In-situ X-ray tomography and acoustic emission monitoring of damage evolution in C/C-SiC composites fabricated by liquid silicon infiltration

Carbon fiber-reinforced silicon carbide (C/C-SiC) ceramic matrix composites are attractive materials for high-temperature applications due to their excellent thermal and ablation resistance. This paper investigates how the morphology of residual silicon affects damage behavior in C/C-SiC composites fabricated via the Liquid Silicon Infiltration (LSI) process using thermoplastic precursors. Two model materials are examined: one with interconnected silicon and another with isolated silicon. In situ X-ray computed tomography (XCT) is combined with acoustic emission (AE) monitoring during tensile testing. The multi-modal approach enables full-field strain mapping and real-time tracking of damage evolution. The results reveal that the distribution and connectivity of the silicon bulks significantly influence local strain distributions and crack development, features that are not accessible through conventional macroscopic testing. This detailed study demonstrates the value of integrating XCT and AE data into a unified damage analysis framework to overcome the limitations of each in isolation. This work provides a first microstructure-level investigation on how residual silicon and its local arrangement influence damage behavior of C/C-SiC composites. The new insights gained here contribute to an in-depth understanding of microstructure-performance relationships in C/C-SiC composites, highlighting pathways for optimizing LSI processing parameters to enhance damage tolerance.