%0 Journal Article
%T Influence of Adhesive Wear and Thermal Degradation on the Frictional Characteristics of Paper-Based Friction Materials: A Comparative Study
%A Agusmian Partogi Ompusunggu
%A Paul Sas
%A Hendrik Van Brussel
%J ISRN Tribology
%D 2013
%R 10.5402/2013/739202
%X This paper discusses the effects of adhesive wear and thermal degradation on the dry frictional characteristics of paper-based friction materials against steel material. Some commercial paper-based friction materials typically used for clutch applications were subjected to adhesive wear and thermal degradation and the dry frictional characteristics were then measured at different states on a rotational tribometer. The experimental results reveal that both adhesive wear and thermal degradation have opposite effects on the frictional characteristics, where the static and kinetic coefficients of friction increase due to adhesive wear but decrease due to thermal degradation. 1. Introduction Paper-based materials have gained popularity as lining materials of the friction discs of transmission clutches because of their favorable properties such as high coefficient of friction (COF), stable friction characteristics, and low production cost [1, 2]. These materials are porous composites, basically containing some ingredients such as fiber, solid lubricant, and friction modifiers; which are all saturated and cured at certain pressure and temperature, with the thermosetting resin acting as a binder [3]. After the first introduction of paper-based material for automatic transmission clutches, asbestos fibers were widely used as the main ingredient. However, it was found later on that the airborne asbestos fibers can cause serious health problems [5, 6]. As a consequence, the use of the asbestos fiber has been restricted since the 1970. The restriction was first applied in the USA and then across the globe [7]. Nowadays, asbestos fibers are no longer used for paper-based friction materials [8]. In general, the composition of modern paper-based friction materials is visually shown in Figure 1. Figure 1: Schematic composition of a modern paper-based friction material, reproduced from [ 4]. To obtain as high COF as possible, a paper-based material has to be designed with following specifications: (i) sufficiently high porosity and resilience as recommended in [9¨C12] and (ii) plateaued (stratified) surface [13, 14]. Here, a plateaued surface is referred to as a surface having a negatively skewed asperity heights distribution. High porosity implies that the clutch lubricant can flow into the friction materials and expand the sliding area where boundary lubrication is dominant, resulting in a higher kinetic COF . Furthermore, a plateaued surface significantly contributes to larger microcontact area, that is, real contact area, which consequently results in higher static
%U http://www.hindawi.com/journals/isrn.tribology/2013/739202/