Aeroelastic stability analysis of composite hingeless rotor based on free-wake model

Based on finite element method (FEM) and free-wake method, an aeroelastic stability analysis model of composite hingeless rotor was developed. In order to simulate the aeroelastic behavior of composite rotor, 2-D linear FEM analysis was employed to obtain the sectional properties, and 1-D beam was modeled by 23 degree of freedom (DOF) nonlinear beam element which included transverse shears. The free-wake model was adopted to calculate non-uniform induced velocity field, and a highly-efficient and accurate aerodynamics analysis module was established by using lifting-line theory. On the basis of these, the stability analysis for composite hingless rotor was carried out. It is demonstrated by numerical simulation that the present model is capable to predict unsteady airloads and aeroelastic stability characteristics of composite rotor. Finally, the effect of material ply orientation on hingless rotor aeroelastic stability was analyzed, and it can be seen from the results that under the condition of low thrust coefficient (0.0025), the rotor aeroelastic instability may occur when ply angle of the vertical wall varies between 10°and 25°, which should be avoided in rotor design.