Experimental study on effect of impact locations on damage formation and compression behavior of stiffened composite panels with L-shaped stiffener

Abstract

Abstract Experiments are performed in this study to investigate the influence of impact locations on the damage and compression behavior of stiffened composite panels with a single L-shaped stiffener. After the application of low-velocity impact to the flange tip or web from the outboard side with the same energy level, significant differences among the damage types in specimens are observed. The flange tip impact induces complex damage types including ply fracture, splitting, delamination, and stiffener/skin interface debonding. The stiffness discontinuity results in the extensive propagation of delamination along the longitudinal direction. In contrast, the web impact damage is minimal because of the web's high stiffness. The results of compression after impact reveal that these two types of damage lead to considerable differences in compression behavior. The severe damage caused by the former leads to a considerable reduction in buckling load; however, the buckling deformation drives the rapid propagation of damage without any constraint. As a result, no distinct post-buckling stage is observed, and the failure load is considerably reduced. On the other hand, the damage caused by the latter weakens the interaction between the stiffener and skin, thereby slightly reducing both buckling and failure loads. Based on these findings, several suggestions on aircraft structure design and inspection are proposed to avoid significant damage and rapid damage propagation.