Fibers

21 pages, 26641 KiB

Open AccessArticle

A CNN-Based Method for Quantitative Assessment of Steel Microstructures in Welded Zones

by Cássio Danelon de Almeida, Thales Tozatto Filgueiras, Moisés Luiz Lagares, Jr., Bruno da Silva Macêdo, Camila Martins Saporetti, Matteo Bodini and Leonardo Goliatt

Fibers 2025, 13(5), 66; https://doi.org/10.3390/fib13050066 - 15 May 2025

Abstract

The mechanical performance of metallic components is intrinsically linked to their microstructural features. However, the manual quantification of microconstituents in metallographic images remains a time-consuming and subjective task, often requiring over 15 min per image by a trained expert. To address this limitation, [...] Read more.

The mechanical performance of metallic components is intrinsically linked to their microstructural features. However, the manual quantification of microconstituents in metallographic images remains a time-consuming and subjective task, often requiring over 15 min per image by a trained expert. To address this limitation, this study proposes an automated approach for quantifying the microstructural constituents from low-carbon steel welded zone images using convolutional neural networks (CNNs). A dataset of 210 micrographs was expanded to 720 samples through data augmentation to improve model generalization. Two architectures (AlexNet and VGG16) were trained from scratch, while three pre-trained models (VGG19, InceptionV3, and Xception) were fine-tuned. Among these, VGG19 optimized with stochastic gradient descent (SGD) achieved the best predictive performance, with an

R^{2}

of 0.838, MAE of 5.01%, and RMSE of 6.88%. The results confirm the effectiveness of CNNs for reliable and efficient microstructure quantification, offering a significant contribution to computational metallography. Full article

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14 pages, 4191 KiB

Open AccessArticle

Evaluating Carbon Fibre-Reinforced Polymer Composite Helical Spring Performances Under Various Compression Angles

by Yupu Dai, Joel Chong, Ling Chen and Youhong Tang

Fibers 2025, 13(5), 65; https://doi.org/10.3390/fib13050065 - 14 May 2025

Abstract

Springs are widely used in industries such as aerospace and automotive. As the demand for emission reduction grows, the research on lightweight spring performance is becoming increasingly important. This study analyses the mechanical performance of triple-layer braided composite helical springs (TCHS) under various [...] Read more.

Springs are widely used in industries such as aerospace and automotive. As the demand for emission reduction grows, the research on lightweight spring performance is becoming increasingly important. This study analyses the mechanical performance of triple-layer braided composite helical springs (TCHS) under various loads and compression angles. Firstly, the optimal high-temperature curing condition of the epoxy resin was determined through tensile and three-point bending analysis. Then, TCHS were fabricated based on optimal epoxy curing conditions, and multi-angle compression tests under different loads were carried out. Simultaneously, strain gauges were installed at various positions and orientations on the inner and outer sides of the spring wire to reveal strain patterns during the compression. The test results indicate that stiffness decreases with increasing compression angle. Additionally, the strain in the inner and outer positions in different directions of the same region increased with the rise in compression force and angle, and strains in the helical direction were the largest. Subsequently, strain in the helical direction across different regions further showed that maximum strain occurred in the centre coil (region 2), with inner and outer helical direction strains reaching −5116.89 με and 5700.15 με, respectively, which are 71.3% and 90.4% higher than those in region 1 and 73.2% and 92.9% higher than those in region 3. As the compression load increased, cracks appeared on the outer side of the centre coil. In addition, the crack was perpendicular to the helical direction, further confirming that the highest strain occurred in the helical direction. This study provides an in-depth analysis of the impact of angle-specific loads on TCHS, offering valuable insights for the design and optimisation of composite helical springs and laying a theoretical foundation for their future development. Full article

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64 pages, 6390 KiB

Open AccessReview

Greening Fused Deposition Modeling: A Critical Review of Plant Fiber-Reinforced PLA-Based 3D-Printed Biocomposites

by Muneeb Tahir and Abdel-Fattah Seyam

Fibers 2025, 13(5), 64; https://doi.org/10.3390/fib13050064 - 14 May 2025

Abstract

Fused deposition modeling (FDM) 3D printing (3DP) of PLA biocomposites reinforced with plant-derived cellulosic fibrous materials, including spun yarn, microcrystalline, microfibrillar, nanofibrillar cellulose, and cellulose nanocrystals, offers an environmentally sustainable solution to the mechanical limitations of polymer-only printed materials. Micron- and submicron-scale cellulosic [...] Read more.

