Study of the friction mechanisms of pile surfaces: Measurement conditions and pile surface properties

Pile can be found on different kinds of surfaces on textiles or carpet surfaces for example. This pile exhibits complex contact and friction behaviour. In this study, model surfaces of pile entities produced from PET fibres have been lab-made and their friction behaviour was investigated. The influence of the penetration depth of the slider into the pile, the sliding velocity, the pile density, and the surface tension of the fibre constituting the pile has been studied. The mechanisms involved during friction with a single pile entity-bending in front of the slider and then friction underneath the slider-have been identified and studied. In the first mechanism, pile entity deformation is predominant, and in the second, friction with the slider is significant. In the case of a pile entity assembly, friction also occurs between bristles/loops. The depth penetration into the pile increases the bending contribution. The surface tension of the fibre has a significant influence on fibre-to-fibre friction. The sliding velocity influence comes from both the friction with the slider and between fibres. The coefficient of friction due to the mechanisms underneath the slider is constant whatever the depth of penetration into the pile.