Piezoactuation of sandwich plates with viscoelastic cores

Experimental and analytical validations of a Galerkin analysis of sandwich plates is 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 sandwiched plates that are 67.31 cm (26.5') long, 52.07 cm (20.5') wide and nominally 0.16 cm (1/16') 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 have been conducted on sandwich plates with aluminum face-plates under clamped boundary conditions to validate the model for isotropic face-plates. Symmetric and asymmetric sandwiches have been tested. The maximum error in damped natural frequency predictions obtained via the assumed modes solutions is less than 11%. Analytical studies on the influence of the number of assumed modes in the Galerkin approximation, and the temperature variation, have been conducted. Error in the first plate bending mode is 112% when only a single in-plane mode is used; error reduces to 3.95% as the number of in-plane modes is increased to 25 in each of the in-plane directions. The study on the temperature influence shows that every plate mode has a corresponding temperature, wherein the loss factor is maximized.