Effect of intra-ply hybrid patches and hydrothermal aging on local bending response of repaired GFRP composite laminates

This study investigates the influence of intra-ply hybrid patches and hydrothermal aging on the indentation properties of patch repaired GFRP composites. Fabrics with various proportions of glass and Kevlar fibers were employed as the patches to achieve enhanced mechanical properties by hybridizing Kevlar and glass fibers together. Hydrothermal aging behavior of repaired composite laminates modified with water-resistant glass fibers in the outer layers was further investigated. Specimens were immersed in an environmental chamber containing seawater at temperatures of 30 (ambient), 50, and 70 °C until up to saturation. Damage mechanisms of repaired laminates were monitored using real-time acoustic emission (AE) technique. The experimental results showed that specimens repaired with 50G:50K patches offered superior performance than the virgin specimens. The hydrothermal aging effect on indentation behavior of the modified repaired specimens showed a considerable reduction in indentation properties, with higher strength retention exhibited by the repaired specimens modified with chopped glass fibers compared to the particulate fibers

Review on natural plant fibres and their hybrid composites for structural applications: Recent trends and future perspectives

© 2022 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Sustainability and environmental protection have given rise to the use of renewable and biobased materials in several application areas. Fibre reinforced composites are currently gaining a high market value in both structural and semi-structural applications. Making these materials environmentally friendly, renewable and lighter will protect the environment and increase resource use efficiency. Opposed to synthetic fibres such as carbon and glass, natural plant fibres are less expensive, lighter, degradable, easy to produce, non-toxic and environmentally friendly. However, natural plant fibres are inferior to their synthetic counterparts in both mechanical performance and tolerance to harsh environmental conditions. One method of compensating for these disadvantages is to combine natural and synthetic fibres in a single matrix forming a hybrid composite where the disadvantages of one are compensated by the other. In this way, sustainability and cost minimisation are achieved with acceptable mechanical and physical responses. However, successful implementation and advancement in the development of natural plant fibre reinforced polymer (FRP) hybrid composites require the development of workable conceptual design, suitable manufacturing techniques and understanding of the strengthening mechanisms. The main objectives of this review are to critically review the current state of knowledge in the development of natural FRP hybrid composites, outlining their properties and enhancing them while reducing environmental impact of the product through the hybridisation approach.Peer reviewe

Abrasive water jet drilling of advanced sustainable bio-fibre-reinforced polymer/hybrid composites : a comprehensive analysis of machining-induced damage responses

This paper aims at investigating the effects of variable traverse speeds on machining-induced damage of fibre-reinforced composites, using the abrasive water jet (AWJ) drilling. Three different types of epoxy-based composites laminates fabricated by vacuum bagging technique containing unidirectional (UD) flax, hybrid carbon-flax and carbon fibre-reinforced composite were used. The drilling parameters used were traverse speeds of 20, 40, 60 and 80 mm/min, constant water jet pressure of 300 MPa and a hole diameter of 10 mm. The results obtained depict that the traverse speed had a significant effect with respect to both surface roughness and delamination drilling-induced damage responses. Evidently, an increase in water jet traverse speed caused an increase in both damage responses of the three samples. Significantly, the CFRP composite sample recorded the lowest surface roughness damage response, followed by C-FFRP, while FFRP exhibited the highest. However, samples of FFRP and hybrid C-FFRP recorded lowest and highest delamination damage responses, respectively. The discrepancy in both damage responses, as further validated with micrographs of colour video microscopy (CVM), scanning electron microscopy (SEM) and X-ray micro-computed tomography (X-ray μCT), is attributed to the different mechanical properties of the reinforced fibres, fibre orientation/ply stacking and hybridisation of the samples.Peer reviewe

Low-Velocity Impact Induced Damage Evaluation and Its Influence on the Residual Flexural Behavior of Glass/Epoxy Laminates Hybridized with Glass Fillers

This research work investigates the low-velocity impact induced damage behavior and its influence on the residual flexural response of glass/epoxy composites improved with milled glass fillers. The low-velocity impact damage employing varying impact velocities (3 m/s, 3.5 m/s, and 4 m/s) was induced on baseline and filler loaded samples with different fiber orientations. The residual performance and their damage modes were characterized using post impact flexural (FAI) test and acoustic emission (AE) monitoring. In all fiber orientations, the filler modified glass/epoxy samples showed improved impact strength and stiffness properties. A substantial improvement in impact damage tolerance, especially for samples impacted at 3.5 m/s and 4 m/s was observed. The presence of filler at the interlaminar zone contributed to improved energy dissipation through filler debonding and pull-out. This further contributed in arresting the crack growth, showing reduced damaged area. The inclusion of milled fibers on glass/epoxy laminates enhanced the impact toughness and residual flexural behavior

