Fibers

11 pages, 1951 KiB

Open AccessEditor’s ChoiceArticle

Kinetic Analysis of Cement–Asbestos Materials’ Thermal Decomposition Process by an Ex Situ Technique

by Robert Kusiorowski, Anna Gerle and Magdalena Kujawa

Fibers 2025, 13(4), 43; https://doi.org/10.3390/fib13040043 - 10 Apr 2025

Cited by 1 | Viewed by 382

For many years, countries around the world have been struggling with the problem of storing asbestos waste, especially in, those countries where the production and use of asbestos products have been legally banned. Following the adoption of plans for cleaning up asbestos waste, [...] Read more.

For many years, countries around the world have been struggling with the problem of storing asbestos waste, especially in, those countries where the production and use of asbestos products have been legally banned. Following the adoption of plans for cleaning up asbestos waste, countries are struggling with the problem of its disposal, which mainly involves storing it in specialist landfills. At the same time, scientists are looking for alternatives to this type of “disposal” of asbestos by developing methods for degrading the harmful fibers. Particular attention has been paid to methods based on the thermal treatment of this waste, which results in hazardous asbestos fibers being thermally decomposed. This work focuses on the kinetic study of the thermal decomposition process of cement–asbestos using an exsitu thermal treatment. The results obtained made it possible to interpret this thermal transformation kinetically. Kinetic analysis of the isothermal data using an Avrami–Erofeev model yielded values for the overall reaction order. On this basis, the value of the apparent activation energy of the thermal decomposition process of the tested cement–asbestos samples was obtained, which was approximately 140–180 kJ mol⁻¹. Full article

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17 pages, 5419 KiB

Open AccessEditor’s ChoiceArticle

Fiber/Free-Space Optics with Open Radio Access Networks Supplements the Coverage of Millimeter-Wave Beamforming for Future 5G and 6G Communication

by Cheng-Kai Yao, Hsin-Piao Lin, Chiun-Lang Cheng, Ming-An Chung, Yu-Shian Lin, Wen-Bo Wu, Chun-Wei Chiang and Peng-Chun Peng

Fibers 2025, 13(4), 39; https://doi.org/10.3390/fib13040039 - 2 Apr 2025

Cited by 2 | Viewed by 684

Abstract

Conceptually, this paper aims to help reduce the communication blind spots originating from the design of millimeter-wave (mmW) beamforming by deploying radio units of an open radio access network (O-RAN) with free-space optics (FSOs) as the backhaul and the fiber-optic link as the [...] Read more.

Conceptually, this paper aims to help reduce the communication blind spots originating from the design of millimeter-wave (mmW) beamforming by deploying radio units of an open radio access network (O-RAN) with free-space optics (FSOs) as the backhaul and the fiber-optic link as the fronthaul. At frequencies exceeding 24 GHz, the transmission reach of 5G/6G beamforming is limited to a few hundred meters, and the periphery area of the sector operational range of beamforming introduces a communication blind spot. Using FSOs as the backhaul and a fiber-optic link as the fronthaul, O-RAN empowers the radio unit to extend over greater distances to supplement the communication range that mmW beamforming cannot adequately cover. Notably, O-RAN is a prime example of next-generation wireless networks renowned for their adaptability and open architecture to enhance the cost-effectiveness of this integration. A 200 meter-long FSO link for backhaul and a fiber-optic link of up to 10 km for fronthaul were erected, thereby enabling the reach of communication services from urban centers to suburban and remote rural areas. Furthermore, in the context of beamforming, reinforcement learning (RL) was employed to optimize the error vector magnitude (EVM) by dynamically adjusting the beamforming phase based on the communication user’s location. In summary, the integration of RL-based mmW beamforming with the proposed O-RAN communication setup is operational. It lends scalability and cost-effectiveness to current and future communication infrastructures in urban, peri-urban, and rural areas. Full article

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38 pages, 9959 KiB

Open AccessEditor’s ChoiceArticle

Application of Carbon-Fiber-Reinforced Polymer Rods and Ultra-High-Performance Fiber-Reinforced Concrete Jackets with Mechanical Anchorage Systems to Reinforced Concrete Slabs

by Firas Hassan Saeed and Farzad Hejazi

Fibers 2025, 13(3), 33; https://doi.org/10.3390/fib13030033 - 13 Mar 2025

Cited by 1 | Viewed by 881

Abstract

The aim of this experimental study was to develop and evaluate the effectiveness of a new strengthening system for reinforced concrete slabs employing external jackets consisting of ultra-high-performance fiber-reinforced-concrete (UHPFRC) and mechanical anchor systems. The issue of debonding between old and fresh concrete [...] Read more.

The aim of this experimental study was to develop and evaluate the effectiveness of a new strengthening system for reinforced concrete slabs employing external jackets consisting of ultra-high-performance fiber-reinforced-concrete (UHPFRC) and mechanical anchor systems. The issue of debonding between old and fresh concrete layers, as well as the efficiency of utilizing CFRP rods, is the primary challenge of applying the UHPFRC jackets with embedded CFRP rods. In this study, we propose a novel retrofitting technique for implementing a mechanical anchor system to improve the binding of fresh UHPFRC jackets with old RC slabs. An experimental test was conducted by subjecting three slabs to cyclic loads by utilizing a dynamic actuator: a reference slab, a retrofitted slab with an external UHPFRC layer, and a retrofitted slab with an external UHPFRC layer incorporating CFRP bars. Furthermore, finite element models (FEMs) were utilized to investigate the responses of the retrofitted slabs and compare the novel method with traditional strengthening techniques, including near-surface-mounted (NSM) CFRP rods, externally bonded CFRP strips, and epoxy-bonded UHPFRC jackets, as well as two models that were the same as the experimental strengthened slab specimens except for the fact that they did not have a mechanical anchor system. Additionally, analytical mechanistic models were employed to determine the flexural moment capacity of the RC slabs. The experimental findings demonstrated that the proposed strengthening strategy considerably prevented premature debonding and enhanced the maximum load of retrofitted RC slabs by over 82%. Also, the FEM and analytical results are significantly consistent with the experimental outcomes. In conclusion, the newly suggested strengthening technique is a reliable system for enhancing the efficacy of slabs, effectively preventing early debonding between existing and new components. Full article

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19 pages, 7052 KiB

Open AccessEditor’s ChoiceArticle

Experimental Study on the Valorization of Rice Straw as Fiber for Concrete

by Hesam Doostkami, David Hernández-Figueirido, Vicente Albero, Ana Piquer, Pedro Serna and Marta Roig-Flores

Fibers 2025, 13(3), 28; https://doi.org/10.3390/fib13030028 - 5 Mar 2025

Cited by 1 | Viewed by 1156

Abstract

Rice straw is an agricultural waste that is difficult to manage and has traditionally been burned or buried, leading to environmental problems. Because of this, the introduction of rice straw into concrete has been proposed to revalue this residue. This investigation shows experimental [...] Read more.

Rice straw is an agricultural waste that is difficult to manage and has traditionally been burned or buried, leading to environmental problems. Because of this, the introduction of rice straw into concrete has been proposed to revalue this residue. This investigation shows experimental work carried out to prepare rice straw fibers and introduce them into a concrete mix as macrofibers. In addition, three fiber treatments were compared: two alkaline and one thermal. Four concrete mixes were studied: a reference mix, two concrete mixes with untreated rice straw fibers in two dosages, 10 kg/m³ and 15 kg/m³, and a fourth concrete mix with 10 kg/m³ of fiber treated with sodium hydroxide. The properties analyzed are workability, compression flexural strength, and shrinkage. The results show that the rice straw fiber used in this work improves concrete flexural strength at the peak but does not provide post-crack residual flexural strength. The sodium hydroxide treatment was effective in obtaining a more cohesive mix and lower setting time delay and slightly improved the performance of the rice straw fiber at the flexural strength peak. In summary, concrete can be used to encapsulate this agricultural waste material, providing enough strength for several engineering applications (>30 MPa). Full article

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43 pages, 27240 KiB

Open AccessEditor’s ChoiceArticle

An Experimental Investigation on the Effect of Incorporating Natural Fibers on the Mechanical and Durability Properties of Concrete by Using Treated Hybrid Fiber-Reinforced Concrete Application

by Anteneh Geremew, Amelie Outtier, Pieter De Winne, Tamene Adugna Demissie and Hans De Backer

Fibers 2025, 13(3), 26; https://doi.org/10.3390/fib13030026 - 28 Feb 2025

Cited by 2 | Viewed by 2186

Abstract

This research explores the use of treated hybrid natural fibers—wheat straw and bamboo—as reinforcements in concrete for pavement applications. Motivated by environmental and economic benefits, the study investigates how these fibers can enhance the mechanical and durability properties of concrete. Wheat straw fibers, [...] Read more.

This research explores the use of treated hybrid natural fibers—wheat straw and bamboo—as reinforcements in concrete for pavement applications. Motivated by environmental and economic benefits, the study investigates how these fibers can enhance the mechanical and durability properties of concrete. Wheat straw fibers, abundant in Ethiopia due to extensive wheat farming, help control micro-cracks and increase the tensile strength of concrete, while bamboo fibers, also locally available, reduce macro-crack propagation and improve concrete toughness. To prepare these fibers, wheat straw was cut to 25 mm in length and bamboo fibers were treated with a 5% sodium hydroxide solution before being cut into lengths of 30, 45, and 60 mm. A concrete mix targeting a cube compressive strength of 30 MPa incorporated 0.1% wheat straw fibers, with varying bamboo fiber contents (0.5%, 1%, and 1.5%) by weight of cement. The results indicate that the uniquely treated hybrid natural fiber-reinforced concrete mix exhibits noticeable enhancements in mechanical properties, with approximate increases of 4.16%, 8.80%, and 8.93% at 7, 28, and 56 days, respectively. Furthermore, the split tensile strength, flexural strength, and durability properties of the concrete were significantly improved by the proposed fiber concentration and length compared to the control concrete mix design. This treatment also shifted the failure mode of the concrete from brittle to ductile and enhanced its energy absorption capacity up to 7.88% higher than that of the control concrete. Based on the AASHTO 1993 pavement design guidelines, this fiber-reinforced concrete reduces pavement thickness by 11% compared to the control concrete while improving post-cracking behavior. This hybrid natural fiber-reinforced concrete presents a promising, sustainable, and eco-friendly alternative for rigid pavement construction. Full article

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16 pages, 5390 KiB

Open AccessEditor’s ChoiceArticle

Flammability of Plant-Based Loose-Fill Thermal Insulation: Insights from Wheat Straw, Corn Stalk, and Water Reed

by Martins Andzs, Ramunas Tupciauskas, Andris Berzins, Gunars Pavlovics, Janis Rizikovs, Ulla Milbreta and Laura Andze

Fibers 2025, 13(3), 24; https://doi.org/10.3390/fib13030024 - 24 Feb 2025

Cited by 1 | Viewed by 994

Abstract

This study investigates the fire resistance capabilities of newly developed loose-fill thermal insulation materials crafted from annual plants such as wheat straw, corn stalk, and water reed. Three processing methodologies were employed: mechanical crushing (raw, size ≤ 20 mm), chemi-mechanical pulping (CMP) using [...] Read more.

