Buckling of sandwich panels with a flexible core-high-order theory

The buckling behavior of sandwich panels with a core that is flexible in the out-of-plane direction, also denoted as ''soft'' core including high-order effects, is presented. The buckling analysis consists of the formulation of the linear and the nonlinear governing equations along with the boundary conditions. The sandwich panel construction is general and consists of two skin-panels, metallic or composite laminated symmetric that may be unidentical and a flexible isotropic or orthotropic core made of foam or a low strength honeycomb. The analysis uses a high-order theory formulation, which permits nonlinear distortions of the cross-section plane of the core as well as changes in its height. The analysis determines the bifurcation loads along with the associated mode shapes, local or overall buckling modes, as well as deformations, internal resultants and stresses al skin-core interface layers due to imperfections. Numerical results using closed form solutions for simply-supported panels, with identical and non-identical skin-panels subjected to compressive inplane loads as well as imperfection analysis results, are presented. The results reveal that, under some structural configurations,the local buckling mode is a critical, rather than a global one as a result of the out-of-plane flexibility of the core. (C) 1997 Elsevier Science Ltd.