Processing

Filament Winding

Filament winding is a process to produce hollow, cylindrical, oval, and conical or ball shapes in GRP. The most important applications for this process are tanks, containers, silo’s (on which the end caps are frequently hand-laminated), and pipes.

There are various ways to produce filament-wound articles. A distinction can be made to the winding principle (lathe winding, planetary winding) or the angle of the reinforcement to the winding axis (parallel winding or cross winding). Modern winding machines equipped with multiple axis winding, can produce very complicated shapes. As reinforcement glass rovings or tapes are most frequently used.

The reinforcement is drawn through an impregnating bath, which contains the resin, already equipped with the proper curing system. Depending on the application the resin may also contain fillers. The reinforcement is wound on a rotating mandrel until the required wall thickness is reached. The winding angle and the glass content can be adjusted to obtain the required mechanical properties.

Typically, cylinder diameters, ranging from 40 mm to 8 m are wound on stationary machines (i.e. in a factory). For bigger diameters (which will present a transport problem) winding machines have been developed with which a product can be produced directly on site.

For the industrial production of pipes in large lengths a continuous winding process has been developed. In this process the winding mandrel is an endless stainless steel band, which runs under an angle on a turning support construction. The band makes a helical movement and the resin, glass fibre and fillers are dosed on top of it. The complete mass goes through a ring oven in which the curing takes place. After the curing oven the steel band is released from the inside and moved back to the start of the process.