Comparative Study of Friction and Wear of Two Generation of CVI CC Composite (original) (raw)
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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.
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Carbon, 2009
Carbon/Carbon disks worn by a reduced scale braking test were characterised by an experimental set-up allowing the analysis of the whole disk. In this way, the structure and the surface chemistry of the wear debris formed during the braking and trapped at the sliding interface were determined. The evolution of the surface chemistry and the structure during rubbing at different braking energies were studied by temperature programmed desorption with mass spectrometry analysis and by measuring the active surface area. The analysis of the composites before and after rubbing highlights the formation of highly disordered and oxygen-rich carbon wear debris at the sliding surface. The surface chemistry of the carbon dust trapped on the disk surface was found to be very similar to that of the wear debris ejected during braking. From this similarity a rough estimation of the amounts of carbon dust lying on the worn composites surface was made. (C. Vix-Guterl). C A R B O N 4 7 ( 2 0 0 9 ) 8 5 -9 3 a v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / c a r b o n
Influence of thermal properties on friction performance of carbon composites
Carbon, 2001
Three different needled felt C / C composites containing from 5 to 25% fiber oriented normal to the friction surface (z-fiber) were evaluated and tested for friction performance. A laboratory dynamometer was used to simulate cold taxi, hot taxi and normal landing braking events utilizing a single stator and rotor pair. Temperatures measured near the friction surface were lowest for highest thermal diffusivity material demonstrating the effectiveness of z-fiber content at reducing friction surface temperature. Low friction coefficient (|0.12) under cold taxi conditions increased by a factor of two under hot taxi conditions due to water-desorption transitions. Composites with high diffusivity needed greater braking power to experience transition relative to lower diffusivity materials. Higher braking power was needed to produce a transition under higher humidity conditions. Highest z-fiber content discs showed the lowest wear rate which was attributed to higher in-plane shear strength. The wear rate was highest under hot taxi conditions and it was concluded that mechanisms other than oxidation loss were primarily responsible for the wear rate of the C / C composites tested in this study. The C / C composite surfaces had a polished appearance suggesting that the removal of nano-scale particles occurs from the friction process.
Effect of Type of Carbon Matrix on Tribological Properties of C C Aircraft Brake Discs
Defence Science Journal, 2019
Four type of Carbon/Carbon (C/C) composite brake discs (A, B, C, D) were manufactured using different process routes, using spun yarn graphitised carbon fabric as reinforcement. These discs were densified with different types of carbon matrices derived from different precursor materials. C/C brake disc of type A is having carbon matrix derived from pitch precursor, type B has a mixture of resin and pitch derived carbon matrices, type C has a combination of resin derived, pyro and pitch derived carbons and type D has pyro and pitch derived carbon matrices. Friction and wear performance of these brake discs were studied by simulating aircraft landing braking energies (normal and over load) corresponding to one interface using disc-on-disc dynamometer. It was found that the type of carbon matrix influences the nature of friction film formed, which in turn affects the wear rate of C/C brake discs. It was also discussed how the matrix characteristics affected the mechanical properties and the friction film formed affect the coefficient of friction of each type of disc.
Wear, 2009
Due to their thermo-mechanical performances maintained at high temperature, C/C composites demonstrate their advantages in high energy aeronautical braking. During friction a typical tribological behavior was observed. At first, an abrupt transition of friction coefficient takes place systematically from a weak value (∼0.15) to a high value (∼0.35). Before this transition, an extremely weak wear rate is associated to a weak friction coefficient value and no gas exchanges occur in the contact, this regime being called non-reactive. From the abrupt transition, a very high wear rate and strong gas exchanges associated to the high friction value occur (reactive regime). In this paper, for a better understanding of the mechanisms governing the abrupt transition during C/C composites tribological, mechanical, thermal and physicochemical data are analyzed. Friction tests are performed on a 3D C/C composite consisting of PAN-based fibers and CVI pyrocarbon matrix in using a pin-on-disc tribometer equipped with a mass spectrometer allowing the in situ gas exchange analysis (CO 2 production, O 2 consumption) in the contact. To follow the disc surface temperature evolution before, during and after the transition, a thermal infrared camera is used. After friction, worn surfaces and interfaces are characterized by optical microscopy and scanning electron microscopy. In a final analysis, a mechanism is proposed to explain the abrupt transition.
