Microstructure based model for sound absorption predictions of perforated closed-cell metallic foams

Abstract : Closed-cell metallic foams are known for their rigidity, their lightness, their thermal conductivity as well as their low production cost compared to open-cell metallic foams. Yet, they are also poor sound absorbers. A method to enhance their sound absorption is to perforate them. This method has shown good preliminary results but has not yet been analyzed from a microstructural point of view. The objective of this work is to better understand how perforations modify the sound absorption of closed-cell metallic foams. First, a simple two-dimensional (2D) microstructural model of the perforated closed-cell metallic foam is proposed and solved through numerical homogenization. A rough three-dimensional (3D) correction of the 2D results is then given from the standpoint of straightforward examination of the analytical slits/cylinders macroscopic parameters. The results show that the diameter of both the perforation and the pore appear as the main controlling parameters of the sound absorption behavior. An experimental comparison demonstrates that the 2D proposed microstructural numerical model combined with a 3D analytical correction factor yields realistic trends for optimization purposes. Some design guides are also proposed.