Role of Advanced Materials in Modern Aero Engines

Advanced materials have been a key technology throughout the history of the aero engine, continually contributing to its increasing effectiveness. The constant drive for increased performance necessitates materials that demonstrate not just ever-increasing high-temperature strength but also decreasing density for lower weight and higher thrust-to-weight ratios. As current materials reach the limits of their potential, new materials are emerging that offer significant improvements in capability, or, to a military operator, the potential edge in combat situations. The composition of the aero engine has changed radically in the last 40 years. Until around I960, steels accounted for about 60% by weight of the engine. They now represent little more than 10%. The presence of aluminium alloys has also vastly diminished. With the latest generation of high bypass turbofan aero engines, titanium alloys and nickel superalloys account for up to 75% of the engine weight. Titanium based alloys offer mechanical strength and light weight, and are used in fan and compressor blade and disc manufacture. Nickel superalloys have superb high-temperature capability, and are heavily used in the turbine 'hot-end' section of the engine. Composite materials have also steadily increased in use and, while not yet fulfilling eaarly predictions, they have overtaken aluminium in overall usage and make up a large proportion of the engine's static structures. New materials, such as titanium and nickel aluminides and advanced composites, can offer a step change in capability over today's alloys. However, the aero engine market is cost driven, so development of existing alloys remains vital, as the challenge of demonstrating performance improvements and simultaneous cost reduction via new advanced materials is undertaken.