Brake Materials Research Articles

Copper-Free Resin-Based Braking Materials: A New Approach for Substituting Copper with Fly-Ash Cenospheres in Composites

Copper particles emitted from braking have become a significant source of environmental pollution. However, copper plays a crucial role in resin-based braking materials. Developing high-performance braking materials without copper has become a significant challenge. In this paper, the resin-based braking materials were filled with fly-ash cenospheres to develop copper-free braking materials. The effects of fly-ash cenospheres on the physical properties, mechanical and friction and wear properties of braking materials were studied. Furthermore, the wear mechanism of copper-free resin-based braking materials filled with fly-ash cenospheres was discussed. The results indicate that the inclusion of fly-ash cenospheres in the braking materials improved their thermal stability, hardness and impact strength, reduced their density, effectively increased the friction coefficient at medium and high temperatures, and enhanced the heat-fade resistance of the braking materials. The inclusion of fly-ash cenospheres contributed to the formation of surface friction film during the friction process of the braking materials, and facilitated the transition of form from abrasive wear to adhesive wear. At 100–350 ℃, the friction coefficient of the optimal formulation is in the range of 0.57–0.61, and the wear rate is in the range (0.29–0.65) × 10−7 cm3·N−1·m−1, demonstrating excellent resistance to heat-fade and stability in friction coefficient. This research proposes the use of fly-ash cenospheres as a substitute for environmentally harmful and expensive copper in brake materials, which not only improves the performance of braking materials but also reduces their costs.

Green composite friction materials: A review of a new generation of eco-friendly brake materials for sustainability

Particulate matter (PM) still poses a significant threat leading to air pollution which is responsible for continued damage to human health and the environment. Particulate matter resulting from non-exhaust emissions are considered as viable a source comes mostly from brake pad wear concept. The scientific challenge of this work is to stimulate a new generation of green friction materials to reduce particle emissions having low-environmental impact. The specificity of braking materials, their effects on the environment and human health are studied. To minimize the levels of air pollution, the use of green friction composites collected from natural elements reducing human diseases is discussed. For this purpose, the novel and high-performance friction composite materials synthesized from vegetable and animal waste used as a raw material are reported. The natural powder and fiber treatments, the optimum formulation and the binder materials related to the green friction composites are reviewed. An overview of environmentally ecofriendly green friction materials embedded by reinforcing phases of natural elements exhibiting excellent mechanical and tribological properties are mentioned. Therefore, scientific and industrial efforts should concentrate on the development of green friction materials to minimize the effect of transport related air pollution.

Study on Effect of Heat Treatment on C/C-SiC Brake Performance

After powder metallurgy and carbon/carbon brake materials, carbon-ceramic brake material (C/C-SiC) is a new generation of braking material. There are currently some batches of brake materials whose friction performance could be better: slightly higher than the standard. SiC was introduced into the C/C-SiC brake disc through Polymer Impregnation and Pyrolysis (PIP), and the composition and friction-wear performance C/C-SiC-SiCp were investigated. The findings indicate that the SiC introduced by PIP is amorphous, existing in the material’s pores, and the porosity is reduced to 7%. With the increase in speed, The C/C-SiC-SiCp braking curve demonstrates a transition from inverted trapezoidal to saddle-shaped. The line wear rate is reduced by 0.6 μm/cycle at medium and high speeds compared with C/C-SiC.

Study on the Influence of Friction and Wear Properties of High-Speed Rail Brake Materials under Humidity Environment and Temperature Conditions

A multi-functional friction and wear testing machine was used to test the pin disk wear of high-speed railway brake friction material under different disk temperatures (20 °C, 100 °C, and 200 °C) and different ambient humidities (55%, 95%). The test results show that the change in the disk temperature and different ambient humidities have significant effects on the frictional wear performance of the high-speed railway brake material. Under the conditions of 20 °C, 100 °C and 200 °C, the instantaneous friction coefficient and wear rate of the brake material decreased as the ambient humidity increased. The different ambient humidity caused severe surface damage to the brake materials, but the damage mechanisms were dramatically different. At constant temperature, the higher the ambient humidity, the lower the maximum equilibrium temperature of the disc.

Study on the Wear Performance of Brake Materials for High-Speed Railway with Intermittent Braking under Low-Temperature Environment Conditions.

