Repeated Double-Point Low-Velocity Impact Response and Damage Interference Mechanism of Glass Fiber-Reinforced Composites

The low-velocity impact behavior and damage evolution of glass fiber-reinforced composites were explored in-depth, taking into account the damage accumulation and damage interference in this paper. Two impact positions with the same distance from the center of composite laminates were impacted sequentially until the failure of the laminates. The impact behaviors for four impact distances between the two impact positions were analyzed. The mechanical curves containing contact force-time/displacement curves and absorbed energy-time histories of each impact position were recorded. The variations of mechanical characteristics and the differences of impact responses between the two impacts were further analyzed, associated with the damage induced in the laminates at different impact distances. Experimental results showed that the uninterfered status of the correlation between the double impacts could be converted into interfered due to damage accumulation for the 30 mm impact distance. Total 14 impact groups were conducted to penetrate the laminates for the 30 mm impact distance, which was more than twice the impact group for the 10 mm impact distance. For the 30 mm impact distance, the damage of fiber breakage was restrained by the abundant development of delamination damage between the double impact positions, which further delayed the failure of the laminates. The ultimate delamination area for the 30 mm impact distance acquired the largest value of 2158 mm2, which was 40.68% larger than that of the 10 mm impact distance.