Fiber-reinforced Composites Research Articles

Mechanical and microstructural characterization of sisal fiber-reinforced polyester laminate composites for improved durability in automotive applications

This study investigates the effects of fiber concentration and the stacking sequence of laminae on the mechanical properties of a sisal-reinforced polyester composite. The mechanical properties, such as the tensile, flexural, and impact strength were characterized for laminated composite with different fiber concentrations and stacking sequences of lamina after they were processed using the hand layup weaved method. In addition to the mechanical properties, morphological analysis was done. Specimens with different fiber concentrations and stacking sequences were prepared using a manual compression molding technique that provides a flat plate with a thickness of 5 mm. The results showed that 40 wt% of sisal fiber-reinforced composites with 90/0/45 staking sequence have shown the maximum tensile (68.409 MPa), flexural (64.276 MPa), and impact (67.71 MPa) strength, and laminated composite with 90/0/45 staking sequence has shown superior tensile, flexural and impact properties as it compared with randomly oriented and non-woven fiber reinforced composite. The microstructure showed that a better interface adhesion was observed at 40 wt% of fiber and 90/0/45 staking sequence. Therefore, 90/0/45 laminated composite materials can be proposed for engineering applications that require equivalent properties, including automobile front-fender applications.

Mechanical and microstructural properties of fiber-reinforced basalt rock cutting waste-based geopolymer composites exposed to high temperatures.

Managing basalt rock cutting waste in an environmentally responsible manner is crucial to mitigate its negative impacts and protect both the environment and human health. Recycling basalt rock cutting waste in geopolymer applications offers multiple environmental, economic, and performance benefits, making it a promising approach for sustainable construction practices. For this purpose, this study concerns about the performance of fiber-reinforced basalt rock-cutting waste-based geopolymer composites at high temperatures up to 1000°C. Geopolymer composites were manufactured by activating basalt rock cutting waste with sodium silicate. Alongside the fiber-free mixtures, fiber-reinforced geopolymer composites incorporating 0.5% and 1.0% basalt or polypropylene fibers by volume were synthesized. These composites underwent thermal curing at 100°C for two distinct durations: 8h and 24h. In addition, the geopolymer composites were subjected to thermal exposure at three different temperatures: 600°C, 800°C, and 1000°C. Changes in the strength and weights of the composites were determined after high-temperature exposure. In addition, XRD and SEM/EDX analyses were performed on the selected composites to investigate the changes in the microstructure of the composites. Thermal curing time and fiber content had significant influence on the high-temperature performance of the geopolymer composites. In this study, geopolymer mortars based on basalt rock cutting waste were successfully developed, demonstrating resistance to elevated temperatures up to 1000°C. No reduction in compressive strength was observed in any of the composites when exposed to 600°C, 800°C, and 1000°C. In fact, an increase in strength was recorded at varying rates, compared to the pre-exposure values.

Comparison of the Performance of Nonlinear Time-Dependent Constitutive Models Calibrated with Minimal Test Data Applied to an Epoxy Resin

Epoxy resins are extensively employed as adhesives and matrices in fibre-reinforced composites. As polymers, they possess a viscoelastic nature and are prone to creep and stress relaxation even at room temperature. This phenomenon is also responsible for time-dependent failure or creep fracture due to cumulative strain. Several constitutive equations have been used to describe the mechanical time-dependent response of polymers. These models have been proposed over the past six decades, with minimal direct and practical confrontation. Each model is associated with a specific application or research group. This work assesses the predictive performance of four distinct time-dependent constitutive models based on experimental data. The models were deemed sufficiently straightforward to be readily integrated into practical engineering analyses. A range of loading cases, encompassing constant strain rate, creep, and relaxation tests, were conducted on a commercial epoxy resin. Model parameter calibration was conducted with a minimum data set. The extrapolative predictive capacity of the models was evaluated for creep loading by extending the tests to five decades. The selected rheological models comprise two viscoelastic models based on Volterra-type integrals, as originally proposed by Schapery and Rabotnov; one viscoplastic model, as originally proposed by Norton and Bailey; and the Burger model, in which two springs and two dashpots are combined in a serial and parallel configuration. The number of model parameters does not correlate positively to superior performance, even if it is high. Overall, the models exhibited satisfactory predictive performance, displaying similar outcomes with some relevant differences during the unloading phases.