This study investigates the fire resistance capabilities of newly developed loose-fill thermal insulation materials crafted from annual plants such as wheat straw, corn stalk, and water reed. Three processing methodologies were employed: mechanical crushing (raw, size ≤ 20 mm), chemi-mechanical pulping (CMP) using 4% sodium hydroxide, and steam explosion (SE). An admixture of boric acid (8%) and tetraborate (7%) was added to all treated materials to enhance fire retardancy. The fire reaction characteristics of the insulation materials were assessed using a cone calorimeter measuring the key parameters like time to ignition, total heat release, heat release rate, and total smoke production. The findings indicate that nearly all tested insulation samples, apart from the raw and SE water reed, demonstrated fire resistance comparable to commercial cellulose insulation, surpassing the fire performance of various synthetic foams and composite materials. Furthermore, the single-flame source fire tests indicated that the developed insulation materials achieved a fire classification E, except for the SE water reed sample. Thus, the fire performance results approve the suitability of developed plant-based insulation materials for competing materials in building constructions. Full article

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24 pages, 30156 KiB

Open AccessEditor’s ChoiceArticle

Chopped Basalt Fibers Reinforced Mortar for Strengthening the Architectural Heritage

by Micaela Mercuri, Marco Vailati and Amedeo Gregori

Fibers 2025, 13(2), 20; https://doi.org/10.3390/fib13020020 - 11 Feb 2025

Cited by 1 | Viewed by 1980

Abstract

The high seismic vulnerability of unreinforced masonry buildings urgently calls for researchers to develop sustainable reinforcing methods and materials. This paper presents an innovative lime-based mortar reinforced with randomly oriented basalt fibers for the reinforcement of masonry heritage. The main aim of this [...] Read more.

The high seismic vulnerability of unreinforced masonry buildings urgently calls for researchers to develop sustainable reinforcing methods and materials. This paper presents an innovative lime-based mortar reinforced with randomly oriented basalt fibers for the reinforcement of masonry heritage. The main aim of this study is to understand the effect of the content and the length of basalt fibers on the mortar’s mechanical behavior. As a cementitious material made mostly out of lime, the mortar is chemically compatible with the historical substrate and therefore suitable in cases of restoration works on architectural heritage. Moreover, the chopped basalt fibers are randomly oriented, and this characteristic makes the overall layer effective in all directions, as the state of stress induced by seismic action is directionally undetermined. The newly proposed reinforcement system is characterized by a twofold aspect related to sustainability: 30% of the aggregates composing the mortar mix design is a recycled result of the ruins of the 2009 L’Aquila earthquake, and the chopped fibers are made out of basalt, widely known for its environmentally supportable peculiarity. The study consists of testing samples characterized by two fiber lengths and six fiber contents, along with one set of plain mortar samples. Specimens measuring 160 mm × 40 mm × 40 mm are first tested in a three-point bending (TPB) configuration, aiming to determine the flexural strength and the post-peak capacity through the calculation of the fracture energy. Then, the two broken pieces resulting from the TPB tests, each measuring 80 mm × 40 mm × 40 mm, are tested in splitting and compression, respectively, aiming to compute the tensile and compressive strengths. Finally, to provide a trend for the mortar’s mechanical properties, a regression analysis is performed by fitting the experimental data with simple linear, polynomial, and exponential regression models. Results show that: (i) both fiber content and fiber length are responsible for a linear increase of the flexural strength and the fracture energy; (ii) for both short- and long-fiber mortar samples, the tensile strength and the compressive strength parabolically increase with the fiber content; (iii) the increase in fiber content and fiber length always generates a reduction in the conglomerate workability. The fiber content (FC) optimization with respect to the mechanical properties leads to a basalt FC equal to 1.2% for long-fiber samples and an FC equal to 1.9% for short-fiber ones. Full article

(This article belongs to the Special Issue Development of Eco-Friendly Concrete-, Mortar- and Fiber-Reinforced Composite Systems for Building Applications: Experimental and Theoretical Studies)

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31 pages, 6533 KiB

Open AccessEditor’s ChoiceArticle

Enhancing Interfacial Adhesion in Kevlar and Ultra-High Molecular Weight Polyethylene Fiber-Reinforced Laminates: A Comparative Study of Surface Roughening, Plasma Treatment, and Chemical Functionalization Using Graphene Nanoparticles

by Feyi Adekunle, Jan Genzer and Abdel-Fattah M. Seyam

Fibers 2025, 13(2), 19; https://doi.org/10.3390/fib13020019 - 11 Feb 2025

Cited by 1 | Viewed by 1232

Abstract

This study investigates the impact of mechanical and chemical surface treatments on the interfacial adhesion and mechanical properties of Kevlar and ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced laminates (FRLs). Various treatments, including surface roughening, plasma exposure, NaOH and silane coupling, and graphene nanoparticle [...] Read more.

This study investigates the impact of mechanical and chemical surface treatments on the interfacial adhesion and mechanical properties of Kevlar and ultra-high molecular weight polyethylene (UHMWPE) fiber-reinforced laminates (FRLs). Various treatments, including surface roughening, plasma exposure, NaOH and silane coupling, and graphene nanoparticle (NP) incorporation, were conducted to enhance the fiber–matrix bonding within thermoplastic polyurethane (TPU) and ethylene-vinyl acetate (EVA) matrices. Results demonstrated that treatment efficacy highly depends on fiber type and matrix material, with chemical modifications generally outperforming the physical treatment (surface roughness). Plasma treatment significantly enhanced adhesion for UHMWPE, increasing yarn pullout force by 188.1% with TPU. While combining plasma with graphene slightly improved performance, it did not exceed plasma-only results due to potential surface functionalization losses during wet graphene application. For Kevlar, the combination of NaOH, silane, and graphene NP (NSG) treatment yielded the highest adhesion, showing increases of 76.6% with TPU and 95.4% with EVA, underscoring the synergy between chemical coupling and nanomaterial reinforcement. This study’s insights align with previous research, expanding the knowledge base by investigating graphene’s role independently and alongside established methods. Full article

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28 pages, 5006 KiB

Open AccessEditor’s ChoiceArticle

Insights on Lattice Discrete Particle Model Calibration and Validation Procedure to Simulate Polypropylene and Steel Fibre-Reinforced Concrete

by Sushant Poudel, Antonio Cibelli, Clementina Del Prete, Roman Wan-Wendner, Claudio Mazzotti and Nicola Buratti

Fibers 2025, 13(2), 16; https://doi.org/10.3390/fib13020016 - 5 Feb 2025

Cited by 2 | Viewed by 1383

Abstract

The use of fibre-reinforced concrete (FRC) has been substantially increasing in the last few years, in different fields of the construction industry. Recently, many experiments have been performed to observe the short- and long-term mechanical behaviour of FRC, and several models have been [...] Read more.

The use of fibre-reinforced concrete (FRC) has been substantially increasing in the last few years, in different fields of the construction industry. Recently, many experiments have been performed to observe the short- and long-term mechanical behaviour of FRC, and several models have been formulated to capture its mechanical response. In this work, the mechanical behaviour is simulated through the Lattice Discrete Particle Model (LDPM) and its extension to fibre-reinforced cementitious composites (LDPM-F). This paper aims to provide insights into the calibration process and potential pitfalls in a case where only limited experimental data are available—in this case, unconfined uniaxial compression and three-point bending tests on different mixes of polypropylene and steel fibre-reinforced concretes. As a first step, a sensitivity analysis is performed to weight the effect of each governing mesoscale parameter on the simulated macroscale behaviour. Then, for each mix at issue, different sets of model parameters are identified as capable of accurately matching the experimental evidence. As a validation, each calibrated set is used to simulate energy absorption tests on round panels. The validation stage shows that one of the identified sets, for the FRC with polypropylene fibres, accurately matches the round panels’ response, while the others result in acceptable predictions. For the mix with steel fibres, instead, none of the sets captures the experimental results, likely due to the different post-cracking behaviour detected in fracture and energy absorption tests. Finally, a parametric study showcases how the LDPM-F might serve as tool to optimise the mix design without extensive experimental investigations. Full article

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4 pages, 139 KiB

Open AccessEditor’s ChoiceEditorial

Perspectives on Natural Fibers’ Competitiveness and Sustainability

by Mourad Krifa and Vinoth Kumar Gnanasekar

Fibers 2025, 13(2), 14; https://doi.org/10.3390/fib13020014 - 2 Feb 2025

Cited by 1 | Viewed by 1336

Abstract

Since antiquity, natural fibers have been a vital component of human civilization [...] Full article

(This article belongs to the Special Issue Natural Fiber Competitiveness and Sustainability)

19 pages, 13847 KiB

Open AccessEditor’s ChoiceArticle

Effect of GFRP and CFPR Hybrid Confinement on the Compressive Performance of Concrete

by Marina L. Moretti

Fibers 2025, 13(2), 12; https://doi.org/10.3390/fib13020012 - 24 Jan 2025

Cited by 1 | Viewed by 867

Abstract

Application of hybrid jackets consisting of comparatively stiff FRP materials for the seismic retrofit of substandard RC columns, aiming at reducing the risk of buckling and of brittle failure, which are typical to older columns, is a promising challenge. Given the sparsity of [...] Read more.

Application of hybrid jackets consisting of comparatively stiff FRP materials for the seismic retrofit of substandard RC columns, aiming at reducing the risk of buckling and of brittle failure, which are typical to older columns, is a promising challenge. Given the sparsity of similar experimental data, the objective of this paper is to study the hybrid effect in concrete confined with conventional carbon- and glass- reinforced polymer fabrics (CFRP and GFRP, respectively). Twenty-six concrete cylinders, wrapped by one to three layers of CFRP and GFRP with different fiber configurations, were tested in compression. A clear hybrid effect was observed, consisting of a less brittle failure and an improved confinement as compared to the behavior of simple jackets. Furthermore, hybrid specimens, in which a CFRP layer is substituted by a GFRP layer, appear to display similar efficiency in confinement compared to specimens with a stiffer jacket consisting of more CFRP sheets, which are expected to experience 30 to 40% higher lateral pressure owing to the stiffer jacket. A design model to estimate peak concrete compressive strength and axial strain is proposed. The results are promising towards the potential application of similar hybrid jackets for the seismic rehabilitation of older RC columns. Full article

(This article belongs to the Special Issue Fracture Behavior of Fiber-Reinforced Building Materials)

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31 pages, 4126 KiB

Open AccessEditor’s ChoiceArticle

Optimizing Controlled-Resonance Acoustic Metamaterials with Perforated Plexiglass Disks, Honeycomb Structures, and Embedded Metallic Masses

by Giuseppe Ciaburro, Gino Iannace and Virginia Puyana Romero

Fibers 2025, 13(2), 11; https://doi.org/10.3390/fib13020011 - 22 Jan 2025

Cited by 2 | Viewed by 1406

Abstract

Acoustic metamaterials offer new opportunities for controlling sound waves through engineered material configurations at the sub-wavelength scale. In this research, we present the optimization of a resonance-controlled acoustic metamaterial based on a sandwich structure composed of perforated plexiglass disks, honeycomb structures, and added [...] Read more.

