| The composite has been widely used in many engineering applications because of their desirable mechanical properties, such as high ratio of stiffness, strength to weight, light-weight and the reliable design of these structural behavior. For example, thin-walled beams with closed cross-sections made up of composite materials, have been widely used in modern helicopter rotor blade and larger wind turbine blade. A good knowledge of their coupled static and dynamic characteristics are of fundamental importance in the rational design of thin-walled structures.Above all, the coupled deformation behavior of the thin-walled laminated composite beams is investigated. The constitutive relationship of the composite thin-walled box structure is derived using an asymptotic variational method. The general form of constitutive relation was applied to the cases of extension-twist coupling, corresponding to Circumferentially Uniform(CUS) and bending-twist coupling, corresponding to Circumferentially Anti-Symmetric(CAS). The coupled static deformations of composite thin-walled closed-section beams of various circular, elliptical and single (double)-cell box sections are obtained by numerical calculations. Secondly, on the basis of the closed form solution of natural frequencies, the influence of the elastic coupling mechanisms on the free vibration behavior of the above-mentioned thin-walled composite beams is investigated numerically.The assumed mode method is combined with the Lagrange's equation to derive the mathematical model that describes the coupled extension-twist forced vibration of composite thin-walled closed-section cantilever beams. The time-domain response curves of the beam tip are obtained and the steady forced vibration responses of single-cell and two-cell box beams are compared.Finally, using ANSYS of the finite element analysis software, the predictions of coupled static deformations and natural frequencies of composite thin-walled box beams are validated. |
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