Criteria for Crack Deflection-Penetration in EBC Coated Ceramics: A Parametric Study

Authors

Ali Abdul-Aziz, NASA Glenn Research Center, Cleveland, Ohio, USA
Ramakrishna T. Bhatt, NASA Glenn Research Center, Cleveland, Ohio, USA
Joseph E. Grady, NASA Glenn Research Center, Cleveland, Ohio, USA

Date of this Version

2015

Citation

Mechanics of Advanced Materials and Structures (2015) 12, 1039–1047

Comments

U.S. Government Work

Abstract

This article discusses results obtained from a parametric study to analytically evaluate the impingement of a crack at the interface of an environmental barrier coating (EBC) and a monolithic Silicon nitride (Si₃N₄) layered ceramics substrate. The study establishes a correlation that leads to determine if the crack is arrested or advanced by either penetrating or deflecting along the EBC/substrate interface. A finite-element-based fracture mechanics methodology is utilized to perform these calculations. Critical parameters determining penetration-deflection conditions in relation to EBC’s physical characteristics, such as porosity level, voids, and mini cracks, are determined for a single layer and multi-layered coating system coordinating the interactions between the EBCs (Mullite, Mullite mixture, Silicon nitride, etc.) and the substrate structure. Results showing thermo-mechanical stresses and stress/strain energy release relations with respect to crack penetration-deflection are presented and discussed as the crack is advanced.