"Twist-Controlled" force amplification \& Spinning tension transition in yarn

TL;DR

This paper investigates the transition in twisted yarns from loose fibers to a cohesive structure, revealing a sharp, twist-controlled force amplification mechanism and identifying a critical non-dimensional parameter that governs this transition.

Contribution

The study introduces a mechanical/statistical model explaining the spinning transition in yarns, highlighting the role of a non-dimensional number and demonstrating agreement with experimental data.

Findings

Transition is continuous but very sharp due to frictional force amplification.

A critical non-dimensional number ${ m extbf{H}}$ governs the transition.

Predictions match experimental results on cotton yarns.

Abstract

Combining experiments and numerical simulations with a mechanical/statistical model of twisted yarns, we discuss the spinning transition between a cohesion-less assembly of fibers into a yarn. We show that this transition is continuous but very sharp due to a giant amplification of frictional forces which scales as $\exp \theta ^2$, where $\theta$ is the twist angle. We demonstrate that this transition is controlled solely by a non-dimensional number ${\mathcal{H}}$ involving twist, friction coefficient, and geometric lengths. A critical value of this number ${\mathcal{H}} \simeq 30$ can be linked to a locking of the fibers together as the tensile strength is reached. This critical value imposes that yarns must be very slender structures with a given pitch. It also induces the existence of an optimal yarn radius. Predictions of our theory are successfully compared to yarns made from natural cotton fibers.