Review of F-111 Structural Materials
DEFENCE SCIENCE AND TECHNOLOGY ORGANISATION VICTORIA (AUSTRALIA) AERONAUTICAL AND MARITIME RESEARCH LAB
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The RAAF is now the sole operator of the F-111 and current plans for the fleet will keep the aircraft in service until 2020. The F-111 is a structurally complex aircraft, and its swing-wing geometry in particular requires materials of ultra high strength to handle expected loadings. In particular, the D6ac steel used in most of the critical components in the aircraft was subjected to rigorous research efforts in the early 1970s to better characterise material performance in fatigue. This report summarises many of these efforts to characterise the main alloys in the airframe, namely D6ac steel and aluminium alloys 2024-T851, 7079-T651, and 7075-T6. The major goal is to study the available data for these critical F-111 materials, evaluate the completeness of the existing data sets and make recommendations for research efforts necessary to ensure that the F-111 fleet is operated as safely and economically as possible until retired. Particular attention is payed to the fact that the RAAF now uses JP-8 fuel rather than the original JP-4 fuel. Short crack behaviour from corrosion damage will likely be a concern for the F-111, particularly in the D6ac steel. Stress corrosion cracking is likely to continue to be the biggest problem for the 7xxx-series aluminium alloy components and will have to be monitored carefully.
- Attack and Fighter Aircraft