Fibers

18 pages, 2909 KiB

Open AccessArticle

Recycling Particleboard by Acid Hydrolysis: Effects on the Physical, Thermal, and Chemical Characteristics of Recycled Wood Particles

by Gustavo E. Rodríguez, Rosilei Garcia and Alain Cloutier

Fibers 2025, 13(7), 90; https://doi.org/10.3390/fib13070090 - 2 Jul 2025

Abstract

Acid hydrolysis can be more efficient than water hydrolysis, particularly in breaking down cured adhesives found in waste panels within a shorter reaction time, which could benefit large-scale industrial processes. This study evaluates the effects of various acid hydrolysis conditions on the thermal, [...] Read more.

Acid hydrolysis can be more efficient than water hydrolysis, particularly in breaking down cured adhesives found in waste panels within a shorter reaction time, which could benefit large-scale industrial processes. This study evaluates the effects of various acid hydrolysis conditions on the thermal, physical, and chemical properties of recycled particles intended for particleboard production. Particleboards were recycled using oxalic acid and ammonium chloride at different concentrations and reaction times at 122 °C. The thermal stability of the particles was determined by thermogravimetric analysis. Particle size distribution, particle morphology, nitrogen content, pH and acid/base buffer capacity were analyzed. The effect of the recycled particles on the urea-formaldehyde (UF) curing was assessed using differential scanning calorimetry and the gel time method. The recycled particles exhibited a higher thermal degradation beyond 200 °C, indicating their thermal stability for manufacturing new panels. The acid treatments did not damage the anatomical structure of the particles, preserving the prosenchymatous elements. The nitrogen content of recycled particles decreased by up to 90% when oxalic acid was used, compared to raw board particles. Recycled particles exhibited a lower pH, with a maximum reduction of 44%. They also showed a decreased acid buffer capacity and an increased base buffer capacity compared to raw board particles. This effect was particularly pronounced in treatments that included ammonium chloride. The recycled particles did not significantly affect the peak polymerization temperature of the UF adhesive. However, some treatments affected the gel time of the adhesive, particularly those using 30% ammonium chloride. The results indicate that particleboards can be effectively recycled through acid hydrolysis, mainly with oxalic acid, which provides better results than hydrolysis using water alone. Oxalic acid showed increased selectivity in eliminating the cured UF adhesive, resulting in recycled particles suitable for manufacturing new panels. Full article

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20 pages, 5421 KiB

Open AccessArticle

Influence of Encapsulation Size and Textile Integration Techniques on the Wash Durability of Textiles with Integrated Electronic Yarn

by Arash M. Shahidi, Parvin Ebrahimi, Kalana Marasinghe, Tharushi Peiris, Zahra Rahemtulla, Carlos Oliveira, Dominic Eberl-Craske, Tilak Dias and Theo Hughes-Riley

Fibers 2025, 13(7), 89; https://doi.org/10.3390/fib13070089 - 2 Jul 2025

Abstract

A crucial factor when developing e-textiles is ensuring their robustness and functionality during everyday activities, particularly washing. The ability to launder e-textile garments is not merely a matter of convenience but a necessity for widespread adoption. Incorporating electronics into textiles can lead to [...] Read more.

A crucial factor when developing e-textiles is ensuring their robustness and functionality during everyday activities, particularly washing. The ability to launder e-textile garments is not merely a matter of convenience but a necessity for widespread adoption. Incorporating electronics into textiles can lead to damage due to mechanical and chemical stresses, which most electronics are not designed to withstand. This work focuses on electronic yarn technology (e-yarn), in which electronic functionality is added to textiles by embedding small electronic components into a flexible yarn-like structure. First, the component is soldered onto thin conductive wires. The soldered component is then enclosed in a protective polymer resin (micro-pod). Micro-pods have different diameters depending on the size of the embedded electronic component. The ensemble is finally covered in a textile sheath. This study focuses on the wash durability of e-yarns integrated with textiles in three different ways: embroidered onto the surface of a woven fabric, within a knitted channel in a knitted fabric, and woven as a weft yarn. Further, the work studied the impact of using different sizes of micro-pods on the e-yarns’ wash durability. Ultimately, good wash durability was observed under all testing conditions. Full article

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19 pages, 1844 KiB

Open AccessArticle

Embedding 1D Euler Beam in 2D Classical Continua

by Armine Ulukhanyan, Luca Placidi, Anil Misra, Roberto Fedele, Raimondo Luciano and Francesco Fabbrocino

Fibers 2025, 13(7), 88; https://doi.org/10.3390/fib13070088 - 1 Jul 2025

Abstract

In this contribution, the classical Cauchy first-gradient elastic theory is used to solve the equilibrium problem of a bidimensional (2D) reinforced elastic structure under small displacements and strains. Such a 2D first-gradient continuum is embedded with a reinforcement, which is modeled as a [...] Read more.