Acoustic metamaterials offer new opportunities for controlling sound waves through engineered material configurations at the sub-wavelength scale. In this research, we present the optimization of a resonance-controlled acoustic metamaterial based on a sandwich structure composed of perforated plexiglass disks, honeycomb structures, and added metal masses. The innovative approach consists of integrating perforated plexiglass disks interspersed with honeycomb structures, which act as multiple and complex Helmholtz resonators, and adding metal masses to introduce resonances at specific frequencies. The metamaterial’s acoustic properties were experimentally characterized using an impedance tube (Kundt tube), allowing the measurement of the Sound Absorption Coefficient (SAC) over an expansive frequency selection. The results demonstrate a substantial enhancement in sound absorption at the target frequencies, demonstrating the effectiveness of the introduced resonances. Numerical simulations using an Artificial Neural Network (ANN) model in MATLAB environment were used to analyze the distribution of resonances and optimize the structural configuration. To effectively evaluate the acoustic properties of the metamaterial, various configurations were analyzed using perforated plexiglass disks combined with different layers of honeycombs arranged in a sandwich structure with a thickness ranging from 41 to 45 mm. A comparison of these configurations revealed a notable increase in the Sound Absorption Coefficient (SAC) when employing three layers of perforated plexiglass disks and adding masses to the first disk (about 14%). This study highlights the potential of resonance-controlled metamaterials for advanced applications in noise control and acoustic engineering. Full article

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24 pages, 13018 KiB

Open AccessEditor’s ChoiceArticle

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

Cited by 2 | Viewed by 1219

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

Open AccessEditor’s ChoiceArticle

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

Cited by 1 | Viewed by 1046

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

Open AccessEditor’s ChoiceReview

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

Cited by 2 | Viewed by 3158

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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29 pages, 5536 KiB

Open AccessEditor’s ChoiceReview

Natural Fiber-Reinforced Mycelium Composite for Innovative and Sustainable Construction Materials

by Maristella E. Voutetaki and Anastasios C. Mpalaskas

Fibers 2024, 12(7), 57; https://doi.org/10.3390/fib12070057 - 9 Jul 2024

Cited by 13 | Viewed by 8881

Abstract

Fiber-reinforced mycelium (FRM) composites offer an innovative and sustainable approach to construction materials for architectural structures. Mycelium, the root structure of fungi, can be combined with various natural fibers (NF) to create a strong and lightweight material with environmental benefits. Incorporating NF like [...] Read more.

Fiber-reinforced mycelium (FRM) composites offer an innovative and sustainable approach to construction materials for architectural structures. Mycelium, the root structure of fungi, can be combined with various natural fibers (NF) to create a strong and lightweight material with environmental benefits. Incorporating NF like hemp, jute, or bamboo into the mycelium matrix enhances mechanical properties. This combination results in a composite that boasts enhanced strength, flexibility, and durability. Natural FRM composites offer sustainability through the utilization of agricultural waste, reducing the carbon footprint compared to conventional construction materials. Additionally, the lightweight yet strong nature of the resulting material makes it versatile for various construction applications, while its inherent insulation properties contribute to improved energy efficiency in buildings. Developing and adopting natural FRM composites showcases a promising step towards sustainable and eco-friendly construction materials. Ongoing research and collaboration between scientists, engineers, and the construction industry will likely lead to further improvements and expanded applications. This article provides a comprehensive analysis of the current research and applications of natural FRM composites for innovative and sustainable construction materials. Additionally, the paper reviews the mechanical properties and potential impacts of these natural FRM composites in the context of sustainable architectural construction practices. Recently, the applicability of mycelium-based materials has extended beyond their original domains of biology and mycology to architecture. Full article

(This article belongs to the Special Issue Fracture Behavior of Fiber-Reinforced Building Materials)

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26 pages, 2239 KiB

Open AccessEditor’s ChoiceReview

Retting of Bast Fiber Crops Like Hemp and Flax—A Review for Classification of Procedures

by Morris Angulu and Hans-Jörg Gusovius

Fibers 2024, 12(3), 28; https://doi.org/10.3390/fib12030028 - 15 Mar 2024

Cited by 13 | Viewed by 4785

Abstract

The interest and thus the number of publications on the supply chains of bast fiber plants has steadily increased in recent years. A number of specific technical terms related to methods and their use for individual areas of the supply chain are often [...] Read more.

The interest and thus the number of publications on the supply chains of bast fiber plants has steadily increased in recent years. A number of specific technical terms related to methods and their use for individual areas of the supply chain are often interpreted and used in very different ways. Therefore, the aim of this publication is to increase the clarity of the description of the operations and to improve the understanding of the sequence and the purpose of the process steps. This is based on a selected review of the relevant literature as well as on suggestions for their classification Full article

(This article belongs to the Special Issue Fibers 10th Anniversary: Past, Present, and Future)

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36 pages, 7490 KiB

Open AccessEditor’s ChoiceReview

Developments of Core/Shell Chitosan-Based Nanofibers by Electrospinning Techniques: A Review

by Siriporn Taokaew and Tapanee Chuenkaek

Fibers 2024, 12(3), 26; https://doi.org/10.3390/fib12030026 - 12 Mar 2024

Cited by 23 | Viewed by 6348

Abstract

This review is focused on the recent development of various chitosan-based nanofibers (membranes, patches, mats, and scaffolds) that have been designed into core and shell structures using emulsion and coaxial electrospinning techniques. Chitosan, a promising polysaccharide derived from natural sources, holds potential for [...] Read more.

This review is focused on the recent development of various chitosan-based nanofibers (membranes, patches, mats, and scaffolds) that have been designed into core and shell structures using emulsion and coaxial electrospinning techniques. Chitosan, a promising polysaccharide derived from natural sources, holds potential for diverse applications, including nanofiber production, aimed at fostering sustainability. Core/shell chitosan-based nanofibers offer appealing features, including drug encapsulation and sustained release capabilities, with a higher efficiency than uniaxial fibers. The fabrication of core/shell chitosan-based nanofibers, including the co-spinning agents and various spinning parameters, such as spinning voltage, needle size, spinning flow rate, distance from needle tip to collector, temperature, and humidity, is summarized in this work. The review also explores updated applications in various fields, such as textiles, medical dressings, drug release systems, filtration membranes, and food packaging. It highlights the current advancements in core/shell chitosan-based nanofibers produced via electrospinning techniques. The innovative insights presented in the recent literature and the challenges associated with these sustainable materials are thoroughly examined, offering valuable contributions to the field. Full article

(This article belongs to the Special Issue Application of Chitosan in the Textile Field)

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26 pages, 7745 KiB

Open AccessEditor’s ChoiceArticle

Influence of Recycled High-Density Polyethylene Fibers on the Mechanical and Electrochemical Properties of Reinforced Concrete

by Alejandro Flores Nicolás, Elsa C. Menchaca Campos, Mario Flores Nicolás, José J. Martínez González, Omar A. González Noriega and Jorge Uruchurtu Chavarín

Fibers 2024, 12(3), 24; https://doi.org/10.3390/fib12030024 - 11 Mar 2024

Cited by 11 | Viewed by 3864

Abstract

The quantity of different plastics generated after consumption is an impact factor affecting the environment, and the lack of recycling generates solid waste. The purpose of this work is to incorporate high-density recycled polyethylene fibers (HDPE) for possible use as concrete reinforcement. Physical [...] Read more.

The quantity of different plastics generated after consumption is an impact factor affecting the environment, and the lack of recycling generates solid waste. The purpose of this work is to incorporate high-density recycled polyethylene fibers (HDPE) for possible use as concrete reinforcement. Physical and mechanical properties from recycled fibers were analyzed, such as density, absorption, and stress resistance, as well as workability, air content, porosity, concrete compression, and flexural strength properties. Samples were prepared with a low fiber content of 0.2% and 0.4%, as a substitution for sand weight, and lengths of 10 and 30 mm. To study corrosion phenomena, the specimens were exposed to a saline environment containing 3% sodium chloride for 365 days, and the electrochemical techniques including half-cell potential (HCP), electrochemical noise (EN), linear polarization resistance (LPR), and electrochemical impedance spectroscopy (EIS) were applied. The results showed a 4.8% increase in compressive strength with a low fiber percentage and short geometries, while flexural strength increased marginally by 2.3% with small quantities of HDPE fibers. All these factors contribute to greater material durability, less permeability, and crack control. A positive effect of fibers with short dimensions on the corrosion processes of a steel bar was observed, with the fibers acting as a physical barrier against the diffusion of chloride ions. Full article

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18 pages, 3633 KiB

Open AccessEditor’s ChoiceArticle

Evaluation of Hydrothermally Treated Wood Fibre Performance in Cement Mortars

by Petrini Kampragkou, Vasiliki Kamperidou and Maria Stefanidou

Fibers 2024, 12(3), 21; https://doi.org/10.3390/fib12030021 - 26 Feb 2024

Cited by 8 | Viewed by 2922

Abstract

Biofibres’ wide application in mortar enhancement has thus far been restricted by factors related to their chemical composition and hygroscopic nature. Their hydrophilic behaviour increases the water demand of mortar mixtures and diminishes their affinity to the matrix, while further moisture-related fibre degradation [...] Read more.

Biofibres’ wide application in mortar enhancement has thus far been restricted by factors related to their chemical composition and hygroscopic nature. Their hydrophilic behaviour increases the water demand of mortar mixtures and diminishes their affinity to the matrix, while further moisture-related fibre degradation issues may arise. Additionally, natural fibres seem to be susceptible to degradation caused by exposure to alkaline environmental conditions such as those experienced by cement mortars, restricting their utilisation in the construction industry. Therefore, the current study investigates the potential of fibre modification through treatments that would permanently alter their structure and chemical composition to improve their performance. In this study, wood fibres of black pine and beech species were exposed to mild thermal treatment (140 °C 2 h, under a steam atmosphere), characterised in terms of the physical and chemical properties and incorporated in cement mortars, applying the proportion of 1.5% v/v in the mortar, in order to assess their performance as reinforcement material. The mortars’ workability (at a fresh state) was examined, as well as other physical, hygroscopic, thermal, and mechanical characteristics of the mortars at the ages of 28, 90 and 365 days and weathering performance, by subjecting them to different artificial ageing environments (freeze–thaw cycles or outdoor exposure). The results revealed the beneficial role of the treated fibres in dimensional stability, flexural strength, thermal insulation properties and capillary absorption of the mortar specimens, especially during the ageing process, with the black pine fibres showing the greatest improvement. The hydrothermally treated wood fibres seem to help maintain the integrity of cement mortars under all ageing conditions, proving that they could provide low-cost and eco-friendly mortar enhancement pathways. Full article

(This article belongs to the Special Issue Organic Natural Fibers and Textiles for Reinforcement and Performance Enhancement of Mortars and Concrete)

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19 pages, 8938 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Methodological Aspects and Mesh Convergence in Numerical Analysis of Athermal Fiber Network Material Deformation

by Nishan Parvez, Syed Nabeel Amjad, Mithun K. Dey and Catalin R. Picu

Fibers 2024, 12(1), 9; https://doi.org/10.3390/fib12010009 - 12 Jan 2024

Cited by 7 | Viewed by 3169

Abstract

A balance between model complexity, accuracy, and computational cost is a central concern in numerical simulations. In particular, for stochastic fiber networks, the non-affine deformation of fibers, related non-linear geometric features due to large global deformation, and size effects can significantly affect the [...] Read more.

