Design and Virtual Testing of Environmental Barrier Coatings (EBCs)
Abstract
Environmental barrier coatings (EBCs) are critical to achieving higher temperatures andgreater efficiency in propulsion and power turbines, as they are required to ensure the durabilityof ceramic matrix composites. This proposal targets two central challenges in the development ofeffective EBCs: (i) the identification of effective combinations of material system and layerarchitecture that promote thermo-mechanical stability, and (ii) the development of a virtualtesting framework to simulate coating response to thermal cycling, chemical attack, and foreignobject damage from high speed impacts.In the first thrust of the program, software developed during a previous ONR programwill be utilized to generate property combinations that avoid delamination and crack penetration(mudcracking) into underlying silicon bond coats. Particular attention will be placed on coatingsystems utilizing rare earth silicates (such as yttria and ytterbium), BSAS and mullite. Designmaps will be generated that identify regions of the parameter space (defined by materials, layerthicknesses and operating temperatures) that avoid failure and illustrate the sensitivity of theoperational envelope to system properties. This study of the design space will consider the roleof CMAS on cracking to ensure robustness in the presence of reaction layers. The accuracy ofthese design maps will be evaluated by comparison with experimental characterization of systemsin the literature and those emerging from programs at UCSB and other institutions funded byONR.In the second thrust of the program, virtual test frameworks will be developed using thefully explicit dynamic cohesive zone formulations developed under a previous award, which arecapable of predicting evolving crack patterns. These tools will be applied study the nature ofimpact damage in multilayered EBCs, with an emphasis on identifying critical impact parameters(e.g. project speed, size and mechanical properties) that produce cracks that penetrate the coatingto the underlying composite. Further, these simulation platforms will be extended to include theeffects of time-dependent CMAS infiltration, including the propagation of reaction zones andtheir impact on mechanical stability during cooling. Particular attention will be focused ondetermining the effect of localized CMAS penetration into cracks or microstructure/defectboundaries (such as splats or voids) and its role in subsequent cracking during thermal cycling.This effort will be deeply enhanced by strong synergies with other UCSB programs withclose ties to industry, which are focused on the separate yet related challenge of oxidation ofsilicon-rich phases.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 05, 2017
- Source ID
- N000141712351
Entities
People
- Matthew R. Begley
Organizations
- Office of Naval Research
- United States Navy
- University of California, Santa Barbara