In this contribution, the classical Cauchy first-gradient elastic theory is used to solve the equilibrium problem of a bidimensional (2D) reinforced elastic structure under small displacements and strains. Such a 2D first-gradient continuum is embedded with a reinforcement, which is modeled as a zero-thickness interface endowed with the elastic properties of an extensional Euler–Bernoulli 1D beam. Modeling the reinforcement as an interface eliminates the need for a full geometric representation of the reinforcing bar with finite thickness in the 2D model, and the associated mesh discretization for numerical analysis. Thus, the effects of the 1D beam-like reinforcements are described through proper and generalized boundary conditions prescribed to contiguous continuum regions, deduced from a standard variational approach. The novelty of this work lies in the formulation of an interface model coupling 1D and 2D continua, based on weak formulation and variational derivation, capable of accurately capturing stress distributions without requiring full geometric resolution of the reinforcement. The proposed framework is therefore illustrated by computing, with finite element simulations, the response of the reinforced structural element under uniform bending. Numerical results reveal the presence of jumps for some stress components in the vicinity of the reinforcement tips and demonstrate convergence under mesh refinement. Although the reinforcement beams possess only axial stiffness, they significantly influence the equilibrium configuration by causing a redistribution of stress and enhancing stress transfer throughout the structure. These findings offer a new perspective on the effective modeling of fiber-reinforced structures, which are of significant interest in engineering applications such as micropiles in foundations, fiber-reinforced concrete, and advanced composite materials. In these systems, stress localization and stability play a critical role. Full article

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16 pages, 2046 KiB

Open AccessArticle

Physical and Mechanical Characterization of Flax Fibers: From Elementary Fiber to Yarn

by Wafa Mahjoub and Omar Harzallah

Fibers 2025, 13(7), 87; https://doi.org/10.3390/fib13070087 - 30 Jun 2025

Abstract

This study presents a multiscale characterization of flax fibers, from elementary fibers to technical bundles and yarns, to elucidate how fiber scale attributes influence yarn mechanics. Four yarn counts (111.11 tex, 100 tex, 90.9 tex, and 83.33 tex) were produced via dry spinning, [...] Read more.

This study presents a multiscale characterization of flax fibers, from elementary fibers to technical bundles and yarns, to elucidate how fiber scale attributes influence yarn mechanics. Four yarn counts (111.11 tex, 100 tex, 90.9 tex, and 83.33 tex) were produced via dry spinning, and tensile testing performed at each structural level. The results revealed a progressive decline in a specific modulus from elementary fibers (1.09 ± 0.62 N/tex) to short bundles (14.41 ± 9.59 N/tex), primarily due to fiber misalignment. Post hoc analysis confirmed that finer yarns (83.33 tex) exhibited higher stiffness (7.32 ± 1.69 N/tex, p < 0.001), attributed to advanced processing (GN4 combing). These findings highlight the critical role of fiber length and alignment in optimizing flax yarns for high-performance textiles. Full article

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23 pages, 9679 KiB

Open AccessArticle

Structure and Crystallization of Even–Odd Nylons Derived from Pimelic Acid: Influence of the Number of Methylene Groups in the Diamine Unit

by Matteo Arioli, Lourdes Franco and Jordi Puiggalí

Fibers 2025, 13(7), 86; https://doi.org/10.3390/fib13070086 - 27 Jun 2025

Abstract

Nylons 6,7, 8,7 and 10,7 have been synthesized by interfacial polycondensation and characterized. Thermal properties and thermally induced structural transitions have been evaluated to complement the reported data on nylon 4,7. Therefore, the complete even–odd series derived from pimelic acid is here fully [...] Read more.

