Controlling density and modulus in auxetic foam fabrications—-implications for impact and indentation testing

DUNCAN, Oliver, ALLEN, Tom, FOSTER, Leon, GATT, Ruben, GRIMA, Joseph N. and ALDERSON, Andrew (2018). Controlling density and modulus in auxetic foam fabrications—-implications for impact and indentation testing. Proceedings, 2 (6), p. 250.

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Foams are commonly used for cushioning in protective sporting equipment. Volumetrically compressing open-cell polyurethane foam buckles cell ribs creating a re-entrant structure—set by heating then cooling—which can impart auxetic behaviour. Theoretically, auxetic materials improve impact protection by increasing indentation resistance and energy absorption, potentially reducing sporting injuries and burdens on individuals, health services and national economies. In previous work, auxetic foam exhibited ~3 to ~8 times lower peak force (compared to its conventional counterpart) under impacts adopted from tests used to certify protective sporting equipment. Increases to the foam’s density and changes to stress/strain relationships (from fabrication) mean Poisson’s ratio’s contribution to reduced peak forces under impact is unclear. This work presents a simple fabrication method for foam samples with comparable density and linear stress/strain relationship, but different Poisson’s ratios ranging between 0.1 and −0.3, an important step in assessing the Poisson’s ratio’s contribution to impact force attenuation.

Item Type: Article
Uncontrolled Keywords: Auxetic; Foam; Fabrication; safety; impact; protection
Research Institute, Centre or Group - Does NOT include content added after October 2018: Centre for Sports Engineering Research
Materials and Engineering Research Institute > Modelling Research Centre
Identification Number:
Page Range: p. 250
Depositing User: Jill Hazard
Date Deposited: 20 Mar 2018 12:55
Last Modified: 18 Mar 2021 02:18

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