Failure Analysis and Optimization Design of Wing Skin Unbalanced Lay-Up

Abstract

To clarify the influence of the unbalanced coefficient and the change in lay-up angle on the failure characteristics of the laminate in the static aeroelastic problem of the aircraft, numerical simulations were performed based on the classical laminate theory and the Tsai-Wu failure criterion, as well as the fluid-structure coupling calculation method. The structure’s stress-strain and failure curves are found to decrease as the unbalanced coefficient increases. The stress curve’s slope is relatively stable, whereas the strain and failure curves’ slopes change three times, indicating that strain may be the primary cause of structural failure. Unbalanced coefficient laminates are classified into three types based on their mechanical properties low unbalanced coefficient laminates (Unbalanced coefficient 0.2 to 0.3), quasi-balanced coefficient laminates (Unbalanced coefficient 0.4 to 0.6, Balanced laminate when the Unbalanced coefficient is 0.5), and high unbalanced coefficient laminates (Unbalanced coefficient 0.7 to 0.8). Within their respective spanning intervals, the mechanical properties of the three types of laminates remain relatively stable. An increase in the ply angle reduces both the elastic deformation of the structure and the failure factor. The variation patterns of structural strain and failure at 45° and 60° ply angles decrease as unbalanced coefficients increase, whereas the opposite is true for 30° ply angles. Finally, a two-level optimization method based on “equalized plies” and “equal-angle plies” was developed, resulting in a 23.93% reduction in elastic deformation and a 37.04% reduction in the laminated structure's failure coefficient when compared to the preoptimization results.