Nylons 6,7, 8,7 and 10,7 have been synthesized by interfacial polycondensation and characterized. Thermal properties and thermally induced structural transitions have been evaluated to complement the reported data on nylon 4,7. Therefore, the complete even–odd series derived from pimelic acid is here fully characterized, in order to insist on their peculiar structural polymorphism. Real-time WAXD synchrotron experiments were conducted during heating, cooling and reheating processes. Basically, three structures were involved: a modified α-form, a distorted pseudohexagonal form and a pseudohexagonal form. The modified α-form was stable up to relatively low temperatures (i.e., lower than 140 °C), was mainly produced by solution crystallization and was progressively disfavored when the number of methylene groups of the diamine moiety increased. A progressive transition from the modified α-form to the distorted pseudohexagonal structure was observed during heating. Also, a continuous reverse transition was detected on cooling, although the yield on the modified α-form was low. A Brill transition towards a pseudohexagonal structure was observed in all cases. This transition was reversible, although with some hysteresis degree. Oriented fiber patterns corresponding to the distorted pseudohexagonal structure were obtained by melt stretching. In all cases, the 00l reflections appeared with a meridional orientation and indicated a shortening close to 0.05 nm/amide group with respect to the expected values for fully extended conformations. Full article

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11 pages, 2369 KiB

Open AccessArticle

The Effect of a Carbon Fiber Layer Between the Cathode and the Current Collector on Battery Cell Performance

by Jaswinder Sharma, Runming Tao, Georgios Polizos, Ruhul Amin, Yue Feng, Junbin Choi, M. Shahriar and Jianlin Li

Fibers 2025, 13(7), 85; https://doi.org/10.3390/fib13070085 - 27 Jun 2025

Abstract

Contact resistance between the cathode active material (CAM) and the Al current collector can be reduced by applying carbon coatings to the Al current collector surface. However, this process requires an additional step of carbon layer coating on the current collector, which increases [...] Read more.

Contact resistance between the cathode active material (CAM) and the Al current collector can be reduced by applying carbon coatings to the Al current collector surface. However, this process requires an additional step of carbon layer coating on the current collector, which increases both manufacturing costs and processing time. In the present work, an interlayer of continuous unsized carbon fibers aligned in one direction (CF interlayer), is introduced between the Al current collector and the NMC811 cathode during cathode deposition on the Al current collector. This single-step approach eliminates the need for the additional carbon layer coating on the current collector. Additionally, this approach removes the use of toxic solvents and insulative polymers used for making the carbon coating. The CF interlayer improves the rate capability at higher C-rates. The CF interlayer lowers the contact resistance between the cathode particles and the current collector while improving the activation energy of charge transfer. The peel test showed that the CF interlayer does not affect the adhesion strength of the cathode layer with the current collector. Full article

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Graphical abstract

35 pages, 10135 KiB

Open AccessArticle

Constitutive Model for Plain and Steel-Fibre-Reinforced Lightweight Aggregate Concrete Under Direct Tension and Pull-Out

by Hasanain K. Al-Naimi and Ali A. Abbas

Fibers 2025, 13(7), 84; https://doi.org/10.3390/fib13070084 - 23 Jun 2025

Abstract

In the present study, a programme of experimental investigations was carried out to examine the direct uniaxial tensile (and pull-out) behaviour of plain and fibre-reinforced lightweight aggregate concrete. The lightweight aggregates were recycled from fly ash waste, also known as Pulverised Fuel Ash [...] Read more.

In the present study, a programme of experimental investigations was carried out to examine the direct uniaxial tensile (and pull-out) behaviour of plain and fibre-reinforced lightweight aggregate concrete. The lightweight aggregates were recycled from fly ash waste, also known as Pulverised Fuel Ash (PFA), which is a by-product of coal-fired electricity power stations. Steel fibres were used with different aspect ratios and hooked ends with single, double and triple bends corresponding to 3D, 4D and 5D types of DRAMIX steel fibres, respectively. Key parameters such as the concrete compressive strength f_lck, fibre volume fraction V_f, number of bends n_b, embedded length L_E and inclination angle ϴ_f were considered. The fibres were added at volume fractions V_f of 1% and 2% to cover the practical range, and a direct tensile test was carried out using a purpose-built pull-out test developed as part of the present study. Thus, the tensile mechanical properties were established, and a generic constitutive tensile stress–crack width σ-ω model for both plain and fibrous lightweight concrete was created and validated against experimental data from the present study and from previous research found in the literature (including RILEM uniaxial tests) involving different types of lightweight aggregates, concrete strengths and steel fibres. It was concluded that the higher the number of bends n_b and the higher the volume fraction V_f and concrete strength f_lck, the stronger the fibre–matrix interfacial bond and thus the more pronounced the enhancement provided by the fibres to the uniaxial tensile residual strength and ductility in the form of work and fracture energy. A fibre optimisation study was also carried out, and design recommendations are provided. Full article

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45 pages, 2664 KiB

Open AccessReview

Converging Electrospinning and 3D-Printing Technologies: From Innovative Design for Tissue Engineering to Global Patent Trends and Technology Transfer

by Karen J. Juarez-Navarro, Vincenzo Guarino and Marco A. Alvarez-Perez

Fibers 2025, 13(6), 83; https://doi.org/10.3390/fib13060083 - 19 Jun 2025

Abstract

Electrospinning is a technique that enables the production of nano- and microfibrillar patterns that mimic the native extracellular matrix. However, these nanofibrous structures often lack mechanical properties suitable for reproducing the behavior of structurally complex tissues. Therefore, achieving more accurate and precise geometric [...] Read more.

