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Fibers
Volume 13
Issue 1
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Fibers, Volume 13, Issue 1 (January 2025) – 10 articles

Cover Story (view full-size image): The silk industry generates a significative fraction of valuable waste, and it is responsible for pollution, carbon emissions and energy consumption. A switch towards more sustainable practices in line with circular economy principles must be sought. A possible field of application for silk waste fibers is the production of more sustainable and recyclable composite materials. To fully exploit the mechanical properties of silk and to achieve complete sustainability of the materials, nonwoven fabrics accompanied by thermoplastic matrices are the best candidates. A review explores the feasibility of this solution, covering silk properties and common industrial practices, state-of-the-art silk-based composite materials, and silk waste nonwovens, as well as the possibility of industrialization of the recycling routes. View this paper
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28 pages, 3967 KiB  
Article
Degradation of Interfacial Bond for FRPs Near-Surface Mounted to Concrete Under Fatigue: An Analytical Approach
by Xun Wang and Lijuan Cheng
Fibers 2025, 13(1), 9; https://doi.org/10.3390/fib13010009 - 15 Jan 2025
Viewed by 375
Abstract
In this study, an analytical model was developed for the local bond degradation behavior between a near-surface mounted (NSM) fiber-reinforced polymer (FRP) and concrete under fatigue loading. A trilinear local bond stress–slip relationship was adopted to characterize the fundamental bond behavior at the [...] Read more.
In this study, an analytical model was developed for the local bond degradation behavior between a near-surface mounted (NSM) fiber-reinforced polymer (FRP) and concrete under fatigue loading. A trilinear local bond stress–slip relationship was adopted to characterize the fundamental bond behavior at the FRP-epoxy-concrete interface at different stages of elastic, softening and debonding. A series of post-fatigue direct pull-out tests (DPTs) of NSM FRP-bonded concrete blocks was conducted to provide the local bond degradation laws for the analytical model. The bond region was discretized into finite elements to include the effect of bond degradation to different extents, and a closed-form solution was derived by virtue of appropriate boundary conditions in each fatigue cycle. The model is capable of predicting the FRP strain distribution, local bond stress distribution and relative slip development at a targeted number of fatigue cycles. The reliability of the analytical model was confirmed by experimental data, and its sensitivity to various parameters such as local bond strength, the residual bond strength ratio and Young’s modulus of FRP reinforcement was also assessed in this study. Full article
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26 pages, 10277 KiB  
Article
Rehabilitation and Strengthening of Damaged Reinforced Concrete Beams Using Carbon Fiber-Reinforced Polymer Laminates and High-Strength Concrete Integrating Recycled Tire Steel Fiber
by Hasan A. Alasmari, Ibrahim A. Sharaky, Ahmed S. Elamary and Ayman El-Zohairy
Fibers 2025, 13(1), 10; https://doi.org/10.3390/fib13010010 - 15 Jan 2025
Viewed by 496
Abstract
Currently, millions of tires are consumed annually, which necessitates the efficient disposal of these quantities of spent tires and the development of means to convert them into useful materials. This research deals with the effect of adding the steel fibers extracted from used [...] Read more.
