High-temperature subcritical crack growth in a 3D woven SiC-based composite

Abstract

This study investigates the subcritical crack growth behavior of a 3D woven SiC-based composite under cyclic loading at 1100°C in air. The composite was subjected to monotonic tension and tension–tension fatigue tests using both unnotched dumbbell-shaped and edge-notched specimens. Detailed examinations of crack growth were conducted through optical microscopy and X-ray computed tomography (XCT). While the monotonic tensile strength was found to be insensitive to millimeter-sized notches, the fatigue strength was reduced by 20%–30% in the presence of such notches. Crack growth was found to be irregular and chaotic at the mesoscale, influenced by the complex interplay of chemical and mechanical processes and spatial variability in the composite microstructure. The study emphasizes the importance of XCT imaging for accurate internal crack tracking. It also proposes a phenomenological fracture mechanics model to describe crack growth and lifetime prediction, highlighting the nonmonotonic nature of crack growth rates.