Composite Plates and Their Lay-Up Solutions Leading to High Buckling and Post-Buckling Resistance

Abstract

At the beginning of the present paper, the post-buckled composite plates are examined. The plates have a symmetric lay-up. The layer orientation angles vary in a point-wise way or in a plate-wise way. The von Karman theory describes a plate behavior. For a plate stiffness maximization problem the first-order optimality conditions are derived. In the conditions, the essential roles play the mid-plane principal strains and the principal curvatures. The optimality conditions may lead to a co-axiality of some structural tensors. Analytical examples illustrate the solutions of such types. Further, several numerical examples are presented. In the examples, the plates are loaded by shear and have the high buckling-resisting ability also. A significant conclusion of the paper is that in the properly designed lay-up the outermost layers and the innermost layers play different roles. The former ones withstand mainly buckling, and the latter ones withstand mainly post-buckling. The innermost layers have the orientation angle rather close to 0°. The weight reduction opportunities are demonstrated.