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Fiber-Reinforced Polymer Composites: Progress and Prospects
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Fiber-Reinforced Polymer Composites: Progress and Prospects

A special issue of Polymers (ISSN 2073-4360). This special issue belongs to the section "Polymer Composites and Nanocomposites".

Deadline for manuscript submissions: 31 May 2026 | Viewed by 32488

Special Issue Editor

Prof. Dr. Chi-Wai Kan

E-Mail Website
Guest Editor
School of Fashion and Textiles, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
Interests: textile materials and textile processing; textile coloration and finishing; surface treatment of textile materials; textile product evaluation; textile testing instrumentation; safety and health management; environmental management
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Fiber-reinforced polymer composites (FRPs) are materials that consist of a polymer matrix reinforced with fibers. These composites offer a wide range of mechanical, thermal, and chemical properties, making them attractive for various applications across industries such as aerospace, automotive, construction, and sports equipment. Over the years, significant progress has been made in the development and implementation of FRPs, and they continue to hold promising prospects.

For this Special Issue, we invite academic researchers and industrial experts to submit their research findings covering different developments in FRPs. Topics in this Special Issue will include articles related to, but not limited to, the following: (i) manufacturing techniques; (ii) fiber development; (iii) matrix materials; (iv) tailored properties; (v) light-weight structures; (vii) corrosion resistance; (viii) design flexibility; and (ix) sustainability implications.

Prof. Dr. Chi-Wai Kan
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 250 words) can be sent to the Editorial Office for assessment.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • fiber-reinforced polymer composites
  • manufacturing technique
  • fiber development
  • matrix materials
  • tailored properties
  • light-weight structure
  • design flexibility and sustainability

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Published Papers (25 papers)

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Research

17 pages, 17876 KB  
Article
Tensile Behavior of Carbon Fibers Impregnated with Thermoplastics Using Coextrusion Technique
by Victor V. Tcherdyntsev, Andrey A. Stepashkin and Alnis A. Veveris
Polymers 2026, 18(5), 651; https://doi.org/10.3390/polym18050651 - 6 Mar 2026
Viewed by 316
Abstract
To increase printing speed and quality, a route consisting of using two sequential coextruders to form impregnated fiber immediately before feeding it to the printer. Such an approach, aimed at allowing the use of the most common industrial 12K carbon fibers for additive [...] Read more.
To increase printing speed and quality, a route consisting of using two sequential coextruders to form impregnated fiber immediately before feeding it to the printer. Such an approach, aimed at allowing the use of the most common industrial 12K carbon fibers for additive manufacturing, prevents damage to composite fibers during transportation, storage, and loading. An elaborate system was used to prepare carbon fibers impregnated with polypropylene, ethylene vinyl acetate, and their blends. The used scheme allows the production of composite fibers containing from 60 to 80 wt. % of carbon fibers. It was found that the elastic modulus of the composite fibers is close to those for raw carbon fibers and does not depend on the used polymer. It shows that the used carbon fiber path in the polymer melt and two sequential calibrating nozzles result in a high degree of orientation of the elementary filaments in the fiber at impregnation and maintain the elastic properties of the carbon fiber in the resulting composite. The tensile strength of the composite fibers depends on the polymer content in the composite fiber; the highest tensile strength was observed for fibers impregnated with ethylene vinyl acetate when increasing the coextrusion temperature up to 220 °C, which results in a composite fiber with a polymer content of 30 wt. %. A decrease in the polymer content in composite fibers results in a decrease in strength. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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32 pages, 19818 KB  
Article
An Interpretable Ensemble Machine Learning Framework for Predicting the Ultimate Flexural Capacity of BFRP-Reinforced Concrete Beams
by Sebghatullah Jueyendah and Elif Ağcakoca
Polymers 2026, 18(5), 601; https://doi.org/10.3390/polym18050601 - 28 Feb 2026
Viewed by 313
Abstract
Prediction of the ultimate moment capacity (Mu) of BFRP-reinforced concrete beams is complicated by nonlinear parameter interactions and the linear-elastic response of BFRP, reducing the accuracy of conventional design models. This study develops an optimized machine learning (ML) framework incorporating random forest, extra [...] Read more.
Prediction of the ultimate moment capacity (Mu) of BFRP-reinforced concrete beams is complicated by nonlinear parameter interactions and the linear-elastic response of BFRP, reducing the accuracy of conventional design models. This study develops an optimized machine learning (ML) framework incorporating random forest, extra trees, gradient boosting, adaboost, bagging, support vector regression, histogram-based gradient boosting, and ensemble voting and stacking strategies for reliable prediction of the Mu of BFRP-reinforced concrete beams. A comprehensive database of material, geometric, reinforcement, and BFRP mechanical parameters was analyzed, and model performance was evaluated using an 80/20 train–test split and 10-fold cross-validation based on R2, RMSE, MAE, and MAPE. The stacking regressor demonstrated superior predictive performance, achieving an R2 of 0.999 (RMSE = 0.590) in training and an R2 of 0.988 (RMSE = 2.487) in testing, indicating excellent robustness and strong generalization capability in predicting Mu. Furthermore, interpretability analyses based on SHAP, PDP, ALE, and ICE demonstrate that span length (L) and beam depth (h) constitute the governing parameters in the prediction of Mu. Unlike prior studies focused mainly on predictive accuracy, this work proposes an optimized and interpretable stacking ensemble framework that integrates explainable AI with classical flexural mechanics for physically consistent and reliable prediction of the ultimate moment capacity of BFRP-reinforced concrete beams. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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20 pages, 5832 KB  
Article
Delamination Mode I Analysis on Thin Stitch Fiberglass Composite
by Manuel Alejandro Lira-Martínez, Marianggy Gomez, Delfino Cornejo-Monroy, Jose Omar Davalos and Luis Asunción Pérez-Domínguez
Polymers 2026, 18(5), 572; https://doi.org/10.3390/polym18050572 - 27 Feb 2026
Viewed by 315
Abstract
Delamination is a major failure Mode in laminated composites, typically triggered by premature interlaminar matrix cracking and leading to severe structural degradation. To address this, various through-thickness reinforcement strategies have been explored, including three-dimensional woven architecture. Although these designs significantly improve delamination resistance, [...] Read more.
