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