Stability analysis for hel icopter composite rotor blades with elastic coupl ing

The aeroelasticity of helicopter composite rotor blades with elastic coupling is analyzed. The st ructuralmodel in this analysis includes the effect s of t ransverse shear deformation , out-of-plane warping and aeroelastic coupling. A 21-DOF beam finite element , including t ransverse shear DOF and warping DOF , is developed for analysis.The governing differential equations of motion for a hingeless rotor are derived using the Hamiltonps principle.Three different composite blade configurations are conducted for comparison. The result s show that changes in bladef requencies are very small , however , the mode shapes are significantly changed considering elastic coupling. Theblade stability in hover is st rongly affected by the ply-induced composite couplings. Positive flap -torsion couplinghas a stabilizing effect on the lag mode damping. Negative flap-torsion coupling has a destabilizing effect on the lagstability.