Effect of double impact positions on the low velocity impact behaviors and damage interference mechanism for composite laminates

Composite structures are susceptible to repeated low velocity impact usually occurring at different positions, which is very common but lacks of in-depth exploration. In this paper, two impact positions with the same distance from the center of the [0₂/90₂]_4S composite laminates were impacted sequentially. The impact responses for four impact distances between the double positions were compared. The mechanical curves such as the impact force-time/central displacement curves and the delamination damage projected area were recorded during the tests. Experimental results demonstrated that the interference status for mechanical curves directly corresponded to the impact-induced damage modes at different impact energy. By comparison, the maximum central displacement could characterize the interference degree of double impact positions. In addition, at high impact energy with impact-induced fiber breakage, the dominant energy dissipation mode for the second impact changed from fiber damage to delamination damage with the increase of impact distance.