Auxetic materials and structures display an unusual behavior when deformed. Specifically, they expand when subjected to tensile deformation, whereas most materials would show the opposite response. This behavior has been observed in a variety of materials and structures, and the structural feature responsible for this behavior can be present at the molecular level or at a larger macroscale level. While this behavior may be purposefully engineered through intricate structural design, fiber networks can possess auxeticity as a result of their processing. Our research has examined the auxetic behavior of two types of fiber networks: paper and heat-compressed nonwoven fabrics. Both types of samples are anisotropic arrangements of fibers and as such, their response is partially auxetic, i.e. the phenomenon is observed only in the thickness direction due to the anisotropic structure of paper and nonwoven fabrics. Through studying the behavior of these two types of fiber networks, we have observed different mechanisms for the auxetic response, which are related to physical interactions between fibers, and, in the case of the heat-compressed nonwovens, ways to affect the magnitude of the auxetic response by changing processing conditions. Overall, these results provide the needed general processing-structure-property relationships for producing auxetic fiber networks as well as demonstrate pathways to producing these structures through conventional, large scale methods.

Auxetic behavior in fiber networks

2019 Fall National Meeting

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