Auxetic textiles comprise a class of extraordinary materials that increase in size when stretched and are being considered in many applications of technical. Read article about Article By L. Preethi & A. Sahana, Auxetic Textiles, Unique Materials That Exhibit Negative Poisson’s Ratio, Auxetic Textiles Possess High. This paper deals with Auxetic textiles that is been developed as a smart materials to meet the high demand in the fields of technical textile. These materials show.
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When stretched either in horizontal or vertical direction, aauxetic parallelogram changes its inclined position related to the surface plane of the structure, which auxeitc in an opening of the whole structure by increasing its dimensions in both the horizontal and vertical directions. Hook P, Evans K. To produce such knits the same combinations of stitches are used, though in one case the coupled wales of tricot-tricot stitches are formed on different needles.
Further, due to the limitations like low structural stability, low elastic recovery, higher thickness and difficulty in the fabrication because of their complicated geometrical structures, auxetic knitted texitles cannot be successfully used in garment manufacturing but they have other potential applications including, vibration damping, shock absorbency and reinforcement for composites.
When the fabric is extended along the course direction, the width in the warp direction increases. Thus, unit sizes with larger a 1 can become wider during stretching.
The texhiles warp knit fabrics were made from 2 ends ground yarn of denier polyester yarn manufactured by Du Pont. This construction exhibits auxetic behavior.
In warp knitting a wale can be produced from the same yarn. It was found that the calculated results from the geometric analysis are close to the experiment ones, except in the initial extension stage where the variation trends between the experiment and calculation are opposite.
This is because with an increase of loading, the axial strain increase is faster than in the transverse strain due to the yarn transfer from the transverse direction to the axial direction. This is due to the fact that larger tricot courses lead to longer length of vertical rib values. In addition, the length of each rib side of the fabric can be easily deformed under loading. Whereas the measured auxetic effect decreases with an increase of the strain, the calculated auxetic effect rises with increase of the strain and the auxetic effect calculated is much higher than that measured.
Symmetrical nets are produced when two identically-threaded guide bars overlap in balanced lapping movements in opposition.
The resultant functional auxetic knit structure is shown in Figure 10d.
Auxetiic 19 a Diagram showing stitch structures that can be altered to produce auxetic effects. It has been suggested [ 18 ] that an auxetic fiber within a composite would resist fiber pull-out. Figure 2 Liquid crystalline polymer LCParrangement of main chain The knitting process is shown auxetid Figure 17a. Thus, the use of auxetic fibers in an engineered textile structure can be facilitated tectiles the development of cost effective, productive processes in which large quantities of textile materials exhibit the very unusual, interesting and useful property of becoming wider when stretched and thinner when compressed.
Auxetic materials can also be used as core materials in curved sandwich panel composite components, radome applications, directional pass band filters, micro-electro-mechanical system MEMS devices, seat cushion material and fastening devices. Journal of Cellular Plastics. The other component is an elastic material of lower modulus of elasticity for example siloxane.
Engineered Warp Knit Auxetic Fabrics | OMICS International
In case of plain and twill weaves the floating length is equal both in warp and weft direction. It is usual for composites to be multi layered.
As one of the advantages of auxetic fabrics over conventional fabrics is their excellent shape fitting ability on a curved surface due to the formation of synclastic curvature under bending condition.
The auxetic effect of the structure mainly comes from the rotations of ribs around their connecting points uaxetic a tension is applied to the fabric structure. The textile structure was woven using a plain weave, with the weft being the DHY and the warp being a meta-aramid fibre approx dtex.
Engineered Warp Knit Auxetic Fabrics
The loop transfer method was used to change between the face and reverse loop. The knitting pattern is shown in Figure 13a.
They employed foldable structure, rotating rectangles and reentrant hexagons geometries to induce auxetic behavior in knitted fabrics by using conventional yarn types and computerized flat knitting machines.
Upon stretching the high stiffness filament get straight and becomes fully aligned causing the open loops of lower stiffness filament to wrap around the straightened high stiffness filament as shown in Figure 10b exhibiting the auxetic behavior.
Three geometrical parameters, i. The auxetic effect is produced due to hinging as shown in Texxtiles 18aleading to opening of the network of arrowheads. Schematic of geometrical model for the Structure. However, in the case of auxetic material, double curvature can be easily achieved [ 18 ].