Effect of material coupling on wave vibration of composite Euler-Bernoulli beam structures

Fiber-reinforced composite materials are an important development in the continuing search for lightweight materials for great strength and stiffness. Lighter structures are usually more prone to vibrations. Furthermore, due to material coupling, composite beams normally vibrate with coupled vibration modes, which complicates vibration analysis. This paper presents the effect of coupling between bending and torsional deformations on vibrations of composite Euler-Bernoulli beams from a wave vibration standpoint. In the study, it is found that the torsional mode is only unaffected by the material coupling at low frequencies. The flexural modes are found affected over the entire frequency band. Unlike their uncoupled metallic counterparts, the wavenumbers for propagating and decaying wave components are no longer the same due to material coupling. Free vibration analysis is performed from a wave standpoint. Free vibration of composite beam with the coupling effect taken into account is of great importance. This is because the free vibration characteristics can be designed favorably by suitable choice of ply orientations and stacking sequence-one of the unique features of composite structures. Numerical examples for which comparative results are available in the literature are presented.