Optimization methodology of composite panels

Abstract

This paper deals with mass optimisation of composite laminates aeronautical structures. It focuses on the final stage of the process of composite structure design i.e. defining the lay-up evolution all over the panel, this being directly used for manufacturing. Strength criteria (in-plane behaviour) and stability criteria (out-of-plane behaviour) performed with appropriate industrial tools are evaluated in the multi-level optimisation presented hereafter. The methodology consists in five steps. In the first two steps, optimisation is performed with continuous variables and a homogenized material (i.e. with approached out of plane properties). In the third step, a lay-up table is selected (or built) and translated into a "continuous" material (i.e. out of plane stiffnesses expressed as continuous variables of the lay-up thickness). In the fourth step, optimisation is performed with the "continuous" material. In the last step, a genetic optimisation is used to round off at discrete ply thicknesses. This methodology provides a manufacturable result (in terms of ply continuity) that satisfies all stress and stacking sequence constraints.