Thermal buckling and postbuckling of sandwich panels with a transversely flexible core

This paper deals with thermally induced deformation buckling and postbuckling of a unidirectional sandwich panel with a soft core. The mathematical formulation is based on the high-order sandwich-panel approach and it incorporates the effects ofthe flexibility of the core in the vertical direction, along with its expansion or contraction in the vertical direction as a result of the imposed thermal field. The nonlinear governing equations are derived using a variational approach following the principles of the high-order sandwich-panel theory. The governing equations of the prebuckling and buckling states are determined through linearization following a perturbation approach. The effects of the vertical thermal core normal strains of the core, which are usually ignored by various computational models, are studied at the buckling and the postbuckling stages, with emphasis on the differences in the mechanical behavior. A comparison with results obtained using a classical elastic foundation approach is conducted, and the differences are presented and discussed. The postbuckling behavior of thermally loaded sandwich panels in the vicinity of the temperatures that cause buckling, based on a simplified model, is presented through numerical examples involving a uniform temperature field, along with finite element results using ANSYS that compare very well. In addition, the results for a gradient thermal field are described. The results are presented through various structural quantities along the panel and through equilibrium path curves of temperature vs extreme values of these structural quantities. An important conclusion of the study is that the postbuckling behavior of a heated sandwich panel with a soft core is of a stable type for the cases investigated (i.e., that of a plate rather than of a column or a shell).