Dielectric property measurement of a SiCf/SiC ceramic matrix composite via microwave cavity characterisation

Abstract

Ceramic Matrix Composites (CMCs) are used for high temperature structural engineering applications, such as those found within gas turbine engines. When operating in these environments they can undergo oxidation and damage that may not be easily detectable, emphasising the need for a non-invasive assessment approach that could detect such changes. In this research, we use a single mode microwave cavity for sensitive dielectric property measurement as a method of assessment for Silicon Carbide (SiC) CMC material. We have also used this method to characterise individual bundles of SiC fibres, to develop an understanding of the method. Environmental conditions are then applied to the CMC samples including a high temperature exposure at 800 °C, and humidity exposures followed by two different 800 °C reheat durations. Characterisation was performed on the pre- and post-exposed material to verify the severity of each exposure, both microstructurally and mechanically, to compare these with microwave dielectric property data.