The pin on the disc friction tester was used to conduct the intermittent braking testing of train brake materials with a low-temperature environment simulation device at temperatures 20 °C, 0 °C, -10 °C, -20 °C, and -30 °C. The results show that intermittent braking presents different wear characteristics of braking materials at low temperatures. Under different ambient temperature conditions, the most volatile friction coefficient caused by intermittent braking happens at 0 °C, and the wear rate of brake materials reaches its maximum at 0 °C. The wear surface morphology of the brake pad material mainly includes scratches, furrows, adhesions, and abscission pits, while the surface of the brake disc material was dominated by scratches, furrows, and adhesions. With the decrease in temperature, the adhesion damage of the brake pad/disc material increases. At 0 °C, the brake pad material has crack damage.

Comparative Study on Thermal Analysis of Disc Brake Using ANSYS Simulation

The objective of this paper is to find a suitable material for disc brakes that can dissipate heat very fast to the environment than others. They are subjected to wear and tear, which might have an impact on their performance. The simulation findings will help us figure out the temperature, pressure, and heat that can be withstand at its maximum. If it manages to dissipate heat properly it can avoid the distortion, which will be produced in the disc, which leads to thermal cracking of the disc leading to disc failure. To eliminate such flaws, we need to develop a disc brake material that can endure a specific level of heat and friction while maintaining its efficiency over time. In this work, 3 different disc brake materials, namely Al356, cast iron, and SS420, are chosen for thermal analysis by using ANSYS simulations and the results will be compared among.

Effective Anti-Oxidation Repair Coating for C/C Brake Materials Comprising Lead-Borosilicate and Bismuth-Borosilicate Glass

To achieve effective antioxidation of on-site repair coating for C/C brake materials in the full temperature range (500–900 °C), lead glass and bismuth glass were introduced into the borosilicate glass to acquire the protective coatings. Before preparing coating samples, the thermal gravity characteristics of the lead/bismuth–borosilicate glass powders were analyzed by TG/DSC. The results revealed that the temperature at which weight gain begins was 495 °C and 545 °C, respectively. The oxidation behaviors of the lead- and bismuth-modified borosilicate glass coatings were compared at 500 °C, and the antioxidation properties of the former were further examined from 500 to 900 °C. The oxidation results indicated that mixing lead glass with borosilicate glass realized effective oxidation resistance in the full temperature range. With a lead content of 20%, the lead–borosilicate glass coating was able to protect C/C substrates from oxidation. The corresponding weight loss of the lead-glass-coated samples was −1.89% when oxidized at 500 °C for 10 h, while the weight loss was −2.55% when further oxidized at 900 °C for 10 h. However, mixing bismuth glass with borosilicate glass was difficult to achieve the oxidation resistance of the coating at 500 °C due to the significant phase separation.

Evolution of contact surface characteristics and tribological properties of a copper-based sintered material during high-energy braking

A plethora of difficulties may appear with brake materials during braking with high-energy dissipation. The tribological properties of a copper-based sintered material for high-energy brakes at different levels of braking energy ranging from 3010 to 31,789 J/cm2 were experimentally evaluated using a reduced-scale dynamometer. Morphological analysis of worn surfaces and wear debris analysis were conducted using scanning electron microscope and three-dimensional video microscope, respectively. Friction and wear behaviour of the copper-based sintered material depended strongly on the contact surface characteristics, being controlled by the dissipation of braking energy. The worn surfaces with low roughness, well-covered by the tribo-films, contributed to the low and stable friction coefficient. Additionally, examination and analysis of worn surfaces and wear debris corroborated the wear mechanisms of the copper-based sintered material. Severe adhesive wear and delamination wear occurred during high-energy braking.

Tribology and Airborne Particle Emission of Laser-Cladded Fe-Based Coatings versus Non-Asbestos Organic and Low-Metallic Brake Materials

Laser cladding is a promising surface treatment for refurbishing worn-out cast-iron brake rotors. Previous studies on laser-cladded brake rotors have demonstrated their extensively higher wear and greater airborne particle emissions, compared with traditional cast iron rotors. In order to overcome this, a commercial non-asbestos organic (NAO) brake material is tested against Fe-based laser-cladded and traditional cast-iron brake rotors. Two low-metallic brake pad materials are also tested as references. The materials’ coefficients of friction, specific wear rates and particle number concentrations are evaluated. The results indicate that the NAO brake material showed lower wear and had fewer particle emissions than the low-metallic brake materials when deployed against both cast iron and laser-cladded brake rotors. The NAO/laser-cladding friction pairing showed wear, particle concentration and fraction of fine particles (sub 1 μm) equivalent to those of the low-metallic/cast-iron friction pairing, creating significant potential for application in refurbishing worn-out cast-iron brake rotors.

