For hingeless rotor system, the flap and lag hinges are removed and the flap and lag motions are realized through the elastic deformation of the flexures. Large amount of aerodynamic moments can be transmitted to rotor shaft because of the absence of hinges; accordingly aeroelastic instability problems of rotor system can occur. In order to increase aeroelastic stability, sufficient in-plane damping is required. In this study, composite tailoring technique has been applied to the flexures of a small-scaled hingeless rotor system. Composite flexures can have different coupling stiffness even though they have the same isotropic stiffness terms, and the aeroelastic characteristics can be greatly different. The effects of each coupling stiffness term on the aeroelastic stability have been investigated. Analysis results show that the in-plane damping can be changed remarkably when a torsion/flap bending coupling is changed. In addition, the application of viscoelastic damping material is considered to increase in-plane damping a little more.
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