Delamination is a major failure Mode in laminated composites, typically triggered by premature interlaminar matrix cracking and leading to severe structural degradation. To address this, various through-thickness reinforcement strategies have been explored, including three-dimensional woven architecture. Although these designs significantly improve delamination resistance, their industrial adoption stays limited due to reproducibility challenges and the high cost and operational complexity of advanced manufacturing systems needed for controlled through-thickness reinforcement. This study investigates an alternative interlaminar reinforcement method, through-thickness stitching, aimed at enhancing Mode-I delamination resistance of a commercial fiberglass laminate without changing its native architecture. Composites were manufactured using a low-viscosity epoxy infusion system (MAX 1618 A/B) and a [0/90] biaxial fiberglass fabric. An eight-filament polyethylene thread (Ø = 0.12 mm) was introduced in predefined stitch architectures consisting of three longitudinal patterns having two, three, and five continuous stitch lines, referred to as AV, BV and CV samples, respectively. Results show that stitching highly increases Mode-I interlaminar fracture toughness GIC by 0.3808, 0.4152 and 0.5192 kJ/m2 for AV, BV and CV respectively, compared to 0.0265 kJ/m2 for the unstitched composite O, highlighting the strong influence of stitch orientation and spacing on interlaminar performance. But scanning electron microscopy revealed added failure mechanisms in stitched specimens, including localized fiber misalignment of up to 33° and resin-rich regions approximately 0.6 mm in length, suggesting that while stitching enhances delamination resistance, it may also influence other mechanical properties. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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35 pages, 11024 KB  
Article
A Comparison of Damages Occurring on the Bonding Surface of Carbon and Glass Fiber-Reinforced Polymer Composite Materials Used in Wind Turbine Blades and Marine Vessels via Three-Point Bending and Four-Point Bending Tests
by Dudu Mertgenç Yoldaş and Gürcan Atakök
Polymers 2026, 18(4), 481; https://doi.org/10.3390/polym18040481 - 14 Feb 2026
Viewed by 361
Abstract
The aim of this study is to experimentally evaluate the damage mechanisms occurring in the adhesive-bonded regions of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites, which are widely used in marine and offshore wind turbine applications, under environmental conditions. In [...] Read more.
The aim of this study is to experimentally evaluate the damage mechanisms occurring in the adhesive-bonded regions of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites, which are widely used in marine and offshore wind turbine applications, under environmental conditions. In particular, this study focuses on the degradation caused by long-term seawater exposure and its effects on the bending behavior and load-carrying capacity of adhesive joints. For this purpose, the specimens were prepared in accordance with ASTM D5868-01, using 7-layer GFRP and 8-layer CFRP laminates. Single-lap adhesive joints were fabricated. To simulate marine environmental conditions, the single-lap adhesive joints were immersed in natural seawater obtained from the Aegean Sea (22 °C temperature and 3.3–3.7% salinity) for 1, 2, and 3 months in separate containers. Three-point bending (3PB) tests were performed on specimens representing marine applications, while four-point bending (4PB) tests were conducted on specimens representing offshore wind turbine blade structures. The results quantitatively revealed the influence of seawater on adhesive-bonded composite joints. In 3PB tests, the reductions in the Young’s modulus of GFRP specimens after 1, 2, and 3 months of exposure were measured as 5.94%, 8.90%, and 12.98%, respectively. For CFRP specimens, degradation was more limited, with corresponding reductions of 1.28%, 3.39%, and 3.74%. A similar trend was observed in 4PB tests representing offshore wind turbine applications, where GFRP joints exhibited modulus reductions of 3.15%, 6.42%, and 9.45%, while CFRP joints showed reductions of 1.29%, 2.62%, and 3.48% for the same exposure durations. Overall, the findings demonstrate that CFRP composites exhibit more stable mechanical behavior under environmental exposure, whereas GFRP structures undergo more pronounced performance losses, particularly in moisture- and salt-rich environments. These results highlight the critical importance of material selection for long-term durability in offshore composite structures. The outcomes of this study contribute to a better understanding of the damage processes occurring in composite adhesive joints under environmental conditions and provide a scientific basis for developing more reliable design and material selection strategies in both the marine and wind energy sectors. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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36 pages, 3186 KB  
Article
Structural Analysis and Mechanical Performance of Industrial Conveyor Flight Bars Manufactured with Epoxy Matrix Composites Reinforced by Glass, Carbon, and Kevlar Fibers
by Antonio Henrique da Silva Bitencourt Junior, Maurício Maia Ribeiro, Douglas Santos Silva, Raí Felipe Pereira Junio, Sergio Neves Monteiro and Jean da Silva Rodrigues
Polymers 2026, 18(4), 433; https://doi.org/10.3390/polym18040433 - 9 Feb 2026
Viewed by 456
Abstract
Industrial conveyor systems commonly use steel flight bars, which can account for nearly 50% of the total system mass and significantly affect energy consumption. This study investigates epoxy matrix composites reinforced with glass, carbon, and Kevlar fibers as lightweight alternatives to steel flight [...] Read more.
Industrial conveyor systems commonly use steel flight bars, which can account for nearly 50% of the total system mass and significantly affect energy consumption. This study investigates epoxy matrix composites reinforced with glass, carbon, and Kevlar fibers as lightweight alternatives to steel flight bars. A multiscale analytical approach combining micromechanics, Classical Laminate Theory (CLT), and ply-level failure criteria is applied to evaluate the structural response under an industrial bending moment of 342.02 N·m. Tensile tests on vacuum-infused woven glass/epoxy laminates are used to validate micromechanical assumptions and calibrate elastic properties. Ply-wise analysis shows that carbon/epoxy laminates exhibit the lowest longitudinal stresses (≈43 MPa), followed by Kevlar/epoxy (≈53 MPa) and glass/epoxy (≈95 MPa), all well below their respective strength limits. Replacing steel flight bars (4.64 t) with composite alternatives reduces the moving mass to 0.68–0.82 t, corresponding to an 82–85% reduction. This mass reduction significantly lowers the required mechanical power, resulting in an estimated annual energy saving of R$ 8812.80 under continuous operation. Overall, the results demonstrate that polymer-matrix composite flight bars are structurally safe and energetically advantageous, with carbon/epoxy providing the highest mechanical efficiency. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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19 pages, 2016 KB  
Article
Structure–Property Relationships of Boron Nitride-Reinforced Glass Fiber/Epoxy Laminated Composites
by Sakine Kıratlı and Selçuk Özmen
Polymers 2026, 18(3), 372; https://doi.org/10.3390/polym18030372 - 30 Jan 2026
Viewed by 458
Abstract
Advances in modern industry largely depend on the development of high-performance materials. In this study, the influence of hexagonal boron nitride (h-BN) filler on the performance of glass fiber/epoxy laminates was systematically investigated. Composites containing h-BN with different particle sizes (65–75 nm and [...] Read more.
