Analysis of smooth characteristics of flexible skin for variable-sweep wing considering creep

Abstract:

To meet the requirement of smooth continuity during the deformation process of the shear-type variable-sweep wing, this paper proposed a flexible skin structure using pre-stretched silicone rubber as the shape-maintaining surface layer. To ensure that the skin maintains smooth continuity within the variation range of the wing sweep angle, this paper investigated the critical shear angle for skin smoothness and wrinkling. First, based on a three-parameter solid model characterizing creep behavior and a dimensionless normalization analysis method, this paper established a viscoelasticity prediction model of the silicone rubber surface layer. Second, according to the minimum stress criterion, this paper established a critical model considering the viscoelasticity of the silicone rubber surface layer, completed the calculation of the critical shear angle of the pre-stretched flexible skin, and proposed an empirical formula for solving the critical shear angle. Finally, this paper simulated and analyzed the critical shear angles of skins with different pre-stretching amounts using the finite element method, generated tensile deformation by applying displacements along the x and y directions, and generated shear deformation by applying rotation and displacement along the diagonal direction. The results indicate that within a large tensile strain range, the viscoelastic model of the silicone rubber surface layer can accurately describe the static creep behavior of the silicone rubber, and the critical shear angle model for the smoothness of the pre-stretched flexible skin considering the viscoelasticity of the silicone rubber surface layer has high accuracy; the pre-stretching amount and the creep characteristics of the silicone rubber surface layer have a significant impact on the critical shear angle, and biaxial stretching is beneficial to improve the anti-wrinkling ability of the skin, thereby maintaining surface smoothness during the variable-sweep process. The theoretical prediction results agree well with the simulation results and experimental results, which has great value for the engineering application of the shear-type variable-sweep wing.