Fused deposition modeling (FDM) 3D printing (3DP) of PLA biocomposites reinforced with plant-derived cellulosic fibrous materials, including spun yarn, microcrystalline, microfibrillar, nanofibrillar cellulose, and cellulose nanocrystals, offers an environmentally sustainable solution to the mechanical limitations of polymer-only printed materials. Micron- and submicron-scale cellulosic fibers are valued for their renewability, non-toxicity, high surface area, and favorable elastic and specific moduli; notably, micron-scale reinforcements are particularly attractive due to their ease of large-scale industrial production and commercial viability. Similarly, PLA benefits from large-scale production, contributes to CO₂ sequestration through its raw material precursors, and requires less energy for production than non-biodegradable petroleum-derived polymers. Incorporating these raw materials, each of which offers attractive performance properties, complementary commercial strengths, and environmental benefits, as constituent phases in FDM 3D-printed biocomposites (FDMPBs) can further enhance the environmental responsiveness of an already low-waste FDM 3DP technology. Inspired by these compelling advantages, this paper critically reviews research on FDMPB with cellulosic reinforcements in a PLA matrix, uniquely categorizing studies based on the form of cellulosic reinforcement and its impact on the biocomposite’s structure and mechanical performance. Additionally, the review covers biocomposite filament production methods and the equipment involved, presenting an alternative framework for cataloging FDMPB research. A comprehensive literature analysis reveals that the wide variation in feedstocks, fiber–matrix compounding methods, equipment, and processing parameters used in filament production and 3DP complicates the comparison of FDMPB mechanical properties across studies, often resulting in conflicting outcomes. Key processing parameters have been compiled to bridge this gap and offer a more nuanced understanding of the cause-and-effect relationships governing biocomposite properties. Finally, targeted recommendations for future research on developing FDMPB with a PLA matrix and micron-scale cellulosic reinforcements are provided, addressing the knowledge gaps and challenges highlighted in the peer-reviewed literature. Full article

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21 pages, 4029 KiB

Open AccessArticle

Virginia Mallow: The Lost Fiber of the Future?

by Gabriela Vanja, Sandra Bischof and Zorana Kovačević

Fibers 2025, 13(5), 63; https://doi.org/10.3390/fib13050063 - 13 May 2025

Abstract

Virginia mallow or Sida hermaphrodita (L.) Rusby (SH) is a perennial plant from the Malvaceae family (mallows) that is used for medicinal purposes, reducing soil erosion, cleaning soil, and most recently for energy production. The potential of sustainable lignocellulosic agro-waste is immense as [...] Read more.

Virginia mallow or Sida hermaphrodita (L.) Rusby (SH) is a perennial plant from the Malvaceae family (mallows) that is used for medicinal purposes, reducing soil erosion, cleaning soil, and most recently for energy production. The potential of sustainable lignocellulosic agro-waste is immense as it represents Earth’s most abundant organic compound. This paper explores fibers isolated from SH stems, a plant with significant industrial application potential, including technical textiles and biocomposites. The fibers were harvested in January, March, and November of 2020 and in January and March of 2021, and their yield, mechanical properties, moisture content, and density were thoroughly analyzed. The fiber yield showed slight variations depending on the harvest time, with consistent results observed across different years, suggesting stable productivity. The SH fibers demonstrated a favorable moisture content, making them suitable for storage and processing, and their density ranged between 1.52 and 1.58 g/cm³, comparable to that of other natural fibers. According to this research, the best mechanical properties were observed in the winter harvest. Furthermore, the high percentage of solid residue left after fiber extraction shows promise for sustainable utilization, primarily for biofuel production. This study underscores the versatility and sustainability of SH fibers, positioning them as a valuable resource for a wide range of industrial applications. Full article

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18 pages, 14418 KiB

Open AccessArticle

Recovery of End-of-Life Building Materials: Thermal Decomposition and Phase Transformation of Chrysotile in Asbestos-Containing Fiber Cement Boards

by António Curado, Leonel J. R. Nunes, Arlete Carvalho, João Abrantes, Eduarda Lima and Mário Tomé

Fibers 2025, 13(5), 62; https://doi.org/10.3390/fib13050062 - 9 May 2025

Abstract

The circular economy emphasizes reducing, recycling, and reusing waste, a principle that is challenging to apply to hazardous materials like asbestos-containing construction waste, typically destined for landfills due to limited recycling options. This experimental study investigates the physicochemical characterization of asbestos fibers in [...] Read more.