Advances in modern industry largely depend on the development of high-performance materials. In this study, the influence of hexagonal boron nitride (h-BN) filler on the performance of glass fiber/epoxy laminates was systematically investigated. Composites containing h-BN with different particle sizes (65–75 nm and 790 nm) and contents (0.2 and 0.4 wt.%) were fabricated, and their mechanical (tensile, in-plane shear, hardness, impact), thermal (Differential Scanning Calorimetry, DSC), electrical (volume resistivity), and spectroscopic (Fourier Transform Infrared Spectroscopy, FTIR) properties were examined. The results demonstrated that specimens with 65–75 nm h-BN at 0.2 wt.% exhibited the highest tensile and shear strengths, whereas those with 790 nm h-BN at 0.4 wt.% showed superior impact resistance and hardness. DSC analyses revealed that h-BN addition increased the glass transition temperature (Tg), while FTIR confirmed interfacial interactions between h-BN and the epoxy matrix. Electrical measurements indicated that h-BN preserved the insulating nature of the composites, with only limited reductions in resistivity observed at higher contents of larger particles due to morphological effects. Overall, these findings highlight that h-BN filler enhances load transfer efficiency, thermal stability, and mechanical reliability, offering significant potential for applications requiring multifunctional performance, such as aerospace, marine, and electrical and electronic insulation systems. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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23 pages, 6872 KB  
Article
Experimental Evaluation of Tensile Behavior and Hygrothermal Degradation of Glass Fiber Composites
by Ciprian Ionuț Morăraș, Viorel Goanță, Lucia Raluca Maier, Teodor Adrian Badea and Paul Doru Bârsănescu
Polymers 2026, 18(2), 277; https://doi.org/10.3390/polym18020277 - 20 Jan 2026
Viewed by 309
Abstract
Glass fiber-reinforced polymer (GFRP) composites are widely used in structural applications due to their high specific strength and durability; however, their mechanical performance strongly depends on fiber architecture and environmental exposure. This study evaluates the mechanical behavior and moisture-induced degradation of GFRP laminates [...] Read more.
Glass fiber-reinforced polymer (GFRP) composites are widely used in structural applications due to their high specific strength and durability; however, their mechanical performance strongly depends on fiber architecture and environmental exposure. This study evaluates the mechanical behavior and moisture-induced degradation of GFRP laminates through tensile tests, impact tests, dynamic mechanical analysis (DMA), and thermomechanical analysis (TMA) performed on a bi-directional glass–epoxy GFRP laminate ([0°/90°]). Tensile tests revealed a maximum longitudinal strength of 369 MPa in dry specimens, while water immersion for up to 21 days led to a significant reduction in tensile strength, from 207 MPa to 63 MPa, in diagonally cut specimens. Impact tests conducted at 12 J showed larger displacements in specimens cut along directions not aligned with the fibers, indicating matrix-dominated behavior. Dynamic mechanical analysis demonstrated strong dependence of stiffness on fiber orientation, with storage modulus values decreasing by approximately 45% in 45° specimens compared with the principal directions, while the glass transition temperature remained within 59–62 °C. Thermomechanical analysis confirmed an increase in the coefficient of thermal expansion after aging, from 205.6 to 291.65 µm/(m·°C) below Tg. These results provide insights into the structure–property–environment relationships governing the durability of GFRP composites and support the optimization of their design for long-term polymer-based applications. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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22 pages, 5176 KB  
Article
Experimental Investigation of Shear Connection in Precast Concrete Sandwich Panels with Reinforcing Ribs
by Jan Macháček, Eliška Kafková, Věra Kabíčková and Tomáš Vlach
Polymers 2026, 18(2), 200; https://doi.org/10.3390/polym18020200 - 11 Jan 2026
Viewed by 447
Abstract
This paper presents an experimental investigation of the shear connection between outer layers of lightweight precast concrete sandwich panels (PCSP) made of high-performance concrete (HPC). The shear-transfer mechanism is based on reinforcing ribs composed of rigid polymer-based thermal insulation combined with carbon-fibre-reinforced polymer [...] Read more.
This paper presents an experimental investigation of the shear connection between outer layers of lightweight precast concrete sandwich panels (PCSP) made of high-performance concrete (HPC). The shear-transfer mechanism is based on reinforcing ribs composed of rigid polymer-based thermal insulation combined with carbon-fibre-reinforced polymer (CFRP) shear reinforcement. A total of seven full-scale sandwich panels were tested in four-point bending. This study compares three types of rigid thermal insulation used in the shear ribs—Purenit, Compacfoam CF400, and Foamglass F—and investigates the influence of the amount of CFRP shear reinforcement on the structural behavior of the panels. Additional specimens were used to evaluate the effect of reinforcing ribs and of polymer-based thermal insulation placed between the ribs. The experimental results show that panels with shear ribs made of Purenit and Compacfoam CF400 achieved significantly higher load-bearing capacities compared to Foamglass F, which proved unsuitable due to its brittle behavior. Increasing the amount of CFRP shear reinforcement increased the load-bearing capacity but had a limited effect on panel stiffness. The experimentally determined composite interaction coefficient ranged around α ≈ 0.03, indicating partial shear interaction between the outer concrete layers. A simplified strut-and-tie model was applied to predict the load-bearing capacity and showed conservative agreement with experimental results. The findings demonstrate that polymer-based materials, particularly CFRP reinforcement combined with rigid polymer insulation, enable efficient shear transfer without thermal bridging, making them suitable for lightweight and thermally efficient precast concrete sandwich panels. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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33 pages, 12059 KB  
Article
Determination of Mechanical Properties of Single and Double-Layer Intraply Hybrid Composites Manufactured by Hand Lay-Up Method
by Mohsen Shams and Ferit Cakir
Polymers 2026, 18(2), 188; https://doi.org/10.3390/polym18020188 - 9 Jan 2026
Cited by 1 | Viewed by 559
Abstract
This study experimentally evaluates the mechanical and microstructural performance of single- and double-layer intraply hybrid composite (IRC) laminates produced using the hand lay-up method, focusing on Glass–Aramid (GA), Aramid–Carbon (AC), and Carbon–Glass (CG) configurations. Tensile, flexural, compressive, and density tests were conducted in [...] Read more.
This study experimentally evaluates the mechanical and microstructural performance of single- and double-layer intraply hybrid composite (IRC) laminates produced using the hand lay-up method, focusing on Glass–Aramid (GA), Aramid–Carbon (AC), and Carbon–Glass (CG) configurations. Tensile, flexural, compressive, and density tests were conducted in accordance with relevant ASTM standards to assess the influence of hybrid type and layer number under field-representative manufacturing conditions. Microstructural investigations were performed using optical microscopy and scanning electron microscopy (SEM) to identify fabrication-induced imperfections and their relationship to mechanical behavior. The results demonstrate that increasing the laminate configuration from single to double layer significantly enhances mechanical performance across all hybrid types. Double-layer AC laminates exhibited the highest tensile strength (330.4 MPa) and Young’s modulus (11.93 GPa), corresponding to improvements of approximately 85% and 59%, respectively, compared to single-layer counterparts. In flexural loading, the highest strength was observed in double-layer CG laminates (97.14 MPa), while compressive strength was maximized in double-layer AC laminates (34.01 MPa), indicating improved stability and resistance to compression-driven failure. Statistical analysis confirmed that layer number is the dominant parameter governing mechanical response, exceeding the influence of hybrid configuration alone. Microstructural observations revealed fiber misorientation, incomplete resin impregnation, and localized voids inherent to manual fabrication. However, these imperfections were consistently distributed across all specimens and did not obscure comparative mechanical trends. Coefficients of variation generally remained below 10%, indicating acceptable repeatability despite non-ideal manufacturing conditions. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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17 pages, 7322 KB  
Article
Development of 3D Printing Filament from Poly(Lactic Acid) and Cassava Pulp Composite with Epoxy Compatibilizer
by Thidarat Kanthiya, Pattraporn Changsuwan, Krittameth Kiattipornpithak, Pornchai Rachtanapun, Sarinthip Thanakkasaranee, Pensak Jantrawut, Nuttapol Tanadchangsaeng, Patnarin Worajittiphon, Thorsak Kittikorn and Kittisak Jantanasakulwong
Polymers 2025, 17(23), 3228; https://doi.org/10.3390/polym17233228 - 4 Dec 2025
Cited by 1 | Viewed by 744
Abstract
A 3D printing filament was fabricated from poly(lactic acid) (PLA), cassava pulp (CP), and epoxy using a twin-screw extruder. Several bio-composites were synthesized by varying the amount of epoxy (0.5, 1.0, 3.0, 5.0, and 10.0 wt.%). The size of the CP fibers significantly [...] Read more.
