Sandwich structures consisting two thin faces and a thick core are increasing in demand, corresponding to the challenge to minimize weight and improve load carrying. In order to describe the free vibration of these kinds of structures, several accurate models have been proposed; however, the damping effect of ambient air, influential for lightweight structures, is always neglected. This paper originally presents a finite element formulation to study free vibration of a sandwich beam coupling with ambient air. The sandwich beam was modeled based on the sandwich theory, where the shear deformation of the sandwich core was taken into account. The thickness of the sandwich beam was included into the mesh model. The accuracy of the formulation was verified by comparing the obtained results with other analytical solutions and experimental results. The parametric studies on the effect of shear deformation and ambient air were conducted and the results indicate the necessity of taking into account these effects.
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