Currently, millions of tires are consumed annually, which necessitates the efficient disposal of these quantities of spent tires and the development of means to convert them into useful materials. This research deals with the effect of adding the steel fibers extracted from used car tires (RSFs) to incorporate them as concrete components to obtain high-strength concrete (HSC). The HSC was used in this paper to strengthen the pre-damaged beams by jacking. In the first phase, twelve beams were subjected to an overload equal to 80% of their total expected bearing capacity to obtain damaged RC beams, while one beam was loaded to failure (reference beam, RB0). In the second phase, the damaged beams were strengthened with HSC jacketing integrating RSFs with three contents (0, 0.25, and 0.5%) or by HSC jacking and bonded CFRP laminates to the bottom surface of the jacket. Moreover, the Abaqus finite element (FE) program was implemented to simulate the upgraded damaged beams. The result ensured enhanced HSC compressive and tensile strengths by 11.6–14.4% and 11.6–20.9% as the RSF % increased from 0 to 0.25 and 0.5%, respectively. Using the HSC jacket with 0, 0.25, and 0.5% RSF to strengthen the RC-damaged beams increased the load capacity by 8.8, 14.5, and 20.1%, respectively compared to RB0. Furthermore, strengthening the damaged RC beams with both HSC jacket and CFRP laminates enhanced their load capacity by 41.9, 45.5, and 50.3% as the HSC integrated 0, 0.25, and 0.5% RSF, respectively, compared to RB0. Finally, the FE model could reveal several aspects related to the behavior of the damaged beams strengthened with jackets and CFRP laminates and the interaction between the different beam components. Full article
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21 pages, 9644 KiB  
Article
Ballistic Impact Study of an Aramid Fabric by Changing the Projectile Trajectory
by Larisa Titire and Cristian Muntenita
Fibers 2025, 13(1), 8; https://doi.org/10.3390/fib13010008 - 14 Jan 2025
Viewed by 463
Abstract
Personal protective systems widely use aramid textile fabrics, whether in soft or rigid form, to protect against various types of ballistic threats. Ballistic impact refers to a high-velocity impact caused by a thrusting source, often involving a low-mass object. To use these materials [...] Read more.
Personal protective systems widely use aramid textile fabrics, whether in soft or rigid form, to protect against various types of ballistic threats. Ballistic impact refers to a high-velocity impact caused by a thrusting source, often involving a low-mass object. To use these materials effectively in structural applications, it is crucial to have a thorough understanding of their ballistic behavior when subjected to high-velocity impact. Upon contact of the projectile with the ballistic material, complex ballistic penetration processes take place, which require a comprehensive and quantitative examination for a better understanding. This study aims to analyze the damage mechanism of aramid fabric by altering the projectile impact trajectory based on numerical simulations. We aim to obtain a thorough understanding of the behavior of the aramid fabric by performing numerical simulations and examining the penetration process in detail. The obtained results are analyzed based on the von Mises stress distribution (panel and projectile, projectile only, and main wires), projectile deformation, projectile velocity during ballistic impact, and based on photographs obtained during the impact. Full article
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24 pages, 21943 KiB  
Article
Strengthening Fire-Damaged Lightweight Concrete T-Beams Using Engineered Cementitious Composite with Basalt Fiber-Reinforced Polymer Grid
by Haider M. Al-Baghdadi and Mohammed M. Kadhum
Fibers 2025, 13(1), 7; https://doi.org/10.3390/fib13010007 - 13 Jan 2025
Viewed by 496
Abstract
Lightweight concrete (LWC) is a long-standing development in the area of construction materials. LWC has become increasingly important for sustainable construction due to its reduced susceptibility to cracking. However, when exposed to extreme temperatures during fires, LWC can lose its compressive strength and [...] Read more.
