Carbon-carbon composites are the most interesting materials for the conception of the thermal shield of the solar probe space mission designed to study the solar wind and solar corona. The physico-chemical behavior and the structural modifications of some carbon-carbon composites at high temperature and under proton irradiation have been studied using SEM, XRD and Raman spectroscopy. The characterization of the as-received carbon-carbon composites show that the processing routes and the fiber preform have a strong influence on the microstructure of the composites: the fibrous preform 2.5D. the liquid consolidation and a final heat treatment allows to enhance drastically the graphitization degree of the carbon matrix and the fibers and the size of the crystallites. The high temperatures induce especially a decrease of the open porosity due to an amorphous carbon deposit at the surface of the material. This evolution has been observed mainly for the 2.5D structure. The high temperatures come to an evolution of the microstructure with a better crystallinity. an increase of the size and orientation of the crystallites of the fibers and matrix. The 2D structure presents, however, an increase of the disorder with the temperature. Finally, the hydrogen irradiation has only a very weak influence on the inner and surface degradation of the carbon-carbon composites. (c) 2004 Elsevier B.V All rights reserved.