United States Department of Transportation
i
Effects of New Jet Fuel Exposure on Aerospace Composites – Phase 1 Final Report
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2022-06-01
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[PDF-5.20 MB]
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Edition:Final Report
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Abstract:Composite materials are increasingly used in the aerospace industry as an alternative to metals, primarily due to their high specific mechanical properties (stiffness, strength, etc.), and tailorability. These materials can be subjected to different types of aeronautical fluids during their lifetime. These composites’ exposure to organic fluids such as fuels may lead to matrix swelling and degradation of the composite’s material properties. Hence, evaluating property changes as a function of fuel exposure to ensure aircraft flight safety is of paramount importance. A number of alternative jet fuels have come to focus in recent years to reduce the environmental impact of commercial aviation jet fuels. These blended jet fuels are intended to be used as drop-in fuels in aircraft since they meet existing certification limits required of conventional Jet A fuels. The effects of the following jet fuel blends were investigated in this work; 50/50 Gevo Alcohol-to-Jet (ATJ)/Jet A fuel, 50/50 Synthetic Paraffinic Kerosene (SPK)/Jet A, Amyris 20/80 farnesane/Jet A fuel, and 50/50 S8/Jet A. Note that the first three listed fuels are bio-derived, while the latter is derived via natural gas. The objective of this research is to determine the extent of initial fuel absorption in various composites and investigate the effect of such absorption on the composites’ glass transition temperature Tg and degradation of composite materials’ properties (storage E′ and loss moduli E” and tan δ). Specifically, the changes in Tg were identified as a function of the type of fuel, and duration of exposure. The specimens used were autoclave-cured Hexcel SGP370-8H/8552 eight-harness satin weave carbon/epoxy prepreg specimens with two layups: a four-ply [0/-45/+45/90] layup and a four-ply [0/90]s layup 2 x 0.5 in² specimens, oven-cured Jaco Aerospace & Industrial DMS 2436 Type 1 Class 72 multi-axial warp-knit dry carbon fabric infused with API-1078 epoxy with a seven-ply [45/-45/0/90/0/-45/45] layup 2 x 0.5 in² specimens, and Oven-cured Cytec T40-800 Cycom® 5215 graphite/epoxy prepreg with [0]30 layup 1.5 x 0.5 in² specimens. Specimens were vacuum-dried to remove any remaining moisture in the carbon/epoxy specimens before submersion in various fuels. Fuel-exposed specimens were periodically measured during fuel immersion to evaluate mass gain and when fuel uptake saturation occurs. After a final weighing, fuel- saturated specimens were used in dynamic mechanical analysis (DMA) to investigate of fuel absorption effect on composites’ Tg and dynamic mechanical properties.
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