Active Twist of the Composite Rotor Blade Using Macro Fiber Composite Actuators

The aim of this work is the development of an active twist actuation concept for reduction of vibration and blade-vortex interaction (BVI) noise of helicopter to improve the overall performances of helicopters. Active twist control of the rotor blades may be used to refuse the aerodynamic disturbances affecting the blades and in real time enables the implementation of active vibration control strategies. The twist deformation of blade is obtained using Macro Fiber Composite actuators (MFC) embedded in the composite blade construction. Two active plies of MFC actuators is situated at the top and bottoms of helicopter rotor blades and oriented at ±450 to the spanwise axis of the rotor blade. Electric field activates the piezoelectric effect in the piezoceramic fibers of MFC actuators, which elongate along the length of fibers and thus distribute a twisting movement along the blade. The methodology based on the planning of experiments and response surface technique has been developed for the various geometric parameters of blade and optimum placements of Macro Fiber Composite (MFC) actuators to achieve a maximal angle of twist. The optimisation problem has been formulated on the results of parametric study and taking into account the producers requirements. The finite element model of rotor blade was built using ANSYS finite element program. It was comprised of two different types of elements: linear layered structural shell elements SHELL 99 and structural solid elements SOLID 186, which was used to model the different components of blade. The design of this finite element model is based on the dimensions of the full-scale BO-105 helicopter rotor blade. An investigated helicopter rotor blade is equipped with NACA23012 airfoil and has a rectangular shape. The helicopter rotor blade consists of C-spar made of unidirectional glass-fiber reinforced plastic (UD GFRP), skin made of ±450 GFRP, foam core, balance weight and MFC actuators. For a static analysis the thermal strain analogy between piezoelectric strains and thermal strains is used to model piezoelectric effects, when piezoelectric coefficients characterizing an actuator are introduced as thermal expansion coefficients