Strain rate and temperature effect on mechanical properties and failure of 3D needle-punched Carbon/Carbon composites under dynamic loading

High-strain-rate compression experiments were performed on 3D needle-punched Carbon/Carbon composites at room and elevated temperatures with a Split Hopkinson Pressure Bar (SHPB) apparatus in the longitudinal and transverse direction. Macro-fracture and Scanning Electron Microscope (SEM) micrographs were examined to understand the failure mechanism. The results show composites are characterized as high-strain-rate and temperature sensitivity. With increasing the strain rate, dynamic properties increase significantly. Moreover, transverse properties are higher than longitudinal properties. With increasing the temperature (up to 300 °C), longitudinal and transverse curves rise up, dynamic strength and modulus increase and failure strain decreases. The results also indicate composites take on more serious damage and clear shear failure mode with increasing the strain rate. Longitudinal failure behaves as matrix cracking and compression process on fiber layers. While needle-punched fibers shear fracture and 0°/90° fiber layers delaminating dominate transverse impact failure. In addition, at high strain rates, brittle failure feature becomes more obvious with increasing the temperature.