A unified formulation for the biaxial local and global buckling analysis of sandwich panels

Sandwich structures are increasingly employed in many practical applications thanks to their interesting compromise between lightweight and high mechanical properties. However, due to some specific geometric and material features, such structures are subject to global as well as local buckling phenomena, which lead to collapse in most cases. The buckling analysis of sandwich panels is therefore an important issue for their mechanical design. In this respect, this paper is devoted to the theoretical study of the elastic local/global buckling of rectangular sandwich plates under uniaxial or biaxial compression(-tension). Only classical sandwich materials are considered with homogeneous and isotropic core/skin layers. In the present formulation, a Love–Kirchhoff plate model is used to represent the thin skins, whereas the relatively thick core is modeled as a 3D continuous solid. Furthermore, the proposed approach is based on the elastic bifurcation theory in a general 3D framework, and leads to closed-form analytical expressions of the critical loadings and the corresponding bifurcation modes. The accuracy of the derived formulae is checked for both local and global modes by comparison with the results of finite element computations. Parametric analyses are finally performed, investigating primarily the influence of the aspect ratio of the plate and the ratio of the compressive (or tensile) loadings between both directions on the first buckling mode type and the associated minimum critical value.