Several
materials can be used for major structures—wings, fuselage, or landing gear,
for example—on different types of aircraft.
Airplane rivets.
● Wood was used on most early
airplanes and is now mainly used on homebuilt airplanes. Wood is lightweight
and strong, but it also splinters and requires a lot of maintenance.
● Aluminum (blended with small
quantities of other metals) is used on most types of aircraft because it is
lightweight and strong. Aluminum alloys
don’t corrode as readily as steel. But because they lose their strength at high
temperatures, they cannot be used for skin surfaces that become very hot on
airplanes that fly faster than twice the speed of sound.
● Steel can be up to four
times stronger and three times stiffer than aluminum,
but it is also three times heavier. It is used for certain components like
landing gear, where strength and hardness are especially important. It has also
been used for the skin of some high-speed airplanes, because it holds its
strength at higher temperatures better than aluminum.
● Graphite-epoxy is one of
several types of composite materials that are becoming widely used for many
aircraft structures and components. These materials typically consist of
strong fibers embedded in a resin (in this
case, graphite fibers embedded in epoxy).
Thin sheets of the material can be stacked in various ways to meet specific
strength or stiffness needs. Graphite-epoxy is about as strong as aluminum and weighs about half as much.
● Titanium is about as strong
as steel and weighs less, though it is not as light as aluminum.
It holds its strength at high temperatures and resists corrosion better than
steel or aluminum. Though titanium is expensive,
these characteristics have led to its greater use in modern aircraft.
Sufficient
stress will buckle—and in some cases can destroy—a structure. Aircraft are
designed to resist such buckling (though some parts and small areas are allowed
to buckle to some extent). Buckling depends not only on the physical properties
of the structural material but also on thickness and shape.