Mode I fracture toughness and fractographic investigation of carbon fibre composites with liquid Methylmethacrylate thermoplastic matrix

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.