Abstract: High-aspect-ratio wing undergoes large deflections under aerodynamic force, and these large deflections can noticeably change the wing's flutter speed and frequency. Linear analysis methods usually yield unreasonable results for this problem. Dynamic equations are built up with composite wing being modeled as thin-wall box beam, and geometric nonlinearity, aerodynamic nonlinearity as well as stiffness coupling are simultaneously involved in it. Vibration equations are deduced through perturbing the dynamic equations at wing's equilibrium position. Flutter equations are obtained by using Theodorsen's unsteady aerodynamic theory, then flutter stabilities at various wind speeds are determined by the v-g method. Several examples show the distinguished differences between results from nonlinear flutter analysis and one from linear flutter analysis. Variations of flutter speed with wing parameters, such as ply angle, aspect ratio and mass per unit length, are also discussed.

Key words: high-aspect-ratio wing, geometric nonlinearity, flutter, composite material, thin-walled closed section beam