Tribology of Sized Glass Fibers Part II: Using an Electronic Microbalance Technique to Study Stick-Slip Behavior

Abstract

This part of the series presents an analysis of stick-slip motion during sliding of two crossed, sized, glass fibers on the basis of experiments with an electronic microbalance as described in Part I. The vertical movement of a fixed horizontal fiber generates a discontinuous or stick-slip motion of the vertical fiber linked to the microbalance. A large number of friction measurements are stored and then interpreted by a computer program. While Part I showed that friction force values are correlated to those measured by lateral force microscopy, this paper seeks a better understanding of stick-slip: static friction forces, as well as their amplitude and frequency, and the effects produced by changes in the sliding velocity and applied load. Results show that static friction coefficient values do not vary considerably with increasing speeds, but these values increase drastically when the load is decreased. Whatever the conditions, the amplitude of the stick phases is related to cohesive forces between filaments, which can be evaluated by “pull-off” experiments, and each stick amplitude is proportional to its duration such that the slope of the stick is always constant. This stick slope depends on the nature of the sizing, the applied load, and the sliding velocity. Variation of work done during decohesion with the sliding speed is attributed to viscoelastic effects.