Search Results (184)

This work presents a study on the evaluation of the erosive wear behavior of laminated composites, manufactured using the vacuum-assisted resin infusion (VARI) method with a glass fiber-reinforced epoxy matrix modified with SiO₂ nanoparticles (0.0, 1.5, and 3.0 wt.%). Results indicate that nanoparticle concentration and dispersion state critically influence the mechanical and tribological performance. The composite FG-1.5-SiO₂ with 1.5 wt.% SiO₂ exhibited optimal nanoparticle distribution, as confirmed by FTIR, GIXRD, and SEM analyses, with the lowest surface roughness (Ra = 0.215 μm), highest hardness (35.58 HV), and highest elastic modulus (19.66 GPa). These enhancements contributed to a 38% improvement in erosion rate compared to the unmodified laminated composite, with the lowest total mass loss (0.0261 mg) and erosion rate (2.3360 × 10⁻⁵ mg/g). Profilometry and SEM results revealed shallower wear depths and reduced matrix removal, indicating stronger fiber–matrix interface integrity. In contrast, the 3.0 wt.% SiO₂ composite (FG-3-SiO₂) suffered from nanoparticle agglomeration, which increased surface roughness, diminished mechanical properties, and reduced erosion resistance to levels comparable to the unreinforced material. The results indicate that homogeneous dispersion at an optimal concentration (1.5 wt.%) is crucial for improving erosion resistance, while agglomeration at higher concentrations negates the potential benefits of nanoparticle incorporation. These findings highlight the need to optimize nanoparticle dispersion for the development of fiberglass/epoxy composites with greater durability and erosion resistance in demanding applications. Full article

Fiber-reinforced polymer composites (FRPCs) are increasingly used in construction due to their high performance and low environmental footprint. However, their widespread adoption has raised concerns over end-of-life management, particularly under European regulations mandating high recycling rates for construction and demolition waste (CDW). This study evaluates different systems for the chemical recycling of FRPCs through microwave (MW)-assisted solvolysis using green solvents, including deep eutectic solvents (DESs) and biobased acetic acid. The process targets thermoset resin depolymerization while preserving fiber integrity, operating at reduced temperatures (≤230 °C) and lower energy demand than conventional techniques, such as pyrolysis. A systematic experimental design was applied to CDW-derived polyester composites and extended to industrial epoxy and vinyl ester composites. Among the tested solvents, glacial acetic acid + ZnCl₂ (5 wt.%), achieved the highest degradation efficiency, exceeding 94% in small-scale trials and maintaining over 78% upon upscaling. Recovered fibers showed moderate property retention, with tensile strength and elongation losses of ~30% and ~45% for infusion-based epoxy composites, while those from pultrusion-based epoxy composites exhibited 16–19% and retained similar properties to the virgin material, respectively. The method facilitates fiber recovery with limited degradation and aligns with circular economy principles through solvent reuse and minimizing environmental impact. Full article

Achieving the ambitious EU goals of zero-waste manufacturing requires innovative tools and methodologies that address both efficiency and environmental sustainability. This study presents a comprehensive methodology for assessing the efficiency and eco-efficiency of industrial processes, in order to support zero-waste manufacturing strategies. The proposed approach assesses critical performance metrics while integrating environmental-impact analysis to provide a holistic view of process optimization. The methodology was applied to two industrial use cases in the composites sector, a field with significant environmental impact due to the resource-intensive nature of composite manufacturing and challenges associated with the end-of-life management. By implementing this dual assessment, the study identifies key areas for improvement in operational performance and sustainability, offering actionable insights for process optimization and waste reduction. The results reveal that labor costs emerged as the primary contributor to the total costs for both use cases, more than 50%. On the other hand, the resin infusion phase accounts for the majority of the environmental impacts, accounting for more than 70% of the total impacts. This analysis highlights that eco-efficiency assessments, integrating environmental and cost data, allow the identification of inefficiencies, helping industries to prioritize improvement areas. In this specific case, the high environmental impact of resin infusion needs enhanced waste monitoring and process optimization, while the labor-intensive operations need streamlined workflows to reduce operational time and associated costs. The present methodology intends to serve as a practical tool for industries aiming to balance high-performance manufacturing with reduced environmental impact. Full article

