Composite Materials

What Are Composite Materials?

Composite materials are engineered substances made by combining two or more constituent materials with significantly different physical or chemical properties. The result is a material with characteristics superior to each individual component. In aviation, the most widely used composites are carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP), where strong fibers are embedded in a resin matrix to create panels, beams, and structural skins that are simultaneously lighter and stiffer than aluminum alloys.

How They Work

The structural performance of a composite comes from the orientation and layering of fiber plies. Engineers stack sheets of pre-impregnated fiber ("prepreg") at calculated angles—typically 0°, 45°, and 90°—and cure them under heat and pressure in an autoclave. This process locks the fibers in optimal load-bearing directions. The result delivers:

• High strength-to-weight ratio: CFRP is roughly five times stronger than steel at one-fifth the weight.
• Corrosion resistance: Carbon fiber does not rust, reducing maintenance costs over the aircraft's life.
• Design freedom: Complex aerodynamic contours are easier to form in composite than in sheet metal.
• Fatigue resistance: Composites generally withstand cyclic loading better than aluminum, reducing metal fatigue concerns.

Applications in Aviation

The Boeing 787 Dreamliner was the first commercial airliner to use composites for more than 50% of its structural weight, including the entire pressurized fuselage barrel and the wingbox. The Airbus A350 XWB similarly uses CFRP for fuselage frames, stringers, and wing covers. Engine fan blades on modern high-bypass turbofans—such as the GE9X and LEAP—are manufactured from woven CFRP, withstanding extreme centrifugal and aerodynamic loads while saving hundreds of kilograms per engine. Military aircraft like the F-22 Raptor use composites for low-radar-signature stealth skins.

Future Developments

Next-generation composite manufacturing is moving away from slow autoclave curing toward out-of-autoclave (OOA) processes and additive manufacturing of continuous-fiber parts. Thermoplastic composites—which can be re-melted and welded rather than bonded with adhesive—promise faster production rates and improved recyclability, critical for sustainability goals as aviation works to meet 2050 net-zero targets. Research into hybrid metal-composite joints and automated fiber placement robots is expected to cut production costs significantly through the 2030s.