A balance between model complexity, accuracy, and computational cost is a central concern in numerical simulations. In particular, for stochastic fiber networks, the non-affine deformation of fibers, related non-linear geometric features due to large global deformation, and size effects can significantly affect the accuracy of the computer experiment outputs and increase the computational cost. In this work, we systematically investigate methodological aspects of fiber network simulations with a focus on the output accuracy and computational cost in models with cellular (Voronoi) and fibrous (Mikado) network architecture. We study both p and h-refinement of the discretizations in finite element solution procedure, with uniform and length-based adaptive h-refinement strategies. The analysis is conducted for linear elastic and viscoelastic constitutive behavior of the fibers, as well as for networks with initially straight and crimped fibers. With relative error as the determining criterion, we provide recommendations for mesh refinement, comment on the necessity of multiple realizations, and give an overview of associated computational cost that will serve as guidance toward minimizing the computational cost while maintaining a desired level of solution accuracy. Full article

(This article belongs to the Special Issue Fibers 10th Anniversary: Past, Present, and Future)

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12 pages, 2752 KiB

Open AccessEditor’s ChoiceArticle

Production of Nanofibers by Blow Spinning from Polylactide Containing Propolis and Beeswax

by Agata Penconek, Maciej Kilarski, Anna Soczewka, Michał Wojasiński and Arkadiusz Moskal

Fibers 2024, 12(1), 8; https://doi.org/10.3390/fib12010008 - 12 Jan 2024

Cited by 6 | Viewed by 2692

Abstract

The growing pollution of the environment with slowly decomposing waste, as well as the increasing drug resistance of pathogens, including the antibiotic resistance of bacteria, has led to a search for new solutions based on biodegradable and natural materials, which are known for [...] Read more.

The growing pollution of the environment with slowly decomposing waste, as well as the increasing drug resistance of pathogens, including the antibiotic resistance of bacteria, has led to a search for new solutions based on biodegradable and natural materials, which are known for their potential bacteriostatic properties. This study aimed to produce nanofibers by blowing from a polylactide (PLA) polymer solution containing natural compounds (e.g., beeswax, propolis). As a result of the conducted research, nanofibers were produced from PLA solutions containing various additives. The fibers’ mean diameter ranges from 0.36 to 2.38 µm, depending on the process parameters. To the authors’ knowledge, fibers were produced for the first time by blow spinning from a polymer solution containing propolis and beeswax. Full article

(This article belongs to the Special Issue Nanofibers: Biomedical Applications)

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17 pages, 5565 KiB

Open AccessEditor’s ChoiceArticle

Investigation of the Effect of Chemical Treatment on the Properties of Colombian Banana and Coir Fibers and Their Adhesion Behavior on Polylactic Acid and Unsaturated Polyester Matrices

by Ismael Barrera-Fajardo, Oswaldo Rivero-Romero and Jimy Unfried-Silgado

Fibers 2024, 12(1), 6; https://doi.org/10.3390/fib12010006 - 3 Jan 2024

Cited by 11 | Viewed by 3059

Abstract

In this work, the adhesion behavior of chemically treated banana and coir Colombian fibers embedded in polylactic acid (PLA) and unsaturated polyester resin (UPR) matrices was investigated. Both types of fibers were treated with a 5 wt.% sodium hydroxide solution for one hour. [...] Read more.

In this work, the adhesion behavior of chemically treated banana and coir Colombian fibers embedded in polylactic acid (PLA) and unsaturated polyester resin (UPR) matrices was investigated. Both types of fibers were treated with a 5 wt.% sodium hydroxide solution for one hour. The properties of treated and untreated fibers were determined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and tensile tests. To evaluate the adhesion behavior of the fibers in PLA and UPR matrices, pull-out tests were performed, and the percentage of broken fibers was determined. The results showed that alkaline treatment improved the fibers’ physicochemical, mechanical, and thermal properties. In addition, the alkaline treatment was able to improve the adhesion behavior of coir and banana fibers to PLA and UPR matrices. The banana fibers showed a percentage of broken fibers of 100%, while the coir fibers showed a slight increase in IFSS value. This behavior is attributed to the improvement in surface roughness due to the removal of non-cellulosic composites and impurities. Full article

(This article belongs to the Special Issue Natural Fiber Competitiveness and Sustainability)

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17 pages, 4322 KiB

Open AccessEditor’s ChoiceArticle

Mechanical Properties of 3D-Printed Carbon Fiber-Reinforced Cement Mortar

by Yeou-Fong Li, Pei-Jen Tsai, Jin-Yuan Syu, Man-Hoi Lok and Huei-Shiung Chen

Fibers 2023, 11(12), 109; https://doi.org/10.3390/fib11120109 - 11 Dec 2023

Cited by 8 | Viewed by 3783

Abstract

The 3D printing process is different from traditional construction methods of formwork casting due to the use of additive manufacturing. This study develops a suitable 3D-printed carbon fiber-reinforced cement mortar (CFRCM) considering the extrudability, fluidity, setting time, and buildability of the CFRCM. The [...] Read more.

The 3D printing process is different from traditional construction methods of formwork casting due to the use of additive manufacturing. This study develops a suitable 3D-printed carbon fiber-reinforced cement mortar (CFRCM) considering the extrudability, fluidity, setting time, and buildability of the CFRCM. The difference in compressive strength and flexural strength between 3D-printed specimens and conventional cast specimens was investigated by varying the amount of carbon fiber added (carbon fiber to cement ratio, 2.5 vol.‰, 5 vol.‰, 7.5 vol.‰, and 10 vol.‰) and the curing times (7th day and 28th day). The results of the experiments indicate that the addition of 6 wt.% cement accelerators to the cementitious mortar allows for a controlled initial setting time of approximately half an hour. The fluidity of the CFRCM was controlled by adjusting the dosage of the superplasticizer. When the slump was in the range of 150 mm to 190 mm, the carbon fiber to cement ratio 2.5 vol.‰ could be incorporated into the cementitious mortar, enabling the printing of hollow cylinders with a height of up to 750 mm. Comparing the 3D-printed specimens with the traditionally cast specimens, it was found that the addition of a carbon fiber to cement ratio of 7.5 vol.‰, and 10 vol.‰ resulted in the optimal compressive strength and flexural strength, respectively. Full article

(This article belongs to the Special Issue Fibers in Concrete Construction: Material Behavior, Design and Strengthening II)

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25 pages, 3449 KiB

Open AccessEditor’s ChoiceReview

Characterization Specifications for FRP Pultruded Materials: From Constituents to Pultruded Profiles

by Ehsan Harati Khalilabad, Alvaro Ruiz Emparanza, Francisco De Caso, Hossein Roghani, Nima Khodadadi and Antonio Nanni

Fibers 2023, 11(11), 93; https://doi.org/10.3390/fib11110093 - 2 Nov 2023

Cited by 10 | Viewed by 4739

Abstract

Pultruded FRP composites have emerged as a promising alternative to traditional materials like concrete, steel, and timber, especially in corrosive environmental conditions. However, the unique properties of these composites necessitate careful consideration during their implementation, as they differ significantly from conventional materials. Proper [...] Read more.

Pultruded FRP composites have emerged as a promising alternative to traditional materials like concrete, steel, and timber, especially in corrosive environmental conditions. However, the unique properties of these composites necessitate careful consideration during their implementation, as they differ significantly from conventional materials. Proper testing and characterization of FRP pultruded materials is key for their efficient and safe implementation. However, the existing specifications are not unified, resulting in ambiguity among stakeholders. This paper aims to bridge this gap by thoroughly reviewing current destructive and non-destructive test methods for FRP pultruded materials, specifications, quality control, and health monitoring of FRP structures. Each subsection is further divided into subtopics, providing a comprehensive overview of the subject. By shedding light on these crucial aspects, this article aims to accelerate the adoption and utilization of these innovative materials in practical applications. Full article

(This article belongs to the Special Issue Use of Fibers in Organic and Inorganic Composite Solutions for Structural Strengthening: Advances, Applications, and Challenges)

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22 pages, 4062 KiB

Open AccessEditor’s ChoiceArticle

Conversion of Animal-Derived Protein By-Products into a New Dual-Layer Nanofiber Biomaterial by Electrospinning Process

by Carmen Gaidău, Maria Râpă, Laura Mihaela Stefan, Ecaterina Matei, Andrei Constantin Berbecaru, Cristian Predescu and Liliana Mititelu-Tartau

Fibers 2023, 11(10), 87; https://doi.org/10.3390/fib11100087 - 14 Oct 2023

Cited by 6 | Viewed by 2805

Abstract

The aim of this study was to design a dual-layer wound dressing as a new fibrous biomaterial based on the valorization of animal-derived proteins. The first layer was fabricated by the deposition of poly(ethylene oxide) (PEO) loaded with keratin hydrolysate (KH) via a [...] Read more.

The aim of this study was to design a dual-layer wound dressing as a new fibrous biomaterial based on the valorization of animal-derived proteins. The first layer was fabricated by the deposition of poly(ethylene oxide) (PEO) loaded with keratin hydrolysate (KH) via a mono-electrospinning process onto a poly(lactic acid) (PLA) film, which was used as a support. The second layer consisted of encapsulating a bovine collagen hydrolysate (CH) into poly(vinyl pyrrolidone) (PVP) through a coaxial electrospinning process, which was added onto the previous layer. This assemblage was characterized by electronic microscopy for morphology and the controlled release of KH. In vitro biocompatibility was evaluated on the L929 (NCTC) murine fibroblasts using quantitative MTT assay and qualitative cell morphological examination after Giemsa staining. Additionally, in vivo biocompatibility methods were used to assess the impact of the biomaterial on white Swiss mice, including the evaluation of hematological, biochemical, and immunological profiles, as well as its impact on oxidative stress. The results revealed a nanofibrous structure for each layer, and the assembled product demonstrated antioxidant activity, controlled release of KH, a high degree of in vitro biocompatibility, negligible hematological and biochemical changes, and minimal impact of certain specific oxidative stress parameters compared to the use of patches with textile support. Full article

(This article belongs to the Special Issue Nanofibers: Biomedical Applications)

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25 pages, 2412 KiB

Open AccessEditor’s ChoiceReview

Overcoming Challenges and Limitations Regarding the Atomic Force Microscopy Imaging and Mechanical Characterization of Nanofibers

by Stylianos Vasileios Kontomaris, Andreas Stylianou, Georgios Chliveros and Anna Malamou

Fibers 2023, 11(10), 83; https://doi.org/10.3390/fib11100083 - 9 Oct 2023

Cited by 13 | Viewed by 4600

Abstract

Atomic force microscopy (AFM) is a powerful tool that enables imaging and nanomechanical properties characterization of biological materials. Nanofibers are the structural units of many biological systems and their role in the development of advanced biomaterials is crucial. AFM methods have proven to [...] Read more.