Lightweight concrete (LWC) is a long-standing development in the area of construction materials. LWC has become increasingly important for sustainable construction due to its reduced susceptibility to cracking. However, when exposed to extreme temperatures during fires, LWC can lose its compressive strength and ductility. This study investigates the performance of lightweight expanded clay aggregate (LECA) concrete T-beams exposed to elevated temperatures. The research also focuses on the use of an engineered cementitious composite with a basalt fiber-reinforced polymer grid (ECCBFG) as a rehabilitation method for fire-damaged T-beams. Key variables considered include the concrete cover thickness (20 and 30 mm), fire exposure duration (30 and 60 min), and thickness of the ECCBFG layer. Thermocouples were installed at various points within the beams to monitor the heat gradient across the cross-section. Fourteen concrete beam specimens were tested, including control beams, fire-damaged beams, and beams strengthened with the ECCBFG layer. Key performance parameters, such as the energy absorption, cracking load, ductility index, maximum load capacity, and corresponding displacement, were analyzed. The experimental results showed that the strengthened beams outperformed the fire-damaged beams, closely matching the performance of undamaged reference beams in most aspects, except energy absorption. The findings suggest that further research is needed to optimize certain performance indicators and address challenges in strengthening fire-damaged beams. Full article
(This article belongs to the Special Issue Recent Developments in Structural Applications of Fiber-Reinforced Concrete)
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20 pages, 5498 KiB  
Review
Potential Use of Silk Waste in Sustainable Thermoplastic Composite Material Applications: A Review
by Tommaso Pini, Matteo Sambucci and Marco Valente
Fibers 2025, 13(1), 6; https://doi.org/10.3390/fib13010006 - 13 Jan 2025
Viewed by 615
Abstract
Global warming and climate change demand rapid and swift action in terms of reducing resource consumption, gas emissions, and waste generation. The textile industry is responsible for a large share of global pollution; therefore, to define a route to tackle part of the [...] Read more.
Global warming and climate change demand rapid and swift action in terms of reducing resource consumption, gas emissions, and waste generation. The textile industry is responsible for a large share of global pollution; therefore, to define a route to tackle part of the issue, a literature review on the current state of research in the field of recycling silk waste was conducted. The methods used to recover, process, and characterize silk waste fibers were summarized. The aim of this work was to investigate the possible applications of recycled silk waste in the field of composite materials for load bearing applications. In this sense, some prominent studies in the field of silk-based composites were reported, favoring thermoplastic materials for sustainability reasons. Studies on nonwoven silk waste fabrics were covered as well, finding an abundance of results but no applications as a reinforcement for composite materials. In a circular economy approach, we believe that the combination of nonwoven silk waste fabrics, thermoplastic polymers, and possibly hybridization with other fibers from sustainable sources could be beneficial and could lead to green and high-performance products. The aim of this work was to summarize the information available so far and help define a route in that direction. Full article
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24 pages, 13018 KiB  
Article
Amplifying the Sensitivity of Electrospun Polyvinylidene Fluoride Piezoelectric Sensors Through Electrical Polarization Process for Low-Frequency Applications
by Asra Tariq, Amir H. Behravesh, Muhammad Tariq and Ghaus Rizvi
Fibers 2025, 13(1), 5; https://doi.org/10.3390/fib13010005 - 9 Jan 2025
Viewed by 487
Abstract
Piezoelectric sensors convert mechanical stress into electrical charge via the piezoelectric effect, and when fabricated as fibers, they offer flexibility, lightweight properties, and adaptability to complex shapes for self-powered wearable sensors. Polyvinylidene fluoride (PVDF) nanofibers have garnered significant interest due to their potential [...] Read more.
