Like engineers in other transportation industries, commercial aircraft designers are racing to create lighter weight, less costly components while maintaining structural integrity. New materials for manufacturing structural and non-structural components are being developed for interior and exterior applications. These include lighter, stronger, and faster-curing carbon fiber and glass composites, and lighter weight metals and alloys. For interiors, new constructions contain microcellular or honeycomb cores or glass bubbles.
Although composites, especially carbon fiber-based, receive a lot of attention, most structural materials in commercial aircraft are still metals, primarily aluminum and its alloys. According to a new study of lightweighting materials in transportation, in many cases, aluminum is the best material for the short term, since it doesn't disrupt manufacturing patterns. The Lux Research report, "Structural Navigation: Optimizing Materials Selection in Automotive and Aerospace," contains multiple decision-tree analyses. These help determine which materials are best used where in several transportation applications, now and during the next 10 years.
Components made of microcellular polyurethane elastomers, such as this jounce bumper or spring aid made of BASF's Cellasto, can reduce weight, absorb shock, and dampen sound and vibration in aircraft interiors.
In the last five to seven years the aerospace industry has learned that carbon fiber doesn't make sense for every application, said Tony Morales, Alcoa's global marketing director for aerospace and defense rolled products:
From the design and build standpoint, aluminum has high performance and low weight at a lower cost than the alternatives. It doesn't require building new factories, new hangars, new supply chains, new ovens, or doing R&D for new inspection and repair techniques. In metal wing structures, you only have mass where it's needed. In carbon fiber it's harder to fine-tune complex shapes.
Alcoa is working with aircraft OEMs on new structural approaches that combine selective reinforcement techniques and advanced structural concepts with new materials.
Its third-generation aluminum-lithium alloys, introduced last year, have higher strength-to-weight ratios and better stiffness and corrosion resistance. Their densities range from 2 percent to 10 percent lower than traditional aluminum, depending on the amount of lithium. Most of the new generation is around 5 percent lower density. They are being used in extrusions, forgings, and sheet and plate applications in several aircraft structures, including airplane wings and fuselage. Alcoa expects to reach full production by the end of 2012 in two facilities, and by the end of 2014 in its Lafayette, Ind. facility.
Composite makers are also involved in major efforts to improve their materials as competition with aluminum alloys heats up. The main areas of development include improving strength and toughness, adapting component shapes to specific loads or environmental conditions, and reducing costs by finding better processing methods to speed up laydown rates, said Carmelo Lo Faro, Cytec's vice president of technology.