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A general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materials-with application to a melamine foam
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Marcus Wallenberg Laboratory MWL. KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Numerical acoustics.ORCID iD: 0000-0003-1855-5437
2014 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 115, no 8, 084904- p.Article in journal (Refereed) Published
Abstract [en]

This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.

Place, publisher, year, edition, pages
2014. Vol. 115, no 8, 084904- p.
Keyword [en]
Anisotropy, Energy dissipation, Estimation, Porous materials, Stiffness matrix
National Category
Textile, Rubber and Polymeric Materials Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:kth:diva-137747DOI: 10.1063/1.4865789ISI: 000332619600090Scopus ID: 2-s2.0-84896794683OAI: oai:DiVA.org:kth-137747DiVA: diva2:679686
Funder
EU, European Research Council, MRTN-CT-2006-035559
Note

QC 20140508. Updated from submitted to published

Available from: 2013-12-16 Created: 2013-12-16 Last updated: 2017-12-06Bibliographically approved
In thesis
1. Vibro-acoustic modelling of anisotropic poroelastic materials: characterisation of the anisotropic properties
Open this publication in new window or tab >>Vibro-acoustic modelling of anisotropic poroelastic materials: characterisation of the anisotropic properties
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The present-day challenges in the transport industry, steered by the increasing environmental awareness, necessitate manufacturers to take measures to reduce emissions related to the movements of goods and humans. In particular, the measures aiming at a reduced mass or higher load capacity to increase fuel efficiency,  generally deteriorate the noise and vibration insulation properties of their products. In order to comply with the regulations and customer demands, modern vehicles increasingly move towards a multifunctional integrated design approach, if possible for all subcomponents involved. Such a multifunctional design approach is an iterative process, evaluating the proposed solutions in every stage, and is therefore best performed in a virtual testing environment. \\Poroelastic materials are interesting to include in a multifunctional design, offering reasonably good vibro-acoustic insulation properties at a low weight penalty. These materials can also be combined in multilayer arrangements to further enhance the overall performance. \\In order to achieve an accurate modelling of the vibro-acoustic behaviour of poroelastic materials, the input data describing the material properties should be of a high quality. Two characteristics inherent to these materials encumber a precise characterisation with traditional techniques. Poro-elastic aggregates are anelastic due to the constituent material used, and anisotropic as a consequence of the production process. Characterisation techniques allowing for an accurate determination of the material properties need to take these intrinsic characteristics into account.\\The objective in this thesis is to enable the characterisation of a constitutive material model for poroelastic materials which is as general as possible, and includes the inherent material anelasticity and anisotropy. For this purpose, a set of advanced characterisation techniques has been developed to characterise the anisotropic flow resistivity tensor and the anisotropic dynamic Hooke's tensor. \\These advanced characterisation techniques are based on an inverse estimation procedure, used consistently throughout the work, and includes both experiments and numerical predictions. The property to characterise is isolated in a specially designed set-up such that it can be modelled by physics solely involving this property. The obtained experimental and numerical data then serve as the input to an optimisation, which returns the material properties for which the difference between both is as small as possible. These methods have been successfully applied to melamine foam, which is found to be both anisotropic and anelastic, confirming the need for such advanced characterisation techniques.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2014. xiv, 58 p.
Series
Trita-AVE, ISSN 1651-7660 ; 2013:67
National Category
Fluid Mechanics and Acoustics Textile, Rubber and Polymeric Materials
Identifiers
urn:nbn:se:kth:diva-137809 (URN)978-91-7501-983-3 (ISBN)
Public defence
2014-01-20, sal F3, KTH, Lindstedtsvägen 26, Stockholm, 13:15 (English)
Opponent
Supervisors
Funder
EU, European Research Council, MRTN-CT-2006-035559
Note

QC 20131219

Available from: 2013-12-19 Created: 2013-12-16 Last updated: 2013-12-19Bibliographically approved

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Göransson, Peter

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