Electrospinning is a technique that enables the production of nano- and microfibrillar patterns that mimic the native extracellular matrix. However, these nanofibrous structures often lack mechanical properties suitable for reproducing the behavior of structurally complex tissues. Therefore, achieving more accurate and precise geometric structures be-comes a key challenge. In this context, additive manufacturing techniques such as 3D printing may allow for the development of tailored structures with highly controlled ar-chitecture and improved mechanical strength. However, in contrast with electrospinning, these techniques are commonly considered “low-resolution” techniques, unable to ma-nipulate structural details at the submicrometric scale. Hence, this review aims to intro-duce and discuss recent technological approaches based on combining these technologies for scaffold development in tissue engineering, detailing some distinct integration strate-gies correlating the outcomes to the benefits and drawbacks. Finally, a comprehensive analysis of the current state of the art in the registered intellectual property related to these integrated approaches will be proposed, assessing their distribution by geographic region and analyzing the main trends over time and future fallouts. Full article

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11 pages, 1050 KiB

Open AccessArticle

Optimization of Process of Dyeing Alpaca Yarn Using Indigo Carmine (C.I. Natural Blue 2)

by Cristina M. Luque-Jacobo, Elizabeth Medrano de Jara, Jose Carrasco Bocangel and Edgar García-Hernández

Fibers 2025, 13(6), 82; https://doi.org/10.3390/fib13060082 - 18 Jun 2025

Abstract

As part of an implementation in the Peruvian textile industry, the use of different sources to obtain blue hues in alpaca fiber has taken on a prominent role. The present study investigated the optimization of the dyeing process of alpaca fibers using indigo [...] Read more.

As part of an implementation in the Peruvian textile industry, the use of different sources to obtain blue hues in alpaca fiber has taken on a prominent role. The present study investigated the optimization of the dyeing process of alpaca fibers using indigo carmine as dye. The methodology was based on a central composite design (CCD) and response surface methodology (RSM) with color strength (K/S) as response variable. The results demonstrate that the independent variables significantly affected the color strength (K/S). In this context, an increase in both mordant concentration (3.9887 g/L) and dyeing temperature (95 °C), coupled with lower exhaust time (30.0019 min), enhanced levels of superficial dye adsorption. Additionally, color fastness properties provided tolerable values according to the gray scale. In conclusion, the optimization of the dyeing process of alpaca fibers using indigo carmine enabled the achievement of a blue shade with satisfactory fastness properties in the fiber yarns. Full article

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24 pages, 2772 KiB

Open AccessArticle

Harnessing the Unique Nature of Evanescent Waves: Optimizing FOEW LSPR Sensors with Absorption-Focused Nanoparticle Design

by Omar Awad, AbdulRahman Ghannoum and Patricia Nieva

Fibers 2025, 13(6), 81; https://doi.org/10.3390/fib13060081 - 17 Jun 2025

Abstract

This work presents a novel and comprehensive framework for optimizing fiber optic evanescent wave (FOEW) localized surface plasmon resonance (LSPR) sensors by investigating the unique interaction between evanescent waves and plasmonic nanoparticles. Unlike propagating light, the evanescent wave is a localized, non-propagating field [...] Read more.

