Mechanical and Microstructural Assessment of Inhomogeneities in Oxide Ceramic Matrix Composites Detected by Air-Coupled Ultrasound Inspection

Ceramic Matrix Composites (CMC) are promising materials for high-temperature applications where damage tolerant failure behavior is required. Non-destructive testing is essential for process development, monitoring, and quality assessment of CMC parts. Air-coupled ultrasound (ACU) is a fast and cost...

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Bibliographic Details
Published in:Journal of composites science 2021-11, Vol.5 (11), p.286
Main Authors: Roßdeutscher, Jan, Mechnich, Peter, Flucht, Ferdinand, Shi, Yuan, Jemmali, Raouf
Format: Article
Language:English
Subjects:
air-coupled ultrasound testing
Ceramic matrix composites
Computed tomography
Damage tolerance
Damping
Frequency analysis
High temperature
Inhomogeneity
Inspection
Material properties
Matrix cracks
mechanical testing
Mechanical tests
Microscopy
Modulus of elasticity
non-destructive testing
Nondestructive testing
Quality assessment
Resonant frequencies
Shear modulus
Sintering
Tomography
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Summary:Ceramic Matrix Composites (CMC) are promising materials for high-temperature applications where damage tolerant failure behavior is required. Non-destructive testing is essential for process development, monitoring, and quality assessment of CMC parts. Air-coupled ultrasound (ACU) is a fast and cost-efficient tool for non-destructive inspections of large components with respect to the detection of material inhomogeneities. Even though ACU inspection is usually used for visual inspection, the interpretation of C-scan images is often ambiguous with regard to critical defects and their impact on local material properties. This paper reports on a new approach to link the local acoustic damping of an oxide CMC plate obtained from ACU analysis with subsequent destructive mechanical testing and microstructural analyses. Local damping values of bending bars are extracted from ACU maps and compared with the results of subsequent resonant frequency damping analysis and 3-point bending tests. To support data interpretation, the homogeneous and inhomogeneous CMC areas detected in the ACU map are further analyzed by X-ray computed tomography and scanning electron microscopy. The results provide strong evidence that specific material properties such as Young’s modulus are not predictable from ACU damping maps. However, ACU shows a high, beneficial sensitivity for narrow but large area matrix cracks or delaminations, i.e., local damping is significantly correlated with specific properties such as shear moduli and bending strengths.
ISSN:2504-477X
2504-477X
DOI:10.3390/jcs5110286