Carbon fiber tubes can replace steel, but more often they replace aluminum. In many cases, the weight of a carbon fiber tube may be 1/3 of that of an aluminum tube, but it still has the same or better strength characteristics. Therefore, carbon fiber reinforced tubes are often used in applications where weight reduction is critical, such as aerospace, racing, and leisure sports.
The most common carbon fiber tubular outline shapes are square, rectangular and circular. Rectangular and square profiles are often referred to as "box beams". The carbon fiber box beam provides excellent stiffness to the structure and simulates two parallel I-beams.
Manufacturing carbon fiber tube
Hollow composite structures can be difficult to manufacture. This is because pressure needs to be applied to both the inside and outside of the laminate. Carbon fiber tubes with continuous profiles are usually manufactured by pultrusion or filament winding.
Pultruded pipe is by far the most cost-effective method of manufacturing continuous composite profiles. When pultruding a hollow tube, a "floating mandrel" is required. The chrome steel rod is firmly fixed on the side where the mold enters the raw material. The distance to install the hardware is far enough so that it will not interfere with the impregnated fiber when it enters the mold.
The space between the mandrel and the mold will determine the wall thickness of the carbon fiber tube.
Pultruded carbon fiber tubes can produce tubes of almost any length. The transportation of tubes is usually limited by length. In pultrusion, most of the fibers will extend in the direction of the tube. This produces a tube with great stiffness, but not much hoop or lateral strength.
Filament wound carbon fiber tube
In order to improve the strength and performance in all directions, filament winding is an effective method to manufacture carbon fiber tubes. Filament wound tubes are cost-effective and have excellent performance, but the biggest limitation depends on the length of the winding machine.
Other manufacturing processes
Although pultrusion and filament winding are the most common, they are not the only way to make carbon fiber tubes. Compression molding, vacuum infusion and autoclave processing are all methods of manufacturing carbon fiber tubes. Each has its own advantages and disadvantages.