In this paper, a lamination parameter-based approach to weight optimization of composite aircraft wing structures is addressed. It is a bi-level procedure where at the top level lamination parameters and numbers of plies of the pre-defined angles (0, 90, 45 and −45°) are used as design variables, the material volume is treated as an objective function to be minimized subject to the buckling, strength and ply percentage constraints. At the bottom level the optimum stacking sequence is obtained subject to the requirements on blending and preservation of mechanical properties. To ensure composite blending, a multi-stage optimization is performed by a permutation genetic algorithm aiming at matching the lamination parameters passed from the top level optimization as well as satisfying the layup rules. Two new additional criteria, the 90°ply angle jump index and the stack homogeneity index, are introduced to control the uniformity of the three ply angles (0, 90, 45 and −45) spread throughout the stack as well as improve the stack quality and mechanical performance by encouraging 45°angle change between neighbouring groups of plies. The results of the application of this approach are Page 2 of 28 compared to published results to demonstrate the potential of the developed technique.
Keywords:Laminated composite, optimization, stacking sequence, blending, lamination parameters
IntroductionStacking sequence optimization of laminated composite structures to satisfy ply continuity (blending) requirements has recently attracted considerable attention by Gürdal et al. (1999), Kristinsdottir et al. (2001), Liu and Haftka (2001), Seresta et al. (2007), Liu and Krog (2008), Liu et al. (2011). Liu et al. (2000 presented a bi-level (global and bottom) strategy for optimization of a composite wing box structure. At the global level, continuous optimization of thicknesses of 0, 90, 45 and 45°plies was performed to minimize the weight of a wing box subject to strain and buckling constraints. For a given number of plies of each orientation and in-plane loads, a permutation genetic algorithm (GA) was used at the bottom level to optimize the stacking sequence in order to maximize the buckling load. The optimum buckling load, which was treated as a function of the loading and the numbers of plies of 0, 90, 45 and 45°orientation, was evaluated by a cubic polynomial response surface approximation. This bi-level approach was also used for maximization of buckling load of composite panels by Liu et al. (2004), layup optimization of anisotropic laminated composite panels by Bloomfield et al. (2009) and stacking sequence optimization of blended composite structures by Liu et al. (2011). The use of lamination parameters to represent the in-plane and flexural stiffness in the optimization of laminated composites was first used by Tsai et al. (1968) and later applied to the buckling optimization of orthotropic laminated plates by Fukunaga and Hirano (1982). Miki (1982), Fukunaga and Chou (1988), and Fukunaga and Sekine (1993) also u...