Fibers

24 pages, 1517 KB

Open AccessArticle

Shear Interface Capacity of GFRP-Reinforced Concrete Joints

by Mostafa M. Ahmed, Mohammed G. El-Gendy and Ehab F. El-Salakawy

Fibers 2026, 14(5), 62; https://doi.org/10.3390/fib14050062 (registering DOI) - 19 May 2026

Interface shear transfer (IST) is a critical mechanism governing composite action in reinforced concrete (RC) structures. While the IST behavior in steel-RC is well established, its application to glass fiber-reinforced polymer (GFRP)-RC remains uncertain due to the scatter of experimental data and the [...] Read more.

Interface shear transfer (IST) is a critical mechanism governing composite action in reinforced concrete (RC) structures. While the IST behavior in steel-RC is well established, its application to glass fiber-reinforced polymer (GFRP)-RC remains uncertain due to the scatter of experimental data and the absence of a unified design model. This study assesses the accuracy of current IST design provisions and analytical models for GFRP-RC using a database of 107 push-off tests from the literature, including 56 specimens with an as-cast interface, 20 specimens with an intentionally roughened interface, 26 specimens with a monolithic interface, and five specimens with a smooth interface. Predictions of available models were compared with experimental peak loads. The results show that current provisions in design codes and standards either significantly underestimate or overestimate the IST capacity. The proposed analytical strain-based models in the literature improved predictions but exhibited inconsistencies across different interface conditions. Accordingly, a modified IST model is proposed based on regression analysis, incorporating a cohesion parameter as a function of the concrete strength with a GFRP strain limit of 0.003. The proposed model provides accurate, yet conservative, predictions across different interface conditions. Full article

(This article belongs to the Special Issue Fiber-Reinforced Concrete and Fiber-Reinforced Polymer Materials: Innovative Solutions in Construction Engineering)

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23 pages, 2824 KB

Open AccessArticle

Tensile and Flexural Behavior of Biaxial Non-Crimp-Fabric Composites for Two-Wheeled Electric-Vehicle Chassis

by Gabriel Constantinescu, Syed Tahir Ali Shah, José Paulo Oliveira Santos, João Manuel Cardoso, Mário Jorge de Sousa Henriques and António Manuel de Bastos Pereira

Fibers 2026, 14(5), 61; https://doi.org/10.3390/fib14050061 (registering DOI) - 18 May 2026

Abstract

The demand for lower-impact materials in mobility has increased interest in the lightweight composite structures for electric vehicles (EVs). This study presents an extended and revised dataset for biaxial non-crimp fabric (NCF) composite laminates intended for two-wheeled EV chassis applications, building on earlier [...] Read more.

The demand for lower-impact materials in mobility has increased interest in the lightweight composite structures for electric vehicles (EVs). This study presents an extended and revised dataset for biaxial non-crimp fabric (NCF) composite laminates intended for two-wheeled EV chassis applications, building on earlier published results by repeating all mechanical tests and recalculations and by adding a full stress–strain analysis, a repeatability assessment across multiple specimens, and a digital image correlation (DIC)-based strain evaluation. Three material families, represented by four laminate conditions, were investigated: carbon/epoxy composites post-cured for 4 h and 10 h, glass-fiber composites, and linen (flax) composites. The tensile and flexural behaviors were characterized according to ISO 527-4 and ISO 14125, respectively, while a GOM ARAMIS optical system was used to obtain the axial strain, transverse strain, and Poisson’s ratio. Carbon laminates showed the highest performance, with the 10 h post-cure condition reaching 1126 MPa tensile strength, up to 60 GPa Young’s modulus, 696 MPa flexural strength, and 43 GPa flexural modulus. Glass laminates provided intermediate properties, whereas flax laminates showed lower strength but higher compliance and deformation capacity. The obtained results show that the biaxial NCF composites studied in this work offer weight-saving potential for micro-mobility chassis and provide a standard-based benchmark for future durability and life-cycle studies. Full article

