Amir Hamza
The Journal of Mechanical Science and Technology, vol. 23, no. 2, pp.283-290, 2009

Abstract : Polyurethane (PU) and other plastic foams are widely used as passive acoustic absorbers. For optimal design, it is often necessary to know the viscoelastic properties of these materials in the frequency range relevant to their application. An experimental/numerical technique has been implemented to determine the Young and shear dynamic moduli and loss factor of poroelastic materials under low-frequency 40-520Hz random excitation. The method consists of measuring the dynamic response of the sample at its surface, and matching the response with the predictions from a finite element model in which the two complex elastic moduli are the adjustable parameters. Results are presented for measurements made in air, under standard pressure and temperature conditions, and compared with predictions based on Okuno’s model. The dependence of elastic moduli on the dimension of the sample and its boundary conditions is also studied.

Keyword : Young’s modulus; Shear modulus; Loss factor; Finite element method