Brake Friction And Wear Characteristics Of Carbon / Carbon Composites And Its Temperature Field

Carbon carbon composites is a new aircraft friction material and their ftiction and wear properties are very important. Temperature fields and Tribological and wear properties of C/C composites during braking were studied and efects of matrix carbon and experimental condition were also analyzed. In order to inquire into the worn mechanisms, the morphology and structure of worn surfaces and wear debris were examined through using optical microscopy, scanning electron microscopy, X-ray diffraction, laser Raman micro-spectroscopy.The main contents and the conclusions are as follows.1. A novel method for measuring the temperature of friction surface was proposed based on the difficulty of surface temperature test.which can show the surface temperature changed with braking time.and it plays an important role in studing temperature fields and friction and wear mechanisms.2.Effects of braking speed and pressure on friction and wear properties of C/C composites with different matrix carbon were studied. The results show that the friction coefficient of sample with rough laminar (RL) pytolytic carbon come to a head at the mid-to-low speed.and decreases with pressure;the friction coefficient of sample with resin-derived carbon also come to a head at the mid-to-low speed,while incresse with pressure and the amount of wear debris increase sharply at high pressure.while the friction coefficient and wear rate of sample with smooth laminar (SL) pytolytic carbon are small and they were immune to speeds and pressure3.Temperature fields of C/C composite samples with different matrix carbon were studied by means of finite element simulate and experiment.The result shows that high thermal gradients appear in the axis direction of the laboratorial samples, while low in the radial direction. The maximal temperature layer appears in the big radius of friction surface. On the real braking disc the maximal temperature layerappears in midial stator, Surface temperature and thermal gradients of A320 braking discs are higher than those of B757.4.Thermal gradients of sample with rough laminar (RL) pytolytic carbon are the less, because it's thermal conductivity was higher than other samples,and the heat of surface transfer to matrix rapidly. By contraries, thermal conductivity of sample with resin-derived carbon was the least so heat stock up in the braking surface conduct to matrix tardily and the thermal gradients are the most. and those of sample with smooth laminar (SL) pytolytic carbon are the least because it's friction coefficient was the least heat conduct to matrix well at the longest braking time .