The Effect of Alkali Treatment on the Mechanical Strength, Thermal Stability, and Water Absorption of Bamboo Fiber/PLA Composites

Alkali treatment is a prevalent method to enhance the interfacial compatibility of natural fiber-reinforced polymer composites (NFRPCs). Although the influence of alkali treatment on the properties of NFRPCs has been extensively investigated, previous studies have predominantly examined individual factors in isolation, leaving the combined effects of alkali solution concentration, treatment temperature, and time relatively unexplored. In this study, an orthogonal experiment was conducted to assess the combined impacts of alkali solution (NaOH) concentration, treatment temperature, and time on the mechanical strength, thermal stability, and water absorption of bamboo fiber (BF)/polylactic acid (PLA) composites. The findings indicated that both the NaOH concentration and temperature exhibited a statistically significant effect (0.01 < p < 0.05) on the mechanical strength of BF/PLA composites, while the treatment time had no significant effect. Furthermore, all three factors had an extremely significant impact (p < 0.01) on the thermal stability of BF/PLA composites. The water absorption of BF/PLA composites was found to be significantly influenced by treatment temperature and time (p < 0.01), while no significant effect of NaOH concentration was observed. The optimal combination of alkali treatment parameters (concentration—5 wt%, temperature—25 °C, time—30 min) for BF/PLA composites was determined. Additionally, it was observed that the water absorption of alkali-treated BF/PLA composites was lower than that of untreated composites for shorter dipping times, but higher for prolonged dipping times. This work offers an important reference for the efficient application of alkali treatment to NFRPCs.

Characterization of Fatigue Properties of Fiber-Reinforced Polymer Composites Based on a Multiscale Approach

This study presents a methodology for characterizing the constituent properties of composite materials by back-calculating from the laminate behavior under fatigue loading. Composite materials consist of fiber reinforcements and a polymer matrix, with the fatigue performance of the laminate governed by the interaction between these constituents. Due to the challenges in directly measuring the properties of individual fibers and the polymer matrix, a reverse-engineering approach was employed. Using the micro-mechanics of fatigue (MMFatigue), we predicted the laminate’s fatigue behavior based on assumed constituent properties and compared these predictions with experimental data from fatigue tests. The properties of the fiber and polymer matrix were iteratively adjusted to minimize the differences between predictions and experimental results, enabling accurate fatigue characterization. To ensure robustness, three laminate angles—0°, 30°, and 60°—were evaluated at three temperatures: low temperature (LT: −40 °C), room temperature (RT: 25 °C), and high temperature (HT: 85 °C). The error, defined as the fatigue life difference between the prediction and the experimental results, were obtained as 2.48% at LT, 7.18% at RT, and 1.25% at HT for a laminate angle of 45°. Finally, the applicability of the multiscale-based fatigue life prediction method was demonstrated through studies on laminates with various angles under tension–compression, and compression–compression cyclic loads, as well as composite pressure vessels under cyclic loading.

Five-Axis Printing of Continuous Fibers on the Mold

This paper explores a five-axis printing method designed to improve the fabrication of continuous fiber-reinforced thermoplastic composites (CFRTPCs), essential for producing lightweight, complex structures in advanced manufacturing. Traditional CFRTPC placement techniques often face challenges with precision, scalability, and optimal fiber orientation, especially in customized, small-scale applications. The proposed five-axis printing technique overcomes these issues by enabling precise fiber orientation and the production of robust spatial structures using 3D-printed molds compatible with CFRTPCs. Validation through three-point bending and surface quality tests revealed that five-axis printed cylindrical-lattice samples, with fibers oriented at 45°, exhibited superior mechanical properties and surface quality. The five-axis printed samples achieved a load-to-weight ratio 27% higher than traditional samples and maintained their shape even under significant deformation. Surface quality improved significantly, with roughness values reduced from 37.63 µm to approximately 12 µm. This method advances CFRTPC applications in industries requiring complex, lightweight components.

