Effect of off-axis angle on low-velocity impact and compression after impact damage mechanisms of 3D woven composites

This paper presents the influence of the off-axis angles on the low-velocity impact (LVI) and compression after impact (CAI) damage mechanism of three-dimensional (3D) woven carbon/epoxy composites. Three kind of samples with different angles, 0 degrees, 30 degrees and 45 degrees, of the weft and warp yarn orientation were experimentally tested using the drop weight LVI and quasi-static CAI equipment. X-ray micro-computed tomography (Micro-CT) techniques were used to identify the impact damage volumes, damage distribution and damage modes of 3D woven composites. Results indicated that the off-axis angles have significant effects on the LVI and CAI mechanical behavior and final failure mechanisms. Furthermore, Micro-CT revealed that off-axis samples exhibit more damage volumes and out-of-plane deformation. More importantly, the ultimate CAI strength of all the samples are largely governed by the global buckling. However, the formation of buckling damage in 0 degrees samples runs from one edge of the specimen to the other side, whereas that in 30 degrees and 45 degrees samples mainly occur along the weft direction. (c) 2020 The Authors. Published by Elsevier Ltd.