Analysis of Sandwich Plates with Isotropic Face Plates and a Viscoelastic Core

Experimental and analytical validations of a Galerkin assumed modes analysis of sandwich plates are presented in this paper. The 3-layered sandwich plate specimen consists of isotropic face-plates with surface bonded piezo-electric patch actuators, and a viscoelastic core. The experimental validation is conducted by testing sandwich plates that are 67.31 cm (26.5 in.) long, 52.07 cm (20.5 in.) wide and nominally 0.16 cm (1/16 in.) thick. The analysis includes the membrane and transverse energies in the face plates, and shear energies in the core. The shear modulus of the dissipative core is assumed to be complex and variant with frequency and temperature. The Golla-Hughes-McTavish (GHM) method is used to account for the frequency dependent properties of the viscoelastic core. Experiments were conducted on symmetric and asymmetric sandwich plates with aluminum face-plates under clamped boundary conditions to validate the model for isotropic face-plates. The maximum error in damped natural frequency predictions obtained via the assumed modes solution is <11 percent. Analytical studies on the influence of the number of assumed modes in the Galerkin approximation have been conducted. Error in the first plate bending mode is 112 percent when only a single in-plane mode is used; error reduces to 3.95 percent as the number of in-plane modes is increased to 25 in each of the in-plane directions.

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