This work presents a novel and comprehensive framework for optimizing fiber optic evanescent wave (FOEW) localized surface plasmon resonance (LSPR) sensors by investigating the unique interaction between evanescent waves and plasmonic nanoparticles. Unlike propagating light, the evanescent wave is a localized, non-propagating field that interacts exclusively with absorbing media near the fiber surface. This characteristic highlights the importance of prioritizing nanoparticle absorption over total extinction in FOEW sensor design. The optical response of silver nanoparticles was modeled across a size range of 10–100 nm, showing that absorption increases with particle number. Among the sizes tested, 30 nm silver nanoparticles exhibited the highest absorption efficiency, which was confirmed experimentally. An analytical adsorption kinetics model based on diffusion transport further predicted that smaller nanoparticles yield higher surface coverage, a result validated through atomic force microscopy (AFM) and scanning electron microscopy (SEM) imaging. Refractive index (RI) sensitivity tests conducted on sensors fabricated with 10 nm, 20 nm, and 30 nm silver nanoparticles revealed that while smaller nanoparticles produced higher initial absorption due to greater surface density, the 30 nm particles ultimately provided superior RI sensitivity due to their enhanced absorption efficiency. These findings underscore the significance of absorption-centered nanoparticle design in maximizing FOEW LSPR sensor performance. Full article

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22 pages, 5134 KiB

Open AccessArticle

Experimental Investigation of the Behaviour of Short-Span FRP-Reinforced Glulam Beams with Hoops and Tension Anchoring

by Herry Chen, Yannick Vetter, Catherine Shrimpton and Daniel Lacroix

Fibers 2025, 13(6), 80; https://doi.org/10.3390/fib13060080 - 17 Jun 2025

Abstract

Past research has shown that for short-span glulam beams reinforced with a simple tension GFRP fabric can lead to undesirable failure modes at the reinforcement termination point. An experimental programme aimed at investigating alternative reinforcement schemes comprising hoops and tension anchoring as an [...] Read more.

Past research has shown that for short-span glulam beams reinforced with a simple tension GFRP fabric can lead to undesirable failure modes at the reinforcement termination point. An experimental programme aimed at investigating alternative reinforcement schemes comprising hoops and tension anchoring as an alternative to fan-type anchorage and full-length confinement was undertaken. Sixteen GFRP-reinforced glulam beams were tested to failure under four-point bending. Overall, the hoops and tension anchoring prevented premature debonding and stress concentration failures observed in beams reinforced with simple tension reinforcement. Improvements in the stiffness and strength were generally observed for all configurations with the average failure strain being on average 1.16 times larger than the unreinforced specimens. While hoops prevented undesirable failure modes, it had limited improvements when using bidirectional fabrics for the hoops. Conversely, the configurations with tension anchoring using bidirectional fabrics only resulted in improved performance with some level of post-peak resistance compared to the unreinforced specimens and those reinforced with simple tension reinforcement. For short-span beams, or any FRP-reinforced glulam beams where flexure is not the dominant failure mode, more robust modelling techniques are required to properly capture the distribution of the reinforcement. Full article

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21 pages, 5667 KiB

Open AccessArticle

Optimising Mechanical Performance of Additive Manufactured Composites for Biomedical Applications

by Abdul Qadir, Amadi Gabriel Udu and Norman Osa-uwagboe

Fibers 2025, 13(6), 79; https://doi.org/10.3390/fib13060079 - 13 Jun 2025

Abstract

The mechanical properties of additive manufactured (AM) short-fibre reinforced polymer (SFRP) composites are significantly influenced by infill patterns, fibre orientation, and fibre-matrix interactions. While previous studies have explored the role of process parameters in optimising AM components, the impact of infill geometry on [...] Read more.

The mechanical properties of additive manufactured (AM) short-fibre reinforced polymer (SFRP) composites are significantly influenced by infill patterns, fibre orientation, and fibre-matrix interactions. While previous studies have explored the role of process parameters in optimising AM components, the impact of infill geometry on anisotropy and mechanical performance remains underexplored, particularly in the context of machine learning (ML). This study develops an ML-driven framework to predict the tensile and flexural properties of AM SFRP composites with different infill patterns, including triangular, hexagonal, and rectangular. AM structures were fabricated and subjected to tensile and flexural tests, with the data used to train ML models, including LightGBM, XGBoost, and artificial neural networks (ANN). The results showed that the triangular infill pattern had the highest tensile strength and stiffness, the hexagonal infill had the lowest flexural properties, and the rectangular infill exhibited performance levels that fell between those of the triangular and hexagonal patterns. The ML models demonstrated high prediction accuracy, with R-squared values exceeding 0.95. XGBoost performed best for predicting tensile properties of hexagonal infill, while ANN excelled with triangular and rectangular configurations. This study demonstrates the potential of machine learning to enhance the mechanical performance of additively manufactured SFRP composites by capturing the complex interplay between infill geometry and fibre-matrix interactions. Thus, providing additional data for the design of high-performance materials in applications such as biomedical devices. Full article

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12 pages, 1291 KiB

Open AccessArticle

Non-Destructive Condition and Damage Assessment of Historic Weighted Silk

by Marta Anghelone, Caroline Dalhed and Tanja Kimmel

Fibers 2025, 13(6), 78; https://doi.org/10.3390/fib13060078 - 10 Jun 2025

Abstract

Silk weighting is a process used to compensate for the weight loss caused by degumming, achieved by adding agents such as metallic salts to enhance the hand feel and appearance of the fibers. With the development of tin weighting procedures (ca. 1870s), the [...] Read more.

