ABSTRACT
Some aerospace experts have predicted that while current generation aircraft are generally composed of approximately 80 per cent aluminium, this percentage could dwindle to 17 or less during the next two decades as composite materials increasingly become de rigueur in various structural applications. However, competition from composites could also spur significant product improvements in aerospace aluminium and its alloys. This metal still offers many advantages, not least its being 30 per cent lighter and correspondingly cheaper than titanium, and being easier to fabricate than either titanium or many composites. Yet, despite anticipated competition from aluminium and composites, titanium will likely find increasing aerospace applications in the future, especially in high-performance military aircraft and aerospacecraft (the Lockheed SR-71, reputedly the world's fastest aircraft, is constructed almost entirely of titanium). In thermal-structures design, researchers are developing efficient concepts for vehicle wings, fuselage, and ramjet and scramjet aeroengine components using high-temperature resistant titanium alloys and superalloys suitable for cruise speeds in excess of Mach 3. However, titanium is reaching technical maturity as a structural material for some airframe and gas-turbine applications, and the expectation is that future gas-turbine aeroengines will contain less titanium on a weight-to-thrust basis. Figures 23 and 24 illustrate the rather modest advances in strength/density and stiffness/density which can be expected for the light alloys, which are essentially mature technologies in an advanced state of development. The light alloys can be broadly defined to include aluminium, beryllium-aluminium, magnesium, titanium alloys and stainless steels.
