Flutter analysis of a high-aspect-ratio sandwich wing under large angle of attack

The semi-analytical expressions are established first for the coupled modes of bending and torsion of a high-aspect-ratio composite beam, and then the dynamic equations of a high-aspect-ratio sandwich wing with NACA0012 airfoil shape are derived in modal space. A semi-empirical and nonlinear aerodynamic model ONERA is employed to model aerodynamics that the nonlinear aeroelastic problem of a sandwich wing is well defined. The nonlinear flutter boundary of the sandwich wing is obtained by jointly running structural solver and aerodynamic solver. In order to validate the presented method, the linear flutter equations of the sandwich wing are established using the linear part of the ONERA model. The numerical results show that the linear flutter speed agrees well with those predicted by the method of the nonlinear analysis. The flutter speed decreases rapidly with an increase of the root angle of attack, and the flutter speed of the sandwich wing is significantly influenced by laminate ply angles.