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Optimisation of composite beam behaviour has led to the use of composite materials where one of the constituent orthotropic axes is no longer orthogonal to the cross-section, in order to obtain specific coupling characteristics which enhance the overall performance of the structure. Therefore, theories which were previously valid for traditional beams (where the longitudinal axis is parallel to an orthotropic axis) are no longer applicable. The purpose of this paper is to provide a simple analytical method for calculating stresses and strains existing in thin-walled composite beams formed of orthotropic materials, one of whose orthotropic axes is not necessarily orthogonal to the cross-section. The advantage of such a method is that it does not rely on a cumbersome numerical calculation like, for example, a finite element method. The box beam to be studied is formed of different parts, so that, by using a homogenisation method, each part can be considered as an equivalent homogeneous material. The use of the original hypothesis, together with global equilibrium equations, have enabled us to obtain a set of easy-to-solve linear equations. The solution gives forces and strains in the cross-section. Using this knowledge, stress can be determined in each layer. The suggested method has been validated by comparison with results calculated by a finite element software called MEF-MOSAIC. |
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