Study on a theoretical model of braided auxetic yarns made from a high-speed braiding machine

Abstract

The main content of this article theoretically analyzes the yarn diameter and Poisson's ratio variation of braided auxetic yarns under axial strain. Braided auxetic yarns are composed of three components: wrap yarns, the core yarn, and the stiff yarn. The core yarn has a larger diameter and smaller elastic modulus than the other two kinds of yarns, but its rigidity is lower. There is a lack of theoretical basis for predicting the Poisson's ratio of braided auxetic yarn. Based on the geometric model, the curve of the Poisson's ratio has been determined and the Poisson's ratio trend of braided auxetic yarns is deduced, aiming to predict the Poisson's ratio of braided auxetic yarns under axial strain with accurate yarn parameters. The experimental results show that the minimum Poisson's ratio of theoretical value and actual value appears under the same axial strain, and the variation trend of Poisson's ratio of both values is consistent. The Poisson's ratio curve of braided auxetic yarns is predicted, which lays a theoretical foundation for the development of auxetic materials and also provides more possibilities for subsequent research.