Abstract: The thermal expansion law of matrix-modified C/ C composites under high temperatures is studied. Theresults show that the law, between the temperature and the thermal expansion coefficient of C/ C composite, accordswith the general linearity which exists in carbon materials under 900 ℃. However, the law, between the temperature and the thermal expansion coefficient of matrix-odified C/ C composite, meets exponential relation from 900 ℃to 1500 ℃. The law is reliable and reasonable as indicated by our experiments and mathematical analysis. Therefore,it is significant for improving the matching degree of the thermal expansion coefficient between C/ C composites andtheir coatings, and for raising the ability to resist oxidation under high temperatures.

Key words: matrix-modified, C/C composites, thermal expansion coefficient, law