Manufacture and characterisation of thin flat and curved auxetic foam sheets

A new method for the production of thin flat and curved auxetic foam sheets by uniaxial compression is reportted in this paper. Detailed optical microscopy and Poisson's ratio measurement by videoextensometry has revealed that the auxetic behaviour is due to a crumpling of the pores through the foam thickness, caused by a uniaxial compression of 4060% in combination with shear for the curved foams. Poisson's ratio values of up to -3 have been recorded for the curved foams and -0.3 for the flat sheets.