Atomic force microscopy (AFM) is a powerful tool that enables imaging and nanomechanical properties characterization of biological materials. Nanofibers are the structural units of many biological systems and their role in the development of advanced biomaterials is crucial. AFM methods have proven to be effective towards the characterization of fibers with respect to biological and bioengineering applications at the nanoscale. However, both the topographical and mechanical properties’ nanocharacterizations of single fibers using AFM are challenging procedures. In particular, regarding imaging procedures, significant artifacts may arise from tip convolution effects. The geometrical characteristics of the AFM tip and the nanofibers, and the fact that they have similar magnitudes, may lead to significant errors regarding the topographical imaging. In addition, the determination of the mechanical properties of nanofibers is also challenging due to their small dimensions and heterogeneity (i.e., the elastic half-space assumption is not valid in most cases). This review elucidates the origins of errors in characterizing individual nanofibers, while also providing strategies to address limitations in experimental procedures and data processing. Full article

(This article belongs to the Special Issue Nanofibers: Biomedical Applications)

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24 pages, 9868 KiB

Open AccessEditor’s ChoiceReview

Analytical Methods for the Identification and Quantitative Determination of Wool and Fine Animal Fibers: A Review

by Marina Zoccola, Parag Bhavsar, Anastasia Anceschi and Alessia Patrucco

Fibers 2023, 11(8), 67; https://doi.org/10.3390/fib11080067 - 2 Aug 2023

Cited by 12 | Viewed by 5765

Abstract

The identification and quantitative determination of wool and fine animal fibers are of great interest in the textile field because of the significant price differences between them and common impurities in raw and processed textiles. Since animal fibers have remarkable similarities in their [...] Read more.

The identification and quantitative determination of wool and fine animal fibers are of great interest in the textile field because of the significant price differences between them and common impurities in raw and processed textiles. Since animal fibers have remarkable similarities in their chemical and physical characteristics, specific identification methods have been studied and proposed following advances in analytical technologies. The identification methods of wool and fine animal fibers are reviewed in this paper, and the results of relevant studies are listed and summarized, starting from classical microscopy methods, which are still used today not only in small to medium enterprises but also in large industries, research studies and quality control laboratories. Particular attention has been paid to image analysis, Nir spectroscopy and proteomics, which constitute the most promising technologies of quality control in the manufacturing and trading of luxury textiles and can find application in forensic science and archeology. Full article

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19 pages, 3438 KiB

Open AccessEditor’s ChoiceArticle

Failure Mode Prediction of Unreinforced Masonry (URM) Walls Retrofitted with Cementitious Textile Reinforced Mortar (TRM)

by Athanasia K. Thomoglou, Martha A. Karabini, Dimitra V. Achillopoulou, Theodoros C. Rousakis and Constantin E. Chalioris

Fibers 2023, 11(6), 53; https://doi.org/10.3390/fib11060053 - 15 Jun 2023

Cited by 8 | Viewed by 3414

Abstract

The brittle failure of unreinforced masonry (URM) walls when subjected to in-plane loads present low shear strength remains a critical issue. The investigation presented in this paper touches on the retrofitting of URM structures with textile-reinforced mortar (TRM), which enables shifting the shear [...] Read more.

The brittle failure of unreinforced masonry (URM) walls when subjected to in-plane loads present low shear strength remains a critical issue. The investigation presented in this paper touches on the retrofitting of URM structures with textile-reinforced mortar (TRM), which enables shifting the shear failure mode from a brittle to a pseudo-ductile mode. Despite many guidelines for applying composite materials for retrofitting and predicting the performance of strengthened structures, the application of TRM systems in masonry walls is not extensively described. A thorough retrospect of the literature is presented, containing research results relating to different masonry walls, e.g., bricks, cement, and stone blocks strengthened with TRM jackets and subjected to diagonal compression loads. The critical issue of this study is the failure mode of the retrofitted masonry walls. Available prediction models are presented, and their predictions are compared to the experimental results based on their failure modes. The novelty of this study is the more accurate failure mode prediction of reinforced masonry with TRM and also of the shear strength with the proposed model, Thomoglou et al., 2020, at an optimal level compared to existing regulations and models. The novel prediction model estimates the shear failure mode of the strengthened wall while considering the contribution of all components, e.g., block, render mortar, strengthening textile, and cementitious matrix, by modifying the expressions of the Eurocode 8 provisions. The results have shown that the proposed model presents an optimum accuracy in predicting the failure mode of all different masonry walls strengthened with various TRM jackets and could be taken into account in the regulations for reliable forecasting. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymers and Fiber-Reinforced Cement-Based Mortars in Repair/Strengthening Methods of Masonry and Reinforced Concrete Structural Members)

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15 pages, 3866 KiB

Open AccessEditor’s ChoiceArticle

The Exothermic Effects of Textile Fibers during Changes in Environmental Humidity: A Comparison between ISO:16533 and Dynamic Hot Plate Test Method

by Faisal Abedin and Emiel DenHartog

Fibers 2023, 11(5), 47; https://doi.org/10.3390/fib11050047 - 22 May 2023

Cited by 7 | Viewed by 4085

Abstract

The exothermic effects of high regain fiber types have been described before; yet, there have not been reliable tests to demonstrate these effects on the human body. Most test methods focus on steady-state measurements; therefore, these exothermic effects during changes in environmental humidity [...] Read more.

The exothermic effects of high regain fiber types have been described before; yet, there have not been reliable tests to demonstrate these effects on the human body. Most test methods focus on steady-state measurements; therefore, these exothermic effects during changes in environmental humidity are typically not analyzed or quantified. We have conducted a set of fabric tests that shows the connection between the exothermic effect of water vapor uptake and its consequence for heat loss through the fabric in transient conditions. We have performed the ISO:16533 standard test, a dynamic hot plate test developed by Naylor to measure the exothermic property of the fabric, and dynamic regain tests to connect the dots between these tests and the water vapor uptake phenomenon. Although the ISO:16533 test method tends to show the temperature increase in fibers, it cannot differentiate between the hygroscopic fiber (wool, viscose, cotton) types (p > 0.001). In addition, sensor size and sample folding techniques could impact the temperature increase. On the other hand, the Naylor hot plate test showed a greater difference in heat release among the fiber types (wool showed 20% higher heat release than viscose, 50% more than cotton), although the relative humidity changes in the chamber take time, which might not reflect a step-wise change in humidity. So far, these test methods have proven to be the most reliable for determining the exothermic behavior of textile fiber. However, these test methods still have limitations and cannot simulate realistic environmental conditions considering an instantaneous change in the environment. This paper reflects the comparison between the two test methods and recommends directions to accurately address the theory of water vapor uptake under dynamic conditions. Full article

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17 pages, 4174 KiB

Open AccessEditor’s ChoiceArticle

Elementary Liber Fibres Characterisation: Bias from the Noncylindricity and Morphological Evolution along the Fibre

by Marie Grégoire, Emmanuel De Luycker and Pierre Ouagne

Fibers 2023, 11(5), 45; https://doi.org/10.3390/fib11050045 - 15 May 2023

Cited by 6 | Viewed by 1851

Abstract

In this work, we investigate the influence of noncircularity along with cross-sectional area evolution on the measurement of the mechanical properties of elementary fibres. First, we focus on the cross-sectional area measurement and compare the circular assumption with the elliptical one using an [...] Read more.

In this work, we investigate the influence of noncircularity along with cross-sectional area evolution on the measurement of the mechanical properties of elementary fibres. First, we focus on the cross-sectional area measurement and compare the circular assumption with the elliptical one using an ombroscopic device that allows the measurement of the projected diameters along the fibre as the fibre rotates around its axis, the fibre dimensional analysis system (FDAS). The results highlight important approximations to the cross-sectional area evaluation for fibres with noncircular cross sections, leading to reduced elastic modulus and stress at failure evaluated by the standard method. Additionally, results from the FDAS are used to evaluate the twist inside an individual fibre when the cross sections are sufficiently elliptical. A numerical model based on the real measured dimensions of the fibres is developed to illustrate and visualize this nonuniformity and to more accurately identify the elastic modulus. The results obtained lead us to an analytical approach that takes into account the evolution of the cross-sectional area along the fibre for a better identification of the stiffness and modulus of elasticity, which maximizes the identified mechanical properties on average by 12% for the modulus and 200% for the stress at failure. Finally, recommendations are formulated to better account for the variability along a fibre in order to evaluate the cross-sectional area. Full article

(This article belongs to the Special Issue Fiber Composite Process)

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42 pages, 15346 KiB

Open AccessEditor’s ChoiceReview

A Review of Fibre Reinforced Polymer Bridges

by Jawed Qureshi

Fibers 2023, 11(5), 40; https://doi.org/10.3390/fib11050040 - 4 May 2023

Cited by 17 | Viewed by 15690

Abstract

Fibre-reinforced polymer composites (FRPs) offer various benefits for bridge construction. Lightweight, durability, design flexibility and fast erection in inaccessible areas are their unique selling points for bridge engineering. FRPs are used in four bridge applications: (1) FRP rebars/tendons in concrete; (2) repair and [...] Read more.

Fibre-reinforced polymer composites (FRPs) offer various benefits for bridge construction. Lightweight, durability, design flexibility and fast erection in inaccessible areas are their unique selling points for bridge engineering. FRPs are used in four bridge applications: (1) FRP rebars/tendons in concrete; (2) repair and strengthening of existing bridges; (3) new hybrid–FRP bridges with conventional materials and (4) all–FRP composite new bridges made entirely of FRP materials. This paper reviews FRP bridges, including all–FRP and hybrid–FRP bridges. FRP bridges’ history, materials, processes and bridge components—deck, girder, truss, moulded parts and cables/rebars are considered. This paper does not discuss the use of FRP as an architectural element and a strengthening system. While lack of design codes, material specifications and recycling are the major challenges, the high cost of FRPs still remains the most critical barrier to the progress of FRPs in bridges. Full article

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

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40 pages, 4925 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Mechanical Properties and Morphological Alterations in Fiber-Based Scaffolds Affecting Tissue Engineering Outcomes

by James Dolgin, Samerender Nagam Hanumantharao, Stephen Farias, Carl G. Simon, Jr. and Smitha Rao

Fibers 2023, 11(5), 39; https://doi.org/10.3390/fib11050039 - 29 Apr 2023

Cited by 27 | Viewed by 5163

Abstract

Electrospinning is a versatile tool used to produce highly customizable nonwoven nanofiber mats of various fiber diameters, pore sizes, and alignment. It is possible to create electrospun mats from synthetic polymers, biobased polymers, and combinations thereof. The post-processing of the end products can [...] Read more.

