Pultrusion is a method of manufacturing continuous fiber reinforced composites profiles. The manufacturing process is similar to extrusion, where molten plastic or metal is pushed through a die. However, with pultrusion, the material is "pulled" through a die. (Hence the name, pul-trusion).
Originally invented by Brandt Goldsworthy, well known as the pioneer of fiber reinforced composites, pultrusion is a method of manufacturing composites extremely economically. Once a pultrusion machine is started, it is highly automated and requires little hands-on labor.
The Pultrusion Process
- Raw fiber (glass, carbon, aramid, etc) is pulled off of doffs or rolls from a creel racking system.
- The fiber is pulled through a bath of thermosetting resin. Most often the resin is polyester resin, but also vinyl ester, epoxy, and more recently, urethane.
- Using guiding systems, the impregnated fiber is led through a heated die. The entrance of the die is often cooled to avoid curing the resin while excess resin is squeezed off.
- As the fiber and resin is pulled through the heated die, the resin cures and exits as a fully formed composite. The shape of the pultruded composite part will match the shape of the die.
- All of this is accomplished by a set of "pullers" or "grippers" which are pulling this material at a consistent rate.
- At the end of the composite machine is a cut-off saw, which cuts the pultruded profiles at a desired length.
Once a pultrusion machine is up and running, you do not want it to stop. The longer the machine is running, the less labor is required, and the cost of production is reduced. This is because regardless of how much is produced, there is the same amount of labor involved in the set-up at the beginning, and the clean-up at the end. Hence, for high volume composite products, there is no better manufacturing process cost wise, then pultrusion.
Common products manufactured with the pultrusion process include:
- Window Lineals
- Flat Sheets
- Ballistic Panels
- Fiberglass Tubing
- Tool Handels
- Archery Arrows