Strength enhancement of 2D-SiCf/SiC composites after static fatigue at room temperature

The fracture behavior of 2D-woven-SiC-fiber/SiC-matrix composites (2D-SiCf/SiC) has been studied under monotonic tensile test conditions in air at room temperature. The specimens statically fatigued at 90% σR showed a higher ultimate tensile strength (UTS) and failure strain than those of the original ones. Microstructural observations suggest that the static fatigue process enhances slow crack growth (SCG) mechanisms in fibers and the extensive fiber/matrix debonding after fatigue could be responsible of the enhanced final strength observed. Ultimate tensile stress has been evaluated from mirror radii of broken fibres, although this method turns up to overestimate experimental data. In contrast, the fracture behavior of Nicalon fiber bundles agrees with the results obtained in these composites.