The circular economy emphasizes reducing, recycling, and reusing waste, a principle that is challenging to apply to hazardous materials like asbestos-containing construction waste, typically destined for landfills due to limited recycling options. This experimental study investigates the physicochemical characterization of asbestos fibers in fiber cement boards and assesses the efficacy of mechanical grinding and thermal treatments to transform these fibers into non-fibrous, stable phases for reuse in sustainable construction applications, such as cement and mineral wool production. Using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), we analyzed samples from end-of-life fiber cement panels, subjecting them to thermal treatments at 700 °C, 1000 °C, and 1200 °C. Results show that, while grinding reduces particle size, it does not eliminate fibrous structures; however, thermal treatment above 1000 °C fully converts chrysotile into forsterite and enstatite, eliminating health risks and enabling material reuse. These findings, that are part of the FiberRec project, support a systematic approach to integrating asbestos-containing waste into a closed-loop material cycle, significantly reducing carbon emissions and landfill dependency. Full article

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10 pages, 2843 KiB

Open AccessArticle

Passively Q-Switched Thulium-Doped Fiber Laser Employing a Glycerin-Based Saturable Absorber

by Edwin Addiel Espinosa-De-La-Cruz, Manuel Durán-Sánchez, Ulises Alcántara-Bautista, Alejandro Reyes-Mora, Adalid Ibarra-Garrido, Ivan Armas-Rivera, Luis Alberto Rodríguez-Morales, Miguel Bello-Jiménez and Baldemar Ibarra-Escamilla

Fibers 2025, 13(5), 61; https://doi.org/10.3390/fib13050061 - 8 May 2025

Abstract

A passively Q-switched Thulium-doped fiber laser based on glycerin as the saturable absorber is experimentally demonstrated for the first time. The saturable absorber consists of two FC/PC connectors aligned within a mechanical fiber-fiber coupler, with the intervening gap filled with glycerin. Such a [...] Read more.

A passively Q-switched Thulium-doped fiber laser based on glycerin as the saturable absorber is experimentally demonstrated for the first time. The saturable absorber consists of two FC/PC connectors aligned within a mechanical fiber-fiber coupler, with the intervening gap filled with glycerin. Such a saturable absorber is integrated into a compact ring cavity, enabling passive Q-switched laser operation. Starting at a minimum pump power of 1.7 W, Q-switched pulses with a central wavelength of 1946 nm are obtained. At the maximum pump power of 2.4 W, the laser generates pulses with a duration of approximately 2 µs, a repetition rate of 26.7 kHz, and a pulse energy of 1.08 µJ. To the best of our knowledge, this is the first demonstration of passively Q-switched laser operation utilizing a glycerin-based saturable absorber for generating pulsed emission at the 2-µm wavelength region. This breakthrough represents a significant advancement in fiber laser technology, introducing a novel and efficient approach to pulse generation. Full article

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26 pages, 10042 KiB

Open AccessArticle

Verification of Crack Width Evaluation in Fiber-Reinforced Cementitious Composite Reinforced with Various Types of Fiber-Reinforced Polymer Bars

by Hideto Sasaki, Helen Negash Shiferaw and Toshiyuki Kanakubo

Fibers 2025, 13(5), 60; https://doi.org/10.3390/fib13050060 - 7 May 2025

Abstract

This study aims to verify the adaptability of a crack width evaluation method for fiber-reinforced cementitious composite (FRCC) proposed by the authors to various combinations of fiber-reinforced polymer (FRP) bars and FRCCs. As this evaluation method requires bond constitutive laws between FRP bars [...] Read more.

This study aims to verify the adaptability of a crack width evaluation method for fiber-reinforced cementitious composite (FRCC) proposed by the authors to various combinations of fiber-reinforced polymer (FRP) bars and FRCCs. As this evaluation method requires bond constitutive laws between FRP bars and FRCC, bond tests between FRP and FRCCs were conducted. The FRP and FRCC combinations used in the bond tests were spiral-type CFRP and GFRP bars with PVA-FRCC, as well as strand-type CFRP bars with aramid–FRCC. The maximum bond stress tended to increase as the rib–height ratio of the spiral-type bars increased. When the rib–height ratio increased by 50%, the maximum bond stress of the CFRP and GFRP bars increased by 11% and 33%, respectively. For aramid–FRCC, the average maximum bond stress in the FRCC with a 0.25% volume fraction was 1.67 times that in mortar, and that in 0.50% was 2.01 times that in mortar. The bond constitutive laws were modeled using the trilinear model. Verifications of the method’s adaptability were conducted using tension tests on prisms made of spiral-type CFRP and GFRP bars with PVA-FRCC. As a result of the tension tests, when the FRP strain reached approximately 0.3%, the crack width was about 0.2 mm for CFRP bars and about 0.1 mm for GFRP bars. Verifications were also conducted using four-point bending tests on strand-type CFRP bar beams with aramid–FRCC. The crack width at the same FRP strain tended to become smaller as the fiber volume fraction of FRCC increased. When the FRP strain reached approximately 0.2%, the average crack width of the mortar specimen was around 0.25 mm, whereas it was about 0.15 mm in FRCC with a 0.25% volume fraction and about 0.10 mm at 0.5%. The test results for FRP strain versus crack width relationships were compared with the calculations using the crack width prediction formula. The test results and calculation results were in good agreement. Full article

