Dynamics of elastic knitted fabrics for tight fit sportswear

Abstract

Elastic fabrics and their garments have instant response and return to their original size and shape due to physical exertion by any organ of the human body. These garments are mainly used in sports activities such as cycling, swimming and athletics, as they improve the sportsmen performance by offering least resistance during garment stretch and by enhancing the power by quick recovery of the fabric dimensions. The dynamic elastic behaviour such as dynamic work recovery and stress at specific extension of the fabrics helps to analyze the instant garment response to body movements. It is an objective evaluation of the performance of the elastic fabrics for tight fit sportswear. The analysis of this dynamics will help to engineer new products for improving the stamina and speed of the sportsmen, as one particular type of garment doesn’t serve the purpose of all kinds of sports events. The research work mainly deals with the effect of material variables, machine variables and processing treatments on dynamic elastic behavior of cotton / spandex knitted fabrics. The analysis of dynamic elastic behaviour of the cotton / spandex knitted fabric helps to study the performance of the garment for sports person who require stamina and power during strenuous sports activity. These fabrics were tested for their dynamic elastic behaviour such as dynamic work recovery and stress at specific extension based on ASTM D 4964 – 96 method at different extension levels such as 20%, 30%, 40% and 50% extension using Instron tester. Since, human body movement expands the skin by 10 to 50% at different parts of the body. The effect of material variables on dynamic elastic behaviour of the fabrics were carried out with the different sets of comparisons. In order to study the level of performance of the cotton / spandex fabric, the comparison of dynamic elastic behaviour of cotton and cotton / spandex knitted fabrics was made. The cotton / spandex fabric was found to be more beneficial than cotton fabric with respect to dynamic elastic characteristics due to its quick work recovery which enhances the power of the performance of the sports person. Two commercial production methods such as spandex back plated cotton knitted (SBPC) fabric and spandex core cotton spun yarn knitted (SCCS) fabric production methods exist to produce elastic knitted fabrics. The comparison of the dynamic elastic behaviour of SBPC fabric and SCCS fabric was made, in order to analyse the suitability of the fabrics for tight fit sportswear. The effect of yarn structure on dynamics of the fabrics was analysed by comparing the dynamic elastic behaviour of cotton / spandex knitted fabrics made from ring and rotor yarns, and ring and compact yarns. In order to study the effect of machine variables on dynamics of the elastic fabrics, analysis of spandex input yarn tension, spandex linear density and cotton yarn loop length have been studied. Heat setting is to stabilise the desired fabric properties of width, weight, stretch and power. Under-setting results in eventual loss of fabric dimensions; over heat-setting lowers power. Compacting is a mechanical process by compactors that physically rearrange the geometrical relationship of yarns in a fabric. The effect of heat setting and compacting temperatures on dynamic elastic behaviour of cotton / spandex knitted fabric was carried out, in order to optimize and improve the dynamic elastic behaviour of the fabrics. The study of laundering effect on dynamic elastic behaviour of cotton / spandex knitted fabric was carried out, in order to improve the laundering cycle which in turn leads to increase in the economics of the elastic garments usages. Garment pressure comfort is measured indirectly by calculating the fabric dynamic work recovery and the stress at specific extension by using Instron tester. In the Instron test, analysis of DWR test results for the knitted fabric is difficult due to the directional effect. In order to overcome the effect, pressure sensing device for analyzing the pressure comfort of elastic garments have been designed and developed. Pressure values obtained from the new pressure sensing device and the Instron tester has given good correlation.