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Study on the Multi-Directional Static Friction Properties of High Performance Yarns

Qi Yexiong, Iqbal Waqar, Jiang Yaming

Fibres & Textiles in Eastern Europe

2022

Vol. 30, no. 3

111-115

To further optimise the bullet-proof performance of textile reinforced composites, multi-directional friction tests of aramid and ultrahigh molecular weight polyethylene (UHMWPE) yarns were carried out by the slope method. The influence of the included angle between the high-performance yarns on the static friction coefficient for aramid and UHMWPE yarns was studied by measuring the friction coefficient. The relationship between the static friction coefficient and the included angle among the high-performance yarns was discussed. The results showed that the friction coefficient of aramid yarns was higher than that of UHMWPE yarns. Especially, at the same included angle between high-performance yarns, the static frictional coefficient of aramid yarns is 50% higher than that of UHMWPE yarns. In accordance with expectations, the static friction coefficient decreases with the increased included angle between high-performance yarns, and the included angle of high-performance yarns changes from 0º to 90º. The trend of rapid decline appeared when the included angle between high-performance yarns changed from 0º to 15º. For the actual result, the static friction coefficient of aramid and UHMWPE yarns is less than 0.3, which needs to be improved to increase the bullet-proof performance of textile composites.

Yarn Damage Evaluation in the Flat Knitting Process

Iqbal Waqar, Jiang Yaming, Qi Ye-xiong, Xu Lei

Autex Research Journal

2021

Vol. 21, no. 3

272--283

Textile yarns are subjected to numerous types of forces during knitting, usually leading to yarn damages, such as decrease in tensile, bending, shearing, and surface properties, which are closely related to different yarn properties, knitted structures/actions, and machine settings. This article comprehensively evaluated yarn damages in the computerized flat knitting process. Five different commercially available and commonly used yarns including cotton, wool, polyester, acrylic, and viscose were selected as raw materials, and the tensile, bending, shear, and frictional properties were investigated and compared before knitting and after being unraveled from plain- and rib-knitted fabrics, respectively. The results show that knitting actions/structures exhibit different damage extents for all different raw materials. It has been observed that the modulus is declined by 3–30% for bending, 2–10% for tensile, and 8–80% for shearing due to flat knitting action, respectively. The frictional coefficient of yarns also increased from 6 to 23%. As compared to yarn before knitting, the yarns unroved from plain and rib structures have been damaged to a great extent as a result of the loss of mechanical properties. The results are completely in agreement with the statistical analysis that clearly represents the significant loss in yarn properties during the knitting process. The microscopic analysis of the yarns clearly illustrates the effect of knitting action on yarn surface and mechanical properties. For yarn’s cross-sectional shearing properties testing, this article self-designed an innovative “Yarn Shear Testing Device.” The methodology and results are of great importance for improving the quality of knitted products, evaluating knitting yarns’ knittability, and in the development of high-performance technical textiles.