Damage evolution and failure mechanism of three-dimensional braided composite subjected to varied high strain-rate loadings

Three-dimensional (3D) braided composite exhibit the excellent integrity of a braided structure, which gives the composites the advantages of high-impact damage tolerance, excellent delamination resistance, and high fatigue resistance. They have been widely used in the fields of aerospace and transport. Composites are always subjected to high strain-rate loading in these application cases. Braided composites show significantly different damage evolution under varied high strain-rate loadings. A bridge which can connect the strain rate variation to the different damage evolution of composites is urgently needed for composite strength design. This research demonstrated how the strain rate variation induced the change of damage evolution and failure mode of 3D braided composite. A high-speed camera system was used to capture damage process information. A micro-scale rate-dependent finite-element model (FEM) was established to study the underlying mechanisms. The results show that the velocity gap between yarns and resin becomes more obvious at higher strain-rate loading. Damage morphology of composites under lower strain rate resulted from the higher transverse stress at the output-bar area. Higher strain-rate loading induces plastic deformation, which occurs earlier in composites. The deformation distributes more haphazardly under higher strain-rate loading. Optimizing suggestions are given to improve the impact resistance of 3D braided composites.