A 3D printing filament was fabricated from poly(lactic acid) (PLA), cassava pulp (CP), and epoxy using a twin-screw extruder. Several bio-composites were synthesized by varying the amount of epoxy (0.5, 1.0, 3.0, 5.0, and 10.0 wt.%). The size of the CP fibers significantly affected the surface quality, filament diameter, and mechanical properties of the final product. The smallest fiber size (45 µm) provided a smooth surface and consistent diameter. Incorporating 1 wt.% of epoxy into PLA/CP enhanced the tensile strength (56.6 MPa), elongation at break (6.2%), and hydrophobicity of the composite. The composite mechanical properties deteriorated at epoxy contents above 1 wt.% due to the amplified plasticizer effect of excessive epoxy. The optimized PLA/CP/epoxy formulation was used to generate the 3D filament. The resultant filament displayed a tensile strength of 64.6 MPa and elongation at break of 9.8%, attributed to the fine morphology achieved via thorough mixing provided by the twin-screw extruder. Epoxide-mediated crosslinking between PLA and CP enabled the development of a novel 3D printing filament with excellent mechanical properties. This research illustrates how agricultural residues can be upcycled into high-performance biomaterials with innovation in sustainable manufacturing, inclusive economic growth, reducing reliance on petroleum-based plastics and thus providing benefits regarding human health, climate change mitigation, plastic in the ocean, and environmental impacts. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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23 pages, 3685 KB  
Article
Ballistic Performance of Raffia Fabric-Reinforced Epoxy Composites as an Intermediate Layer in Multilayered Armor Systems
by Douglas Santos Silva, Raí Felipe Pereira Junio, Leticia dos Santos Aguilera, Sergio Neves Monteiro and Marcelo Henrique Prado da Silva
Polymers 2025, 17(21), 2827; https://doi.org/10.3390/polym17212827 - 23 Oct 2025
Cited by 1 | Viewed by 949
Abstract
This study investigates the ballistic performance of epoxy matrix composites reinforced with raffia fabric, aiming to evaluate their potential as the second layer in multilayered armor systems (MAS), replacing conventional synthetic aramid (Kevlar™) laminates. Composite plates with different volumetric fractions of raffia fabric [...] Read more.
This study investigates the ballistic performance of epoxy matrix composites reinforced with raffia fabric, aiming to evaluate their potential as the second layer in multilayered armor systems (MAS), replacing conventional synthetic aramid (Kevlar™) laminates. Composite plates with different volumetric fractions of raffia fabric (10, 20, and 30%) were manufactured and integrated with a ceramic front layer (Al2O3/Nb2O5) in MAS structures, which were then subjected to ballistic impact tests using high-energy 7.62 mm caliber ammunition. The backface signature (indentation depth) measured in ballistic clay, used as a human body simulant, showed that only the 10% raffia-reinforced composite (ER10) met the National Institute of Justice (NIJ 0101.06) safety threshold of 44 mm. Higher raffia contents (20% and 30%) led to increased indentation, compromising ballistic integrity. Scanning electron microscopy (SEM) of the fractured surfaces revealed typical energy dissipation mechanisms, such as fiber rupture, fiber pull-out, and interfacial delamination. The results indicate that raffia fabric composites with 10% fiber content can serve as a cost-effective and sustainable alternative to Kevlar™ in personal armor applications, while maintaining compliance with ballistic protection standards. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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20 pages, 6294 KB  
Article
Corrosion Inhibition in Concrete: Synergistic Performance of Hybrid Steel-Polypropylene Fiber Reinforcement Against Marine Salt Spray
by Jianqiao Yu, Jamal A. Abdalla, Rami A. Hawileh, Xiaoyue Zhang and Zhigang Zhang
Polymers 2025, 17(19), 2645; https://doi.org/10.3390/polym17192645 - 30 Sep 2025
Cited by 2 | Viewed by 848
Abstract
In the marine salt spray environment, steel fiber reinforced concrete (SFRC) structures are often subjected to accelerated durability degradation, primarily due to chloride-induced corrosion. To address this issue, polypropylene (PP) fibers were incorporated to partially replace steel fibers in the formulation of hybrid [...] Read more.
In the marine salt spray environment, steel fiber reinforced concrete (SFRC) structures are often subjected to accelerated durability degradation, primarily due to chloride-induced corrosion. To address this issue, polypropylene (PP) fibers were incorporated to partially replace steel fibers in the formulation of hybrid fiber reinforced concrete (HFRC), thereby enhancing its resistance to chloride corrosion. The results demonstrate that all HFRC mixtures achieved a compressive strength of approximately 65 MPa at 28 d. After 200 d of salt spray exposure, the compressive strength of the HFRC containing PP fibers decreased at a significantly slower rate than that of the control group (M0) incorporating sole steel fibers, with the former still meeting the high-strength concrete standard (>60 MPa). Regardless of the exposure duration to salt spray, the wave velocity of the HF series remained higher than that of M0. This suggests that the PP fibers play a significant role in preserving the matrix’s compactness, effectively mitigating deterioration caused by chloride corrosion. Furthermore, after 200 d of exposure, the peak chloride content, critical corrosion depth, and chloride diffusion coefficient of HF2 were 0.58%, 16 mm, and 1.24 × 10−12 m2/s, respectively, all of which were lower than those of the other specimens. This demonstrates that incorporating 0.3 vol% PP fibers most effectively enhances the chloride corrosion resistance of HFRC. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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31 pages, 7277 KB  
Article
Multi-Performance Evolution and Elasto-Plastic Damage Modeling of Basalt Fiber-Reinforced EPS Geopolymer Lightweight Concrete
by Feng Liang, Qingshun Yang and Jutao Tao
Polymers 2025, 17(18), 2471; https://doi.org/10.3390/polym17182471 - 12 Sep 2025
Viewed by 907
Abstract
To elucidate the multi-performance evolution mechanisms of basalt fiber-reinforced lightweight expanded polystyrene geopolymer concrete (LEGC), a two-tiered investigation was conducted. In the first part, a series of LEGC mixtures with varying volume fractions of EPS (10–40%) and basalt fiber (BF) (0.4–0.8%) were designed. [...] Read more.
