Modelling and dynamic stability of a hingeless active fibre composite blade

Abstract

The main focus of this investigation was to investigate dynamic stability of what is now commonly referred to as an active twist rotor blade. With the ultimate intention of controlling helicopter blade vibrations, active or smart materials embedded in the rotor blade in various arrangements as opposed to the conventional passive isolation devices and absorbers are used. Structurally integrated interdigitated piezoelectric fibre composite material is considered in this work. This active composite may be used in constructing the blade in place of or concurrent with, composite blades. This fibrous composite is able to twist the blade, when subjected to an electric field, due to its unique arrangement of active fibres. The paper begins with outlining the design for lay-up sequence of the active blade. This is followed by developing a complete structural and dynamic modelling of the equations of motion of the smart blades for hover flight. These equations are used to investigate dynamic stability of the steady state motion of the smart blades under parametric excitation. In closing, as a preliminary step to determine the actuation authority of the active fibres, the open-loop response of the blade to an impulsive type of actuation is also investigated.