Twist morphing of a hingeless rotor blade using a moving mass

Abstract

This paper presents a new concept of morphing by changing the twist of a composite blade through the movement of a mass near the tip of the blade. The mass is moved in the chordwise direction which then modifies the centrifugal force near the tip of the blade. The blade is tailored with composite materials and hence coupling is introduced. By moving the mass in the chordwise direction, a variable bending moment is produced which is the result of the offset between the point mass centrifugal force and the shear centre of the blade section. This bending moment will be transferred to the composite spar, and then through the bend-twist coupling of the composite layup, a variable torsional moment will be induced. This variable torsional moment changes the twist distribution of the blade. The dynamics of the rotating composite blade is modelled by using the geometrically exact fully intrinsic beam equations and the point mass is considered as a non-structural concentrated mass which has offsets with respect to the beam reference line. It is found that by moving the mass in the chordwise direction, the twist distribution of the blade changes. The rate of twist change completely depends on the bend-twist coupling and also the point mass magnitude and location. Finally, the effect of sensitive morphing parameters on the rotating frequencies of the Bo105 main rotor blade is determined.