Global Sensitivity Analysis of Parameters During Cure Process of SRM Composite Case

The case for modern solid rocket motor (SRM) is a complex compose structure with fiber reinforced resin matrix composite, insulation layer and metal connections, the case forming process is a multi-physical–chemical process which involving heat transfer, chemical reaction and structure deformation. During the cure process, temperature determines whether the case cure completely and the uniformity of temperature field is an important factor in causing residual thermal stress and shrinkage stress, so temperature field is the key to the mutual coupling effect of each physical and chemical process, and the basis to analyze the cure process of the case. During the cure process of case, fluctuation of cure temperature, cure time or heat transfer of hot air in the furnace may occur, which make the actual forming process of case deviate from the ideal cure process. In order to investigate the sensitive degree of thermal cycle, convective heat transfer coefficient and thermal properties to cure uniformity during cure process of composite case, the influence rule of the three factors on uniformity of temperature and cure degree fields were analyzed by numerical simulation. A thermal-chemical model was built for a simplified composite SRM case firstly, and the model was verified. Then, the influence degree of the three factors on cure uniformity of composite case was analyzed and quantized by the Morris global sensitivity analysis method. The results show that he sensitivity order of the uniformity of temperature field for the four parameters is: thermal diffusion coefficient > heat transfer coefficient > duration time > cure temperature. Besides, he temperature and duration time of the fourth dwell stage have less effect on the cure uniformity of composite case than that of heat transfer coefficient. Therefore, it is a challenge to design a thermal cycle that can not only guarantee the vulcanization of EPDM insulation layer, but also improve the cure uniformity.