THE INFLUENCE OF COMPOSITE INDUCED COUPLINGS ON TILTROTOR WHIRL FLUTTER STABILITY

The paper presents a study of the influence of composite induced elast ic couplings on the stability characteristics of a wing/rotor system. In particular, the study is focused on the effectiveness of the compos ite couplings that are introduced to the wing and the blade structures in modifying tiltrotor whirl flutter stability in forward flight (air plane mode). For that purpose, the study was first concentrated on the modelling and tailoring of the composite wing and blade structures. S ubsequently, by examining the equations of motion, the study has shown that a wing structure that features ''Chordwise Bending-Twist'' coupl ing may directly cancel the adverse aerodynamic effects and postpone i nstability while ''Beamwise Bending-Twist'' coupling has only indirect influence. Examination of coupled elastic blades revealed the involve d mechanisms within the rotor degrees of freedom that have the potenti al to increase the influence of highly damped degrees of freedom on th e system dynamics and subsequently postpone instabilities. It has been shown that depending on the blade pitch angle and its initial twist, both ''Chordwise Bending-Twist'' coupling and ''Beamwise Bending-Twist '' coupling within the blade structure are influential and may contrib ute to the system stability.