The thick-wall composite tube myth

26.4.2018 15:40 EET

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Exel Composites blog by Patrick Loock

Today, composite manufacturing technology allows us to design and manufacture tubes that meet required material specifications, and which are very competitive with other materials in terms of weight and cost. Yet many clients have a preconceived idea that composite tubes must also have thick walls and because of this will automatically exclude them from consideration. I’m on a mission to dispel this myth.

I’ve been selling composite tubes for many years and have heard this mistaken belief many times. So where does it come from? From my experience, I’ve seen the spectrum of tube wall thicknesses. In some cases thick walls are required for structural or mechanical reasons, but in other cases they result from poor control of the manufacturing process. When manufacturing experience and engineering expertise work together, the production of thin-wall composite tubes with wall thicknesses of less than 1 mm is achievable.

How are thin-wall composite tubes manufactured?

The primary objective with any tube (whether composite, steel, aluminum or PVC) is that the material used meets or exceeds the desired performance requirements within the desired cost parameters. For composite tubes, reinforcement fibers are combined with a resin to form the tube. The most common manufacturing processes are pultrusion and pullwinding. Each of these processes requires an understanding of many factors, from the choice of reinforcing fiber, to the angles the fibers are oriented in the tube structure, to the resins used. All of these factors need to be taken into consideration for optimal overall control of the process.

Wall thickness is affected by the arrangement of the fibers. This is where experience and engineering are required to determine the optimal amount of fiber required, and its arrangement to ensure the tube’s mechanical properties meet or exceed the specifications. This ensures the correct performance, weight and cost characteristics are met. With pullwinding manufacturing we are able to arrange fibers in the longitudinal and crosswise orientations at 90 degrees to produce a tube with a wall thickness of less than 1 mm.

Material choice

Today there are two main fibers used to produce composite tubes – glass and carbon. Glass fiber composite, commonly known as fiberglass, has been used for more than 70 years and is still considered a high-performance material. Carbon fiber composite is a newer material and is best known for its high strength (stiffness) and very low weight. Both of these materials may be combined in the tube manufacturing process in what is known as a hybrid composite. This allows us to offer different solutions for different client needs, taking advantage of the benefits that each of these different materials offers.

Busting the myth globally

I’ve noticed that when I show samples of our thin-wall tubes to clients the 'thick-wall' myth quickly disappears as our discussion turns towards their requirements and the advantages of using composites. Composite solutions very quickly (if not automatically) meet the lightweight requirement. Alternatively, if corrosion is a factor, composite tubes offer great resistance to harsh environments and will not rust or corrode. If electrical safety is a requirement, fiberglass is an inherent insulator and can be used around live electricity.

If you have been thinking about your tube needs and would like to see our thin-wall tubes in person, give me a call or send me an email. With our global engineering capability, competitive manufacturing capacity and over 50 years’ experience pioneering composite possibilities, I plan to continue dispelling the thick-wall myth, wherever I go.

Exel Composites Oyj, Vantaa head office, Mäkituvantie 5, FI-01510 Vantaa, Finland