Molding simulation of airfoil foam sandwich structure and interference optimization of foam-core

During the Co-Cure Molding (CCM) of airfoil foam sandwich structure, it is challenging to avoid collapse of foam core at the trailing edge. Herein, an Equal Proportional Thickening (EPT) method is proposed to optimize the interference of polymethacrylimide (PMI) foam core during the CCM process. Firstly, based on some basic parameters of composite skin and foam core obtained by experiments or multi-scale simulations, a thermal-curing-mechanical coupling analysis for the CCM of foam sandwich structure is performed and the results show that the maximum stress within foam core occurs at the completion of mold-closing, which tends to decrease during the subsequent CCM process. Then, the foam core is thickened by traditional equidistant-thickening method, and the simulation reveals that the foam core at the trailing edge tends to collapse because of stress concentration. Conversely, if the foam core is thickened by the proposed EPT method, the mold-closing caused collapse at the trailing edge can be effectively avoided, and a thickening ratio range of 0.6%- 2.0% is obtained, which is further proved by practical verifications. Therefore, the interference design scheme proposed can ensure the molding quality and effectively reduce the scrap of molded products.