Optimization Design Of Composite Laminates With A Hole To Strengthen Load-carrying Capacity

Composite material has been widely used in aviation and aerospace industry because of its high ratioes of strength and stiffness. Especially in recent years, more and more composite material is used in the new designed plane. F-22 is a new generation fighter of America, and the composite material takes a percentage of 24 percent of its total structure weight. Half of the structure weight of Boeing 787 is also composite material. Composite laminate is used most among all types of composite material, it has good design control property. Because of the checking, repairing and the pipe getting across, aerocraft structure should have a series of holes. For composite laminate, holes existing will cut the fiber and lower the load–carrying capacity. we should strengthen the area around the hole to recover structure's load-carrying capacity.In this thesis, the optimization method of repairing patch is used to strengthen the composite laminate for a hole exists. For the rectangular hole, the shape parameters and thickness of each orientation for repairing patch are studied and optimized. Firstly, we choose discrete design points based on experiment design of iSIGHT; Then, build FEA optimization model for each experiment design point using PATRAN,and according to NASTRAN, the optimum thickness of each layer for the patch and the structure weight will be got; After then, based on the weight response of each design point, we can build approximate model for the weight, and optimize it using sequential quadratic program to get the optimum shape parameters; At last, building FEA optimization model and calculating it once more time based on optimum shape parameters, the optimum thickness of the layers will be got and we also do something with the results to satisfy engineering requirements. Using this optimization method, we optimize the repairing patch for the retangular hole exists of the skin under tension and compression load respectively to recover its load-carrying capacity. The result shows that the strengthening method can obviously reduce the structure weight and solve the engineering problem. The method can be widely used. Not only in the skin, but also in some other positions and other types hole can adopt this method.