Stability analysis for helicopter composite rotor blades with elastic coupling

The aeroelasticity of helicopter composite rotor blades with elastic coupling is analyzed. The structural model in this analysis includes the effects of transverse shear deformation, out-of-plane warping and aeroelastic coupling. A 21-DOF beam finite element, including transverse shear DOF and warping DOF, is developed for analysis. The governing differential equations of motion for a hingeless rotor are derived using the Hamilton's principle. Three different composite blade configurations are conducted for comparison. The results show that changes in blade frequencies are very small, however, the mode shapes are significantly changed considering elastic coupling. The blade stability in hover is strongly affected by the ply-induced composite couplings. Positive flap-torsion coupling has a stabilizing effect on the lag mode damping. Negative flap-torsion coupling has a destabilizing effect on the lag stability.