate the comfort characteristics of the samples, the functionalized cotton samples were subjected to the water vapor permeability index test. The results yielded an index value of 90, indicating that the encapsulation process preserved the comfort characteristics of the samples. Among the samples, the specimen with an oil concentration of 8 mL displayed the maximum antibacterial performance, achieving a 90% reduction in colony-forming units (CFUs) following quantitative testing protocol. However, the qualitative antibacterial assessment indicates no clear zone of inhibition, but no bacterial growth was observed on the samples. Furthermore, the fabric incorporating the maximum loadings of N.S. oil and alginate capsules exhibited the maximum antioxidant activity of 86.5%. These results underscore the critical role of N.S. oil microcapsules in enhancing the antibacterial and antioxidant properties of cotton fabric, while also revealing a harmony between functional performance and comfort characteristics.

Fibers doi: 10.3390/fib14040043

Authors: Yuan Fan Jiayi Zhang Zhaoqian Li Lingyun Wang Min Tang

Military confined spaces face poor ventilation and severe airborne hazards (toxic gases/particulates), while conventional air purification systems with separate filtration–adsorption units are bulky and hard to miniaturize. Activated carbon fiber paper (ACFP) is a promising integrated filtration–adsorption material, but existing studies lack systematic comparisons of different ACF precursors and rational balancing of adsorption, filtration, and mechanical properties. Herein, ACFPs were fabricated via wet papermaking technology, using two ACFs (rayon-based, RACF, and phenolic-based, PACF) as the adsorptive component, glass wool as a filtration enhancer, and dual-melting-point polyethylene terephthalate (PET) fibers as a mechanical reinforcer. Dynamic adsorption was evaluated via DMMP (a Sarin simulant). Results showed that PACF had a micropore ratio twice that of RACF. Under the optimal formulation (20% glass wool, 30% PET, and 50% ACF), both types of ACFP showed FE0.3 μm ≥ 90%. PACFP outperformed RACFP in comprehensive performance, showing higher adsorption capacity, tensile strength, and filtration quality factor. Both ACFPs exhibited superior bed utilization efficiency (RACFP: 91.3%; PACFP: 86.0%) to granular activated carbon (AC: 82.7%), confirming better dynamic adsorption kinetics. This work provides a rational optimization strategy for ACFPs, offering a lightweight, integrated material for air purification in military confined spaces.

Fibers doi: 10.3390/fib14040042

Authors: Se Jin Kim So Hee Shin Dong Ok Shin Won Jun Lee

Conventional separators for lithium metal batteries suffer from poor thermal stability, flammability, and limited mechanical strength. In this study, we report a self-reinforced aramid separator integrated with Li7La3Zr2O12 (LLZO) via a sodium–naphthalene-based selective dissolution strategy. Controlled partial disruption of hydrogen bonding in copolymerized aramid enables the formation of a hierarchical structure consisting of intact fibers and nanofibrillar networks, thereby providing intrinsic mechanical reinforcement without binders. The separator maintains structural integrity up to ~400 °C and retains over 70% weight at 600 °C, exhibiting self-extinguishing behavior (LOI > 30). Puncture strength is more than three times higher than Celgard®, while LLZO integration doubles the ionic conductivity along with excellent electrolyte wettability. This synergistic design provides a promising route toward intrinsically safe and high-performance lithium metal battery separators.

Fibers doi: 10.3390/fib14040041

Authors: Md Mazedur Rahman Md Ahad Israq Szabolcs Szávai Saiaf Bin Rayhan Gyula Varga

The present study investigates simple cubic lattice structures fabricated through an FDM-based three-dimensional (3D) printing method using wood–polylactic acid (wood–PLA) bio-composite filament and develops a data-driven framework to predict their mechanical response. The design of experiments (DOE) was developed using a response surface methodology (RSM) based on a central composite design (CCD) that was implemented in Design-Expert software (Version 13). During fabrication, four different manufacturing parameters—the layer height, the printing speed, the nozzle temperature, and the infill density—were considered. The compressive strength and compressive modulus were evaluated experimentally, and the corresponding stress–strain responses were examined. The results reveal that the layer height is the most influential parameter, where lower layer heights (0.06–0.1 mm) significantly improve both the compressive strength and the modulus due to enhanced interlayer bonding and reduced void formation. The printing speed and the nozzle temperature also play critical roles, where lower printing speeds (≈40 mm/s) and moderate nozzle temperatures (≈195–205 °C) promote more uniform material deposition and improved interlayer bonding, while higher speeds (≥60 mm/s) and excessive temperatures (≈225 °C) lead to reduced bonding quality and a deterioration in mechanical performance. In contrast, the infill density exhibited a non-monotonic influence, where intermediate levels (around 70%) provided an improved performance under combinations of the low layer height (≈0.1 mm), the low printing speed (≈40 mm/s), and the moderate nozzle temperature (≈195–215 °C), suggesting an interaction-driven effect rather than a purely density-dependent trend. To complement the experimental findings, a machine learning model based on eXtreme Gradient Boosting (XGBoost) was developed using 12,000 data points that were derived from stress–strain curves. The model successfully predicted continuous mechanical responses with errors in the range of 2–8% for unseen specimens, suggesting its capability to capture the relationship between printing parameters and mechanical behavior within the studied design space. Overall, the study highlights that the mechanical properties of wood–PLA lattice structures can be effectively tailored by choosing an appropriate printing parameter control and demonstrates the feasibility of using machine learning to estimate mechanical performance without additional physical testing within the defined parameter domain.

Fibers doi: 10.3390/fib14040040

Authors: Lihui Yin Zhu Yuan

This paper presents a systematic investigation into the long-term mechanical property development, water absorption behavior, and microstructural characteristics of hybrid glass and polypropylene fiber-reinforced concrete (HGPFRC). The findings provided valuable engineering construction solutions for holistically considering the improvement effect of hybrid fibers on concrete performance and for the durability design of concrete materials. The main conclusions of the study are as follows: the water-to-binder ratio (w/b) and the hybrid fiber content significantly influenced the development rate of compressive strength in concrete. Compared to the control group without fibers, the compressive strength of HGPFRC increased more rapidly during the curing stage from 7 to 28 days. HGPFRC with different w/b and fiber contents exhibited significant differences in water absorption rates at various testing stages. In this study, the water absorption of HGPFRC reached 60% to 86% of the total absorption on the first day, 6% to 23% from the second to the fourth day, and 3% to 18% from the fifth to the thirty-first day. Considering the compressive strength, water absorption performance, and microstructure observed via SEM, the optimal mix proportion for the HGPFRC in this study was determined to be a w/b of 0.35 and a hybrid fiber content of 1.8%. The hybrid glass and polypropylene fiber content of 2.7% used in this study exceeded the optimal dosage, and the resulting concrete could not meet engineering construction requirements.

Fibers doi: 10.3390/fib14040039

Authors: Tishager Taye Teriya Hirpa G. Lemu Endalkachew Mosisa Gutema

The objective of this study is to review the literature on the natural resources needed for biodegradable materials underscoring the importance of natural fiber-based composites as a feasible alternative. The review focuses on the pivotal role of natural fiber-based composites in the formulation of industry benchmarks, the challenges associated with application of natural fibers, the application areas, and the mechanical properties as well as the determinants influencing the properties of the composites. The manufacturing methods were discussed and compared. In addition, the study highlights the successful instances where enset fiber-based composites have been adeptly implemented. The study also observed potential areas of future research to improve the performance of enset fiber-reinforced composites including the fabrication techniques and treatments. Hand lay-up and compression molding are the conventionally used composite fabrication methods, while the recent advances in 3D printing for composite fabrication bring new opportunities to solve many of the existing limitations. In addition, most research is currently limited to alkali treatment, whereas other fiber treatment techniques could further improve the mechanical performance by modifying the surface properties and removing the impurities. Moreover, hybridization, orientation of fiber, and addition of nano-particles are observed to have direct impact on the composite properties. The review scrutinizes comprehensive examination of the prevailing landscape and prospective courses for enset fiber applications within the realm of sustainable material science, utilizing diverse processing techniques and applications while pinpointing inherent challenges.

Fibers doi: 10.3390/fib14030038

Authors: Andrea Marangon Elisa Calà Alessandro Bessi Alessandro Croce Enrico Avattaneo Eleonora Cara Giorgio Gatti

In recent years, there has been a notable increase in commercial demand for natural fibers. Consequently, numerous studies have concentrated on formulating innovative industrial production methodologies for natural fibers, with a particular emphasis on the environmental sustainability of production processes. Among natural fiber sources, bamboo has emerged as a leading candidate, attracting considerable interest due to its exceptional renewability, rapid growth, and low cultivation requirements. The contemporary industrial methodologies employed in the extraction of cellulose from bamboo frequently entail the utilization of concentrated solutions of strong acids and bases, often at elevated temperatures and with extended treatment durations. These processes generate highly polluting waste from mineral acids and bases, posing significant environmental challenges and ecosystem damage. In response to the prevailing concerns, there has been a marked increase in the focus on environmentally friendly techniques that combine enzymatic treatments, selective chemical reagents, and optimized mechanical processes. These processes facilitate the extraction of high-quality bamboo fibers, which are suitable for utilization in the textile industry and have the potential to replace synthetic fibers. This work demonstrates the efficacy of methodologies employing more diluted solutions than conventional approaches. Specifically, this study utilizes a weak base, such as NH4OH, in conjunction with hydrothermal extraction. It is therefore possible for dilute weak base solutions to yield natural fibers after a relatively brief period of processing, typically just a few hours.

Fibers doi: 10.3390/fib14030037

Authors: Jinming Zhang Yiyang Xu Dongfang Wang Qian Li

After implantation in vivo, airway stents are prone to negative biological effects, such as platelet adhesion, aggregation, and blood coagulation, which may lead to vascular occlusion and thrombosis. Therefore, when studying the antithrombotic properties of vascular grafts, it is crucial to construct a fiber film-coated airway stent with antithrombotic properties. In this paper, PTFE/TPU fiber film was prepared by emulsion electrospinning, and heparin aldehyde group was modified to covalently graft with the fiber film to obtain heparin-loaded fiber film (Hep-PT fiber film), and a heparin-loaded PTFE fiber film-coated airway stent (Hep-PT fiber film-coated airway stent) was prepared. Covalent grafting improves the stability of heparin and promotes the long-term stable release of heparin. The loading of heparin increases the fiber nodes between the fiber films, increases the friction between the fibers, and improves the mechanical properties and ability of the fiber film to resist external forces. At the same time, the Hep-PT fiber film-coated airway stent exhibits excellent cytocompatibility, making it an ideal candidate system for airway stent materials.

Fibers doi: 10.3390/fib14030036

Authors: Aman Ul Azam Khan Nazmunnahar Nazmunnahar Mehedi Hasan Roni Aurghya Kumar Saha Zarin Tasnim Bristy Abdul Baqui Abdul Md Mazid

Conductive thread is an integral aspect of smart textiles in the domain of electronic textiles (e-textiles). This study unveils the development of twelve distinct variants of conductive threads using the twisting method: the fusion of copper filament with cotton and polyester threads. The threads are coated with a carbon paste solution enriched with dissolved sea salt. The carbon paste is obtained from non-functional dry cell batteries, conventionally categorized as hazardous electronic waste (e-waste), which underscores an economically viable and environmentally sustainable approach. Experiments proved that each variant demonstrates minimal electrical resistance. The lowest resistance, 0.0164 ± 0.0001 Ω/cm, was achieved by Carbon-Coated Cotton Twisted Copper Thread-II. Comparative evaluation with commercially available conductive threads, including Bekaert Bekinox® VN type (12/1x275/100z), indicated comparable or moderately lower resistance values for the developed copper-based threads. Mechanical–electrical stability under bending, twisting, and wash–dry cycles confirmed consistent conductive performance with minimal resistance variation. Practical demonstrations further validated the integration of the threads into fabric-based flexible circuits and wearable electronic systems. These findings demonstrate that twisted copper-based conductive threads derived from sustainable coating materials provide a promising alternative for smart textile and wearable electronic applications. Future research should focus on scalable fabrication, enhanced coating fixation, and long-term durability assessment.

Fibers doi: 10.3390/fib14030035

Authors: Izabela Jasińska Alicja Nejman Beata Tkacz-Szczęsna Sandra Flinčec Grgac

Textile fabrics intended for use in protective clothing, workwear, and uniforms are subjected to repeated high-temperature industrial washing and drying processes. It is evident that due to the rigorous nature of the prescribed preservation conditions, textiles that are currently utilised for this purpose do not contain elastomeric yarns: a consequence of their suboptimal thermal stability. However, elastomers enable garments to better fit the wearer’s figure and enhance safety and comfort during occupational activities. Currently, no investigations of EOL (elastolefin) yarn elastic durability under commercial maintenance conditions have been conducted. The publication evaluates the elastic properties and pilling resistance of fabrics with EOL-core weft yarns before and after repeated industrial washing under conditions that are typical of rental use. Additionally, an analysis using SEM, FTIR spectroscopy, thermal and thermogravimetric techniques of core-yarns and the core itself was performed. The tested fabrics retained a high elasticity index, even after 100 industrial washing cycles, as confirmed by instrumental analysis. In conclusion, fabrics with EOL-core yarns can be used for garments that are subjected to intensive maintenance in industrial washing conditions without losing their elastic properties.

Fibers doi: 10.3390/fib14030034

Authors: Karolina Lipska Izabela Betlej Agnieszka Laskowska Piotr Boruszewski

The development of composite materials based on post-consumer polymers and agricultural residues is a pragmatic valorization approach that extends the lifetime of materials. This research aimed to analyze the selected physical and mechanical properties of post-consumer-polyethylene-based composites with lignocellulosic fillers. This study explores the ‘ready-to-use’ valorization of untreated oilseed pomaces. The polyethylene ratio was set at 30% and 40%. Wood particles were substituted with oilseed pomace from nigella, rapeseed and evening primrose. The content of the pomace replacing wood particles was 30%, 65% and 100%. The composites made of post-consumer polyethylene and wood particles were used as a reference. The manufacturing process utilized a hybrid approach, combining extrusion with flat pressing. Increasing pomace content generally reduced the modulus of rupture and modulus of elasticity. Surface roughness decreased with higher pomace addition, except for the 30% rapeseed content for the lower polyethylene ratio, i.e., 30%, which showed unusually high roughness. Higher pomace content improved surface wettability, particularly for nigella-based composites. Water absorption and thickness swelling after 2 h and 24 h of soaking were highest at 30% pomace content and decreased with increasing substitution levels. Evening primrose composites consistently exhibited the lowest water uptake and swelling.

