The aeroelastic stability analysis of isotropic and composite bearingless rotors is investigated using a large deflection beam theory in hovering. The bearingless configuration consists of a single flexbeam with a wrap-around type torque tube and the pitch links located at the leading edge and trailing edge of the torque tube. The outboard main blade, flexbeam, torque tube are all assumed to be an elastic beam undergoing flap bending, lead-lag bending, elastic twist and axial deflections, which are discretized into beam finite elements. For the analysis of composite bearingless rotors, flexbeam is assumed to be a rectangular section made of laminate. Two-dimensional quasi-steady strip theory and Loewy’s aerodynamic theory with the lift deficiency function are used for unsteady aerodynamic computation. The finite element equations of motion for beams are obtained from Hamilton’s principle. Numerical results are calculated for selected bearingless blade configurations based on the lay-up of laminae in the flexbeam and pitch links location. A systematic study is made to identify the importance of the stiffness coupling terms on blades stability for various fiber orientation and for different configurations.
