On wrinkling of a sandwich panel with a compliant core and self-equilibrated loads

The nonlinear response of a unidirectional sandwich panel that is associated with wrinkling of the face sheets, due to a self-equilibrated loading scheme is presented. This loading scheme may be a results of a manufacturing process where the core is tensioned first and the sandwich panel is formed through bonding of the face sheets to the tensioned core while wrinkling occurs as a result of the release of the tensile force of the core, i.e. similar to the manufacturing of electroactive polymers (EAPs) [Wantanaba et al. (2002)] or due to prestressing of the core which is associated with the pre-strain the edge of the core only. These self-equilibrated loads yield compression in the face sheets as well as in the core which may be associated with loss of stability as a result of overall buckling of the entire panel or wrinkling of the face sheets. Thus, for such loading scheme the longitudinal rigidity of the core must be considered although it is small as compared with that of the face sheets. The governing equations along with the appropriate boundary conditions are derived through the introduction of longitudinal normal stresses in the core along with high-order distribution functions for the displacements through its depth. The mathematical formulation is based on variational principles along with moderate type of deformations for the kinematic relations. The results of the various structural quantities in the form of curves along the panel, equilibrium curves and deformed shapes for a particular sandwich panel are presented. The study discusses the effects of the transfer of the compressive load from the core to the face sheets, either directly through an edge beam or without it. Conclusions are drawn and presented.