You are here

Environmental Performance Prediction of Ceramic Matrix Composites in Extreme Environments


TECH FOCUS AREAS: Nuclear; General Warfighting Requirements (GWR) TECHNOLOGY AREAS: Nuclear; Materials; Air Platform OBJECTIVE: Predicting failure of ceramic matrix composites in extreme environments requires analyses of high local velocities, temperatures and forces together with oxidative, ablative, and strength-reducing material evolutions and local strains. This D2P2 should model the material degradation of a surface-morphing high speed aircraft, and support critical predictions with measured data. DESCRIPTION: The need for understanding performance of materials in extreme environments has exploded over the last few years, particularly with the push for operational high speed systems; however, models capable of providing this information have been limited. As a result, performance of these systems is primarily determined through expensive experimental programs, which have limited the pace of development in this area despite the fact it is a current national defense priority [1]. Recently, the Air Force Research Laboratory executed a benchmarking study, “Enhanced Physics-based Prognosis and Inspection of Ceramic matrix composites (EPPIC),” [2] to assess the current ability of progressive damage models to capture behavior of ceramic matrix composites (CMCs) in service relevant conditions. While this program was highly successful, the lack of ability to address the environmental degradation aspects of the expected extreme service environments was a major issue. In particular, the ability to analyze high local velocities, temperatures and forces is needed to properly predict oxidative, ablative, and strength-reducing material evolutions and local strains required for failure. AFRL has been developing environmental damage models for CMCs capable of addressing this current gap in capability. Specifically, a SiC/BN/SiC oxidation damage micromodel was recently published [3].This topic seeks to formulate an environmental damage model for silicon carbide (C/SiC) CMCs and transition it to industry to address the current challenges in modeling the complex thermo-mechanical behaviors of C/SiC CMCs in extreme high speed relevant environments. The model should consider the following processes in C/SiC: (i) diffusion of oxygen and moisture across the surface boundary layer and through the cracks in the matrix, including Knudsen effect; (ii) oxidation of SiC crack walls to form SiO2 and associated gradual closure of the crack opening; (iii) volatilization of coating (SiC in this case at extreme temperatures); (iv) oxidation of SiC fibers and matrix surrounding them; (v) out-diffusion of (several in-common) gaseous oxidation products, such as CO, CO2, SiO(g), Si(OH)4, etc., through the cracks and fiber/matrix gaps in the silicon carbide matrix. The present topic addresses C/SiC materials and structures applicable to high speed vehicles and emphasizes corresponding boundary conditions & strains, damage of the more oxidation-resistant SiC matrix, and subsequent oxidation and weakening of carbon tows leading to failure. Data gathered in relevant environments (arc-jet, heated wind tunnel, etc.) is recommended to develop confidence in the predictive capabilities of proposed models in high-speed vehicles. Unstressed and stressed oxidation experiments on C fibers and C/SiC show rapid consumption of the C phases [6,7]. Different C and SiC materials may have significant differences in oxidation behavior due to microstructure and processing (e.g., [8]). Previous C/SiC oxidation models assume strength loss due to the reduced cross-sectional area of the C fibers and do not consider thermal degradation of fiber strength [9,10]. Additional experimentation exploring the strength loss in carbon fibers due to thermal degradation may be required for the model. Data from in-situ micro-tensile experiments monitoring cracking behavior at elevated temperatures may be useful as inputs for the model. PHASE I: This topic is intended for technology proven ready to move directly into a Phase II. Therefore, a Phase I award is not required. The offeror is required to provide detail and documentation in the Direct to Phase II proposal which demonstrates accomplishment of “Phase I-like” capabilities, including a feasibility study. Existing capabilities can be established via prior reports and/or journal publications on subjects such as related materials development and testing in harsh environments; CFD modeling accounting for vehicle- and/or component-level aerothermal environments including such features as mass loss, surface reaction systems, oxidation, sublimation, and spallation in extreme environments; related relationships with high-speed DoD air vehicle integrators evidenced by prior reports and/or publications. This includes determining, insofar as possible, the scientific and technical merit and feasibility of ideas appearing to have commercial potential. The D2P2 proposal should show direct benefit to a potential AF operational system, evidenced by endorsement of an associated stakeholder. The offeror should have defined a clear, immediately actionable plan with the proposed solution and the AF customer. The feasibility study should identify the prime potential AF end user(s) of the final modeling and/or material improvements; estimate integration cost and capability improvements vs current mission-specific products; describe if/how the demonstration can be used by other DoD or Governmental customers, and possibly non-governmental customers. PHASE II: Under the phase II effort, the offeror shall sufficiently develop the technical approach, product, or process in order to conduct a small number of performance/life prediction-relevant demonstrations. These demonstrations should include relevant environment testing in relevant high-enthalpy environments such as arc jet, wave rotor, plasma torch, heated wind tunnel, etc. Vehicle-level performance improvements and limitations associated with morphing surfaces should be assessed for relevant maneuvers of a high speed vehicle. Identification of manufacturing/production issues and or business model modifications required to further improve product or process relevance to improved sustainment costs, availability, or safety, should be documented. Air Force sustainment stakeholder engagement is paramount to successful validation of the technical approach. These Phase II awards are intended to provide a path to commercialization, not the final step for the proposed solution. PHASE III DUAL USE APPLICATIONS: A phase III program should involve a relevant AF command in partnership with the small business, to build and test morphing component parts of a relevant model aircraft. Prime contractor integrators involved with military high speed vehicle development would be examples of appropriate partners. Boeing, Hermeus and other commercial companies are engaged in building hypersonic passenger planes. The U.S. Air Force has awarded the Hermeus Corporation a contract to support its work on a hypersonic aircraft powered by an advanced combined-cycle jet engine. The service says that the deal could be a stepping stone to fielding a high-speed plane for VIP transport and other missions in the future. Such companies may be able to leverage the analytical developments across future military and commercial platforms. NOTES: The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the proposed tasks intended for accomplishment by the FN(s) in accordance with section 5.4.c.(8) of the Announcement and within the AF Component-specific instructions. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. Please direct questions to the Air Force SBIR/STTR HelpDesk: REFERENCES: 1) Shyu, H. “USD(R&E) Technology Vision for an Era of Competition,” 1 February 2022.; 2) Parthasarathy, T.A., et al. J. Am Cer. Soc. 101.3 (2018); 973-997.; 3) Medford, J., 10th Thermophysics Conference. 1975.; 4) Medford, J., 12th Thermophysics Conference. 1977. ; 5) Halbig, M.C., et al. J. Am Cer. Soc. 91.2 (2008); 519-526.; 6) Opila, E.J., Serra J.L. J. Am Cer. Soc. 94.7 (2011); 2185-2192.; 7) Brown, T. C., Carbon 39.5 (2001); 725-732.; 8) Mei, H. Adv. Appl.Cer. 108.2 (2009); 123-127.; 9) Ding, J., et al. Applied Composite Materials 28.5 (2021); 1609-1629. KEYWORDS: morphing; high speed; enthalpy; testing; arc jet; wave rotor; plasma; oxidation; sublimation; spallation; ablation; modeling; performance;
US Flag An Official Website of the United States Government