Composite pipe structure
Composite pipes — Beading study

A composite tube is made up of several layers of material.

An inner layer, the gel coat, ensures resistance to corrosion and abrasion, and provides a very smooth surface finish. The gel coat consists either of pure resin, possibly with mineral fillers, or of a resin-rich (up to 70% by weight) veil of E or C glass fibers. However, the inner layer may itself be a thermoplastic polymer or elastomer tube. In this case, it's a liner.

Above the inner layer, several layers of glass-fiber-reinforced resins provide the tube's mechanical strength. Hereinafter referred to as composite laminates. The volume fraction of glass in these layers is around 70%.

Finally, an outer layer ensures resistance to the environment (UV, corrosion, bacteria), fire, impact, and provides a better appearance... Sometimes called top coat. It consists...