초록
Frictional bundling of fibers is accompanied by twists that compel the bundle cohesion force to generate bundle strength. Twists generated by friction occur in two forms; one by fiber arrangement on the bundle layer and the other by torque due to the thickness distribution of the bundle on the friction surface. This study investigates the twists of a friction bundle that occur on the friction surface, and theoretical models of twists are applied to develop total twist and the twist characteristics by simulation. Results showed that the fiber arrangement twists are directionally opposite to the torque twists; fiber arrangement twists occur as S-twists and torque twists as Z-twists. In the steady state the bundle exiting the friction zone had S-twists finally and the twists per length was uniform along the bundle radius. The steady state twists of the bundle at the exit of the friction zone were determined by two model constants and a process variable. The two model constants were composed of model parameters such as slippage ratio, minimum thickness of the fleece for bundling, the density ratio of the bundle to the input fleece, and also of process variables such as friction ratio, the speed ratio of the fleece feeding to bundle takeup, and the thickness of the input fleece. The process variable acting directly on the bundle twist was the fleece feeding width. Thus, the twist angle of the bundle in the friction zone varied with the radial position inside the bundle. The twist angle was the lowest in the vicinity of the bundle axis. As the fiber layer approaches the bundle surface, the twist angle increases.