Vehicle crush boxes are one of the safety elements used in vehicles to minimize damage that may occur during an accident. The task of crush boxes is to absorb the energy which is generated during an accident. In this study, peak force, energy absorption and specific energy absorption values of cylindrical composite crush boxes, to which 0.25% and 0.50% graphene was added, were experimentally investigated with hydrothermal aging. The composite crush boxes were produced with vacuum infusion method. Glass, aramid and carbon fibers and their hybridizations were used as fibers. During hybridization, the winding order of the fibers was changed from inside to outside. The parameters for hydrothermal aging were selected as 500 h and 1000 h at 60 °C. The highest energy absorption value was obtained in the carbon fiber-reinforced sample CFRPG1H2 with 0.25% graphene-added epoxy resin matrix, aged for 1000 h. The lowest peak strength was observed in the aramid fiber-reinforced sample AFRPG2H2 with 0.50% graphene-added epoxy resin matrix, hydrothermally aged for 1000 h. It was observed that increasing the graphene addition rate reduced the negative effects on aging. It was determined that increasing the graphene ratio by 0.25% had an effect on aging. Full article

Carbon-reinforced epoxy laminated composite (CREC) structures are increasingly utilized in high-speed marine vehicles (HSMVs) due to their high specific strength and stiffness; however, they are frequently subjected to impact loads like slamming and aggressive environmental agents during operation. This study experimentally investigates the Compression After Impact (CAI) behavior of CREC plates with varying lamination sequences under both atmospheric and accelerated aging conditions. The samples were produced using the vacuum-assisted resin infusion method with three specific orientation types: quasi-isotropic, cross-ply, and angle-ply. To simulate the marine environment, specimens were subjected to accelerated aging in a salt fog and cyclic corrosion cabin for periods of 2, 4, and 6 weeks. Before and following the aging process, low-velocity impact tests were conducted at an energy level of 30 J, after which the residual compressive strength was measured by CAI tests. At the end of the aging process, after the sixth week, the performance of plates with different layer configuration characteristics can be summarized as follows: Plates 1 and 2, which are quasi-isotropic, exhibit opposite behavior. Plate 1, with an initial toughness of 23,000 mJ, increases its performance to 27,000 mJ as it ages, while these values are around 27,000 and 17,000 mJ, respectively, for Plate 2. It is thought that the difference in configurations creates this difference, and the presence of the 0° layer under the effect of compression load at the beginning and end of the configuration has a performance-enhancing effect. In Plates 3 and 4, which have a cross-ply configuration, almost the same performance is observed; the performance, which is initially 13,000 mJ, increases to around 23,000 mJ with the effect of aging. Among the options, angle-ply Plates 5 and 6 demonstrate the highest performance with values around 35,000 mJ, along with an undefined aging effect. Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS) analyses confirmed the presence of matrix cracking, fiber breakage, and salt accumulation (Na and Ca compounds) on the aged surfaces. The study concludes that the impact of environmental aging on CRECs is not uniformly negative; while it degrades certain configurations, it can enhance the toughness and energy absorption of brittle, cross-ply structures through matrix plasticization. Full article

