Single-crystal-material-based induced-shear actuation for vibration reduction of helicopterswith composite rotor system

Abstract

In this study, an assessment is made for the helicopter vibration reduction of compositerotor blades using an active twist control concept. Special focus is given to the feasibility ofimplementing the benefits of the shear actuation mechanism along with elastic couplings ofcomposite blades for achieving maximum vibration reduction. The governingequations of motion for composite rotor blades with surface bonded piezoceramicactuators are obtained using Hamilton’s principle. The equations are then solvedfor dynamic response using finite element discretization in the spatial and timedomains. A time domain unsteady aerodynamic theory with free wake modelis used to obtain the airloads. A newly developed single-crystal piezoceramicmaterial is introduced as an actuator material to exploit its superior shear actuationauthority. Seven rotor blades with different elastic couplings representing stiffnessproperties similar to stiff-in-plane rotor blades are used to investigate the hubvibration characteristics. The rotor blades are modeled as a box beam with actuatorlayers bonded on the outer surface of the top and bottom of the box section.Numerical results show that a notable vibration reduction can be achieved forall the combinations of composite rotor blades. This investigation also bringsout the effect of different elastic couplings on various vibration-reduction-relatedparameters which could be useful for the optimal design of composite helicopter blades.