Abstract
Auxetic materials, including textiles, exhibit a negative Poisson’s ratio (NPR), which is of interest for many applications. This research aims to optimize the structural parameters of helical auxetic yarns (HAYs) and to evaluate the auxetic performance of these yarns. The research reports on the improvement of auxetic yarn quality and the yarn auxeticity through studying the effect of helical angles, diameter ratio and tensile moduli of the two plies, as well as the binder filament feeding. The maximum NPR of the optimized auxetic yarns was experimentally achieved as low as –9.6, with the helical angle of around 14.0° on average using the optimal machine setting. The optimized yarn parameters enabled the making of high-quality auxetic yarns with a wider range of machine settings than before. In parallel, theoretical and numerical studies were carried out for the engineering design of auxetic yarns, which enabled comparisons among the experimental results, calculated results and results from finite element analysis. The comparison showed that a lower initial helical angle, higher tensile modulus of the wrap ply and lower tensile modulus of the core ply led to a higher auxetic effect. A new finding is reported in that a concave relationship between the diameter ratio and the NPR was discovered. The results of this study could assist researchers in producing HAYs, and this type of HAY could be used for many potential applications, such as filtration and impact protection.
Highlights
Auxetic materials, including textiles, exhibit a negative Poisson’s ratio (NPR), which is of interest for many applications
The research results indicated the helical auxetic yarns (HAYs) can be designed by setting parameters and the NPR value can be improved by increasing the tensile modulus of the wrap ply and the diameter ratio of the core ply to the wrap ply, as well as decreasing the helical angle
In order to investigate the tensile property of the HAY, a polyester (PET) wrap ply with the linear density of 11.1 tex was involved for making a yarn
Summary
Auxetic materials, including textiles, exhibit a negative Poisson’s ratio (NPR), which is of interest for many applications. Further study on HAY was carried out to investigate the influence of the diameter ratio of the two plies, the wrapping angle and the tensile modulus on the auxetic behavior.[6] It was confirmed that a lower helical angle, a higher diameter ratio of the core to the wrap and an increased tensile modulus of the wrap could achieve a greater value of the NPR.[7,8] The maximum NPR of the yarn they achieved was as low as – 4.94 This type of auxetic yarn can be made into fabrics[9,10] and composites[4] for various applications. The optimization of the yarn quality focused on machinery that could apply to large-scale production
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