22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-4.7.3

FLUTTER ANALYSIS OF COMPOSITE WINGS USING SYMBOLIC COMPUTATION

J. R. Banerjee (1), R. Butler (2)
(1) City University, UK; (2) University of Bath, UK

Keywords: aeroelasticity, composite wings, flutter, symbolic computation

Symbolic computation is used to investigate the flutter behaviour of uniform composite wings analytically instead of numerically. As a result the proposed method requires minimum computational effort because all numerical matrix manipulations associated with the solution of flutter problems are completely avoided. The wing is idealised as a bendingtorsion (materially) coupled composite beam with cantilever end condition for which the frequency equation and mode shapes in free natural vibration are presented in closed analytical form. For a given number of selected normal modes, the expressions for generalised mass, generalised stiffness and generalised aerodynamic force are derived in explicit analytical form. This was assisted greatly by symbolic computation. Finally the flutter problem is formulated by summing algebraically the expressions for generalised mass, generalised stiffness and generalised aerodynamic force terms. From the final expression containing all the above terms the flutter speed and flutter frequency are determined by using a standard root finding procedure. As a consequence, the proposed analytical method is found to be accurate and efficient, and therefore, it holds out the prospect of precise aeroelastic optimisation. An illustrative example confirming the correctness and accuracy of the method when predicting the flutter speed and flutter frequency of a laminated composite wing is provided.

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