Improving laminates through non-uniform inter-ply angles

Abstract

While recent research on crustacean-inspired helicoidal lay-ups have suggested that very small inter-ply angles lead to better damage tolerance, it is observed that the exoskeleton of crustacean favor a graduation in over a fixed small inter-ply angle. In particular, the shell of the mantis shrimp, a crustacean known to deliver and withstand high impacts, has a helicoidal structure where the inter-ply angle increases from the inner to outer surface. CFRPs mimicking this non-constant helicoidal pitch were fabricated and tested under out-of-plane loading. It is seen that the large inter-ply angles at the surface improve resistance to matrix splitting at where high bending-induced tensile stresses occur while delamination, which tend to occur closer to the point of loading, is concurrently resisted by the small inter-ply angles there. Helicoidal laminates with non-constant pitch have higher peak loads than those with constant pitch and they outperform cross-ply laminates by up to 75%.