Defect effect on high strain rate compressive behaviors of 3D braided composites

Defect effects of carbon fiber composites under dynamic impact conditions are important to mechanical behavior design in the aerospace field. Here we report the defect effect on the impact compressive behavior of 3D braided composites at high strain rates from 550/s to 1240/s. The defect effect on damage behavior was observed by high-speed photography and digital image correlation (DIC) technology. A finite element analysis (FEA) model was developed to show the defect effect on stress distribution and thermo-mechanical behavior. The defect structure reduces the compressive strength of the composite and causes more brittle and catastrophic failure compared with the perfect composite. The defect effect on the compressive behaviors is more significant at higher strain rates. FEA results show that the defect structure causes local stress concentration, high adiabatic temperature rise, and high stress in the X-shaped shear band region, thereby accelerating composite failure.