MicroCT Scan of Auxetic Foam

Notable Features of Model

• Based on in vitro scan
• Image to model in less than 20 minutes
• Contact surface automatically generated on structure
• Coupled fluid-structure mesh
• Analysis caried out in Abaqus, Fluent and LS-Dyna

What is Auxetic Foam?

The term "auxetic" derives from the Greek auxeos to mean "that can expand". Auxetic materials have a negative Poisson's ratio, which means in contrast to most materials, they expand in all directions when stretched.

MicroCT (Synchrotron) Scan

High-resolution 3D scan data of auxetic foam was obtained from synchrotron facilities in Chicago (courtesy Prof Gerry Seidler, University of Washington).

CT scan data

Segmented foam in ScanIP

FE mesh in +ScanFE (more detailed image)

Mesh Generation in ScanIP and ⁺ScanFE

The data was straightforwardly segmented using threshold and FloodFill tools, and a 3D smooth volumetric mesh was generated within ⁺ScanFE. A contact surface was created on the surface of the foam to simulate compression in the compaction regime. The total combined image processing and meshing time, including user interaction time, was less than 20 minutes.

Analysis in Abaqus, Fluent and LS-Dyna

The mesh imported into Abaqus where a top pressure load was applied to explore the structural mechanisms leading to the unusual Poisson's ratio value measured experimentally. In LS-Dyna, a contact surface was created on the surface of the foam to simulate compression in the compaction regime.

Abaqus		Fluent		LS-Dyna
Deformation compression View animation AVI (4.6 Mb)		Flow analysis		Stress plot View animation MPG (10 Mb)
Large deformation     compression   High element qualities   Dual convergence		Flow through dual of     mesh   Fluid-structure     interaction		Explicit analysis   High volumetric     compression   Non-linear material     properties of parent     material

Need a player or codec to play the animations?
Download Windows MediaPlayer, Media Player Classic, XViD codec.

Special thanks to First Numerics (Dr Georges Limbert), the University of Exeter (Dr Gavin Tabor), and ARUP (Brian Walker), who provided us with their FEA and CFD studies.

Publications

Walker, B., Young, P., 2007. Image Based Meshing for LS-DYNA. In: 6th European LS-Dyna users' conference, 28-29 May 2007 Gothenburg. Linköping: Engineering Research Nordic AB, 3.53-3.67.

Limbert, G., 2006. Computer simulation: A powerful tool for developing new materials for biomedical applications. MED Matters - IMechE Medical Engineering Division E-Newsletter, January 2006 - Issue 02.