Optimization of Sandwich Beams for Concentrated Loads

The optimization of sandwich structures for stiffness has been considered by a number of authors, but the optimization for strength, and particularly under concentrated loading, appears to be much less well understood. Part of the difficulty is that simplified structural theories, such as classical or first order shear deformation theory, do not give sufficient accuracy under concentrated loading. In the present work, an elasticity solution is employed that agrees well with both finite element and experimental strain gage readings. It is shown that strength values from three point bend test experiments on sandwich beams with polyurethane foam cores and carbon/epoxy faces can be successfully interpreted. An algorithm is then developed that gives the optimum design of sandwich structures for strength to weight under concentrated loading.