A Study of Various Mechanisms of Attrition of Fibres as a Result of Abrasion

This paper presents an account of an experimental study of the pure-bending and recovery properties of both continuous-filament and spun yarns. The bending behaviour of yarns is approximately represented by a simple two-element rheological model of an elastic element and a single frictional element acting in parallel. The use of this model allows the bending deformation to be separated into an elastic and a frictional component, measured by the flexural rigidity and the frictional (or coercive) bending moment, respectively. An expression for the frictional couple in yarn-bending is derived from consideration of the lateral forces acting within the yarn and the degree of set of fibres in a twisted yarn. Bending experiments were made with nylon model plied yarns, conventional multifilament yarns, and staple-fibre yarns; it is shown that the level of residual fibre tension within both unset and set yarns can be estimated from the experimental values of the frictional bending moment by semi-empirical means. The mechanisms of bending for conventional polyester-fibre multifilament and worsted-spun yarns are investigated and the effects of yarn linear density, twist, and yarn-setting treatment studied. The bending behaviour of a series of wool-nylon blended-fibre yarns is also discussed in terms of the simple two-element rheological model of yarn-bending behaviour. It is shown that both the flexural rigidity and the frictional bending moment for the blended-fibre yarns can be calculated by assuming independent behaviour of the fibre during bending.