The effect of elevated temperatures on the bending behaviour of foam cored sandwich structures

The influence of elevated temperatures on the bending response of polymer foam cored sandwich structures is investigated. A new analytical model is proposed that enables the calculation of the stress/strain and deflection of sandwich beams subjected to load and elevated temperatures. The model is based on the classical sandwich beam theory, but the effect of a through thickness temperature gradient is accounted for by imposing different stiffnesses of the core for different temperatures. The sandwich beam specimen studied in the paper is loaded in a simply supported three-point bending configuration, where one of the face sheets is heated. The experimental approach utilises digital image correlation to obtain the point deflection of the specimen and more importantly to characterise the nonuniform deformation of the core. The results from the new analytical method agree well with corresponding experimental results for the beam deflection and core shear strain. It is found that the core shear stress remains uniform in the through thickness direction despite the temperature gradient and resulting stiffness gradient. Thereby the core shear yielding is initiated from the area with the highest temperature in the sandwich beam cross-section due to the reduction of core yield strength with increasing temperature.