3D visualization and quantitative characterizations of damage evolution in C/SiC composites: Synchrotron X-ray CT and in-situ loading at 800°C

Continuous carbon fiber-reinforced silicon carbide (C/SiC) composites are critical structural materials in advanced aerospace and energy fields, where they are subjected to extreme thermo-mechanical loads above 800°C. The complex internal damage evolution in the bulk of C/SiC composites determines their structural integrity and service life. However, traditional ex-situ characterization methods fail to capture the dynamic 3D evolution of internal damage under such extreme conditions. In this study, an integrated experimental protocol combining in-situ synchrotron radiation X-ray computed tomography (SR-CT) with high-temperature tensile loading was developed to investigate the damage evolution in C/SiC composites. Two types of dog-bone specimens were designed: one with arc-shaped notches to localize damage and another with a central hole to simulate engineering riveted connections. In-situ tensile tests were conducted at 800°C in an inert nitrogen atmosphere using a dedicated testing system, and SR-CT scans were performed at different loading steps to visualize and quantify internal microstructures and damage evolution. Damage characterization reveals that damage initiates at high stress levels (>85% of fracture strength) in both specimens, with limited propagation before catastrophic failure and the volume fraction of damage during loading is significantly lower than that of initial cracks. This study validates the effectiveness of in-situ SR-CT for 3D visualization and quantitative analysis of damage evolution in C/SiC composites under high-temperature tensile loading, providing insights into their damage mechanisms under extreme thermo-mechanical conditions and supporting optimization of material design and performance.