Adhesive joint failure remains a critical limitation in the manufacturing of large wind turbine blades, where reliable and reproducible surface preparation methods are required at an industrial scale. This study systematically evaluates the effect of peel ply-induced surface morphology and chemistry on the adhesion performance of glass fiber-reinforced polymer (GFRP) laminates, explicitly examining the relationship between wettability and bonding strength. Five surface conditions were generated during vacuum-assisted resin infusion using different commercial and proprietary peel plies and a smooth mold surface. Despite significant differences in contact angle and surface energy, lap shear testing revealed no significant relationship between wettability and joint strength. Instead, surface roughness-driven mechanical interlocking and adhesive–substrate compatibility dominated performance. Compared to the smooth mold surface, twill-type peel ply–modified adherends increased shear strength by up to 3.9×, while other commercial types of peel-plies presented strength improvements between 2.7 and 3.3×. More compatible adhesive–polymer resin systems exhibited a combination of cohesive and adhesive failures, with no clear dependence on surface roughness. In contrast, when the adhesive is less compatible with the substrate, surface roughness significantly affects the adhesive response, with adhesive failure predominating. The adhesive application temperature showed no measurable effect for practical industrial use. These findings demonstrate that wettability alone is not a reliable predictor of adhesion performance for this class of substrates and confirm peel ply surface modification as a robust, scalable solution for industrial wind blade bonding. Full article

Type IV composite overwrapped pressure vessels—characterized by a polymer liner fully wrapped in fiber-reinforced polymer—are emerging as lightweight, corrosion-proof alternatives to traditional metal cylinders in fire safety applications. This paper presents a comprehensive review of Type IV high-pressure vessels used in portable fire extinguishers and self-contained breathing apparatus (SCBA) systems. We outline recent material innovations for both the non-metallic liners and composite shells, including multilayer liner designs (e.g., high-barrier polymers and nanocomposites) and advanced fiber/resin systems. Key manufacturing developments such as automated filament winding, resin infusion, and in-line non-destructive testing are discussed. Technical performance in fire applications is critically examined: current standards and certification requirements (EU and international), typical design pressures (e.g., 300 bar in SCBA) and safety factors, common failure modes (liner collapse, fiber rupture, etc.), inspection protocols, and a comparison with Type IV hydrogen storage cylinders. Market trends are also reviewed, highlighting the major manufacturers and the growing adoption of composite extinguishers (e.g., 20-year service-life composite units) versus conventional steel. The review draws on 7–10 peer-reviewed studies to analyze the state of the art, finding that Type IV vessels offer significant weight reduction (>30%) and corrosion resistance at the cost of more complex design and certification. In firefighting use, these cylinders demonstrably improve firefighter mobility and reduce maintenance, while meeting rigorous safety standards. Remaining challenges include further improving liner permeability barriers to prevent gas leakage or collapse, understanding long-term composite aging under cyclic loads, and optimizing fire resistance. Overall, Type IV composite pressure vessels represent a major innovation in fire suppression technology, enabling safer and more efficient extinguishing equipment. Future research and standardization efforts are recommended to fully realize their benefits in fire protection. Full article

Graphene oxide (GO) has been successfully used as a filler to modify various properties of polymers and fiber-reinforced composites. The resulting properties depend on the filler content and on the distribution of GO in the polymer matrix. In this work, for the first time, we introduced GO into the highly viscous DEN-438 epoxy novolac resin and investigated rheological properties of the resulting compositions. In particular, we studied the functions of complex viscosity, storage and loss moduli, and mechanical loss tangent on temperature and GO content. The unusual behavior of the newly prepared formulations compared to typical GO/epoxy mixtures was discovered. At low GO content, introduction of GO led not to an increase, but to a decrease in the resin viscosity, with the minimum registered at 0.29 wt.% GO. After this threshold value, viscosity increased with GO content, which we explained by formation of the liquid crystalline structure. At higher GO concentrations, the formulations changed their state from solid-like at rest to liquid-like under load, with the properties being highly desired for film binders. The discovered properties of the GO/novolac epoxy resin formulations suggest their potential use as the new generation of film binders for Resin Film Infusion technology. Full article

