Aeroelastic stability of composite hingeless rotor blades in hover—Part II: Results

Abstract

In Part I of this two-part paper, an aeroelastic stability analysis was presented for isolated hingeless, composite rotor blades in the hovering flight condition, which was based on a mixed finite element method. Herein, the focus is to present numerical results obtained from this analysis. First, certain of these results are compared with those of existing aeroelastic stability analyses for validation. Next, the numerical accuracy and convergence characteristics of the current approach are quantified. Finally, parametric studies are performed to investigate the effects of composite elastic coupling and thrust condition on the blade's aeroelastic stability, especially that of the lightly damped lead-lag mode. The stability of some of the elastically coupled cases studied was sensitive to the nonclassical couplings; indeed, in one case a significant error appeared, accentuated at high thrust levels, when bending-shear coupling was neglected. Another significant effect stems from changes in the equilibrium solution for elastic twist due to extension-twist coupling. The necessity of including such effects in the blade model for general-purpose analysis is noted.