Pultruded vs Roll-Wrapped Carbon Fiber Tubes
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Two carbon fiber tubes with the same diameter and wall can behave completely differently. The difference is fiber direction, and that's set by how the tube was made.
Pultruded
Fiber is pulled through a resin bath and a heated die in a continuous process, so nearly all of it runs along the length of the tube. That makes pultruded tube stiff and strong in bending and tension for the money, and the process makes long, straight, constant sections cheaply. The weakness is everything else: with little fiber running around the tube, it's weak in torsion and crushing, and it splits lengthwise easily, especially at clamps and fittings.
Good for struts, rods and frames loaded mostly in bending or tension.
Roll-wrapped
Sheets of prepreg are cut and rolled around a steel mandrel, wrapped with shrink tape and cured. Because each sheet can be cut at any angle, the layup can mix plies: 0° fibers for bending, ±45° for torsion, 90° hoops for crush. Roll-wrapping also makes tapered tubes, and it's how many golf shafts, fishing rods and ski poles are made.
Good for tubes with combined loads, tapers, and a cosmetic outer ply.
Filament wound
A continuous band of fiber is wound onto a rotating mandrel at a set angle. Winding excels at hoop and helical angles, which makes it ideal for pressure vessels, drive shafts and tubes loaded in torsion or internal pressure. Angles close to the tube axis are hard to wind, so axial stiffness is usually lower than a pultruded or rolled tube unless axial plies are added another way.
Braided
Braiding weaves a sleeve of fibers over a mandrel at plus and minus angles. Braids handle torsion and impact well and follow bends and changes in section, which is why they show up in bike frames, hockey sticks and curved structural tubes. They're often combined with unidirectional plies for axial stiffness.
Quick comparison
| Process | Fiber direction | Strong in | Weak in |
|---|---|---|---|
| Pultruded | mostly along the tube | bending, tension | torsion, crush, splitting |
| Roll-wrapped | any mix of angles | combined loads, tapers | more labor per tube |
| Filament wound | hoop and helical | torsion, pressure | axial stiffness |
| Braided | plus and minus angles | torsion, impact, curves | axial stiffness on its own |
Joining tubes
Tubes often fail at the ends: clamps that crush, fittings that peel. Bonded sleeves with enough overlap, hoop plies under clamps, and inserts sized to the tube's real inside diameter fix most of it. See bonding carbon fiber.
Need a custom tube or a second look at a design? See composites manufacturing.