Fibers doi: 10.3390/fib14030033

Authors: Beata Anwajler Krystian Grabowski Tullio de Rubeis Monika Nowakowska Paweł Leśniewski Jacek Kasperski

Construction technologies and materials engineering are collaborating to develop new solutions that enhance energy efficiency. One such solution is thermal barriers filled with phase change material. Thanks to their thermal properties, these innovative barriers are being used in an increasing number of construction projects. Additive manufacturing enables the production of architected thermal barriers with controlled cellular topologies and customized heat transfer pathways. This study investigates the thermal performance of lightweight partitions produced using masked stereolithography (m-SLA) 3D printing, focusing on two geometries: open-cell Kelvin structures and closed-cell honeycomb structures. Two strategies for incorporating phase change material were evaluated: direct addition of 10% and 30% paraffin oil by weight to the photopolymer resin and post-print filling of cellular voids with a PCM-based gel. The aim was to establish the effect of topology and PCM distribution on steady-state thermal parameters and transient temperature stabilization. Experimental testing under cyclic heating–cooling conditions revealed that increasing paraffin oil content significantly improves thermal performance. The open-cell Kelvin structure with 30% PCM exhibited the lowest thermal conductivity (λ = 0.0289 W/(m·K)) and the highest thermal resistance (R = 0.697 m2·K/W). Honeycomb structures achieved λ = 0.0360 W/(m·K) and R = 0.590 m2·K/W at the same PCM content. Transient analysis demonstrated enhanced temperature stabilization, with maximum ΔT values of 29.55 K (30% PCM) and 28.61 K (honeycomb 30%). These results confirm that the geometry produced by additive manufacturing plays a decisive role in governing heat transfer and latent heat utilization in PCM-based thermal barriers.

Fibers doi: 10.3390/fib14030032

Authors: Mária Petková Marcela Hricová Viera Jančovičová Zita Tomčíková Anna Ujhelyiová

This work presents the preparation and obtained results of the properties of biodegradable-oriented systems of dyed polymer by biocolorants in mass. The oriented systems (films) were prepared from biodegradable material Nonoilen. Our applied research is focused on preparing masterbatches using inorganic, organic, and food-nature pigments to prepare films as packaging materials. Inorganic pigments, such as iron and titanium oxide, and organic pigments were selected to maintain the biodegradability of the polymer mixture, as the manufacturer declares the biodegradability of the selected pigments. The food-natural pigments are extracted from plants and food pigments, such as chlorophyll, caramel, and violets. First, rheology was evaluated to verify the processing conditions of the materials, and then the properties of the prepared films were examined. Mechanical properties, supermolecular structure, and coloristic properties were assessed for the pure and dyed films. We investigated color fastness after accelerated thermal-light aging using Q-SUN equipment. Food-nature pigments showed sufficient colorability after preparation, although the coloration was lost relatively quickly after accelerated light aging. If they are used as food packaging materials, these pigments would be highly safe for health, in addition to being biodegradable. The color stability of inorganic and organic pigments reached high stability values even after accelerated aging.

Fibers doi: 10.3390/fib14030031

Authors: Askar Abdykadyrov Amandyk Tuleshov Nurzhigit Smailov Zhandos Dosbayev Sunggat Marxuly Yerlan Tashtay Gulbakhar Yussupova Nurlan Kystaubayev

In recent decades, the reliability and safety of large engineering structures have become a critical issue due to failures caused by undetected micro-level deformations. Fiber-optic strain sensors, especially Fiber Bragg Grating (FBG) and interferometric systems, are widely used in structural health monitoring (SHM); however, their standard sensitivity is often insufficient for early detection of nano-strain level damage. This paper presents a comparative analysis and system-level optimization of the main sensitivity enhancement methods, including mechanical amplification, functional coatings and composite embedding, interferometric schemes, and advanced spectral signal processing. Analytical modeling and numerical simulations were performed. It is shown that flexure-beam amplifiers provide a stable sensitivity gain of 2.1–4.8, whereas lever-type mechanisms achieve higher amplification (5.6–9.3) at the cost of dynamic degradation. Functional coatings increase the strain transfer coefficient from 0.62 to 0.68 to 0.91–0.97, but introduce temperature-induced errors up to 1.5–2.0 µε. Interferometric systems can detect strains at the 10−8 level but exhibit high temperature cross-sensitivity. Advanced spectral processing reduces the Bragg wavelength estimation error by 8–15 times, improving the equivalent strain resolution to (2–5) × 10−8. Based on these results, an optimized integrated approach combining moderate mechanical amplification (2.5–3.5), improved strain transfer (η ≈ 0.85–0.92), and efficient spectral processing is proposed. This improves the equivalent strain resolution from 1 × 10−6 to (1.5–3.0) × 10−8 while keeping temperature-induced errors within 15–25% and limiting the computational load increase to 2–3 times. The proposed solution is suitable for long-term monitoring of large engineering structures.

Fibers doi: 10.3390/fib14030030

Authors: Eduardo J. Mezquida-Alcaraz Juan Navarro-Gregori Pedro Serna

This study presents a reliable methodology for analyzing reinforced ultra-high-performance fiber-reinforced concrete (UHPFRC) elements by linking material behavior to structural performance. A non-linear finite element model (NLFEM) is proposed to simulate the tensile response of reinforced UHPFRC elements, with particular emphasis on shrinkage effects. The model operates in two phases: the first simulates shrinkage during specimen storage and the second simulates the mechanical tensile test, using the internal stresses from the first phase as initial conditions. The model was validated through an experimental program involving reinforced UHPFRC ties. The NLFEM accurately reproduced the load–displacement response using average UHPFRC tensile parameters obtained from a simplified Four-Point bending test Inverse Analysis method (4P-IA). It reliably predicted the shrinkage strain range and its impact on stiffness loss during microcrack initiation and stabilization, where tension-stiffening behavior is critical. Additionally, the simulation from the model captured the transition from microcracking to macrocrack formation and the role of fiber bridging in maintaining stiffness. The predicted shrinkage strain aligns with values reported in the literature and represents a conservative upper bound, neglecting the potential effects of creep and relaxation. Overall, the NLFEM effectively simulates the full tension-stiffening behavior of reinforced UHPFRC, including three-dimensional effects, and provides a reliable tool for structural analysis and design.

Fibers doi: 10.3390/fib14030029

Authors: Matthew Davidson Ryan Graunke Aidan Green Hayden Haelsig Laura Heinemann Subin Antony Jose Pradeep L. Menezes

Carbon Fiber-Reinforced Polymer (CFRP) composites represent a transformative class of structural materials, combining low density, high specific strength, and excellent fatigue resistance. This review provides a comprehensive overview of CFRPs, addressing their structure, manufacturing routes, mechanical performance, and functional behavior, with particular emphasis on damage tolerance, tribological properties, and environmental durability. The discussion begins with the classification and morphology of carbon fibers, highlighting their influence on composite anisotropy and interlaminar behavior. The effects of impact loading, delamination, and environmental conditioning on residual strength and fatigue life are then examined, with reference to established evaluation methods such as ASTM D7136 and compression-after-impact (CAI) testing. From a tribological perspective, the incorporation of nanoscale additives, such as graphite nanoplatelets and TiO2 nanoparticles, and their contribution to enhancing wear resistance by promoting the formation of stable tribofilms, is explored. Advances in processing techniques, including low-pressure curing and improved resin systems, are also discussed for their roles in enhancing manufacturability and energy efficiency. Overall, the review underscores that optimal CFRP performance is achieved through the synergistic integration of fiber architecture, matrix design, and precise processing control, while future progress in nanomodification, recycling, and sustainable curing technologies is expected to further expand CFRP applications in the aerospace, automotive, and high-performance engineering sectors.

Fibers doi: 10.3390/fib14030028

Authors: Yingying Tao Yanmei Zhang Chuan Zhao Changlei Bu Rui Zhang Qikai Wang Qingzhe Yi Fuxin Wu Yanchang Zhu Yongxiang Fang

High-strength concrete (HSC) is vital for large-scale tunnel infrastructure; however, its durability is often compromised by rigorous freeze–thaw cycles in cold-region environments. This study investigates the synergistic effects of incorporating hybrid steel fiber (SF) and polypropylene fiber (PPF) to enhance the frost resistance of HSC. Experimental testing involved 125 freeze–thaw cycles across various fiber dosages and lengths, monitoring mass loss and the relative dynamic modulus of elasticity. Additionally, a concrete damage plasticity (CDP) model was utilized in numerical simulations to analyze thermal stress distribution and damage evolution under coupled freeze–thaw and axial loading. Results indicate that the hybrid fiber integration significantly improved durability, with Group A3 (35 kg/m3 SF and 1.5 kg/m3 of 18 mm PPF) achieving the highest performance. After 125 cycles, Group A3 maintained a relative dynamic modulus of 94.5% and restricted mass loss to 1.42%, a 41% improvement over the fiber-free control. Numerical simulations corroborated these findings, demonstrating that the dual-fiber system preserves load-bearing capacity, limiting compressive strength degradation to just 6.7%. These findings quantitatively validate the synergistic mechanisms of hybrid fibers, providing a robust reference for designing high-durability concrete in cold-climate engineering applications.

Fibers doi: 10.3390/fib14020027

Authors: Sana Ullah Salvatore Benfratello Carmelo Sanflippo Luigi Palizzolo

The rising environmental concerns over cement-based construction materials have led to the development of sustainable alternatives. Among these, geopolymers represent a promising class of low-carbon binders offering environmental benefits and competitive mechanical properties; however, their intrinsic brittleness limits their tensile and post-cracking performance. This study investigates the adoption of flax fibers as natural reinforcement to enhance ductility and post-peak behavior of metakaolin-based geopolymers. The performance of metakaolin-based geopolymers with flax fibers (MKFLAX) was experimentally evaluated in terms of strength, stiffness, toughness, and failure behavior. The addition of flax fibers enhanced ductility, toughness, and post-peak load-carrying capacity while slightly improving stiffness due to the bridging of cracks and the fiber pull-out mechanism. In comparison with the available literature on sisal, flax, and jute fibers, flax fibers showed improved performance due to the better dispersion within the matrix and higher tensile modulus. These findings highlight that flax fiber-reinforced metakaolin geopolymers show enhanced post-cracking behavior at the laboratory scale and could be of interest for sustainable cementitious materials, subject to further validation at the structural scale. Furthermore, a nonlinear finite element model was adopted based on damage mechanics to simulate the damage localization, stress–strain response and post-peak behavior of geopolymer composites. The numerical results showed a reasonable agreement with the experimental trends, particularly in the elastic and early softening phases. The findings are limited to the studied material system, fiber content, and small-scale samples and should be viewed as trend-level observations rather than generalized performance claims.

Fibers doi: 10.3390/fib14020026

Authors: Chunquan Hong Jincheng Wen Huailiang Liu Libo Wang Lin Zhang Xiuquan Ma

Laser slicing of 4H-SiC wafers offers high efficiency and minimal material loss. While nanosecond lasers are the preferred light source, simultaneously achieving high output power, excellent beam quality (M2 < 1.3), and broad operational tunability remains an outstanding challenge. This study developed a highly efficient nanosecond laser source using hybrid fiber and solid-state multi-stage amplification architecture. With excellent beam quality (M2 < 1.3), it achieves the highest output power, widest continuously tunable pulse width range, and broadest repetition rate range currently reported for 4H-SiC laser slicing. This advancement is poised to advance the continued development of 4H-SiC slicing technology.

Fibers doi: 10.3390/fib14020025

Authors: Buda Rocco Pucinotti Raffaele

The seismic vulnerability of existing reinforced concrete buildings is often exacerbated by the inadequate mechanical performance of non-structural components, such as masonry infill walls, which may exhibit brittle behavior and limited deformation capacity under seismic actions. This issue highlights the need for innovative and compatible strengthening materials capable of improving ductility and damage tolerance while maintaining adequate mechanical strength. This study presents an experimental investigation aimed at developing a sustainable fiber-reinforced plaster manufactured exclusively from locally sourced natural materials from the Calabria region, including cork granules, broom fibers, and natural hydraulic lime. Following a preliminary experimental phase, the mixture containing 30% cork granules was selected as the reference matrix due to its favorable mechanical performance and deformability. In the present phase of the research, several composite formulations incorporating broom fibers were produced and experimentally characterized. Uniaxial tensile tests were conducted on broom fibers to assess their reinforcing potential, while compressive and flexural tests were performed on the plaster matrices. The experimental results show that the incorporation of broom fibers significantly enhances flexural behavior and post-cracking ductility, while maintaining compressive strength levels compatible with structural retrofit applications. The study demonstrates that the combined use of cork and broom fiber effectively enhances the mechanical performance of the plaster by promoting ductility, improving flexural behavior, and limiting crack initiation and propagation. The high tensile strength of the fibers promotes effective crack-bridging mechanisms and improved energy dissipation capacity. Overall, the combined use of cork aggregates and broom fibers results in a mechanically balanced plaster composite characterized by enhanced deformability and reduced brittleness. These features make the proposed material particularly suitable for the strengthening of masonry infill walls and for applications where improved ductility and damage tolerance are required, such as seismic retrofitting and restoration of existing buildings.

Fibers doi: 10.3390/fib14020024

Authors: Ramia Almohamad Jean-Yves Drean Laurence Peschel Omar Harzallah

This study evaluates the textile potential of five underexplored Agave varieties (Agave salmiana crassispina, A. salmiana salmiana, A. ingens marginata, A. tecta, and A. mapisaga) through combined analyses of extraction behaviour, microstructure, and single-fibre mechanical performance. Fibres extracted from basal, middle, and upper leaf sections were characterised using scanning electron microscopy (SEM) and single-fibre tensile testing under controlled conditions. All varieties produced spinnable fibres and exhibited significant longitudinal variability in mechanical behaviour along the leaf axis (p < 0.05). Mechanical performance depended strongly on both species and leaf position, with fibres from the middle leaf section generally showing higher tenacity. Variations in Young’s modulus reflected differences in fibre maturity and internal microstructural organisation. Fractographic observations revealed predominantly brittle fracture with microfibrillar rupture and longitudinal fibrillation. Overall, the results demonstrate that agave species and leaf position are key parameters governing fibre performance. These agave varieties therefore represent promising candidates for sustainable textile applications, provided that appropriate fibre selection and blending strategies are implemented to ensure homogeneous yarn properties.

