Investigation Of Sensitivity Of Conductive Fabric Knitted By CCFS

With the progress of intelligent materials and micro-computer technology, studies of smart textile were applied in various fields, such as military, medical, sports and entertainment, electronics and electric and so on. Smart textile incorporates manifold technologies, micro-electronics, information dissemination, sensors and computer technology. It consists of three parts, including sensors, drive units and control unit, which can respond and feedback signal in accordance with the requirements that let the clothing and textile become a multifunctional"conscious"and"perceptual"system. Development of multifunctional smart textile which can also be comfortable enough to people has become a competitive point in the field of international textile. It also is a new growth point of economic effect in the industries of costumes and textile. As the future popularity of the concept of intelligent stylish living, smart textile will be a very nice prospect on the market.Based on the domestic and international studies about smart textile, this research work knitted a rudiment of flexible sensor, conductive knitted fabric. The work is starting from the spun from of yarn, designing different shares and twists, then finding the relationship between the change of resistance and elongation according repeating and staggered tensile tests. It also analyzed effects on the conductive properties by structure and finding the best structure of yarn according to the correlation coefficient between change of resistance and elongation and gain factors (GF). After the study of yarn, different structure of knitted fabric was made by the conductive yarn. Two kind of knitted fabrics, Single Jersey and Rib 1+1, were be chosen. Find the relationship of resistance change and deformation of fabric by searching the conductive and sensitive performance of which under the dynamic tensile, and analyze effects on the sensitive of conductive fabric by structure of yarn and fabric. In this research, sensitive performances relate to sensitivity, linearity, repeatability and stress relaxation characteristics. Considering the purpose of this conductive fabric, as a sensor in smart clothing, it analyzes effects on degree of washable. In the last part, based on the deformation of unit loop under strain, it investigates the theoretic reason on the resistance change of fabric from microcosmic structure.Based on a mass of references reading, this work improved the device of dynamic tensile, and gave some testing means for evaluating and analyzing the performance of knitted fabric, such as one-off tensile, repetitive tensile, tension under different speeds and washing test. The tests arrived at conclusions as follow:1. The trend of resistance change under strain was split into two phases: 0-7mm (elongation of 0-11.67%) and 7-15mm (elongation of 11.67-25%). Conductive yarn with more shares has lower sensitivity, otherwise the higher sensitivity. Conductive yarn could improve linearity by twisting. If the way of making flexible sensor is embedding conductive yarn to fabric, the parameter of yarn should be chosen by tension range of sensor.2. The resistance change of conductive fabric is contrary to which yarns has. The resistance goes steadily downhill in the mass, through the conic return analysis, the correlation coefficient reaches up to 0.992, which is the same as the result of yarn experiment, the extent of fitting about fabric made of untwisting yarn is higher than that of twisting yarn.3. The scope of resistance change of 4 kinds of knitted fabric sorted from higher to lower is: Single Jersey with combine yarns > Single Jersey with twist yarns > Rib 1+1 with combine yarns > Rib 1+1 with twist yarns. From the sturcture of fabric , Single Jersey's scope of stability is better than Rib 1+1's.4. The sensitivity of 4 kinds of knitted fabric sorted from higher to lower is: Single Jersey with combine yarns > Single Jersey with twist yarns > Rib 1+1 with combine yarns > Rib 1+1 with twist yarns. The sensitivity of Single Jersey fabric is better than the one of Rib 1+1 fabric.5. The difference of resistance change of Rib 1+1 fabric is smaller under tension by different speed, and the repeatability, stress relaxation characteristics is better than which of Single Jersey fabric. As this result, structure designing of knitted fabric sensors could choose Rib 1+1 to reduce the error during signal monitoring if it's sensitivity meets the requirements.6. The resistance of conductive knitted fabrics increased obviously after repeated washing, and the resistance change became more and more unstable. The stability of Rib 1+1 fabric is worse than that of Single Jersey fabric. The reason of this result is the flatness of initial stage become more and more worsen after washing.7. The change of knitted fabric's resistance is mainly due to the change of contact resistance between conductive yarns. so, the study of knitted fabric sensors should attach importance to the contact resistance of overflod yarns.The research directions and ideas in this work will guide the future study on flexible textile sensors. The theory, method, experimental data, the improved structure of yarn and fabric in the research also will provide important and valuable theoretical and practical bases for future development of smart textiles.