Effect of Different Yarn Combinations on Auxetic Properties of Plied Yarns

This study presents the effects of a novel plied yarn structure consisting of different yarn components and yarn twist levels on the Poisson's ratio and auxetic behavior of yarns. The plied yarn structures are formed with bulky and soft yarn components (helical plied yarn [HPY], braided yarn, and monofilament latex yarn) and stiff yarn components (such as high tenacity [HT] and polyvinyl chloride [PVC]-coated polyester yarns) to achieve auxetic behavior. Experimental results showed that as the level of yarn twist increased, the Poisson's ratios and the tensile modulus values of the plied yarns decreased, but the elongation values increased. A negative Poisson's ratio (NPR) was obtained in HT–latex and PVC–latex plied yarns with a low twist level. The plied yarns formed with braid–HPY and braid–braid components gave partial NPR under tension. A similar result was achieved for yarns with HT–latex and PVC–latex components. Since partial NPR was seen in novel plied yarns with braided and HPY components, it is concluded that yarns formed with bulky–bulky yarn components could give an auxetic performance under tension.

Finite element simulation of an auxetic plied yarn structure

Auxetic plied yarn is a novel type of yarn structure formed with two types of component yarns with different moduli. Although the effect of structural parameters on its negative Poisson's ratio behavior has been investigated by both experimental and geometrical analyses, the influence of material properties, including yarn tensile modulus and friction, has not been studied yet. In this work, these two factors are further investigated via finite element simulation. The finite element model is first created by using the commercial software ANSYS 15.0. Then, the simulation results are compared with the experimental and analytical data. Finally, the effects of the tilt angle of stiff yarn, yarn friction and tensile modulus are discussed. It is expected that the outcomes of this work would be useful to guide the design and fabrication of this type of auxetic yarn structure.

All-carbon cord-yarn supercapacitor

Flexible solid-state yarn supercapacitors were fabricated using commercial carbon fiber and activated carbon fiber. Two methods of yarn construction were studied. One was twisting carbon fiber and activated carbon fiber together (plied yarn), and the other was wrapping activated carbon fiber on carbon fiber (wrapped yarn). Electrochemical measurements in terms of cyclic voltammetry (CV), galvanostatic charge/discharge (GC) and electrical impedance spectroscopy (EIS) were conducted. The result revealed that the cord-yarn structure performed better than the core-spun yarn structure, by showing a specific length capacitance of 82 mF cm−1 at 2 mVs−1. It also exhibited a high specific length energy density of 20.4 μW h cm−1 at a power density of 60 μW cm−1. There was little capacitance reduction when the cord-yarn supercapacitor was bent or crumpled, showing an excellent mechanical flexibility.

Qualitative Analysis of Siro-spun and Two Fold Yarns Tensile Properties under the Influence of Twist Factor

Siro yarns are spun from two separate roving of same type of materials. Similarly in textile arts,folding is a process used to create a strong and balance yarn by putting together two separate yarns. Hence,this research study was carried to analyse the quality of Siro-spun and two fold yarns under the influenceof twist factor with special reference to their tensile properties. The results disclosed better tensile propertiesof yarn made from Siro spinning technique as compared to two plied yarn. This indicates the supremacyof Siro-spun yarn over two fold yarn. These findings enhance the fact that Siro spinning technique producesbetter quality yarn as compared to conventional ring spinning technique.

Mechanical Properties Of Traditional And Nanofibre Textiles

This study deals with a comparison of mechanical properties of a conventional yarn and a textile from nanofibres. The conventional yarn represents the textile objects with high degree of orientation of fibres and the textile from nanofibres represents the textile objects with low degree of orientation of fibres. The theoretical section is concerned with the issue of internal structure of plied yarn and resulting differences in the orientation and straightening of fibres and in utilisation of deformation properties of fibres in comparison to the referred nano textile. The experimental section describes the manner of realisation of both static and dynamic tests of conventional yarn and strips of nanofibres. The results show differences in the mechanical properties of conventional yarn and textile strip from nanofibres under static and dynamic loading conditions. The processing technology of conventional yarn has been verified in the long term. But textiles from nanofibres are a relatively new material and mechanical properties of the detected differences point out possible problems with their behaviour during standard technological processes.

Effects of Tooth Number of Drive Gear on Mechanical Properties of Polypropylene/Polyester Composite Tubular Knits

The severe global climate changes result in consecutive torrential rains in rainy season, and causes water loss and soil erosion. For an effective water and soil conservation, geotextiles are commonly used in geotechnical engineering. Geotextiles should able to isolate soil, filter water, and reinforce the soil; therefore, the material for geotextiles should be acid-resistant and alkali-resistant, such as polypropylene (PP) and polyester (PET). This study uses PP fibers as the skin and PET plied yarns as the core to form PP/PET composite tubular knits on a cord knitting machine. The PET plied yarn is fed with a specified tensile strength, and only the tooth number of the drive gear varies. Mechanical property test results show that a drive gear of 30 teeth increases the tensile strength of the resulting tubular knits; however, with a drive gear of 35 teeth, the tensile strength decreases. An optimal core coverage occurs with a drive gear of 30 teeth.

Electromagnetic shielding effectiveness and functions of stainless steel/bamboo charcoal conductive fabrics

Following technological advancements, there is a growing population of cellular phone and computer users. However, these electronic instruments cause electromagnetic waves, negatively influencing users’ health or precision instruments’ malfunction. Therefore, shielding electromagnetic wave becomes an important matter. In this study, stainless steel wires and bamboo charcoal roving are made into conductive yarn with 6 turns/cm by ring spinning machine. On a 14-gauge automatic horizontal knitting machine, the resulting yarn is then knitted into stainless steel/bamboo charcoal conductive fabrics and then evaluated for the electrical property and functions. According to experimental testing, electromagnetic shielding effectiveness (EMSE) of the fabrics increases with an increase in stainless steel content and number of lamination layers. In particular, when laminated at an angle of 0°/45°/90°/−45°/0°/45°, the fabrics have an EMSE of above 30 dB at an incident frequency between 2010 and 2445 MHz. The far infrared emissivity increases with bamboo charcoal content, reaching the maximum of 0.9 ɛ, when the fabric was made by one-cycle polyethylene terephthalate (PET)/stainless steel/bamboo charcoal plied yarn in the first feeder and four-cycle PET/bamboo charcoal plied yarn in the second feeder.