Innovations in Designing Damage Tolerant Rotorcraft Components by Interface Tailoring
Navy STTR 2019.A - Topic N19A-T003
NAVAIR - Ms. Donna Attick -
Opens: January 8, 2019 - Closes: February 6, 2019 (8:00 PM ET)


TITLE: Innovations in Designing Damage Tolerant Rotorcraft Components by Interface Tailoring


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

ACQUISITION PROGRAM: PMA276 H-1 USMC Light/Attack Helicopters

OBJECTIVE: Develop and demonstrate innovations in tailoring ply interfaces to improve damage tolerance and durability of rotorcraft components.

DESCRIPTION: Composites offer unique opportunities for designing rotorcraft components that are not offered by traditional monolithic materials. In addition to structural efficiency, composites also offer improved fatigue resistance than metal and superior resistance to environmental effects. However, composite fabrication design and fabrication are more challenging, especially for high-performance designs involving interfaces of multiple material systems (e.g., glass/epoxy and carbon/epoxy in the same component). Interlaminar failure often dictates the design. Ply drop-offs are usually the location of damage initiation sites. If more than one composite system is used (e.g., carbon/epoxy with glass/epoxy), the interface between the two systems is a weak point and a potential site for damage initiation. These areas often have sharp strain gradients and/or residual thermal stresses due to Coefficient of Thermal Expansion (CTE) mismatch. Tailoring the interface between adjacent plies by using techniques such as nano-stitching or by embedding graphene sheets has the potential of improving damage resistance by moving the damage to a lower-strain area. Nano tubes and graphene sheets are given only as an example; any non-nano solution will also be considered.

Although it is not required, it is recommended that the small businesses work with the original equipment manufacturers (OEMs) to ease future transition.

PHASE I: Define and develop a concept to use interface tailoring and demonstrate feasibility at a coupon level. It is recommended that the feasibility be demonstrated by qualitative and mechanical testing. Suggested ASTM standards for testing include D2344, D0339, and D5379. The tests are not mandatory and the offerors can propose tests best suited for their solution. The Phase I effort will include prototype plans to be developed under Phase II.

PHASE II: Using results from Phase I, prove the concept at a component level such as a rotorcraft component that sees complex out of plane loads and is prone to delamination in a lab or live environment. Potential component includes but not limited to rotorcraft flex-beams, composite cuff and yoke. Refer to JSSG-2006 [Ref 1] for general requirements for Navy structures.

PHASE III DUAL USE APPLICATIONS: Mature the technology for possible insertion in Future Vertical Lift (FVL). Concurrently, it is recommended that the proposer work with an existing OEM for potential transition to an existing platform. The cost pressures in commercial aviation are even more constrained 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.


1. JSSG-2006, Department of Defense Joint Service Specification Guide: Aircraft Structures, 30 October 1998.

2. “NanoStitch.” n12 Technologies, Cambridge, MA.

3. ASTM D5379 / D5379M - 2. “Standard Test Method for Shear Properties of Composite Materials by the V-Notched Beam Method.” West Conshohocken: ASTM International, 2018.

4. ASTM D2344 / D2344M - 16.  “Standard Test Method For Short-Beam Strength of Polymer Matrix Composite Materials and Their Laminates.” West Conshohocken: ASTM International, 2018.

5. ASTM D3039 / D3039M - 17. “Standard Test Method For Tensile Properties of Polymer Matrix Composite Materials.” West Conshohocken: ASTM International, 2018.

6. Villoria, R., Hallander, P., Ydrefors, L., Nordin, P., and Wardle, B.  “In-plane Strength Enhancement of Laminated Composites Via Aligned Carbon Nanotube Interlaminar Reinforcement.” Composites Science and Technology, 2016, pp. 33-39.

KEYWORDS: Composites Design; Composites Manufacturing; Interfacial Reinforcement; Damage Tolerant; Ply Drop-Off; Rotorcraft Component



These Navy Topics are part of the overall DoD 2019.A STTR BAA. The DoD issued its 2019.1 BAA STTR pre-release on November 28, 2018, which opens to receive proposals on January 8, 2019, and closes February 6, 2019 at 8:00 PM ET.

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