Fibers doi: 10.3390/fib14020023

Authors: William G. Davids Aidan G. McGlone

In this paper, the impact of shear deformations on the load–deflection response of transversely loaded inflatable panels made from drop-stitch fabric is explored. A nonlinear shear constitutive model was derived from torsion tests and integrated into Timoshenko beam theory to predict deflection components. Four-point bend tests of the same panel are conducted at pressures of 34.5, 68.9, and 103 kPa and for span-to-depth ratios of 7.2, 12.5, and 17.8 to give load–deflection response with varying levels of shear deformation. Analytical, mechanics-based expressions are derived to quantify load–deflection response due to bending and shear, including deflections caused by the drop-stitch yarns. The resulting expressions are shown to predict the measured load–deflection behavior to within 20% at the theoretical wrinkling load while indicating that the midspan deflection caused by shear deformations including the effect of the drop-stitch yarns are 78% of the total panel deflection for the lowest inflation pressure and smallest span-to-depth ratio. An approach to reducing panel shear deformability through the incorporation of braided sidewalls is proposed, and a second panel with this modification is fabricated and tested in four-point bending to experimentally demonstrate effectiveness. For the smallest span-to-depth ratio, shear stiffening reduced panel midspan deflection by 17–22% depending on inflation pressure.

Fibers doi: 10.3390/fib14020022

Authors: Chloe M. Taylor Lucian A. Lucia

Stimuli-responsive textiles are a rapidly evolving class of functional fiber-based materials that sense and adapt to environmental triggers. Within these enabling technologies, hydrogels and microcapsules are very illustrative, as they offer complementary mechanisms for moisture management, controlled release, and adaptive performance. Hydrogels provide soft, water-rich polymer networks with modifiable swelling, permeability, and mechanics, while microcapsules offer protection and targeted delivery of active agents through engineered shell structures. When integrated into fibrous networks, they impart dynamic detection responses for moisture, temperature, pH, mechanical stress, light, and chemical or biological agents. This review critically examines progress in design, synthesis, and textile integration of hydrogel- and microcapsule-based systems, with emphasis on materials that exhibit stimuli-responsive behavior rather than passive or extended-release functionality. Strategies for incorporating bulk hydrogels, micro- and nanogels, and stimuli-responsive microcapsules into fibers, yarns, and fabrics are discussed in addition to applications such as smart apparel, medical and hygienic textiles, controlled drug delivery, antimicrobial fabrics, and adaptive filtration media. Existing challenges for durability, washability, response kinetics, scalability, and sustainability are highlighted, while future research directions are proposed to advance the development of robust and intelligent textile systems at the nexus of soft matter science and fiber engineering.

Fibers doi: 10.3390/fib14020021

Authors: Juro Živičnjak Antoneta Tomljenović Igor Zjakić

During use, the surface of textile fabrics is prone to wear, which can cause changes such as pilling. Pilling (entanglement of fibers) is primarily assessed using the standard visual method EN ISO 12945-4:2020, but it can also be quantitatively measured by instrumental methods with image analysis software. Due to non-uniform digital imaging conditions, such as variations in magnification and analyzed surface area, the assessed area is often inconsistent. As a result, the total percentage of the fabric specimen surface area covered with pills is often omitted. To ensure uniform digital imaging, an innovative apparatus was designed and constructed in this research and applied to woven fabrics made from 100% cotton, wool, viscose, polyamide 6.6, polyester, and acrylic fiber. Pilling in the fabric specimens was induced by rubbing with the Martindale pilling tester (EN ISO 12945-2:2020) using two different abradant materials, through predefined pilling rubs ranging from 125 to 30,000. Pilling assessment was conducted using both the visual method and the improved instrumental method, following established grading classes based on the total percentage of the fabric specimen surface area covered with pills. The research results highlight the importance of uniform digital imaging and digital grading, as these demonstrate the high comparability of pilling grades assigned by the standard visual method while providing better distinction between consecutive grades.

Fibers doi: 10.3390/fib14020020

Authors: Paula Vigón Antonio Argüelles Miguel Lozano Jaime Viña

One of the most critical damage modes affecting the structural performance of traditional composite materials, and therefore their durability, is the occurrence of interlaminar cracks (delamination), which are prone to grow under different loading conditions. In this study, the feasibility of repairing carbon fiber reinforced polymer (CFRP) laminates using structural adhesives was experimentally investigated by evaluating the Mode I interlaminar fracture toughness. Two unidirectional AS4 CFRP systems were analyzed, manufactured with epoxy 8552 and epoxy 3501-6 matrix resins. Mode I delamination behavior was characterized using Double Cantilever Beam (DCB) specimens. Three commercial structural adhesives were used in the repair process: two epoxy-based systems, (Loctite® EA 9460™, manufactured by Henkel adhesives (Düsseldorf, Germany), and Araldite® 2015 manufactured by Huntsman Advanced Materials (The Woodlands, TX, USA) and one low-odor acrylic adhesive, 3M Scotch-Weld® DP8810NS manufactured by 3M Company (St. Paul, MN, USA). Adhesive joints were applied to previously fractured specimens, and the results were compared with those obtained from baseline composite specimens. The results indicate that repaired joints based on the 8552 matrix exhibited higher strain energy release rate (GIc) values, approaching those of the original material. The 3501-6 system showed increased fiber bridging, contributing to higher apparent fracture toughness. Among the adhesives evaluated, the acrylic-based adhesive provided the highest delamination resistance for both composite systems.

Fibers doi: 10.3390/fib14020019

Authors: Chao Du Yali Zhao Yong Li

In this study, the process of preparing ABS-ZnO (Acrylonitrile Butadiene Styrene-Zinc Oxide) composite materials as FDM printing materials was elaborated, and the influence of printing process parameters on the tensile properties and surface roughness of the materials was analyzed. It was concluded through orthogonal experiments that among all the parameters studied, the infill rate had the most significant effect on the tensile strength, followed by layer thickness and layer width, while the printing speed had the least effect. When the printing parameters were set as follows: infill rate (90%), layer thickness (0.2 mm), layer width (0.4 mm), and printing speed (200 mm/s), the tensile strength of the sample reached the maximum value of 48.37 MPa. Scanning electron microscopy (SEM) analysis revealed that a high infill rate could make the internal structure of the material denser and the bonding between fibers more sufficient. In contrast, with the increase in layer thickness and layer width, the internal structure of the material exhibited a porous morphology, which led to a decrease in tensile properties. By investigating the effects of printing temperature and layer thickness on the surface roughness of the samples, the optimal surface roughness was achieved when the printing temperature was set at 230 °C, and the layer thickness was 0.3 mm.

Fibers doi: 10.3390/fib14020018

Authors: Mohammad A. Abdul Qader Shannon Hughes Dryver Huston Mandar M. Dewoolkar

This study evaluates the mechanical properties and durability of novel self-shrinking chitosan fibers incorporated into a High-Performance Concrete (HPC) matrix. The cementitious system comprised a 75–25% blend of Portland Limestone Cement (PLC) and Ground Glass Pozzolan (GGP). Two variants of chitosan—food-grade and high-grade—were processed into fibers and integrated at dosages of 0.36%, 0.73%, and 1.45% by weight of binder, alongside a 0% control group. The experimental program assessed eight distinct mixtures through extended freeze–thaw testing (up to 602 cycles), electrical resistance monitoring, and compressive strength evaluation at 56 and 90 days. Results indicated that food-grade chitosan fibers caused a substantial reduction in compressive strength, ranging from 40% to 70% depending on the dosage. Despite this mechanical loss, these mixtures showed localized improvements in freeze–thaw resistance and electrical resistivity. Conversely, the high-grade chitosan fibers exhibited severe performance degradation under freeze–thaw cycling; all reinforced groups fell below 80% relative dynamic modulus, with two mixtures dropping below the 60% failure threshold. In comparison, the control mixture retained 98% of its dynamic modulus after 602 cycles. Ultimately, the findings suggest that, in their current formulation, self-shrinking chitosan fibers do not provide consistent or reliable enhancements to the structural integrity or durability of high-performance concrete.

Fibers doi: 10.3390/fib14020017

Authors: Duman Dyussembinov Zhanbolat Shakhmov Rauan Lukpanov Assel Jexembayeva Adiya Zhumagulova

The article examines the waste management challenges associated with basalt fiber-based mineral insulation materials generated during the production of thermal insulation products. In response to the environmental and economic issues linked to their disposal, a chemical processing approach is proposed to convert this waste into a mineral powder suitable for construction applications, particularly as an additive in asphalt concrete. A detailed technological scheme of the chemical treatment process is presented, and the optimal proportions of waste, water, and electrolyte (sulfuric acid), along with the corresponding processing conditions, are identified. The chemical and mineralogical composition of the raw materials and the resulting powder are investigated, and laboratory tests are carried out confirming its suitability as an active mineral additive. The chemical and mineralogical characteristics of the raw waste and resulting product are analyzed using XRD, SEM-EDS, and standard physical tests. In addition, the proposed technology provides a notable reduction in waste volume, thereby decreasing the load on landfills and contributing to more sustainable resource utilization.

Fibers doi: 10.3390/fib14020016

Authors: Dong-Kyu Kim Woong Han Young Chul Choi Kwan-Woo Kim Byung-Joo Kim

The wettability of a carbon fiber surface is an important factor that determines the strength of its bonding with matrices, and hence, an optimized criterion is required to accurately measure the wettability. In this study, the Washburn capillary rise method was used to select the capillary constant with the minimal deviation among various carbon fiber lengths, and it was applied to determine the contact angle and surface free energy of each carbon fiber length according to the wetting liquid. The smallest deviation in the contact angle was observed for a carbon fiber length of 2 inches, and this observation was attributed to the pores in the fibers and the orientation of the carbon fibers packed inside the column. By reducing the number of pores and achieving favorable packing, the surface free energy of carbon fibers can be measured with a high degree of accuracy, contributing to an improved understanding of fiber–matrix interactions.

Fibers doi: 10.3390/fib14010015

Authors: Faisal Abedin Emiel DenHartog

The interaction between moisture and textile materials plays a critical role in transient thermal comfort, particularly through the exothermic heat released during wetting. While the heat of wetting has been extensively characterized at the fiber level, its behavior in finished fabrics, where structure, porosity, and air gaps influence moisture uptake, remains poorly understood. This study quantifies the heat of wetting of clothing fabrics using a TAM Air isothermal microcalorimeter under controlled isothermal conditions (23 °C). Five fabric types representing different fiber chemistries (Merino wool, cotton, viscose, and polyester) were evaluated in both folded and dissected forms to assess the influence of sampling methods. Wool fabrics exhibited the highest heat release, followed by viscose and cotton, whereas polyester showed negligible exothermic response due to its non-hygroscopic nature. Overall, fabric-level heat of wetting values were lower and more variable than the corresponding fiber-level values reported in the literature, reflecting the combined effects of fabric structure, air permeability, surface hydrophilicity, and sampling uniformity. These findings demonstrate the feasibility and limitations of isothermal microcalorimetry for characterizing moisture–fabric interactions and highlight the need for improved sampling and measurement protocols to more accurately capture fabric-level sorption heat relevant to clothing comfort.

Fibers doi: 10.3390/fib14010014

Authors: Luigi Madeo Anastasia Macario Federica Napoli Pierantonio De Luca

Licorice (Glycyrrhiza glabra) is a perennial herb traditionally valued for its aromatic and therapeutic properties. In recent years, however, growing attention has shifted toward the technical and environmental potential of the plant’s industrial by-products, particularly the fibrous material left after extraction. This review integrates botanical knowledge with engineering and industrial perspectives, highlighting the role of licorice fiber in advancing sustainable innovation. The natural fiber obtained from licorice roots exhibits notable physical and mechanical qualities, including lightness, biodegradability, and compatibility with bio-based polymer matrices. These attributes make it a promising candidate for biocomposites used in green building and other sectors of the circular economy. Developing efficient recovery processes requires collaboration across disciplines, combining expertise in plant science, materials engineering, and industrial technology. The article also examines the economic and regulatory context driving the transition toward more circular and traceable production models. Increasing interest from companies, research institutions, and public bodies in valorizing licorice fiber and its derivatives is opening new market opportunities. Potential applications extend to agroindustry, eco-friendly cosmetics, bioeconomy, and sustainable construction. By linking botanical insights with innovative waste management strategies, licorice emerges as a resource capable of supporting integrated, competitive, and environmentally responsible industrial practices.

Fibers doi: 10.3390/fib14010013

Authors: Jack Andrew Cottrell Muhammad Ali D. Brett Martinson D. Lavorato

This study investigates the behaviour of Compressed Earth Cylinders (CECs) and Compressed Earth Blocks (CEBs) during direct compression tests and examines the influence of aspect ratio and the effects of platen restraint. The experimental investigation utilises two soil types and examines the impact of jute fibre reinforcement on the failure mechanism of CECs with aspect ratios ranging from 0.50 to 2.00. Through experimental analysis and numerical modelling, the effects of platen restraint are examined, and a novel hypothesis of intersecting cones is presented. The results show that specimens with a lower aspect ratio exhibited higher compressive strength due to confinement caused by platen restraint. Moreover, this research has derived new aspect ratio correction factors that enable conversion from Apparent Compressive Strength (ACS) to Unconfined Compressive Strength (UCS) of unstabilised and fibre-reinforced CECs. The experimental results indicate that the derived conversion factor of 0.861 allows for the prediction of CEB strength from CEC specimens with an accuracy of 2.7%. Furthermore, the addition of jute fibres at a 0.25% dosage increased the Apparent Compressive Strength across all aspect ratios. The outcome of this research recommends a standard approach to the application of aspect ratio correction factors when interpreting and reporting the compressive strength of CECs and CEBs.

