Buckling optimization of variable thickness composite plates subjected to uncertain thermal and mechanical loadings

Abstract

Composite rectangular plates are traditionally optimized for buckling assuming that perfectly uniform loadings are applied. However, this assumption is clearly not realistic for composite structures in real applications, particularly when the multiplicity of potential load cases is considered. Composite plate optimization is addressed differently in this paper: the loading distribution is not assumed to be uniform but it is allowed to vary within an admissible set, conferring uncertainty to the applied loads. The admissible load space comprises loadings that can be represented through a collection of piecewise linear functions defined along the plate edges. The uncertainty of the loading is treated with the aid of a minimax formulation where the loading configuration and piecewise constant plate thicknesses are taken simultaneously as design variables. The choice of design variables imply in variable thickness non-homogeneous composite plates characterized by nonzero thermal residual stresses, inherited from the thermal processing. These residual stresses must also be accounted for in the buckling calculation as they significantly affect elastic behavior of the plate. The optimal composite plates obtained by the present optimization strategy satisfactorily withstand not only perfectly uniform loadings but an entire class of piecewise linear loadings. Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.