Composites

A composite is made of two or more materials. Carbon fiber is a composite material. It is made of plastic strength­ened by strands (or fibers) of carbon. The first composite used to build aircraft was a material called Duramold in the 1930s. It was made from thin sheets or strips of wood laid on top of one another with their grains in different directions and then soaked with plastic glue. Having the grains of the layers lying in different
directions made the finished material stronger. A composite material called fiberglass was introduced in the 1950s. Fiberglass is made of plastic strength­ened with glass fibers. It was used in the Boeing 707 airliner.

Today about one-tenth of the Boeing 777 airliner is made of various compos­ite materials. About 24 percent of the new F-22 fighter plane is made from composites, with titanium (39 percent), aluminum (16 percent), steel (6 percent), and other materials (15 percent) forming the rest.

Stealth planes such as the Lockheed F-117 Nighthawk attack plane and the Northrop B-2 Spirit stealth bomber have more composite materials used in their construction than most aircraft, because composites do not reflect radar waves as metals do. Composites help stealth planes to disappear from an enemy’s radar screens.

GLIDER MATERIALS

Gliders, like other aircraft, used to be made from wood, but today they are made from fiberglass, which is extremely lightweight. The parts of the aircraft are made in molds. The inside of a mold forms the outside of the part. The mold is first painted with a substance called gelcoat.

(The gelcoat gives the glider a very smooth, glassy surface that is ideal for reducing air resistance.) Then mats of glass fibers are laid in the mold and soaked with liquid plastic. When the plastic with the glass fibers embedded in it has set hard, the part is popped out of the mold.

The same mold can be used over and over again to produce many identical parts.

an aircraft or spacecraft goes into produc­tion. Flight simulation, shown here for the X-33 in 1997, can provide crucial data to the designer. The X-33, conceived as a reusable space launch vehicle, was canceled in 2001 because of many technical difficulties, including flight instability.