Friction in Fibrous Materials

Abstract

The classical laws of friction adequately describe the behavior of materials that deform plastically but fail to do so in fibers that deform viscoelastically. This paper presents a structural model that characterizes friction in fibrous materials. The theory is general and can account for the behavior of a wide range of materials. The model provides a theoretical base for the empirical equation F = aNⁿ, which has been fitted successfully to experimental data from previous investigations. It gives theoretical meaning to the indices a and n, which heretofore were empirical constants, and brings out the factors, structural as well as procedural, that affect their values. The factors affecting friction in fibers are shown to fall in two main groups, one governing the morphology of contact and the other the mechanical properties of the junctions. A detailed discussion of these factors is given in this paper. The results of an experimental investigation, where acrylic and polypropylene yarns varying systematically in structure were the materials, will be submitted for publication later. Friction is measured in dry and wet media using both line and point contact methods. The effects of structural factors are examined and interpreted in light of the model.