AEROELASTIC STABILITY OF COMPOSITE HINGELESS ROTOR BLADES IN HOVER .1. THEORY

A finite-element-based stability analysis is presented for isolated hi ngeless, composite rotor blades in the hovering flight condition. The formulation is comprised of separate, but compatible, cross-sectional (two-dimensional) and global or beam (one-dimensional) equations. The sectional analyses used account for all possible deformation in the th ree-dimensional representation of the blade. The global analysis is ba sed on a mixed variational statement for the dynamics of moving beams; it can account for 6 x 6 cross-sectional stiffness and inertia matric es which, respectively, allow for the treatment of shear deformation a nd rotary inertia. There are no restrictions on the magnitudes of the displacements and rotations if the strain remains small compared to un ity. The lift, drag, and pitching moment models are based on two-dimen sional, quasi-steady strip theory, with induced inflow taken from mome ntum theory. The equilibrium operating configuration of the blade is o btained by an iterative solution of the complete nonlinear equations. The dynamic equations are linearized about this position, yielding an eigenproblem. In Part II, numerical results are presented for both ext ension-twist and bending-twist coupled rotor blades, which indicate th at certain ''nonclassical'' couplings must be included in the analysis in general.