Isogeometric analysis and design of variable-stiffness aircraft panels with multiple cutouts by level set method

For composite panels with cutouts, curvilinear fiber path can adjust the in-plane stiffness distribution to increase the buckling resistance, but it results in huge computational cost for the buckling analysis when FEA is employed. In this study, variable-stiffness panels with cutouts are analyzed via isogeometric method, where cutouts are represented by the level set method. The method for suppressing artificial buckling modes is proposed to improve the prediction accuracy. Moreover, the analytical sensitivity is derived to facilitate fiber path optimization, and a new bi-level optimization framework considering manufacturing constraints is established. Finally, the proposed method is verified by variable-stiffness aircraft panel with multiple cutouts, which can not only provide an accurate prediction of buckling load, but also exhibit high convergence rate and low computational cost for fiber path optimization.