(This article belongs to the Special Issue Recent Developments in Structural Applications of Fiber-Reinforced Concrete)

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19 pages, 9914 KiB

Open AccessArticle

Lithium Orthosilicate Solid Porous Membranes for CO₂ Capture Obtained from Silica Microfibers

by Joaquín Penide, Efstratios Stavrakakis, Félix Quintero, Danai Poulidi, Antonio Riveiro, Jesús del Val, Rafael Comesaña, Fernando Lusquiños and Juan Pou

Fibers 2025, 13(5), 59; https://doi.org/10.3390/fib13050059 - 7 May 2025

Abstract

Lithium orthosilicate (Li₄SiO₄) has demonstrated a high CO₂ adsorption rate and capacity and its suitability to be implemented in industry as CO₂ capture technology at high temperatures. The optimum solid adsorbent should present a porous structure to [...] Read more.

Lithium orthosilicate (Li₄SiO₄) has demonstrated a high CO₂ adsorption rate and capacity and its suitability to be implemented in industry as CO₂ capture technology at high temperatures. The optimum solid adsorbent should present a porous structure to maximize surface and enable a high sorption rate. In this work, we present an original approach based on the use of a novel architecture of precursors in the form of very thin free-standing solid silica fibers. An original technique called continuous fiberizing by laser melting (Cobiflas) was used to obtain membranes of pure silica fibers with diameters in the micrometer range, forming a porous membrane which offer a high surface and porous connectivity to be used as precursors without any supporting substrate. Then, we employed a method based on the impregnation of the silica fibers within a lithium-containing aqueous solution and subsequent calcination to obtain a porous solid adsorbent with the maximum proportion of lithium orthosilicate. This method is compared with the results obtained using a sol-gel powder method by analyzing their composition using X-Ray Diffraction (XRD), and their adsorption capacity and adsorption kinetics by Thermogravimetric analyses (TGA). As a result, an outstanding type of solid adsorbent is reported with a 31% adsorption capacity and a total regeneration capacity, which is over 0.8 efficiency with regard to the theoretical maximum adsorption of this material. Full article

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16 pages, 8231 KiB

Open AccessArticle

A Study on the Effect of an Oxidizing Atmosphere During the Recycling of CFRP by Pyrolysis

by Cynthie Dega, Ali Jadidinia and Rachid Boukhili

Fibers 2025, 13(5), 58; https://doi.org/10.3390/fib13050058 - 7 May 2025

Abstract

Composite materials are increasingly in demand. However, challenges such as high raw-material costs and complicated waste management impede their adoption. Overcoming these obstacles requires efficient recycling methods. Pyrolysis effectively recycles carbon fiber-reinforced polymers (CFRPs). This study proposes a cost-effective CFRP recovery approach utilizing [...] Read more.

Composite materials are increasingly in demand. However, challenges such as high raw-material costs and complicated waste management impede their adoption. Overcoming these obstacles requires efficient recycling methods. Pyrolysis effectively recycles carbon fiber-reinforced polymers (CFRPs). This study proposes a cost-effective CFRP recovery approach utilizing conventional ovens to minimize recycling expenses and maximize reclaimed-product value. Pyrolysis was conducted under atmospheric conditions at 450–600 °C, lasting 1–6 h at each temperature. It was optimal at 2.5 h and 500 °C. Higher temperatures caused fiber degradation, and lower temperatures excessively prolonged duration. After determining the optimal conditions, composite plates were produced using recycled carbon fibers and a vacuum-assisted resin infusion process. Subsequent physical characterization and mechanical tests were conducted on these plates to assess the recycled-CFRP properties. The recovered tensile strength and tensile modulus were 88% and 97% that of virgin carbon fibers (vCF), respectively. Full article

