The use of composite materials is growing over nowadays, not only in the aerospace industry but also in automotive, construction and sailing sectors. Carbon Fibre Reinforced Polymers (CFRPs) bring lighter structures but with an impressive mechanical behaviour. Therefore, it seems to be important understanding the different degradation processes, especially matrix cracking and delamination. The aim of this study is to characterize the degradation of CFRPs because of thermal fatigue in different atmospheres. Due to the lack of inspection contrast, a specific method consisting in tomographic characterization and image processing method has been developed. In this way, a complete quantification of the degradation process, in terms of crack and delamination volume, can be performed.