Development of Reliability Based Life Prediction Methods for Thermal and Environmental Barrier Coatings in Ceramic Matrix Composites

Content Provider	Semantic Scholar
Author	Shah, Ashwin
Copyright Year	2001
Abstract	FORWARD:This report summarizes the technical work performed during the time period of June 2000through October 2000 for the Order No. C-71140-K entitled "Development of Reliability BasedLife Prediction Methods for Thermal And Environmental Barrier Coatings in Ceramic MatrixComposites." During this time period, literature survey related to the EBC/TBC (environmentalbarrier coating/thermal barrier coating) life models, failure mechanisms in EBC/TBC and theinitial work plan for the proposed EBC/TBC life prediction methods development was developedas well as the finite element model for the thermal/stress analysis of the GRC developed EBCsystem was prepared. Technical report for these activities is given in the subsequent sections.OBJECTIVE: The long term objective of the proposed work is to perform the research tomodel the structural behavior, cracking, crack propagation and develop reliability based lifeprediction of thermal barrier and environmental barrier coatings in ceramic matrix composites.However for the current funding period the scope is to:(i)(ii)(iii)(iv)Perform literature survey and evaluate the current trend of research, technicaldirection, methods and computer codes used to assess the structural behaviorcharacteristics, crack, crack propagation, life and uncertainties related to EBC/TBCs.Develop a plan to approach the problem related to uncertainties, modeling, durabilityand life prediction and design of EBC/TBCs.Discuss, report and concur on the approaches pursued and followed with the NASAProgram Manager on a timely basis.Document findings, benefits and shortcoming of different approaches in the form of aformal technical report.BACKGROUND AND FAILURE/LIFE ISSUES RELATED TO EBC/TBC:Computational model development research to predict behavior and failure of thermalbarrier coatings (TBC) traces back to past three decades. However, a very little effort has beenspent to develop life prediction models accounting for uncertainties in the governing variables.Current efforts in the Ultra Efficient Engine Technology (UEET) development program at theNASA Glenn Research Center (GRC) are focused not only on protecting components againstsevere thermal loads but also against the environmental effects such as moisture in the gas,debris, oxygen, etc. (references 1 and 2). The concept of protection against environmental effectsis unique and novel under development at GRC. Current EBC/TBC material systems developedat NASA GRC are capable of delivering the expected performance up to 2400 °F temperature.However, new materials called environmental barrier coatings (EBC) are being developed toachieve desired thermal/environmental protection for components to operate at the gastemperature of 3000 °F, coating surface temperature of 2700 °F, and bond coat substrateinterface temperature of at least 2400 °F with a desired life expectancy and assured reliability.The current state-of-the-art EBC system under development in the UEET system consistsof CMC (ceramic matrix composite) as substrate, silicon layer as a bond coat, a composite layerofmullite and BSAS (Barium Strontium Aluminum Silicate) and pure BSAS layer as EBC at thetop. A pictorial representation of this system is shown in the figure 1.
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Language	English
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Resource Type	Article