Universal Journal of Mechanical Engineering 1(2): 62-67, 2013 http://www.hrpub.org DOI: 10.13189/ujme.2013.010205 Mechanical Properties of Weft Knitted Fabrics in Fully Stretched Status along Courses Direction: Geometrical Model Aspect Dariush Semnani Department of Textile Engineering, Isfahan University of Technology, Isfahan, 84156-83111 Iran *Corresponding Author: d_semnani@cc.iut.ac.ir Copyright © 2013 Horizon Research Publishing All rights reserved. Abstract Weft knitted fabric structures have got new application in the modern technical textile such as seat belt and packaging fabrics. The weft knitted fabric is applied for technical textiles commonly as composites to resist against tension along courses direction in jamming status. In this study, mechanical properties of weft knitted fabrics with different structures of single jersey and double jersey in fully stretched status of jamming were considered by geometrical modeling. Ultra high tenacity nylon 6.6 yarn was used in manufacturing of weft knitted fabrics. Consequently the tenacity of the sample fabrics is assessed by a tensile tester. Mechanical properties of the fabrics are compared with theoretical modeling. The results show that the weft knitted fabrics with Rib structure have a superior tenacity. Also, double jersey fabrics of Full Cardigan and Full Milano represent better mechanical properties in comparison with single jersey fabrics. Keywords weft knitted fabrics; geometrical modeling; mechanical properties; jamming status, knitted stitch 1. Introduction Textile products of technical applications have been developed in protection and safety. The most important merit in those applications is high strength and work of rapture properties of knitted fabric. The belts of packaging and protection applications must present high strength with high work up to rapture property [1]. Many researches have been concerned in design and study on mechanical properties of fabric composites with reinforcement polymers. Most of composites are produced with compositions of woven fabrics of polyester, nylon 6, nylon 6.6 and tenser yarns and reinforcement polymers as heat treated binders. Although most of those composites have remarkable strength, but, none of them have enough elongation property. Therefore, the work up to rapture is not sufficient for packaging applications [1, 2 and 3]. Other researches have been done to develop composite industry for simple knitted fabrics as base fabric in composites with shrinkable polymers of heat treated binders. These products presented better mechanical properties specially, regarding to impact resistance [4 and 5]. In these researches the effect of fabric structure has not been considered, sufficiently. Many researches have been done to consider stress/strain properties of knitted composites to make strong materials applicable in heavy industries [6, 7 and 8]. Also impact resistance has been investigated in knitted composites to achieve high resistant materials for heavy lift applications [9, 10,11and 12]. Weft knitted fabrics is made from connecting of yarn loops in hieratical courses. Each loop is consisted of one head loop, two vertical stems and two horizontal half circles as lower stems. While vertical force is applied along courses to the fabric, the loop elongated in vertical position and jamming phenomena is occurred in vertical position. This matter is occurred in horizontal position while the force is applied along walls. Therefore, the knitted fabrics have remarkable work up to rapture resistance against both vertical and horizontal forces specially, forces along courses. Weft knitted fabrics which are knitted in one needle series have hieratical courses in one surface. The other rib fabrics which are knitted in two needle series (cylinder/dial in circular and two beds in flat knitting machines) have two series of courses in two surfaces. In these kinds of knitted fabrics the loops are connected together in two directions of both courses. Therefore, it seems rib fabrics can present better mechanical properties in comparison with plain ones. Elements of knitted fabrics, which are knit, tuck and skip stitches, demonstrate different structures of fabric depend on design of fabric. Usually, tuck and skip stitches cause more stability and less shrinkage in knitted fabric. Skip stitches have no noticeable effect on thickness of fabric while tuck stitches causes increasing thickness and covering factor of fabric [13].