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In-Plane Conductivity Improvement to Fiber Reinforced Composite Materials


OBJECTIVE: Develop a lightweight solution to improve the in-plane thermal conductivity of carbon fiber reinforced polymer composite materials that is either directly integrated into the material, co-cured within the fabrication process of a composite structure, or secondarily bonded to the structure without significantly affecting the structural capabilities of the material. DESCRIPTION: Fiber reinforced polymer composites exhibit high specific strength and stiffness making them extremely attractive in many structural applications. Unfortunately, for applications such as missile airframes and guidance electronics units, the insulative nature of the polymer matrix can cause issues due to the packaging of high power electronics. As the state of the art in missile electronics continues to evolve, it becomes increasingly important to be able to remove heat from the structure to ensure electronics survivability. Conventional aerospace materials such as aluminum offer great advantages with respect to thermal management due to their high isotropic thermal conductivity (usually in excess of 130 W/m- degrees C) and favorable specific heat capacity. Carbon fiber reinforced epoxy composites offer a stronger, lightweight, corrosion resistant structural alternative to aluminum; however, the aforementioned thermal properties make them unfavorable in applications requiring thermal management. The goal of this three-phase SBIR process, therefore, is to address the thermal limitations of composites and deliver a novel, lightweight material solution to improving the in-plane thermal conductivity of composite structures as a potential replacement for aluminum missile structures. The nature of this application involves thin skin composite structures (up to 0.1"thick) where the fibers are oriented in the x-y direction. It has been shown that moderate increases to the in-plane thermal conductivity can have drastic effects on the overall ability of the structure to manage waste heat loads (often in excess of 50 W); this is largely due to the large surface areas used as convective surfaces. This topic addresses one of the top 5 Army Science and Technology Challenges of overburdened soldiers that must carry heavy close combat weapon systems. Man-portable systems such as Javelin benefit from lightweight and reduced volume composite structures. There is an immediate need for lightweight advanced material systems that lessen the weight on burdened soldiers, while still providing enhancements to structural performance and maintaining effective thermal management capability. PHASE I: Identify potential approaches to integrating high in-plane thermal conductivity into composite structures. Assess feasibility of various methodologies from a fabrication standpoint. Develop analytical tools to model various methodologies and understand them from a performance standpoint. Demonstrate in-plane thermal conductivity enhancements that exceed 10 x the conductivity of the composite baseline (at ~5 W/m- degrees C) with less than 5 % degradation in tensile and compressive strength values of composite baseline using coupon level experiments. PHASE II: Develop, test and demonstrate a prototype composite missile airframe structure, of the geometry dimensions provided by the customer, possessing high in-plane thermal conductivity. Test the thermal and structural performance of the structure using stimulant missile electronics to represent waste heat loads and representative thermal and mechanical system configurations to be provided by the customer. Test the performance under relevant environmental conditions. Demonstrate improvements in thermal performance over structurally equivalent aluminum cylindrical structures. TRL: (Technology Readiness Level) TRL Explanation Biomedical TRL Explanation TRL 6 - System/subsystem model or prototype demonstration in a relevant environment PHASE III: Weight reduction and affordable manufacturing processes is of great importance in many aviation and missile structures. The awardee will deliver a material solution that can be easily integrated into any carbon composite structure using conventional composite processing approaches including, but not limited to, filament winding, hand layup, and tube rolling. This will enable transition of the technology to defense and aerospace users. This is considered a pervasive technology and can be applicable to future Army weight reduction efforts for systems with thermal management issues including TOW, Javelin, JAGM, and multiple unmanned and manned aerial vehicle platforms. REFERENCES: 1) Springer, G. S., S.W. Tsai, Thermal conductivities of unidirectional materials, Journal of Composite Materials, v. 1, n. 2, p. 166-173, 1967. 2) Rolfes, R., U. Hammerschmidt, Transverse thermal conductivity of CFRP laminates: A numerical and experimental validation of approximation formulae, Composites Science and Technology, v. 54, p. 45-54, 1995. 3) Pilling, M. W., B. Yates, M.A. Black, P. Tattersall, The thermal conductivity of carbon fibre-reinforced composites,"Journal of Materials Science, n. 14, p. 1326-1338, 1979. 4) Owens, A.T., Thermal management in fiber reinforced composite applications, Proceedings of the 2008 International Conference on Composite Materials, Edinburgh, UK, 2008.
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