Comparison of gradient-based and gradient-free methods for optimal stacking sequence of composites

This paper deals with the solution of the optimal stacking sequence problem for laminated composite structures made of conventional plies oriented at 0°, 45°, 90° and -45°. A constraint of the optimization problem is to be able to take into account the classical design rules, such as a minimum amount of each kind of orientation must be present in the laminate, which moreover must be balanced and symmetric. Two optimization approaches are compared. The first one is based on a discrete formulation of the problem, which can directly solve the combinatorial optimization problem. In the second approach, continuous design variables are used, with a specific parameterization of the material properties based on a multi-phase topology optimization formulation. The efficiency of the approaches is compared on a representative test case, which consists of a panel submitted to buckling.