Experimental investigation on different positional impact damages and shear-after-impact (SAI) behaviors of stiffened composite panels

Buckling and postbuckling performances of stiffened composite panels with different positional impact damage under in-plane shear load were investigated. Barely visible impact damage (BVID) was introduced into three different positions with the same impact energy of 50 J. Damage areas and impact crater depths were both measured and their relationship in each impact position was affirmed. Shear after impact (SAI) experiments were conducted on the damaged specimens. Compared with pristine panels, the impact damaged panels showed a similar buckling mode during the shear process, which was three buckling waves in each skin bay without buckling transition, but had a far different failure mode. Additionally, the changes in buckling and failure load both were different depending on the impact position. The most serious decline in buckling and failure load was caused by the combination of material properties degradation and debonding due to the impact damage.