Fibers doi: 10.3390/fib14010012

Authors: Loukia Plakia Adamantia Zourou Maria Zografaki Evangelia Vouvoudi Dimitrios Gavril Konstantinos V. Kordatos Nikos G. Tsierkezos Ioannis Kartsonakis

Hydrogen, as an alternative energy carrier, presents significant prospects for the transition to more environmentally friendly energy solutions. However, its efficient and safe storage remains a challenge, as materials with high adsorbent capacity and long-term storage capability are required. This study focuses on the synthesis and characterization of a composite material comprising carbon fiber and manganese dioxide (MnO2/CFs), for the purpose of hydrogen storage. Carbon fiber was chosen as the basis for the composition of the composite material due to its large active surface area and its excellent mechanical, thermal, and electrochemical properties. The deposition of MnO2 on the surface of carbon fibers took place through two different synthetic pathways: electrochemical deposition and chemical synthesis under different conditions. The electrochemical method enabled the production of a greater amount of oxide with optimized structural and chemical properties, whereas the chemical method was simpler but required more time to achieve comparable or lower-capacity performance. Elemental analysis of the electrochemically produced composites showcased an average of 40.5 ± 0.05 wt% Mn presence, which is an indicator of the quantity of MnO2 on the surface responsible for hydrogen storage, while the chemically produced composites showcased an average of 7.6 ± 0.05 wt% Mn presence. Manganese oxide’s high specific capacity and reversible redox reaction participation make it suitable for hydrogen storage applications. The obtained results of the hydrogenated samples through physicochemical characterization indicated the formation of the MnOOH intermediate. Regarding these findings it may be remarked that carbon fiber/MnO2 composites are promising candidates for hydrogen storage technologies. Finally, the fabricated carbon fiber/MnO2 composites were applied successfully as working electrodes for analysis of the [Fe(CN)6]3−/4− redox system in aqueous KCl solutions.

Fibers doi: 10.3390/fib14010011

Authors: Valeria Indelicato Roberto Visalli Maria Rita Pinizzotto Carmelo Cantaro Rosolino Cirrincione Alberto Pistorio Claudia Ricchiuti Rosalda Punturo

The present review paper focuses on the peculiar environmental and health implications of fibrous amphibole “fluoro-edenite”, a new mineral first reported in Biancavilla (Etna Mount, Sicily, Italy). Its presence has been linked to an unusually high incidence of malignant pleural mesothelioma, as seen from national surveys during 1988–1997, marking the first case study of natural occurrence of fibrous amphibole in a volcanic context. Despite remediation efforts since the cessation of quarrying activities at the “Il Calvario” quarry, the risk of fiber exposure may extend beyond urban areas to surrounding soils and volcanic formation, not fully characterized yet. This review synthesizes relevant existing literature on mineralogical and chemical features of fluoro-edenite, while also enriching current understanding with new observations from optical microscopy, stereomicroscopy, and Scanning Electron Microscopy (SEM). Our analyses reveal the presence of fluoro-edenite amphibole not only in the altered samples but, significantly, within the massive rock samples. This finding expands its known distribution and offers initial consideration on public health implications related to massive lava rock, which crops out. This study highlights the importance of ongoing monitoring, detailed geological surveys, and further research into fiber occurrences and distribution in the volcanic systems, of which Mt. Etna represents the first case of natural occurrences, in order to fully assess their impact on public health.

Fibers doi: 10.3390/fib14010010

Authors: Augustina Sandina Tronac Simona Marcu Spinu Mihaela Dragoi Cudalbeanu Carmen Laura Cimpeanu Alina Ortan

Human health is profoundly influenced by external factors, with stress being a primary contributor. In this context, the digestive system is particularly susceptible. The prevalence of diseases affecting the small intestine and colon is increasing. Consequently, insoluble plant fibers, such as cellulose and hemicellulose, play a crucial role in promoting intestinal transit and maintaining colon health. Lettuce is a widely consumed leafy vegetable with high nutritional value and has been intensively studied through hydroponic cultivation. This study aims to optimize the cultivation conditions and freeze-drying process of Lugano and Carmesi lettuce varieties (Lactuca sativa L.) by identifying the optimal growth conditions, freeze-drying duration, and sample surface area in order to achieve an optimal percentage of insoluble fibers. Carmesi and Lugano varieties were selected based on their contrasting growth characteristics and leaf morphology, allowing to assess whether treatments and processing conditions have consistent effects on different types of lettuce. The optimal freeze-drying parameters were determined to include a 48 h freeze-drying period, a maximum sample surface area of 144 cm2, and growth under combined conditions of supplementary oxygenation and LED light exposure. The optimal fiber composition, cellulose (21.61%), hemicellulose (11.84%) and lignin (1.36%), was found for the Lugano variety, which exhibited lower lignin and higher cellulose contents than the Carmesi variety. The quantification of hemicellulose, cellulose and lignin was performed using the well-known NDF, ADF and ADL methods. Therefore, optimized freeze-dried lettuce powder, particularly from the Lugano variety, presents a high-value functional ingredient for enriching foods and developing nutritional supplements aimed at digestive health.

Fibers doi: 10.3390/fib14010009

Authors: Nikita A. Shutskiy Aleksandr R. Shevchenko Ksenia A. Mayorova Leonid L. Shagrov Andrey S. Aksenov

A promising application of smart materials based on natural polymers is the potential to solve problems related to hemostasis in cases of severe bleeding caused by injury or surgery. This can be a life-threatening situation. Cellulose and its modified derivatives represent one of the most promising sources for creating effective hemostatic systems, as well as for various sensing applications related to disease detection, infection diagnosis, chronic condition monitoring, and blood analysis. The aim of this review was to identify key criteria for the efficiency of cellulose-based gels with hemostatic activity. Experimental studies aimed at evaluating new hemostatic devices were analyzed based on international sources using the PRISMA methodology. A total of 111 publications were identified. Following the identification and screening stages, 20 articles were selected for the final qualitative synthesis. The analyzed publications include experimental studies focused on the development and analysis of highly porous cellulose-based scaffolds in the form of aerogels and cryogels. The type and origin of cellulose, as well as the influence of additional components and synthesis conditions on gel formation, were investigated. Three major groups of key criteria that should be considered when developing new cellulose-based highly porous scaffolds with hemostatic functionality were identified: (I) physicochemical and mechanical properties (pore size distribution, compressive strength, and presence of functional groups); (II) in vitro tests (blood clotting index, red blood cell adhesion rate, hemolysis, cytocompatibility, and antibacterial activity); (III) in vivo hemostatic efficiency (hemostasis time and blood loss) in compliance with the 3Rs policy (replacement, reduction, refinement). The prospects for the development of highly porous cellulose-based scaffolds are not only focused on their hemostatic properties, but also on the development of smart platforms.

Fibers doi: 10.3390/fib14010008

Authors: Razvan Udroiu Paul Bere Katarzyna Biruk-Urban Jerzy Józwik

High-quality drilled holes are critical in thin fabric-reinforced composites used in many industrial applications; however, the influence of woven architecture on drilling performance without a backup plate remains insufficiently defined. This paper introduces the first comprehensive experimental and statistical framework for evaluating unsupported drilling of thin woven glass fiber-reinforced polymer (GFRP) laminates. The framework integrates the effect of support opening width, fiber weight fraction (wf), feed per tooth, and fabric architecture to quantify their combined effects on delamination, cutting forces, and surface roughness. The samples consisted of vacuum mold-pressed GFRP laminates. Drilling tests were conducted on plain and twill-woven plates, and hole quality was evaluated using thrust force, delamination factor, and surface roughness (Sa). A statistical DOE and multifactorial ANOVA were applied to quantify the effects of the main parameters. For plain-woven GFRP, the best results were obtained with a 65 mm support opening width, 45% fiber wf, and 0.04 mm/tooth feed. Plain-woven laminates exhibited lower average surface roughness (Sa ≈ 5.0–6.5 µm) than twill-woven laminates (Sa ≈ 6.0–7.0 µm). The study demonstrates how fabric architecture and drilling parameters jointly influence hole quality in thin GFRP composites, providing practical guidance for manufacturing applications.

Fibers doi: 10.3390/fib14010007

Authors: Hazman Azhari Abdul Rasid Hamid Yusoff Koay Mei Hyie Fatin Hazwani Aiman Izmin Boey Tze Zhou Farrahnoor Ahmad

Empty fruit bunches (EFBs) and kenaf are two abundant sources of lignocellulosic resource agricultural waste with potential as substrates for mycelium-based composites (MBCs). These composites are lightweight, compostable, low-cost, and suitable for packaging applications. However, their performance is highly dependent on the type of lignocellulosic substrate and the processing conditions applied during production. Despite the promising availability of natural fibers, limited research has focused on the drying process that affects the quality of MBCs. This study investigates the effect of different drying times (12, 18, and 24 h) on the physical and mechanical properties of MBCS produced from EFB and kenaf substrates. Following a 20-day incubation period under controlled conditions, the composites were oven-dried and analyzed for mycelial colonization, density measurement, shrinkage, water loss, shore A hardness, impact resistance, and mold growth. The results demonstrated that a drying time of 24 h yielded the best overall performance. Moisture loss (67.00%) and shrinkage (50.70%) increased with longer drying times (24 h), particularly in kenaf-based composites. Extended drying minimized mold contamination and enhanced the structural integrity of the composites. Overall, EFB-based composites achieved the highest Shore A hardness (44.53 HA). These findings show that optimizing the drying time enhances the durability of MBCs, reinforcing their potential as sustainable, biodegradable alternatives to polystyrene and promoting the development of eco-friendly materials.

Fibers doi: 10.3390/fib14010006

Authors: Tommaso Pini Gianluca Ciarleglio Elisa Toto Maria Gabriella Santonicola Marco Valente

Electrospinning of poly(lactic acid) (PLA) commonly relies on toxic organic solvents, which limit its sustainability and biomedical applicability. In this work, a green electrospinning process was developed using dimethyl carbonate (DMC), a biodegradable and low-toxicity solvent, combined with acetone as a volatile co-solvent to promote efficient jet solidification. Three commercial PLA grades were evaluated for solubility and spinnability, and PLA 4043D was identified as the most suitable for DMC and acetone systems. The electrospinning parameters, including solvent ratio, flow rate, and applied voltage, were systematically optimized to achieve stable jet formation and uniform fiber morphology. Under optimized conditions, the process produced continuous, bead-free nanofibers with a mean diameter of ~1 µm and uniform nanoscale surface porosity resulting from differential solvent evaporation. The resulting fibers were characterized in terms of morphology, structure, thermal behavior, and mechanical performance, confirming increased amorphous content, high porosity (about 78%), and tensile strength of ~3 MPa for the selected electrospinning condition. This study demonstrates that DMC-based solvent systems enable a sustainable and potentially biocompatible route, considering the lower toxicity of the solvents employed, offering a green alternative to conventional toxic processes for the fabrication of medical scaffolds.

Fibers doi: 10.3390/fib14010005

Authors: Houzhen Liu Wenzheng Jiang Shaokai Hu Guodong Zhang Weizhuang Yang Shengzong Ci Tianrun Yang Kun Qiao

The extensive application of carbon fibers (CFs) and their composites in aerospace and electronics has established the optimization of their electrical conductivity as a critical research priority. Conventional electrodeposition techniques are limited by CF inherent chemical inertness and low surface energy, which increase the energy barrier for copper deposition, leading to defective coatings and weakened interfacial bonding. This study demonstrated that sodium hypophosphite (NaH2PO2) enhances CF copper deposition efficiency through concentration gradient experiments (0–30 g/L), revealing its modulation of deposition kinetics, crystallographic evolution, and interfacial adhesion strength. Electrochemical analysis showed that NaH2PO2 accelerates initial copper nucleation by reducing activation energy without forming complexes. Increasing its concentration expanded monofilament diameter from 8.55 to 9.26 μm post-deposition, with copper loading rising 28.89%. XRD analysis identified 20 g/L as the optimum for crystallinity, producing maximal grain size (8.27 nm) and predominant (111) orientation. This structure achieved a conductivity of 1.63 × 103 S·cm−1 (55.24% enhancement) and improved breaking force from 13.54 to 14.57 cN. Adhesion tests showed that the 20 g/L group maintained stability comparable to the control. These results suggest that 20 g/L is the preferred concentration balancing conductivity enhancement with mechanical stability. This approach offers a novel strategy for fabricating highly conductive CF composites.

Fibers doi: 10.3390/fib14010004

Authors: Emmanouil Golias Chris Karayannis

In the original publication [...]

Fibers doi: 10.3390/fib14010003

Authors: Le Quang Trung Yuki Takahashi Motoki Haruta Shinji Okazaki Naoya Kasai

This study presents the experimental optimization of an interferometric optical fiber sensor for acoustic emission (AE) detection. The system employs a simple and low-cost structure composed of sensing and reference fibers, enabling interference-based detection without specialized components such as fiber Bragg gratings or Fabry–Perot cavities. A narrowband laser source was selected through comparative experiments for its superior stability and interference performance. The influence of fiber-loop parameters, including the number of turns and the optical-path intensity ratio, was systematically evaluated to clarify their effects on AE sensitivity and frequency response. The experimental results demonstrate that detection performance and bandwidth can be flexibly tuned by optimizing the loop configuration. Finally, the sensor was validated using a tensile test, successfully detecting AE signals in the range of 20 kHz to 1 MHz. The proposed system provides a robust, EMI-resistant, and cost-effective interferometric solution for AE monitoring.

Fibers doi: 10.3390/fib14010002

Authors: Adèle Hue Coralie Buffet Lèna Brionne Johnny Beaugrand Pierre D’Arras Alain Bourmaud Christophe Baley

Along the French-English Channel coast, fibre flax is traditionally cultivated in spring during a short window from March to July. However, increasingly frequent and severe spring droughts, driven by climate change, cast doubt on the sustainability of this practice. One possible adaptation, inspired by the winter cultivation of oilseed flax and tested over several years, involves extending the growing cycle by cultivating fibre flax in winter. In this system, seeds are sown in autumn, and the crop is harvested in early June. After four consecutive years of monitoring yield and fibre mechanical properties, a selected spring flax variety was grown both in winter 2022/2023 and in spring 2023 for direct comparison. This period included a mild winter favourable for winter crops, and a spring drought that severely impacted spring crops. Plants from the winter crop produced twice as many fibres at mid-stem height as the spring crop, but the mechanical properties of the elementary fibres remained similar in both. However, the elementary fibres in the lower stems of the winter crop averaged only 15 mm in length, compared to 33 mm for the spring crop, which benefited from higher temperatures. Regarding biochemical composition, lignin content in winter flax scutched fibres was significantly higher than in spring flax, at 4.2% versus 2.7%. Cultivating a spring flax variety in winter is thus feasible under favourable conditions, but the resulting fibres are shorter and more lignified, which may pose technical challenges during spinning and could require separating fibres from the lower stems of winter plants to ensure consistent fibre quality. In the final section of the paper, strategies to adapt flax cultivation to climate change are proposed, drawing on the experimental results and current meteorological projections, providing guidance for optimizing crop performance.