Effect of Nano Sodium Titanate Whisker and Aramid Pulp on the Friction and Wear Behavior of Resin-Based Brake Material

The dependence of friction and wear behavior on nanosodium titanate whisker and aramid pulp in a designed resin-based brake material was systematically analyzed. Higher contents of aramid pulp enhanced the hardness of the brake materials. In addition, the maximum impact energy of the material reached 0.392 J/cm2 where the ratio of aramid pulp to sodium titanate whisker is 0.75. At same time, the friction coefficient was stable between 0.38 and 0.45, and the wear rate was 5%. The samples with higher contents of nanosodium titanate whiskers and aramid pulp showed more uniform furrows, fewer delaminated craters, more moderate layers transfer and more stable contact plateaus.

Frictional and Lubricating Materials with Mineral Components

The results of the tribotechnical studies on frictional materials and lubricating composites in Armenia are presented. The characteristics of developed braking materials, antifriction polymeric composites, and lubricants are given. Recommendations on designing machine parts made of antifriction and friction composites based on polymers, as well as lubricants for friction units using local raw materials and minerals, are developed. Main regularities in the friction and wear of the surface layers of antifriction and friction composites materials are revealed. Environmentally safe and efficient brake materials for motor cars and railroad vehicles are presented. Self-lubricating materials for sliding bearings and novel additives for lubricants have been proposed for industry.

Effect of Brake Parameters on Friction Properties of Brake Materials in Low Temperature Environment

Effect of Brake Parameters on Friction Properties of Brake Materials in Low Temperature Environment

Comparison of tribology performance, particle emissions and brake squeal noise between Cu-containing and Cu-free brake materials

The present study developed two Cu-free brake materials using carbon fiber or carbon nanotube as the replacements for copper fiber and evaluated their tribology performance, particle emissions and brake squeal noise. Results show that the coefficients of friction (COFs) of the Cu-free brake materials are lower than that of Cu-containing brake material at the braking conditions with low and medium loads. At the high load braking condition, all the braking materials exhibit comparable COFs. Cu-free brake materials present larger specific wear rates than the Cu-containing brake material. However, the application of carbon fiber can reduce the particle number emission. All brake materials exhibit comparable brake squeal noise.

Experimental Characterization Protocols for Wear Products from Disc Brake Materials

The increasing interest in the emission from the disc brake system poses new challenges for the characterization approaches used to investigate the particles emitted from the wearing out of the relevant tribological systems. This interest stems from different factors. In the first place, a thorough characterization of brake wear particles is important for a complete understanding of the active tribological mechanisms, under different testing and servicing conditions. This information is an important prerequisite not only for the general improvement of brake systems, but also to guide the development of new materials for discs and brake pads, responding better to the specific requirements, including not only performance, but also the emission behavior. In this review paper, the main material characterization protocols used for the analyses of the brake wear products, with particular regard for the airborne fraction, are presented. Reliable results require investigating the fine and ultrafine particles as concerns their composition together with their structural and microstructural aspects. For this reason, in general, multi-analytical protocols are very much recommended.

Effect of Nano Sodium Titanate/ Potassium Titanate Whisker on Tribology Behavior of Brake Materials

Here we developed a hot-pressed molded resin-based brake pad material reinforced by a nano sodium titanate whisker in comparison with nano potassium titanate whisker. The effect of the whiskers on the tribology behavior was investigated. Though nano sodium titanate whisker reinforced brake material showed higher porosity (+12.29% averagely) and lower hardness (-25.8% averagely) caused by the impurities, it exhibited improved ability in stabilizing the friction coefficient and enhancing 25.5%, 31.1%, 25.9% higher wear resistance, when the volume contents of whisker are 7.5%, 15% and 22.5%, respectively, compared to the nano potassium titanate whisker reinforced brake material. The wear mechanisms of the nano sodium titanate whisker reinforced brake materials were determined as embedded debris, delaminated crater, moderate layers transfer, uniform furrows, primary plateaus and secondary plateaus in similar size, indicating a main wear form of abrasive wear instead of adhesive wear.

