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Civil-Comp Proceedings
ISSN 1759-3433
CCP: 77
Edited by: B.H.V. Topping
Paper 74

Free Vibration of Metallic and Composite Beams Exhibiting Bending-Torsion Coupling

H. Su, C.W. Cheung and J.R. Banerjee

School of Engineering and Mathematical Sciences, City University, London, United Kingdom

Full Bibliographic Reference for this paper
H. Su, C.W. Cheung, J.R. Banerjee, "Free Vibration of Metallic and Composite Beams Exhibiting Bending-Torsion Coupling", in B.H.V. Topping, (Editor), "Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 74, 2003. doi:10.4203/ccp.77.74
Keywords: free vibration, metallic beam, composite beam, bending-torsion coupling.

Many investigators have studied the important effect of bending-torsion coupling on natural frequencies, mode shapes and response of metallic and composite beams [1,2,3,4,5,6,7,8,9,10,11,12]. However, all of these studies have been carried out independently, either for metallic, or for composite beams. The current investigation combines the studies of both metallic and composite beams using exact analytical approaches developed in References [1,2]. The main purpose of this paper is to compare the effect of two different types of coupling between bending and torsional deformations in beams made of metallic or composite constructions. In metallic beams, the mode coupling occurs as a result of non-coincident mass and shear centres. This coupling is inertial and is called geometric coupling. On the other hand, the coupling in composite beams arises as a result of stacking sequence and ply orientation and is called material coupling. Numerical results in this investigation are obtained using the methods described in References [1] and [2] for metallic and composite beams respectively. Two aircraft wings, namely the Goland wing [3] and the Loring wing [4] are used as examples for metallic beams, for which the effect of the geometric coupling is studied in details. These results are compared with published results [7] and excellent agreement was found. There are also two types of composite beams analysed in this paper, of which one is a flat beam with solid rectangular cross-section and the other is a thin-walled box beam. The former, namely the MIT beam, has been studied extensively in Reference [5] whereas the latter is referred to as the GIT beam [6]. As the names imply the work on these two beams was carried out by researchers at the Massachusetts Institute of Technology (MIT) and Georgia Institute of Technology (GIT) in the USA respectively. The effect of the material coupling on the free vibration characteristics is studied for both composite beams. Some of the results are compared with those obtained using the finite element method and experimental measurement [5]. Finally, numerical results for both metallic and composite beams are compared and discussed. One of the intriguing features of the current study is that the geometric and the material coupling can both cause modal interchanges between bending and torsional modes. The results presented in this paper highlight some of these interesting features which may have profound influence in aeroelastic studies.

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