Fatigue crack propagation behavior at a notch for needled C/SiC composite under tension-tension loading

Fatigue test of a needled C/SiC composite with a notch under tension-tension cyclic loading was completed, and the main fatigue crack propagation curve of the needled composite was obtained by the in situ observation of the fatigue process. By analyzing the influence of the failure number and distribution on the tensile loading subjected by 0 degrees fiber bundles, the relationship between the main fatigue crack propagation and the distribution of 0 degrees fiber bundles in the needled composite was established. By observing the fracture microstructure (especially the distribution of 0 degrees fiber bundles) of the needled composite through scanning electron microscopy, the reasons for the varying fatigue resistance of different notched specimens were also explained. In addition, acoustic emission (AE) was also used to analyze the AE energy characteristics during the fatigue crack propagation process of the needled composite.