Electrospinning is a versatile tool used to produce highly customizable nonwoven nanofiber mats of various fiber diameters, pore sizes, and alignment. It is possible to create electrospun mats from synthetic polymers, biobased polymers, and combinations thereof. The post-processing of the end products can occur in many ways, such as cross-linking, enzyme linking, and thermal curing, to achieve enhanced chemical and physical properties. Such multi-factor tunability is very promising in applications such as tissue engineering, 3D organs/organoids, and cell differentiation. While the established methods involve the use of soluble small molecules, growth factors, stereolithography, and micro-patterning, electrospinning involves an inexpensive, labor un-intensive, and highly scalable approach to using environmental cues, to promote and guide cell proliferation, migration, and differentiation. By influencing cell morphology, mechanosensing, and intracellular communication, nanofibers can affect the fate of cells in a multitude of ways. Ultimately, nanofibers may have the potential to precisely form whole organs for tissue engineering, regenerative medicine, and cellular agriculture, as well as to create in vitro microenvironments. In this review, the focus will be on the mechanical and physical characteristics such as porosity, fiber diameter, crystallinity, mechanical strength, alignment, and topography of the nanofiber scaffolds, and the impact on cell proliferation, migration, and differentiation. Full article

(This article belongs to the Special Issue Nanofibers: Biomedical Applications)

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17 pages, 4767 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Production of Long Hemp Fibers Using the Flax Value Chain

by Lola Pinsard, Nathalie Revol, Henri Pomikal, Emmanuel De Luycker and Pierre Ouagne

Fibers 2023, 11(5), 38; https://doi.org/10.3390/fib11050038 - 28 Apr 2023

Cited by 9 | Viewed by 4755

Abstract

Hemp is finding a strong renewal of interest in the production of fine fibers for garment textiles. This resource of long-line fibers would come as a complement to the highly demanded flax fibers, whose large production in the north-west of Europe cannot be [...] Read more.

Hemp is finding a strong renewal of interest in the production of fine fibers for garment textiles. This resource of long-line fibers would come as a complement to the highly demanded flax fibers, whose large production in the north-west of Europe cannot be extended. In Normandy, where a complete industrial value chain exists for flax, it is intended to adapt it to hemp, and this was demonstrated from the field to the scutched fibers with a complete value chain. In this region, early harvesting is necessary to leave enough time for dew-retting and permit dry storage of stems before mid-September. An early-flowering variety (USO-31) was harvested using dedicated hemp equipment to obtain a 1 m parallel and aligned windrow that can be further processed by flax equipment. The scutching process as well as the fiber’s morphological and mechanical properties were particularly studied. Adapted scutching process parameters with reduced advancing speed and beating turbine velocity led to long fiber yields of about 18% of the stem mass. Stem yields were reaching about 6 tons/ha leading to a production of 1.1 tons/ha of long fibers. The tensile properties of the long fibers were highly sufficient for textile applications, and their thickness after hackling was in the range suitable for the production of fine yarns. Compared to other crops grown in Normandy, the hemp as produced in this 2020 case study provides good incomes to the farmer, higher than traditional crops such as wheat or barley, and the results of this study should encourage farmers to grow hemp for textile purposes. Full article

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25 pages, 10545 KiB

Open AccessEditor’s ChoiceArticle

An Electromechanical Impedance-Based Application of Realtime Monitoring for the Load-Induced Flexural Stress and Damage in Fiber-Reinforced Concrete

by Maria C. Naoum, George M. Sapidis, Nikos A. Papadopoulos and Maristella E. Voutetaki

Fibers 2023, 11(4), 34; https://doi.org/10.3390/fib11040034 - 11 Apr 2023

Cited by 25 | Viewed by 2894

Abstract

Effective real-time structural health monitoring in concrete structures is paramount to evaluating safety conditions and the timely maintenance of concrete structures. Especially, the presence of discrete fibers in fiber-reinforced concrete restrains crack propagation into small and thin cracks, which increases the difficulty in [...] Read more.

Effective real-time structural health monitoring in concrete structures is paramount to evaluating safety conditions and the timely maintenance of concrete structures. Especially, the presence of discrete fibers in fiber-reinforced concrete restrains crack propagation into small and thin cracks, which increases the difficulty in detecting damage. In this study, an array of piezoelectric lead zirconate titanate (PZT) transducers was applied to study the effects of external load-induced flexural stress and damage in fiber-reinforced concrete beams using the electromechanical impedance (EMI) or electromechanical admittance (EMA) methods. Beams were subjected to a four-point bending test under repeatable loading, while PZTs evaluated corresponding flexural stress and induced damage simultaneously. Due to the influence of the medium’s stress fields in the different types of wave propagation in structural elements, PZT transducers measurements are accordingly affected under variable stress fields, in addition to the effect of the higher level of damage that occurred in the medium. According to the results of the tests, variation in EMA signatures, following flexural stress and gradual damage changes, provided convincing evidence for predicting stress and damage development. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymers and Fiber-Reinforced Cement-Based Mortars in Repair/Strengthening Methods of Masonry and Reinforced Concrete Structural Members)

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18 pages, 6092 KiB

Open AccessEditor’s ChoiceArticle

Effect of Elevated Temperature on the Behavior of Amorphous Metallic Fibre-Reinforced Cement and Geopolymer Composites

by Faiz Uddin Ahmed Shaikh, Narwinder Singh Kahlon and Attiq Ur Rahman Dogar

Fibers 2023, 11(4), 31; https://doi.org/10.3390/fib11040031 - 28 Mar 2023

Cited by 7 | Viewed by 2536

Abstract

To improve the tensile, flexural, and ductility properties of geopolymer composites, amorphous metallic fibres (AMF) are used to reinforce these composites, and the behavior of these composites at elevated temperatures has been assessed in this study. Four types of composites, i.e., cement, reinforced [...] Read more.

To improve the tensile, flexural, and ductility properties of geopolymer composites, amorphous metallic fibres (AMF) are used to reinforce these composites, and the behavior of these composites at elevated temperatures has been assessed in this study. Four types of composites, i.e., cement, reinforced cement, geopolymer, and reinforced geopolymer composites have been prepared. The composites have been reinforced using AMF with a fibre volume fraction of 0.75%. The composites have been assessed for change in mass loss, cracking, compressive strength, and flexural strength at four elevated temperatures of 200 °C, 400 °C, 600 °C, and 800 °C, and conclusions have been drawn concerning these composites. The results have shown that an increase in temperature has an adverse effect on these composites, and geopolymer composites exhibit higher performance than their counterpart cement composites at elevated temperatures. The mass loss and surface cracking were significantly lower in geopolymer composites, and the fibre reinforcement had a negligible effect on mass loss. Also, the residual compressive and flexural strength of reinforced geopolymer composites was significantly higher than that of the reinforced cement composites. In addition, scanning electron microscopic images also showed that even at higher temperatures, the geopolymer matrix is present on the AMF fibre, which results in higher residual strength than the cement composites in which a negligible amount of matrix is present on the fibres. Full article

(This article belongs to the Collection Feature Papers in Fibers)

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21 pages, 8315 KiB

Open AccessEditor’s ChoiceReview

Textile Fabrics as Electromagnetic Shielding Materials—A Review of Preparation and Performance

by Tomasz Blachowicz, Dariusz Wójcik, Maciej Surma, Mirosław Magnuski, Guido Ehrmann and Andrea Ehrmann

Fibers 2023, 11(3), 29; https://doi.org/10.3390/fib11030029 - 15 Mar 2023

Cited by 23 | Viewed by 9205

Abstract

Shielding of instruments and humans from electromagnetic interference (EMI) has become increasingly important during the last decades due to more and more machines and devices radiating electromagnetic waves. While several applications can use rigid shields, more flexibility is enabled by developing bendable, drapable, [...] Read more.

Shielding of instruments and humans from electromagnetic interference (EMI) has become increasingly important during the last decades due to more and more machines and devices radiating electromagnetic waves. While several applications can use rigid shields, more flexibility is enabled by developing bendable, drapable, ideally even stretchable EMI shielding. Textile fabrics can have these properties, combined with potentially good mechanical properties, depending on the textile structure and the chosen material. On the other hand, the necessary physical properties, especially conductivity and magnetic properties, cannot be taken for granted in normal textile fabrics. These properties have to be added by conductive yarn or layer coatings, integration of conductive or magnetic fibers, producing intrinsically conductive or magnetic fibers, etc. The article gives a critical comparison of the properties of materials typically used for this purpose, such as intrinsically conductive polymers, metal-coated fabrics and metal wires, MXene coatings, MXene fibers, carbon coatings, and fibers. The review concentrates on thematically suitable papers found in the Web of Science and Google Scholar from the last five years and shows that especially MXenes are highly investigated recently due to their high conductivity and EMI shielding effectiveness, while other conductive and magnetic coatings and fibers are nevertheless still interesting for the preparation of EMI shielding textile fabrics. Full article

(This article belongs to the Collection Feature Papers in Fibers)

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17 pages, 4939 KiB

Open AccessEditor’s ChoiceArticle

Application of Transformed Cross-Section Method for Analytical Analysis of Laminated Veneer Lumber Beams Strengthened with Composite Materials

by Michał Marcin Bakalarz and Paweł Grzegorz Kossakowski

Fibers 2023, 11(3), 24; https://doi.org/10.3390/fib11030024 - 23 Feb 2023

Cited by 11 | Viewed by 3287

Abstract

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials [...] Read more.

Due to the high cost of laboratory testing, many researchers are considering developing methods to predict the behavior of unreinforced and reinforced wood beams. This work aims to create either numerical or analytical models useful for extrapolating already conducted tests to other schemes/materials used as reinforcement. In the case of timber structures, due to the complexity of timber, this task is difficult. The first part of the article presents an analysis of the suitability of using a simplified mathematical model based on the equivalent cross-section method to describe the behavior of unreinforced and reinforced with carbon-fibre-reinforced polymer (CFRP) composite full-size laminated veneer lumber (LVL) beams. The theoretical results were compared with the results of conducted experimental tests. The scope of the analysis includes the estimation of modulus of rupture, bending stiffness, and determination of the neutral axis position. The equivalent cross-section method showed good agreement in determining the bending stiffness and neutral axis position of the strengthened sections. However, the suitability of using the equivalent cross-section method to estimate the load-carrying capacity of a cross-section reinforced with fiber composites still needs to be confirmed, which, according to the authors, is due to the differences between the assumed (linear) and actual (nonlinear) strain distribution in the compression zone. The second part uses the equivalent cross-section method to estimate the predicted bending stiffness of LVL beams strengthened with aramid-fibre-reinforced polymer (AFRP), glass-fibre-reinforced polymer (GFRP), and ultra-high modulus carbon-fibre-reinforced polymer (CFRP UHM) sheets. The proposed method can be used for preliminary evaluation of strengthening effectiveness of LVL beams. Full article

(This article belongs to the Special Issue Carbon Fibers from Sustainable Precursors)

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19 pages, 4569 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Synergistic Effect of HEDP.4Na and Different Induced Pouring Angles on Mechanical Properties of Fiber-Reinforced Alkali-Activated Slag Composites

by Jingjie Wei, Jianwei Liu, Kamal H. Khayat and Wu-Jian Long

Fibers 2023, 11(3), 23; https://doi.org/10.3390/fib11030023 - 22 Feb 2023

Cited by 7 | Viewed by 3123

Abstract

The poor flexural and damping properties of building materials damages concrete structures and affects their service life when concrete structures are subjected to dynamic loads. Three different dosages (i.e., 0%, 0.3%, and 0.6%) of organic phosphonates (HEDP.4Na) and different pouring methods (i.e., conventional [...] Read more.

