Optimum design of laminates with natural frequency constraints

A method of optimally designing symmetric fibre reinforced composite laminates subject to constraints on natural frequencies is presented. The problem is cast as a non-linear mathematical programming problem in which the thickenesses of material placed at preassigned orientation angles are treated as the design variables. The resulting optimization problem is solved by using an interior penalty function algorithm. Several non-linear programming problems are solved by taking minimization of weight or maximization of fundamental frequency/buckling load/maximum transverse deflection under the stated loading condition as the behaviour constraints. The numerical results are presented in the form of design studies which reveal the influence of different design constraints on the optimum design. These design studies illustrate that the method presented offers an efficient and practical optimum design procedure for composite laminates.