| Author: | Xuan, Yanzhuang |
| Title: | Design and fabrication of strong non-woven fabric-based yarns |
| Advisors: | Yao, Haimin (ME) |
| Degree: | M.Sc. |
| Year: | 2023 |
| Subject: | Nonwoven fabrics Textile fabrics Hong Kong Polytechnic University -- Dissertations |
| Department: | Department of Mechanical Engineering |
| Pages: | x, 73 pages : color illustrations |
| Language: | English |
| Abstract: | Nonwoven fabric (NWF) is a textile material widely used in the medical and health field to produce products such as masks and wound bandages. Since NWF is a sheet composed of randomly stacked short fibers, it exhibits much lower strength than the other woven fabrics and, therefore, can barely sustain the mechanical load. As a structural material, to widen the application spectrum of NWF, a view of twisting NWF strips into yarns and then weaving the yarns into fabric has been proposed. In this dissertation, the effect of twisting on the strength of the yarns was studied systematically. Several factors(the strength of the original NWF strips, the strip width, the yarn twist level) affecting yarn strength need to be considered. A series of experiments (uniaxial tensile experiment, data significance analysis, digital image processing) were performed to evaluate the influence of these factors. Strip strength and yarn strength were determined by uniaxial tensile experiments. Significance analysis was used to analyze the differences in data sets and demonstrate significant trends. The fiber orientation distribution function (ODF) obtained by image processing reveals the preferential direction of most fibers. Experimental results prove that NWF strips cut along ODF maximum direction are stronger. The NWF strips were twisted into yarns, and the tensile strength's dependences on the strip width and yarn twist levels were researched. To fairly compare the load-carrying capacity of the yarns, the value of the yarn's maximum load divided by the original NWF strip width is used to express the yarn strength in this dissertation. The experiment result shows that when the twist level increases, the yarn strength first increases and then decreases. There exists an optimal twist level at which the strength of the NWF-based yarns reaches the maximum. The operation of pre-rolling can significantly improve the yarn load capacity. At the optimal twist level, NWF-based yarns with pre-rolling were stronger. To reveal the mechanism accounting for the optimal twisting level, the finite element analysis was carried out with a simplified fiber bundle model. The results show that the twist level increases the friction between fibers. The higher the twist level, the greater the friction that hinders the relative movement of the fibers. If the twisting level is less than the optimal twist level, the higher the twist level, the harder to separate the fibers and the corresponding pulling force increases. If the twisting level is higher than the optimal twist level, the fibers fail before they are separated from each other. The higher the twisting level, the less the pulling force when the fibers are separated. It reveals why the yarn strength first increases and then decreases when the twist level increases. In conclusion, this dissertation analyzes the factors influencing NWF-based yarn strength. The cutting direction should be the most fibers’ preferential direction to obtain stronger NWF strips. A strong NWF-based yarn can be obtained with pre-rolling and twisting at optimal twist level. The strong NWF-based yarns can be used to improve the load-carrying capacity of NWF products and the spinnability of short fibers. |
| Rights: | All rights reserved |
| Access: | restricted access |
Files in This Item:
| File | Description | Size | Format | |
|---|---|---|---|---|
| 7483.pdf | For All Users (off-campus access for PolyU Staff & Students only) | 3.05 MB | Adobe PDF | View/Open |
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