Composite Laminated Shell Structures Of Aga-fem-based Optimization Method

Composite laminate shells have been applied more and more widely in aerospace structures. In order to increase thrust to weight ratio and improve the comprehensive performance of airplane, optimization design must be carried out. This thesis brings forward utilizing the method of AGA-FEM, which combines Adaptive Genetic Algorithm (AGA) and Finite Element Method (FEM), to optimize fibre-reinforced composite shells. Based on this, optimization of an aeroengine composite case is carried out. The research work in this paper is mainly included following:(1) The method of AGA-FEM is developed. To optimize composite shells, this thesis proposes using AGA-FEM, and hierarchical design optimization method considering ply thicknesses and ply orientation angles respectively is presented. It divides the complex problem into two simple sub-problems that are easy to be solved: optimization considering ply thicknesses, optimization considering ply orientation angles. As a result, the method is capable of solving the problem concisely, efficiently and adaptively, and simultaneity it also improves the ability of searching an optimum solution.(2) Aiming at the discrete structure of composite shells, this thesis proposes two integer coding method, then uses one of them to optimize composite shells. The results are proved to be satisfactory.(3) Using AGA-FEM to minimum the mass of an aeroengine case, the results indicate that the method we improved can be adopted to optimization of engine case and other engineering components.(4) This thesis brings forward the secondary development of ANSYS and combines it with visual C++ language, which make up our computing software system. This system possesses excellent analysis ability and can be transplanted easily, the procedure code is exoteric and reusable.