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Micro-Macro Acoustic Modeling of Heterogeneous Foams with Nucleation Perturbation
ISSN: 0148-7191, e-ISSN: 2688-3627
To be published on June 3, 2020 by SAE International in United States
Event: 11th International Styrian Noise, Vibration & Harshness Congress: The European Automotive Noise Conference
The properties of a polyurethane foam are greatly influenced by the addition of graphite particles during the manufacturing process, initially used as a fire retardant. These thin solid particles perturbate the nucleation process by generating bubbles in its immediate vicinity. The preponderance of work so far has focused on foams that are locally relatively homogeneous. We propose a model for locally inhomogeneous foams (including membrane effects) consisting of a random stack of spheres that permits one to represent certain pore size distribution functions. The cellular structure of the foam is obtained through a Laguerre tessellation and the solid skeleton determined from the minimization of surface energy (Surface Evolver). The structure of real foam samples is analyzed using X-ray computed tomography and scanning electron microscopy followed by image processing to create computerized three-dimensional models of the samples. The corresponding effective material parameters, including the permeability, the tortuosity and the viscous characteristic length are computed by applying a numerical homogenization approach. All the numerical data are presented, discussed and further compared with experimental results.