Piezoelectric sensors convert mechanical stress into electrical charge via the piezoelectric effect, and when fabricated as fibers, they offer flexibility, lightweight properties, and adaptability to complex shapes for self-powered wearable sensors. Polyvinylidene fluoride (PVDF) nanofibers have garnered significant interest due to their potential applications in various fields, including sensors, actuators, and energy-harvesting devices. Achieving optimal piezoelectric properties in PVDF nanofibers requires the careful optimization of polarization. Applying a high electric field to PVDF chains can cause significant mechanical deformation due to electrostriction, leading to crack formation and fragmentation, particularly at the chain ends. Therefore, it is essential to explore methods for polarizing PVDF at the lowest possible voltage to prevent structural damage. In this study, a Design of Experiments (DoE) approach was employed to systematically optimize the polarization parameters using a definitive screening design. The main effects of the input parameters on piezoelectric properties were identified. Heat treatment and the electric field were significant factors affecting the sensor’s sensitivity and β-phase fraction. At the highest temperature of 120 °C and the maximum applied electric field of 3.5 kV/cm, the % β-phase (F(β)) exceeded 95%. However, when reducing the electric field to 1.5 kV/cm and 120 °C, the % F(β) ranged between 87.5% and 90%. The dielectric constant (ɛ′) of polarized PVDF was determined to be 30 at an electric field frequency of 1 Hz, compared to a value of 25 for non-polarized PVDF. The piezoelectric voltage coefficient (g33) for polarized PVDF was measured at 32 mV·m/N at 1 Hz, whereas non-polarized PVDF exhibited a value of 3.4 mV·m/N. The findings indicate that, in addition to a high density of β-phase dipoles, the polarization of these dipoles significantly enhances the sensitivity of the PVDF nanofiber mat. Full article
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17 pages, 6537 KiB  
Article
Development of Acoustic Insulating Carpets from Milkweed Fibers Using Air-Laid Spike Process
by Deborah Lupescu, Mathieu Robert and Said Elkoun
Fibers 2025, 13(1), 4; https://doi.org/10.3390/fib13010004 - 7 Jan 2025
Viewed by 482
Abstract
Fibers from milkweed, which grows in Quebec (Canada), offer a distinct and outstanding advantage compared to other natural fibers: their ultra-lightweight hollow structure provides excellent acoustic and thermal insulation properties for the automobile industry. To highlight the properties of milkweed fibers and reduce [...] Read more.
Fibers from milkweed, which grows in Quebec (Canada), offer a distinct and outstanding advantage compared to other natural fibers: their ultra-lightweight hollow structure provides excellent acoustic and thermal insulation properties for the automobile industry. To highlight the properties of milkweed fibers and reduce the use of synthetic materials in vehicles, nonwoven carpeting made from a blend of milkweed fibers and polylactic acid (PLA) fibers was produced using the air-laid process. Some of the nonwovens were compressed to investigate the effects of increased mass per unit area on their thermal, acoustic, and mechanical properties. The nonwovens’ mass per unit area, thermal insulation, sound absorption coefficient, airflow resistivity, compression, and resistance to moisture were evaluated and compared to other carpets made of natural and synthetic fibers. The findings indicate that milkweed and PLA carpets have lower thermal conductivity values of 37.45 (mW/m·K), (mW/m·K) less than carpets made from cotton and polypropylene. At low frequencies, none of the carpets absorbed sound. At high frequencies, milkweed and PLA carpets showed sound absorption values of at least 0.6, which provide better acoustic insulation than nonwoven materials made from jute and polyethylene (PE) fibers. Milkweed and PLA carpets exhibited better compression values than polypropylene (PP) carpets. Full article
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21 pages, 3266 KiB  
Review
Recovery of N-Methylmorpholine N-Oxide (NMMO) in Lyocell Fibre Manufacturing Process
by Maria Sawiak, Bernardo A. Souto, Lelia Lawson, Joy Lo and Patricia I. Dolez
Fibers 2025, 13(1), 3; https://doi.org/10.3390/fib13010003 - 6 Jan 2025
Viewed by 1125
Abstract
The lyocell process offers an environmentally friendly strategy to produce regenerated cellulose fibre from biomass. However, it is critical to recover and reuse the N-methyl-morpholine-N-oxide (NMMO) solvent to maximize the environmental benefits and lower the cost. This article reviews NMMO [...] Read more.
