FG and viscoelastic models combination for vibroacoustic modeling of sandwich structures made of open and closed cell foam materials

Abstract

This paper presents a new method based on a functionally graded viscoelastic model for examining the acoustic vibrations of a submerged sandwich shell in the fluid. The structure consists of two isotropic shells that the space between them is filled with open-cell and closed-cell foams. A laminate model is used to get the equations of motion of the foam core. It is assumed that the core is composed of an infinite number of viscoelastic layers, while the properties of the adjacent layers are different. Consequently, complex Young’s and shear moduli are dependent on the frequency of excitation. Density and Young modulus vary according to a distribution function through the thickness. Because of the effective roles of rotary inertia and shear deformation, the governing equations of the sandwich structure are obtained by the three-dimensional theory of elasticity. The Zener model is used for describing the viscoelastic behavior of foam. Next, the solution procedure of the vibroacoustic behavior is derived by the transfer matrix method. Finally, the effects of mechanical parameters of foam such as relative density, edge material fraction, relaxation time, volume fraction, and power index are examined. The results exhibit that open-cell foam is better sound insulation than closed-cell foam.