TECHNOLOGY AREAS: Materials/Processes

ACQUISITION PROGRAM: F35/Joint Strike Fighter

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop innovative, environment-resistant matrix materials in SiC fiber-based Ceramic Matrix Composites (CMCs).

DESCRIPTION: The Joint Strike Fighter and other military platforms are targeting CMCs for aeroengine airfoil applications with a goal of increased specific power. Concerns exist regarding the degradation of CMCs at elevated temperatures due to life limiting phenomena related to thermal, chemical, and environmental instability of those materials. Of particular concerns are combined or individual effects of creep, fatigue, oxidation, sand or CMAS (calcium magnesium aluminosilicate), water vapor, salt, erosion, and foreign object damage (FOD), etc. Environmental barrier coatings (EBCs) or some specific-purposed coatings in SiC/SiC CMC systems have been utilized at <2400 F to mitigate or to prevent deleterious effects associated with harsh engine operating conditions. The EBCs or other coatings, however, are typically a separate external material system with appropriate bond coats at the coating-substrate interfaces, which requires several fabrication steps in addition to added materials. It is, therefore, from a prospective of cost-effectiveness, highly desirable to develop pertinent integrated matrix material systems that could fulfill or outperform the function of those external protective coatings. Particular emphasis is in durability and stability of materials at 2400 F against attacks of CMAS, water vapor, salt, and FOD, with minimal degradation of mechanical properties.

PHASE I: Develop and determine the feasibility of innovative approaches to ceramic matrix materials of SiC fiber-based CMCs, which could perform in place of EBCs up to 2400 F under Navy aeroengine conditions.

PHASE II: Develop, demonstrate and validate the pertinent CMC systems developed in Phase I. Evaluate the CMCs in various environments described above and demonstrate the materials� durability and stability through appropriate test methods including mechanical property testing using a reasonable number of test coupons.

PHASE III: Transition the approach to JSF and additional propulsion applications.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: CMCs propulsion components have a great potential to transition to the civilian aeroengine applications. The resulting material development, albeit risky, could allow a significant cost saving while the developed material could outperform the conventional coating systems. The development will also open a new means of material/component designs by simplifying fabrication and maintenance processes.

REFERENCES:
1. K.N. Lee, "Rare Earth Silicate Environmental Barrier Coatings for SiC/SiC Composites and Si3N4 Ceramics," J. Eur. Ceram. Soc., 25 1705-1715 (2005).

2. T. Bhatia, et al., "Advanced Environmental Coatings for SiC/SiC Composites," ASME Paper No. GT2005-68241 (2005), ASME Turbo Expo 2005.

3. K.M. Grant, S. Kraemer, J.P. Lofvander, C.G. Levi, "CMAS Degradation of Environmental Barrier Coatings," Surface & Coatings Technology, 202 [4-7] 653-657 (2007).

4. S.R. Choi, et al., "Foreign Object Damage Behavior of a SiC/SiC Composite at Ambient and Elevated Temperatures," ASME Paper No. GT2004-53910 (2004), ASME Turbo Expo 2004.

KEYWORDS: ceramic matrix composites (CMCs); SiC/SiC composites; environmental barrier coatings; ceramics; ceramic matrix; SiC fibers

** TOPIC AUTHOR (TPOC) **

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