Carbon Fiber Composite is a new kind of structual material which developed obviously in recent ten years. Carbon fiber can be composited with resin, plastic, glass, ceramic, metal and other material, after which the material become high in strength, light in weight and good in rigidity.

　　All in all development prospect of carbon fiber composite material is really wide.

　　Carbon fiber composite material can reduce the weight of aircraft, missiles, spacecraft in a large extent, which is a very nice way to improve payload of those craft. For example, some foreign aircraft and missiles reduce 20% to 30% weight by replace its material by carbon fiber composite. When intercontinental missiles and satellites are flying at a high speed, high temperature of thousand degree was generated by the frictioncraft between skin of craft and air. In order to ensure those craft run in good condition, special protective layer was invented. In fact most of those protective layer was machined by carbon fiber composite material.

　　Those protective layer made by carbon fiber composite have been used widely. At present, carbon fiber material have been used in following fields: fan blade of aircraft engine, floor of aircraft cabin and floor beam, landing gear of aircratf, brake pads, and etc. By the way, carbon fiber composite also can be applied in human body.

　　Carbon carbon composites (CFC) is a kind of material formed by high strength carbon fiber and carbon matrix which has been processed by enhancement graphitization,it can be widely used in various structure, heater and vessel under the high temperature environment .

　　Carbon carbon composites (CFC) has the following advantages compared with the traditional engineering materials of :

　　1).High strength (5 times steel).

　　2).High temperature resistance (it can still maintain excellent mechanical and electrical properties under 2000℃).

　　3).Thermal shock resistance.

　　4).The low coefficient of thermal expansion.

　　5).The small thermal capacity.

　　6).The low density (1.7).

　　7).The excellent corrosion resistance and radiation performance.

　　The main application fields of carbon carbon composites are:

　　1).The field of aerospace. Carbon carbon composites (CFC) can be used for aircraft wing and fuselage, satellite antenna and its support structure, the wing and shell of solar cell, the verton composite shell of large carrier rocket, engine casing, The shuttle structure parts manufacturing because of it has good thermal stability, high specific strength and stiffness.

　　2).Automotive industry. Carbon carbon composites (CFC) can be used in the manufacture of the automobile body, the force support element, the transmission shaft, the engine frame and its internal components because of the characteristics of the carbon carbon composite materials such as the special vibration damping,vibration damping and noise reduction, anti fatigue performance, damage is easy to repair, convenient integral forming,

　　3).The Chemical, textile and machinery manufacturing.Carbon carbon composites (CFC) is the material which composited by the carbon fiber with good corrosion resistance and resin matrix material, it can be used in the manufacture of chemical equipment, textile machines, paper machines, copying machines, high-speed machine tools, precision instruments, etc.

　　4).The medical science.Carbon carbon composites (CFC)has excellent mechanical properties and non-absorbing of X-rays characteristic,it can be used in the manufacture of medical X-ray machines and orthopedic frame etc.. Carbon carbon composites materials also has biological tissue compatibility and blood compatibility, good stability in biological environment, it also can be used as biomedical materials.

　　5).Carbon carbon composites (CFC) are also used in the manufacture of sports devices and used as building materials, etc..

　　Carbon carbon composites is one kind of high performance friction material, which has been successfully applied in the aviation industry.

　　Compared with other friction materials, carbon carbon composite materials with low density, high temperature resistant, high strength, thermal shock resistance, corrosion resistance, good vibration resistance and suitable friction coefficient and friction performance, is a comprehensive performance ,excellent high temperature friction material. Carbon carbon composites have become the preferred material for aircraft brake discs.

　　In addition to do the brake disc, carbon carbon composite material can also be used as sliding bearing material and piston of internal combustion engine.

　　As the friction material, carbon carbon composites will be more widely used. Therefore, it is of great significance to study the tribological properties of carbon carbon composites for guiding and promoting the application of carbon friction materials.