Experimental analysis of mechanical properties and FTIR analysis of areca fiber-reinforced epoxy composites incorporating Al2O3

Experimental analysis of mechanical properties and FTIR analysis of areca fiber-reinforced epoxy composites incorporating Al2O3

Experimental investigation and molecular dynamics simulations of plasma treatment on the interface properties of carbon fiber-reinforced PI resin composites

ABSTRACT This paper examines surface modification of carbon fibers using low-temperature plasma and investigates the temperature-dependent interfacial properties of high-performance polyimide-based composites. Additionally, the mechanisms by which air and argon plasma treatments enhance the high-temperature interfacial properties of carbon fiber-reinforced polymers (CFRP) are examined. First, the changes in physical morphology and surface structural defects of carbon fibers under different plasma atmospheres are discussed: carbon fibers develop surface protrusions after various plasma treatments, and a grooved morphology forms after argon plasma treatment. The ID/IG ratio (R value) of the carbon fiber surface increased from 1.25 in untreated fibers to 1.37 after air plasma treatment, and further to 1.60 after argon plasma treatment. The short-beam shear strength test results show that at 300°C, the ILSS (interlaminar shear strength) of argon plasma-treated laminates increased from 67.70 MPa to 87.69 MPa, a 29.53% improvement. The ILSS of air plasma-treated laminates reached 81.46 MPa, a 20.33% improvement. Argon plasma-treated laminates showed more stable interlaminar shear performance at high temperatures, maintaining an interfacial retention rate of 85.11% at 300°C. Secondly, the mechanisms by which air and argon plasma modification enhance the high-temperature interface performance of CFRP are as follows: Air treatment, due to the dual effects of chemical bonding and physical etching, allows the laminated plates to exhibit excellent performance at room temperature. However, in high-temperature environments, the chemical bonding effect is easily affected and damaged, significantly reducing the interface retention rate of the laminated plates. The etching effect of argon treatment is quite significant, which means that the improvement effect of argon mainly manifests in the mechanical interlocking action, with the chemical bonding effect being relatively small. The physical effect of mechanical interlocking is less influenced by temperature, thus the high-temperature retention rate of the laminate is relatively high. Furthermore, molecular dynamics models of the interface were built using atomic simulation to explore how plasma modification introduces active groups that enhance the interface at the molecular level. The impact of these modifications on interfacial structure and energy was analyzed using molecular dynamics metrics. Both experimental and molecular dynamics simulation results confirm that plasma treatment has a positive regulatory effect on the interface.

The Influence of pH Environments on the Long-Term Durability of Coir Fiber-Reinforced Epoxy Resin Composites

This study investigates the effects of different pH environments on the durability of coir fiber-reinforced epoxy resin composites (CFRERCs). The CFRERCs were prepared by combining alkali-treated coir fibers with epoxy resin and exposing them to acidic, alkaline, pure water, and seawater environments for a 12-month corrosion test. The results show that an alkaline environment has the most significant impact on the tensile strength of CFRERCs, with a 55.06% reduction after 12 months. The acidic environment causes a 44.87% decrease in strength. In contrast, tensile strength decreases by 32.98% and 30.03% in pure water and seawater environments, respectively. The greatest reduction in tensile strain occurs in the alkaline environment, with a decrease of 36.45%. In the acidic environment, tensile strain decreases by about 25.56%, while in pure water and seawater, the reductions are 18.78% and 22.65%, respectively. In terms of stiffness, the alkaline environment results in a 49.51% reduction, while the acidic environment causes a 54.56% decrease. Stiffness decreases by 43.39% in pure water and 36.72% in seawater. Field emission scanning electron microscope (FE-SEM) analysis shows that corrosive agents in different pH environments cause varying degrees of damage to the microstructure of CFRERCs. In the acidic environment, corrosive agents erode the fiber–resin interface, leading to delamination and fiber breakage. In the alkaline environment, corrosive agents penetrate the fiber interior, increasing surface roughness and porosity. While pure water and seawater also cause some damage, their effects are relatively mild.

