The Effect of Fabric Structure and Strain Percentage on the Tensile Stress Relaxation of Rib Weft Knitted Fabrics

Stress relaxation is a time-dependent behavior in textiles, which occurs with the release of stresses when the textile is under constant strain over a period of time. This phenomenon will induce disturbances in textile performance in applications such as pressure garments, varicose stockings, pressure bandages and etc., in which it is critical to maintain pressure on the scar area, within a certain range according to instructions from doctors or therapists. Consequently, by theoretical and experimental research on the factors affecting stress relaxation, it will be possible to design and produce appropriate functional clothes. In the present study, double jersey weft knitted fabrics with five different knit patterns differing in the number of back bed tuck stitches have been produced and the effect of fabric structure and strain value on the stress relaxation of the fabrics in the course direction have been investigated. The results reveal that by increasing the number of tuck stitches in the fabric structure, the initial and residual stress values decrease whilst the stress relaxation of the fabric increases. Moreover, in all fabric structures, applying higher tensile strain will cause higher stress in the fabrics as well as increase the stress relaxation of the fabrics. Eventually, three components Maxwell model with parallel connected nonlinear spring proposed as the best model that matches the experimental results. As a whole, to enhance the functionality of pressure garments, varicose stockings and compression bandages, the use of tuck stitch in the fabric structure is not recommended.