Sandwich column buckling – A hyperelastic formulation

The macro-buckling equations for a sandwich column are developed. A layer-wise Timoshenko beam displacement approximation is assumed. The constitutive relationships and equilibrium equations for the core and face sheets are derived using a consistent hyperelastic neo-Hookean formulation. The derivations in this paper are consistent with that of Haringx’s and Reissner’s proposal for beam actions. The buckling formulation includes the axial deformation prior to buckling and the transverse shear deformation of the core and face sheets. The buckling equations derived agree with the equation of [Allen, H.G., 1969. Analysis and Design of Structural Sandwich Panels, Pergamon, Oxford] for thick faces but are also applicable to any ratio of face sheet to core thickness and material properties. The formulation is compared to experimental results for sandwich columns and shows good comparison except for very short columns. The formulation is also compared to the buckling experimental results for short rubber rods and also compared well. The formulation does not predict a shear buckling mode.