The response of clamped sandwich beams subjected to shock loading

The dynamic response of monolithic and sandwich beams made from stainless steel is determined by loading the end-clamped beams at mid-span with metal foam projectiles. The sandwich beams comprise stainless-steel pyramidal cores (with no axial stretch resistance), stainless-steel corrugated cores (with a high stretch resistance) and an aluminium alloy metal foam. High-speed photography is used to measure the transient transverse deflection of the beams. The resistance to shock loading is measured by the permanent transverse deflection at the mid-span of the beams for a fixed magnitude of projectile momentum and mass of beam. It is found that the sandwich beam with the pyramidal core was the weakest of the sandwich beams, but all sandwich beams had a higher shock resistance, then the monolithic beam. For each type of beam, the dependence of transverse deflection upon the magnitude of the projectile momentum is measured. A comparison of the measurements is made with analytical predictions for both impulsive and finite pressure loading. It is found that the impulsive loading analysis over-predicts the deflections of both the monolithic and sandwich beams. The finite pressure analysis, which considers the transient nature of the loading pressure provided by the foam projectile, can accurately predict the measured transverse deflection.