Clothing Pressure of Knitted Fabrics Estimated in Relation to Tensile Load Under Extension and Recovery Processes by Simultaneous Measurements

Abstract

Clothing pressure of knitted fabrics was estimated by two methods using an air pack. In Case 1, the pressure by shrinkage of extended fabrics was measured by an air pack put on the cylinder, in which the air pack was inserted between the knitted fabric extended to a desired strain and the cylinder as a basic substance. The tensile load at a given strain of the knitted fabric covered on the cylinder was estimated from the same strain of the extended knitted fabric measured by a strip biaxial tensile tester. The pressure on the cylinder was predicted on the basis of the relationship between pressure and surface tension for a curved thin liquid film. The predicted pressure was in good agreement with the pressure measured, when the curvature of the air pack on the cylinder was taken into consideration along the cylindrical axis. In Case 2, the hysteresis routes of clothing pressure and tensile load under extension and return processes were measured simultaneously as a function of strain. The hysteresis routes of the pressure provided a similar tendency to that of tensile load. Furthermore, the corresponding tensile load routes were calculated on the basis of hypothesis associated with stress relaxation based on hereditary integral and the clothing pressure with a hysteresis route was predicted by substituting the tensile load into the pressure-tension relationship concerning a liquid surface used in Case 1. The pressure routes predicted by choosing a suitable exponent parameter were in good agreement with the pressure routes measured.