Silk weighting is a process used to compensate for the weight loss caused by degumming, achieved by adding agents such as metallic salts to enhance the hand feel and appearance of the fibers. With the development of tin weighting procedures (ca. 1870s), the production of weighted silk tremendously increased, as the fast decay of such fabrics was attributed to the process itself. The weighted silk was largely used for evening wear and high-fashion garments, many of which nowadays are stored in textile collections, and often characterized by poor conservation conditions. Within the present work, a multi-analytical and interdisciplinary non-destructive protocol was established for studying the finishing techniques, characterizing the materials as well as the state of preservation of historic tin-weighted silk. The protocol involves a visual and haptic approach typical of conservation professionals, as well as analytical investigations such as X-Ray Fluorescence analyses, 3D digital microscopy, Scanning Electron Microscopy with Energy Dispersive Spectroscopy, and Fourier-transform Infrared Spectroscopy (FTIR) in Attenuated Total Reflection. Elemental analyses are effective for studying the technology of production, while FTIR emerged as a powerful tool for assessing the condition, through the carbonyl and crystallinity indices. Full article

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Graphical abstract

19 pages, 7815 KiB

Open AccessArticle

Short-Beam Shear Fatigue Behavior on Unidirectional GLARE: Mean Shear Stress Effect, Scatter, and Anisotropy

by Douglas G. Caetano, Hector G. Kotik, Juan E. Perez Ipiña and Enrique M. Castrodeza

Fibers 2025, 13(6), 77; https://doi.org/10.3390/fib13060077 - 9 Jun 2025

Abstract

This paper investigates the effect of mean shear stress on short-beam shear fatigue in a GLARE 1-3/2 commercial fiber–metal laminate (FML). This study explores three shear stress ratios (

R_{τ}

0.1, 0.3, and 0.5) and two material orientations (longitudinal and transversal) under [...] Read more.

This paper investigates the effect of mean shear stress on short-beam shear fatigue in a GLARE 1-3/2 commercial fiber–metal laminate (FML). This study explores three shear stress ratios (

R_{τ}

0.1, 0.3, and 0.5) and two material orientations (longitudinal and transversal) under constant amplitude fatigue. Different stress levels for each

R_{τ}

value were explored to obtain failures between 10³ and 10⁶ load cycles. The experimental results reveal anisotropy, with transversal specimens exhibiting lower performance and increased scatter. The mean shear stress effect is discussed herein, with insights into the critical role of mean shear of fatigue performance.

R_{τ}

0.1 was the most severe condition and

R_{τ}

0.5 was the least severe. The

R_{τ}

0.3 condition produced steeper S-N curves, indicating that the combined effect of mean shear stress and shear stress amplitude led to a higher rate of damage accumulation. The fractographic analysis investigated the failure modes and confirmed the damage dominated by Mode II, supporting the test methodology employed. Full article

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20 pages, 8651 KiB

Open AccessArticle

Hierarchical Modeling of Archaeological and Modern Flax Fiber: From Micro- to Macroscale

by Vasuki Rajakumaran, Johnny Beaugrand, Alessia Melelli, Mario Scheel, Timm Weitkamp, Jonathan Perrin, Alain Bourmaud, Henry Proudhon and Sofiane Guessasma

Fibers 2025, 13(6), 76; https://doi.org/10.3390/fib13060076 - 9 Jun 2025

Abstract

Flax fiber reinforcements weaken with aging and microstructural changes, limiting their applications. Here, we examine the effects of microstructure and aging on flax fiber elements’ performance by using 4000-year-old and modern Egyptian flax as references through multi-scale numerical modeling. This study introduces a [...] Read more.

