THE EFFECT OF UNDERWATER EXPLOSION SHOCK LOADING ON THE FLEXURAL PROPERTIES OF GRP LAMINATES

This paper examines changes to the flexural properties of a monolithic glass reinforced polymer (GRP) laminate when impulsively loaded by an underwater shock wave produced by an explosion. The laminate was expe rimentally tested using shock waves having a wide range of impulse pre ssures, and the residual flexural strength and stiffness was measured by the four-point bend technique. When dynamically loaded by a shock w ave with relatively low pressure, the laminate experienced comparative ly little microstructural damage, and consequently the flexural proper ties remained unchanged. Increasing the shock wave pressure beyond a t hreshold value caused severe damage, resulting in a significant loss i n flexural strength and stiffness. This paper also presents measuremen ts of the flexural strength of GRP at strain rates between 2 x 10(-6) and 2 x 10(-1) s(-1). It is proposed that the four-point bend test met hod can be used to evaluate the resistance of GRP to damage by underwa ter shock loading, providing the strain sensitivity of the laminate is considered.