THE EFFECT OF UNDERWATER EXPLOSION SHOCK LOADING ON THE FATIGUE BEHAVIOR OF GRP LAMINATES

This paper reports changes in the fatigue behaviour of glass-reinforced polymer (GRP) laminates after being subjected to increasing shock wave pressures produced by an underwater explosion. The shock testing was performed in a small-scale underwater explosion facility, and by using larger explosive charges and smaller separation distances between the charge and GRP, it was possible to exert higher underwater shock wave pressures on the laminate. The laminate was then fatigue tested in tension-compresion at a stress ratio, R, of - 1 to obtain S-N curves. At low shock pressures the laminate experienced a small amount of cracking in the polymer matrix, but this did not alter the fatigue performance compared with the unshocked laminate. At high shock pressures the laminate experienced gross structural damage in the form of polymer cracking, delamination between the polymer and glass fibre, and fracture of the glass fibres. These effects caused a large reduction in the fatigue resistance.