Material selection for CFRP-aluminium-foam-sandwiches manufactured by a PUR spraying process

Sandwich structures are ideal for planar parts which require a high bending stiffness at a low weight. Usually, sandwich structures are manufactured using a joining step, in which the face sheets and the core are connected. The PUR spraying process allows to include the infiltration of the face sheet fibres, the curing of the matrix and the joining of the face sheets to the core within one process step. Furthermore, this manufacturing process allows for the use of open cell core structures without infiltrating the core, which enables a comparison of different material configurations, assembled by the same manufacturing process. The selection of these materials, with the aim of the lowest possible mass of the sandwich composite at a constant bending stiffness, is displayed systematically within this work. It could be shown that the bending modulus calculated from the component properties matched the experimentally achieved values well, with only few exceptions. The optimum of the bending modulus, the face sheet thickness and the resulting effective density could be calculated and also matched the experimental values well. The mass-specific bending stiffness of the sandwich composites with core structures of open cell aluminium foams was higher than with closed cell aluminium foams, but was exceeded by sandwich composites with Nomex honeycomb cores.