High strain rate behavior and failure mechanism of three-dimensional five-directional carbon/phenolic braided composites under transverse compression

The quasi-static and high-strain-rate compressive experiments were performed on the three dimensional (3D) five-directional carbon/phenolic braided composites with different braiding parameters in the transverse direction. Transverse compressive properties at high strain rates from 500/s to 1500/s were tested using the split Hopkinson pressure bar (SHPB) technique. The dynamic stress vs. strain curves and important mechanical properties such as peak stress, modulus and failure strain were determined. Macro-fracture morphology and the scanning electron microscope (SEM) micrographs were examined to understand the deformation and failure mechanism of composites. The results show the stress vs. strain curves exhibit obvious non-linear characteristics and a marked softening phenomenon. The composites show clearly the strain rate strengthening effects and dynamic toughness phenomenon. The damage and failure patterns of composites vary with high strain rates. Moreover, the transverse dynamic compressive properties and failure mechanism can be significantly affected by the braiding angle and the fiber volume fraction.