Influence of treatment and fly ash fillers on the mechanical and tribological properties of banana fiber epoxy composites: experimental and ANN-RSM modeling

ABSTRACT This research examines the impact of chemical treatment and banana fly ash fillers on the mechanical, tribological, and water absorption characteristics of banana fiber-reinforced epoxy composites. Alkaline treatment enhanced fiber-matrix adhesion, markedly improving mechanical characteristics. The optimal performance occurred at 10% fly ash content, yielding a tensile strength of 40.25 MPa, a flexural strength of 77.23 MPa, and an impact strength of 44.82 kJ/m2. Water absorption studies indicated a decline in moisture uptake, reducing from 40% in untreated composites to 25% in composites containing 15% fly ash, due to enhanced bonding and fewer voids. Tribological experiments demonstrated a decrease in Specific Wear Rate (SWR) and Coefficient of Friction (COF) with elevated fly ash concentration, signifying improved wear resistance. Predictive modeling with Artificial Neural Networks (ANN) showed enhanced accuracy (mean error: 0.9584% for SWR, 0.50265% for COF). RSM optimization identified the optimal input parameters for minimizing SWR and COF: a sliding velocity of 5.14491 m/s, a sliding distance of 652.05 m, and a fly ash content of 12.6236%, yielding minimum SWR and COF values of 15.63 × 10− 5 mm3/Nm and 0.242241, respectively. SEM analysis confirmed that treated fibers and fly ash fillers minimized wear and crack propagation while improving fracture toughness. The results underscore the promise of banana fly ash-filled composites for automotive, aerospace, and structural applications that necessitate improved mechanical, tribological, and moisture-resistant characteristics.

Quality Investigation of Pultruded Carbon Fiber Panels Subjected to Four-Point Flexure via Fiber Optic Sensing.

Pultruded carbon fiber-reinforced composites are attractive to the wind energy industry due to the rapid production of highly aligned unidirectional composites with enhanced fiber volume fractions and increased specific strength and stiffness. However, high volume carbon fiber manufacturing remains cost-prohibitive. This study investigates the feasibility of a pultruded low-cost textile carbon fiber-reinforced epoxy composite as a promising material in spar cap production was undertaken based on mechanical response to four-point flexure loading. As spar caps are primarily subjected to flexural loading, large-span four-point flexure was considered, and coupon testing was restricted to tensile modulus and compression strength assessment. High-resolution spatial fiber optic strain sensing was utilized to determine spatial strain distribution during four-point flexure, revealing consistent strain along the length of the part and proved to be an excellent option for process manufacturing quality examination. Additionally, holes with diameters of 2.49 mm, 5.08 mm, and 1.93 mm were drilled through the thickness of full-width parts to determine the feasibility of structural health monitoring of pultruding parts internal to wind blades via fiber optic strain sensing.

Mechanical behaviour of 3D printed fiber-reinforced soft functional hydrogel composite: Opportunities for biomedical applications

Owing to the unique native properties of cellulose, such as biocompatibility, biodegradability, and excellent mechanical properties, it offers new strategies for designing environment-friendly, cost-effective, and high-mechanically robust hydrogel composites. Herein, we proposed the fabrication of 3D printed nature-inspired cellulose nanofibers (CNFs) reinforced anisotropic functional nanocomposite hydrogel structure.In this hypothetical study, we focuses on to develop nature-inspired 3D-printed Polyacrylamide PAM / Alginate (Alg) based single layered and multilayered laminate hydrogel composites reinforced with anisotropically oriented CNFs and performing finite element (FE) analysis study via implementing measured experimental material properties to explore the CNF reinforcement mechanism in the fiber-reinforced composite hydrogel. The FE modelling and simulation are based on an idealised anisotropic hyperelastic model used to analyse the anisotropic mechanical behaviour of the 3D printed hydrogel composite structure. The computational study of the nature-inspired printed helicoidally layup hydrogel composite construct exhibit enhanced mechanical properties, which offered appreciable stretchability, toughness and anisotropic mechanical behavior.It will assist the design of the more mechanically compliance composite hydrogel structure, making it suitable for load-bearing biomedical applications.