Flax fiber reinforcements weaken with aging and microstructural changes, limiting their applications. Here, we examine the effects of microstructure and aging on flax fiber elements’ performance by using 4000-year-old and modern Egyptian flax as references through multi-scale numerical modeling. This study introduces a novel investigation into the tensile stress distribution behavior of archaeological and modern flax yarns. The finite element (FE) model is derived from 3D volumes obtained via X-ray microtomography and tensile testing in the elastic domain. At the microscale, fibers exhibit higher axial stress concentrations around surface defects and pores, particularly in regions with kink bands and lumens. At the mesoscale, fiber bundles show increased stress concentrations at inter-fiber voids and lumen, with larger bundles exhibiting greater stress heterogeneity, especially around pores and surface roughness. At the macroscale, yarns display significant stress heterogeneity, especially around microstructural defects like pores and fiber–fiber cohesion points. Aged fibers from ancient Egyptian cultural heritage in particular demonstrate large fiber discontinuities due to long-term degradation or aging. These numerical observations highlight how porosity, surface imperfections, and structural degradation increase stress concentration, leading to fiber rupture and mechanical failure. This insight reveals how aging and defects impact flax fiber performance and durability. Full article

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21 pages, 6582 KiB

Open AccessArticle

Experimental Study on the Effect of Abaca Fibers on Reinforced Concrete: Evaluation of Workability, Mechanical, and Durability-Related Properties

by Armando Arvizu-Montes, Stefany Alcivar-Bastidas and María José Martínez-Echevarría

Fibers 2025, 13(6), 75; https://doi.org/10.3390/fib13060075 - 4 Jun 2025

Abstract

Interest in incorporating natural fibers as reinforcements in concrete has grown in parallel with the increasing need to reduce the environmental impact of construction. These fibers, known for their renewability, low cost, and life-cycle superiority, exhibit technical advantages such as light weight and [...] Read more.

Interest in incorporating natural fibers as reinforcements in concrete has grown in parallel with the increasing need to reduce the environmental impact of construction. These fibers, known for their renewability, low cost, and life-cycle superiority, exhibit technical advantages such as light weight and high tensile strength. This study experimentally evaluated the influence of abaca fibers (AF) previously subjected to alkaline treatment and incorporated in reinforced concrete on workability, mechanical behavior, and durability, with a particular focus on the mechanisms affecting steel rebar corrosion. The characterization techniques included compressive and flexural testing; porosity, capillary water absorption, ion chloride penetration, and carbonation depth measurements; and corrosion rate monitoring via electrochemical methods. The results indicated that the addition of AF did not compromise the fresh-state properties or compressive strength but improved the flexural strength by 7.3%. Regarding durability, the porosity and water absorption increased by 4.1% and 8.2%, respectively, whereas the chloride penetration and carbonation depth remained within the requirements. Notable effects were observed regarding steel corrosion performance, where the incorporation of AF led to higher variability and an increasing trend in the corrosion rate compared with that of the reference concrete. Nevertheless, estimations suggest that abaca-fiber-reinforced concrete can meet the 100-year service life. These findings support the potential of AF as a viable reinforcement material for mechanical improvement; however, their influence on long-term durability, particularly corrosion, requires further investigation to deepen their feasible application for sustainable construction. Full article

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13 pages, 2510 KiB

Open AccessArticle

Poly-D,L-Lactic Acid as a Compatibilizer for Nootkatone-Embedded Nylon 12 Fabric Manufacturing

by Javier Jimenez, Joseph A. Orlando, James E. Cilek and Jeffrey G. Lundin

Fibers 2025, 13(6), 74; https://doi.org/10.3390/fib13060074 - 4 Jun 2025

Abstract

Personal protection from mosquitos is dominated by topically applied aerosol sprays or lotions, which demonstrate efficacy durations of no longer than 10 h, thus encouraging the research and development of long-term insect-repelling devices. Repellent-loaded polymeric matrices have driven the development of insect-repelling apparel [...] Read more.

Personal protection from mosquitos is dominated by topically applied aerosol sprays or lotions, which demonstrate efficacy durations of no longer than 10 h, thus encouraging the research and development of long-term insect-repelling devices. Repellent-loaded polymeric matrices have driven the development of insect-repelling apparel fabrics; however, most efforts either fail to offer the tensile properties demanded from apparel applications or only demonstrate repellency durations for multiple days. This study utilizes poly-D,L-lactic acid (PDLLA) as a compatibilizer between Nylon 12 and nootkatone for enhanced nootkatone retention throughout fabric manufacturing processes. Nootkatone-infused Nylon 12/PDLLA composites demonstrate up to a 14% increase in nootkatone retention throughout fabric manufacturing compared to pure Nylon 12, underscoring the importance of polymer/substrate miscibility on substrate retention. Moreover, while nootkatone-infused Nylon 12 filaments demonstrate decreasing tensile stress at breaks with increasing nootkatone content, Nylon 12/PDLLA filaments exhibit similar tensile properties regardless of nootkatone content. The PDLLA domains are suspected to behave as reservoirs for excess nootkatone to prevent its role as a defect within the Nylon 12 matrix. The resulting knits exhibit significant mosquito repellencies over 24 h dependent on the nootkatone concentration, thus demonstrating potential to embed insect repellent within high-performance polymeric filaments with effective mosquito repellencies. Therefore, the incorporation of PDLLA as a compatibilizer holds significant potential for enhanced nootkatone retention during Nylon 12 fabric manufacturing. Full article

