Buckling of cylindrical sandwich shells with metal foam cores

Buckling of cylindrical sandwich shells subject to axial compression is addressed for shells having foamed metal cores. Optimal face sheet thickness, core thickness and core density are obtained which minimize the weight of a geometrically perfect shell with a specified load carrying capacity. Constraints imposed by wrinkling and yielding of the face sheets and yielding of the core are all considered. The range of the structural load index is identified for which the sandwich shells have a competitive weight advantage over stringer stiffened shells. In most of this range, the minimum weight design has elastic buckling simultaneous with face sheet yielding. Imperfection sensitivity of the shells is assessed with special emphasis on the role of plasticity in degrading strength, especially in light of the coincidence of elastic buckling and face sheet yielding in the optimally designed perfect shell. The purpose is to examine the interaction between imperfections and plastic yielding to see if buckling load knockdowns should be larger than those expected for elastic shells.