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Proceedings Paper

Environmental barrier coating (EBC) durability modeling using a progressive failure analysis approach
Author(s): Ali Abdul-Aziz; Galib Abumeri; William Troha; Ramakrishna T. Bhatt; Joseph E. Grady; D. Zhu
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Paper Abstract

Ceramic matrix composites (CMCs) are getting the attention of most engine manufacturers and aerospace firms for turbine engine and other related applications. This is because of their potential weight advantage and performance benefits. As a protecting guard for these materials, a highly specialized form of environmental barrier coating (EBC) is being developed and explored for high temperature applications that are greater than 1100 °C1,2. The EBCs are typically a multilayer of coatings and are on the order of hundreds of microns thick. CMCs are generally porous materials and this feature is somewhat beneficial since it allows some desirable infiltration of the EBC. Their degradation usually includes coating interface oxidation as opposed to moisture induced matrix degradation which is generally seen at a higher temperature. A variety of factors such as residual stresses, coating process related flaws, and casting conditions may influence the strength of degradation. The cause of such defects which cause cracking and other damage is that not much energy is absorbed during fracture of these materials. Therefore, an understanding of the issues that control crack deflection and propagation along interfaces is needed to maximize the energy dissipation capabilities of layered ceramics. Thus, evaluating components and subcomponents made out of CMCs under gas turbine engine conditions is suggested to demonstrate that these material will perform as expected and required under these aggressive environmental circumstances. Progressive failure analysis (PFA) is applied to assess the damage growth of the coating under combined thermal and mechanical loading conditions. The PFA evaluation is carried out using a full-scale finite element model to account for the average material failure at the microscopic or macroscopic levels. The PFA life prediction evaluation identified the root cause for damage initiation and propagation. It indicated that delamination type damage initiated mainly in the bond and intermediate coating materials then propagated to the substrate. Results related to damage initiation and propagation; behavior and life assessment of the coating at the interface of the EBC/CMC are presented and discussed.

Paper Details

Date Published: 30 March 2012
PDF: 11 pages
Proc. SPIE 8346, Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2012, 834612 (30 March 2012); doi: 10.1117/12.912865
Show Author Affiliations
Ali Abdul-Aziz, NASA Glenn Research Ctr. (United States)
Galib Abumeri, AlphaSTAR Corp. (United States)
William Troha, Alpha STAR Corp. (United States)
Ramakrishna T. Bhatt, NASA Glenn Research Ctr. (United States)
Joseph E. Grady, NASA Glenn Research Ctr. (United States)
D. Zhu, NASA Glenn Research Ctr. (United States)

Published in SPIE Proceedings Vol. 8346:
Smart Sensor Phenomena, Technology, Networks, and Systems Integration 2012
Theodore E. Matikas, Editor(s)

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