Carbon Fiber Tubes

Learn About The Stiff and Lightweight Features of Carbon Fiber Tubes

Carbon fiber road bicycle outdoors
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Carbon fiber tubes are ideal for both the hobbyist and industry professional. Using the rigidity of the carbon fibers, an extremely stiff yet lightweight tubular structure can be used in a wide range of applications.

Carbon fiber tubes can replace steel, but more often than not, it is replacing aluminum. In many instances, a carbon fiber tube can weigh 1/3rd of an aluminum tube and still have the same or better strength characteristics.

Because of this, carbon fiber reinforced tubes are often found in applications light weight is crucial, like aerospace, race cars, and recreational sports.

The most common carbon fiber tubular profile shapes are squares, rectangles, and circular. The rectangular and square profiles are commonly referred to as a "box beam". Carbon fiber box beams provide excellent rigidity to a structure and simulate two parallel I-beams.

Carbon Fiber Tube Applications

Any application where weight is crucial, switching to carbon fiber will be beneficial. The following are some of the most common uses of carbon fiber tubes:

  • Aerospace beams and spars
  • Formula 1 structural components
  • Arrow shafts
  • Bicycle tubes
  • Kayak paddles

Manufacturing Carbon Fiber Tubes

Hollow composite structures can be difficult to manufacture. This is because pressure needs to be applied to both in internal and the external side of the laminate.

More often than not, carbon fiber tubes with a continuous profile are manufactured by either pultrusion or filament winding.

Pultruded tubes are by far the most cost effective method of manufacturing continuous composite profiles. You can learn about the pultrusion process here. When pultruding a hollow tube, a "floating mandrel" is required.

A chromed steel rod is firmly affixed in place on the side of the die where the raw material enters. The mounting hardware is far enough away that does not interfere with the impregnated fiber as it enters the die.

The space between the mandrel and the die will determine the wall thickness of the carbon fiber tube.

Pultruding carbon fiber tubes allow for the production of tubing of virtually any length. Transportation of the tube is the generally the restriction on length. In pultrusion, most all of the fiber will run the direction of the tube. This creates a tube with a tremendous about of stiffness, but not much hoop strength, or cross-directional strength.

Filament Wound Carbon Fiber Tubes

For increased strength and properties in all directions, filament winding is an effective method in manufacturing carbon fiber tubes. You can learn more about filament winding process here. Filament wound tubes are cost effective and have excellent properties, however, the largest limitation is based on the length of the winding machine.

Other Manufacturing Processes

Pultrusion and filament winding, although the most common, are not the only way to manufacture carbon fiber tubes. Bladder molding, compression molding, vacuum infusion, and autoclave processing are all methods to manufacture carbon fiber tubes.

Each has their own advantage and disadvantage as well.