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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.
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