Internal damage evolution related to woven architectures in SiC_f/SiC composites investigated by in-situ synchrotron X-ray imaging and numerical simulation

Fiber-reinforced woven SiC_f/SiC ceramic matrix composites are currently recognized as the most promising materials for aero-engine turbine components, but the complex fiber architectures and pores affect their mechanical performance under extreme service conditions. To clarify the damage behavior related to fiber architecture in woven SiC_f/SiC composites, the X-ray Computed Tomography (XCT) combined with the in-situ testing is utilized to reconstruct the internal microstructures of the 2D- and 2.5D-woven SiC_f/SiC composites and visualize the evolution of damage under loading. The results indicate that in the 2D-woven composites, cracks at the interface between pure matrix and yarns propagate and connect with the adjacent yarns and pores, ultimately leading to the delamination failure. In contrast, the interlaminar constraint provided by the 2.5D-woven architecture prevents crack propagation. However, significant pore clustering in the 2.5D-woven composites induced by woven architecture results in reduced load carrying capacity and the final brittle fracture. The influence of fiber architectures and pores on the failure behavior of woven composites was further discussed based on Image-Based Finite Element Method (IB-FEM). It reveals that the stress concentration resulting from the woven architecture leads to delamination in 2D-woven composites, while the large pores result in localized debonding in the 2.5D-woven composite and the woven architecture prevents these cracks from propagating.