Development of High Toughness Sheet and Extruded Products for Airplane Fuselage Structures

Abstract

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 2055 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 on resulting microstructures is discussed. Introduction Airplane fuselage skin materials have evolved throughout the history of aviation as the performance requirements have changed. The first airplane fuselages consisted of a wood frame covered in fabric. There were very little performance requirements for the fabric skin of the airplane other than to shield the pilots from the wind. Aluminum eventually replaced fabric covered wood for airplane fuselages, but the development of a metallic airframe was met with many significant challenges.