Examination of impact behavior of composites containing crack repaired by patching

In this study, the low-velocity impact behavior of cracked composite plates repaired using bonded patches was investigated through experimental and numerical approaches, and the effectiveness of external patch repair on impact resistance was evaluated. Within the scope of the study, both patched and unpatched specimens containing cracks and circular holes were manufactured, and low-velocity impact tests were carried out by considering key parameters such as crack length, hole diameter, impact direction, and impact energy. Experimental results were comparatively analyzed based on force–time, force–displacement, and energy–time response curves. The findings demonstrate that external patch repair significantly enhances load transfer around the damaged region by bridging the crack formed around the hole, thereby improving the impact resistance of the composite plates. It was determined that the maximum contact force of patched specimens increased by approximately 40–50% compared to unpatched plates, indicating a substantial recovery in impact load-carrying capacity due to the repair process. Additionally, damage distribution following impact was observed to shift away from the impact center in patched specimens, while the maximum displacement and absorbed energy varied within the range of 15–20%, depending on crack length and impact conditions. The influence of impact direction was also examined, revealing that specimens subjected to rear-face impact exhibited more abrupt and irregular damage evolution compared to front-face impact cases. Overall, the results confirm that bonded patch repair is an effective method for restoring and improving the low-velocity impact performance of cracked composite plates. The combined experimental and numerical findings provide valuable insight into the damage mechanisms of repaired composites and contribute to a better understanding of the effects of geometric and loading parameters on impact behavior.