(This article belongs to the Special Issue Mechanical Behaviour of Reinforced Thermosetting Polymers with Fibers: Analytical/Numerical Models and Experimental Evidence)

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17 pages, 4475 KiB

Open AccessArticle

Performance of Carbon Fiber-Reinforced Date Palm Midrib Composites

by Mohammad Hassan Mazaherifar, Octavia Zeleniuc, Camelia Cerbu, Sergiu-Valeriu Georgescu, Antonela Lungu and Camelia Coșereanu

Fibers 2025, 13(5), 57; https://doi.org/10.3390/fib13050057 - 7 May 2025

Abstract

This paper evaluates the performance of composites made from date palm (Phoenix dactylifera L.) midribs reinforced with carbon fiber. Two types of adhesives—unsaturated polyester and epoxy resin—were used as binder for the experimental panels. The physical properties and mechanical strength of the [...] Read more.

This paper evaluates the performance of composites made from date palm (Phoenix dactylifera L.) midribs reinforced with carbon fiber. Two types of adhesives—unsaturated polyester and epoxy resin—were used as binder for the experimental panels. The physical properties and mechanical strength of the composites, as a function of fiber types, lamination configuration, as well as adhesive types, were determined. The density levels of the panels made using epoxy and unsaturated polyester resin were found to be 1103 kg/m³ and 1133 kg/m³, respectively. Panels made using polyester adhesive had 6.05% and 3.98% for water absorption and thickness swelling values, respectively. Corresponding values of 3.09% and 6.35% were found for the panels made using epoxy resin. Mechanical properties of the samples revealed that carbon fiber-reinforced epoxy hybrids offer superior mechanical performance, whereas polyester-based hybrids may be more suitable for impact-resistant applications. Stereo-microscopy and vertical density profile (VDP) analysis of the panels resulted in variations in layer adhesion and density distribution. Based on the findings in this work, carbon fiber-reinforced epoxy-bonded hybrid panels exhibited superior mechanical properties, while those panels made using polyester-based binder would be more suitable where impact resistance is desired. The combination of date palm fibers and carbon fiber presents significant potential for sustainable applications, offering a balance of strength and durability. Full article

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12 pages, 1671 KiB

Open AccessArticle

Crosstalk Suppression in Multi-Core Fiber Through Modulation of the Refractive Index

by Er’el Granot

Fibers 2025, 13(5), 56; https://doi.org/10.3390/fib13050056 - 3 May 2025

Abstract

One promising method to increase the bit-rate capacity of optical fibers is the use of Multi-Core Fibers (MCFs). However, the close proximity of the cores can lead to data interference due to crosstalk between them. A novel approach is proposed to suppress crosstalk [...] Read more.

One promising method to increase the bit-rate capacity of optical fibers is the use of Multi-Core Fibers (MCFs). However, the close proximity of the cores can lead to data interference due to crosstalk between them. A novel approach is proposed to suppress crosstalk in MCFs. It is demonstrated that if the refractive index of the cores is weakly modulated harmonically, with each core having a different phase, crosstalk in two-core and three-core fibers can be entirely eliminated. Furthermore, by using specific configurations—either by selecting the fiber length or by arranging the cores’ spatial layout—crosstalk can be suppressed even in fibers with more than three cores. Full article

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18 pages, 10492 KiB

Open AccessArticle

Predicting Nonlinear Behavior of Cellular Cross-Laminated Timber Under Bending and Rolling Shear

by Suman Pradhan and Mostafa Mohammadabadi

Fibers 2025, 13(5), 55; https://doi.org/10.3390/fib13050055 - 2 May 2025

Abstract

This study investigates the structural performance of cellular cross-laminated timber (CCLT) through a nonlinear finite element model using Hill and Hashin damage criteria in Abaqus. This study evaluates these criteria in simulating CCLT’s mechanical behavior under bending and shear loading. Experimental validation included [...] Read more.

