The aeroelastic response and stability of isotropic and composite rotor blades are investigated using a large
de ection-type beam theory. The 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 re ned cross-sectional 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 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 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.