TECHNOLOGY AREAS: Air Platform, Materials/Processes, Weapons

ACQUISITION PROGRAM: Joint Strike Fighter Program Office, Airframe IPT, ACAT I D Program

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Develop a cost-effective controllable very rapid curing resin and pre-preg system for galvanic barrier or isolation ply restoration on complex pre-cured and machined carbon composite part surfaces. The system is to be based on proven epoxy chemistry resins for barrier or isolation ply applications with type "E" glass 108 style fiberglass cloth.

DESCRIPTION: New developments in very rapid cure resin systems have overcome limitations of legacy properties associated with these novel resin systems; including, but not limited to, brittleness, aircraft fluid and environmental sensitivity, unpredictable cure, and low glass transition temperature. Rapid resin cure is considered to be orders of magnitude less than current thermal cure processes while eliminating many time consuming processing steps; with no post processing required. An objective of this effort will be to develop a system that includes the epoxy based rapid and controllable cure resin and pre-preg processes needed to adequately impregnate the 108 style fiberglass cloth.

The proposed epoxy based rapid cure resin system with specified 108 style fiberglass cloth should meet the specific application of restoring the galvanic barrier or isolation ply corrosion protection on machined carbon composite surfaces that meets DoD aerospace fighter requirements. The final product form of the pre-preg must meet desired properties such as aerial weight, density, uniformity, thickness, etc. In addition, the pre-preg must meet the glass transition requirement of 375 F-dry via dynamic mechanical analysis (DMA) and demonstrated resistance to standard DoD aircraft fluids and environments. Final pre-preg properties will be assessed to ensure adequate performance for this application. Storage, handling and shipping of candidate pre-preg material should require no special environmental considerations beyond manufacturer packaging to remain stable and usable for processing - for example, no freezer/dry ice storage, but may require a protective package supplied via manufacturing process to limit cure from ambient light. The intention is for this candidate pre-preg material to be stored within a composite manufacturing center with typical constraints such as no direct sunlight and at temperatures typically found at an aerospace composite manufacturing center.

The candidate pre-preg along with the pre-preg life should include storage life, open mold life and be sufficient to meet the intentions of this program; allow for lay-up and subsequent rapid cure on large complex carbon composite parts to restore the galvanic corrosion barrier. Shelf life will be proven at the maximum extent possible within the capabilities of resin system, and be measured in tens of months rather than days or weeks.

PHASE I: Develop, perform analysis and perform optimization trials for a candidate baseline rapidly curing resin system. Demonstrate feasibility to pre-preg the resin while meeting physical and structural properties of the pre-preg and laminate. Demonstrate viscosity versus temperature evaluations of the resin and design a pre-preg process that will allow for flow and coating on the 108 style fiberglass cloth and cool sufficiently during the roll process to form an aerospace quality product with consistent thickness and resin content.

PHASE II: Develop and refine epoxy based rapid and controllable cure resin and pre-preg processes to provide for consistent product form on 108 style fiberglass cloth. This very rapid cure resin and glass cloth material could potentially be vacuum bag capable prior to and during cure process. Pre-preg properties will be assessed and provided to ensure adequate performance that meets this application; such as potentially, resin content, fiber area weight, volatile content, tack, cured ply thickness, density, glass transition temperature, adhesion, microcrack resistance, etc. Other woven fiber reinforcement materials may be explored for pre-pregging during this phase.

PHASE III: Design, fabricate, and test a pre-preg system with the optimized resin system developed in previous phases. The system must have the final production environment, limitations, and quantities required in mind during this phase of the program. Handling properties of the final pre-preg must be manufacturing friendly, and be able to be used with the standard set of tools and procedures available in a typical aerospace clean room of a composite manufacturing facility. Provide adequate system description and specifications to effectively transition the technology to the final pre-preg manufacturer.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial aircraft manufacturers, automotive, and marine vehicle repair shops will benefit from the technology developed under this effort.

REFERENCES:
1. SAE-AMS 3824C - Glass Cloth.

2. Shi, W and Ranby, B., "UV Curing of Composites Based on Modified Unsaturated Polyester," Journal of Applied Polymer Science. Vol 51, 1129-1139, 1994.

3. Zahouily, K. and Decker, C., "High-Performance UV-cured Composite and Nanocomposite Materials," JEC Composites Magazine. Vol 32, 75-79 May 2007.

4. Allred, R. E.; Hoyt, A. E.; Harrah, L.A.; McElroy, P.M.; Scarborough, S.; Cadogan, D. and Pahle, J.W., "Light Curing Rigidizable Inflatable Wing," 45th AIAA/ASME/ASCE/AHS/ASC Structures, Structures Dynmaics and Materials Conference; Palm Springs, CA Apr. 19-22, 2004.

5. Allred, R.E.; Hoyt, A. E.; Harrah, L.A.; Scaraborough, S.; Mackusick, M. B. and Smith, T.,"Light Rigidizable Inflatable Wings for UAVs: Resin and Manufacturing Development," 46th AIAA/ASME/ASCE/AHS/ASC Structures, Structures Dynamacs and Materials Conference; Austin, TX Apr 18-21, 2005.

6. Mirle, S. K. and Kumpfmiller, R. J., US Patent 5,418,112, (1995)
"New Sandia UV LEDs emit short-wavelength, high-power output," Sandia National Laboratories Press Release, November 18, 2003.

7. "UV LEDs Have Multiple Uses," Sandia National Laboratories Press Release, November 18, 2003.

8. Ryan, A. J.; Valdya, U. R.;Mormann, W. and Macosko, C. W.," Networks by Fast Polymerization" Polymer Bulletin. Vol 24, 521-527, 1990.

9. Hoyt, A. E.; Harrah, L. A.; Allred, R. E. and McElroy, P. M.,"Rigidization on Command (ROC) Resin Development for Lightweight Isogrid Booms with MLI, " 33rd Intl Conf on Environmental Systems, Vancouver, BC, July 2003, technical paper series 2003-01-2342.

10. Jansen, J. F. G. A.; Dias, A. A.; Dorschu, M. and Coussens, B., "Fast Monomers: Factors Affecting the Inherent Reactivity of Acrylate Monomers in Photoinitiated Acrylate Polymerization," Macromolecues, Vol 36, 3861-3873, 2003.

11. Rix, B. A. and Bulluck, J. W., "Ultraviolet Radiation Cured Acrylate for Aircraft Composite Field Repairs," www.radtech.org, Radtech Report Nov/Dec 2004.

12. Black, S., "Technologies for UV Curing of Composite Laminates Demonstrated," www.compositesworld.com, April 2004.

KEYWORDS: Rapid cure resin pre-pregging; galvanic barrier ply restoration; automated pre-preg system; optimized rheology; quality assurance; glass transition.

** TOPIC AUTHOR (TPOC) **

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