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1 pages, 117 KB

Open AccessRetraction

RETRACTED: Arshad, Z.; Alharthi, S.S. Enhancing the Thermal Comfort of Woven Fabrics and Mechanical Properties of Fiber-Reinforced Composites Using Multiple Weave Structures. Fibers 2023, 11, 73

by Zafar Arshad and Salman S. Alharthi

Fibers 2026, 14(5), 60; https://doi.org/10.3390/fib14050060 (registering DOI) - 15 May 2026

Abstract

The journal retracts the article titled “Enhancing the Thermal Comfort of Woven Fabrics and Mechanical Properties of Fiber-Reinforced Composites Using Multiple Weave Structures” [...] Full article

23 pages, 14021 KB

Open AccessArticle

Integration of Artificial Intelligence and Electrical Resistivity for the Prediction of Compressive Strength in Steel Fiber-Reinforced Concrete

by Ana Torre, Pedro Espinoza, Sorín Ramírez and Luisa Shuan

Fibers 2026, 14(5), 59; https://doi.org/10.3390/fib14050059 (registering DOI) - 12 May 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Special Issue Fiber-Reinforced Concrete and Fiber-Reinforced Polymer Materials: Innovative Solutions in Construction Engineering)

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16 pages, 9598 KB

Open AccessArticle

Impact of Use of Surfactants and a Pulse Sonicator on Length and Fiber Count Determinations for Natural and Synthetic Microfibers Using the OpTest Fiber Quality Analyzer

by Chanel Angelique Fortier and Michael Santiago Cintron

Fibers 2026, 14(5), 58; https://doi.org/10.3390/fib14050058 (registering DOI) - 12 May 2026

Abstract

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 [...] Read more.

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. Full article

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21 pages, 3421 KB

Open AccessArticle

Spinning Optimization of Fine Cashmere Yarns: Influence of Fiber Preparation and Spinning Technology

by Wafa Mahjoub, Sarangoo Ukhnaa, Jean-Yves Drean and Omar Harzallah

Fibers 2026, 14(5), 57; https://doi.org/10.3390/fib14050057 (registering DOI) - 11 May 2026

Abstract

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 [...] Read more.

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. Full article

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24 pages, 3754 KB

Open AccessReview

Electrospun Nanofibers for Small Molecule Sustained Delivery Targeting Articular Cartilage Regeneration: A Review

by Frederico Barbosa, Filipe Miguel, Margarida F. Domingues and João Carlos Silva

Fibers 2026, 14(5), 56; https://doi.org/10.3390/fib14050056 - 11 May 2026

Abstract

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 [...] Read more.

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. Full article

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39 pages, 5383 KB

Open AccessReview

Advancements in Design and Manufacture of High-Performance Modified Carbon/Carbon Composites for Extreme Aerospace Environments: A Comprehensive Review

by Johnson I. Humphrey, Stephen Dobreh, Md Mostafizur Rahman, Ayomide Sijuade and Okenwa I. Okoli

Fibers 2026, 14(5), 55; https://doi.org/10.3390/fib14050055 - 8 May 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Topic Advanced Composite Materials)

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16 pages, 1858 KB

Open AccessReview

Antiseptic Functionalization of Healthcare Textile Materials: Comparative Analysis of Antimicrobial Agents, Methods, and Performance—A Review

by Yakubova Dilfuza, Turaev Khayit, Alikulov Rustam, Mukumova Gulvar, Norkulov Fayzulla, Kholboeva Aziza and Ahatov Behzod

Fibers 2026, 14(5), 54; https://doi.org/10.3390/fib14050054 - 1 May 2026

Abstract

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 [...] Read more.