This study investigates the structural performance of cellular cross-laminated timber (CCLT) through a nonlinear finite element model using Hill and Hashin damage criteria in Abaqus. This study evaluates these criteria in simulating CCLT’s mechanical behavior under bending and shear loading. Experimental validation included short-span and long-span bending tests, along with rolling shear tests. In bending simulations, the Hill criterion predicted maximum loads with a 7% error for long-span beams when modeling lumber as solid elements and the corrugated panel as shell elements. When the entire CCLT was modeled using shell elements, the error increased to 9%. For the short-span bending, the error remained at 8% regardless of element type. The Hashin model provided more accurate results, with deviations of 0.2% for long-span beams and 1% for short-span beams. Both models successfully predicted failure mechanisms, identifying tension failure in the lumber under long-span bending and shear failure in the corrugated core under short-span bending. In rolling shear tests, the Hill criterion underestimated the maximum shear load by 11%, while the Hashin criterion had a larger underestimation of 26%. Despite these discrepancies, both models effectively captured the nonlinear behavior of CCLT panels. These findings highlight the potential of Hill and Hashin criteria for modeling CCLT’s mechanical response, offering valuable insights into structural design applications. Full article

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14 pages, 1777 KiB

Open AccessArticle

Spanish broom Production Chain Improvement with a View to Sustainable Development

by Pavel Malyzhenkov, Giuseppe Chidichimo, Chiara La Torre and Alessia Fazio

Fibers 2025, 13(5), 54; https://doi.org/10.3390/fib13050054 - 1 May 2025

Abstract

The extraction of Spanish broom fibers presents significant commercial opportunities. However, the traditional production process is associated with a high environmental impact and considerable waste. This work demonstrates how to address the limitations of alkaline maceration by employing a natural maceration process. This [...] Read more.

The extraction of Spanish broom fibers presents significant commercial opportunities. However, the traditional production process is associated with a high environmental impact and considerable waste. This work demonstrates how to address the limitations of alkaline maceration by employing a natural maceration process. This innovative method not only reduces environmental harm but also facilitates the extraction of large quantities of pectin (6%). Notably, pectin has been obtained from the waste product of broom processing, creating a dual source of profit: both cellulose and pectin. This means that not only can the fibers be utilized for various applications, but the by-products can also be transformed into a valuable marketable product. Pectin, a valuable polysaccharide widely used in the food industry as a gelling agent, thickener, and stabilizer, can significantly increase the economic viability of broom cultivation. Moreover, the high yield of pectin from Spanish broom underscores the plant’s potential as a sustainable resource, making it an attractive alternative to more environmentally damaging crops. Pectin obtained has been characterized by Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM), providing valuable insights into its structural and morphological properties. Full article

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21 pages, 4947 KiB

Open AccessArticle

Effective Flexural Strengthening of Reinforced Concrete T-Beams Using Bonded Fiber-Core Steel Wire Ropes

by Anggun Tri Atmajayanti, Yanuar Haryanto, Fu-Pei Hsiao, Hsuan-Teh Hu and Laurencius Nugroho

Fibers 2025, 13(5), 53; https://doi.org/10.3390/fib13050053 - 30 Apr 2025

Abstract

This study experimentally and numerically investigated the effectiveness of fiber-core steel wire ropes (FC-SWRs) in enhancing the flexural performance of reinforced concrete (RC) T-beams using a bonding technique. The investigation focused on deflection, flexural load-carrying capacity, and failure modes, along with key behaviors [...] Read more.

This study experimentally and numerically investigated the effectiveness of fiber-core steel wire ropes (FC-SWRs) in enhancing the flexural performance of reinforced concrete (RC) T-beams using a bonding technique. The investigation focused on deflection, flexural load-carrying capacity, and failure modes, along with key behaviors such as ductility, stiffness, energy absorption, and steel strain response. Two beams were tested under four-point bending until failure—one serving as the control specimen and the other strengthened with bonded FC-SWRs to improve its flexural behavior. Additionally, an analytical study was conducted using a computer program based on the Modified Compression Field Theory (MCFT), and the results were compared with experimental findings. The validation of the analytical model enabled further parametric investigations, examining the influence of the FC-SWR diameter, modulus of elasticity, and steel reinforcement ratio on flexural performance. Full article

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18 pages, 5924 KiB

Open AccessArticle

Thermal Performance of Bio-Based Materials for Sustainable Building Insulation: A Numerical Study

by Labouda Ba, Abdelkrim Trabelsi, Tien Tung Ngo, Prosper Pliya, Ikram El Abbassi and Cheikh Sidi Ethmane Kane

Fibers 2025, 13(5), 52; https://doi.org/10.3390/fib13050052 - 30 Apr 2025

Abstract

This study investigates the thermal and energy performance of various bio-based materials, including Typha Australis, straw, banana fiber, Alfa fiber, peanut shells, and VSS (a blend of wood pulp, cotton, flax, and hemp), in comparison to conventional concrete. A combined approach integrating numerical [...] Read more.

