LAUSR

Abstract Helicoidal laminates mimicking the shells of mantis shrimp crustaceans have been found to be able to bear higher loads than conventional laminate configurations primarily through quasi-static or low-speed out-of-plane loads. However, mantis shrimps are known to withstand high speed impacts and there is a lack of such studies on helicoidal laminates. A study into the ballistic performance of helicoidal laminates was undertaken. The laminae of chitin fibers forming the shell were simulated by 3 different synthetic fiber reinforced laminates - carbon fiber reinforced epoxy, Kevlar fiber reinforced epoxy and polyethylene fiber laminates. Experimental results showed that helicoidal carbon-epoxy laminates with small inter-ply angles outperform cross-ply and quasi-isotropic laminates. However, helicoidal Kevlar-epoxy and polyethylene fiber laminates performed poorly relative to cross-ply laminates. Further investigations guided by experimental observations and numerical simulations show that matrix splitting is the dominant damage in helicoidal laminates with small inter-ply angles. The projectile perforates the laminate by crushing the fibers at the impact face of the laminate and then slipping through the matrix cracks developed at the back of the laminate attributed to matrix splitting. In contrast, fiber damage is the dominant mode of failure for cross-ply and quasi-isotropic laminates and helicoidal laminates with large angles. Such laminate configurations are therefore recommended for laminae reinforced by tough fibers. Conversely, bioinspired helicoidal lay-ups with small inter-ply angles are advantageous for brittle laminates. With the failure mechanism understood, an even higher ballistic limit is achieved for carbon-epoxy laminates through a mix of helicoidal and cross-ply configurations. The mixed-configuration laminate outperformed cross-ply and quasi-isotropic laminates by 32.6% and 86.6% respectively in terms of impact energy absorbed.