　　Carbon carbon composites reinforced with carbon fiber, matrix for the pyrolysis of carbon, the two are amorphous carbon. But in terms of its microstructure, carbon fiber and carbon fiber are randomly layer graphite structure. And the lamellar structure is different from that of pure graphite. Therefore, the friction behavior of carbon carbon composites can not be explained by the interlayer slip theory of graphite crystals.

　　The type of matrix is an important factor to influence the friction and wear properties. In two different density of carbon / carbon composites, medium density of carbon / carbon composite has good friction performance, which has low coefficient of friction, the wear volume than low density and high density of carbon / carbon composite low one order of magnitude. In the process of friction and wear, the change of friction coefficient of various carbon carbon composites is not the same.

　　Carbon fiber orientation has a strong influence on the friction and wear properties of carbon / carbon composites,at low speeds, when the parallel fiber on friction surface, the wear rate is much lower than the fiber perpendicular to the direction of the friction surface to, while the friction coefficient fiber perpendicular to the direction of the friction surface is much higher than; at high speed, friction coefficient and wear rate are not big difference, Z to increase the fiber content, can improve the rate of the thermal conductivity of the carbon carbon composite, reduce friction surface temperature, will influence the carbon / carbon composite friction and wear properties

　　carbon/carbon composite material integrated carbon material of high temperature properties and composite materials with excellent mechanical properties, with high specific strength and high specific stiffness, excellent ablation resistance and friction performance, good thermal shock resistance, low creep, high temperature strength retention rate high and good biocompatibility and so on a series of excellent properties, it can be as functional materials, and can be used as high temperature structural materials, is currently the only composite material for high temperature of 2800.

　　So far, the carbon carbon composites have been successfully application in missile reentry nose cone, solid rocket motor nozzle, aerospace aircraft structure parts, brake disc, a heat exchanger, high power electronic device radiator and artificial bones, joints, teeth many fields, the development potential of large.

　　As the ideal candidates for high temperature structural materials, carbon carbon composite material in the service process inevitably relates to fatigue loading situation of fatigue damage of the gradual accumulation of will lead to a material in a certain number of cycles suddenly fracture, the fracture often no obvious signs, the harm is great, so the fatigue behavior research has very important significance, received extensive attention.

　　The fatigue behavior of carbon carbon composite material is not only related to the composition and structure of the material, but also with the test parameters, the different load and different loading frequency reflect the fatigue behavior.

　　The research on the fatigue behavior of carbon carbon composite material despite extensive attention, but still very limited, in order to promote carbon carbon composite material can as soon as possible from the laboratory into the practical application stage, a comprehensive understanding of the fatigue behavior is the focus of future research.

　　The carbon carbon composite materials as excellent thermal structure, functional integration of Engineering materials, since its birth in 1958, it has been greatly developed in the military , the most important use is for the manufacture of missile warhead components. Due to its high temperature resistance, good wear. It has been widely used in solid rocket motor, aerospace structural parts of aircraft, aircraft and racing brake device, the heating element and mechanical fasteners, heat exchanger, aviation engine hot end components.

　　The properties of carbon carbon composites:

　　(1) The physical properties: the C / C composites after heat treatment in the chemical composition and elemental carbon higher than 99%, low density, has a strong affinity, due to the high melting point of elemental carbon, it has high temperature resistance, good corrosion resistance and thermal shock resistance, acid, alkali, salt.

　　(2) The mechanical properties: The strength, modulus of elasticity and friction and wear resistance performances are the mechanical properties of C/C composites.

　　(3)The high temperature stability: the room temperature strength of C/C composite can be maintained to 2500 C, the thermal stress of C/C composites is not sensitive, it has good resistance to erosion.

　　(4) The comprehensive performance evaluation: the strength and elastic modulus of C/C composite at room temperature is good, the production of C/C composite material is less, it can save material and manufacturing cost, it has high safety and reliability.

　　The research results show that the major factors which influences the thermal conductivity of carbon / carbon composites is the the microstructure of CVD pyrolytic carbon , in different CVD pyrolytic carbon , the CVD pyrolytic carbon which the main structure is the RL structure has the highest thermal conductivity; whether heat treatment of carbon / carbon composites thermal conductivity rate has considerable influence, but the heat treatment temperature increasing of carbon / carbon composite thermal conductivity is limited to improve.

