N112-149 TITLE: Advanced Carbon Nanotube Forms for Composite Structural Applications

TECHNOLOGY AREAS: Materials/Processes

ACQUISITION PROGRAM: None

OBJECTIVE: To develop new carbon nanotube structural products that are amenable for seamless integration with existing structural composites manufacturing methods and that will provide significant increases in through thickness strength of laminated composite structures. The ultimate goal is to enhance the performance and endurance of structural composites by introducing small amounts of CNTs in to critical areas, with relative ease and minimal cost impact.

DESCRIPTION: By now it has been amply demonstrated that carbon nanotubes (CNTs) can produce polymer (epoxy, vinyl ester and others) nano-composite materials with mechanical properties (in-plane and out-of-plane) that are significantly better than those of the best aerospace grade carbon fiber reinforced material, albeit at relative small sizes due to the large CNT cost when used at high concentrations. On the other extreme, very small concentrations of CNTs, acting as a secondary reinforcement phase and placed at the appropriate location, have been shown to significantly enhance some of the mechanical properties of structural composites with a minimum cost impact. This topic seeks to develop new cost effective CNT forms (for example pre-preg tapes, pre-preg mats, sprays, or other advanced concepts) that can be applied to well defined hot spots and are amenable with existing PMC manufacturing processes. The intent is not to apply these new forms throughout the entire composite structure, but only in localized areas that could benefit from additional out of plane reinforcement such as around fastener holes, ply drop-offs and other mentioned previously.

Special interest will be placed on those teams that can manufacture and process CNTs since it is well know that the best performance of these materials is achieved when the quality of the CNT is appropriately controlled (such as number of CNT walls, the number of defects on the surface of the CNT, the length of the CNTs, functionalization of the CNTs, resin compatibility, dispersion of the CNTs and other properties).

PHASE I: Develop at least one new carbon nanotubes (CNT) form. Demonstrate how it is applied during a manufacturing trial and characterize its structural performance under an open hole compression test (OHC). Optimize the CNT form (CNTs length, form thickness, length and width, processing parameters and other form parameters) in terms of OHC strength and/or interlaminar shear strength.

PHASE II: Expand on that CNT form to include other sizes and configurations. Investigate scale-up options and start developing manufacturing and commercialization plans. In coordination with Navy engineers, a target demonstration application will be identified and executed.

PHASE III: In coordination with Navy engineers, a target demonstration will be performed on a representative structural article and resulting test data evaluated to a baseline configuration. The manufacturing processes also will be further optimized.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The commercial aviation and shipping industry would benefit significantly from a product of this nature as well. The same problems are experienced in our Naval platforms (ships, subs and aircraft) also occur in commercial counterparts. For example, impact related delaminations, dis-bonds, fastener hole damage, and heat/moisture induced delaminations are common to all In Service composite structures.

REFERENCES:
1. "Processing a glass fiber reinforced vinyl ester composite with nanotube enhancement of interlaminar shear strength", J. Zhu, A. Imam, R. Crane, K. Lozano, V. Khabashesku, E.V. Barrera; Composites Science and Technology; v67, n7-8, June 2007 p. 1509-151

2. "Joining prepreg composite interfaces with aligned carbon nanotubes", Enrique J. Garcia, Brian L. Wardle*, A. John Hart; Composites: Part A 39 (2008) 1065-1070

3. "Functionalization of Carbon Nanotube Buckypaper for High-Performance Composites Applications," Jianwen Bao, Qunfeng Cheng, Xianping Wang, Richard Liang, Chuck Zhang, Ben Wang, High Performance Material Institute (HPMI), Department of Industrial and Manufacturing Engineering.

KEYWORDS: Carbon Nanotubes, CNT, Composite Materials, Composite Patches, Peel strength, interlaminar shear strength

** TOPIC AUTHOR (TPOC) **

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