The lyocell process offers an environmentally friendly strategy to produce regenerated cellulose fibre from biomass. However, it is critical to recover and reuse the N-methyl-morpholine-N-oxide (NMMO) solvent to maximize the environmental benefits and lower the cost. This article reviews NMMO recovery and characterization techniques at the lab and industrial scales, and methods to limit the NMMO degradation during the process. The article also presents the results of a pilot study investigating the recovery of NMMO from lyocell manmade cellulosic fibre (L-MMCF) manufacturing wastewater. The work described includes the development of a calibration curve for the determination of NMMO content in aqueous solutions using Fourier Transform Infrared Spectroscopy (FTIR). Successful NMMO recovery from the wastewater was achieved using a rotary evaporator: the final NMMO concentration was 50, i.e., ready for use in the lyocell process, and no NMMO degradation was observed. The knowledge in this paper will support advances in L-MMCF manufacturing and the reduction in textile environmental footprint. Full article
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17 pages, 3333 KiB  
Article
Evaluation of Alpaca Yarns Dyed with Buddleja Coriaceous Dye and Metallic Mordants
by Arturo Quispe-Quispe, Franklin Lozano, Luz María Pinche-Gonzales and Fulgencio Vilcanqui-Perez
Fibers 2025, 13(1), 2; https://doi.org/10.3390/fib13010002 - 28 Dec 2024
Viewed by 680
Abstract
The objective of this research was to evaluate the effect of dye obtained from Buddleja coriacea and metallic mordants on the chromatic properties, textile characteristics, spectral profiles, and color stability in alpaca fibers. The dye extraction technique involved boiling in an aqueous solution, [...] Read more.
The objective of this research was to evaluate the effect of dye obtained from Buddleja coriacea and metallic mordants on the chromatic properties, textile characteristics, spectral profiles, and color stability in alpaca fibers. The dye extraction technique involved boiling in an aqueous solution, followed by filtration. Subsequently, alpaca yarns were dyed using the resulting extract following a standard protocol. The applied mordants included sodium sulfate (Na2SO4), aluminum sulfate and potassium dodecahydrate (KAl(SO4)2·12H2O), and oxalic acid (C2H2O4). Spectroscopy UV-Vis and FTIR spectrophotometry methods were used for the characterization of the dyed samples and analysis of the dye during the dyeing process. The findings revealed the formation of four distinct color tones. Additionally, it was determined that the mordants influenced the chromatic properties of the fibers dyed with Buddleja coriacea extract without modifying their textile characteristics. The identified spectral bands corresponded to keratin, the structural protein of the fibers. Changes in the intensity of these spectral bands were observed in the dyed samples, attributable to the presence of different mordants. Wet rub fastness was found to be inferior to dry rub fastness, which has implications for textile maintenance. In conclusion, Buddleja coriacea flowers provide an effective yellow dye, and when combined with various mordants, they allow for a variety of shades and hues in alpaca fiber yarns. Full article
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20 pages, 5177 KiB  
Article
The Influence of In Vitro Degradation on the Properties of Polylactic Acid Electrospun Fiber Mats
by Kardo Khalid Abdullah and Kolos Molnár
Fibers 2025, 13(1), 1; https://doi.org/10.3390/fib13010001 - 28 Dec 2024
Viewed by 616
Abstract
The scope of our study was to investigate the changes in electrospun polylactic acid (PLA) fiber mats’ morphological, mechanical, and thermal properties in vitro. We electrospun two sets of PLA fiber mats with different average diameters, E6 (747 nm) and E10 (1263 nm). [...] Read more.
The scope of our study was to investigate the changes in electrospun polylactic acid (PLA) fiber mats’ morphological, mechanical, and thermal properties in vitro. We electrospun two sets of PLA fiber mats with different average diameters, E6 (747 nm) and E10 (1263 nm). The degradation study of PLA electrospun fibers was carried out in phosphate-buffered saline solution at 37 °C to simulate conditions within the human system. The results reveal the thicker fibers (E10) degraded more rapidly than the E6 sample due to their different morphology. E10 showed a 29% reduction in diameter and a 41% weight loss, while E6 exhibited an 18% reduction in diameter and a 27.5% weight loss. E6’s Young’s modulus increased by 3.55 times, while E10’s rose by 2.23 times after 28 days of degradation, and the fibers became more rigid. E6 showed a more pronounced decrease in crystallinity compared with E10. Changes in electrospun fiber diameters and crystallinity greatly influence the degradation mechanism of PLA. Full article
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