Aeroelastic Analysis of a Hingeless Rotor Blade in Forward Flight

Abstract

The aeroelastic response and stability of isotropic and composite rotor blades are investigated using a large deflection-type beam theory. The finite element equations of motion for beams undergoing arbitrary large displacements and rotations, but small strains, are obtained from Hamilton's principle. The sectional elastic constants of a composite box beam including warping deformations are determined from the refined cross-sectional finite element method. The analysis is performed for a soft-in-plane hingeless rotor in free flight propulsive trim. The nonlinear periodic blade steady response is obtained by integrating the full finite element equation in time through a coupled trim procedure with a vehicle trim. After the coupled trim response is computed, the aeroelastic response is calculated through a time-marching solution procedure under small perturbations assumption, and then the stability analysis is performed by using a moving block analysis. Numerical results of rotating natural frequencies, blade response, and aeroelastic stability are presented. The results of the full finite element analysis using the large deflection-type beam theory are quite different from those of a previously published modal analysis using the moderate deflection-type beam theory.