Pre- and postbuckling finite element analysis of curved composite and sandwich panels

Abstract

A three-dimensional degenerated isoparametric multilayer finite element is described in conjunction with an automatic incremental/iterative method to find the complete nonlinear response of arbitrarily laminated composite and sandwich panels under destabilizing loads. The case of thick sandwich panels is investigated by comparing three different models: 1) a high-order, multilayer shell element, 2) a multilayer shell element with null transverse shear moduli in the skins layers, and 3) a superposition of multilayer isoparametric membranes for the skins, and a volume element for the core. All these models allow the accurate representation of the cross-section warping in thick shear deformable sandwich panels and, after some validation tests, the model (3) is found to be the most efficient. In the prebuckling range of the structural response, incremental bifurcation analyses are combined with an arc-length algorithm to control the step size; for the postbuckling path, the increment size is determined automatically by a new recurrence formula. The good behavior of this proposed procedure is illustrated on two structural postbuckling applications, namely, a highly curved cylindrical composite panel and a sandwich panel with flange edges both subjected to in-plane compression.