Fibers doi: 10.3390/fib14010001

Authors: Qunyi Huang Qingyu Huang Hong Yang Jiahang Zhang Yajie Wu

This paper investigates the fundamental workability of 3D printed concrete materials incorporating different fiber types. Fluidity, extrudability, and buildability were proposed as key indicators for assessing printability, evaluated through corresponding test methods, including fluidity tests, filament extrusion tests, and slump tests. The results demonstrate that the optimal ranges for printability are superplasticizer content between 0.35% and 0.45%, accelerator content between 0.60% and 0.85%, and silica fume replacement level between 7.5% and 10%. The incorporation of copper-coated steel fibers led to deteriorated workability, manifested as reduced fluidity, increased fluidity loss over time, poor pumpability, discontinuous extrusion, and low slump, although buildability remained satisfactory. Polypropylene fibers increased the air content in concrete, thereby improving workability; they exhibited good extrusion continuity, appropriate slump and filament width, and favorable buildability. Basalt fibers significantly enhanced air content and workability. However, due to the high stiffness of the fibers, extrusion continuity was only moderate. While the slump and filament width were suitable, the presence of minor voids in the printed filaments resulted in average buildability.

Fibers doi: 10.3390/fib13120167

Authors: João Marques Madalena Barata Garcia Virgínia Infante Pedro Miguel Amaral Arménio Correia

The building sector faces sustainability issues due to its substantial resource demand, prompting the exploration of alternative materials of natural origin. Given the diverse environmental conditions buildings experience, assessing the impact of these conditions on the mechanical characteristics of alternative materials becomes crucial. This study focuses on a composite comprising stone, agglomerate cork core and glass fiber-reinforced epoxy skins, designed for ventilated facades. The composite underwent an aging cycle commonly applied in the evaluation of construction building materials to evaluate its flexural behavior. To that end, bending tests on unaged and aged samples were carried out to investigate both the bending strength and stiffness. The composite panels were tested in two configurations: (i) stone facing up and (ii) stone facing down. The results indicated that higher bending strength was found in samples where the stone was facing up, regardless of the aging condition. In the stone facing up configuration, the predominant failure mode was stone crushing, whereas the samples in the stone facing down configuration evidenced a failure mechanism of fiber breakage. Despite the observed morphological differences between aged and unaged specimens, no significant difference was found regarding the bending strength and failure modes in both tested configurations. However, a flexural stiffness reduction of at least 21% was found for every aged specimen.

Fibers doi: 10.3390/fib13120166

Authors: Amanda J. Thompson

Demand for clothing is estimated to increase globally by 4.5% per year, and secondhand clothing is often used to fill that demand. A clear understanding of the environmental impact of secondhand items would support transparency around sustainability, which is a rising consumer concern. This study focuses on the characteristics of the fiber fragment material released during the laundering of secondhand, 100% cotton denim clothing, and the implications of secondhand clothing’s contribution of fiber fragments to the environment. The test method used was AATCC TM212-2021, with detergent, conditioned specimens, and filters. The specimens included thirteen pairs of secondhand men’s 100% cotton jeans (SHS) and two pairs of new jeans (CN controls). This study concluded that the amount of fiber fragmentation material shed by SHS was 23.2% of that shed by CN. While this is less than is shed by new clothing, there is still shed material to consider, including dyes and processing chemicals that can contribute to anthropogenic contamination of the environment. The fiber fragment size and frequency were found to have statistically significant differences between SHS (length 370.5 µm, diameter 16.9 µm, 3093 fiber fragments per filter) and CN (320.7 µm, 13.8 µm, and 5962 fiber fragments per filter).

Fibers doi: 10.3390/fib13120165

Authors: Katarina Didulica Ana Baričević Vesna Zalar Serjun

The incorporation of recycled tyre polymer fibres (RTPF) in cementitious composites provides an effective and sustainable approach in tyre waste management while offering potential benefits in mitigating early-age volume deformations. This study evaluates the influence of RTPFs, used in dry (RTPFd) and pre-wetted (RTPFw) states, on key hydration processes governing autogenous shrinkage in cement pastes with w/c of 0.4 and 0.22. The results show that RTPF reduced workability and altered the setting process due to the fibre–matrix mechanical interactions. Incorporation of RTPFs induced changes in water distribution at the fibre surface, delaying self-desiccation and maintaining higher internal relative humidity. While RTPFs offer a beneficial reduction in autogenous shrinkage by 12–41% in mixtures with w/c of 0.4 and by 15–34% in mixtures with w/c of 0.22, RTPFs also increased porosity, which contributed to a reduction in 28-day compressive strength of up to 16%. These findings highlight the dual effect of RTPF on early-age performance and provide insight into their potential application in sustainable cementitious composites.

Fibers doi: 10.3390/fib13120164

Authors: Ramdane Sidali Amrouche Samira Djaknoun Messaoud Saidani Zineb Abeoub Giangiacomo Minak

Despite increased utilization of high-performance mortars in construction, there remains a paucity of research concerning the bond performance of steel reinforcement, particularly within masonry structures. This study characterizes the bond stress behavior in high-performance steel fiber mortar (HPSFRM) to define critical design bond stress parameters. Pull-out tests were performed, incorporating three primary variables: compressive resistance, steel fiber volume, and steel rebars diameter. To support safe and reliable bond design in HPSFRM precast members, various methods for analyzing bond strength, alongside empirical predictive equations, were evaluated. The results revealed that although the rate of increase in bond strength was impacted by the incorporation of steel fibers, the bond strength demonstrated significant improvement in the mortar compressive strength. Introducing steel fibers at a volumetric content of 1% doubled the bond strength. The optimum fiber content was found at 1%, where bond strength increased by 6% and slip by 102% due to effective fiber bridging. Increasing the dosage to 2% yielded only a marginal 2–5% gain, hindered by clustering and poor dispersion. Variations in steel bar diameter had a more pronounced effect on bond stress behavior. The proposed model addresses the underestimation of bond strength and ductility by existing empirical models and code provisions.

Fibers doi: 10.3390/fib13120163

Authors: Maria Modestou Dionisis Semitekolos Tao Liu Christina Podara Savvas Orfanidis Ana Teresa Lima Costas Charitidis

Wind turbine blades (WTBs) have always been considered one of the greatest engineering achievements. They primarily use glass fiber-reinforced polymers (GFRPs) because of their lightweight nature, impressive strength-to-weight ratio, and durability. Until now, typical disposal methods of End-of-Life (EoL) WTBs are landfill or incineration. However, such practices are neither environmentally sustainable nor compliant with current regulations. This study investigates a low-temperature solvolysis process using a poly(ethylene glycol)/NaOH system under ambient pressure for efficient decomposition of the polyester matrix, promoting the potential of chemical recycling as an alternative to landfilling and incineration by offering a viable method for recovering glass fibers from WTB waste. A parametric study evaluated the influence of reaction time (4–5.5 h) and catalyst-to-resin ratio (0.1–2.0 g NaOH per g resin) on solvolysis efficiency. Optimal conditions (200 g PEG200, 12.5 g NaOH, 10 g GFRP, 5.5 h) achieved an ~80% decomposition efficiency and fibers exhibiting minimal surface degradation. SEM and EDX analyses confirmed limited morphological damage, while excessive NaOH (>15 g) caused notable etching of the glass fibers. ICP-OES of liquid residues detected high Na (780 mg/L) and Si (139 mg/L) concentrations, verifying partial dissolution of the fiber structure under strongly alkaline conditions. After applying a commercial sizing agent (Hydrosize HP2-06), TGA confirmed ~1.2% sizing mass, and nanoindentation analysis showed the interfacial modulus and hardness of re-sized fibers improved by over 70% compared to unsized recycled fibers, approaching the performance of virgin fibers.

Fibers doi: 10.3390/fib13120162

Authors: Marta Goliszek-Chabros Omid Hosseinaei

High production costs and sustainability issues are the main factors limiting the widespread application of carbon fibers in various industrial sectors. Lignin, a by-product from the paper and pulping industry, due to its high carbon content of up to 60%, can be considered a potential replacement for polyacrylonitrile in carbon fiber production. The production of lignins with distinct molecular weight distributions as well as group functionalities is essential to enhance high-value applications of lignin. In this study, we present a simple, green solvent-based fractionation method for LignoBoost softwood kraft lignin to obtain a lignin fraction with tailored physicochemical properties for electrospun carbon fiber production without polymeric spinning additives. Sequential solvent extraction was used to produce two fractions with distinct molecular weights: low-molecular-weight softwood kraft lignin (LMW-SKL) and high-molecular-weight softwood kraft lignin (HMW-SKL). The lignin fractions were characterized using size exclusion chromatography (SEC) for the molar mass distribution. The thermal properties of lignins were studied using thermogravimetry (TGA) and differential scanning calorimetry (DSC). Hydroxyl group content was quantified using quantitative 31P NMR spectroscopy. We successfully demonstrated the electrospinning of a high-molecular-weight lignin fraction—obtained in high yield from the fractionation process—without the use of any additives, followed by thermal conversion to produce electrospun carbon fibers. The presented results contribute to the valorization of lignin as well as to the development of green and sustainable technologies.

Fibers doi: 10.3390/fib13120161

Authors: Magaly Granda Ezequiel Zamora-Ledezma Michael Macías Pro Joseph Guamán Alexis Debut Frank Alexis Frederico B. De Sousa Christian Narváez-Muñoz

This study presents the fabrication and performance analysis of multilayer membranes produced by electrospinning using polyacrylonitrile (PAN), chitosan (CS), and Nylon 6 (N6) for the removal of chromium (Cr) and cadmium (Cd) from water. The electrospun membranes were configured in six different multilayer structures. The morphological and mechanical properties of the membranes were evaluated using SEM and tensile testing. Adsorption experiments were performed using synthetic and real water samples from the Cutuchi River. The multilayer membranes demonstrated metal ion removal efficiencies up to 80.81% for Cr6+ and 78.98% for Cd2+ in synthetic water, and similar performance in real samples. These results validate the use of multilayer electrospun membranes as an effective, environmentally friendly method for water purification applications.

Fibers doi: 10.3390/fib13120160

Authors: Said Elkholy Mohamed Salem Ahmed Godat

Numerous experimental and numerical studies have extensively investigated the performance of reinforced deep beams made with natural coarse aggregate concrete. However, limited research has been carried out on reinforced deep beams made of concrete with coarse aggregate from recycled materials and steel fibers. The main goal of this research is to create an accurate finite element model that can mimic the behavior of deep beams using concrete with recycled coarse aggregate and different ratios of steel fibers. The suggested model represents the pre-peak, post-peak, confinement, and concrete-to-steel fiber bond behavior of steel fiber concrete, reinforcing steel, and loading plates by incorporating the proper structural components and constitutive laws. The deep beams’ nonlinear load–deformation behavior is simulated in displacement-controlled settings. In order to verify the model’s correctness, the ultimate loading capacity, load–deflection relationships, and failure mechanisms are compared between numerical predictions and experimental findings. The comparison outcomes of the performance of the beams demonstrate that the numerical model effectively predicts the behavior of deep beams constructed with recycled coarse aggregate concrete. The findings of the experiment and the numerical analysis exhibit a high degree of convergence, affirming the model’s capability to accurately simulate the performance of such beams. In light of how accurately the numerical predictions match the experimental results, an extensive parametric study is conducted to examine the impact of parameters on the performance of deep beams with different ratios of steel fibers, concrete compressive strength, type of steel fibers (short or long), and effective span-to-effective depth ratio. The effect of each parameter is examined relative to its effect on the fracture energy.

Fibers doi: 10.3390/fib13120159

Authors: Lais Alves Tabata Barreto Nordine Leklou Silvio de Barros

The search for sustainable alternatives to synthetic composites has become increasingly relevant in aerospace engineering education and student rocketry. Fiberglass is widely used for rocket fuselages due to its favorable balance of performance and cost, but it is energy-intensive, non-biodegradable, and environmentally burdensome. This study provides the first demonstration of natural fiber composites applied to student rocket fuselages, evaluating bamboo and jute as sustainable alternatives to fiberglass. Fiberglass, bamboo, and jute laminates were fabricated following the procedures of the RocketWolf team at CEFET/RJ. The fuselages were characterized by parachute ejection tests, surface roughness analysis, and flight simulations using OpenRocket software. Additional data such as laminate mass, wall thickness, fiber–resin ratio, and cost analysis were incorporated to provide a comprehensive assessment. Results revealed contrasting behaviors: untreated bamboo composites showed poor resin impregnation, brittle behavior, and lack of structural stability, confirming their unsuitability without chemical treatment. Jute composites, in contrast, achieved adequate impregnation, cylindrical geometry, and superior surface roughness (Ra = 37 µm) compared to fiberglass with paint (62 µm) or envelopes (52 µm). Both fiberglass and jute fuselages successfully passed parachute ejection tests, while simulations indicated apogees close to 1 km, fulfilling competition requirements. The jute fuselage also presented slightly improved stability margins. Economically, jute was ~492% cheaper than fiberglass in fiber-only comparison but absorbed more resin; nevertheless, real purchase prices favored jute. These findings confirm that jute composites are a technically feasible, cost-effective, and sustainable substitute for fiberglass in student rocket fuselages. Beyond technical validation, this work demonstrates the educational and environmental benefits of integrating natural fibers into academic rocketry, bridging sustainability, performance, and innovation.

Fibers doi: 10.3390/fib13120158

Authors: Ilektra Tourkantoni Konstantinos Tserpes Dimitrios Marinis Ergina Farsari Eleftherios Amanatides

The rapid expansion of carbon-fiber-reinforced polymer (CFRP) applications in aerospace, automotive, and energy sectors has intensified concerns over end-of-life waste and the absence of efficient recycling solutions. Plasma-assisted solvolysis has emerged as a promising hybrid approach, combining oxidative chemical treatment with plasma activation to accelerate matrix degradation. In this study, CFRP cylinders (6.4 cm height, 5.5 cm internal, and 6.0 cm external diameter) were processed in a closed-loop plasma solvolysis system under varied operational parameters, including plasma power, plasma gas composition, and nitric acid concentration. The mechanical performance of the recovered carbon fibers was assessed through single-fiber tensile and microbond tests, evaluating both tensile and interfacial properties. In most cases, the recycled fibers retained—or even exceeded—the tensile strength of their virgin counterparts, reaching up to 1.49 times that of the virgin fibers. Young’s modulus, though more variable, ranged from 0.48 to 1.67 times the reference value depending on treatment conditions. Elongation at break generally increased, particularly in the 24K (24,000-filaments) fiber sets, suggesting improved surface ductility. Weibull statistical analysis indicated higher consistency in 3K (3000-filaments) fiber batches compared to 24K, whereas interfacial shear strength was moderately retained across conditions. Overall, balanced plasma and acid conditions enabled efficient fiber recovery with high strength and interfacial performance, validating plasma-assisted solvolysis as a viable route for recovering high-performance fibers suitable for structural reuse, in alignment with circular economy principles.

