N22A-T019 TITLE: Enhanced Thermal, Mechanical, and Physical Properties of Ceramic Matrix Composites Through Novel Additives

OUSD (R&E) MODERNIZATION PRIORITY: General Warfighting Requirements (GWR);Hypersonics;Space

TECHNOLOGY AREA(S): Air Platforms;Materials / Processes;Space Platforms

OBJECTIVE: Enhance and optimize oxidation resistance and thermal, mechanical, and physical properties of ceramic matrix composites (CMCs) through computational-directed and validated design and the addition of additive(s) to the CMC.

DESCRIPTION: The service life of ultra-high temperature materials such as CMCs in gas turbine engines or hypersonic applications is dependent on a complex combination of temperature-stress- environment- time conditions. Maximizing thermal transport to avoid local hot spots on leading edges of reusable hypersonic structures and optimizing tensile strength require a thorough understanding of CMC phenomena. Additives such as nanoparticles and micron-sized chopped fibers have been reported to reduce localized mechanically and thermally-induced stresses thereby increasing overall strength and toughness. Informed design will enhance interphase coatings and reduce CMC porosity. Modeling strength and deformation processes of CMCs as a function of CMC structure and additive load will lead to fabrications processes that maximize CMC component strength.

PHASE I: Using Integrated Computational Materials Engineering (ICME) functionalities, establish models to predict the effect of composition on phase stability and key properties in ceramic matrices such as thermomechanical and thermochemical behavior with and without the application of additives as a function of temperature. The ICME effort needs to be combined with experimental approaches to generate requisite information for model validation. Develop a process for applying novel additives to CMC fibers. Evaluate the oxidation resistance and creep resistance of SiC CMC fibers with and without the addition of novel additives as a function of temperature up to 2000oC, if possible. Develop a Phase II plan.

PHASE II: Apply validated models, developed in Phase I, to the synthesis of advanced matrices and coatings, initially as monolithic materials and later in sub-systems and complete EBC/CMC systems. In coordination with an appropriate original equipment manufacturer (OEM), establish and execute a test plan that will provide sufficient data for preliminary assessment of design allowables for critical and relevant design requirements. These requirements will be developed in conjunction with an OEM and ONR. Test samples will be manufactured with different testing geometries (necessitated by uniformity and testing hardware requirements) for determination of thermal and mechanical property data, including: density, hardness, thermal conductivity, thermal expansion, tensile strength, modulus, creep, and creep rupture, and vibrational and dynamic fatigue.

Test conditions shall include controlled stress, temperature, and time under environmental conditions, including simulated turbine engine by-products of combustion gases with and without sodium sulfate and water present. By the end of the Phase II, ensure that data will be available to initiate constituent modeling of modified CMCs with lifetime predictions of oxidation resistance and thermal-mechanical-creep performance up to 100 hours. Also ensure that thermal-mechanical-creep tests will reach up to 1000 hours at 2000�C or more.

PHASE III DUAL USE APPLICATIONS: Adoption of models/optimized matrix by an OEM for further maturation to manufacture robust self-healing matrix CMC components that can operate in complex environments with less maintenance, lower overall life cycle cost, and improved operational capabilities. Coordinate with an engine OEM on work toward further maturation of the knowledge and/or process to fabricate CMC engine components for military and commercial platforms or show how the CMCs with additives can perform at temperature exceeding 2000�C.

REFERENCES:

1. DeCarlo, J.A. and van Roode, M. "Ceramic Composite Development for Gas Turbines Engine Hot Section Components." ASME Turbo Expo 2006, Power for Land, Sea and Air, May 8-11, 2006, Barcelona, Spain. Paper GT2006-90151. https://asmedigitalcollection.asme.org/GT/proceedings-abstract/GT2006/42371/221/314649.
2. Padture, N.P. "Environmental Degradation of High-Temperature Protective Coatings for Ceramic Matrix Composites in Gas Turbine Engines." Nature: npj Materials Degradation, v. 3, p.11, 2019. https://www.nature.com/articles/s41529-019-0075-4.
3. "US Hypersonic Initiatives Require Accelerated Efforts of the Materials Research Community." MRS Bulletin, Vol. 46, March 2021. https://link.springer.com/content/pdf/10.1557/s43577-021-00050-2.pdf.
4. Lauten, F.S. and Schulberg, M.T. "Composite Materials for Leading Edges of Enhanced Common Aero Vehicles and Hypersonic Cruise Vehicles." Physical Sciences Inc., 2006.
5. Evans, A.G.; Zok, F.W.; McMeeking, R.M. and Du, Z.Z. "Models of high temperature, environmentally assisted embrittlement in ceramic-matrix composites." Journal of the American Ceramic Society, Vol. 79, Issue 9, September 1996, pp. 2345-2352. https://ceramics.onlinelibrary.wiley.com/doi/10.1111/j.1151-2916.1996.tb08982.x.

KEYWORDS: Ceramic Matrix Composite; CMC; gas turbines; hypersonics; nanoparticles; ultra-high temperatures; oxidation resistance; metal carbines