Roll-wrapping
Carbon Fibre Tube Manufacturing Methods; What are they, how do they differ and which method best suits your application?
When Carbon Fibre Tubes Ltd (CFT) was established in 2003, the composites industry was in its infancy. At this nascent stage, carbon fibre, as a material, was only just starting to be considered as an alternative to traditional materials/metals. If you wind forward the 20+ years that CFT have been operating, the composites industry is now unrecognisable; it has increased in size, scale and complexity. Manufacturing of carbon fibre is now global, the properties of composites are better understood, and consequently, the application of this advanced material is increasingly widespread.
Unlike many industries, the composite tube sector is segregated by manufacturing method, with companies often differentiating themselves by the process they specialise in. Carbon fibre tubes are prized for their exceptional strength-to-weight ratio, rigidity and environmental resistance, making their application ideal in a wide range of industries from aerospace and automotive, to medical technology, sports equipment and robotics. However, the performance and cost of these tubes depend heavily on the manufacturing method used.
What are the different methods of manufacturing carbon fibre tubes?
The main carbon fibre tube manufacturing processes include:
Each process offers unique benefits. It is paramount, therefore, to understand each of these methods, their merits and the impact they can have on the final product. It may be that a tube manufactured using one method is more or less suited to its final application than a very similar specification of tube but manufactured in a different way. We explore these below to explain each process and give some example applications suited to each method.
What is Roll-Wrapping?
Roll-wrapping is one of the most common manufacturing techniques for high-performance tubes. Layers of pre-impregnated carbon fibre (known as pre-preg) are rolled around a mandrel in precise orientations (e.g., 0°, ±45°, 90°). If required, specialist pre-preg layers can be added to the laminate design at this stage too. The assembly is then heat-cured in a specialist oven and then the mandrel removed.
The main advantage of this method is that it offers the ability to design and customise fibre orientation. This means the tube can be manufactured to meet exact strength and stiffness specification, and can therefore be crafted to meet the needs of the final application. This process can also achieve an excellent surface finish which is an important factor when aesthetics are valued, often cited in luxury automotive and marine markets.
Some example applications of roll-wrapped carbon fibre tubes include marine parts, bicycle components, UAV/UAS structures, antenna masts, camera/AV tripods, frames placed under greater strains, and aerospace parts.
Roll-wrapping is the primary method our team at Carbon Fibre Tubes (CFT) use, and we are considered experts in the field of laminate design and custom tube manufacture. Learn more about our capabilities here.
What is Pultrusion?
The pultrusion manufacturing method involves pulling continuous fibres through a resin bath and a heated die, curing them into a constant cross-section. In many ways, this is a simpler process; the nature of the process means that this is the ideal manufacturing method for long, straight tubes where consistent quality is valued.
The main advantage of pultrusion is the resulting lower overall production cost; cost efficiencies are achieved because the process is more suited to repeatability and thus benefits from automation. However, pultrusion has limitations: fibres run almost entirely lengthwise, so the tubes have limited torsional strength and are not suitable for all applications.
Some example applications of pultruded carbon fibre tubes include industrial rollers, support beams, and lightweight frames that are subject to less stress/strain.
What is Filament Winding?
The process of filament winding is the method by which resin-impregnated carbon fibre tows (known as towpreg) are wound, under tension, around a rotating mandrel at controlled angles. This is achieved using a specialist filament-winding machine, such as our 6-axis KUKA Robot Winder. Once fully wound and compacted, the tubes are heat cured in dedicated ovens, after which the mandrel is removed.
The main advantage of this method is that it provides an excellent level of control of fibre angles. By doing this, tubes can be made with superior hoop and torsional strength, which makes them far more resilient under pressure. This method can also make non-consistent shaped tubes, such as tapers, spheres, or tubes with irregular geometry.
Some example applications of filament-wound tubes include pressure vessels and pipes, drive shafts, rocket casings, scuba tanks, and sub-sea applications (all of which are subject to extreme pressure scenarios).
At CFT, we have in-house filament winding capabilities and have delivered a series of composite projects using filament winding to our Defence customers. Learn more about our capabilities here.
What is Bladder Moulding?
Bladder Moulding is the process of wrapping dry fabric or pre-impregnated carbon fibre (pre-preg) around an internal bladder or mandrel, then placing it in a metal mould to cure under pressure and heat. This can be a more labour-intensive manufacturing method, but it does provide the ability to make complex shapes or tubes with curves/kinks. The nature of the moulding under pressure means there is a high level of fibre compaction, which, in turn, increases the tube’s strength. From an aesthetic perspective, this process can also create very smooth finishes.
Some example applications of tubes created using Bladder Moulding include automotive suspension components, sporting goods, and aerospace fittings.
CFT have worked on some very complex projects using this process to achieve an exact specification for customers. One such example is the curved frame structure we created for GOM.
Conclusion
Each carbon fibre tube manufacturing method balances cost, strength, weight, and geometry in different ways. Roll-wrapped tubes offer tailored performance, pultruded tubes are economical for simple profiles, filament-wound tubes excel in torsional applications, and bladder-moulded tubes allow complex, high-quality parts. Choosing the right method ultimately depends on the engineering requirements of the final application.
