Nonwoven textile structures – Commodity pathways to auxeticity*

Auxetic materials and structures possess a negative Poisson's ratio, which is inconsistent with intuition regarding a structure's response to deformation. Specifically, auxetic structures expand in tension and contract under compression, leading to sought after damping properties, impact resistance, and opportunities for constructing deployable structures. While this behavior may be achieved through intricate structural design, more common materials and structures can display this mechanical response, leading to a class of commodity auxetics. Our research has examined nonwoven fabrics and paper from this viewpoint and found that an out-of-plane auxetic response can be readily realized in fiber networks. By examining a variety of nonwoven structures, we have observed different mechanisms for the auxetic response and been able to affect the magnitude of the auxetic response by incorporating post-processing strategies. Overall, these results provide some of the needed general processing-structure-property relationships for producing auxetic fabrics as well as demonstrate pathways to producing these structures through conventional, large-scale methods.