Effect of Variability in Microgeometry of Polyurethane Foams on their Macroscopic Acoustic Performance

The numerical formulations used for the modeling and design of sound absorbing materials are constructed based on a set of physical parameters, known as the Biot's parameters (for isotropicmaterials these are comprised of 5 non-acoustical parameters and 4 mechanical parameters). These parameters are inter-correlated and are microstructure-dependent. There is in consequence a need for the development of links between the cellular structure of the foams and the Biot's parameters before realistically using these models for material-level optimization. In this sense, a microstructure-based model has been developed by Doutres et al. [J. Appl. Phys. 110, 064901 (2011)] to link the microstructure (thickness and length of struts and the closed windows content) of polyurethane (PU) foams to their non-acoustical parameters. In this study, this model is first extended to add the link between the microstructure and the mechanical properties of the foam. Next, a global sensitivity analysis using Fourier Amplitude Sensitivity Test (FAST) is performed to investigate the impact of the variability, associated with the irregularities in microstructure, on the sound absorption and transmission loss (TL) of the foam when combined with an elastic structure.