Optimum Design Of Composite Payload Bearing Structur On The Launch Vehicle Acceleration Stage

Instrument compartment of launch vehicle is located on the upside of the acceleration stage, next to the payloads. Payload bearing structures are installed on the top of instrument compartments in order to bear payloads of launch vehicle. Cross beam structures have been widely used as payloads bearing structures in acceleration stages of launch vehicle. Because of the application condition and environment, aerospace products material must have the high requirements of light weight, high strength, heat-resistant and heat-insulation anticorrosion. Advanced composites materials have the advantages of high specific intensity, high specific rigidity, better designability, excellent corrosion-resistance and strong vibration resistance. Due to the superior performance of CM, the design for cross beam from advanced composite materials of launch vehicle acceleration stage is proposed.The environment around the spacecraft is different from those of the aircraft or other machineries, therefore the design of spacecraft structures should meet the requirements for general machinery design but also better stiffness, weight and stability characters. In this paper, in order to obtain the minimum weight and meet the requirements for strength, stiffness and stability, a two-level design method based on equivalent model and surrogate model is used to provide the structural layout optimization of composite cross beam structure on the launch vehicle acceleration stage. First, the initial samples of design parameter are created by design of experiment (DOE), the finite element equivalent models corresponding to the samples are built with PCL (Patran Command Language), and the responses are obtained by finite element analysis using the software NASTRAN, then the response surface model is derived through the samples and the responses by iSIGHT. The optimal solution is obtained with multi-island genetic algorithm (MIGA) and sequential quadratic programming method (SQP) based on the response surface model. At last, optimum thickness and stacking sequences of cross-sectional were obtained by using iterative optimization and the software NASTRAN. In this paper an optimization method of the cross beam is proposed and it provides a reference for engineering design.