Fibers

16 pages, 2639 KB

Open AccessArticle

Aging Effects on Flexural Behavior of Glass Fiber-Reinforced Stone-Cork Composite Panels for External Facade Elements

by João Marques, Madalena Barata Garcia, Virgínia Infante, Pedro Miguel Amaral and Arménio Correia

Fibers 2025, 13(12), 167; https://doi.org/10.3390/fib13120167 - 18 Dec 2025

Viewed by 689

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. [...] Read more.

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. Full article

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16 pages, 1336 KB

Open AccessArticle

The Science of Laundering and Wear: Understanding Fiber Fragmentation from Secondhand Cotton Denim

by Amanda J. Thompson

Fibers 2025, 13(12), 166; https://doi.org/10.3390/fib13120166 - 11 Dec 2025

Cited by 2 | Viewed by 1752

Abstract

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. [...] Read more.

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). Full article

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20 pages, 6471 KB

Open AccessArticle

Assessing the Role of Recycled Tyre Polymer Fibres (RTPFs) on the Key Hydration Processes Governing Autogenous Shrinkage

by Katarina Didulica, Ana Baričević and Vesna Zalar Serjun

Fibers 2025, 13(12), 165; https://doi.org/10.3390/fib13120165 - 10 Dec 2025

Viewed by 1061

Abstract

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 (RTPF_d) [...] Read more.

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 (RTPF_d) and pre-wetted (RTPF_w) 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. 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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27 pages, 4878 KB

Open AccessArticle

Bond Stress Analysis Between High-Performance Steel Fiber Reinforced Mortar and Deformed Steel Bars Under Pull-Out Test

by Ramdane Sidali Amrouche, Samira Djaknoun, Messaoud Saidani, Zineb Abeoub and Giangiacomo Minak

Fibers 2025, 13(12), 164; https://doi.org/10.3390/fib13120164 - 5 Dec 2025

Viewed by 1064

Abstract

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 [...] Read more.

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. Full article

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21 pages, 7246 KB

Open AccessArticle

Recycling of Glass Fibers from Wind Turbine Blade Wastes via Chemical-Assisted Solvolysis

by Maria Modestou, Dionisis Semitekolos, Tao Liu, Christina Podara, Savvas Orfanidis, Ana Teresa Lima and Costas Charitidis

Fibers 2025, 13(12), 163; https://doi.org/10.3390/fib13120163 - 5 Dec 2025

Cited by 9 | Viewed by 2898

Abstract

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 [...] Read more.

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. Full article

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15 pages, 4638 KB

Open AccessArticle

Electrospun Carbon Fibers from Green Solvent-Fractionated Kraft Lignin

by Marta Goliszek-Chabros and Omid Hosseinaei

Fibers 2025, 13(12), 162; https://doi.org/10.3390/fib13120162 - 4 Dec 2025

Cited by 2 | Viewed by 1476

Abstract

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 [...] Read more.

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. Full article

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13 pages, 6272 KB

Open AccessArticle

Multilayer Electrospun Nanofibrous Membranes for Enhanced Heavy Metal Remediation

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

Fibers 2025, 13(12), 161; https://doi.org/10.3390/fib13120161 - 2 Dec 2025

Cited by 1 | Viewed by 1685

Abstract

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 [...] Read more.

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

{Cr}^{6 +}

and 78.98% for

{Cd}^{2 +}

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. Full article

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33 pages, 3464 KB

Open AccessArticle

Finite Element Models on Shear Behavior of Deep Beams Prepared Using Steel Fiber-Reinforced Recycled Coarse Aggregate Concrete

by Said Elkholy, Mohamed Salem and Ahmed Godat

Fibers 2025, 13(12), 160; https://doi.org/10.3390/fib13120160 - 26 Nov 2025

Cited by 1 | Viewed by 1013

Abstract

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. [...] Read more.

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. 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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14 pages, 1845 KB

Open AccessBrief Report

Natural Fiber Composites for Sustainable Model Rocketry: Bamboo and Jute as Alternatives to Fiberglass

by Lais Alves, Tabata Barreto, Nordine Leklou and Silvio de Barros

Fibers 2025, 13(12), 159; https://doi.org/10.3390/fib13120159 - 26 Nov 2025

Viewed by 1423

Abstract

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. [...] Read more.

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. Full article

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24 pages, 4452 KB

Open AccessArticle

Mechanical Characterization of Carbon Fibers and Their Interfaces Recycled Through Plasma-Assisted Solvolysis Under Different Processing Conditions

by Ilektra Tourkantoni, Konstantinos Tserpes, Dimitrios Marinis, Ergina Farsari and Eleftherios Amanatides

Fibers 2025, 13(12), 158; https://doi.org/10.3390/fib13120158 - 24 Nov 2025

Cited by 5 | Viewed by 1526

Abstract

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 [...] Read more.

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. Full article

(This article belongs to the Topic Advanced Carbon Fiber Reinforced Composite Materials, Volume II)

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28 pages, 8636 KB

Open AccessReview

Valorization of Natural Byproducts Through Additive Manufacturing for Ecologically Sustainable Composite Materials: A Literature Review

by Ioannis Filippos Kyriakidis, Anargiros Karelis, Nikolaos Kladovasilakis, Eleftheria Maria Pechlivani and Konstantinos Tsongas

Fibers 2025, 13(12), 157; https://doi.org/10.3390/fib13120157 - 24 Nov 2025

Viewed by 1268

Abstract

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 [...] Read more.

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. Full article

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Fibers, Volume 13, Issue 12 (December 2025) – 11 articles

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