Elevated-temperature in-situ μCT characterization and progressive damage simulation of EBC-coated SiC/SiC ceramic matrix composites

In-situ damage evolution studies of SiC/SiC ceramic matrix composites (CMCs) with environmental barrier coatings (EBCs) under elevated temperature remain limited. In this work, in-situ μCT tensile experiments were conducted on two-dimensional woven SiC/SiC composites with EBCs at 1350 °C, 1600 °C, and 1800 °C, using a non-contact laser heating system and infrared thermometry for temperature control. CT images were analyzed via deep learning algorithms to systematically investigate porosity, void connectivity, and crack propagation characteristics. A thermomechanical coupled multilinear constitutive model for SiC/SiC composites was proposed and validated, along with a degradation approach for yarns and matrix properties at elevated temperatures, and a finite element modeling method incorporating mesoscale porosity. Both experimental and numerical results reveal that inter-yarn voids and specimen edges serve as crack initiation sites during initial loading. Cracks then propagate perpendicular to the applied stress and merge with cracks from adjacent voids. The experiments demonstrate that excessive temperatures lead to grain growth in both fibers and matrix, thereby reducing the composite strength. The numerical model incorporating degraded properties of yarns and matrix successfully captures the observed decline in tensile strength of SiC/SiC composites with increasing temperature.