BUCKLING OF UNILATERALLY CONSTRAINED PLATES - APPLICATIONS TO THE STUDY OF DELAMINATIONS IN LAYERED STRUCTURES

The results from a combined experimental and analytical investigation of the problem of buckling of unilaterally constrained finite rectangu lar, elastic plates is reported. The plates are modeled along the line s of classical plate theory employing the Kirchhoff-Love hypothesis. T he presence of a unilateral constraint is accounted for through the us e of a nonlinear elastic foundation model that exhibits a deformation sign dependent force-displacement relation. Using Galerkin's method, t he resulting system of governing nonlinear equations ai e solved itera tively. Different boundary conditions are considered and the results f or some boundary conditions ai e compared and shown to be in good agre ement with 'exact' results reported earlier for infinite plates. The r esults fi om an experimental investigation has further revealed that t he buckling mode of the plate may involve regions ol points of contact with the substrate beneath the buckling plate. The shadow Moire techn ique is used to show clearly that the mode shape is periodic and conta ins points and/or regions of contact. The results obtained from the th eoretical investigation are found to bound the experimental values. It is clear that the stiffness of a post-buckled plate with unilateral c onstraints is highly influenced by whether the buckled portion involve s points (ol regions) of contact or not. Thus, in analytical model dev elopment, associated with addressing the problem of delamination buckl ing in layered plates, the possibility of the delaminated portion cont acting the substrate beneath cannot be excluded. The present study has demonstrated the validity of using nonlinear foundation models in the buckling analysis of unilaterally constrained rectangular plates. (C) 1998 The Franklin Institute. Published by Elsevier Science Ltd.