Study on negative Poisson’s ratio of auxetic yarn under tension: Part 2 – Experimental verification

Abstract

Auxetic yarn was successfully produced by a wrap filament and a core filament based on a ring-spinning system, which showed an auxetic effect when stretched, that is, expanding transversely under tension. Yarns were spun by different structural parameters of the core filament and the wrap filament, including diameter ratio, helical angle and tensile modulus of the wrap filament. Corresponding tensile tests were utilized to analyze the effects of structural parameters and performance on outer contour deformation of auxetic yarn. Experimental results showed that the outer contour of auxetic yarn expanded transversely under tension and there existed significant negative Poisson's ratio values in the Poisson's ratio-strain curve, and it was found that the auxetic effect became more observable with a higher diameter ratio of the core filament to the wrap filament, and lower helical angle and larger tensile modulus of the wrap filament. Moreover, compared with theoretical results by theoretical modeling in Part I, good relations of Poisson's ratio-strain curves were obtained between experimental and theoretical results. This proves the effectiveness of spinning auxetic yarn by selecting reasonable components of yarn and it is feasible to design yarn with a negative Poisson's ratio effect.

Tensile and Deformation Behavior of Auxetic Plied Yarns

“…It can be seen that DHY, 4‐ply, and 6‐ply auxetic yarns have a significant variation in auxetic behavior under stretching. DHY A‐1‐D has the same kind of Poisson's ratio‐strain curve and similar auxetic characteristics consistent with the references, that is, the Poisson's ratio is positive and increases with increasing tensile strain at the beginning of stretch, then decrease till its maximum negative value and finally increases toward zero until the yarn is broken. It is interesting to note that due to the core‐wrap structure of the DHY, the initial elongation is inevitably accompanied with a positive Poisson's ratio.…”

“…Wright, Sloan and Evans carried out a finite element analysis and an experimental study to investigate the influence of structural and material parameters on the auxetic performance of the DHY . Du et al conducted a theoretical analysis to predict the auxetic performance of the DHY for any given tensile strain and an experimental study afterward to verify the accuracy of the model . Sibal and Rawal also proposed a DHY system to predict the auxetic behavior of the DHY through energy minimization approach .…”

“…[21,23] Du et al conducted a theoretical analysis to predict the auxetic performance of the DHY for any given tensile strain and an experimental study afterward to verify the accuracy of the model. [24,25] Sibal and Rawal also proposed a DHY system to predict the auxetic behavior of the DHY through energy minimization approach. [26] Bhattacharya et al investigated the core-indentation effects on the auxetic behavior of the DHY.…”

Theoretical Modeling on the Deformation Behavior of Auxetic Tubular Braid Made from Modified Circular Braiding Technique

“…It is believed that a lower initial wrap angle can lead to a larger maximum NPR. [20,21,[24][25][26] In contrast, there may also exist an critical angle for obtaining the largest NPR, below or above which the maximum NPR of HAY will be impeded. [22] With respect to the Poisson's ratio of core and stiff yarns, it is found that the auxetic effect of HAY is increased with the decrease in their Poisson's ratio.…”

Large-scale manufacturing of helical auxetic yarns using a novel semi-coextrusion process

“…Bhattacharya et al 20 found that the core indentation effect (the wrap fiber embeds into the core fiber) would reduce the auxetic performance of the HAY; therefore, this phenomenon should be eliminated during the manufacturing process. Du et al 21,22 carried out theoretical and experimental studies to investigate the effect of different design parameters on the auxetic performance of HAY. Zhang et al 23 fabricated a novel three-component auxetic structure based on a HAY and they indicated that the coating thickness was identified as a new design parameter for tailoring the auxetic effect.…”