Study on the folding damage mechanism of SiC fiber braided fabric based on synchrotron radiation CT and finite-element analysis

Silicon carbide (SiC) fiber exhibits high strength, thermal resistance, and chemical stability, but its insufficient flexural strength renders it unsuitable for use in flexible structural materials. In this study, the microstructure evolution and damage mechanisms of SiC fiber braided fabric were investigated at different braiding angles and folding stages using synchrotron micro computed tomography (µ-CT) and finite-element analysis. Results from synchrotron radiation CT scans indicate that, with an increase in the number of folding cycles, both fiber surface fractures and slippage gradually increased, leading to a looser internal structure and diminished fiber continuity. The SiC fiber braided fabric at 37.8° was predominantly influenced by the folding behavior, exhibiting a higher frequency of fiber breakages. Conversely, the 43.1° SiC fiber braided fabric was primarily affected by inter-bundle abrasion, resulting in looser fiber bundles and increased slippage. In the case of the 41.2° SiC fiber braided fabric, under the combined effects of friction and folding, the highest occurrences of fiber slippage and breakages were observed. Finite-element simulation results reveal that the stress at the folding site of the 40° braided fabric was higher than those of the 45° and 50° braided fabrics, confirming the experimental conclusion that the folding resistance of SiC fiber fabrics is poorest at a braiding angle of around 41° to 42°. This research is of significant importance for a deeper understanding of the folding performance and damage behavior of SiC fiber braided fabric, providing valuable insights for further optimizing material design and applications.