Fibers doi: 10.3390/fib13120157

Authors: Ioannis Filippos Kyriakidis Anargiros Karelis Nikolaos Kladovasilakis Eleftheria Maria Pechlivani Konstantinos Tsongas

This review paper explores the influence of natural byproducts on polymer matrices via additive manufacturing (AM), focusing specifically on the development of eco-friendly composite materials. A broad range of lignocellulosic residues—such as sawdust, wood chips, bark, and other related byproducts—are evaluated for their potential incorporation into polymer matrices to create filaments and pastes appropriate for AM techniques. The paper initially examines the features of natural byproducts and their typical uses, then evaluates the benefits that AM presents in comparison to conventional manufacturing techniques. Special emphasis is placed on the physicochemical and mechanical properties of the developed composites, encompassing their thermal characteristics (glass transition temperature, melting point, and stability), density, and mechanical behavior under both static and dynamic loading. Furthermore, the environmental effects of these composites are thoroughly assessed through Life Cycle Assessment (LCA), highlighting their contribution to minimizing ecological footprints and promoting circular economy initiatives. Collectively, the findings indicate that the additive manufacturing of composites derived from natural byproducts represent a promising pathway toward sustainable industrial production.

Fibers doi: 10.3390/fib13110156

Authors: Trupti Amit Kinjawadekar Shantharam Patil Gopinatha Nayak

Corrosion continues to be a major challenge affecting the service life, safety and durability of steel-reinforced concrete (RC) structures. The deterioration of steel not only reduces structural capacity but also increases long-term maintenance costs. To address this limitation, glass fiber-reinforced polymer (GFRP) is being investigated as an alternative to conventional steel reinforcement, particularly in aggressive environments. This work examines the behavior of composite columns reinforced with GFRP bars with steel stirrups. Sixteen square columns of 150 × 150 × 850 mm dimensions, cast with M30 grade concrete, were reinforced using either GFRP or steel, while varying stirrup spacing and bar diameters. Experimental observations showed that GFRP reinforcement contributed about 10–12% of the ultimate capacity of the columns. A marked enhancement in load carrying capacity of GFRP-RC columns was obtained with closer stirrup spacing. The axial strength of GFRP-reinforced columns was comparable to steel-reinforced ones with the same main reinforcement ratio. Ductility increased by 12% when stirrup spacing was reduced. The difference between analytical and experimental values ranged between 12% and 15%, whereas experimental and numerical results differed by 10–12%. Based on these results, a modification factor derived from IS 456:2000 is proposed for predicting the capacity of ‘GFRP-reinforced’ columns. The outcomes clearly highlight the potential of GFRP reinforcement as a durable, sustainable and practical substitute for conventional steel reinforcement.

Fibers doi: 10.3390/fib13110155

Authors: Sodiq Babatunde Yusuf Nnaemeka Ewurum Harrison Appiah Jovale Vincent Tongco

The generation of over 150 million tons of hemp waste annually is as much of a sustainability challenge as it is an opportunity for the circular bioeconomy. This review provides a critical analysis of the recent trends in the use of industrial hemp waste as a precursor to producing sustainable bioproducts. The objective is to synthesize the current state of knowledge and to identify the various pathways for valorizing hemp waste beyond the traditional applications. The methodology involved the systematic assessment of the recent literature to identify the applications in textiles, biocomposites, packaging, and, most importantly, advanced areas such as hemp-based carbon materials for storing energy, biomedical materials, and smart biomaterials. Findings showed that hemp waste is a versatile material for creating high-value products, as it shows promise in carbon electrodes for supercapacitors as well as reinforcement for 3D-printed biocomposites. However, there are some limitations in terms of standardization and scalability. The review concludes that future progress depends on multidisciplinary research to optimize conversion and utilization processes, including the development of comprehensive life-cycle assessments and reliable supply chains.

Fibers doi: 10.3390/fib13110154

Authors: Theodoros Rousakis Vachan Vanian Martha Lappa Adamantis G. Zapris Ioannis P. Xynopoulos Maristella Voutetaki Stefanos Kellis George Sapidis Maria Naoum Nikos Papadopoulos Violetta K. Kytinou Martha Karabini Constantin E. Chalioris Athanasia K. Thomoglou Emmanouil Golias

Existing Mediterranean reinforced concrete buildings with masonry infills exhibit critical seismic vulnerabilities, yet real-time damage detection capabilities remain limited. This study validates a novel dense piezoelectric transducer (PZT) network concept for early damage detection in deficient RC structures under progressive seismic loading. A three-dimensional single-story RC frame with brick infills, representative of pre-Eurocode Mediterranean construction (non-ductile detailing, inadequate transverse reinforcement), was tested at serviceability limit states (SLSs) (Phase A) using a dynamic pushover approach with the 1978 Thessaloniki earthquake record, progressively scaled from EQ0.1g to EQ1.1g within the GREENERGY vertical forest renovation project. The specimen featured 48 PZTs using electromechanical impedance (EMI) methodology, 12 accelerometers, 8 displacement sensors, and 20 strain gauges. Progressive infill deterioration initiated at EQ0.5g while steel reinforcement remained elastic (max 2350 μstrain < 2890 μstrain yield). Maximum inter-story drift reached 11.37‰ with negligible residual drift (0.204‰). The PZT network, analyzed through Root Mean Square Deviation (RMSD), successfully detected internal cracking and infill-frame debonding before visible manifestation, validating its early warning capability. Floor acceleration amplification increased from 1.26 to 1.57, quantifying structural stiffness degradation. These SLS results provide critical baseline data enabling the Phase B implementation of sustainable vertical forest retrofitting strategies for aging Mediterranean building stock.

Fibers doi: 10.3390/fib13110153

Authors: Solange Mélanie Anafack Paul William Mejouyo Huisken Jean-Yves Drean Omar Harzallah Rodrigue Nicodème Sikame Tagne Hermann Tamaguelon Dzoujo Murugesh Babu Ebenezer Njeugna

This study deals with the physical, chemical, and thermal properties of William banana peduncle fibers in order to consider the possibility of using these new fibers in textile applications. The samples were collected in Cameroon, in the Littoral region, Njombe Penja district (agri-food industry). The fibers were extracted by three methods, including Water Retting (WR), Dew Retting (DR), and Mechanical Extraction (ME). The various resulting fibers were characterized by X-ray Diffraction (XRD), Thermogravimetric Analysis (TGA), Fourier-Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM), respectively. The FTIR analysis confirmed the lignocellulosic structure of the fibers and revealed that the three extraction methods had not affected the chemical nature of the fibers. The extraction methods also had no significant impact on density and moisture content. Scanning electron microscopy showed bands of fibers bundles on all samples. Thermogravimetric analysis (TGA) showed that the fibers extracted were thermally stable at 82 °C. X-ray diffraction (XRD) analysis showed crystallinity levels ranging from 58.24% for (WR), 54.83% for (DR), and 69.53% for (ME). The results obtained on the chemical composition show that the extracted fibers consist mainly of 71.8%, 73.6%, and 74.8% cellulose for WR, DR, and ME, respectively, making them suitable for textile applications.

Fibers doi: 10.3390/fib13110152

Authors: Vachan Vanian Theodoros Rousakis

This paper presents FRESCO (Fiber REinforced Strengthening COmposite Database), a comprehensive open-source database designed to systematically organize experimental data on infilled RC frame systems that can be strengthened with advanced composite materials, such as Fiber-Reinforced Polymers (FRP), Textile-Reinforced Mortars (TRM), and other fiber-based solutions. The database employs open source practices while providing high-quality output that is fully compatible with leading commercial software packages such as ANSYS 2022R2. It uses Python3 as the main programming language and FreeCAD v1.0 as the model generation engine, with a systematic 13-section structure that ensures complete documentation of all parameters necessary for numerical modeling and validation of analytical methods. Two types of databases are provided: in comma-separated format (.csv) for common everyday interaction and in JSON format (.json) for easy programmatic access. The database features automated 3D modeling capabilities, converting experimental data into detailed finite element models with solid RC frame geometry, reinforcement details, and infill configurations. Validation through three comprehensive examples demonstrates that numerical models generated from the database closely match experimental results, with response curves that closely match the initial stiffness, the peak loading and the post-peak stiffness degradation phase across different loading conditions. The database focuses on RC frame systems with unreinforced brick infill. Reflecting the term FRESCO, which in Greek (φρέσκο) means “fresh”, the database is designed as a dynamic, evolving resource, with future versions planned to include RC walls and full buildings.

Fibers doi: 10.3390/fib13110151

Authors: Jawed Qureshi Karthick Murugan Mahendran

This research addresses the critical gap in accurately modelling pultruded fibre-reinforced polymer (FRP) beam-to-column joints, where previous studies largely ignored progressive damage mechanisms. A novel finite element framework is developed in ABAQUS, integrating Hashin’s failure criterion with fracture energy-based damage evolution to simulate delamination and brittle failure in FRP cleats. The model is rigorously validated against full-scale experimental data, achieving close agreement in moment–rotation response, initial stiffness (within 5%), and ultimate moment capacity (variation < 10%). Quantitative results confirm that delamination at the fillet radius governs failure, while qualitative analysis reveals the sensitivity of stiffness to cleat geometry and bolt characteristics. A parametric study demonstrates that increasing cleat thickness and bolt diameter enhances stiffness up to 15%, whereas bolt–hole clearance introduces slip without significantly affecting strength. The validated FEM reduces reliance on costly physical testing and provides a robust tool for optimising FRP joint design, supporting the future development of design guidelines for pultruded FRP structures.

Fibers doi: 10.3390/fib13110150

Authors: Rafał Malinowski Danuta Matykiewicz Volodymyr Krasinskyi Urszula Gryczka Daniel Kaczor

This paper presents the investigation of the effect of electron radiation or the combined action of this radiation and triallyl isocyanurate (TAIC) on the structural, thermal, and mechanical properties of epoxy resin filled with a fraction of dust fibers (DFs) from recycled wind turbine blades. The resin containing 20 wt% of DF was irradiated with doses of 40, 80, 120, and 160 kGy. The results showed that electron radiation had only a slight effect on the properties of the studied composite, mainly on its glass transition temperature. More significant changes were observed with the combined action of radiation and TAIC. The main effect that occurred after the TAIC addition was the plasticization of the polymer matrix. With its participation, the glass transition temperature, thermal stability, and the hardness of the material and its flexural modulus were significantly reduced. The degree of change in these properties was regulated by the radiation dose. Furthermore, no significant changes in the composite structure were observed after radiation treatment, while the introduction of TAIC into the polymer matrix caused the formation of gas cells, probably due to the partial decomposition of TAIC.

Fibers doi: 10.3390/fib13110149

Authors: Kristiyan Stiliyanov-Atanasov Probal Basu

Due to their interesting physicochemical and bioactive properties, regenerated fibres (including cellulose and collagen regenerated fibres) have been considered attractive biomaterials for biomedical applications. These regenerated fibres have an altered molecular arrangement compared to the native fibres and exhibit unique properties. Despite their distinctive structural characteristics, a meagre amount of research explores their potential for the development of tissue-engineering bio-composites. This work focuses on exploring the promise of cellulose and collagen-based regenerated fibres in tissue-regeneration bio-composite development. Initially, the work investigates the similarities and dissimilarities between the collagen and cellulose structures, which are linked to their specific properties, such as crystallinity, chemical characteristics, and mechanical properties. It then delves deeper into their molecular structural reassembly and various aspects of the already reported bio-composites developed using them. Finally, their promise in the development of tissue-engineering bio-composites is explored through a meticulous comparative analysis of their advantages and challenges. It was found that efficient biodegradability is one of the key advantages of regenerated fibres, whereas difficulty in processing presents a significant disadvantage. Despite these facts, regenerated fibres can incorporate enhanced and desired properties into the bio-composite matrix, which could lead to tissue-specific bio-regenerative applications.

Fibers doi: 10.3390/fib13110148

Authors: Gianfranco Stipo Valerio Alecci Mario De Stefano Stefano Galassi Maria Cristina Salvatici Maria Luisa Satta

In the last decades, composite materials made of synthetic fibers embedded in organic or inorganic matrices have been successfully used for strengthening reinforced-concrete and masonry buildings. The scientific community is currently discussing the low sustainability of these materials and their environmental impact due to the production process, the life cycle, and the generation of potentially harmful waste. In this context, the use of natural textiles represents a promising solution, alternative to conventional synthetic fibers, aimed at designing an innovative composite material obtained from renewable resources with no energy consumption and greatly reducing the impact of building activities on the environment. In this paper, an experimental assessment of ten different natural textiles is presented in order to compare their mechanical properties for possible use in innovative, eco-friendly composite materials. Mechanical tensile tests were performed on the ten different textiles before and after an all-natural protective treatment referred to as the “hornification” process. Treatment-induced changes in the fiber morphology were also analyzed using a scanning electron microscope (SEM), which provided high-resolution images of the surface and cross-sectional area of the fibers. Considering that the current demand for sustainable building materials capable of ensuring a greener future for the construction industry is on the rise, the promising results obtained in this study could be useful to the academic community and building industry.

Fibers doi: 10.3390/fib13110147

Authors: Aigbe E. Awenlimobor Douglas E. Smith

This study presents a finite element analysis (FEA)-based numerical homogenization method for evaluating the effective thermo-mechanical properties of a large-area additively manufactured particulate-filled composite using realistic periodic representative volume elements (RVEs) generated from reconstructed X-ray µ-CT image scans of a 3D-printed bead. The numerical results of the predicted effective properties, including the elastic stiffness, coefficient of thermal expansion (CTE) and thermal conductivity, were benchmarked with the Mori–Tanaka–Benveniste analytical estimates, which were found to be comparable. Initial sensitivity analysis using a single region of interest (ROI) extracted from the bead’s volume was performed to determine a suitable RVE size. The impact of inherent micro-porosities on the resulting composite material’s behavior was also quantified in the current investigation and was shown to reduce the composite’s effective properties. Using a suitable RVE size, the effect of anisotropy due to spatial variation in the microstructure across the bead specimen on the computed composite’s effective properties was also assessed. The results show that the regions closer to the exposed surface of the print bead with highly aligned and densely packed fiber particulates have superior properties as compared to inner regions with a more randomly oriented and less densely packed fibrous microstructure.

