Wool nonwovens as candidates for commodity auxetic materials

Abstract

Abstract Advances in the field of auxetics have realized fabricated auxetic materials such as foams, fabrics, and fibers as well as a better theoretical understanding of the auxetic response. Because of their unique properties and applications, commodity auxetic materials are particularly desirable. Needle-punched nonwovens, several kinds of paper, and many knitted and woven fabrics have the potential to be auxetic, either as-produced or through a processing or design solution. In this study, we examine the out-of-plane Poisson’s ratio of as-produced and heat-compressed wool nonwovens. The wool nonwovens were found to be out-of-plane auxetic as-produced, and their auxetic character became more pronounced at higher treatment temperatures. Their behavior could be similar to that of paper, where straightening of a bent fiber was responsible for thickness increase. The prescribed processing conditions to enhance auxeticity could potentially be incorporated in their existing production, providing a pathway to generating commodity auxetics.