How is a Fiberglass Reinforced Plastic (FRP) pipe manufactured?

The most common manufacturing method for Fiberglass Reinforced Plastic (FRP) piping is the non-continuous process (or filament winding).

In this method, shown in the image below, long glass fibres are wound along the pipe, which spins thanks to a mandrel. As the mandrel revolves around, the sticky fibres of glass wind around the pipe (1). To make the fibres stick, the glass fibres pass through a resin bath (i.e., the “glass hopper”), where they get wetted by resin (2). Some filler (usually sand) might be applied to the glass and resin to increase the thickness of the pipe (3).

Depending on the spinning speed of the mandrel (and the moving speed of the glass hopper), the fibres of glass wound with different angles. This angle has an impact on the physical properties of the pipe. Of course, the slower the resin hopper moves, the more the glass fibres get wound around the pipe circumferentially. And the faster the hopper moves, the more the fibres are wound at a more horizontal angle. Thus, the structure of the fibreglass pipes is adjusted to enhance either hoop or axial strength.

When the desired wall thickness is reached, the glass fibres, the resin, and the sand are hardened with induced heat.