To elucidate the multi-performance evolution mechanisms of basalt fiber-reinforced lightweight expanded polystyrene geopolymer concrete (LEGC), a two-tiered investigation was conducted. In the first part, a series of LEGC mixtures with varying volume fractions of EPS (10–40%) and basalt fiber (BF) (0.4–0.8%) were designed. Experimental tests were carried out to evaluate density, flowability, compressive strength, flexural strength, and splitting tensile strength. Crack propagation behavior was monitored using DIC-3D speckle imaging. Additionally, X-ray CT scanning revealed the internal clustering of EPS particles, porosity distribution, and crack connectivity within LEGC specimens, while SEM analysis confirmed the bridging effect of basalt fibers and the presence of dense matrix regions. These microstructural observations verified the consistency between the synergistic effects of EPS weakening and fiber reinforcement at the microscale and the macroscopic failure behavior. The results indicated that increasing EPS content led to reduced mechanical strength, whereas the reinforcing effect of basalt fiber followed a rising-then-falling trend. Among all specimens, LEGC20BF06 exhibited the best comprehensive performance, achieving a compressive strength of 40.87 MPa and a density of 1747.6 kg/m3, thus meeting the criteria for structural lightweight concrete. In the second part, based on the experimental data, predictive models were developed for splitting tensile and flexural strengths using compressive strength as a reference, as well as a dual-factor model incorporating EPS and fiber contents. Both models were validated and demonstrated high predictive accuracy. Furthermore, a splitting tensile elasto-plastic damage constitutive model was proposed based on composite mechanics and energy dissipation theory. The model showed excellent agreement with experimental stress–strain curves, with all fitting coefficients of determination (R2) exceeding 0.95. These findings offer robust theoretical support for the performance optimization of LEGC and its application in green construction and prefabricated structural systems. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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20 pages, 10068 KB  
Article
Effect of AF Surface Nanostructure on AFRP Interface Properties Under Temperature: A MD Simulation Study
by Zhaohua Zhang, Guowei Xia, Chunying Qiao, Longyin Qiao, Fei Gao, Qing Xie and Jun Xie
Polymers 2025, 17(15), 2024; https://doi.org/10.3390/polym17152024 - 24 Jul 2025
Viewed by 767
Abstract
The insulating rod of aramid fiber-reinforced epoxy resin composites (AFRP) is an important component of gas-insulated switchgear (GIS). Under complex working conditions, the high temperature caused by voltage, current, and external climate change becomes one of the important factors that aggravate the interface [...] Read more.
The insulating rod of aramid fiber-reinforced epoxy resin composites (AFRP) is an important component of gas-insulated switchgear (GIS). Under complex working conditions, the high temperature caused by voltage, current, and external climate change becomes one of the important factors that aggravate the interface degradation between aramid fiber (AF) and epoxy resin (EP). In this paper, molecular dynamics (MD) simulation software is used to study the effect of temperature on the interfacial properties of AF/EP. At the same time, the mechanism of improving the interfacial properties of three nanoparticles with different properties (insulator Al2O3, semiconductor ZnO, and conductor carbon nanotube (CNT)) is explored. The results show that the increase in temperature will greatly reduce the interfacial van der Waals force, thereby reducing the interfacial binding energy between AF and EP, making the interfacial wettability worse. Furthermore, the addition of the three fillers can improve the interfacial adhesion of the composite material. Among them, Al2O3 and CNT maintain a large dipole moment at high temperature, making the van der Waals force more stable and the adhesion performance attenuation less. The Mulliken charge and energy gap of Al2O3 and ZnO decrease slightly with temperature but are still higher than AF, which is conducive to maintaining good interfacial insulation performance. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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22 pages, 7210 KB  
Article
Polyethylene Storage Tanks Strengthened Externally with Fiber-Reinforced Polymer Laminates
by Ghassan Hachem, Wassim Raphael and Rafic Faddoul
Polymers 2025, 17(13), 1858; https://doi.org/10.3390/polym17131858 - 3 Jul 2025
Viewed by 1338
Abstract
Polyethylene storage tanks are widely used for storing water and chemicals due to their lightweight and corrosion-resistant properties. Despite these advantages, their structural performance under seismic conditions remains a concern, mainly because of their low mechanical strength and weak bonding characteristics. In this [...] Read more.
Polyethylene storage tanks are widely used for storing water and chemicals due to their lightweight and corrosion-resistant properties. Despite these advantages, their structural performance under seismic conditions remains a concern, mainly because of their low mechanical strength and weak bonding characteristics. In this study, a method of external strengthening using fiber-reinforced polymer (FRP) laminates is proposed and explored. The research involves a combination of laboratory testing on carbon fiber-reinforced polymer (CFRP)-strengthened polyethylene strips and finite element simulations aimed at assessing bond strength, anchorage length, and structural behavior. Results from tensile tests indicate that slippage tends to occur unless the anchorage length exceeds approximately 450 mm. To evaluate surface preparation, grayscale image analysis was used, showing that mechanical sanding increased intensity variation by over 127%, pointing to better bonding potential. Simulation results show that unreinforced tanks under seismic loads display stress levels beyond their elastic limit, along with signs of elephant foot buckling—common in thin-walled cylindrical structures. Applying CFRPs in a full-wrap setup notably reduced these effects. This approach offers a viable alternative to full tank replacement, especially in regions where cost, access, or operational constraints make replacement impractical. The applicability is particularly valuable in seismically active and densely populated areas, where rapid, non-invasive retrofitting is essential. Based on the experimental findings, a simple formula is proposed to estimate the anchorage length required for effective crack repair. Overall, the study demonstrates that CFRP retrofitting, paired with proper surface treatment, can significantly enhance the seismic performance of polyethylene tanks while avoiding costly and disruptive replacement strategies. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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18 pages, 5650 KB  
Article
Process Development for Hybrid Brake Pedals Using Compression Molding with Integrated In-Mold Assembly
by Deviprasad Chalicheemalapalli Jayasankar, Tim Stallmeister, Julian Lückenkötter, Thomas Tröster and Thorsten Marten
Polymers 2025, 17(12), 1644; https://doi.org/10.3390/polym17121644 - 13 Jun 2025
Cited by 2 | Viewed by 1146
Abstract
Currently, the need for resource efficiency and CO2 reduction is growing in industrial production, particularly in the automotive sector. To address this, the industry is focusing on lightweight components that reduce weight without compromising mechanical properties, which are essential for passenger safety. [...] Read more.
