N121-023 TITLE: Innovative Lift Fan Clutch Plate Concepts

TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: JSF-Prop

RESTRICTION ON PERFORMANCE BY FOREIGN CITIZENS (i.e., those holding non-U.S. Passports): This topic is "ITAR Restricted". The information and materials provided pursuant to or resulting from this topic are restricted under the International Traffic in Arms Regulations (ITAR), 22 CFR Parts 120 - 130, which control the export of defense-related material and services, including the export of sensitive technical data. Foreign Citizens may perform work under an award resulting from this topic only if they hold the "Permanent Resident Card", or are designated as "Protected Individuals" as defined by 8 U.S.C. 1324b(a)(3). If a proposal for this topic contains participation by a foreign citizen who is not in one of the above two categories, the proposal will be rejected.

OBJECTIVE: Develop innovative concepts for more efficient and reliable clutch plates for a clutch that transfers the high-speeds and torque generated by jet engines to power a lift fan.

DESCRIPTION: Carbon-carbon composite clutch plates can meet a1,500 engagement life requirement for a lift fan clutch, but this is at least two times less than the desired lifetime. The carbon-carbon composite also does not consistently provide the desired range of friction coefficients. A new, innovative clutch plate concept that reduces wear rate and higher overall friction coefficient is required to increase the service life of the clutch.

The F-35 lift fan for vertical take-off and landing is powered by a rotational moment transferred from the engine through a clutch. The lift fan clutch is a 5 disk dry clutch. The clutch design constrains the size of the clutch plates to roughly one foot in diameter with a stack length of approximately 5 inches. The clutch engages at up to ~8500 rpm and the clutch plates must survive rotational speeds in excess of 10,000 rpm. The clutch plates are required to withstand a high shear load in transferring ~70,000 in-lb of torque. The required instantaneous dynamic friction coefficient is >0.1 with a desired mean static coefficient of ~0.2. The clutch plates need high thermal capacity and thermal conductivity to dissipate large amounts of frictional energy introduced at a very high rate during engagement and to avoid hot spot formation. The design must ensure minimum plate warpage. The heat sink must be able to absorb over 11,000 BTUs at an average temperature of 1500 F. In addition, because of the high speed operational environment, the clutch plates must meet a balance requirement of no greater than 5 gram-inches for each plate.

In addition to wear and friction coefficient requirements, issues that should be explored include oxidation, friction coefficient variability (e.g. low coefficient associated with a cold, damp clutch), heat capacity, thermal conductivity, and dust generation. Reliable service in a marine environment is required. The cost and weight of the proposed solution should be comparable to or better than the current system. Teaming with the lift fan clutch manufacturer is highly recommended to ensure that the range of requirements are understood and addressed and to facilitate transition.

PHASE I: Demonstrate the feasibility of innovative clutch material(s) to provide long wear life and a high, stable friction coefficient. Preliminarily evaluate weight and cost impacts. Forecast expected improvements.

PHASE II: Fabricate and test at least two full scale clutch stack prototypes. Evaluate wear, static & dynamic friction coefficients, friction coefficient variation, mechanical properties, thermal conductivity, heat capacity, oxidation, weight, and cost of the new clutch plate material.

PHASE III: Perform full-scale endurance testing of the optimized clutch material and transition the technology onto an F-35.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Technology developed for this clutch could be advantageous in any dry clutch design, benefiting by extending the service life. Brake systems (aircraft and automotive) could also benefit from this technology.

REFERENCES:
1. Field, K. A. (2004, February 22). The man with the fan. Design news.
http://www.designnews.com/article/1558-The_man_with_the_fan.php

2. Ludema, K.C. (1996) Friction, Wear, Lubrication: A Textbook in Tribology. CRC Press. http://books.google.com/books?id=YTi6CUI9Wa0C&dq=K.C.Ludema,+Sliding+and+Adhesive+Wear&source=gbs_navlinks_s

3. Tatarzycki, E.M., and Webb, R.T. (1992). Friction and Wear of Aircraft Brakes. Friction Lubrication and Wear Technology, ASM Handbook.18, p 582. http://www.asminternational.org/portal/site/www/AsmStore/ProductDetails/?vgnextoid=8ede7e0e64e18110VgnVCM100000701e010aRCRD

KEYWORDS: Turbine Engine; Clutch; Reduced Wear; Friction Coefficient; Shear Strength; High Temperature

** TOPIC AUTHOR (TPOC) **

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