Impact Fatigue Damage of GFRP Materials Due to Repeated Raindrop Collisions

An impact fatigue study has been conducted for GFRP composite laminates to investigate failure mechanisms. A nylon bead with diameter of 4 mm was used as an impactor to simulate raindrop impact. Various specimen thicknesses of 3.0, 4.0 and 5.0 mm were used during experiment. Incident impact velocity of nylon bead ranged between 100 to 220 m/s. Optical microscopic observations were conducted to evaluate the damage at specimen center part of front and back surfaces. SEM investigations were made on the cross-section of damaged specimen. In conclusion, there are three damage modes were found to appear: debonding, matrix cracking, and delamination. Debonding occurred inside specimen at an early stage. Matrix cracking at front speciemens surface was ring crack, and that at back specimen surface was star crack. Delamination was resulted by repeated impacts. Initiation life for each damage mode depends on incident impact energy expressed as an (E–N) diagram of impact fatigue.