Currently, the need for resource efficiency and CO2 reduction is growing in industrial production, particularly in the automotive sector. To address this, the industry is focusing on lightweight components that reduce weight without compromising mechanical properties, which are essential for passenger safety. Hybrid designs offer an effective solution by combining weight reduction with improved mechanical performance and functional integration. This study focuses on a one-step manufacturing process that integrates forming and bonding of hybrid systems using compression molding. This approach reduces production time and costs compared to traditional methods. Conventional Post-Mold Assembly (PMA) processes require two separate steps to combine fiber-reinforced plastic (FRP) structures with metal components. In contrast, the novel In-Mold Assembly (IMA) process developed in this study combines forming and bonding in a single step. In the IMA process, glass-mat-reinforced thermoplastic (GMT) is simultaneously formed and bonded between two metal belts during compression molding. The GMT core provides stiffening and load transmission between the metal belts, which handle tensile and compressive stresses. This method allows to produce hybrid structures with optimized material distribution for load-bearing and functional performance. The process was validated by producing a lightweight hybrid brake pedal. Demonstrating its potential for efficient and sustainable automotive production, the developed hybrid brake pedal achieved a 35% weight reduction compared to the steel reference while maintaining mechanical performance under quasi-static loading Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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17 pages, 4788 KB  
Article
Preparation of Phenolic Epoxy-Based Electronic Packaging Materials with High Thermal Conductivity by Creating an Interfacial Heat Conduction Network
by Minghao Ye, Jing Jiang, Lin Zhao, Hongyu Zhu, Junjie Wang, Zicai Sun, Dewei Zhang, Ming Li and Yagang Zhang
Polymers 2025, 17(11), 1507; https://doi.org/10.3390/polym17111507 - 28 May 2025
Cited by 3 | Viewed by 1401
Abstract
As one of the most widely used packaging materials, epoxy composite (EP) offers excellent insulation properties; however, its intrinsic low thermal conductivity (TC) limits its application in high-frequency and high-power devices. To enhance the TC of EP, six highly thermally conductive inorganic fillers, [...] Read more.
As one of the most widely used packaging materials, epoxy composite (EP) offers excellent insulation properties; however, its intrinsic low thermal conductivity (TC) limits its application in high-frequency and high-power devices. To enhance the TC of EP, six highly thermally conductive inorganic fillers, namely, Al2O3, MgO, ZnO, Si3N4, h-BN, and AlN, were incorporated into the EP matrix at varying contents (60–90 wt.%). The resulting epoxy molding compounds (EMCs) demonstrated significant improvement in thermal conductivity coefficient (λ) at high filler contents (90 wt.%), ranging from 0.67 W m−1 K−1 to 1.19 W m−1 K−1, compared to the pristine epoxy composite preform (ECP, 0.36 W m−1 K−1). However, it was found that the interfacial thermal resistance (ITR) between EP and filler materials is a major hindrance restricting TC improvement. In order to address this challenge, graphene nanosheets (GNSs) and carbon nanotubes (CNTs) were introduced as additives to reduce the ITR. The experimental results indicated that CNTs were effective in enhancing the TC, with the optimized EMC achieving a λ value of 1.14 W m−1 K−1 using 60 wt.% Si3N4 + 2 wt.% CNTs. Through the introduction of a small amount of CNT (2 wt.%), the inorganic filler content was significantly reduced from 90 wt.% to 60 wt.% while still maintaining high thermal conductivity (1.14 W m−1 K−1). We propose that the addition of CNTs helps in the construction of a partial heat conduction network within the EP matrix, thereby facilitating interfacial heat transfer. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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27 pages, 8872 KB  
Article
Mechanical Behavior and Durability Performance of Concrete Reinforced with Hybrid Date Palm and Polypropylene Polymer Fibers
by Musa Adamu, Wafa Abdelmajeed Labib, Yasser E. Ibrahim and Hani Alanazi
Polymers 2025, 17(10), 1350; https://doi.org/10.3390/polym17101350 - 15 May 2025
Cited by 9 | Viewed by 1766
Abstract
Concrete faces challenges related to brittleness and crack propagation, which compromise its tensile strength and durability. Fiber reinforcement has emerged as a promising solution, yet research on hybrid systems combining natural fibers, such as date palm fiber (DPF), with synthetic polymer fibers, like [...] Read more.
Concrete faces challenges related to brittleness and crack propagation, which compromise its tensile strength and durability. Fiber reinforcement has emerged as a promising solution, yet research on hybrid systems combining natural fibers, such as date palm fiber (DPF), with synthetic polymer fibers, like polypropylene fiber (PPF), remains limited. This study investigates the mechanical and durability performance of concrete reinforced with hybrid DPF and PPF, aiming to address the gap in understanding the synergistic effects of combining natural and synthetic fibers in cementitious materials, and improving the tensile strength and crack resistance of the concrete. Both the DPF and PPF were added at varying dosages (0%, 0.25%, 0.5%, 0.75%, and 1% by weight of cement). Both DPF and PPF reduced the workability, fresh density and compressive strength of concrete, with DPF exhibiting a more significant reduction due to its higher hydrophilicity and poor compatibility with the cement matrix. A maximum reduction of 44.78% was observed in the mix containing 1% DPF and 0.5% PPF. The fibers improved tensile strength and ductility, with mixes containing up to 1% combinations of DPF and PPF showing up to a 14.6% increase in splitting tensile strength and 9.5% improvement in flexural strength compared to the control mix. However, durability was compromised—water absorption increased by up to 58% in hybrid mixes containing 1.5% total fiber content, while pore volume rose by as much as 17.5% compared to plain concrete. These increases were more pronounced with higher DPF content due to its hydrophilic nature and poor cement compatibility. This study highlights the potential of hybrid fibers to improve concrete performance while promoting eco-friendly and cost-effective solutions. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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24 pages, 14529 KB  
Article
Comparison of the Performance of Basalt Fiber-Reinforced Composites Incorporating a Recyclable and a Conventional Epoxy Resin
by Farid Taheri, Shahriar Ahamed Chowdhury and Ahmad Ghiaskar
Polymers 2025, 17(10), 1348; https://doi.org/10.3390/polym17101348 - 15 May 2025
Cited by 6 | Viewed by 3629
Abstract
The present study focuses on the mechanical performances of basalt fiber-reinforced composites based on the more environmentally friendly Recyclamine® resin (BR) and conventional and widely used room-cured epoxy systems (BE). Specifically, the study probes the tensile and compressive responses of the composites [...] Read more.