　　The properties of carbon carbon composite not only has high specific strength, high specific modulus and other prominent structural material characteristics, but also has excellent friction and wear and thermal physical properties, it can well meet the high-speed jet aircraft brake materials. The carbon / carbon composite materials has become a new generation of prospects for the development of aeronautical materials. The air brake carbon / carbon composites on the microstructure is a heterogeneous mixture

　　With the rapid development of modern aviation technology, the research of aircraft brake friction materials is more and more important. During the instantaneous brake,almost all the kinetic energy will transform into heat energy,and emited by the braking material,the temperature of the dics will reach 1000~1500℃.

　　C/C composites is the latest aircraft friction material and their friction and wear properties are very important.Friction and wear properties of C/C composites from different techniques were studied and effects of braking speeds and pressure were also analyzed by most scholars.the optical microscopy,scanning electron microscopy,X-ray diffraction,laser Raman micro-spectroscopy are used to examine the morphology and structure of worn surfaces.

　　Studies showed that C/C composites mainly with rough laminar pyrolytic carbon have small uniform wear debris and the most stable friction and wear properties,which can maintain at high braking speeds and pressure and the linear wear is under 2μm/plate.time,owing to the highest degrees of graphitization and thermal conductivities. And C/C composites mainly with smooth laminar pyrolytic carbon have unstable properties of friction and wear owing to lower graphitization degrees and thermal conductivities. And C/C composites impregnated only by pitch have the highest wear rates and the linear wear is up to 27.33μm/plate.time.

　　The properties of C/C composites braking dics has a relationship with the CVD and friction film,the braking speed,braking pressure etc.

　　Some new types of military aircraft and some large civil aircrafts,C/C composites could replace the powder metallurgy.

　　The C/C composites material impregnated metals like C/C+Cu,C/C+Al,which have perfect integrate capability to be used as pantograph sliders and used in the speed-upping electrical locomotive.it’s also one of the main development direction of C/C composites materials.

　　Carbon carbon composite material for a series of unique mechanical, thermal and tribological system can replace the metal base composite material of a new generation of brake materials, its main characteristics are as follows:

　　Density is small, the density of the material at about 1.8 g/cm3, is 1/3 to 1/4 of metal matrix composites. Using the materials of brake components, compared to about 40% weight loss. For military aircraft, the aircraft can be improved measure of payload and lighter; For commercial aircraft, lose weight 1 kg equivalent to 3000 litres of fuel savings annually. So the cost of its use effect is remarkable.

　　Thermal stability is good, when to stop the plane take off, the surface temperature of the brake pads of more than 2000 ℃ above, carbon/carbon composites are neither melt adhesive, also won't buckling deformation, can continue to use after cooling; More than 660 ℃, the temperature of the metal matrix composites above will generate buckling deformation, lead to melt adhesive, need to repair the brake components. Therefore, made of carbon/carbon composites brake pads can not only improve the design margin of brake components, also improves the use safety of brake components. manufacturer: Beijing Greatwall Co.,Ltd..

　　The heat capacity of the heat capacity is big, the material is 2.5 times that of metal matrix composites have good heat function, improve the heat storage capacity of heat reservoir, reduce the operating temperature of the heat reservoir.

　　Stable friction coefficient, the material in a wide range of temperatures and stable friction coefficient, the plane soft braking process, improved the aircraft brake comfort.

　　Low wear rate, long service life. For at least 2 times of metal matrix composites, reduced the maintenance of the brake components.

　　Is higher than strength, especially the high temperature strength of steel more than 2 times , compared with the metal matrix composites, the material itself can be used as structural components, don't need other material skeleton support structure, simplify the structure of the brake components, improve the reliability and maintainability of the brake components.

　　Because of the material has the above characteristics, is especially suitable for used as aircraft brake materials, so since the 1990 s, carbon brake has become the standard configuration of new aircraft and a wide range of applications.