Resin Matrix Brake Materials Reinforced by Nano-Al2O3 for Mining Equipment

To verify the effect of Al2O3 particle content and size as an abrasive on resin matrix friction materials for mining equipment, the tribological performance of friction materials was studied by using a blockon- ring tribotester over a wide range of applied load and sliding speed. The testing conditions simulated brake conditions of mining equipment. The antiwear property of nano-Al2O3 was superior to that of micro- Al2O3 for friction materials. The friction coefficients of specimens increased with the increase of nano-Al2O3 content. The wear rates decreased with increasing nano-Al2O3 content. The wear rates of specimens containing nano-Al2O3 was about 2–8 times lower than that of specimen with micro-Al2O3. The specimen with 10.5 vol% nano-Al2O3 showed the best tribological properties. The wear mechanism of specimens with nano-Al2O3 was abrasive wear and plastic deformation.

A Comparative Thermal and Structural Analysis of Different Disc Brake Materials

A Comparative Thermal and Structural Analysis of Different Disc Brake Materials

Effect of Braking Speed on Frictional Properties of Short Fiber C/C-SiC Brake Materials and Grey Cast Iron

Short fiber C/C-SiC brake materials were prepared by dipping the fibers in resin, chopping, warm pressing, and pyrolyzing, followed by a liquid silicon infiltration process. The effect of braking speed (initial braking speed) on the frictional properties of a pair of short fiber C/C-SiC brake materials and grey cast iron (HT250) (C/C-SiC-HT250) was investigated. The results indicated that the average friction coefficient of the C/C-SiC-HT250 increased to the maximum value at 10 m/s and then decreased with an increase in braking speed. The wear rate of the C/C-SiC increased with increasing braking speed when it was lower than 10 m/s and decreased when it was higher than 10 m/s. The wear was the result of the brittle fracture of asperities when the braking speed was lower than 10 m/s and induced granular debris. The wear for the tough cutting by C/C-SiC asperities or hard phase when the braking speed was higher than 10 m/s and resulted in ribbon debris. When the braking speed was higher than 20 m/s, the texture of the friction surface of the HT250 changed, which would affect the tribological properties.

Effects of Carbon Fiber Dispersion on Bending Property of Cf/SiC Brake Materials

With increasing of the speed of the train, the requirement of the performance of the braking friction materials is more and more higher. It is urgent to find new braking materials to satisfy the rigorous using environment. Cf/SiC has the broad application prospects when it is used as a new kind of braking material. On this article, in order to shorten preparation cycle and reduced production costs, short carbon fiber is substituted continuous carbon fiber felt. Cf/SiC brake materials were prepared by the way of molding compression-pressureless sintering with resin binder. The effect of short carbon fiber dispersion on bending properties of brake materials was researched. The experimental results show that the bending strength of Cf/SiC brake materials, which manufactured by dispersing short carbon fibers, is higher than the composites manufactured by using fiber bundle. When the distribution of carbon fiber in composites is in single fiber state, the interfacial strength between carbon fibers and matrix were increased. At the experimental condition, compared to the sample with fiber bundle, the bending strength of the specimen with dispersed fiber is increased 40.79%. The toughening mechanism of carbon fiber debonding and fiber pull were generated in the process of bending fracture. The fracture model of composites is pseudo-ductile type.

A Pin-on-Disc Study Focusing on How Different Load Levels Affect the Concentration and Size Distribution of Airborne Wear Particles from the Disc Brake Materials

Airborne wear particles originating from disc brakes are one important contributor to the concentration of airborne particles in urban environments. It is therefore of interest to improve the knowledge of these particles. The purpose of this article is to investigate the concentration and size distribution of the airborne wear particles generated from the contact between a low-metallic pad material and a grey cast iron disc at different load levels. This is done on model level with a pin-on-disc machine that allows the cleanliness of the air surrounding the test specimens to be controlled, and thus the airborne portion of the wear particles to be studied separately. The concentration and size of airborne wear particles were measured online during testing with four particle instruments. In addition, airborne wear particles were collected on filters during the tests and afterward analysed using SEM. Trimodal size distributions with peaks around 280, 350 and 550 nm were registered during running-in for all load levels. After running-in bimodal size distributions with peaks around 350 and 550 nm were registered for all load levels with the exception of the highest load level where multimodal size distributions were registered. At the two highest load levels the concentration of ultrafine/fine particles showed an increase up to a factor hundred indicating a change in wear mechanism. SEM images show ultrafine, fine and coarse airborne wear particles.