Evaluation of progressive damage of micro-glass bubble modified composite laminates under repeated impacts

Composite materials modified with fillers have been explored extensively to understand their behavior under various loading conditions such as quasi-static, fatigue, and impact. However, the study of repeated impact behavior of nano/micro-modified composite materials is relatively limited. In this work, the effect of micro-glass bubble concentration on impact resistance of glass-fiber reinforced polymer (GFRP) composites subjected to repeated impacts was studied. Three impact energy levels with a minimum of four specimens per case were experimentally tested. Each sample was subjected to 40 repeated impacts or up to perforation. The impact response was evaluated in terms of evolution of the peak force, bending stiffness, visual damage evolution observations and optical transmission imaging at critical stages as a function of number of impacts. Also, Damage Degree (DD) was calculated to monitor the damage evolution process in the laminates. As expected, impact response of GFRP composites varied based on the presence of micro-glass bubbles and the applied impact energy. The presence of micro-glass bubbles introduces novel phenomena that change the damage progression under repetitive impacts and was verified by our visual and thermography images. A better understanding of these phenomena (crack-bridging, tortuosity) and their contribution to both enhancements in impact behavior and type of damage propagation can lead to better design of novel structural composites.