Abstract
Friction materials are designed to maintain stable friction level in a wide range of braking conditions and to provide good wear resistance. To achieve these requirements, brake linings are multi-ingredient systems containing more than 10 ingredients categorized as binder, fibers, friction modifiers and fillers. Due to the complexity of such formulation where ingredients act synergically, the understanding of the role of each ingredient is difficult to assess. To get round this difficulty, it is proposed to base the analysis on a simplified formulation containing a reduced number of ingredients. With this aim, a formulation, derived from a manufactured brake lining and composed of six ingredients, has been developed providing friction and wear performances closed to the industrial formulation. Focusing on brass and glass fiber effect, 2 formulations are studied, one of these ingredients been added to the simplified formulation. Addition of brass or glass fiber modifies the microstructure of the composite as well as thermal and mechanical properties. Friction and wear behavior is studied by performing friction tests on a pin-on-disc tribometer. A specific protocol with intermittent contact at constant mean pressure and sliding velocity is performed to reach low, medium and high temperature ranges corresponding to thermal loadings obtained by braking. It is shown that the 3 formulations have closed friction behaviors. Glass fiber reduces pad wear while brass leads to an opposite effect. Analysis of rubbed surfaces shown various friction and wear mechanisms depending on the severity of friction test. Related to brass and glass fiber effect, a better load-bearing capacity is obtained with the formulation with brass while glass fiber impact depends on fiber orientation.
KEYWORDS – simplified brake lining formulation, brass, glass fiber, friction, wear mechanisms