Reprocessed Materials Used in Rotationally Moulded Sandwich Structures for Enhancing Environmental Sustainability: Low-Velocity Impact and Flexure-after-Impact Responses

In the rotational moulding industry, non-used, scrap, and waste purge materials have tremendous potential to be reprocessed and applied in skin-foam-skin sandwich structures to replace and reduce the use of virgin polymers. This approach not only encourages the re-use of these waste materials but also significantly contributes to reduce environmental impacts associated with the use of virgin polymers in this sector. The demand of rotationally moulded sandwich structures is rapidly increasing in automotive, marine, and storage tanks, where investigating their impact and after-impact responses are crucial. Hence, this study investigated the low-velocity impact (LVI) and flexure-after-impact (FAI) responses of rotationally moulded sandwich structures manufactured using reprocessed materials. Results obtained from LVI induced damage at two different incident energy levels (15 J, 30 J), and the residual flexural strength of impacted structures evaluated by three-points bending tests were compared with non-reprocessed sandwich structures (virgin materials). The impact damage progression mechanism was characterized using the X-ray micro-computer-tomography technique. Reprocessed sandwiches demonstrated 91% and 66% post-impact residual strength at 15 J and 30 J respectively, while for non-reprocessed sandwiches, these values were calculated as 93% and 88%. Although reprocessed sandwich structures showed a lower performance over non-reprocessed sandwiches, they have a strong potential to be used in sandwich structures for various applications

Evaluation of quasi-static indentation response of superelastic shape memory alloy embedded GFRP laminates using AE monitoring

In this paper, the potential of superelastic shape memory alloy (SE-SMA) wire embedded architectures to increase the quasi-static indentation properties of a laminated glass/epoxy composite material was evaluated. Three types of SE-SMA configurations namely straight independent, meshed and anchored wires were embedded in the glass/epoxy composite laminates via a vacuum bag resin infusion technique. Throughout this investigation, the changes in the quasi-static indentation behavior and allied damage mechanisms due to these embedments were compared with the homogenous glass/epoxy laminates. Real time acoustic emission (AE) monitoring technique was employed to characterize the damage profile of the different glass/epoxy specimens during the quasi-static indentation tests. The experimental results showed that SE-SMA embedments play a vital role in increasing the penetration resistance by enhancing redistribution of the indentation load all across the laminates. In particular, the meshed specimens restricted penetration of an indenter and delayed the critical fiber fracture unlike homogeneous and straight wired ones, whereas the anchored specimens further restricted extensive SMA/matrix pull-out, unlike meshed ones and provided the most excellent balance among rigidity, rear face fiber breakage, and SMA/matrix pull-out. Straight, meshed and anchored SE-SMA wires increased the load-carrying capacity approximately by 31%, 79%, and 100%, respectively, in comparison to the homogeneous ones

Long-term durability and ecotoxicity of biocomposites in marine environments: a review

There is a growing interest in replacing fossil-based polymers and composites with more sustainable and renewable fully biobased composite materials in automotive, aerospace and marine applications. There is an effort to develop components with a reduced carbon footprint and environmental impact, and materials based on biocomposites could provide such solutions. Structural components can be subjected to different marine conditions, therefore assessment of their long-term durability according to their marine applications is necessary, highlighting related degradation mechanisms. Through an up-to-date review, this work critically discusses relevant literature on the long-term durability of biocomposites specific for marine environments. Importantly, in this review we report the effects of abiotic parameters, such as the influence of hygrothermal exposures (temperatures and UV radiation) on physical, mechanical and thermal characteristics of biocomposites. Furthermore, we identify and discuss the potential ecotoxicological effects of leaching substances and microplastics derived from biocomposites, as well as the change in mechanical, physical and thermal behaviours correlated to degradation in the fibre matrix interface, surface defects and overall deterioration of the composite's properties. Finally, the combined effects of various environmental exposures on the long-term durability of the biocomposites are critically reviewed