High-order behavior of fully bonded and delaminated circular sandwich plates with laminated face sheets and a “soft” core

The bending behavior of circular, fully or partially bonded (delaminated), sandwich plates with a ‘‘soft’’ core and composite laminated face sheets of general layup is investigated. The analytical model derived follows the principles of the High-Order Sandwich Plate Theory and it is based on equilibrium and compatibility requirements. The variational principle of virtual work is employed for the derivation of the field equations along with the boundary and continuity conditions. The delamination considered forms a penny shaped disbonded zone, in which the delaminated faces can slip horizontally with respect one to another, yet they may be in contact accommodating vertical normal compressive stresses. The core is assumed a 3D elastic medium and the composite face sheets are modeled using the classical lamination theory, which yields coordinate dependent constitutive relations. The governing equations take the form of partial differential equations with variable coefficients. The solution procedure adopts the Galerkin method with truncated Fourier series in the circumferential direction and the multiple-points shooting method in the radial direction. Numerical results concerning typical fully and partially bonded sandwich plates are presented and discussed. The results reveal the effect of the anisotropy of the face sheets on the response of the structure and the influence of the delaminated area on the behavior of the sandwich plate