Vibration reduction in rotor blades using active composite box beam

The vibratory load reduction at a rotor hub using smart materials and closed-loop control is investigated. The principal load-carrying member in the blade is represented by a composite box beam, of arbitrary thickness, with surface bonded self-sensing actuators. A comprehensive theory is used to model the smart box beam. The theory, which is based on a refined displacement field, is a three-dimensional model that approximates the elasticity solution so that the beam cross-sectional properties are not reduced to one-dimensional beam parameters. Both in-plane and out-of-plane warpings are included automatically in the formulation. Next, an integrated rotor vibratory load analysis procedure is developed by coupling an unsteady aerodynamic model with the rotor blade dynamic model based on the smart composite box beam theory. The dynamic deformations of the blade in all three directions, flap, lead lag, and torsion, are included in the analysis. The finite-state, induced-flow model is used for predicting the dynamic loads. The procedure results in significant reductions in the amplitudes for rotor dynamic loads with closed-loop control. Detailed parametric studies are presented to assess the influence of number of actuators and their locations in vibratory hub load reduction.