Experimental Study on Impact Damage Resistance and Residual Compression Behaviors of Scarf Repaired Composite Plates

Adhesively bonded repaired aircraft composite structures are also susceptible to low-velocity impact (LVI) events. However, the impact responses and the residual behaviors of the bonded repaired structures are still not expressly revealed. In this paper, the impact damage resistance and residual compression behaviors of scarf repaired composite plates were investigated through experiments. LVI and compression after impact (CAI) experiments were carried out for both scarf repaired plates and virgin composite plates. Impact responses including the impact curves, dent depth, dissipated energy and delamination damage, and residual compression behaviors including the residual strength, failure mode and the failure process were compared and analyzed. The results show that scarf repaired plates get smaller dent depth but larger delamination area than the virgin plates due to the higher out-of-plane stiffness and the cushioning effect of the ductile adhesive layer. The large-area delamination causes a reduction of the compression strength due to sub-laminate buckling and delamination propagation. Therefore, scarf repaired plates might have lower residual compressive strength than virgin composite plates under the same impact energy. It is suggested to comprehensively adopt parameters such as delamination area and dent depth to characterize the impact damage resistance of the bonded scarf repaired structures.