Lignocellulosic fiber-reinforced starch thermoplastic composites for food packaging application: A review of properties and food packaging abetted with safety aspects

Lignocellulosic fiber-reinforced starch thermoplastic composites for food packaging application: A review of properties and food packaging abetted with safety aspects

Advanced functionalization of carbon fiber-reinforced polymer composites towards enhanced hybrid 4-terminal photo-thermal energy harvesting devices by integrating dye-sensitized solar cells and thermoelectric generators

Advanced functionalization of carbon fiber-reinforced polymer composites towards enhanced hybrid 4-terminal photo-thermal energy harvesting devices by integrating dye-sensitized solar cells and thermoelectric generators

Shear Strength Database for Nonprestressed High-Strength, High-Performance Fiber-Reinforced Cementitious Composites and Ultra-High-Performance Concrete Beams without Stirrups

Shear Strength Database for Nonprestressed High-Strength, High-Performance Fiber-Reinforced Cementitious Composites and Ultra-High-Performance Concrete Beams without Stirrups

Visualizing fiber end geometry effects on stress distribution in composites using mechanophores.

Localized stress concentrations at fiber ends in short fiber-reinforced polymer composites (SFRCs) significantly affect their mechanical properties. Our research targets these stress concentrations by embedding nitro-spiropyran (SPN) mechanophores into the polymer matrix. SPN mechanophores change color under mechanical stress, allowing us to visualize and quantify stress distributions at the fiber ends. We utilize glass fibers as the reinforcing material and employ confocal fluorescence microscopy to detect color changes in the SPN mechanophores, providing real-time insights into the stress distribution. By combining this mechanophore-based stress sensing with finite element analysis (FEA), we evaluate localized stresses that develop during a single fiber pull-out test near different fiber end geometries-flat, cone, round, and sharp. This method precisely quantifies stress distributions for each fiber end geometry. The mechanophore activation intensity varies with fiber end geometry and pull-out displacement. Our results indicate that round fiber ends exhibit more gradual stress transfer into the matrix, promoting effective stress distribution. Also, different fiber end geometries lead to distinct failure mechanisms. These findings demonstrate that fiber end geometry plays a crucial role in stress distribution management, critical for optimizing composite design and enhancing the reliability of SFRCs in practical applications. By integrating mechanophores for real-time stress visualization, we can accurately map quantified stress distributions that arise during loading and identify failure mechanisms in polymer composites, offering a comprehensive approach to enhancing their durability and performance.

Bamboo-inspired 3D printed continuous fiber-reinforced vascular composites

Bamboo-inspired 3D printed continuous fiber-reinforced vascular composites

EFFECTS OF ALKALI TREATMENT ON THE MECHANICAL, CHEMICAL, AND THERMAL PROPERTIES OF ARAMID AND GRASS FIBER-REINFORCED EPOXY HYBRID COMPOSITES

In this study, we investigated enhancing the biodegradability of aramid fiber composites by incorporating natural grass fibers, with the aim of maintaining the performance integrity of the composites. We fabricated a series of aramid and grass fiber hybrid composites with varied weight ratios (ranging from 0% to 40%) in an epoxy matrix in order to assess the effects of the fiber ratio and alkali treatment on the thermal, mechanical, chemical, and morphological properties of the composites. One pivotal finding was the substantial increase in tensile strength with higher aramid fiber content; notably, a composite with a 30 wt% aramid and 10 wt% grass fiber ratio showcased remarkable strength, retaining about 60% of the tensile capability of a pure aramid fiber composite. Alkali treatment of grass fibers was found to significantly enhance the overall attributes of the composites, evidenced by an increase in crystallinity and improved thermal stability, where treated hybrids demonstrated a higher decomposition threshold compared to their untreated counterparts. Furthermore, these composites exhibited superior resistance in acidic environments, indicating their robustness and applicability across diverse operational scenarios. The investigation into dielectric strength revealed a positive correlation with the inclusion of aramid fibers, peaking with composites fully composed of treated fibers. The scanning electron microscopy analysis after fractography confirmed enhanced fiber-matrix interactions following alkali treatment, further substantiating the observed performance improvements. Therefore, in this paper, we highlight the potential of alkali-treated grass fibers in creating sustainable, high-performance aramid fiber composites, representing a significant stride toward eco-friendly material innovation.

A method for realizing continuous tungsten fiber-reinforced steel matrix composites by wire-arc-based directed energy deposition

A method for realizing continuous tungsten fiber-reinforced steel matrix composites by wire-arc-based directed energy deposition

Effects of ultrasonication on electrical and self-sensing properties for fiber-reinforced cementitious composites containing MWCNTs

Effects of ultrasonication on electrical and self-sensing properties for fiber-reinforced cementitious composites containing MWCNTs