Experimental study on the bending properties and failure mechanism of 3D multi-axial warp knitted composites at room and liquid nitrogen temperatures

Abstract

Three-point bending experiments on 3D multi-axial warp knitted composites with four fiber architectures are performed at room and liquid nitrogen temperatures. Macro-fracture morphology and scanning electron microscope micrographs are examined to understand the deformation and failure mechanism. The results show that the load–deflection curves are significantly different for four types of composites and the bending properties decrease with the increase of fiber orientation angle at room and liquid nitrogen temperatures. Meanwhile, the bending properties at liquid nitrogen temperature have been improved significantly than that of at room temperature. Moreover, the damage and failure patterns of composites vary with the test temperature. At liquid nitrogen temperature, the interfacial adhesion strength is enhanced significantly and the brittle failure feature becomes more obvious. In addition, the failure mechanism at room and liquid nitrogen temperatures can be significantly affected by the fiber architecture.