The Evolution of Plate Products for Upper Wing Applications

High specific ultimate strength and high plane stress fracture toughness are primary requirements of aircraft fuselage skins.  The performance of alloys/products used in high performance fuselage applications is first reviewed.  The specific fracture toughness for products such as 2017-T3, 2024-T3, 2524-T3 and 6013-T6, is discussed as a function of their composition and microstructure.  Then the performance of modern Al-Li alloys/products such as 2199 and 2060 sheet and 2099 and C99N extrusions is examined.  It is concluded that the performance of Li containing alloys/products offer significant improvements over non-Li containing conventional fuselage products because of the optimization of strengthening precipitates and grain microstructures. The role of chemical composition and processing on resulting microstructures is discussed.