The present study focuses on the mechanical performances of basalt fiber-reinforced composites based on the more environmentally friendly Recyclamine® resin (BR) and conventional and widely used room-cured epoxy systems (BE). Specifically, the study probes the tensile and compressive responses of the composites fabricated by vacuum-assisted resin transfer molding. Experimental results revealed that the tensile strength of basalt–Recyclamine was higher than its counterpart (464 MPa compared to 390.9 MPa). At the same time, the BR performed only marginally better under compression, with a strength of 237.7 MPa compared to 233.9 MPa for BE. However, the BR demonstrated significantly enhanced ductility reflected by its greater compressive strain capacity (3.9% compared to only 1.1%). Different microscopic analyses unveiled distinct failure mechanisms, with more progressive failure patterns observed in BR compared with the brittle fracture characteristics of the BE composite. The performance of several micromechanical models was also investigated, with their results corroborating with the experimental results with varying degrees of accuracy. The statistical analysis showed great consistency in the results, with the CoV value below 10%. Experimental results indicated that the basalt–Recyclamine composites can be considered a promising sustainable alternative to traditional polymeric resin-based systems due to their balanced mechanical performance and environmental advantages. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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22 pages, 3405 KB  
Article
Impact Value Improvement of Polycarbonate by Addition of Layered Carbon Fiber Reinforcement and Effect of Electron Beam Treatment
by Yoshitake Nishi, Naruya Tsuyuki, Michael C. Faudree, Helmut Takahiro Uchida, Kouhei Sagawa, Yoshihito Matsumura, Michelle Salvia and Hideki Kimura
Polymers 2025, 17(8), 1034; https://doi.org/10.3390/polym17081034 - 11 Apr 2025
Cited by 2 | Viewed by 1836
Abstract
Polycarbonate (PC) is a highly recyclable thermoplastic with high impact strength that bodes well to re-melting extrusion and shredding for positive environmental impact. For the goal of improving impact strength further, layered carbon fiber (CF) reinforcement has been added between PC sheets by [...] Read more.
Polycarbonate (PC) is a highly recyclable thermoplastic with high impact strength that bodes well to re-melting extrusion and shredding for positive environmental impact. For the goal of improving impact strength further, layered carbon fiber (CF) reinforcement has been added between PC sheets by hot pressing at 6.0 MPa and 537 K for 8 min. An addition of cross-weave CF layer reinforcement to PC increased Charpy impact value, auc of the untreated [PC]4[CF]3 composite over that of untreated PC resin reported at all accumulative probabilities, Pf. At medial-Pf of 0.50, auc was increased 3.13 times (213%), while statistically lowest impact value as at Pf = 0 calculated by 3-parameter Weibull equation was boosted 2.64 times (164%). To optimize auc, effect of homogeneous electron beam irradiation (HLEBI) treatment of 43.2, 129, 216, 302, or 432 kGy at 170 kV acceleration voltage to the CF plies before assembly with PC then hot press was also investigated. The 216 kGy HLEBI dose appears to be optimum, raising as at Pf = 0 about 6.5% over that of untreated [PC]4[CF]3 and agrees with a previous study that showed 216 kGy to be optimum for static 3-point bending strength, when quality can be controlled. Electron spin resonance (ESR) data confirms 216 kGy HLEBI generates strong peaks in CF and PC indicating dangling bond (DB) generation. Bending strength increase was higher than that of impact due to lower test velocity and higher deformation area spreading along specimen length, allowing more DBs to take on the load. X-ray photoelectron spectroscopy (XPS) data of CF top ~10 nm surface layer in the sizing confirms C–O–H, C–H, and C–O peak height from 216 kGy exhibited little or no change compared with untreated. However, 432 kGy increased the peak heights indicating enhanced adhesion to PC. However, 432 kGy degraded as at Pf = 0 of the [PC]4[CF]3, and is reported to decrease impact strength of PC itself by excess dangling bond formation. Thus, the 432 kGy created increased PC/CF adhesion, but degraded the PC resin. Therefore, 216 kGy of 170 kV-HLEBI appeared to be a well-balanced condition between the PC-cohesive force and PC/CF interface adhesive force when fabricating [PC]4[CF]3. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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21 pages, 6126 KB  
Article
Influence of Lignin Type on the Properties of Hemp Fiber-Reinforced Polypropylene Composites
by Florin Ciolacu, Teodor Măluțan, Gabriela Lisa and Mariana Ichim
Polymers 2024, 16(23), 3442; https://doi.org/10.3390/polym16233442 - 8 Dec 2024
Cited by 8 | Viewed by 3041
Abstract
Increasing environmental awareness has boosted interest in sustainable alternatives for binding natural reinforcing fibers in composites. Utilizing lignin, a biorenewable polymer byproduct from several industries, as a component in polymer matrices can lead to the development of more eco-friendly and high-performance composite materials. [...] Read more.
Increasing environmental awareness has boosted interest in sustainable alternatives for binding natural reinforcing fibers in composites. Utilizing lignin, a biorenewable polymer byproduct from several industries, as a component in polymer matrices can lead to the development of more eco-friendly and high-performance composite materials. This research work aimed to investigate the effect of two types of lignin (lignosulfonate and soda lignin) on the properties of hemp fiber-reinforced polypropylene composites for furniture applications. The composites were produced by thermoforming six overlapping layers of nonwoven material. A 20% addition of soda lignin or lignosulfonate (relative to the nonwoven mass) was incorporated between the nonwoven layers made of 80% hemp and 20% polypropylene (PP). The addition of both types of lignin resulted in an increase in the tensile and bending strength of lignin-based composites, as well as a decrease in the absorbed water percentage. Compared to oriented strand board (OSB), lignin-based composites exhibited better properties. Regarding the two types of lignin used, the addition of lignosulfonate resulted in better composite properties than those containing soda lignin. Thermal analysis revealed that the thermal degradation of soda lignin begins long before the melting temperature of polypropylene. This early degradation explains the inferior properties of the composites containing soda lignin compared to those with lignosulfonate. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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18 pages, 19223 KB  
Article
Study on Frost Resistance of Recycled Rubber Straw Concrete Using Particle Swarm Optimization Enhanced Artificial Neural Networks
by Qijing Xia and Yongcheng Ji
Polymers 2024, 16(22), 3191; https://doi.org/10.3390/polym16223191 - 17 Nov 2024
Cited by 2 | Viewed by 1276
Abstract
Rubber particles and straw powder were used to prepare recycled rubber straw concrete, and the freeze–thaw test was conducted on the recycled rubber straw concrete using the quick-freezing method. The frost resistance of the recycled rubber straw concrete was evaluated by determining the [...] Read more.
