The Mechanical Properties of Conventional and Auxetic Foams. Part I: Compression and Tension

Abstract

Auxetic foams exhibit the unusual property of a negative Poisson's ratio and hence expand laterally when stretched. In this, the first of two papers, a systematic study is made of the mechanical properties of a range of foams fabricated to have different negative Poisson's ratios. The stress-strain behaviour, in both tension and compression, is compared with conventional foams. Values for the Young's moduli and Poisson's ratios in the three principal directions, in both tension and compression, are obtained. Negative Poisson's ratios ranging between -0.2 and -0.9 in tension, and between -0.1 and -0.8 in compression have been obtained. The effect of densification, during loading is significantly enhanced in auxetic foams, and this significantly affects the stress-strain curves. The creep resistance of the foams is also examined.