For mass production of structural composites, use of different textile patterns, custom preforming, room temperature cure high performance polymers and simplistic manufacturing approaches are desired. Woven fabrics are widely used for infusion processes owing to their high permeability but their localised mechanical performance is affected due to inherent associated crimps. The current investigation deals with manufacturing low-weight textile carbon non-crimp fabrics (NCFs) composites with a room temperature cure epoxy and a novel liquid Methyl methacrylate (MMA) thermoplastic matrix, Elium®. Vacuum assisted resin infusion (VARI) process is chosen as a cost effective manufacturing technique. Process parameters optimisation is required for thin NCFs due to intrinsic resistance it offers to the polymer flow. Cycles of repetitive manufacturing studies were carried out to optimise the NCF-thermoset (TS) and NCF with novel reactive thermoplastic (TP) resin. It was noticed that the controlled and optimised usage of flow mesh, vacuum level and flow speed during the resin infusion plays a significant part in deciding the final quality of the fabricated composites. The material selections, the challenges met during the manufacturing and the methods to overcome these are deliberated in this paper. An optimal three stage vacuum technique developed to manufacture the TP and TS composites with high fibre volume and lower void content is established and presented.
In the world of fast-growing technology, switch from traditional wooden and metallic sports racquets to next generation powerful racquets is inevitable with the advent of carbon fibres, which offer benefits like increased strength, stiffness, impact, and efficient vibration and damping properties. The introduction of carbon fibres, however, comes with challenges of choosing a right matrix system that, in combination, provides the best solution without sacrificing performance. Non-crimp fabric thin C-Ply composites have the potential to suppress the micro cracks and delamination until the material's ultimate strength. But still, their usage and the possible advantages they can offer in sports applications like tennis racquets, badminton racquets or table tennis bats and so on are yet to be explored. This article aims at exploring the niche benefits offered by thin C-Plyä carbon fibres in combination with thermoset and thermoplastic matrices in sports applications, especially racquets. The composites comprised multi-axial reinforcement fabrics/non-crimp fabrics infused with a room-temperature cure epoxy or a thermoplastic resin having low mix viscosity (200 cps) suitable for vacuum-assisted resin infusion. The mechanical properties of carbon fibre thin C-Ply/(thermoplastic or thermoset) composites pivotal in racquets, like tensile and flexural stiffness and modulus, have been determined experimentally. Double cantilever beam Mode I tests are also carried out to determine the bonding strength between the plies and the matrix interface as most of the failures in sports equipment are accompanied by either bond failures or imperfections within the structure. The findings of testing of various specimens are presented and discussed.
Non-crimp fabrics are fabric tapes stitched to an adjacent orthogonal fabric with no associated crimp. In the current research, the effect of fixation polyester stitches in improving through-the-thickness properties of non-crimp fabric composite laminates is investigated. Detailed experimental studies on interlaminar fracture toughness and static indentation properties of stitched and unstitched thin ply carbon fibre epoxy composites have been conducted. About 23% higher peak load and 37% higher energy absorption were noticed during static indentation tests for the stitched ply composites. A detailed SEM investigation has shown that the stitch-stitch interaction ‘within a bi-angle ply’ and ‘between the bi-angle ply’ plays a significant role in reducing the delamination extent. The critical energy release rate during Mode I fracture toughness of stitched composites was found to be 26.5% higher and SEM investigation depicted that the stitches promote the intra-laminar delamination and enhance the toughness of the composite.
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