Experimental and numerical study on the impact response and compression-after-impact characteristics of repaired composite panels

This study investigates the performance of repaired composite panels under low-velocity impact, as well as their compression-after-impact (CAI) behavior. Damaged composite laminates were repaired by single-patch and double-patch configurations. Low-velocity impact tests were then conducted, followed by damage assessments. Subsequently, CAI tests were performed to evaluate the influences of impact energy, patch size and repair configuration on the load bearing capacity and failure modes of the repaired panels. A finite element model, incorporating continuum damage mechanics, was established by considering three-dimensional composite failure and interlaminar damage. A user-defined subroutine VUMAT and a two-step analysis were implemented in Abaqus/Explicit to simulate the impact and the CAI responses. Experimental results reveal that single-sided repairs have a higher out-of-plane displacement resistance, with only limited damage being observed. However, double-side repairs exhibit a significant damage after impact. Additionally, debonding occurs on the rear side of double-sided repair. CAI results indicate that the failure loads of most double-sided repairs are higher than those of single-sided repairs. The primary failure mode in the repaired structures is featured with laminate cracking propagated from hole edge. The numerical results show that the current model can efficiently predict the dynamic responses of the repaired structures subjected to impact, as well as damage modes. In addition, the CAI results obtained from the FE model also correlate well with the experimental ones.