What is Filament Winding?

Filament winding is a technique used to fabricate composite materials, which are materials made from two or more physically and chemically different substances. The filaments are wound around a mold form called a male mold or a mandrel. Most common filaments used in this process are glass, carbon, and aramid fibers. This technique is especially important for products in the aviation and industrial sectors.

As a highly automated procedure, the filament winding process is normally precise and exact in its measurements. Fibrous material is soaked in a resin bath and covered with low to medium molecular weight reactants. The fiber is then gathered from cylindrical spools and wound around the mandrel. As the material is wound, either epoxy resin, epoxy, or a polyester resin is poured onto it in a uniform manner.

It is extremely important that the mandrel be tightly held in the filament winding machine. This helps the mandrel be wound more precisely, and the filaments be placed in the correct pattern, according to the final application. Specialized computer programs are generally used to control this precise process.

Once all the filaments have been spun around the mandrel, the resin-covered composite is cured through heating in a computerized oven. Heat hardens the fiber and makes it easier to remove the new component from the mandrel form. The component is carefully extracted using a machine that maintains the structure of both the mandrel and the component. After extraction, the new composite fiber structure is ready to be processed and used.

The arrangement of the filaments is crucial to how the final product is constituted. A high angle pattern of laying the fibers encourages greater crush strength in the material. Crush strength refers to the amount of compressive force required to break or rupture a material. Arranging the fibers in a low angle pattern improves the tensile strength of the material. Tensile strength is the amount of stress a material can take when being pulled or stretched before tearing or breaking.

A high strength to weight ratio in the component structure is the result of the rigors of the filament winding process. This final structure is able to withstand much pressure and stress, whether it is shaped as a helix, sphere or cylinder. For this reason, composite structures made from this process are highly prized in industry. Such components are used as pressure vessels, aircraft bodies, power poles, pipes, and much more.