The mechanical properties of conventional and auxetic foams. Part II: Shear

Auxetic materials with a negative Poisson's ratio have the fascinating property of expanding laterally when stretched longitudinally. This property is fundamentally important to the properties of a material, and significant changes in the value of the ratio have important effects on mechanical performance. This paper examines the variation in static and dynamic shear moduli on a range of auxetic foams and also examines variation in loss tangent. It is shown that both the static, elastic shear modulus and the dynamic loss tangent may increase with a negative Poisson's ratio. Such changes are attributed to modifications of the cell structure of the foam, not to changes in the material of the foam, during conversion to an auxetic foam. Such changes may have important applications in cushioning, packaging, sound absorption and protection.