Research on residual strength and fatigue performance of composite laminates with low-velocity impact damage

In the process of fabrication, installation, maintenance, and use, the laminate structures of composite will inevitably experience impact from foreign objects, resulting in delamination damage. In the aerospace vehicle service process, the fatigue damage evolution and failure mechanism become intricate due to the coupling and influence of various impact-induced damage modes under complex fatigue loads. This paper introduces initial impact damage into two typical laminate structures using the drop hammer impact method. Based on A-scan and C-scan technologies, the damage modes were obtained, and compressive buckling fatigue tests were carried out. It was found that after one million cycles, no damage propagation was observed, and there were no significant changes in the stiffness, buckling load, and load-bearing capacity of the specimens. This verifies the design concept of static coverage fatigue and non-propagation of damage under compression loads for skin laminates, providing basis and support for the composite design of aircraft.