The poor flexural and damping properties of building materials damages concrete structures and affects their service life when concrete structures are subjected to dynamic loads. Three different dosages (i.e., 0%, 0.3%, and 0.6%) of organic phosphonates (HEDP.4Na) and different pouring methods (i.e., conventional pouring method, 90°-induced pouring method, and 150°-induced pouring method) were designed to improve the flexural and damping performance of fiber-reinforced alkali-activated slag composites (FR-AASC). The enhanced mechanism of HEDP.4Na was revealed by phase analysis (X-ray diffraction, XRD), pore structure analysis (Mercury Intrusion Porosimetry, MIP), the heat of hydration, and scanning electron microscopy (SEM) analysis. The results showed that 0.3% HEDP.4Na combined with the 150°-induced pouring angle can significantly improve the mechanical properties of the FR-AASC sample compared with the reference group. The sample with 0.3% HEDP.4Na cast by the 150°-induced pouring angle increased compressive and flexural strength, damping energy consumption and storage modulus by 20%, 60%, 78%, and 30%, respectively, compared with the reference sample cast by the conventional pouring methodology. HEDP.4Na reduced the early hydration heat and total porosity of the FR-AASC matrix, modified the fiber–matrix interface transition zone, and increased the frictional energy consumption of steel fibers. Overall, the synergistic effect of HEDP.4Na and the induced pouring methodology significantly improved the flexural and damping properties of FR-AASC. This study can provide a guidance for improving the flexural and damping capacity of FR-AASC and promote the application of FR-AASC in construction engineering. Full article

(This article belongs to the Special Issue Fracture Behavior of Fiber-Reinforced Building Materials)

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37 pages, 8935 KiB

Open AccessFeature PaperEditor’s ChoiceReview

Nanofibres in Drug Delivery Applications

by Samia Farhaj, Barbara R. Conway and Muhammad Usman Ghori

Fibers 2023, 11(2), 21; https://doi.org/10.3390/fib11020021 - 17 Feb 2023

Cited by 57 | Viewed by 12381

Abstract

Over the years, scientists have been continually striving to develop innovative solutions to design and fabricate medicines with improved therapeutic potential. Conventional dosage forms, such as tablets, capsules, and injections, are limited when exploited for advanced therapeutics, such as drug targeting. To cater [...] Read more.

Over the years, scientists have been continually striving to develop innovative solutions to design and fabricate medicines with improved therapeutic potential. Conventional dosage forms, such as tablets, capsules, and injections, are limited when exploited for advanced therapeutics, such as drug targeting. To cater to these limitations, nanofibres have emerged as novel nanomaterials to provide enhanced bioavailability, targeted drug release, extended drug release profile, minimum toxicity, and reduced dosage frequency, which has indisputably improved patient adherence and compliance. This review will concern understanding the potential of drug-loaded nanofibres in drug delivery while comprehending a detailed description of their different production methods. The literature has been thoroughly reviewed to appreciate their potential in developing nanofibrous-based pharmaceutical formulations. Overall, this review has highlighted the importance, versatility, and adaptability of nanofibres in developing medicines with varied drug release kinetics. Several problems must be resolved for their full commercial realisation, such as the drug loading, the initial burst effect, the residual organic solvent, the stability of active agents, and the combined usage of new or existing biocompatible polymers. Full article

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

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17 pages, 26870 KiB

Open AccessEditor’s ChoiceReview

Carbon Fiber-Reinforced Geopolymer Composites: A Review

by Vojtěch Růžek, Ardak Mukhamedievna Dostayeva, Janusz Walter, Thomas Grab and Kinga Korniejenko

Fibers 2023, 11(2), 17; https://doi.org/10.3390/fib11020017 - 1 Feb 2023

Cited by 31 | Viewed by 6332

Abstract

The article summarizes the state of the art in carbon-reinforced geopolymers. It takes into consideration various types of matrices and types of carbon fibers (CFs). The article shows the growing importance of this composite in the investigation conducted in recent years. Today, it [...] Read more.

The article summarizes the state of the art in carbon-reinforced geopolymers. It takes into consideration various types of matrices and types of carbon fibers (CFs). The article shows the growing importance of this composite in the investigation conducted in recent years. Today, it is one of the most promising modern research areas, taking into account the decrease in the prices of CFs and their appearance on the market waste-based CFs, as well as research on new methods of producing CFs from sustainable precursors. The research methods applied in the article are critical analyses of the literature. The results of the literature analysis are discussed in a comparative context, including production methods and the influence of CFs on geopolymer properties. The potential applications for carbon fiber-reinforced geopolymer composites are shown. Additionally, the current research challenges for geopolymer composites reinforced by CFs are presented. Full article

(This article belongs to the Special Issue Carbon Fibers from Sustainable Precursors)

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28 pages, 6763 KiB

Open AccessEditor’s ChoiceArticle

Reducing Plastic in Consumer Goods: Opportunities for Coarser Wool

by Lisbeth Løvbak Berg, Ingun Grimstad Klepp, Anna Schytte Sigaard, Jan Broda, Monika Rom and Katarzyna Kobiela-Mendrek

Fibers 2023, 11(2), 15; https://doi.org/10.3390/fib11020015 - 28 Jan 2023

Cited by 11 | Viewed by 7758

Abstract

Production and use of plastic products have drastically increased during the past decades and their environmental impacts are increasingly spotlighted. At the same time, coarse wool, a by-product of meat and dairy production, goes largely unexploited in the EU. This paper asks why [...] Read more.

Production and use of plastic products have drastically increased during the past decades and their environmental impacts are increasingly spotlighted. At the same time, coarse wool, a by-product of meat and dairy production, goes largely unexploited in the EU. This paper asks why more coarse wool is not used in consumer goods, such as acoustic and sound-absorbing products, garden products, and sanitary products. This is answered through a SWOT analysis of results from a desktop study and interviews with producers of these products made from wool, as well as policy documents relating to wool, waste, textiles, and plastic. Findings show that on a product level, the many inherent properties of wool create opportunities for product development and sustainability improvements and that using the coarser wool represents an opportunity for replacing plastics in many applications as well as for innovation. This is, however, dependent on local infrastructure and small-scale enterprises, but as such, it creates opportunities for local value chains, value creation, and safeguarding of local heritage. The shift to small-scale and local resource utilization requires systemic change on several levels: Here the findings show that policy can incentivize material usage transitions, but that these tools are little employed currently. Full article

(This article belongs to the Special Issue Natural Fiber Competitiveness and Sustainability)

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23 pages, 954 KiB

Open AccessEditor’s ChoiceArticle

Natural and Sustainable? Consumers’ Textile Fiber Preferences

by Anna Schytte Sigaard and Kirsi Laitala

Fibers 2023, 11(2), 12; https://doi.org/10.3390/fib11020012 - 26 Jan 2023

Cited by 20 | Viewed by 17655

Abstract

Textile fibers have become a major issue in the debate on sustainable fashion and clothing consumption. While consumers are encouraged to choose more sustainable and circular textile materials, studies have indicated that a reduction in production and consumption has the greatest potential to [...] Read more.

Textile fibers have become a major issue in the debate on sustainable fashion and clothing consumption. While consumers are encouraged to choose more sustainable and circular textile materials, studies have indicated that a reduction in production and consumption has the greatest potential to reduce the total environmental impact. This can be considered an ecocentric perspective with a focus on degrowth as opposed to a technocentric view where new technologies are expected to solve environmental problems while economic growth continues. Based on a survey in Norway (N = 1284), we investigate how the techno- and ecocentric perspectives impact Norwegian consumers’ fiber preferences and perceptions and the corresponding effects on their clothing consumption. We found that the majority of consumers preferred natural fibers compared to synthetic materials. This contradicts current market practices and the recommendations by material sustainability comparison tools such as the Higg Material Sustainability Index (MSI), where many synthetics receive better ratings than natural fibers. We also found that perceptions of high sustainability regarding fibers were negatively correlated with reduced consumption. Our study suggests that a continued focus on material substitution and other technological measures for reducing climate change will impede the move toward sustainability in the textile sector. Full article

(This article belongs to the Special Issue Natural Fiber Competitiveness and Sustainability)

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17 pages, 6739 KiB

Open AccessEditor’s ChoiceArticle

Production and 3D Printing of a Nanocellulose-Based Composite Filament Composed of Polymer-Modified Cellulose Nanofibrils and High-Density Polyethylene (HDPE) for the Fabrication of 3D Complex Shapes

by Feras Dalloul, Jakob Benedikt Mietner and Julien R. G. Navarro

Fibers 2022, 10(10), 91; https://doi.org/10.3390/fib10100091 - 21 Oct 2022

Cited by 19 | Viewed by 4309

Abstract

This work aims to produce a 3D-printable bio-based filament composed of high-density polyethylene (HDPE) and chemically modified cellulose nanofibrils. Printing using HDPE as a raw material is challenging due to its massive shrinkage and warping problems. This paper presents a new method to [...] Read more.

This work aims to produce a 3D-printable bio-based filament composed of high-density polyethylene (HDPE) and chemically modified cellulose nanofibrils. Printing using HDPE as a raw material is challenging due to its massive shrinkage and warping problems. This paper presents a new method to overcome those difficulties by enhancing the mechanical properties and achieving better print quality. This was achieved using modified cellulose nanofibrils (CNFs) as fillers. Firstly, CNF was converted to a CNF-based macroinitiator through an esterification reaction, followed by a surface-initiated single-electron transfer living radical polymerization (SI-SET-LRP) of the hydrophobic monomer stearyl acrylate. Poly stearyl acrylate-grafted cellulose nanofibrils, CNF-PSAs, were synthesized, purified and characterized with ATR-FTIR, ¹³C CP-MAS NMR, FE-SEM and water contact angle measurements. A composite was successfully produced using a twin-screw extruder with a CNF-PSA content of 10 wt.%. Mechanical tests were carried out with tensile testing. An increase in the mechanical properties, up to 23% for the Young’s modulus, was observed. A morphologic analysis also revealed the good matrix/CNF compatibility, as no CNF aggregates could be observed. A reduction in the warping behavior for the composite filament compared to HDPE was assessed using a circular arc method. The 3D printing of complex objects using the CNF-PSA/HDPE filament resulted in better print quality when compared to the object printed with neat HDPE. Therefore, it could be concluded that CNF-PSA was a suitable filler for the reinforcement of HDPE, thus, rendering it suitable for 3D printing. Full article

(This article belongs to the Topic Cellulose and Cellulose Derivatives)

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22 pages, 1062 KiB

Open AccessEditor’s ChoiceReview

Factors of Weave Estimation and the Effect of Weave Structure on Fabric Properties: A Review

by Most. Setara Begum and Rimvydas Milašius

Fibers 2022, 10(9), 74; https://doi.org/10.3390/fib10090074 - 30 Aug 2022

Cited by 32 | Viewed by 12773

Abstract

This paper provides a review of recent studies on the weave factor along with the effect of weave parameters and particularly the weave structure on various properties of woven fabric. The weave structure can be considered as one of the prime parameters that [...] Read more.

