The physical properties of carbon/carbon composite material are mainly included:density, degree of graphitization,hardness, thermal conductivity, electric conductivity, specific heat, coefficient of thermal expansion etc.Among these properties,the density,thermal conductivity and the graphitization are very important to the carbon carbon composite material which is used for aviation brake.
The density can be the direct response of the C/C material,and it’s the basis of other properties,and the density depends on the density of the carbon fiber and the matrix carbon and the porosity.
The degree of the graphitization is another important parameter of the C/C composite material,it has a close contact with the strength and friction property.now,there is no uniform method to test the graphitization degree,the ways to test it are mainly included XRD, laser Raman spectrometry, magnetic resistance method, electrical resistivity method etc.
The thermal conductivity is also important to the carbon carbon composite material,it’s a symptom during the heat absorption and heat release. In the brake process,the C/C material must have the ability to absorb and release much heat to make the brake device work well.the thermal conductivity of C/C material depends on the carbon fiber and matrix carbon,and the structure, density ,and the graphitization also have a contribution to the thermal conductivity. The volume fraction and the direction of the carbon fiber have a big effect on the thermal conductivity of the carbon carbon composite material.Some researches show that the larger density can lead to a higher thermal conductivity.