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. Full article

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19 pages, 7256 KB

Open AccessArticle

Techno-Mechanical and Structural Properties of Indian Mulberry Silkworm Fibers: An Insight into the Structure–Property Relationship

by Azad Gull, Anil Kumar Mysore Nagaraj, Thomas Braxton, Amit Kumar, Dhaneshwar Padhan, Rubia Bukhari, Swathi Koppa Rameshjois and Ravindra Aurade

Fibers 2026, 14(5), 53; https://doi.org/10.3390/fib14050053 - 28 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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21 pages, 4242 KB

Open AccessArticle

The Impact of Hydrogen Bond Basicity of Ionic Liquids on Cotton Cellulose Dissolution: Experimental and Simulation Study

by Niwanthi Dissanayake, Vidura D. Thalangamaarachchige, Edward L. Quitevis, Zeyad Zeitoun and Noureddine Abidi

Fibers 2026, 14(5), 52; https://doi.org/10.3390/fib14050052 - 28 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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22 pages, 3709 KB

Open AccessArticle

Influence of FRP Confinement on the Compressive Strength of Concrete with Recycled Rubber

by Maria Concetta Cocchiara, María Isabel Prieto, Alfonso Cobo and Fernando Israel Olmedo

Fibers 2026, 14(5), 51; https://doi.org/10.3390/fib14050051 - 27 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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32 pages, 2930 KB

Open AccessReview

Review of the Phosphorylation of Lignocellulosic Fibers: Reaction Products, Characterization, and Potential Applications

by Lahbib Abenghal, Dan Belosinschi, Hamid Lamoudan, Aleksandra Mikhailidi and François Brouillette

Fibers 2026, 14(5), 50; https://doi.org/10.3390/fib14050050 - 27 Apr 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Collection Review Papers of Fibers)

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17 pages, 2770 KB

Open AccessArticle

Evaluation of the Effects of Biochar Pyrolysis Temperature and Loading on the Polyester Biocomposite Properties

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

Fibers 2026, 14(5), 49; https://doi.org/10.3390/fib14050049 - 24 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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19 pages, 6677 KB

Open AccessArticle

Fibre Property Distributions and Rheology as Indicators of Mill-Scale Pulp Refining Performance

by Zahra Gholami, Johan Persson, Kateryna Liubytska, Angeles Blanco, Fritjof Nilsson and Birgitta A. Engberg

Fibers 2026, 14(5), 48; https://doi.org/10.3390/fib14050048 - 24 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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13 pages, 2921 KB

Open AccessArticle

Investigation of Shredded Glass Fiber Composites from Post-Industrial and Post-Consumer Waste from Wind Turbine Blades for Reuse in Structural Epoxy Resin Plates

by Bianca Purgleitner, Barbara Liedl and Christoph Burgstaller

Fibers 2026, 14(5), 47; https://doi.org/10.3390/fib14050047 - 24 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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22 pages, 5797 KB

Open AccessArticle

Computational Investigation of Lightning Strike Damage Effects on an Aircraft Fuel Tank Cover

by Feng Yue and Xiaofeng Xue

Fibers 2026, 14(5), 46; https://doi.org/10.3390/fib14050046 - 23 Apr 2026

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Topic Advanced Carbon Fiber Reinforced Composite Materials, 3rd Edition)

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20 pages, 13493 KB

Open AccessArticle

Modeling of Basalt Fiber Self-Healing Processes in Aggressive Alkaline Environment of OPC Concrete: The Impact of Metakaolin

by Pavlo Kryvenko, Igor Rudenko, Oleksandr Gelevera and Oleksandr Konstantynovskyi

Fibers 2026, 14(5), 45; https://doi.org/10.3390/fib14050045 - 23 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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14 pages, 3406 KB

Open AccessArticle

Antibacterial and Antioxidant Activity of Cotton Fabric Treated with Alginate-Based Microcapsules Containing Nigella sativa Oil as Core Material

by Nusrat Bibi, Imran Ahmad Khan, Kashif Javed, Asfandyar Khan, Tayyab Naveed, Mainul Morshed, Fiaz Hussain and Muhammad Junaid Saleem

Fibers 2026, 14(4), 44; https://doi.org/10.3390/fib14040044 - 10 Apr 2026

Abstract

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 [...] Read more.

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. Full article

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