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Laminated polymer composites are extensively used in various applications ranging from aerospace to automotive, building to marine and offshore, and much more. These composites possess higher mechanical properties in their in-plane directions, but lower interlaminar properties. Especially, low interlaminar fracture toughness (ILFT) makes them susceptible to delamination. In the current research, a novel thermoplastic-based thin-ply composite system is conceptualized and manufactured with an aim to improve the through-the-thickness properties and which can be a competitive solution to traditional epoxy-based composites as well as other class of thermoplastic composites. The detailed experimental investigation on determining the Mode I ILFT properties of these thin ply carbon fibre thermoplastic composites, along with thin ply thermoset composites for benchmarking, is carried out. Quasi-isotropic composite laminates were manufactured using a room temperature cure epoxy, and the novel reactive Methylmethacrylate (MMA) liquid thermoplastic resin. The thin ply/liquid MMA composites have shown 30% and 72% higher Mode I ILFT properties compared to the thick ply/liquid MMA and thin ply/Epoxy composites respectively. Surface morphological studies were conducted to understand and differentiate damage mechanisms in these composites. From the comprehended damage mechanisms, it was deduced that strong fibre-matrix interface, plastic deformation as well as features like ductile drawings in liquid MMA composites make them more resistant to crack propagation.

Fiber-reinforced composites are increasingly used as an outer shell of sporting helmets as an alternative to conventional thermoplastic shells like Acrylonitrile butadiene styrene (ABS), Polyurethane (PU), and polycarbonate (PC) for improved protection. The current research presents a detailed study to manufacture novel woven carbon/Elium® (WEL) thermoplastic composite helmets and investigate the details based on the impact tests following the industrial safety certification criteria (CPSC 1203 helmet certification) tests on the flat, curb-stone, and the hemispherical anvils. The effect of thermoplastic Elium® resin toughened thermoplastic Elium® IM, and Epoxy resin is investigated to understand the benefits offered by the thermoplastic variants in terms of safety, energy absorption, and the impact failure mechanisms. Post-failed Carbon/Elium® thermoplastic composite shells have shown more ductile and less catastrophic damage as opposed to the Carbon/Epoxy composite shell damage. The impact damage mechanisms as observed from the in-situ high-speed camera images have shown more deformation-dominated failure mechanisms for the composite shells manufactured with Elium® and toughened Elium® resin. Carbon/Epoxy composite shells have shown lower energy absorption and the nature of the failure was more catastrophic and more cracks were noticed on the inner side of the foam which is directly attached to the human head. In case of an impact on a flat anvil, the PC shell configuration has shown a critical injury rate of 28.7% and a fatality rate of 6%. With the manufactured Carbon/Elium® composite helmets, the chances of critical and fatal injury rates are reduced to 16.7% and 3% respectively.

The current research presents a first attempt to manufacture thermoplastic tubular composites using carbon fibre as reinforcement and an innovative Elium® resin as the matrix material using Bladder Assisted Resin Transfer Moulding (B-RTM) manufacturing process. The manufacturing process parameters required to achieve a fully impregnated thermoplastic composites were established, and the parts have undergone impact, flexure, and vibration damping tests. The mechanical properties and the failure modes are compared with the tubes manufactured with conventional epoxy matrix. During impact testing, thermoplastic tubular composites have shown 16.3% and 18.9% higher peak load and major damage energy respectively compared to carbon/epoxy tubes. They have also shown distinctive failure modes, with acrylic Elium® composites tubes undergoing more ductile and spreaded failure whilst epoxy composites have shown brittle and catastrophic failure. Flexural tests have shown comparable load-carrying capability, higher strain to failure, and less delamination for carbon/Elium® composites compared to carbon/epoxy composites. These are attributed to the presence of microductlilty and other associated matrix deformation features shown during the fractographic analysis of carbon/Elium® composites. Vibration modal analysis tests have shown 21.7% higher structural damping for carbon/Elium® composite measured at different output locations on the tube. The differences in the failure mechanisms and the underlying reasons for the improvement shown by thermoplastic Elium® composite tubes under different mechanical tests are deliberated in this paper.