This paper provides a review of recent studies on the weave factor along with the effect of weave parameters and particularly the weave structure on various properties of woven fabric. The weave structure can be considered as one of the prime parameters that contributes to the dominant physical and qualitative properties of the woven fabric. This study analyzed not only the parameters that significantly influence the properties of the woven fabric, but also the weave factors for the estimation of the weave that were proposed by earlier scientists. This review paper highlights the impact of weave structure on the physical and mechanical, thermo-physiological and comfort properties, and some special application properties of woven fabrics. This work seeks to serve as a future reference for related research. Full article

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

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15 pages, 8391 KiB

Open AccessEditor’s ChoiceArticle

Simple Synthesis of Fe₃O₄@-Activated Carbon from Wastepaper for Dispersive Magnetic Solid-Phase Extraction of Non-Steroidal Anti-Inflammatory Drugs and Their UHPLC–PDA Determination in Human Plasma

by Vincenzo Ferrone, Pantaleone Bruni, Valentino Canale, Leonardo Sbrascini, Francesco Nobili, Giuseppe Carlucci and Stefania Ferrari

Fibers 2022, 10(7), 58; https://doi.org/10.3390/fib10070058 - 1 Jul 2022

Cited by 7 | Viewed by 4396

Abstract

In the present society, the recycling and reuse of valuable substances are of utmost importance for economic and environmental purposes. At the same time, there is a pressing need to develop new methods to protect the ecosystem from many human activities, including those [...] Read more.

In the present society, the recycling and reuse of valuable substances are of utmost importance for economic and environmental purposes. At the same time, there is a pressing need to develop new methods to protect the ecosystem from many human activities, including those that have contributed to an ever-increasing presence of pharmaceutical pollutants. In this study, a straightforward approach that applies a magnetic carbon composite for the effective removal of NSAIDs from biological fluids is reported. The composite was produced by recycling wasted handkerchiefs, to provide cellulose to the reactive system and then transformed into carbon via calcination at high temperature. The morphological and structural features of the prepared “Fe₃O₄@-activated carbon” samples were investigated via thermal analysis, X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Magnetic solid-state extraction was carried out to reveal the adsorption capabilities of the magnetic carbon composite and then combined with UHPLC–PDA for the determination and quantification of five NSAIDs (furprofen, indoprofen, ketoprofen, flurbiprofen, and indomethacin). The method developed herein proved to be fast and accurate. The adsorbent could be reused for up to 10 cycles, without any decrease in performance; thus, it contributes to an intelligent and sustainable economic strategy projected toward minimal waste generation. Full article

(This article belongs to the Special Issue Carbon Fibers from Sustainable Precursors)

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22 pages, 13230 KiB

Open AccessEditor’s ChoiceArticle

Multifunctional Material Extrusion 3D-Printed Antibacterial Polylactic Acid (PLA) with Binary Inclusions: The Effect of Cuprous Oxide and Cellulose Nanofibers

by Markos Petousis, Nectarios Vidakis, Nikolaos Mountakis, Vassilis Papadakis, Sotiria Kanellopoulou, Aikaterini Gaganatsiou, Nikolaos Stefanoudakis and John Kechagias

Fibers 2022, 10(6), 52; https://doi.org/10.3390/fib10060052 - 10 Jun 2022

Cited by 51 | Viewed by 4580

Abstract

In this work, we present an effective process easily adapted in industrial environments for the development of multifunctional nanocomposites for material extrusion (MEX) 3D printing (3DP). The literature is still very limited in this field, although the interest in such materials is constantly [...] Read more.

In this work, we present an effective process easily adapted in industrial environments for the development of multifunctional nanocomposites for material extrusion (MEX) 3D printing (3DP). The literature is still very limited in this field, although the interest in such materials is constantly increasing. Nanocomposites with binary inclusions were prepared and investigated in this study. Polylactic acid (PLA) was used as the matrix material, and cuprous oxide (Cu₂O) and cellulose nanofibers (CNF) were used as nanoadditives introduced in the matrix material to enhance the mechanical properties and induce antibacterial performance. Specimens were built according to international standards with a thermomechanical process. Tensile, flexural, impact, and microhardness tests were conducted. The effect on the thermal properties of the matrix material was investigated through thermogravimetric analysis, and Raman spectroscopic analysis was conducted. The morphological characteristics were evaluated with atomic force microscopy (AFM), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDS) analyses. The antibacterial performance of the prepared nanomaterials was studied against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) bacteria, with a screening agar well diffusion method. All nanocomposites prepared exhibited biocidal properties against the bacteria tested. The tested PLA/1.0 CNF/0.5 Cu₂O material had 51.1% higher tensile strength and 35.9% higher flexural strength than the pure PLA material. Full article

(This article belongs to the Collection Feature Papers in Fibers)

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22 pages, 9453 KiB

Open AccessEditor’s ChoiceArticle

Influence of Different Surfactants on Carbon Fiber Dispersion and the Mechanical Performance of Smart Piezoresistive Cementitious Composites

by Athanasia K. Thomoglou, Maria G. Falara, Fani I. Gkountakou, Anaxagoras Elenas and Constantin E. Chalioris

Fibers 2022, 10(6), 49; https://doi.org/10.3390/fib10060049 - 31 May 2022

Cited by 35 | Viewed by 4413

Abstract

This experimental study presents the effect of different surfactants on micro-scale carbon fiber (CFs) distribution into carbon fiber reinforced cement-based composites (CFRC) in terms of flexural and compressive strength, stiffness, flexural toughness, and strain-sensing ability. Conducting a narrative review of the literature focusing [...] Read more.

This experimental study presents the effect of different surfactants on micro-scale carbon fiber (CFs) distribution into carbon fiber reinforced cement-based composites (CFRC) in terms of flexural and compressive strength, stiffness, flexural toughness, and strain-sensing ability. Conducting a narrative review of the literature focusing on the fibers’ separation, this paper follows a methodology introducing a combination of mechanical and chemical carbon fibers dispersion, as well as the different mixing processes (wet or dry). Three types of surfactants: Carboxymethyl cellulose (CMC), cellulose nanocrystal (CNC), and superplasticizer (SP), were applied to evaluate the CFs distribution in the cement paste matrix. Compressive and flexural strength, modulus of elasticity, and ductility of the cement-based composites (CFRC) reinforced with 0.5 wt.% CFs were investigated by three-point bending and compressive tests; flexure tests were also conducted on notched 20 × 20 × 80 mm specimens using the Linear Elastic Fracture Mechanics (L.E.F.M.) theory. Moreover, the electrical conductivity and the piezoresistive response were determined by conducting electrical resistance measurements and applying compressive loading simultaneously. The results clearly reveal that the CFs/SP solution or the CFs’ dry incorporation led to a significant enhancement of flexural strength by 32% and 23.7%, modulus of elasticity by 30% and 20%, and stress-sensing ability by 20.2% and 18.2%, respectively. Although the wet mixing method exhibits improved mechanical and electrical conductivity performance, constituting an adequate strain and crack sensor, the authors propose dry mixing as the most economical method, in addition to the enhanced mechanical and electrical responses. The authors recommend an effective method for structural health monitoring systems combining an economical CFs insertion in cementitious smart sensors with great mechanical and self-sensing responses. Full article

(This article belongs to the Special Issue Fiber-Reinforced Polymers and Fiber-Reinforced Cement-Based Mortars in Repair/Strengthening Methods of Masonry and Reinforced Concrete Structural Members)

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16 pages, 3466 KiB

Open AccessEditor’s ChoiceReview

Electromagnetic Interference Shielding with Electrospun Nanofiber Mats—A Review of Production, Physical Properties and Performance

by Tomasz Blachowicz, Andreas Hütten and Andrea Ehrmann

Fibers 2022, 10(6), 47; https://doi.org/10.3390/fib10060047 - 24 May 2022

Cited by 22 | Viewed by 5299

Abstract

With a steadily increasing number of machines and devices producing electromagnetic radiation, especially, sensitive instruments as well as humans need to be shielded from electromagnetic interference (EMI). Since ideal shielding materials should be lightweight, flexible, drapable, thin and inexpensive, textile fabrics belong to [...] Read more.

With a steadily increasing number of machines and devices producing electromagnetic radiation, especially, sensitive instruments as well as humans need to be shielded from electromagnetic interference (EMI). Since ideal shielding materials should be lightweight, flexible, drapable, thin and inexpensive, textile fabrics belong to the often-investigated candidates to meet these expectations. Especially, electrospun nanofiber mats are of significant interest since they can not only be produced relatively easily and cost efficiently, but they also enable the embedding of functional nanoparticles in addition to thermal or chemical post-treatments to reach the desired physical properties. This paper gives an overview of recent advances in nanofiber mats for EMI shielding, discussing their production, physical properties and typical characterization techniques. Full article

(This article belongs to the Collection Feature Papers in Fibers)

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16 pages, 3330 KiB

Open AccessEditor’s ChoiceReview

Fiber-Reinforced Polymer Composites in the Construction of Bridges: Opportunities, Problems and Challenges

by Paweł Grzegorz Kossakowski and Wiktor Wciślik

Fibers 2022, 10(4), 37; https://doi.org/10.3390/fib10040037 - 18 Apr 2022

Cited by 28 | Viewed by 13457

Abstract

In this review, we discuss the basic issues related to the use of FRP (fiber-reinforced polymer) composites in bridge construction. This modern material is presented in detail in terms of the possibility of application in engineering structures. A general historical outline of the [...] Read more.

In this review, we discuss the basic issues related to the use of FRP (fiber-reinforced polymer) composites in bridge construction. This modern material is presented in detail in terms of the possibility of application in engineering structures. A general historical outline of the use and development of modern structural materials, such as steel and concrete, is included to introduce composites as a novel material in engineering, and the most important features and advantages of polymers as a construction material are characterized. We also compare FRP to basic structural materials, such as steel and concrete, which enables estimation of the effectiveness of using of FRP polymers as structural material in different applications. The first bridges made of FRP composites are presented and analyzed in terms of applied technological solutions. Examples of structural solutions for deck slabs, girders and other deck elements made of FRP composites are discussed. Particular attention is paid to the systems of deck slabs, especially those composed of pultruded profiles, sandwich panels and hybrid decks. The disadvantages of composites, as well as barriers and limitations in their application in engineering practice, are presented. Exemplary analyses of the costs of construction, maintenance and demolition of FRP composite bridges are presented and compared with the corresponding costs of concrete and steel bridges. The directions of development of composite bridge structures and the greatest challenges facing engineers and constructors in the coming years are discussed. Full article

(This article belongs to the Special Issue Fiber Composite Process)

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