Abstract: The fabrication process has considerable effect on the performance of fully-cured composite structures. During the curing process, the process-induced residual stress and deformation are generated due to the chemical shrinkage and mismatch of thermal expansion coefficient, et al. The residual stress can potentially lower the performance of composite structures, or even leads to such defects like delamination. Therefore, it is necessary to study the influence of residual stress on the strength of composite structures. Firstly, based on anisotropic viscoelastic constitutive model, a numerical model predicting the residual stress and cure deformation of composite specimen was established. The 3D viscoelastic model was employed in this model and its corresponding finite element code was incurporated into ABAQUS, the relative error of cure deformation between numerical results and experimental data was less than 8.24%. Secondly, a strength predicting numerical model based on the Hashin damage criteria was built. The numerical results have been proved to fit the experimental data in good agreement, the relative error in strength is 9.85%. Then, the residual stress was conducted into the strength predicting model as an initial condition. Thus, the effect of residual stress on the strength of Unmanned Aerial Vehicle (UAV) composite wing structures was numerically studied. To study the effect of different residual stress level on the strength behavior of UAV composite wing structure, 2 different curing parameters were generated. The numerical results show that the residual stress is harmful for the strength behavior of this UAV composite wing structure. The numerical ultimate strength of wing structure was reduced by 3.52% due to the curing residual stress. However, the strength of the wing structure with optimized curing parameter is 1.3% higher than that of the original one.

Key words: process-induced residual stress, process-induced deformation, curing parameter, composite wing, structural strength