Abstract: The finite element method is used to simulate the varying process of temperature, curing degree and thermal stress in the co-curing process of thick-sectioned resin matrix composite patch with mother board, and the correctness of the numerical methodology is verified by comparison with the experimental results. The effects of scarf slope, fiber orientation and fiber layup order on distributions of temperature and thermal stress field in patch at different stages during curing process are studied. The results show that the slope of scarf has a great influence on the thermal stress in the patch during the heating and isothermal stages, and has little effect on the thermal stress of the patch at the end of cooling. Increasing the scarf slope can reduce the thermal stress of the patch during the heating and isothermal stages, and can also avoid large thermal stress concentration. During the whole curing process, the residual thermal stress in the patches is the smallest with 0° fiber orientation while the value is the largest with 90° fiber orientation, and there is a strong stress concentration at the center of the top of the patches corresponding to the latter one. In order to reduce the residual thermal stress, the orientation of the fibers should be parallel to the contact surface of the patch with the motherboard, i.e. perpendicular to the direction constrained by the motherboard. Symmetric ply patches have less thermal stress throughout the curing process, while thermal stresses are greater in the patches with sequential spacer plies and anti-symmetric plies. Symmetry ply design principles should be used for resin matrix composites patch plies.

Key words: scarf repair, process parameters, thick-sectioned resin matrix composites, temperature field, thermal stress