Core and face-sheet anisotropy in deformation and buckling of sandwich panels

A theoretical study of the effects of face sheets anisotropy and of the transverse compressibility of the core on buckling and deformation of sandwich flat/curved panels is presented. Additionally, the effect of core orthotropy is addressed. The analysis is carried out in the context of a newly geometrically nonlinear higher-order sandwich shell model developed by the authors. An analytical solution is obtained by means of an extended Galerkin procedure. Both the overall buckling mode and the local face wrinkling instability mode are addressed. It is observed that the global and local instabilities are coupled rather than being independent features. Furthermore, the face wrinkling instability might have a considerable effect on the overall deformation behavior of the structure in the (global) prebuckling range. Both the stacking sequence of the face sheets and the orthotropicity of the core are found to have a significant effect on the occurrence of the different instability modes.