John Liu

Advanced Aluminium and Hybrid Aerostructures for Future Aircraft

Alcoa has made a fundamental shift in its aerospace R&D program, broadening its scientific and engineering portfolio by creating an integrated, strategic, long-term initiative. The ultimate goal is to help re-define the future performance, cost and value of the metallic and hybrid aerostructures that the company feels will be required to meet the mission requirements of tomorrow’s aircraft. Having intensely studied various structural options, Alcoa believes Hybrid Structural Assembly optimized with a combination of Advanced Aluminum and Hybrid Components offer the best opportunities to maximize structural performance. Not only do the new alloys, notably 3rd Generation Al-Li alloys and high strength and high toughness 7xxx alloys provide structural performance enhancements, they also offer dramatic improvements in corrosion resistance. In this paper, several advanced alloys and structural concepts targeted for next generation wing and fuselage applications and large scale test article results supporting Alcoa’s optimism for Advanced Metallic and Hybrid Structures are reviewed.

A New Paradigm in the Design of Aluminum Alloys for Aerospace Applications

Property requirements which drive material development for aircraft structures have evolved over the years. In order to take advantage of the enhanced material characteristics to improve performance and lower the overall installed component cost of the aircraft, concurrent consideration of design, materials development, and manufacturing is required. This in turn requires close interaction between the material producer and the Original Equipment Manufacturer (OEM). An example of such a teaming approach is the Integrated Product Teams (IPT). For effective functioning of the IPT, the material producers must better understand how material behavior translates to sub-component performance through the use of design tools. Examples of such design tools developed by Alcoa are given. Case studies for wing and fuselage structures are illustrated. More structurally representative testing methods must be developed to supplement these analytical tools. These tools and structurally representative test methodologies are critical enablers to meet the overall needs of the todays OEM including higher performance, less weight, lower manufacturing and assembly costs, lower aircraft maintenance costs and a higher level of safety.

Effect of precipitates on plastic anisotropy of polycrystalline aluminum alloys

The effects of crystallographic texture and precipitate particles on macroscopic anisotropy in aluminum alloys were investigated. In order to simultaneously consider the effects of crystallographic texture and precipitate distribution on macroscopic anisotropy, predictions of plastic properties were carried out using an anisotropic yield function based on texture and a combined isotropic-kinematic hardening rule based on the precipitate volume fraction, shape and habit planes. The model was applied to the case of a recrystallized, extruded binary Al-3wt%Cu alloy that was deformed in uniaxial compression in different directions. Gaussian distributions of grain orientations around ideal texture components typical for aluminum alloys sheets and plates were generated with computer simulations. The isotropic-kinematic hardening rule determined for the Al-3wt%Cu binary alloy was used to assess the influence of precipitates on yield stress and plastic strain ratio (r value) anisotropy for these ideal textures in aluminum alloys.