Fibers doi: 10.3390/fib13110146

Authors: Mattia Longobucco Ignas Astrauskas Audrius Pugžlys Andrius Baltuška Ryszard Buczyński Ignác Bugár

We conducted a comprehensive experimental investigation of dual-wavelength switching of 1560 nm, 75 fs pulses (referred to as signal) driven by 1030 nm, 270 fs pulses (referred to as control) using two dual-core fibers with high refractive index contrast and different levels of asymmetry. The study explores the influence of fiber length, control pulse energy, and control-signal pulse delay on switching performance. For the fiber with higher dual-core asymmetry, we achieved an exceptional switching contrast of 41.6 dB at a 14 mm fiber length, exhibiting a homogeneous character within the spectral range of 1450–1650 nm. In contrast, the study of the weaker dual-core asymmetry fiber revealed a maximum switching contrast of 10.7 dB at a 22 mm fiber length, albeit under lower control pulse energy. These observations confirm that the switching mechanism is based on the nonlinear balancing of dual-core asymmetry, wherein the control pulse induces an enhancement of the effective refractive index in the fast fiber core, facilitating the switching of the signal pulse. This work demonstrates high switching contrasts with only a 0.4–0.6 nJ control pulse energy requirement, providing experimental confirmation of a previously reported theoretical model. For the first time, the dual-wavelength switching performance of dual-core fibers with varying levels of asymmetry is compared. The results reveal key directions for the further development of dual-core fibers in view of their potential applications.

Fibers doi: 10.3390/fib13110145

Authors: Ahmadreza Ravangard Kuthan Celebi Sergii G. Kravchenko Oleksandr G. Kravchenko

Fiber tow-gaps and overlaps formed during the Automated Fiber Placement (AFP) process pose a significant challenge by introducing non-uniform composite morphologies, often characterized by resin-rich regions and fiber waviness. These defects occur as deposited fibers sink into the gap regions during consolidation, with gap geometry determined during path planning. Such morphological inconsistencies can compromise structural reliability by initiating premature failure, particularly through localized out-of-plane waviness and resin accumulation. This study investigates the integration of high melting temperature thermoplastic veils, specifically polyetherimide (PEI), into fiber tow-gaps as a method to prevent ply sinking and reduce fiber waviness on both internal and external surfaces of the laminate. The PEI veils also serve to reinforce resin-rich regions by forming an interpenetrated network of high fracture toughness material within the brittle epoxy matrix. Tensile tests conducted on cross-ply laminates containing staggered gaps demonstrated that the inclusion of PEI veils modified the failure mode. The results suggest that the selective placement of thermoplastic veils within tow-gaps during AFP offers a viable strategy to mitigate manufacturing-induced non-uniform morphologies.

Fibers doi: 10.3390/fib13110144

Authors: Sven Räther Franz Sebastian Schwindling Akinori Tasaka Peter Rammelsberg Andreas Zenthöfer Stefan Rues

Fiber-reinforced composites (FRCs) are increasingly utilized in computer-aided design/computer-aided Manufacturing (CAD/CAM) workflows for both definitive and provisional restorations. Veneering these materials is essential not only for achieving aesthetic outcomes, but also to prevent direct exposure of oral tissues to glass fibers. This study evaluated the short- and long-term shear bond strength (SBS) between a veneering composite and FRC (Trinia, Bicon) with varying bonding interface orientations and load directions. Specimens were sectioned into discs with 1.5° or 45° tilt with respect to material’s layering planes and veneered with a composite pin (Ceramage, Shofu Inc.). SBS was tested after 24 h and 180 days of water storage, with forces applied either parallel or perpendicular to the layer orientation seen at the bonding interface. Long-term water storage significantly reduced SBS (24 h: 23.9 MPa vs. 180 d: 18.1 MPa, p < 0.001). In contrast, neither cutting direction (1.5° vs. 45°, p = 0.584) nor loading direction (parallel vs. perpendicular, p = 0.367) significantly influenced SBS. These results suggest veneering of the tested FRC material is clinically viable regardless of interface orientation or load direction. Although aging significantly reduced SBS, this was not clinically relevant, indicating that appropriate adhesive protocols may ensure durable bonding.

Fibers doi: 10.3390/fib13100143

Authors: Chuan Zhao Guoxin Jiang Junli Guo Xin Zhang Zelong Ma Chunyi Zhuang Wenbing Zhang Shuyang Yu

To evaluate the frost resistance of basalt fiber-reinforced concrete (BFRC) and predict its service life, this study conducted 225 quick freeze–thaw (F-T) cycle tests. Specifically, it systematically investigated how basalt fiber (BF) volume content (0.1%, 0.2%, 0.3%) and the incorporation method (single-doped 18 mm, mixed-doped 6 mm/12 mm/18 mm) affect concrete frost resistance. Meanwhile, a two-parameter Weibull distribution model was established to quantitatively predict the service life of BFRC. The results showed that BF significantly improved the frost resistance of concrete: the reference group without BF had a relative dynamic elastic modulus (RDEM) of less than 60% after 25 F-T cycles, while the group with 0.3% volume content of single-doped 18 mm BF still maintained structural integrity after 225 F-T cycles, with a frost resistance grade exceeding F225. Furthermore, within the scope of this study, the frost resistance effect of single-doped 18 mm BF was better than that of mixed-doped BF, and the frost resistance of concrete gradually improved with the increase in BF volume content. In high-altitude cold regions (e.g., Songpan County, Sichuan Province) with 85 annual F-T cycles, the predicted service life of BFRC with 0.3% single-doped BF reached 49 years, which was approximately 25 times that of the reference group (2 years). This study delivers a systematic comparison of the frost resistance between single-doped long and mixed-doped BF, along with a targeted life prediction model for high-altitude cold regions (85 annual F-T cycles, annual temperatures below 6 °C), which collectively offer a theoretical and technical basis for BFRC durability design in freeze–thaw environments.

Fibers doi: 10.3390/fib13100142

Authors: Veena Phunpeng Kitsana Khodcharad Wipada Boransan

To address circularity and resource recovery in modern structural applications, industry is seeking materials that are sustainable and lightweight. Although natural fiber-reinforced composites offer sustainability advantages, their mechanical properties remain inferior to those of synthetic fiber systems, limiting practical deployment. Flax fibers were selected as reinforcement due to their high specific stiffness, biodegradability, and wide availability. This study implements a three-level strategy to enhance the flexural performance of flax fiber-reinforced composites: at the process level, curing under distinct heating rates to promote a more uniform polymer network; at the material level, incorporation of a carbonaceous additive derived from fuel–oil furnace waste to strengthen interfacial adhesion; and at the structural level, adoption of a sandwich configuration with a recycled PET core to increase section bending inertia. Specimens were fabricated via vacuum-assisted resin transfer molding (VARTM) and tested using a three-point bending method. Mechanical testing shows clear improvements in flexural performance, with the sandwich architecture yielding the highest values and increasing flexural strength by up to 4.52× relative to the other conditions. For the curing series, FTIR indicates greater reaction extent, evidenced by lower intensities of the epoxide ring at 915 cm−1 and glycidyl/oxirane band near 972 cm−1, together with a more pronounced C–O–C stretching region, consistent with the higher flexural response. While SEM observations revealed interfacial debonding at 5% FCB, a hybrid mechanism with crack deflection appeared at 10%. This transition created tortuous crack paths, consistent with the higher flexural strength and modulus at 10% FCB. A distinctive feature of this work is the integration of three reinforcement strategies—controlled curing, waste-derived carbon additive, and recycled PET sandwich design. This integration not only enhances the performance of natural fiber composites but also emphasizes sustainability by valorizing recycled and waste-derived resources, thereby supporting the development of greener composite materials.

Fibers doi: 10.3390/fib13100141

Authors: Luisa F. Sierra Montes María C. Lorenzo Maria A. García Andrés G. Salvay Laura Ribba

Biodegradable composites obtained by reinforcing thermoplastic starch (TPS) with lignocellulosic fibers show great potential, but their strong sensitivity to water still limits practical applications. Among possible reinforcements, Helianthus tuberosus (topinambur) represents an underutilized agricultural residue that has been scarcely explored in this context. In this work, we demonstrate for the first time that topinambur fiber can improve the water vapor barrier properties of cassava starch films, while also providing a detailed analysis of sorption isotherms and the humidity-dependent relationship between surface roughness and contact angle, aspects rarely addressed in previous studies. SEM revealed uniform fiber dispersion and integration. Water sorption kinetics showed that fiber addition reduces both hydration and sorption time constant, indicating lower water affinity and greater water mobility. Water sorption isotherms confirmed that fiber incorporation significantly alters overall hydration and water–matrix interactions, revealing reduced effective water solubility in films. Water vapor permeability also decreased with fiber addition, mainly due to decreased water solubility, rather than changes in water diffusivity. While fiber addition enhanced surface-water repellency across all humidity levels, roughness exhibited a humidity-dependent response FTIR analysis confirmed fiber–matrix compatibility and suggested new hydrogen bonding. Overall, these findings identify topinambur fiber as a novel reinforcement for designing biodegradable films with improved humidity resistance for agroecological applications.

Fibers doi: 10.3390/fib13100140

Authors: Jiseon Kim Sangun Kim Jooyong Kim

This study presents a machine learning-based framework for classifying five embroidered stitch patterns—straight, zigzag, joining, satin, and wave—under 10% tensile strain, aiming to enhance their utility in smart textile circuits. Electrical conductivity was derived from resistance data and standardized using Z-score normalization. Conductivity sequences were first analyzed with PCA and Random Forest classifiers, then classified using a structural artificial neural network model. The model employed a structurally informed filter design, reflecting stitch-wise signal periodicity to capture time-varying electrical patterns under cyclic strain. It achieved a test accuracy of 97.33%, with F1-scores above 0.83 for all classes and perfect scores in three. Partial confusion between wave and zigzag patterns was observed due to their similar curved geometry and signal profiles. These results validate the discriminative power of conductivity-based features and demonstrate the potential of structure-aware neural networks for identifying dynamic stitched circuits in smart textiles.

Fibers doi: 10.3390/fib13100139

Authors: Jorge Albuja-Sánchez Doménica Romero Carlos Solórzano-Blacio

Highly decomposed organic soils exhibit low strength and stability, which pose challenges for geotechnical engineering. This study evaluates the effectiveness of abacá natural fibers treated with 5% NaOH to prevent biodegradation and reinforce organic silt. An experimental program was conducted to investigate the effects of fiber content (1, 1.5, and 2%) and length (5, 10, and 15 mm) on the undrained shear strength (Su), elastic modulus (E50), maximum dry density (MDD), and optimum water content (OWC). The results revealed a slight reduction in MDD and OWC, while Su increased significantly, reaching 104.13% for 1.5% fiber content and 15 mm fiber length. E50 decreased by up to 52.61%, indicating a transition toward more ductile behavior and variability due to the inherent heterogeneity of the soil. ANOVA and post hoc Tukey analyses confirmed the statistical significance of fiber content and length on Su, with optimal performance observed at 1.5% content and 15 mm length. These findings demonstrate that chemically treated abacá fibers provide effective and sustainable soil reinforcement and that chemical treatment is essential to maintain short-term durability in biologically active organic soils.

Fibers doi: 10.3390/fib13100138

Authors: Daniele Oliveira Justo dos Santos Romildo Dias Toledo Filho Paulo Roberto Lopes Lima

The use of sisal fibers to reinforce concrete and mortar enables the development of sustainable cement-based materials suitable for various construction elements. However, the high-water absorption of natural fibers can cause dimensional instability and poor fiber–matrix bonding, which reduces strength over time. Physical and chemical treatments can decrease water absorption and enhance the dimensional stability and bonding properties of fibers, but their effects on composite performance require further clarification. This study produced composites with 2%, 3%, and 4% by mass of sisal fibers subjected to different treatments, including hornification, washed alkaline treatment, and unwashed alkaline treatment. Fibers were characterized through water absorption, dimensional variation, scanning electron microscopy (SEM), X-ray diffraction, thermogravimetric analysis and direct tensile testing. Composites were evaluated by water absorption, capillarity, drying shrinkage, direct tensile and four-point bending tests to assess the influence of fiber treatment and content. Results showed that alkaline treatment significantly improved the physical and mechanical properties of sisal fibers. Consequently, composites reinforced with alkaline-treated fibers achieved superior performance compared to those reinforced with hornified fibers, with the best results observed at the highest fiber mass fraction (4%). These findings demonstrate the potential of treated sisal fibers to enhance the durability and mechanical behavior of natural fiber-reinforced cementitious composites.

Fibers doi: 10.3390/fib13100137

Authors: Aamir Mahmood Miroslava Pechočiaková Blanka Tomková Muhammad Tayyab Noman Mohammad Gheibi Kourosh Behzadian Jakub Wiener Luboš Hes

Basalt fiber-reinforced composites are increasingly utilized in sustainable construction due to their high strength, environmental benefits, and durability. However, the long-term tensile performance of these composites in alkaline environments remains a critical concern. This study investigates the degradation performance of basalt fibers exposed to different alkaline solutions (NaOH, KOH, and Ca(OH)2) with varying concentrations (5 g/L, 15 g/L, and 30 g/L) over various exposure periods (7, 14, and 28 days). The performance assessment is carried out by mechanical properties, including tensile strength and modulus of elasticity, using experimental techniques and Response Surface Methodology (RSM) to find influential factors on tensile performance. The findings indicate that tensile strength degradation is highly dependent on alkali type and concentration, with Ca(OH)2-treated fibers exhibiting superior mechanical retention (max tensile strength: 938.94 MPa) compared to NaOH-treated samples, which showed the highest degradation rate. Five machine learning (ML) models, including Tree Random Forest (TRF), Function Multilayer Perceptron (FMP), Lazy IBK, Meta Bagging, and Function SMOreg (FSMOreg), were also implemented to predict tensile strength based on exposure parameters. FSMOreg demonstrated the highest prediction accuracy with a correlation coefficient of 0.928 and the lowest error metrics (RMSE 181.94). The analysis boosts basalt fiber durability evaluations in cement-based composites.

