Abstract
The impact damage behaviour by low velocity impact of graphite/epoxy laminated composites was studied and residual mechanical properties tests were conducted after impact. The laminates were fabricated into 8 ply sheets of (0°/±45°/90°)s with about 2mm thickness from commercially available prepregs (Besfight, Toho Rayon). The falling impact tests were carried out varying the drop height and the weight diameter. Impact damage of the specimens was inspected using a new type of ultrasonic imaging system and the three point bending tests were performed with an Instron type machine. The maximum bending stress decreased due to the impact delamination. The residual maximum bending stress showed lower values with a larger weight diameter as impact energy was increased. The impact reduced the residual elastic modulus. The residual elastic modulus by the back face loading was larger than that by the front face loading in lower impact energy. On the contrary, residual elastic modulus by the back face loading was lower than that by the front face loading in the larger impact energy. Therefore, residual elastic modulus depends on impact energy.
