Split Hopkinson pressure bar testing of 3D multi-axial warp knitted carbon/epoxy composites

High-strain-rate compression experiments were performed on 3D MWK carbon/epoxy composites with different fiber architectures at room and elevated temperature using an SHPB apparatus. Macro-fracture and SEM micrographs were examined to understand the failure mechanism. The results show the dynamic properties increase with the strain rate and show a high-strain-rate sensitivity. Meanwhile, composites with [0 degrees/0 degrees/0 degrees/0 degrees] have higher properties. Moreover, composites show temperature sensitivity and the properties decrease significantly, especially for composites with [0 degrees/90 degrees/+45 degrees/-45 degrees]. The results also indicate composites take on more serious damage and failure with the strain rate. The failure of composites with [0 degrees/0 degrees/0 degrees/0 degrees] behaves in multiple delaminating, overall expansion and 0 degrees fibers tearing. While that of composites with [0 degrees/90 degrees/+45 degrees/-45 degrees] is mainly interlaminar delaminating, local fibers tearing and fracture on different fiber layers. In addition, with increasing the temperature, the composite shows less fracture and becomes more plastic. The damage of matrix yielding, interface debonding and twisting of fibers increase significantly. (C) 2015 Elsevier Ltd. All rights reserved.