A modified simple interface fracture test for ceramic environmental barrier coating on ceramic matrix composite

A new interface fracture test was developed for ceramic environmental barrier coatings (EBCs) on ceramic matrix composites (CMCs). The proposed test modifies an existing test in order to simplify specimen preparation. An asymmetric double cantilever beam (ADCB) test specimen with a stiffener adhering to the coating was used, and a wedge was inserted into the notch to open it. A formula to calculate interface toughness using the notch opening load and displacement was derived; it was expanded so that the toughness could be obtained from the wedge insertion load and displacement. The interface toughness of a model EBC/substrate system consisting of a mullite layer and Si bond coat on a monolithic SiC plate was measured to examine the validity of the test. The obtained interface toughness was in good agreement with that obtained by the original test in the previous study. The interface to be fractured was controllable by adjusting the position of the notch.