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Friction interaction between brake materials sees a rise in temperatures of over 1000°C contributing to thermal fade of brakes and deterioration/cracking of rotors. Various microstructural features like graphite, ferrite, and pearlite could influence the thermal properties and related friction performance of the brake materials. Even more relevant impact on thermal properties of rotors can be expected after coatings or surface treatments. The primary purpose of this research is to identify the impact of microstructure and surface treatment on the thermal properties of four types of gray cast irons subjected to modified (when compared to their current industrial production) manufacturing processes. These rotors were marked as A (ASTM A48, C30), B (ASTM A48, C20), C (ASTM A48, C30), and D (JIS G5501, FC150), respectively [1, 2].

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.

Copper and copper alloys are widely used in friction materials such as brake pad formulations as one of key ingredients by providing good thermal conductivity and high temperature friction stability to achieve desired friction performance, fade and wear resistance. However, the use of copper or copper containing material is being restricted in brake pads due to environment and health concerns. Extensive works have been made to explore the copper substitutes but most of these efforts became ineffective and failed with issues either thermal fade or excessive pad/rotor wear. In this paper, friction and wear responses were examined when a metallic composite material was used as the copper substitute in NAO and Low-met brake formulations where the copper and copper alloys were added 8% and 22% respectively.

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.

Brake linings have complex microstructure and consist of different components. Fast growing automotive industry requires new brake lining materials to be developed at considerably shorter time periods. The purpose of this research was to generate the knowledge for optimizing of brake friction materials formula with mathematical methods which can result in minimizing the number of experiments/test, saving development time and costs with optimal friction performance of brakes. A combination of processing methods, raw materials and testing supported with the Artificial Neural Network (ANN) and Taguchi design of experiment (DOE) allowed achieving excellent results in a very short time period. Friction performance and wear data from a series of Friction Assessment and Screening Test (FAST) were used to train an artificial neural network, which was used to optimize the formulations. The averaged COF, COF variation and wear were used as the output parameters.

Automotive brake lining materials are complex composites consisting of numerous ingredients allowing for their optimal performance. Since regulations are increasingly limiting Cu content in brake pads and Cu exhibits extremely high thermal conductivity, graphites being excellent heat conducting materials themselves, are often considered for use as potential Cu replacement. This paper surveys the role of two types of carbons (Superior Graphite) with high thermal conductivity but different mechanical properties and morphology: the so-called i) purified flake graphite (PFG) and the ii) resilient graphitic carbon (RGC). A successful “high-end” commercial low-metallic brake pad was re-formulated (SIU Carbondale) by removing of over 20 wt. % of Cu and replacing it with a cocktail of ingredients including 15 wt. % of these two graphite types (RGC and PFG).

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.

This paper discusses the application of an air-coupled ultrasonic non-destructive evaluation (NDE) method for aircraft braking materials. The main objective of this research work was to identify and characterize flaws such as delaminations, cracks, porosity (resin pockets), and disbonds in commercial Carbon/Carbon (C/C) composite aircraft brake disks. Air-coupled ultrasonic testing (ACUT) method was applied for the inspection of commercial C/C brake disks. Several tests were performed by using various air-coupled ultrasonic transducers at center frequencies 50, 120, 125, 225, 400, and 436 kHz in a through-transmission mode by varying scan increments and resolutions. It was found that a testing frequency of 125 kHz provided the best results for commercial C/C composite aircraft brake disks. The relative through-transmitted ultrasonic signal drop in the defect areas was around −18 dB which allowed for easy distinction of abnormal regions within the C/C brake disks.

A number of brake lining materials representative of original equipment in US, Japanese and European automobiles were characterized in order to determine their composition and microstructure. Their frictional performance was subsequently determined using the Friction Assessment and Screening Test (FAST machine). The goal of this work was to identify each constituent of the friction material, to deduce their individual role in the friction process and to determine the effect of the microstructure on the wear properties.