Delamination Buckling Inst ability Near a Circular Hole in Laminated Composite Plates

The motivation for the present study stems from the importance of delamination buckling as a viable mode of failure in laminated composite plates. This part of the study focuses on the prediction of the buckling loads and modes of unilaterally constrained rectangular plates. The laminated plates were modeled along the lines of classical lamination plate theory. Due to the out-of-plane thickness ratio of the delaminated near surface plies to that of the sublaminate (parent), the sublaminate was modeled as an infinitely rigid foundation which constrained the plate's out-of-plane response t o be of one sign. The foundation was modeled as extensional springs exhibiting a nonlinear force-displacement relationship such that its stiffness as well as the plate's buckling mode sign can be controlled in a continuous fashion allowing the simulation of a rigid and tensionless foundation. Preliminary investigations of the buckling loads and modes of rectangular plates attached to such foundations and subjected to a uniform inplane stress field showed the validity of this model for the cases investigated and compared t o previous exact results reported in the literature.