Tribology International, 2019
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Journal of Egyptian Society of Tribology, 2023
Aircraft brakes are very critical for its safe operation. During landing, the brakes takes 40% of the energy while aerodynamic brakes, reverses thrust and rolling friction takes the rest of energy, [1]. Thus superior tribological behavior at high temperatures is required to carry out this mission. Carbon fiber reinforced Carbon(C/C) composites have outstanding low density and high thermomecanical properties, [2]. For these reasons, more aircraft manufacturers convert to C/C brakes. The tribological behavior of C/C composites is examined in this paper by exploring the parameters that affect weight loss. The Taguchi method is used to conduct a design of experiment (DOE) to optimize the experiments size. The response surface methodology is utilized to ascertain the most favorable blend of process operating parameters. The Carbon/Carbon composite's wear and friction characteristics were evaluated using a dry sliding wear test, employing the disc-ondisc method. The findings revealed that the duration of contact between the stator and rotor discs was the most significant contributor to weight loss, followed by the applied load and rotational speed. The most predominant factor was the braking pressure then the time and vehicle speed. KEYWORDS Carbon/carbon composites, taguchi method, analysis of variances, carbon/carbon tribology.
The Influence of Carbon Fiber Heat Treatment Temperature on Carbon-Carbon Brakes Characteristics
Carbon letters, 2013
The effects of heat treatment temperature (HTT) of polyacrylonitrile-based carbon fiber (CF) on the mechanical, thermal, and tribological properties of C/C composites were investigated. It was found that HTT (graphitization) of CF affects the thermal conductivity and mechanical and tribological characteristics of C/C composites. Thermal treatment of fibers at temperatures up to 2800°C led to a decrease of the wear rate and the friction coefficient of C/C composite-based discs from 7.0 to 1.1 μm/stop and from 0.356 to 0.269, respectively. The friction surface morphology and friction mechanism strongly depended on the mechanical properties of the CFs. The relief of the friction surface of composites based on CFs with final graphitization was also modified, compared to that of composites based on initial fibers. This phenomenon could be explained by modification of the abrasive wear resistance of reinforcement fibers and consequently modification of the friction and wearing properties of composites. Correlation of the graphitization temperature with the increased flexural and compressive strength, apparent density, and thermal conductivity of the composites was also demonstrated.
Numerical Simulation of Wear in Aircraft Carbon-Carbon Composite Disk Brake
Journal of Engineering and Science Research
Friction and wear are two major factors affecting the disk brake service life. Carbon-carbon composite materials have good stable friction properties, which enable them to operate as friction material in aircraft brakes application. This article discusses a wear simulation method for predicting the wear amount of c/c composite aircraft brakes under simulated operating conditions. A modified version of Archard’s wear equation is used in 2-D axisymmetric finite element model in order to predict the disk brake friction surfaces wear progression. The finite element commercial software COMSOL Multiphysics 5.5 is used to simulate wear and is presented in this paper. Wear law was implemented as a boundary ordinary differential equation (ODE) in a COMSOL Multiphysics simulation, considering wear depth (thickness) as the independent variable. Frictional heat generation is simulated as heat affects on material thermal properties and as a result surface deformation. Element removal technique i...
Proceedings of the Institution of Mechanical Engineers, Part J: Journal of Engineering Tribology, 2020
Brakes are very important component in any vehicle, used to stop the motion of it either by applying mechanical or hydraulic pressure on brake pads. By engaging and disengaging of braking action, the surface of brake components (or) materials is ruined after some time. Therefore, it is important to study and develop a new composition of brake materials which provides optimum coefficient of friction along with increasing wear resistance to the materials. Hence, new combination has been formulated for fabrication of brake composite material using powder metallurgy method which consist of copper-tin alloy mixed with silicon carbide as a base materials, aluminium oxide as an abrasive material with varying volume percentage of graphite and talc powder as a friction modifiers. The pin-on-disc test was performed on brake composite material to analyse their tribological properties namely friction and wear. From tribotest, it was observed that all composites give the friction coefficient in the range of 0.33−0.51andthelossofmaterialsintherangeof0.33-0.51 and the loss of materials in the range of 0.33−0.51andthelossofmaterialsintherangeof79-131 mg. Further, the mechanical, thermal stability and surface characterization were also carried out on brake composites using universal testing machine, vicker's hardness tester, thermogravimetric analyser and scanning electron microscope respectively. These results reveal a very marginal change in hardness, increase in compressive strength by increase of talc concentration to the matrix, uniform distribution of reinforcement into the matrix and multi stage degradation of material loss in thermograph.