Pultrusion is a manufacturing process used to produce fiber-reinforced polymer composites with excellent mechanical, thermal, and chemical properties. The resulting materials are lightweight, durable, and corrosion-resistant, making them valuable in aerospace, automotive, construction, and energy sectors. However, conventional thermoset composites remain difficult to recycle due to their infusible and insoluble cross-linked structure. This review explores integrating vitrimer technology a novel class of recyclable thermosets with dynamic covalent adaptive networks into the pultrusion process. As only limited studies have directly reported vitrimer pultrusion to date, this review provides a forward-looking perspective, highlighting fundamental principles, challenges, and opportunities that can guide future development of recyclable high-performance composites. Vitrimers combine the mechanical strength (tensile strength and modulus) of thermosets with the reprocessability and reshaping of thermoplastics through dynamic bond exchange mechanisms. These polymers offer high-temperature reprocessability, self-healing, and closed-loop recyclability, where recycling efficiency can be evaluated by the recovery yield retention of mechanical properties and reuse cycles meeting the demand for sustainable manufacturing. Key aspects discussed include resin formulation, fiber impregnation, curing cycles, and die design for vitrimer systems. The temperature-dependent bond exchange reactions present challenges in achieving optimal curing and strong fiber–matrix adhesion. Recent studies indicate that vitrimer-based composites can maintain structural integrity while enabling recycling and repair, with mechanical performance such as flexural and tensile strength comparable to conventional composites. Incorporating vitrimer materials into pultrusion could enable high-performance, lightweight products for a circular economy. The remaining challenges include optimizing curing kinetics, improving interfacial adhesion, and scaling production for widespread industrial adoption. Full article

Fibre-reinforced composites are facing new challenges in the context particular in sustainability and recyclability. Vitrimers could be useful as new matrices to support the increase in sustainability. Due to their high strength, which is comparable to that of thermosets often used in composites, and their covalent adaptive networks, which make them reshapeable for scaled-up manufacturing and recycling purposes, they are very useful. Orthogonal cutting is used for precise reshaping and functional integration into carbon fibre reinforced plastics. Vitrimers could improve processing results at the cutting edge as well as surface quality thanks to their self-healing properties compared to brittle matrices, as well as enabling the recycling of formed chips and scrap. This study showcases the manufacturing of a carbon fibre-reinforced vitrimer using 4-aminophenyl disulfide as a hardener, with vacuum-assisted resin infusion. The temperature of chip formation and the cutting parameters are then shown for different fibre orientations, cutting widths and speeds. The observed cutting forces are lower (less than 140 N) and more irregular for fibre orientations 45°/135°, increasing with cutting depth, and fluctuating periodically during machining. Despite varying cutting speeds, the forces remain relatively constant in range between 85 N and 175 N for 0°/90° fibre orientation and 50 N and 120 N for 45°/135° fibre orientation, with no significant tool wear observed and lower-damage depth and overhanging fibres observed for 0°/90° fibre orientation. Damage observation of the cutting tool shows promising results, with lower abrasion observed compared to thermoset matrices. Microscopic images of the broached surface also show good quality, which could be improved by self-healing of the matrix at higher temperatures. Temperature measurements of chip formation using a high-speed camera show a high temperature gradient as cutting speeds increase, but the temperature only ever exceeds 180 °C at cutting speeds of 150 m/min, ensuring reprocessability since this is below the degradation temperature. Therefore, orthogonal cutting of vitrimers can impact sustainable composite processing. Full article

This study presents a comparative investigation of the mechanical performance of epoxy-based composites reinforced with ±45° multiaxial non-crimp fabrics (NCFs) made from natural flax fibers and conventional glass fibers. Flax fibers, despite their attractive sustainability profile and favorable specific mechanical properties, are typically processed into twisted yarns for textile reinforcement, which compromises fiber alignment and reduces composite performance. A novel yarn-free flax NCF was developed using false twist stabilization of aligned slivers to eliminate the negative effects of yarn twist. Composite laminates were manufactured via vacuum-assisted resin infusion (VARI) under identical processing conditions for both flax- and glass-based reinforcements and tested for tensile, compressive, and flexural behavior. The results show that, although glass fiber composites exhibit superior absolute strength and stiffness, flax-based NCF composites offer competitive specific properties and benefit significantly from improved fiber alignment compared to yarn-based variants. This work provides a systematic comparison under standardized conditions and confirms the mechanical feasibility of flax NCFs for semi-structural lightweight applications. Full article

