Composites in Aerospace Structures
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Carbon fiber composites make up about half the structural weight of current wide-body airliners such as the Boeing 787 and Airbus A350, and they are widely used in satellites and launch vehicles. They are chosen for weight, stiffness, fatigue resistance and corrosion resistance.
Why composites are used
- Weight. Lower structural weight cuts fuel burn on aircraft and increases payload on launch vehicles.
- Stiffness and stability. High-modulus fibers give stiff, light panels for antenna reflectors, optical benches and instrument mounts, and laminates can be designed for near-zero thermal expansion.
- Fatigue. Laminates loaded along the fibers resist cyclic loading well compared with aluminum alloys.
- Corrosion. Composites don't corrode, although metal fasteners and parts in contact with carbon need protection from galvanic corrosion.
Materials and processes
Primary aircraft structure is mostly made from toughened epoxy carbon fiber prepreg, laid up by hand or by automated tape and fiber placement and cured in an autoclave. Out-of-autoclave prepregs, resin transfer molding and filament winding are used for secondary structure, pressure vessels and launch vehicle parts. Sandwich panels with honeycomb cores are common in fairings, floors and satellite panels.
What comes with them
- Qualification. Materials and processes are qualified, and changes to the resin, fiber or cure cycle can require new testing.
- Inspection. Delaminations and porosity aren't visible on the surface, so parts are checked by ultrasonic or other non-destructive methods.
- Impact damage. A low-energy impact can leave little visible mark while damaging the laminate inside, which drives damage tolerance requirements.
- Cost. Aerospace prepreg, autoclave curing, tooling and inspection make composite parts expensive, especially in small quantities.
See space and defence and composites manufacturing.