PhD: metaporoelastic surfaces for the joint mitigation of the acoustic and elastic energies (LAUM, Le Mans, France)

Application deadline: Thu 30 Jun 2022

Location: The Acoustics Laboratory of Le Mans University, UMR CNRS 6613, Av. Olivier Messiaen, 72085 Le Mans Cedex 09
Supervision: Jean-Philippe Groby (CR CNRS-HDR), Vicente Romero-García (CR CNRS), and Olivier Dazel (PR, Univ. du Mans).
Required skills: Master in wave physics or acoustics - analytical, numerical and experimental developments.

Poroelastic materials are used for the joint mitigation of elastic and acoustic energies. Therefore, they are usually packaged in sheets whose thickness remains important in view of the increasing demands, especially for low frequency efficiency. The periodic inclusion of resonators in these plates allows to increase the modal density at low frequencies. This greatly improves the low frequency acoustic performance of the designed metaporous surfaces and interfaces [1,2,3]. These structures are now optimized and faithfully fabricated by rapid machining [4]. Accounting for the motion of the poroelastic plate skeleton allows the use of elastic resonant inclusions which are by definition lower frequencies than the acoustic ones. The aim of this thesis is to analyze the mechanisms of acoustic and elastic energy dissipation in these metaporoelastic structures [5,6]. Achieving perfect absorption of acoustic and elastic energies ‘roughly' requires impedance matching for acoustic and elastic waves and the exact compensation of radiation losses by viscoelastic (elastic waves) and viscothermal (acoustic waves) losses [7,8]. The structures must therefore be tunable, for example multi, or failing that, bi-stable structures.
To achieve this, a bottom-up approach combining homogenization, modal analysis, and
additive manufacturing method will be developed.

[1] J.-P. Groby, A. Wirgin, and E. Ogam, Acoustic response of a periodic distribution of macroscopic inclusions within a rigid frame porous plate, Wave Random Complex, 18: 409-433, 2008.
[2] C. Lagarrigue, J.-P. Groby, V. Tournat, O. Dazel, et O. Umnova, Absorption of sound by porous layers with embedded periodic array of resonant inclusions, J. Acoust. Soc. Am., special issue POROUS MATERIAL, 134: 4670-4680, 2013.
[3] J.-P. Groby, B. Nennig, C. Lagarrigue, B. Brouard, O. Dazel, et V. Tournat, Enhancing the absorption properties of acoustic porous plates by periodically embedding Helmholtz resonators, J. Acoust. Soc. Am., 137: 273-280, 2015.
[4] T. Cavalieri, J. Boulvert, V. Romero-García, G. Gabard, M. Escouflaire, J. Regnard, and J.-P. Groby, Rapid manufacturing of optimised anisotropic metaporous surfaces for broadband absorption, J. Apppl. Phys., special issue Acoustic Metamaterials, 129: 115102, 2021.
[5] T. Weisser, J.-P. Groby, O. Dazel, F. Gaultier, E. Decker, S. Futatsugi, and L. Monteiro, Acoustic behavior of a rigidly backed poroelastic layer with periodic resonant inclusions by a multiple scattering approach, J. Acoust. Soc. Am., 139:617–629, 2016.
[6] M. Gaborit, L. Schwan, O. Dazel, J.-P. Groby, T. Weisser, and P. Göransson, Coupling FEM, Bloch Waves and TMM in meta-poroelastic laminates, Acta Acust. united Ac., special issue Modeling of structured materials for sound and vibration, 104: 220-227, 2018.
[7] V Romero-García, G Theocharis, O Richoux, V Pagneux. Use of complex frequency plane to design broadband and sub-wavelength absorbers, J. Acoust. Soc. Am., 139: 3395-3403, 2016.

[8] V. Romero-García, N. Jiménez, J.-P. Groby, A. Merkel, V. Tournat, G. Theocharis, O. Richoux, V. Pagneux. Perfect absorption in mirror symmetric metascreens. Phys. Rev. Applied 14: 054055,