Analysis of sandwich plates with compressible core using layerwise refined plate theory and interface stress continuity

Lightweight sandwich materials are essential in construction in aircraft, spacecraft, and marine applications. Foam core sandwich materials are not only lightweight but extremely good in thermal insulation purposes. In construction of marine vehicles (i.e., boats, yachts), some sport goods (i.e., surf board), and in the packaging industry soft foam core (i.e., polyvinyl chloride (PVC), polyurethane, polystyrene) sandwiches are used. Polymeric or organic foam core sandwiches are being used in National Aeronautics and Space Administration spacecraft for shock absorption under impact from meteoroid and multilayer thermal insulation. High fidelity analysis tools for sandwich materials are in demand by the engineering community. An attempt has been made here to analyze a sandwich plate considering a three-layer approach using refined higher order plate theory for all the three layers. Moreover, the compressibility (i.e., thickness strain) of the central thick core layer has been considered in the analysis. The continuity of displacements and stresses at each layer interface has also been taken into account in the formulation using Lagrangian multiplier approach. The aforementioned theory has been implemented in an in-house Fortran code. Using this approach, various polymer composite and sandwich plates have been analyzed and the results are compared with other reliable published results. The correlations are found to be good for plates with various aspect ratios and ply orientations.