High-Conductivity Composite Heat Sinks for High-Speed Helicopter Gears

Helicopters are very vulnerable to small arms fire during low-flying operations. One major concern is the loss of the primary oil supply in the transmission due to battle damage. The absence of lubricant and subsequent overheating can cause the gears to fail prematurely. For high-speed highly-loaded gears, the heat generated by friction between the transmission gears cannot be effectively dissipated through the current gear material. New gear and heat transfer designs are required to allow high speed gears to operate for thirty minutes after loss of the primary oil supply with no supplemental emergency oil supply. Thermal Products, Inc. proposes to fabricate an aluminum composite heat sink, containing oriented, high-conductivity graphite fibers. The heat sink will be attached within the side of the gear. The high-conductivity graphite fibers will be oriented within an aluminum alloy matrix to transfer heat away from the surface contact regions of the gear toward the cooling fins of the heat sink. The aluminum composite will also exhibit a low thermal expansion to minimize thermal mismatch stresses between the gear and heat sink material. In Phase I, thermal and mechanical properties of the aluminum composite will be determined. A prototype heat sink will be fabricated. BENEFITS: The material will find use as a thermal plane or heat spreading material in high-power electronic applications because of the high conductivity and tailorable thermal expansion. The material may find application in helicopter oil reservoirs.