Fibers doi: 10.3390/fib13100136

Authors: John P. Gaston Benedikt F. Farag Travis Thonstad Paolo M. Calvi

The combined use of macro-synthetic fibers and traditional steel reinforcement in structural concrete shows promise for enhancing shear behavior, particularly with respect to crack control, ductility, and potentially strength. However, experimental data on such systems remain scarce, especially for elements subjected to pure in-plane shear, where the interaction between fibers and conventional reinforcement is not well understood. This study contributes essential experimental evidence toward addressing this gap. Nine reinforced concrete panels were tested under monotonic in-plane shear, with transverse reinforcement ratios ranging from ρv = 0% to 0.91%, and macro-synthetic fiber contents from Vf = 0% to 0.52% by volume. Results showed that fibers were highly effective in reducing crack widths at low reinforcement levels. For specimens with ρv = 0.34%, increasing Vf from 0% to 0.52% halved the maximum crack width (from 0.6 mm to 0.3 mm) and reduced the average crack width by 22% (from 0.32 mm to 0.25 mm). Potential ductility improvements were also detected at low reinforcement ratios, with increased shear strain capacities observed as fiber content increased. In contrast, the influence of fibers on shear strength was minimal across all reinforcement levels. These findings highlight the potential of macro-synthetic fibers to enhance the performance of shear-critical elements, particularly in lightly reinforced systems, while also illustrating the need for further experimental and numerical work. The results presented here provide a fundamental dataset that can support future efforts to develop reliable assessment and design approaches accounting for the simultaneous presence of steel reinforcement and synthetic fibers in concrete elements subjected to shear.

Fibers doi: 10.3390/fib13100135

Authors: Wenqing Zhang Bin Chen Ruicheng Zhang Keshuai Liu

In this investigation, C20S (29.5 tex) and C30S (19.7 tex) ring-spun cotton yarns with different twist factors were produced using the same technological parameters for the yarn steaming process. The experimental results for yarn snarling, tensile strength, hairiness, fineness, and unevenness were compared before and after steaming. Yarn snarling was clearly reduced in the spun yarn with a higher twist factor due to the elimination of internal stress imbalances. The fineness of the yarn increased slightly after the steaming treatment. Importantly, the tensile strength of the yarn was greatly enhanced due to the adjusted fibre internal stress resulting from the steaming treatment, especially for twist factors of less than 320. The rate of increase in tensile properties decreased as the twist factor increased. Furthermore, the yarn-steaming process was beneficial for hairiness, but generally detrimental to yarn irregularity. Notably, C20S ring-spun cotton yarns exhibited a slightly higher hairiness reduction ratio and unevenness than C30S ring-spun cotton yarns at the same twist factor. Ultimately, the influence of steaming on yarn properties was thoroughly studied to improve yarn quality with reduced snarling and enhanced tensile strength.

Fibers doi: 10.3390/fib13100134

Authors: Yu’an Hu Hui Huang Meiling Chen Chunyu Pan Amsalu Nigatu Alamerew Jiacheng Zhang Mei He

To quantitatively assess the environmental impact of producing a typical bamboo-based fiber composite material—bamboo scrimber (BS)—and to explore pathways for low-carbon optimization, this study adopts the Life Cycle Assessment (LCA) method with a focus on carbon footprint analysis. Using the actual production process of an enterprise as a case study, field data were collected and analyzed for bamboo scrimber with a nominal thickness of 1.5 cm. The results show that the carbon footprint of 1 m2 of this product is 3.11 kg CO2-eq, with the manufacturing stage contributing the highest emissions at 1.45 kg CO2-eq. The primary source of carbon emissions is steam consumption, mainly occurring during the carbonization and drying of bamboo bundles. Therefore, optimizing these stages is crucial for reducing the overall carbon footprint of the product. This study provides a scientific basis for the sustainable development of bamboo-based fiber composite materials and offers practical recommendations for improving their environmental performance in production.

Fibers doi: 10.3390/fib13100133

Authors: Su-Tae Kang Nilam Adsul Bang Yeon Lee

This study investigated the structural behavior of slab-on-grade (SOG) specimens constructed using two materials: conventional concrete reinforced with steel mesh and high-ductility fiber-reinforced cement composites (HDFRCC) containing 1.2% polyethylene (PE) fiber without steel reinforcement. The compressive strengths of conventional concrete and HDFRCC were 37 MPa and 54 MPa, respectively. The average flexural tensile strength of HDFRCC was 3.9 MPa at first cracking and 9.7 MPa at peak load. Punching shear tests were performed under three loading configurations: internal (center), edge, and corner loading. Crack patterns and load–displacement responses were analyzed for both material types. Under center loading, the experimentally measured load-bearing capacities were 174.52 kN for conventional concrete and 380.82 kN for HDFRCC, with both materials exhibiting reduced capacities under edge and corner loading. Analytical predictions demonstrated close agreement with the experimental results for conventional concrete but significantly underestimated the load capacity of HDFRCC SOG. This discrepancy is attributed to the strain-hardening and crack-bridging mechanisms inherent in HDFRCC, which contribute to enhanced strength beyond conventional analytical predictions. In terms of failure mode, the conventional concrete SOG exhibited the expected flexural failure. In contrast, the HDFRCC SOG experienced either flexural failure or a combination of flexural and punching failure, in contradiction to the analytical prediction of exclusive punching shear failure. These findings indicate that the punching shear resistance of the HDFRCC SOG is substantially higher than predicted.

Fibers doi: 10.3390/fib13100132

Authors: D. Domínguez-Santos

The earthquake of 6 February 2023, in Turkey and Syria, was catastrophic for many existing buildings. Various reasons have been given to try to understand what happened, since after 2000, changes in construction methods were introduced in this area, with the aim of improving buildings. In this research, the behavior of frame buildings with a concrete structure is analyzed. To do this, graphene oxide (GO) is introduced into traditional mixtures to improve the most deficient mechanical characteristics of traditional concrete. Laboratory tests performed with GO in traditional concrete mixtures produce improvements in the mechanical analyses performed, essential characteristics for improving the structural behavior of the frame models analyzed in this research. The mechanical results show increases of 13% in the modulus of elasticity, 22% in compression strength tests, 72% in flexural-tensile strength tests, and 14% in ductility, in addition to a 4% reduction in the density of the mixture. These characteristics are essential to understand the structural improvement of the models, helping to reduce the seismic vulnerability of the structures. To reach these conclusions, static and dynamic analyses (using records of the most intense seismic activity that occurred in Turkey in 2023) are performed on three frames of 5, 10, and 20 stories in height, considering the mechanical properties of the new mixtures (traditional and GO) obtained in the laboratory. The results obtained in the analyses of the frame models using GO in the new mixtures show improvements in the structural performance of the frames, improvements that increase with increasing height of the structures. To conclude this investigation, the analyses performed on the frame models are extended with the introduction of brick walls in the exterior bays of the bare frames, a solution commonly used to improve the resistant behavior of these structures, determining a structural improvement of the models, due to the high strength and stiffness that these infill walls impart to the bare frames.

Fibers doi: 10.3390/fib13100131

Authors: Zhandos Yegizbay Maham Fatima Aliya Bekmurzayeva Zhannat Ashikbayeva Daniele Tosi Wilfried Blanc

Aldehyde dehydrogenase 1A1 (ALDH1A1) has emerged as a significant biomarker associated with tumor progression, chemoresistance, and poor prognosis in various cancers, including breast, lung, prostate, and lymphoma. Current diagnostic methods for ALDH1A1, such as flow cytometry and ELISA, are limited by long detection times, the need for labeling, and a reduced sensitivity in complex biological matrices. This study presents a novel optical fiber biosensor based on magnesium silicate nanoparticle-doped fibers for the label-free detection of ALDH1A1. The biosensor design incorporated protein G for enhanced antibody orientation and binding efficiency and anti-ALDH1A1 antibodies for specific recognition. Several sensor configurations were fabricated using a semi-distributed interferometer (SDI) format, and their performances were evaluated across a wide concentration range (10 fM–100 nM) in both phosphate-buffered saline (PBS) and fetal bovine serum (FBS). Our findings demonstrated that the inclusion of protein G significantly improved sensor sensitivity and reproducibility, achieving a limit of detection (LoD) of 172 fM in PBS. The sensor also maintained a positive response trend in FBS, indicating its potential applicability in clinically relevant samples. This work introduces the first reported optical fiber biosensor for soluble ALDH1A1 detection, offering a rapid, label-free, and highly sensitive approach suitable for future use in cancer diagnostics.

Fibers doi: 10.3390/fib13100130

Authors: Razieh Taghizadeh Pirposhteh Omolbani Kheirkhah Shamsi Naderi Fatemeh Borzouee Masoume Bazaz Mazeyar Parvinzadeh Gashti

Peptide nanofibers (PNFs) have emerged as versatile platforms for delivering therapeutic agents due to their biocompatibility, tunable characteristics, and ability to form well-ordered nanostructures. The primary goal of this review is to elaborate on the key features of common PNF fabrication strategies, including both spontaneous and non-spontaneous methods, while exploring how the amino acid sequences of these peptides influence their secondary structure and fiber formation. Additionally, we have compiled studies on PNFs that investigate various delivery approaches, such as systemic delivery, localized delivery, controlled delivery, stimuli-responsive delivery, and targeted delivery. This analysis aims to guide researchers in selecting the most suitable fabrication strategy for specific delivery applications and provide insights into choosing optimal amino acids for rational peptide design. We also focused on the applications of PNFs in delivering various therapeutic agents, including drugs, functional peptides, diagnostic and imaging agents, genes, viral vectors, and vaccines, demonstrating their significant potential in biomedical applications. The synergy between nanofiber fabrication strategies and peptide chemistries offers new avenues for advancing therapeutic products. Overall, this review serves as an important reference for the design and development of advanced PNFs for the effective delivery of various therapeutic agents.

Fibers doi: 10.3390/fib13090129

Authors: Dorota B. Szlek Emily L. Fan Margaret W. Frey

Herein, biobased 1:1 lignin/polylactic acid (PLA) blends are electrospun into micro- and nanofiber mats. Lignin samples originating from softwood, hardwood, and switchgrass biomass, extracted through the Kraft, Alcell, and CELF processes, respectively, and processed into soluble and insoluble fractions, are used. Functional properties of the mats varied with lignin biomass origin, isolation method, and fraction. Mat attributes are demonstrated through analysis of spinnability, thermal and mechanical behavior, chemical structure, morphology, hydrophobicity, and antioxidant activity. Samples spun with hardwood Alcell lignin fractions were brittle and rigid with the highest Young’s modulus, lowest elongation at break, and hydrophobic contact angle > 100°. Switchgrass CELF lignin (SGL)/PLA mats showed the highest tensile strength, a low Young’s modulus, and high elongation at break, as well as good spinnability with the smallest fiber diameter from all samples. Kraft lignin/PLA demonstrated similar mechanical properties to SGL/PLA, as well as the highest antioxidant activity, measurable within 5 min. Therefore, while they did not dictate spinnability, the lignin biomass origin and pretreatment method were shown to have a significant impact on fiber properties, while the use of lignin fractions was shown to tailor functional properties of fibers for specific end use, such as in flexible, hydrophobic, or antioxidant product applications.

Fibers doi: 10.3390/fib13090128

Authors: Piotr Turoboś Piotr Przybysz

The urgent need to decarbonize the construction sector has prompted research into sustainable alternatives to conventional concrete. This study compares two industrially produced pulps with contrasting lignin contents: a bleached kraft cellulose pulp with near-zero lignin used in paper production and a thermo-mechanical lignocellulose pulp with high lignin content used in MDF production. Fiber-reinforced composites were produced by partially replacing mineral aggregates with fibers at dosages from 0.1% to 3% by mass and air-curing to simulate practical curing conditions. The specimens were evaluated for density, water absorption, and compressive strength, with compressive strength measured at 7, 28, and 60 days. Results showed a reduction in density for both fiber types, along with increased water absorption and decreased compressive strength at higher fiber contents. Cellulose composites achieved a more favorable mechanical performance than lignocellulose composites but showed markedly higher water absorption, raising concerns about long-term durability. By testing two pulps that differ primarily in lignin content across multiple replacement ratios, the study provides a systematic comparison of their effects on composite properties. The comparison explicitly contrasts the lignin contents of the two industrial pulps—bleached kraft (~0.1%) versus thermo-mechanical (27.4%)—to isolate lignin-driven effects on hydration and property development. A practical air-curing protocol was adopted, leveraging fiber-bound/process water, thereby reflecting use cases where external water curing is constrained.

Fibers doi: 10.3390/fib13090127

Authors: Sarah Brandão Palácio Simone Oliveira Penello Katharine Valéria Saraiva Hodel Willams Teles Barbosa Gisele Assunção Reis Bruna Aparecida Souza Machado Ana Leonor Pardo Campos Godoy Maria Inês Bruno Tavares Layla Carvalho Mahnke Josiane Dantas Viana Barbosa José Lamartine de Andrade Aguiar

Wound management remains a significant global healthcare challenge, particularly due to chronic wounds that resist healing and impose economic and social burdens. Bacterial cellulose (BC), owing to its biocompatibility, high purity and moisture-handling capabilities, has gained attention as a wound dressing material. This study provides a comparative evaluation of a commercial BC film (Membracel®), a non-commercial BC from POLISA® (BCP) and an experimental BC from SENAI CIMATEC (BCC), all produced via static fermentation using distinct culture conditions. Comprehensive characterization included scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, solid-state 13C NMR, water interaction assessments, porosity and vapor permeability measurements, optical and mechanical testing and in vitro stability in simulated wound fluid. The three BC films exhibited markedly different structural and functional profiles. BCC displayed the highest crystallinity (78.7%), thermal stability and vapor permeability, indicating suitability for wounds with high exudate. BCP showed the greatest tensile strength (46.2 MPa) and flexibility, suggesting utility where mechanical robustness is required. Membracel® exhibited lower crystallinity and vapor permeability, appropriate for low-exudate wounds. All samples remained dimensionally stable in simulated wound fluid. These findings highlight clear correlations between the physicochemical properties of BC-based dressings and their potential clinical applications, supporting the development of tailored wound care solutions based on wound type and moisture management requirements.