Which material model should be used in OptiStruct for EPS foam?

Hi all,

Expanded Polystyrene (EPS) is usually used as a package material. A quasi-static compression test was done to test its material behavior. In order to validate the material stress-strain curve from the compression test, a simulation should be done. The velocity of the compression test was about 5mm/min, so I think a static nonlinear analysis in optistruct may be proper. However, I don't know which material model is suitable for EPS foam material which has both hyperelastic and plastic behavior. Any suggestions?

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Roy