This study investigates the thermal and energy performance of various bio-based materials, including Typha Australis, straw, banana fiber, Alfa fiber, peanut shells, and VSS (a blend of wood pulp, cotton, flax, and hemp), in comparison to conventional concrete. A combined approach integrating numerical simulations and experimental analyses was employed to ensure robust and comprehensive insights. COMSOL Multiphysics was utilized for detailed thermal modeling of wall assemblies, while TRNSYS enabled dynamic simulations to evaluate the impact of these materials on overall cooling energy demand. The results demonstrate that bio-based materials offer significantly improved thermal insulation, reducing air conditioning needs by over 30% relative to concrete, with banana fiber exhibiting the highest performance. This study underscores the need for industrial-scale optimization, supportive regulatory frameworks, and real-world implementation to promote broader adoption. Despite their strong potential, challenges remain, particularly regarding cost-effectiveness, durability, and market penetration. Ultimately, this research advocates for a transition toward more sustainable and environmentally conscious construction practices, aligning with efforts to reduce CO₂ emissions and enhance building energy efficiency. Full article

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20 pages, 8165 KiB

Open AccessArticle

Characterization and Application of Different Types of Pineapple Leaf Fibers (PALF) in Cement-Based Composites

by Julianna M. da Silva, Adilson Brito de Arruda Filho, Lidianne do N. Farias, Everton Hilo de Souza, Fernanda V. D. Souza, Cláudia F. Ferreira and Paulo R. L. Lima

Fibers 2025, 13(5), 51; https://doi.org/10.3390/fib13050051 - 30 Apr 2025

Abstract

The use of plant fibers as reinforcement in cement composites has gained significant interest due to their favorable mechanical properties and inherent sustainability, particularly when sourced from agro-industrial waste. In this study, six types of pineapple leaf fibers from commercial and hybrid varieties [...] Read more.

The use of plant fibers as reinforcement in cement composites has gained significant interest due to their favorable mechanical properties and inherent sustainability, particularly when sourced from agro-industrial waste. In this study, six types of pineapple leaf fibers from commercial and hybrid varieties were characterized in terms of morphology, crystallinity index, water absorption, dimensional stability, and mechanical properties to evaluate their potential as reinforcement in cement-based composites. An anatomical analysis of the leaves was conducted to identify fiber distribution and structural function. Cement-based composites reinforced with 1.5% (by volume) of long and aligned pineapple leaf fibers were produced and tested in bending. The results indicate that the tensile strength of pineapple fibers, ranging from 180 to 753 MPa, surpasses that of fibers already successfully used in composite reinforcement. Water absorption values ranged from 150% to 187%, while fiber diameter varied between 45% and 79% as fiber moisture changed from the dry state to the saturated state. The flexural behavior of the composites modified with pineapple leaf fibers exhibited multiple cracking and deflection hardening, with increases in flexural strength ranging from 6.25 MPa to 11 MPa. The cracking pattern under bending indicated a strong fiber–matrix bond, with values between 0.41 MPa and 0.93 MPa. All composites demonstrated high flexural toughness and great potential for the development of construction elements. Full article

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15 pages, 6656 KiB

Open AccessArticle

Preparation of ZIF-67@PAN Nanofibers for CO₂ Capture: Effects of Solvent and Time on Particle Morphology

by Guilherme Henrique Franca Melo, Tiffany Yau, Yuxin Liu and Uttandaraman Sundararaj

Fibers 2025, 13(5), 50; https://doi.org/10.3390/fib13050050 - 22 Apr 2025

Abstract

Advanced materials including metal–organic frameworks (MOFs) are a critical piece of the puzzle in the search for solutions to various scientific and technological challenges, such as climate change due to the ever-increasing emissions of greenhouse gas. There is intense interest in MOFs due [...] Read more.

