Modelling of the Porousness inside 2.5D Carbon/Carbon Composites

Abstract

Carbon/Carbon (C/C) composite is a kind of material that has good mechanical property in environment with high temperature above 2000°C. Due to its low density, high specific modulus, high specific strength, high temperature resistance, ablation resistance and corrosion resistance, it has been successfully used for manufacturing parts used in the aero-engine or rocket parts. While fabricating this kind of composite material with the carbonization and graphitization process, porousness with different sizes will be left inside the material. These porousness will affect the milling process, which is a commonly used method for manufacturing the C/C composite parts. To address this problem, a mathematical model is developed to describe the distribution of the porousness inside the 2.5D C/C composite. Firstly, the machined section of the specimen is scanned with the high resolution optical scanning instrument and then transformed to an image. Secondly, the porousness inside the specimen is extracted to calculate their distribution and proportion. Finally, an exponential distribution model is found to be suitable for distribution of porousness inside the material and an algorithm for simulating the pore distribution is established. It is found that the simulated surface is in a good agreement with the measured surface, yielding a relative difference in predicted porosity of 19.6%. The pore distribution of simulated surface also conforms the exponential function distribution. Its coefficients are within the range of the real surface, which verifies the feasibility of the algorithm.