Strain rate dependence of stiffness and Poisson's ratio of auxetic open cell PU foams

The paper describes the manufacturing and tensile testing of auxetic (negative Poisson's ratio) thermoplastic polyurethane and polyester urethane foams, under quasi-static and constant strain rate loading. The foams are produced from conventional flexible polyurethane basis following a manufacturing route developed in previous works. The Poisson's ratio behaviour over compressive strain has been analyzed using an Image Data processing technique based on Edge Detection from digital images recorded using camcorders and high speed cameras. The measurements indicate that higher strain rate loading implies stiffening effects on the stress-strain curves, and significant increase of the magnitudes of the Poisson's ratios with increasing compressive strains.