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.

It has come to our attention that figures 2(a) and 5(a) in our manuscript have errors in them. We have provided corrected versions of these figures and an explanation of the corrections in this corrigendum. These corrections do not change the conclusions of the paper. We would like to apologize for any inconvenience caused by these errors in the original manuscript.The units of the y-axis in figures 2(a) were given in 'cm'. However, the units should have been in 'mm'. The sample thicknesses are given with the correct units in table 1. Figures 2(b) and (c) are not changed.The image in figure 5(a) was not that of a wool nonwoven. Instead, it was of a stiff-felt polyester fabric that the authors were studying at the same time. Figure 5(a) has been replaced by a top-view of the as-received (AR) wool nonwoven. Figures 5(b)-(e) are not changed.

Auxetics are a class of mechanical metamaterials that show a negative Poisson’s ratio, which has been of interest as a mechanism to provide enhanced performance in, for example, composite materials...