Negative Poisson’s Ratio Weft-knitted Fabrics

TLDR

The study investigates fabricating negative Poisson’s ratio weft‑knitted fabrics that widen upon stretching. A 3‑D NPR structure built from identical parallelogram planes was designed and produced on a computerized flat‑knitting machine, and its NPR values were measured and compared to theoretical predictions. All tested fabrics displayed a decreasing NPR with increasing strain, matching theory, and the initial opening angle was found to be the key parameter, with smaller angles yielding higher NPR, confirming the feasibility of weft‑knitting NPR fabrics.

Abstract

This paper presents a study of using weft-knitting technology to fabricate negative Poisson’s ratio (NPR) knitted fabrics, which exhibit the unusual property of becoming wider when stretched. Based on a geometrical analysis of a three-dimensional NPR structure constructed with parallelogram planes of the same shape and size, a new kind of NPR weft-knitted fabric was firstly designed and fabricated on a computerized flat-knitting machine. Then the NPR values of these fabrics were evaluated and compared with those from the theoretical calculations. The results show that all knitted fabrics have the NPR effect, which decreases with increased strain in the course direction. This variation trend is consistent with the theoretical prediction. The results also show that the main structure parameter affecting the NPR effect of a fabric is the opening angle at its initial state. Fabric with a smaller opening angle will have higher NPR values. This paper demonstrates the feasibility of fabricating NPR-knitted fabrics by using weft-knitting technology if a suitable structure and parameters are selected.