TECHNOLOGY AREA(S): Air Platform, Ground/Sea Vehicles, Materials/Processes

ACQUISITION PROGRAM: PMA-262 Persistent Maritime Unmanned Aircraft Systems

OBJECTIVE: Develop innovative approaches to manufacture large component aircraft structures using nanostructured heaters.

DESCRIPTION: The Navy is seeking an innovative aircraft manufacturing method to produce primary structures for future air platforms using nanostructured heaters. This approach should generate temperatures up to 500° Celsius (C) reliably and in a stable manner, sufficient to manufacture thermosets and thermoplastic parts. This innovative method should not require autoclave or oven cure. This approach will target aerospace-grade, carbon epoxy (C/Ep) laminate as its initial validation material.

A principal cost driver in making quality composite parts is the need for an autoclave. An autoclave provides the temperature and pressure needed to fabricate parts made from the family of aerospace resins such as Carbon/Epoxy (C/Ep) and Carbon/BMI systems. While the autoclave cure remains the gold standard, it has limitations on part sizes and high costs associated with the process. For large parts, getting time in the autoclave is often the bottleneck. There has been sustained research in developing resin systems and fabrication processes that allow composites to be cured without pressure in a vacuum bag, but still in an oven. One aerospace manufacturer has estimated that out-of-autoclave processes can save it up to 50% of manufacturing costs of fuselage and nacelle components and be up to 40% quicker by eliminating idle time waiting for an autoclave [Ref 3]. Recent developments in nanostructured heaters show promise in producing temperatures as high as 500°C and can be used to produce high-quality parts. Such heaters can act as envelope heaters or can be embedded in lamina interfaces where, besides providing heat, these nanostructure heaters also aid in resin impregnation. Such systems have the potential of producing parts of autoclave quality without requiring an oven. Since no autoclave or oven is needed, these heaters have the potential of curing very large parts, with length dimensions exceeding 100 feet, which typically will not fit in an autoclave. While fabrication of such a large part is not required, it is expected that at the end of the program the scalability of the process to such dimensions will be demonstrated.

Although not required, it is recommended that offerors work with original equipment manufacturers (OEMs).

PHASE I: Develop the concept in the context of eventual demonstration of producing an airframe fuselage component. Demonstrate the feasibility of the approach for an aerospace grade C/Ep laminate by comparing the quality and mechanical properties of a nanoheater cured composite to a conventionally cured composite. Suggested standards are ASTM D2734 for porosity measurement, and ASTM D234, D3039, and D5379 for mechanical property testing. These tests are not mandatory and the offeror can propose the tests best suited for the proposed technology. Develop Phase II plans for producing prototype(s).

PHASE II: Build upon the results from Phase I, fabricate and test a prototype subcomponent representative of a fuselage panel or a control surface of a Naval air platform, such as a wing panel. The demonstration article should be at least 10 ft by 5 ft and have a contour representative of the part selected.

PHASE III DUAL USE APPLICATIONS: Transition the developed solution to an existing platform, conceivably in conjunction with the OEM, for potential cost savings. The secondary approach will be to transition the nanoheater curing technology to Future Vertical Lift (FVL). The cost pressures in commercial aviation are tighter than in military aviation. Commercial aviation is also leading the way in replacing metallic airframe structures with composites. Thus, the technology will be highly applicable to commercial aviation for reducing production costs.

REFERENCES:

1. Lee, J. et. Al. “Aligned carbon nanotube film enables thermally induced state transformations in layered polymeric materials.” ACS Appl Materials & Interfaces, 2015, 7(16), pp. 8900-8905. doi:10.1021/acsami.5b01544

2. Nguyen, N, et. Al. “In Situ Curing and Out-of-Autoclave of Interply Carbon Fiber/Carbon Nanotube Buckypaper Hybrid Composites Using Electrical Current.” Advanced Engineering Materials, 2016, 18 (11), pp. 1906-1912. doi: 10.1002/adem.201600307

3. Derber, A. “Out of Autoclave, Into Production.” MRO-Network.com. http://www.mro-network.com/manufacturing-distribution/out-autoclave-production

4. ASTM D2734-16, Standard Test Methods for Void Content of Reinforced Plastics, ASTM International, West Conshohocken, PA, 2016, www.astm.org

5. ASTM D2344 / D2344M-16, Standard Test Method for Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates, ASTM International, West Conshohocken, PA, 2016, www.astm.org

6. ASTM D3039 / D3039M-17, Standard Test Method for Tensile Properties of Polymer Matrix Composite Materials, ASTM International, West Conshohocken, PA, 2017, www.astm.org

7. ASTM D5379 / D5379M-12, Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method, ASTM International, West Conshohocken, PA, 2012, www.astm.org

KEYWORDS: Composite Fabrication; Out of Autoclave; Out of Oven; Large Composite Parts; Nanoheaters; Energy Efficient