| Author: | Zeeshan, Muhammad |
| Title: | Study of three-dimensional woven fabrics with in-plane negative Poisson’s ratio |
| Advisors: | Hu, Hong (SFT) |
| Degree: | Ph.D. |
| Year: | 2024 |
| Subject: | Textile fabrics Finite element method Hong Kong Polytechnic University -- Dissertations |
| Department: | School of Fashion and Textiles |
| Pages: | xix, 153 pages : color illustrations |
| Language: | English |
| Abstract: | Different from conventional fabrics, auxetic fabrics possess negative Poisson’s ratio (NPR), which means that they show an unusual lateral expansion when stretched longitudinally. Auxetic textile fabrics have received significant attention due to their extraordinary behavior and improved characteristics because of the NPR. Until now, several two-dimensional (2-D) and three-dimensional (3-D) woven and knitted auxetic fabrics have been developed by researchers using different approaches. Auxetic behavior in woven fabrics can be induced by two methods. The first and simple method is to use a special auxetic yarn in the warp, weft, or in both directions to achieve NPR. Although this is the simplest approach to produce auxetic effect, however, there are some drawbacks linked with auxetic fabrics made using this method. Those drawbacks include, unstable auxetic behavior, incomplete transfer of auxetic property from yarn to fabric due to structural limitations, and auxetic yarns need a special arrangement for auxetic effect which makes the weaving process more complicated. The second method to produce auxetic woven fabrics is to realize auxetic geometry by using conventional elastic and non-elastic yarns in the warp and weft directions. After many potential developments in knitted auxetic fabrics, this method has now gained extraordinary interest of researchers to develop woven auxetic fabrics. So far, 2-D uni-stretch and bi-stretch woven fabrics have been developed based on this method. However, there are some limitations associated with these fabrics that include, low NPR, higher longitudinal deformation under tension, and a decrease in auxetic effect at high deformation. In addition, the development of 3-D woven fabric having in-plane auxetic behavior is still unaddressed. This study aims to design and develop a novel 3-D narrow woven fabric that will exhibit in-plane auxetic behavior. A 3-D multilayer orthogonal through thickness structure was specially designed with three different yarn components to incorporate auxetic geometry. One type of yarn was used in warp direction, while the two weft yarn systems, comprised of elastic yarn and coarse binding yarn, were used. The auxetic geometry resembles the re-entrant hexagon that was achieved by the unusual arrangement of warp yarns. The fabric samples were fabricated using a conventional semi-automatic weaving machine with four different influencing parameters for in-depth study. All the developed samples were tested on a tensile testing machine (Instron 5982) to evaluate the mechanical and auxetic behavior. The 3-D fabrics showed auxetic effect even at higher tensile strain. The results show that the appropriate binding to warp yarn diameter can produce a higher NPR of the fabric. While the repeat size of elastic weft yarn can highly affect the NPR of the fabric. The low bending stiffness of coarse binding yarn and low to moderate stretch percentage of elastic weft yarn are favorable for generating higher auxetic behavior. Furthermore, among all the 3-D woven fabrics developed with different structural parameters, the maximum Poisson’s ratio achieved was -1.61. After the experimental study, a geometrical model is proposed for the 3-D auxetic woven structure based on the geometrical arrangement of yarns that causes the NPR effect. A unit cell of a structure is first identified and then a relationship between longitudinal and lateral deformations of the structure is established in the form of semi-empirical equations. For validation of the model, the experimental results of the developed woven fabrics were correlated with the calculated results from the geometrical model. It was found that the calculated results were in good agreement with the experimental results. After experimental validation, the model was used to calculate and discuss critical parameters that affect the auxetic behavior of the structure. Thus, the geometrical analysis is believed to help predict the auxetic behavior of 3-D woven fabrics with different structural parameters. While experimental and geometrical studies of the 3-D auxetic woven structure provide primary information, these studies have limitations in explaining the auxetic behavior of the 3-D woven structure at the yarn level. In addition, predicting the auxetic behavior of the 3-D woven structure by varying material properties is only possible through finite element (FE) analysis. Therefore, a 3-D FE model of the structure was developed to simulate the auxetic behavior of the structure. The structure was studied with different binding yarn properties once a good agreement was found between simulated and experimental results. The FE analysis provides new insights and uncovers fresh discussions regarding the auxetic behavior of the 3-D woven structure. With all the scientific discussions in light of the developed FE model, this study is expected to provide a better foundation for the future development of 3-D auxetic woven structures. |
| Rights: | All rights reserved |
| Access: | open access |
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