Optimum Design of Perforated Orthotropic and Laminated Composite Plates under in-plane loading by genetic algorithm

In this paper, the parameters influencing the stress distribution around regular polygon cutouts in orthotropic plates and symmetrical composite laminates are studied, and then the genetic algorithm is used to determine the optimal values of effective parameter for attaining the lowest normalized stress and the highest failure strength. The parameters examined for this purpose are cutout geometry, curvature radius of cutout corners, cutout orientation, fiber angle, and load angle and stacking sequence of laminated composite. An analytical method is used to calculate the stress distribution around different cutouts under different in-plane loads. Using conformal mapping and complex variable method, the Lekhnitskii’s method that is originally introduced for circular and elliptical cutouts is expanded for cutouts with different shapes. The results show that the failure strength of perforated plates can be improved by choosing the appropriate shape of cutout and the optimal values of the effective parameters. The results show that contrary to expectation, the best cutout geometry is not always a circle, as in some cases by choosing the appropriate values of bluntness parameter, cutout orientation, and stacking sequence for a laminate with non-circular cutout the failure strength higher than that of a circular cutout can be achieved.