Recently, environmental issues have compelled people worldwide to pursue sustainability and adopt circular economy practices across all engineering sectors, including polymer engineering and composite fabrication. A transition towards fabric-reinforced thermoplastics (FRTPs), a greener solution, has been recommended in recent years. On the other hand, utilizing recovered reinforcing phases, such as recycled carbon fiber (rCF), has attracted tremendous attention. In this framework, the aim of this research is to investigate the performance of acrylic-based FRTPs (Elium^® resin developed by Arkema). Woven virgin carbon fiber (vCF) and non-woven recycled carbon fiber (rCF) fabrics were used as reinforcement architectures for the fabrication of composites via resin infusion. The optimized formulation selected for the matrix showed flexural modulus and flexural strength of 5 GPa and 78 MPa, respectively. Composites prepared with woven vCF reached 36 GPa and 620 MPa values of flexural modulus and strength, respectively. The study of non-woven fabric is of particular interest, because the web is composed of recycled carbon fibers obtained from end-of-life (EoL) thermoset composite components. The results were promising; the flexural modulus reached 8 GPa, and the flexural strength was 113 MPa. Improvements are anticipated, especially in the parameters and conditions of the molding process. Full article

Structural composite materials are being used more than ever in aeronautics, automotive and naval, or in renewable energies fields. To reconcile the contradictory needs for higher performances and lower costs, it is crucial to ensure the real-time monitoring of as many features as possible during the manufacturing process to feed a digital twin able to minimise post-fabrication controls. For thermoset composites, little information is available regarding the evolution of the polymer’s core properties during infusion and curing. The local kinetics of reticulation, in several areas of interest across the thickness of a structural composite part, are valuable data to record and analyse to guarantee the materials’ performances. This paper investigates a novel strategy curing in the core of an epoxy matrix with crosslinkable quantum-resistive nanocomposite sensors (xQRS). First, the electrical behaviour of the sensor during isothermal curing is considered. Then, the influence of the dynamic percolation and the epoxy crosslinking reaction on the resistance is examined. The evidence of a relationship between the curing state of the resin and the evolution of the xQRS resistance makes its use in the process monitoring of thermoset composites promising, especially in cases involving large and thick parts. Full article

Three-dimensional printed polycaprolactone (PCL) tissue engineering scaffolds have drawn increasing interest from the medical industry due to their excellent biocompatibility and biodegradability, yet PCL’s poor mechanical performance has limited their applications. This study introduces a biocompatible and biodegradable polylactic acid (PLA) fiber reinforced PCL (PLA/PCL) composite as the filament for 3D printed scaffolds to significantly enhance their mechanical performance: Special-made PLA short fiber mat was infused with PCL matrix and rolled into PLA/PCL filaments through a “Vacuum Assisted Resin Infusion” (VARI) process. The investigation revealed that the PLA fibers are highly oriented along the printing direction when using this filament for 3D printing due to the unique microstructure formed during the VARI process. At the same PLA fiber content, the percentage increase in Young’s modulus of the 3D printed strands using the filaments produced by the VARI process is 127.6% higher than the 3D printed strands using the filaments produced by the conventional melt blending process. The 3D printed tissue engineering scaffolds using the PLA/PCL composite filament with 11 wt% PLA fiber content also achieved an exceptional 84.2% and 143.3% increase in peak load and stiffness compared to the neat PCL counterpart. Full article

This paper describes the development of a new hybrid composite for the metal joints of aluminium and glass fibre composite adherents. The aluminium adherend is manufactured using friction stir-formed studs that are inserted into the composite adherend in the through-thickness direction during the composite manufacturing process, where the dry fibres are displaced to accommodate the studs before the resin infusion process. The materials used were AA6082-T6 aluminium and plain-woven E-glass fabric reinforced epoxy, with primary applications in naval vessels. This joining approach offers a cost-effective solution that does not require complicated onsite welding. The joint design was developed based on a simulation test program with finite element analysis, followed by experimental characterisation and validation. The design solution was analysed in terms of the force displacement response, sequence of load transfer, and characterisation of the joint failure modes. Full article