Movement of fibers in assemblies

Previous studies of the mechanics of fiber assemblies have neglected fiber movements that are due to perturbations of the assembly. Axial movements, which are treated in the paper, are important in pilling, bagging, felting, and incremental drafting of yarns in weaving, but lateral movements may also occur. A dynamical model is analogous to molecular statistical mechanics. Both a diffusion model and a driven model are presented. The resistance to movement is due to gripping forces, which may be externally imposed or caused by structural features, such as twist; both are easy to take into account. The geometric forms of entanglements and the way in which they add to frictional resistance are discussed in more detail.