Quantitative non-destructive evaluation of drilling defects in SiCf/SiC composites using low-energy X-ray imaging technique

Qualitative and quantitative non-destructive testing and evaluation (QNDT&E) of drilling defects in SiCf/SiC composites are crucial to the manufacture of hot-section components of aero-engines. A new technique for the QNDT&E of drilling defects was established based on grayscale (G) variation caused by attenuation of the relative energy (Delta E) of incident X-rays in SiCf/SiC composites. Specimens with artificial defects and actual SiCf/SiC composite components were used as test specimens. An industrial X-ray imaging system was constructed, the changes in Delta E were analysed, and the G value distribution was studied experimentally. A series of experiments on the detectability and QNDT&E of drilling defects was conducted. The results show that different drilling defects can be detected using the G value distribution and changes in the digital X-ray imaging characteristics of the SiCf/SiC composites. Plane defects, like micro-cracks with opening of 0.1 mm, can be detected. The minimum and maximum absolute deviation between the measured and designed defect sizes was close to 0.0 mm and 0.1 mm, respectively, for a Phi 0.3 mm microdefect.