The University of Southampton
University of Southampton Institutional Repository
Warning ePrints Soton is experiencing an issue with some file downloads not being available. We are working hard to fix this. Please bear with us.

A practical procedure for measuring the stiffness of foam like materials

A practical procedure for measuring the stiffness of foam like materials
A practical procedure for measuring the stiffness of foam like materials
Polymer foams are used extensively in everyday life, from disposable packaging and soft furnishings through to engineering applications such as core structural materials in the marine industry or bone analogue materials for orthopaedic device testing. In the engineering field it is important that the mechanical behaviour of these materials is characterised correctly, as computationally based predictions of structural performance rely heavily on accurate input data. Mechanical property data from standard physical tests such as uniaxial compression are subject to artefacts including non-uniformity of applied loading, test fixture-sample contact conditions, and test machine compliance. These are well-documented problems, which techniques such as extensometry and point tracking of marker pairs attempt to resolve. In particular, in addition to being non-contact, the use of individual marker pairs can reveal non-linear behaviours because of alignment issues. In the current work, a practical, accurate experimental methodology is introduced to investigate this issue. Uniaxial compression tests were conducted on cellular polyurethane foam blocks. Both faces of the foam specimens were monitored using point tracking on multiple marker pairs to account for misalignment. Sample deformation was simultaneously measured by test-machine crosshead displacement. The Young’s modulus and Poisson’s ratio were calculated in both cases. To verify the measurements, digital volume correlation (DVC) was applied. DVC is a full-field non-contact strain measurement method that interrogates the interior structure of the foam to determine the physical response. Results demonstrated that misalignment effects could easily be followed during testing, which averaged out on both front and back surfaces to produce a single modulus value. Considerable differences were evident between crosshead displacement calculated modulus and point tracking, indicating that artefacts can lead to substantial errors, as evidenced in the published literature.
polyurethane foam, analogue bone, test artefacts, DVC , digital volume correlation, point tracking, optical extensometry
0732-8818
439-452
Marter, Alexander
10963c2a-2941-40fb-aecf-ecf28be14d28
Dickinson, Alexander
10151972-c1b5-4f7d-bc12-6482b5870cad
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397
Marter, Alexander
10963c2a-2941-40fb-aecf-ecf28be14d28
Dickinson, Alexander
10151972-c1b5-4f7d-bc12-6482b5870cad
Pierron, Fabrice
a1fb4a70-6f34-4625-bc23-fcb6996b79b4
Browne, Martin
6578cc37-7bd6-43b9-ae5c-77ccb7726397

Marter, Alexander, Dickinson, Alexander, Pierron, Fabrice and Browne, Martin (2018) A practical procedure for measuring the stiffness of foam like materials. Experimental Techniques, 42 (4), 439-452. (doi:10.1007/s40799-018-0247-0).

Record type: Article

Abstract

Polymer foams are used extensively in everyday life, from disposable packaging and soft furnishings through to engineering applications such as core structural materials in the marine industry or bone analogue materials for orthopaedic device testing. In the engineering field it is important that the mechanical behaviour of these materials is characterised correctly, as computationally based predictions of structural performance rely heavily on accurate input data. Mechanical property data from standard physical tests such as uniaxial compression are subject to artefacts including non-uniformity of applied loading, test fixture-sample contact conditions, and test machine compliance. These are well-documented problems, which techniques such as extensometry and point tracking of marker pairs attempt to resolve. In particular, in addition to being non-contact, the use of individual marker pairs can reveal non-linear behaviours because of alignment issues. In the current work, a practical, accurate experimental methodology is introduced to investigate this issue. Uniaxial compression tests were conducted on cellular polyurethane foam blocks. Both faces of the foam specimens were monitored using point tracking on multiple marker pairs to account for misalignment. Sample deformation was simultaneously measured by test-machine crosshead displacement. The Young’s modulus and Poisson’s ratio were calculated in both cases. To verify the measurements, digital volume correlation (DVC) was applied. DVC is a full-field non-contact strain measurement method that interrogates the interior structure of the foam to determine the physical response. Results demonstrated that misalignment effects could easily be followed during testing, which averaged out on both front and back surfaces to produce a single modulus value. Considerable differences were evident between crosshead displacement calculated modulus and point tracking, indicating that artefacts can lead to substantial errors, as evidenced in the published literature.

Text
Post Print - Accepted Manuscript
Download (1MB)
Text
Marter_et_al-2018-Experimental_Techniques - Version of Record
Available under License Creative Commons Attribution.
Download (2MB)

More information

Accepted/In Press date: 28 March 2018
e-pub ahead of print date: 24 May 2018
Published date: August 2018
Keywords: polyurethane foam, analogue bone, test artefacts, DVC , digital volume correlation, point tracking, optical extensometry

Identifiers

Local EPrints ID: 418322
URI: http://eprints.soton.ac.uk/id/eprint/418322
ISSN: 0732-8818
PURE UUID: 6365b7ad-863c-4dc9-a307-80757de5727c
ORCID for Alexander Dickinson: ORCID iD orcid.org/0000-0002-9647-1944
ORCID for Fabrice Pierron: ORCID iD orcid.org/0000-0003-2813-4994
ORCID for Martin Browne: ORCID iD orcid.org/0000-0001-5184-050X

Catalogue record

Date deposited: 28 Feb 2018 17:30
Last modified: 26 Nov 2021 06:25

Export record

Altmetrics

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×