DESCRIPTION: The attraction of 3D braided architecture is that it is inherently damage tolerant and can produce near net-shape products; however, these improvements usually come with a stiffness penalty. Additionally, there are limitations on the geometries that can be braided near-net shape. This is particularly true for solid cross-sections where the geometry and shape change along the braiding axis. Conventionally, complex shapes are produced either by over braiding on an insert or by machining an oversized braided composite. The first approach results in a weak interface between the insert and the braid. The second approach is not a near net-shape and results in increased scrap and a weaker structure, resulting from the cut fibers on the surface. Innovations are sought in braiding technology that can address these deficiencies and successfully produce complex rotorcraft components. In addition to technical maturity, scalability of the approach, and automation of the process are important. These criteria will be used during the evaluation process.

PHASE I: Define and develop a concept for an innovative braiding methodology and establish the feasibility of the methodology to fabricate a rotorcraft airframe or rotor component. Feasibility can be established by fabricating coupons that are representative of geometry and cross-section changes of a rotorcraft component. Candidate components may include, but are not limited to, fuselage frame elements, rotor hub, and rotor yoke sub-assemblies. The Phase I effort will include prototype plans to be developed under Phase II. In choosing the components, please refer to JSSG-2006 [Ref 3] and AR-56 [Ref 2] for overarching requirements for Navy rotorcraft structures.

PHASE II: Demonstrate the production methodology by producing a prototype component in a lab or live environment.

PHASE III DUAL USE APPLICATIONS: Finalize and mature the technology for transition and insertion into Future Vertical Lift (FVL) for production fuselage or rotor hub components. The technology will be highly applicable to commercial aviation for reducing production costs by replacing metallic airframe structures with composites.

REFERENCES:

1.   Chou, T.-W. and Ko, F. Textile Structural Composites. Elsevier Science: Amsterdam, 1988. https://onlinelibrary.wiley.com/doi/pdf/10.1002/adma.19890011016

2.   Airworthiness Certification criteria (AR-56 Structural Design Requirements (Helicopters)). Department of Defense, 2004. http://everyspec.com/MIL-HDBK/MIL-HDBK-0500-0599/MIL_HDBK_516A_2069/

3.   Joint Service Specification Guide Aircraft Structures. Department of Defense, 1998. http://everyspec.com/USAF/USAF-General/JSSG-2006_10206/

4.   Kyosev, Y. Advances in Braiding Technology: Specialized Techniques and Applications. Elselvier: Cambridge, 2016. https://www.sciencedirect.com/science/book/9780081009260

5.   Lam, Hoa. �3-Dimensionally Braided Ceramic Matrix Composite Fastener.� Defense Manufacturing Conference. (Uploaded to SITIS 4/19/2019)

KEYWORDS: Composites Manufacturing; Near Net Shape Manufacturing; 3D Braiding; Rotorcraft Airframe Structure; Composite Hub; Composite Yoke