Engineering Design and Characterisation of Auxetic Yarns and Woven Fabrics

  • Yajie Gao

Student thesis: Phd


Auxetic materials, including textiles, exhibit a negative Poisson's ratio (NPR), which is of interest for many applications. They expand laterally when stretched or shrink when compressed in contrast to conventional materials. In recent years, auxetic woven fabrics have gained much attention from researchers due to their special features, such as pore opening behaviour, impact resistance, energy absorption and clothing fit-ability. However, the development of woven fabrics made of auxetic yarns is still limited compared to other auxetic textiles because the auxeticity of the yarns cannot be fully transferred to the fabric due to the interlacement of the woven pattern. Therefore, this research aims to optimise the auxetic yarn and woven fabric manufacturing processes, establish the understanding of design principles and try to reduce the loss of auxeticity of the fabric inherited from the yarns. A series of parametric study was carried out based on the experimental and numerical methods. The research reports on the improvement of helical auxetic yarn (HAY) quality and the yarn auxeticity through studying the factors of helical angles, yarn thickness and tensile moduli, as well as the binder feeding. The maximum negative Poisson's ratio of the optimised yarn was experimentally achieved as low as -9.6 and such optimised procedures enabled the making of high-quality auxetic yarns with a wider range of machine settings than before. The results showed lower initial helical angle, higher modulus ratio of the wrap ply to the core ply led to a higher auxetic behaviour of the yarn. A concave relationship between the yarn thickness and Poisson's ratio was revealed. In parallel, woven fabrics were produced with the selected HAYs in the weft direction and in both warp and weft directions. Tensile property, porosity and impact property were evaluated and the results indicated that the auxetic fabric displayed notable geometric changes compared to the non-auxetic fabric with the same structural parameters. The auxeticity of the fabric was measured in terms of fabric thickness and fabric dimension. Seven influential factors on Poisson's ratio were analysed and the results showed that the maximum NPR can be achieved as -3.57 in thickness direction and -1.17 in warp direction.
Date of Award1 Aug 2022
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorXiaogang Chen (Supervisor) & Rachel Studd (Supervisor)


  • Negative Poisson's ratio
  • Helical auxetic yarns
  • Woven fabrics
  • Finite element analysis

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