Brake is a necessary part in any vehicle. In general, the essential break pad attributes are low compressibility, good resistance to severe temperatures, and good resistance to abrasion. The constituents of the brake pads should guarantee the required properties of the frictional material in the braking systems. The constituents of a brake pad are divided into following categories: binder, reinforcing elements, fibers, abrasive elements, fillers, solid lubricants, fireproofing substances. Any change in the design or applied material for the brake pad must fulfill the necessary technical requirements defined by the automotive standards (e.g. SAE standards and trend to manufacture lighter vehicle) and brake functions.
Pressure, contacting temperature, and sliding velocity are the three critical factors that affect friction and wear performances for brake pad material. In addition to the friction wear, adhesive interaction between moving and fixed parts may raise the adhesive wear at the pads’ surfaces. Contribution of the friction force and the consequence pressure with low cycle (plastic) fatigue and tear (cracking) processes accumulate stresses at the tips or/and critical points of the friction surface up to the level of shear strength of the detachment of the material, which results in formation of tribo-layer and incorporation of material into transfer-films. The subsequence friction forces crash the transfer-films and release the lamellar fragments of these films. Thereof, three-body abrasion is formed abruptly by which increases the applied pressure on the brake frictional surfaces. The additional pressure increases the wear rate by compressing the tribofilms in more compact volume. The condition of the three-body abrasion shatters some of small plateaus formed by the hard ceramic and fills a portion of the grooves from two-body abrasion status with the tribofilms. Furthermore, tribochemical reaction may take place in the brake containing metal fibers or particles with oxidation tendency during friction material in service. Thereby, three-body abrasion generates noise, vibration, and instability in friction coefficient and braking-temperature. A portion of the brake dust may airborne and some other portion may be deposited on the brake hardware.
The proposed pads optimize the wear rate due to tribofilms by:
(a) equipping the frictional surfaces with blower to lower the wear raised by the remained debris from previous brake events. A set of blower may also be designed as air channels within the pad.
(b) fabricating of pads composed of reinforced aluminum matrix composite with hard SiC and nanotube carbon particles to maintain the coefficient of friction. Such pad’s material is fabricated by powder technology technique with well-defined and manageable manufacturing technology to ensure the homogeneity and anisotropic properties of the pads.
The proposed brake pads ameliorates the necessary brake pad properties, particularly, sufficient coefficient of friction force during braking, stability of friction coefficient and actuating temperature, adequate mechanical and thermal strength, longer lifetime and durability, reducing noise and vibration at friction zone, manageable manufacturing technology, ability to regenerate friction with the same condition. Consequently, the proposed pad has desirable cost effect (especially for air-brake systems) in long-term application and improving safety issues in vehicles’ brake.