Geometrical nonlinear deformation effects in composite sandwich plates subjected to in-plane shear loads

An experimental and analytical study is presented to investigate the nonlinear behavior of foam core sandwich plates subjected to in-plane shear loads. Due to the low flexural stiffness of sandwich structures, the geometrical nonlinear deformation effects tend to appear earlier in foam core sandwich plates than in other laminated and sandwich plates. However, the analysis performed is applicable to any laminated or sandwich composite plate. In studies presented herein the Theorem of Minimum Potential Energy has been used to determine the deflections, strains, and stresses in the plate. Polynomial functions are used that satisfy all of the boundary conditions. It is seen from the analytical results that the lateral deflection and the in-plane shear strains and stresses are nonlinear functions of the applied loads. In addition, the in-plane normal strains do occur under the laterally applied loads which cause the inequality of principle strains between the compressive face strains and the tensile face strains.