Micromechanisms and Characterization of Low-Velocity Impact Damage in 3D Woven Composites

Low-velocity impact (LVI) damage of 3D woven composites were experimentally and numerically investigated, considering different off-axis angles and impact energies. The impact responses were examined by LVI tests, and the damage morphology inside the composites was observed by X-ray micro-computed tomography (mu-CT). Yarn-level damage evolution was revealed by developing a hybrid finite element analysis model. The results show that the impact damage has significant directionality determined by the weft/warp orientation of the composites. The damage originates at the bottom of the impacted area and then expands outwards and upwards simultaneously, accompanied by in-plane and out-of-plane stress transfers. The straight-line distributed weft/warp yarns play an important role in bearing loads at the beginning of loading, while the w-shape distributed binder warp yarns gradually absorb impact deformation and toughen the whole structure as the loading proceeds. The effect of directional impact damage on post-impact performance was explored by performing compressing-after-impact (CAI) tests. It is revealed that the CAI properties along principal directions are more sensitive to the low-velocity impact, and the damage mode is significantly affected by the loading direction.

Automated summary

In this study, the low-velocity impact damage behavior and influencing factors of 3D woven composites were investigated experimentally and numerically. The results showed that the damage exhibited significant directionality, which was closely related to the weft/warp orientation of the composites. The distribution shape of the yarns played an important role in absorbing impact deformation and strengthening the structure during loading. Furthermore, the directional impact damage significantly affected the post-impact performance.