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Besides elimination of copper, the eco-friendly brake materials are developed using geopolymer matrix and natural fibers to replace phenolic resin and synthetic fibers, respectively. The objectives are to diminish i) the amount of volatile organic compounds (VOCs) being released from the brake materials when subjected to temperatures higher than 300 °C; and ii) release the potentially hazardous wear debris particles to the environment. Brake materials were fabricated in university and tested using SAE J2430 test procedure and full scale automotive brake dynamometer (Dyno). Dyno test results indicate that the average friction level of the eco-friendly Cu-free materials (µ ∼ 0.30 to 0.33) was only slightly lower when compared to the baseline material containing Cu (µ ∼ 0.35). All tested materials have passed the Brake Effectiveness Evaluation Procedure (BEEP).

Automotive brake linings are complex composite materials. Some raw materials used by manufacturers or the compounds created during the friction process might be potentially hazardous and may cause various adverse effects. Different fractions of the brake wear debris can be released during braking: i) the airborne and ii) the nonairborne. Due to the small size and minimum gravitational action, the airborne particles could be spread for long distances from a source and typically remain suspended in the air for long periods of time. Our previous research demonstrated that the airborne fraction contains considerable amounts of different nanoparticulates. On the other hand, the emitted nonairborne fraction typically settles on vehicle/brake hardware surfaces and in the vicinity of roads. The nonairborne particles are considered to be relatively large, but it was shown that nano-sized particles readily attach to them and can be released later.

Particulate air pollution from road traffic currently represents significant environmental and health issue. Attention is also paid to the “non-exhaust pollution sources,” which includes brake wear debris. During each brake application, the airborne and nonairborne particles are emitted into the environment due to wear. High temperatures and pressures on the friction surfaces initiate chemical and morphological changes of the initial components of brake pads and rotating counterparts. Understanding of impact of matter released from brakes on health is vital. Numerous studies clearly demonstrated that particulate matter caused potential adverse effects related to cytotoxicity, oxidative stress, stimulation of proinflammatory factors, and mutagenicity on the cellular level. This paper compiles our main results in the field of genotoxicity, immunotoxicity, and aquatic toxicity of airborne brake wear particles. The brake wear particles were generated using an automotive brake dynamometer.

The goal of this paper is to delineate recent experimental evidence that the presence of conforming surface wear groove tends to stabilize the vibration and noise response of aircraft brakes. This finding is consistent with an earlier theoretical study in which the contact between Carbon-Carbon (C/C) composite brake disks was assumed to be visco-elastic and through this assumption it was found that the existence of conforming grooves results in increasing dynamic stability of brake disk interaction. Therefore, the presumption of visco-elastic contact for C/C brakes seems to agree with the experimental observation in a subscale dynamometer. The present paper summarizes both theoretical analysis and the test results. In the tests C/C composites were heat treated for one hour at temperatures 1800°C and 2400°C, respectively. They were then subjected to frictional tests in a subscale aircraft brake dynamometer at 50 % relative humidity (RH) level.

The brake wear contribution to the environmental pollution has been extensively discussed, with major focus on asbestos and heavy metals released to the environment. Only limited attention was paid to released organic compounds generated during friction processes, although the organic and carbonaceous components are not the minor part in brake lining formulations. Friction processes in brakes are associated with relatively high temperatures and high pressures on the friction surfaces which relates to the thermal decomposition of the organic components in friction materials and to brake lining thermal fade. Thus, this study focuses on the identification of organic compounds released from a model low metallic brake material.