High strain rate impact effect and failure behavior of 3D six-directional braided composites

The high strain rate impact effect and failure behavior of three-dimensional six-directional (3D6d) braided composites with different braiding angles are reported in this paper. The results show that 3D6d braided composites exhibit typical strain rate sensitivity. Under out-of-plane dynamic compression, the stress–strain curves rise linearly and present obvious softening characteristics. With the increase of strain rate, both the strength and modulus of composites increase, while the failure strain decreases. Moreover, the composites with larger braiding angle exhibit higher dynamic curves and better out-of-plane high strain rate properties. The fracture morphology shows that composites exhibit different dynamic damage and failure modes at different strain rates and braiding angles. As the strain rate increases, the composites show clearer shear fracture feature and more severe brittle failure. The damage is mainly manifested as shear of the sixth and braiding fibers, tear of the fifth fibers on the shear plane, interfacial debonding and matrix cracking. As the braiding angle increases, the damage and fracture of composites are reduced obviously and the composites become less brittle failure at high stain rates.