Composite plate optimization only requires one parameter

Abstract

The object of the study was to optimize composite plates concerning free vibration frequencies, buckling loads, and deflections under constant pressure. Layups without coupling between bending and extension but otherwise arbitrary selection of the ply angle variation through the thickness of the laminate were included. For these plates, four different boundary conditions were studied. The number of relevant parameters was successively reduced from the initial six bending stiffnesses that any laminate has. Bending-twisting coupling has only negative influence on fundamental eigenfrequency, buckling load and average deflection under a constant pressure, so the number of parameters could be reduced by two. The remaining four parameters are not independent, but are functions of only two independent parameters, the flexural lamination parameters. It was further seen that the optimal designs always were found on the boundary of the allowable region of the flexural lamination parameters, i.e. there is only one relevant parameter for the optimization problems. This parameter can be interpreted as the layup angle (Θ) in an orthotropic (+/ − Θ) laminate.