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Graphical abstract

25 pages, 3711 KiB

Open AccessArticle

Eco-Friendly Extraction of Curcumin from Turmeric and Dyeability of Textile Fibers

by Vasilica Popescu, Ana-Diana Alexandrescu, Gabriel Popescu and Viorica Vasilache

Fibers 2025, 13(6), 73; https://doi.org/10.3390/fib13060073 - 4 Jun 2025

Abstract

Classical and modern methods are used to release curcumin by degrading the polysaccharides found in the turmeric powder matrix. Classical methods use chemicals as acids (HCl, H₂SO₄, CH₃COOH), oxidants (H₂O₂, kojic acid), and [...] Read more.

Classical and modern methods are used to release curcumin by degrading the polysaccharides found in the turmeric powder matrix. Classical methods use chemicals as acids (HCl, H₂SO₄, CH₃COOH), oxidants (H₂O₂, kojic acid), and enzymes (amylase type) that can degrade amylose and amylopectin from starch. The modern applied methods consist of the degradation of the polysaccharides in the turmeric powder during eco-friendly processes assisted by ultrasound or microwaves. The extraction medium can consist of only water, water with a solvent, and/or an oxidizing agent. The presence of curcumin in turmeric powder is confirmed by FTIR analysis. The UV–VIS analysis of the extracts allows the determination of the efficiency of modern extraction processes. The release of curcumin from turmeric is highlighted quantitatively by colorimetric measurements for the obtained extracts, using a portable DataColor spectrophotometer. The comparison of the results leads to the conclusion that microwave-assisted extractions are the most effective. These extracts are able to dye many types of textile fibers: wool, cotton, hemp, silk, polyacrylonitrile, polyamide, polyester, and cellulose acetate. CIELab and color strength (K/S) measurements indicate that the most intense yellow colors are obtained on polyacrylonitrile (b* = 86.32, K/S = 15.14) and on cellulose acetate (b* = 90.40, K/S = 14.17). Full article

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22 pages, 1950 KiB

Open AccessArticle

Mechanical Properties and Structural Design of PVA Fiber-Reinforced Cementitious Composites with Fly Ash Replacement for Natural Sand Aggregates

by Camelia Maria Negrutiu, Pavel Ioan Sosa, Cristina Mihaela Campian and Maria Ileana Pop

Fibers 2025, 13(6), 72; https://doi.org/10.3390/fib13060072 - 3 Jun 2025

Abstract

This paper investigates nine PVA fiber-reinforced cementitious composites with varying fiber content (1–2.5%) and types (oil-coated and non-coated). The experimental compositions utilize locally available cement, high volumes of fly ash, silica fume, PVA fibers, and a superplasticizer, entirely omitting natural aggregates. Key parameters [...] Read more.

This paper investigates nine PVA fiber-reinforced cementitious composites with varying fiber content (1–2.5%) and types (oil-coated and non-coated). The experimental compositions utilize locally available cement, high volumes of fly ash, silica fume, PVA fibers, and a superplasticizer, entirely omitting natural aggregates. Key parameters evaluated include bulk density, compressive strength, secant modulus of elasticity, flexural tensile strength, fracture energy, and structural design applicability. The results show that FRCs without natural aggregates achieves significantly lower densities (1500–1720 kg/m³). Compressive strength is influenced by matrix density, with the highest value recorded at 30.98 MPa. The high fly ash content reduces the secant modulus of elasticity, while flexural tensile strength follows a similar pattern to compressive strength. Oil-coated fibers generally lower fracture energy, except for the 1.5% PVA content, where the 2.5% composition performs best. All specimens exhibit tension softening rather than the strain-hardening behavior of ECCs. Structural design equations were developed, though experimental validation is necessary. The 2.5% PVA composition increases the compression zone height by 7% while requiring 2% more reinforcement. As a sustainable alternative to conventional concrete, the composites offer promising mechanical properties and structural viability for construction applications. Full article

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