Optimal Design of Laminated-Composite Circular-Cylindrical Shells Subjected to Combined Loads

Optimization of the buckling load of a laminated-composite, circular-cylindrical shell subjected to axial compression, external pressure, torsion, or a combination thereof is undertaken. In the optimization procedure it is assumed that the shell has a fixed weight (length, radius and thickness); the buckling load is taken as the objective function which is maximized by adopting the lamina fiber orientations as the optimizing parameters. For the shell analysis a perturbation approach is used and the boundary conditions and nonlinear prebuckling effects are included; the analysis yields both the buckling load and the post-buckling character of the shell. The procedure developed is demonstrated for eight loading configurations. In addition, selected laminates were chosen for an experimental programme involving a series of graphite/epoxy shells. The predicted analytical and the measured experimental buckling loads are in very good agreement.