Impact behaviors and damage mechanisms of 2.5D woven composites: Experiment and simulation

2.5D structures have received attention because of their excellent interlaminar mechanical properties. However, there is a lack of research on impact progressive damage, damage mechanisms and internal damage morphology. This paper investigated the low-velocity impact behavior and damage mechanisms of 2.5D woven carbon/epoxy composites through a couple of numerical-experimental approach. Two different impact energy levels, 15 J/mm and 20 J/mm, were designed for all the samples using drop weight impact equipment. Then Micro-CT was employed to identify the impact damage volumes and damage distribution of 2.5D woven composites. A novel whole-local finite element model was proposed based on the tests results and Micro-CT images. The experimental results indicated that the impact energy has a significant effect on the damage modes of 2.5D woven composite. Moreover, the numerically predicted mechanical curves and damage modes exhibit good consistency with the experimental results. Importantly, the numerical simulation results showed that the damage mode of 2.5D woven composites under impact energies of 15 J/mm was mainly controlled by yarn-matrix debonding. With the increase of impact energy per unit thickness, the dominated failure mode of 2.5D woven carbon/epoxy composites changes from yarn-matrix debonding to delamination and eventually to yarn breakage.