X-ray Computed Tomography Inspection of Novel Ceramic Matrix Composites

Abstract

Novel Ceramic Matrix Composites (CMCs) offer the promise of more highly performing structures, especially in aerospace applications, due to their excellent mechanical properties at elevated temperatures with respect to their density and their corrosion resistance. However, the development of such materials requires careful characterisation, and any deployment on an aircraft necessitates an appropriate nondestructive testing capability. This work sought to deploy and refine the method of Xray Computed Tomography (CT) in aid of the development of a novel CMC and subsequent deployment in a flying component. The target application was part of the exhaust system of a civil aircraft’s auxiliary power unit. The work included material characterisation at coupon-level, as well as technique development with a view towards the target application. For the former, high-resolution scans were performed in a range of configurations, including during tensile testing, to provide an understanding of microstructure and failure behaviour. For the latter, novel system configurations were explored to try to deal with the challenge of a large, thin-walled structure. Additionally, alternative or complimentary non-X-ray testing methods were trialled, notably including terahertz (THz) imaging. The material characterisation demonstrated the potential for the novel material to meet the requirements of the application. The terahertz imaging in a through transmission configuration was the most capable of the non-radiographic methods tested, providing an image that correlated very well with the reference CT scan, whilst the system development efforts yielded a configuration optimised for this class of 3D X-ray imaging applications.