Among the next-generation narrow-body passenger aircraft materials, aluminum-lithium alloys are likely to surpass composite materials and become the first choice for narrow-body passenger aircraft. Aluminum-lithium alloys are lighter than traditional aluminum, and between composite materials and new lightweight aluminum alloys, aluminum-lithium alloys seem to have more advantages.
There is no doubt that carbon fiber composites have made great strides in commercial aircraft, mainly because of their light weight and high strength. The Boeing 787 is the first wide-body airliner to use composite materials for the fuselage and key structural components of the aircraft. The Airbus A350XWB is also not far behind.
However, with the rise of new metal materials, aluminum-lithium alloys have also begun to emerge. For example, Airware from Alcan, a subsidiary of Rio Tinto. These new alloys are significantly lighter than traditional aluminum structures, have significantly improved corrosion resistance, and cost less than composites.
Why is the application of aluminum-lithium alloys more than composite materials in narrow-body passenger aircraft?
Operational differences:
Compared with wide-body airliners, narrow-body airliners mainly fly short-haul routes, requiring frequent takeoffs and landings every day. This requires stronger aircraft fuselages to withstand the stress of multiple takeoffs and landings per day, as well as the pressurization of the cabin cycle.
damage tolerance
Aircraft fuselage is more susceptible to ground damage, usually caused by luggage loading carts and carts accidentally hitting the fuselage during the course of day-to-day operations. Although carbon fiber composites are strong, they can easily cause damage to the inside of the fuselage rather than the outside. Therefore, non-destructive testing, such as the use of X-ray equipment, is required to determine whether damage has occurred, and whether the damage is severe enough to require repair to ensure the integrity of the fuselage structure.
In the case of aluminum-lithium metal, damage can be determined by a simple inspection. Just like traditional aluminum. Patching can be done in traditional ways.
manufacturing process
Composites require curing in an oven or autoclave and take a radically different process than traditional aluminum to install parts on an aircraft. Aluminum-lithium alloys do not have such a problem.
cost and durability
There are also differences in cost and durability between the two materials. Composite materials cost more than aluminum, but are more resistant to corrosion. Although aluminum-lithium alloys are more resistant to corrosion than conventional aluminum, they can still corrode in certain operating environments. In contrast, composites can also delaminate if moisture gets into surface defects. From a durability standpoint, the durability of composites remains to be seen.
Environmental issues
Aluminum-lithium alloy is a material that is completely recyclable and can be recycled into new aircraft at the end of the aircraft's life. Carbon fiber composites include carbon fiber, a metal mesh for lightning protection, wrapped in resin. High-strength carbon fibers and metal mesh are difficult to extract from the material.
safety
Aluminum-lithium materials and composites can change a lot in collisions. Aluminum is less rigid than carbon fiber composites and absorbs impact during a crash. In contrast, carbon fibers tend to shatter after a violent collision, especially when high-strength carbon fibers separate from the resin on impact.
In the event of an extreme collision, whether carbon fiber composite materials can provide passengers with the same level of protection as aluminum alloys, especially in the event of a fire, it is necessary to consider the toxicity of the material and the probability of fire entering the cabin through gaps.