Advanced materials including metal–organic frameworks (MOFs) are a critical piece of the puzzle in the search for solutions to various scientific and technological challenges, such as climate change due to the ever-increasing emissions of greenhouse gas. There is intense interest in MOFs due to their potential use for a variety of environmental applications, including catalysis and gas storage. In this work, we specifically focus on the in situ growth of zeolitic imidazolate framework-67 (ZIF-67) on poly(acrylonitrile) (PAN) fibers and its potential application in CO₂ adsorption. Nanofibers were spun from a solution containing PAN and cobalt (II) nitrate hexahydrate using electrospinning. Then, the fibers were immersed in solution with 2-methylimidazole for different time durations. Via the diffusion of the cobalt ions through the fibers and interaction with the ligands in the solution, ZIF-67 was formed. From analysis via SEM, FTIR, PXRD, and CO₂ adsorption, it is evident that varying different parameters—the type of solvent, immersion time, and ligand concentration—affected the morphology of the formed ZIF-67. It was found that immersion for 4 h in 6.0 mg/mL of ligands in methanol created the ZIF-67@PAN best suited for CO₂ adsorption, showing a CO₂ uptake of 0.4 mmol/g at 1.2 bar and 273 K. Full article

(This article belongs to the Special Issue Electrospinning Nanofibers)

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23 pages, 10671 KiB

Open AccessArticle

Multi-Scale Toughening of UHPC: Synergistic Effects of Carbon Microfibers and Nanotubes

by J. D. Ruiz Martínez, J. D. Ríos, H. Cifuentes and C. Leiva

Fibers 2025, 13(4), 49; https://doi.org/10.3390/fib13040049 - 21 Apr 2025

Abstract

This study investigates multi-scale reinforcement of Ultra-High-Performance Concrete through targeted modifications of its mechanical and fracture-resistant properties via carbon microfibers and carbon nanotubes. The research employed comprehensive characterization techniques including workability tests, mercury porosimetry for microscale porosity analysis, and X-ray tomography for macro-scale [...] Read more.

This study investigates multi-scale reinforcement of Ultra-High-Performance Concrete through targeted modifications of its mechanical and fracture-resistant properties via carbon microfibers and carbon nanotubes. The research employed comprehensive characterization techniques including workability tests, mercury porosimetry for microscale porosity analysis, and X-ray tomography for macro-scale pore evaluation. Mechanical performance was assessed through compression strength, tensile strength, and fracture energy measurements. Results demonstrated significant performance enhancements testing UHPC samples with 6 mm carbon microfibers (9 kg/m³) and varying carbon nanotubes dosages (0.11–0.54 wt%). The addition of carbon microfibres improved compressive strength by 12%, while incorporating 0.54 wt% carbon nanotubes further increased strength by 24%. Remarkably, the combined reinforcement strategy yielded a 313% increase in tensile strength compared to the reference mixture. The synergistic effect of carbon fibers and carbon nanotubes proved particularly effective in enhancing concrete performance. This multi-scale reinforcement approach presents a promising alternative to traditional steel fiber reinforcement, offering superior mechanical properties and potential advantages in corrosive environments. Full article

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21 pages, 21103 KiB

Open AccessArticle

Modelling Pore Size Distribution Function of Twist-Texturized Yarns and Single-Jersey Knitted Fabrics

by Leon Pauly, Lukas Maier, Sibylle Schmied, Albrecht Dinkelmann, Ulrich Nieken and Götz T. Gresser

Fibers 2025, 13(4), 48; https://doi.org/10.3390/fib13040048 - 16 Apr 2025

Abstract

Pore sizes on the micrometre scale are a critical factor influencing the fluid transport properties of textiles. Consequently, the pore size distribution function is a desirable parameter in the design of textiles for technical applications. However, the experimental determination of pore size and [...] Read more.

Pore sizes on the micrometre scale are a critical factor influencing the fluid transport properties of textiles. Consequently, the pore size distribution function is a desirable parameter in the design of textiles for technical applications. However, the experimental determination of pore size and its distribution can be challenging, costly, or impractical. Knitted fabrics offer a wide range of porosity and pore size distribution properties. While statistical models have shown reasonable accuracy in predicting pore size distributions in nonwovens and filter media, no equivalent model exists for twist-texturized yarns and single-jersey knitted fabrics. This study presents a hierarchical pore model for single-jersey fabrics. The model uses a log-normal distribution for the intra-yarn pores in the yarn and cylindrical pores for inter-yarn pores between the yarns in the fabric. With these two pore sizes, the model quantitatively characterises the porous structure of the fabric. Initial validation of the model for intra-yarn pores on four yarns of different fibre finenesses shows that the model can cover the influence of different fibre counts. For the validation on the fabric scale, two tomography datasets of single-jersey knitted fabrics show that the presented model can capture the effect of different fabric structures. A parameter study visualises the effects of both yarn and knitting parameters on the pore size distribution function of single-jersey knitted fabrics. The mean pore sizes of the fabrics are given. The results deepen the understanding of the porous properties of knitted fabrics and provide a valuable direction for structural fabric development on knitting machines. Full article

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