Creating three-dimensional (3D) fiber networks with out-of-plane auxetic behavior over large deformations

Abstract

Fiber networks with out-of-plane auxetic behavior have been sporadically investigated. One of the major challenges is to design such materials with giant negative Poissons ratio over large deformations. Here in, we report a systematic investigation to create three-dimensional (3D) fiber networks in the form of needle punched nonwoven materials with out-of-plane auxetic behavior over large deformations via theoretical modeling and extensive set of experiments. The experimental matrix has encapsulated the key parameters of the needlepunching nonwoven process. Under uniaxial tensile loading, the anisotropy coupled with local fiber densification in networks has yielded large negative Poissons ratio (up to −5.7) specifically in the preferential direction. The in-plane and out-of-plane Poissons ratios of fiber networks have been predicted and, subsequently, compared with the experimental results. Fiber orientation was found to be a core parameter that modulated the in-plane Poissons ratio of fiber networks. A parametric analysis has revealed the interplay between the anisotropy of the fiber network and the out-of-plane Poissons ratio based upon constant volume consideration

Random auxetics from buckling fibre networks

“…ref. 30 ). The large discrepancy between the tensile forces needed to extend a slender fibre and the compressive forces required to make it buckle suggests that a smaller fraction of fibres inclined towards the loading direction would be sufficient to cause the out-of-plane deflection of transversally oriented fibre segments.…”

In-Plane Deformation Behavior and the Open Area of Rotating Squares in an Auxetic Compound Fabric

“…Such structures induced in-plane auxetic behavior of the nonwoven fabrics. Bhullar et al [ 24 , 25 ] also used the rotating square geometry in polycaprolactone nanofiber webs (membranes) made by the electrospinning procedure and laser cutting. Rawal et al [ 24 ] developed 3D polyester needle-punched webs with out-of-plane auxetic behavior by adjusting the needle boards‘ direction in a needle-punching process (and, consequently, the proportion of fibers in the through-thickness direction of the webs).…”

“…Bhullar et al [ 24 , 25 ] also used the rotating square geometry in polycaprolactone nanofiber webs (membranes) made by the electrospinning procedure and laser cutting. Rawal et al [ 24 ] developed 3D polyester needle-punched webs with out-of-plane auxetic behavior by adjusting the needle boards‘ direction in a needle-punching process (and, consequently, the proportion of fibers in the through-thickness direction of the webs). Rawal et al [ 25 ] analyzed needle-punched nonwoven fabrics with out-of-plane auxetic behavior by deconstructing the anisotropic structure, and presented analytical models of the modulus and an in-plane Poisson’s ratio.…”

Towards textile metamaterials: a pathway to auxeticity and tensegrity in a needle-punched nonwoven stiff felt

“…While our work has shown that heated compression can enhance the auxetic effect in nonwovens, Rawal et al have also examined the effect of process parameters during the needle punching operation for nonwovens and found that increasing the punch density (decreasing the spacing between fiber columns) can increase the auxetic effect in these fabrics. 46,47 Extending the auxetic behavior of needlepunched nonwovens, work by Dubrovski et al have produced in-plane auxeticity in needle-punched nonwovens by using laser cutting to produce a rotating square pattern in the fabric. 48 This paper builds on what is known about auxetic nonwovens by examining the auxetic character of a stiff felt nonwoven.…”