The design of laminates having the minimum number of layers for obtaining given elastic properties is addressed in the paper. The topic of this study is the fact that the problem is treated and solved in a general case, since no simplifying hypotheses are made on the type of the stacking sequence. The problem is stated as a non-linear programming problem, where a unique objective function includes all the requirements to be satisfied by the solutions. The optimal solutions are found in the framework of the polar-genetic approach, since the objective function is written in terms of the laminate's polar parameters, while a non-classical genetic algorithm is used as optimization scheme. The optimization variables include the number of layers, layer orientations and layer thicknesses. In order to include the number of plies among the design variables, some modification of the genetic algorithm have been done, and new genetic operators have been developed. Some examples and numerical results, concerning the design of laminates with the minimum number of layers for obtaining some prescribed elastic symmetries, like orthotropy, bending-extension uncoupling, quasi-homogeneity and so on, are shown in the paper.
