||In the field of friction braking, the regulation objectives in terms of reduction of the environmental impact (noise, pollutant emission) and augmentation of the energy dissipation performances require the understanding of friction phenomena and of friction material choice, especially for brake lining materials. Since the interdiction of asbestos use, new formulations with organic matrix are developed. Their performances have been significantly improved by formulations ever more complex, including several classes of constituents but without a real understanding of each single function. The development of these friction materials is based on an industrial know-how essentially inspired by feedback and trial-error tests leading to the recipe of formulations but without a structure scientific approach of understanding of the role of each constituent, their interactions and their production process. The complexity linked to their composition and production process make though the understanding of link between their heterogeneity and the mechanisms induced by friction.
A simplified formulation is then developed to avoid the complexity of the industrial formulation. The simplified formulation is derivate from an industrial brake lining formulation used on road for heavy vehicle by keeping the preponderant constituents per class (binder, fiber, lubricant, abrasive, friction modifier, and filler); the proportion of these constituents is equal to the percentage of the entire class in the industrial formulation. The tribological behavior the simplified formulation is compared to the industrial one by performing wear tests at various thermal solicitations level and braking tests with single stop or successive deceleration.
This simplified formulation is used, on one hand, to investigate the effect of brass particle and glass fiber when introduced in the formulation. Addition of brass or glass fibres modifies the microstructure of the composite as well as thermal and mechanical properties. During the previous defined wear tests, the simplified formulations and the modified one show closed friction behaviour. Concerning wear rate, the addition of glass fibres reduces par wear while brass has the opposite effect. Surface analyses allow the identification of changes in friction mechanisms induced by the introduction in the formulation of the 2 studied constituents.
On other hand, the simplified formulation is also used to study the influence of hot moulding parameters, duration and temperature, during the production process of the brake lining. After production, the materials are submitted to tomographic analyses to investigate the impact of changes in the process on the microstructure. Focus is made on the fibres distribution and on the interface between rubber particles and the matrix. The materials are then submitted to wear tests to validate the modification in the process parameter (higher temperature and lower duration) by control of wear and tribological behaviour.
||Brake lining, simplified formulation, brass, glass fibres, production process, wear, tribological behavior, tomography