Theoretical Study of the Strength of Single Jet False Twist Spun Yarns

A mathematical approach is presented to calculate and predict the strength of a false twist yarn spun by means of a single air jet, based on an idealized yarn structure model developed in an earlier paper. The strength of the wrapping fibers and the core fibers and the frictional resistance of slipping fibers in the core are the load bearing components of the yarn. The resulting equations indicate to what extent yarn strength depends on the following major parameters: position of the wrapping fibers, average wrapping length and angle, fiber strain, fiber-to-fiber friction, and fiber slenderness.