N093-171 TITLE: Innovative Approaches for Enhancing Interlaminar Shear Strength of Two - Dimensional (2D) Composite Reinforced Flexbeams and Yokes

TECHNOLOGY AREAS: Air Platform, Materials/Processes

ACQUISITION PROGRAM: PMA-261, CH-53K Heavy Lift Helicopter Program

OBJECTIVE: Develop effective low-cost methods for improving interlaminar shear strength of two-dimensional 2D flexbeams and yokes for rotor systems.

DESCRIPTION: The CH-53K heavy lift and other rotary wing military platforms are targeting composites for rotor hub applications with an ultimate goal of weight reduction. However, concerns exist over acquisition cost, reliability, durability and life expectancy. Current rotor hub components are typically fabricated with 2D woven carbon and fiberglass fabric reinforcement. 2D components have been found to be life-limited in high cycle and fatigue environments due to inherently low matrix dominated interlaminar shear strengths. Three-dimensional (3D) fiber architectures offer the potential for increased durability by enhancing the interlaminar and through-thickness mechanical properties; however, their implementation may be cost and weight prohibitive. Attempts at 3D braiding and weaving have resulted in reduced inplane properties and expensive preforms requiring expensive tooling for Resin Transfer Molding (RTM) processes. Innovative solutions are sought for flexbeams and yokes that may include design, process, material, or tooling that would increase the interlaminar shear strength without degrading inplane properties.

PHASE I: Develop an efficient low-cost method or solution for improving the interlaminar shear strength of 2D rotor hub laminates. Demonstrate the feasibility of the developed approach by showing a strength improvement over a baseline material through the fabrication and testing of a limited number of coupon specimens.

PHASE II: Provide practical implementation of a production-scaleable process to implement the method or solution developed under Phase I. Validate the approach through the fabrication and testing of a sufficient quantity of material property test coupons. Develop a prototype of the design for a rotor hub component using the method or solution for improving the interlaminar shear strength.

PHASE III: Transition the approach to CH-53K and additional rotor hub applications both military and commercial.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Advanced composite rotor hub components have the potential to transition to the commercial aircraft market for weight reduction and enhanced life expectancy. The resulting fabrication approach can transition to the energy generation industries for such applications as wind turbines and propeller hubs.

REFERENCES:
1. Lee, Jung J., Ogin, Stephen L., and Smith, Paul A. "Interlaminar Fracture Toughness of Glass Fiber Laminates Additionally Reinforced with Carbon Beads." Composite Materials: Fatigue and Fracture, a symposium sponsored by ASTM Committee D-30 on High Modulus Fibers and their Composites, Dallas, TX, Vol. 5, (24-25, Oct. 1984): 38-60.

2. Cox, J. Rylan and Wilson Christopher D. "Apparent Interlaminar Shear Strength of a Graphite/Epoxy Composite with Carbon Nanofiber Reinforcement." 49th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Material Conference, (7-10 April 2008), Schaumburg, IL.

3. Yamashita, S., Hatta, H., Takei, T., and Sugano, T. "Interlaminar Reinforcement of Laminated Composites by Addition of Oriented Whiskers in the Matrix." Journal of Composite Materials, Vol. 26, No. 9, (1992): 1254-1268.

4. "Methods of Interlaminar Reinforced Refractory Matrix Composites" Posted on MR&D, http://www.m-r-d.com/expertise/composite-materials.htm

5. ASTM D2344, Standard Test Method for Apparent Interlaminar Shear Strength of Parallel Fiber Composites by Short-Beam Method.

KEYWORDS: Polymer Matrix Composite; Two-Dimensional Reinforcement; Rotor Hub Systems, Interlaminar; CH-53K; Cost Reduction; Weight Reduction

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between July 27 through August 23, 2009, you may talk directly with the Topic Authors to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting August 24, 2009, when DoD begins accepting proposals for this solicitation.

However, proposers may still submit written questions about solicitation topics through the DoD's SBIR/STTR Interactive Topic Information System (SITIS), in which the questioner and respondent remain anonymous and all questions and answers are posted electronically for general viewing until the solicitation closes. All proposers are advised to monitor SITIS (09.3 Q&A) during the solicitation period for questions and answers, and other significant information, relevant to the SBIR 09.3 topic under which they are proposing.

If you have general questions about DoD SBIR program, please contact the DoD SBIR Help Desk at (866) 724-7457 or email weblink.