Charpy impact properties and failure mechanism of 3D MWK composites at room and cryogenic temperatures

Abstract

The charpy impact experiments on the 3D MWK (Multi-axial warp knitted) composites with four different fiber architectures are performed at room (20°C) and liquid nitrogen temperatures (as low as −196°C). Macro-Fracture morphology and SEM micrographs are examined to understand the impact deformation and failure mechanism. The results show that the impact properties decrease significantly with the increase of the fiber ply angle at both room and liquid nitrogen temperatures. Meanwhile, the impact energy at liquid nitrogen temperature has been improved significantly than that at room temperature. Moreover, the fiber architecture has remarkable effect on the impact damage and failure patterns of composites at room and liquid nitrogen temperatures. At liquid nitrogen temperature, the matrix solidification and the interfacial adhesion capacity increase greatly, which effectively hinders the stress wave propagation. However, more micro-cracks appear and the brittle failure feature becomes more obvious.