Rubber particles and straw powder were used to prepare recycled rubber straw concrete, and the freeze–thaw test was conducted on the recycled rubber straw concrete using the quick-freezing method. The frost resistance of the recycled rubber straw concrete was evaluated by determining the relative dynamic modulus of elasticity, the rate of mass loss, and the flexural strength of the recycled rubber straw concrete in the process of freezing and thawing. SEM was used to observe the microstructure of the recycled rubber straw concrete after the freezing and thawing process. SEM observed the microstructure of recycled rubber straw concrete after freezing and thawing. The effect and mechanism of rubber admixture and straw admixture on the frost resistance of concrete were investigated by microanalysis. Based on the experimental data, the particle swarm algorithm and genetic algorithm were used to optimize the BP neural network to establish the prediction model of recycled rubber straw powder, and the results show that the PSO-BP neural network prediction model established in this paper has good accuracy and stability. It has a good prediction effect on the flexural strength and the number of freeze–thaw cycles of recycled rubber straw concrete under different mixing ratios. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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28 pages, 24398 KB  
Article
Tribological Characteristics of Fibrous Polyphthalamide-Based Composites
by Yuanyi Shen, Dmitry G. Buslovich, Sergey V. Panin, Lyudmila A. Kornienko, Pavel V. Dobretsov and Yury M. Kolobov
Polymers 2024, 16(16), 2274; https://doi.org/10.3390/polym16162274 - 10 Aug 2024
Cited by 2 | Viewed by 2447
Abstract
The aim of this study was to investigate the tribological characteristics of commercially available high-strength polyphthalamide-based composites with great contents (30–50 wt.%) of both carbon and glass fibers in point and linear contacts against metal and ceramic counterfaces under dry friction and oil-lubricated [...] Read more.
The aim of this study was to investigate the tribological characteristics of commercially available high-strength polyphthalamide-based composites with great contents (30–50 wt.%) of both carbon and glass fibers in point and linear contacts against metal and ceramic counterfaces under dry friction and oil-lubricated conditions at various loads and sliding speeds. The lengths of both types of fibers were varied simultaneously with their contents while samples were fabricated from granules by injection molding. When loading PPA with 30 wt.% SCFs at an aspect ratio (AR) of 200, the ultimate tensile strength and the elastic modulus increased up to 142.7 ± 12.5 MPa and 12.9 ± 0.6 GPa, respectively. In the composites with the higher contents of reinforcing fibers PPA/40CCF and AR~1000, the ultimate tensile strength and the elastic modulus were 240 ± 3 MPa and 33.7 ± 1.9 GPa, respectively. Under the applied test conditions, a composite reinforced with 40 wt.% carbon fibers up to 100 μm long at an aspect ratio of ~1000 possessed the best both mechanical properties and tribological characteristics. One of the reasons that should be considered for improving the tribological characteristics of the composite is the fatigue wear mechanism, which is facilitated by the high filling degree, the strong interfacial adhesion, and the great aspect ratio for fibers. Under the oil-lubricated conditions, both friction coefficients and wear rates decreased, so such friction units could be implemented whenever possible. The reported data can be used as practical recommendations for applying fibrous polyphthalamide-based composites as friction unit components. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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26 pages, 11470 KB  
Article
The Role of Triboloading Conditions in Tribolayer Formation and Wear Resistance of PES-Based Composites Reinforced with Carbon Fibers
by Defang Tian, Changjun He, Dmitry G. Buslovich, Lyudmila A. Kornienko and Sergey V. Panin
Polymers 2024, 16(15), 2180; https://doi.org/10.3390/polym16152180 - 31 Jul 2024
Cited by 1 | Viewed by 1556
Abstract
In this paper, the tribological characteristics of polyethersulfone-based composites reinforced with short carbon fibers (SCFs) at aspect ratios of 14–250 and contents of 10–30 wt.% are reported for linear metal–polymer and ceramic–polymer tribological contacts. The results showed that the wear resistance could be [...] Read more.
In this paper, the tribological characteristics of polyethersulfone-based composites reinforced with short carbon fibers (SCFs) at aspect ratios of 14–250 and contents of 10–30 wt.% are reported for linear metal–polymer and ceramic–polymer tribological contacts. The results showed that the wear resistance could be greatly improved through tribological layer formation. Loading PES with 30 wt.% SCFs (2 mm) provided a minimum WR value of 0.77 × 10−6 mm3/N m. The tribological layer thicknesses were estimated to be equal to 2–7 µm. Several conditions were proposed, which contributed to the formation of a tribological layer from debris, including the three-stage pattern of the changing kinetics of the time dependence of the friction coefficient. The kinetics had to sharply increase up to ~0.4–0.5 in the first (running-in) stage and gradually decrease down to ~0.1–0.2 in the second stage. Then, if these levels did not change, it could be argued that any tribological layer had formed, become fixed and fulfilled its functional role. The PES-based composites loaded with SCFs 2 mm long were characterized by possessing the minimum CoF levels, for which their three-stage changing pattern corresponded to one of the conditions for tribological layer formation. This work provides valuable insight for studying the process parameters of tribological layer formation for SCF-reinforced thermoplastic PES composites and revealing their impact on tribological properties. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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20 pages, 5120 KB  
Article
Effects of Curing Defects in Adhesive Layers on Carbon Fiber–Quartz Fiber Bonded Joint Performance
by Xiaobo Yang, Miaomiao Zhang, Lihua Zhan, Bolin Ma, Xintong Wu, Cong Liu and He Xiang
Polymers 2024, 16(10), 1406; https://doi.org/10.3390/polym16101406 - 15 May 2024
Cited by 7 | Viewed by 2550
Abstract
Due to their mechanical load-bearing and functional wave transmission, adhesively bonded joints of carbon fiber–quartz fiber composites have been widely used in the new generation of stealth aviation equipment. However, the curing defects, caused by deviations between the process environment and the setting [...] Read more.
Due to their mechanical load-bearing and functional wave transmission, adhesively bonded joints of carbon fiber–quartz fiber composites have been widely used in the new generation of stealth aviation equipment. However, the curing defects, caused by deviations between the process environment and the setting parameters, directly affect the service performance of the joint during the curing cycle. Therefore, the thermophysical parameter evolution of adhesive films was analyzed via dynamic DSC (differential scanning calorimeter), isothermal DSC and TGA (thermal gravimetric analyzer) tests. The various prefabricating defects within the adhesive layer were used to systematically simulate the impacts of void defects on the tensile properties, and orthogonal tests were designed to clarify the effects of the curing process parameters on the joints’ bonding performance. The results demonstrate that the J-116 B adhesive film starts to cure at a temperature of 160 °C and gradually forms a three-dimensional mesh-bearing structure. Furthermore, a bonding interface between the J-116 B adhesive film and the components to be connected is generated. When the curing temperature exceeds 200 °C, both the adhesive film and the resin matrix thermally degrade the molecular structure. The adhesive strength weakens with an increasing defect area ratio and number, remaining more sensitive to triangle, edge and penetration defects. By affecting the molecular structure of the adhesive film, the curing temperature has a significant impact on the bonding properties; when the curing degree is ensured, the curing pressure directly impacts the adhesive’s performance by influencing the morphology, number and distribution of voids. Conversely, the heating rate and heat preservation time have minimal effects on the bonding performance. Full article
(This article belongs to the Special Issue Fiber-Reinforced Polymer Composites: Progress and Prospects)
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