Optimal design of composite sandwich structures by considering multiple structure cases

Acting as primary and secondary structures, sandwich components made of laminated composite face sheets are widely applied in aerospace structures. For simultaneous optimization designs of both stacking sequences of the face sheets and the core thickness, the design problem for composite sandwich structures becomes a combinatorial one by involving both discrete and continuous design variables, for orientation angles of the face-sheet laminate plies are constrained to discrete permissible designs while the core thickness is continuous. Additionally, practical structures like solar arrays are required to satisfy given constraints under multiple structure cases, which involve multiple finite element models and make the problem more complicated. In this study, for optimal designs of composite sandwich structures under multiple structure cases, an optimization model is firstly established by involving both discrete and continuous variables meanwhile integrating all structural cases into a single problem formulation. A stacking sequence optimization method proposed previously by the authors which utilizes two-level approximations and a genetic algorithm is extended to solve the above problem, and an optimization framework is developed by interfacing the improved method with the finite element software MSC.Patran/Nastran. Numerical applications are conducted to demonstrate the feasibility of this optimization system.