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 de ection-type beam theory. The Ž nite element equations of motion for beams undergoing arbitrary large displacements and rotations,but small strains, are obtained fromHamilton’s principle. The sectional elastic constants of a composite box beam including warping deformations are determined from the reŽ ned cross-sectional Ž nite element method. The analysis is performed for a soft-in-plane hingeless rotor in free  ight propulsive trim. The nonlinear periodic blade steady response is obtained by integrating the full Ž nite 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 Ž nite element analysis using the large de ection-type beam theory are quite different from those of a previously published modal analysis using the moderate de ection-type beam theory.