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Communication Dans Un Congrès Année : 2020

Can membrane foams be viewed as high-tortuosity open-porosity foams?

Camille Gaulon
Juliette Pierre
Caroline Derec
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  • PersonId : 879310
  • IdRef : 183445058
François-Xavier Bécot
Fabien Chevillotte
  • Fonction : Auteur
Luc Jaouen

Résumé

When a foam solidifies, in some cases the thin membranes that separate the cells remain, leading to what we define as a ?membrane foam?. These foams have interesting acoustical properties, which differ notably from their open-porosity counterparts, i.e. samples in which the solid membranes are not present [1]. One of the most striking differences is the high values found for the real part of the effective density: typically 4 kg/m<sup>3</sup> for a membrane foam, compared to 1.5 kg/m<sup>3</sup> for usual open foams. Two approaches have been proposed to explain this high value of the effective density. One approach considers that the membranes are entrained by the sound wave, thus contributing to the total inertia of the effective medium. The other approach makes the hypothesis that the membranes remain static, the high effective density being explained by a high tortuosity [2]. This view relies on the observation that membrane foams are open-porosity materials. Indeed, during solidification the pressure in the cells of the foam must equilibrate with the external pressure, leading to the cracking or disappearance of some membranes. Thus the sound needs to travel through the complex tortuous network of small holes in the membranes, which explains the high value of the effective density. Both approaches have relevant arguments and have been successfully applied to some samples. In this talk we will present new experimental results and discuss how they can determine which vision is the correct one. [1] C. Gaulon et al, Appl. Phys. Lett. 2018 [2] V. H. Trinh et al, Materials & Design 2019

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hal-03235470 , version 1 (25-05-2021)

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Camille Gaulon, Juliette Pierre, Caroline Derec, François-Xavier Bécot, Fabien Chevillotte, et al.. Can membrane foams be viewed as high-tortuosity open-porosity foams?. Forum Acusticum, Dec 2020, Lyon, France. pp.3093-3093, ⟨10.48465/fa.2020.0648⟩. ⟨hal-03235470⟩
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