Methodology for Testing Ceramic Materials. Appplication to the evaluation of a New Grade of Silicon Nitride

Dealing with ceramic materials since more than two decades, Thales Alenia Space (TAS) - France has constantly studied literature and norms about the derivation of allowables for different kinds of materials and applications. Thanks to the large range of encountered applications, some specific test jigs and procedures have been developed in order to address industrial challenges ranging from the evaluation of a new material to the qualification of large components for space applications. Recently, an in-depth investigation has been performed in the framework of the “Mechanical Design and Verification Methodologies for Ceramic Structures” [1] study funded by ESA in order to propose adequate strength tests at each step of ceramic structures development, for different verification stages and different model strategies. In this paper, the main outlines of this test methodology are illustrated through an example, namely, the test of a new grade of silicon nitride. This new grade is currently under evaluation. The recommendations to be provided for each step of the process are detailed, namely, the precautions to take during the first evaluation tests, the proper and detailed inspection of the samples after the tests, but also the specific tests to be performed in order to reach the qualification of large scale components.