TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: F-35/Joint Strike Fighter ACAT I

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 and demonstrate high-speed, precision, laser-assisted machining processes and/or tooling for silicon carbide based ceramic matrix composites (CMCs).

DESCRIPTION: Engine and exhaust washed aircraft structures require highly efficient CMC designs to minimize weight and withstand severe environmental conditions. These components are time-consuming and expensive to fabricate and require post-fabrication machining to precise dimensions. The machining process is made difficult due to the low thermal conductivity and hard, brittle, abrasive nature of CMCs. As a result, existing methods of machining and drilling processes are inefficient and expensive. Machining tools are easily damaged and require frequent replacement due to over-heating and repeated contact with the hard and abrasive material. In addition, the CMC components are prone to damage from improper machining. Also, the precision laser focusing, polarizing and reflective surfaces are subject to dust contamination and abuse in a machine shop industrial environment affecting system performance and reliability. A high-speed machining process or method for silicon carbide CMC design is anticipated to eliminate many of the major cost and risk impediments for transitioning these materials into aircraft production.

Innovative, scalable, high-speed, and precise process(es) are sought to fabricate and machine silicon carbide CMC components for engine and exhaust washed aircraft structures. In particular, precision slotting and milling processes should be developed and demonstrated. Possible approaches may explore the use of laser-assisted contact machine tools and/or methods for CMC material removal. Proposed processes should be designed to minimize damage to the substrate and limit replacement of machining tools. It is anticipated that the results of this work will lead to process guidelines and tooling designs that allow a 10 fold reduction in time and cost to machine these components, a significant reduction in part rejection/rework, and decreased maintenance costs of machining tools.

PHASE I: Demonstrate scientific merit and feasibility of the proposed high-speed, laser-assisted machining processes and integrated tooling concepts for precision CMC milling process/material removal operations for typical contours and shapes. Prototype machined samples should be characterized micro-structurally, and mechanically tested for strength and fatigue durability.

PHASE II: Develop the prototype laser-assisted machining process and integrated laser and contact machining tools based on the Phase I work. Fabricate prototype machined samples, and eventually a full-scale component, to be characterized micro-structurally and mechanically tested for strength and fatigue durability.

PHASE III: Generate generic process guidelines and production suitable laser-assisted contact machine tools for use in fabricating high temperature silicon carbide CMC components. Produce and qualify components using the high-speed machining process and transition to current and emerging aircraft production.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: More widespread usage of CMC components using high speed machining processes is expected for the aerospace, power generation and automotive industries.

REFERENCES:
1. Lopez de lacalle, L.N. J. Perez, J.I. Liorente, and J.A. Sanchez. "Advanced Cutting Conditions for the Milling of Aeronautical Alloys." J.Matls. Proc. Tech., 100 (2000) 1-11.

2. Ezugwu, E.O. "High Speed Machining of Aero-Engine Alloys." J. of the Braz. Soc. of Mech. Sci & Eng., (January-March 2004), Vol XXVI, No. 1, 1-11.

3. Rozzi, J.C., F.E. Pfefferkorn, Y.C. Shin and F.P. Incropera. "Experimental Evaluation of the Laser-assisted Machining of Silicon Nitride Ceramics." ASME Journal of Manufacturing Science and Engineering, (2000), Vol 122, 666-670.

4. Lei, S., Y.C. Shin and F.P. Incropera. "Experimental Investigation of Thermo-Mechanical Characteristics in Laser-assisted Machining of Silicon Nitride Ceramics," Transactions ASME, Journal of Manufacturing Science and Engineering, (Nov 2001), Vol 123, 639-646.

KEYWORDS: Silicon Carbide Matrix Composites; High-Speed Machining; Ceramic Matrix Composites (CMC); Nozzles; Machine Tools; High Temperature Structure

TPOC: (301)342-9343
2nd TPOC: (301)342-9355

** TOPIC AUTHOR (TPOC) **

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