Twist-controlled force amplification and spinning tension transition in yarn.

In this presentation, we will discuss the resistance of a yarn made of twisted fibers to slip-rupture. Combining laboratory experiments, numerical experiments and mechanical models, we will show that the friction forces between fibers increase exponentially along the length of the fiber. The slip-rupture force of a twisted wire ultimately varies as T₀*exp(H) where T₀ is a microscopic force, and H is an adimentional number (called the Hercules number) combining friction and twist. The value of this number determines the twist to be applied to natural fibers to make a yarn of optimum strength. This twist seems to be the one used empirically in the textile industry.