Experimental investigation on mechanical response and failure analysis of 3D multi-axial warp knitted hybrid composites

Abstract

3D multi-axial warp knitted (MWK) hybrid composites were fabricated successfully. Tensile, compression, bending and shear properties at high temperatures, and impact tests were performed to reveal mechanical response and failure mechanism. The results show the composites exhibit linear feature and brittle, except from shear curve which shows distinct nonlinear behavior. Meanwhile, the curves show non-linear, long plasticity plateau and failure feature in steps at high temperatures. In addition, tension failure is 0° fibers breakage and pulling out, and 90° fibers tearing; Out-of-plane compression behaves as 45° shear fracture and delaminating; while in-plane compression shows delaminating; Bending failure is tearing of fibers and interface debonding on compression surface, 0° fibers fracture on tension surface and fiber layers delaminating; Shear failure exhibits growing matrix shear damage and debonding, 90° fibers fracture in shear, and 0° fibers’ compression; Impact failure shows “star-shaped” mode under quasi-static and “pyramid -shaped” mode with increasing impact velocity. With increasing the temperature, the materials become soft and plastic. The matrix yielding and cracking, interface debonding, and fiber layers delaminating feature become prominent.