Morphological and structural features affecting the friction properties of carbon materials for brake pads (original) (raw)

Characterization of brake pad friction materials

Due to health-related problems as well as the requirements for better quality products, many material formulations for high performance asbestos-free materials are being introduced in Light Rail Transit (LRT) brake pads. This paper reports four new formulations of brake friction materials, which are made using the following ingredients: Resin, Iron oxide, Steel fiber, Ceramic fiber, Organic fiber, Magnesium Oxide, Aluminium Oxide, Barium, Sulphur, Graphite, Rubber, Novacite, Nipol and friction dust. Values of Hardness, Specific Gravity and Transverse Rupture strengths of these formulations are reported. The friction and wear test results of these formulations viz., A, B, C and D are included. The effects of physical properties, mechanical properties and morphology of the formulations on their friction and wear behavior are discussed. Scanning Electron Micrographs (SEM) and EDAX analysis of a formulation is included. It is found from the analysis that formulation B possesses better friction and wear properties compared to the other three formulations.

Review of automotive brake friction materials

The gradual phasing-out of asbestos in automotive brake friction materials in many parts of the world has sparked the onset of extensive research and development into safer alternatives. As a result, the brake friction industry has seen the birth of different brake pads and shoes in the past decade, each with their own unique composition, yet performing the very same task and claiming to be better than others. This suggests that the selection of brake friction materials is based more on tradition and experimental trial and error rather than fundamental understanding. This review strives to eliminate the cloud of uncertainty by providing an insight into the pros and cons of the common ingredients and make-up used in contemporary dry and wet friction pads and shoes. In this paper typical brake materials are reviewed and their advantages and disadvantages in contemporary brake applications are discussed.

Characterization of surface morphology and its correlation with friction performance of brake pads

International Journal Sustainable Construction & Design, 2015

The present work presents the morphology evolution of a brake material surface submitted to braking tests through a laboratory-scale tribometer. Optical microscope images of the material’s surface were obtained for every 10 braking operations. These images were post-processed in appropriate computational software. By means of the image segmentation technique, morphological parameters related to the brake material surface were estimated. The wear rate and also the coefficient of friction resulting from the tests were measured. For the NAO material used in this study, the friction behaviour revealed to be strongly associated with the amount of contact plateaus. Besides, the mean area of the contact plateaus was the main factor responsible for increasing the real contact area of the friction material. The higher wear rate observed in the first braking operations can be mainly attributed to the higher surface roughness measured in this condition. As the braking operations progress, the ...

Friction and wear behavior of carbon fiber reinforced brake materials

Frontiers of Materials Science in China, 2009

A new composite brake material was fabricated with metallic powders, barium sulphate and modified phenolic resin as the matrix and carbon fiber as the reinforced material. The friction, wear and fade characteristics of this composite were determined using a D-MS friction material testing machine. The surface structure of carbon fiber reinforced friction materials was analyzed by scanning electronic microscopy (SEM). Glass fiberreinforced and asbestos fiber-reinforced composites with the same matrix were also fabricated for comparison. The carbon fiber-reinforced friction materials (CFRFM) shows lower wear rate than those of glass fiber- and asbestos fiber-reinforced composites in the temperature range of 100°C-300°C. It is interesting that the frictional coefficient of the carbon fiber-reinforced friction materials increases as frictional temperature increases from 100°C to 300°C, while the frictional coefficients of the other two composites decrease during the increasing temperatures. Based on the SEM observation, the wear mechanism of CFRFM at low temperatures included fiber thinning and pull-out. At high temperature, the phenolic matrix was degraded and more pull-out enhanced fiber was demonstrated. The properties of carbon fiber may be the main reason that the CFRFM possess excellent tribological performances.

Development of Brake Friction Material for Automotive Application

Zenodo (CERN European Organization for Nuclear Research), 2023

Brakes in any automobile are intended to regulate and stop the moving vehicles safely. The overall braking efficacy depends on various components, their ability to convert kinetic energy to heat energy through friction (b/w pad and drum). Therefore, the pad material properties are of significance, to name a few, clothing forfeiture, coefficient of friction (COF), wear and mechanical behaviour. Normally, Phenol formaldehyde (PF) / Epoxy resin (ER) and some fibre materials along with glass, asbestos and carbon fibres in proper proportions are preferred. Whereas, asbestos is readily available in the market and regularly used. But, this asbestos is toxic in nature and there is every need to explore alternatives. An endeavour made to substitute this asbestos with materials like glass fibre (GF), carbon fibre (CF) coconut casing powder (CSP) etc. which are eco-friendly. Also, inorganic materials likeBaSO4-barium sulphate and CaCO3calcium carbonate are explored as well in terms of filler followed by aluminium

Characterization of Friction Material Formulations for Brake Pads

World Congress on Engineering, 2007

New friction material formulations are compared with a commercial brake friction material used in Light Rail Transit (LRT) operating in Malaysia. Characterization techniques such as SEM, TGA, XRD, friction and wear tests are used to characterize the formulations as well as the commercial material. Out of the 30 formulations made, two formulations viz., S1 and S2 closer to commercial material are presented in this work. Formulation S2 exhibits better thermal stability and better wear resistance. With the help of SEM analysis, physical properties and XRD spectrum analysis, it is shown that formulation S2 has same crystallinity as the commercial specimen and can be considered for replacing the commercial material in LRT brake pad applications. The cost of the brake pad would reduce by half if they are made locally in Malaysia.

Advanced Friction-Wear Behavior of Organic Brake Pads Using a Newly Developed System

2018

The objective of this study was to investigate the influence of an advanced performance system on the tribological behavior of brake pad material using a specially designed brake pad tester system following standard SAE J-661. The tribological behavior and friction and wear characteristics of the organic brake pad samples were evaluated. During braking tests, the samples, in contact with a cast iron disk, were studied at different disc speeds, temperatures, and braking cycles under a constant pressure. In order to understand the friction and wear behavior, the unworn surfaces, worn surfaces, and wear debris were characterized by means of scanning electron microscopy (SEM) and energydispersive X-ray (EDX). Furthermore, the surface characteristics and differences in the wear modes of the brake pad samples were examined. Wear debris was permitted to deform the brake pad surfaces, leading to friction layers and enabling the estimation of the friction behavior of the brake pads. The results showed that the best friction-wear behavior was obtained with lower braking cycles at low speeds and temperature. Thus, the newly developed brake pad tester system proved very effective in evaluating the performance of the brake pad samples.

Chemical and microstructural changes induced by friction and wear of brakes

Wear, 2001

The chemical and microstructural changes occurring during braking simulation tests at the surface of a conventional brake pad material were investigated mainly by scanning and transmission electron microscopy and surface analytical techniques. It can be shown that patches of a third body material develop, comprising a compositional mix of all constituents of the pad and iron oxides from the disk. Milled debris particles still have the crystal structure of barite, the major phase of the pad material, but the grain size is reduced drastically to the nanometer scale. The major wear mechanism is delamination of filler particles from the organic binder, supported by local degradation of the phenolic resin during asperity heating. Quartz crystals are preserved thereby adopting the function of primary contact areas.