Analytic extraction of the elastic coupling mechanisms in composite blades

An aeroelastic model for a hingeless helicopter blade with a composite flex -beam is presented. The model employs structural analysis for laminated fle x-beams of solid cross-sections with symmetric layup, and the study encompa sses configurations with Beamwise Bending-Twist coupling and Chordwise Bend ing-Twist coupling. The structural dynamics of blades with coupled composit e flex-beams is studied by a special purpose methodology that allows the cr eation of a refined uncoupled reference blade for each case. This procedure enables the determination of the net effects which are induced by the elas tic couplings. By examining the stability characteristics of the blades in the frequency domain and their response in the time domain, the paper suppl ies additional information regarding the trade-off between stability and vi bration characteristics in both the transient and the steady-state, forward -flight regimes. The analysis also examines the effect of different types o f composite materials and quantitatively identifies the relation between el astic properties and their potential to improve blade stability margins. (C ) 2000 Elsevier Science Ltd. All rights reserved.