Topological characteristics and mechanical properties of uniaxially thermoformed auxetic foam

Qicheng Zhang, Wenjiang Lu, Fabrizio Scarpa*, David A W Barton, Kathryn Rankin, Yunpeng Zhu, Ziqiang Lang, Hua-Xin Peng

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

21 Citations (Scopus)
7 Downloads (Pure)


We present here a simplified procedure to manufacture auxetic PU foam via a single direction thermoforming compression process applied to conventional (pristine) open cell foam samples. The auxetic foams produced here have a Poisson’s ratio ν_21 ranging from -1 to 0 in the 1-2 plane and a tangent modulus Et2 ranging from 0.2MPa to 2MPa. X-ray μ-CT and 3D skeletonization enabled extraction of the topological parameters of pristine and auxetic foams. The auxetic foam is transverse isotropic with cell structures exhibiting a re-entrant shape along the thermoform compression direction 1. More ribs are also oriented within the transverse plane 2-3, in which the stiffness is larger. Tensile and compression quasi-static tests have been carried out on samples cut along different directions and having various thermoform compression ratios rc. Auxeticity is present in the in 1-2 plane only for compression ratios between 40% to 80%. Finite Element models for the pristine and auxetic foams have been also built from the μ-CT scanned 3D models. The numerical results show good agreement with the experimental data and help explaining the deformation mechanisms of these auxetic foams.
Original languageEnglish
Article number110139
Number of pages29
JournalMaterials and Design
Early online date1 Oct 2021
Publication statusPublished - 1 Dec 2021

Structured keywords

  • Engineering Mathematics Research Group


  • Auxetic foam
  • negative Poisson’s ratio
  • modulus
  • loss factor
  • X-ray CT


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