# Explanation Of Filament Winding Process

As we stated in other articles in Mechanicalland, there are various kinds of processes available to produce different kinds of composite parts. The filament winding process is another composite part production process that is commonly used for specific applications.

Here, we explain the types, process parameters, and applications of filament winding processes.

Composite Materials: Science and Engineering (Materials Research and Engineering)

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## What Is Filament Winding Process?

Filament winding is the application that continuous reinforcement filaments are wound around a rotating mandrel. These continuous filaments are impregnated with a thermosetting resin. After the curing of this thermosetting resin, rigid and lightweight parts are produced.

### Part Shapes And Filament Winding Techniques

Because of the mechanical restrictions, part shapes that are produced with filament winding techniques are limited. Generally, axisymmetric and round parts are produced. The exact shape of the wound part depends on the shape of the mandrel.

In general, two types of winding methods are used; Helical winding and polar winding.

#### Helical Winding

In helical winding, the mandrel is rotated with actuating motor. And the carriage part that provides the filament of the mandrel, moved right and left, over the mandrel. With this mechanism, the helical pattern is obtained.

According to the physical and geometrical requirements, the relative motion between mandrel and carriage must be adjusted. There is a relationship between these velocities;

In this relationship;

• θ is the winding angle that is the angle between the perpendicular line to the axis of rotation of the mandrel and the angle of wound filament on the mandrel.
• Vc is the velocity of the carriage.
• D is the diameter of the mandrel.
• N is the RPM of the mandrel.

The winding angle can be adjusted with the adjustment of these parameters by using this equation.

#### Polar Winding

In this kind of winding technique, the winding operation is started with the winding of the filament along with the longitudinal orientation of the mandrel. Hollow and closed shapes can be obtained.

### Impregnation Of Resin On The Continous Filament

There are different types of impregnation of resin on the continuous filament. These different types of impregnations are also depended on the impregnation sequence. These types are; Prepreg winding, post-impregnation, and wet winding.

• Prepreg filament winding: In this kind of filament winding technique, the mandrel is heated and the filament is passed through a semi-cured resin before the winding operation.
• Postimpregnation: Filament is wound on the mandrel and the resin is applied to the wound filament.
• Wet winding: In this method, the continuous filament is passed through uncured resin and then wound on the mandrel.

### Mandrels That Are Used In Filament Winding

Mandrels must be produced especially that they can be collapsed easily at the end of the process. For this purpose, mandrels are produced as inflatable and deflatable types.

Soluble salts are also used in mandrel production. Collapsible metals are also another mandrel application.

### Applications Of The Filament Winding Processes

The products of filament winding processes are generally used on a commercial basis. But in the aerospace and defense industry, parts that are produced with filament winding process are very common.

Because of the low density and relatively high rigidity of these parts, missiles, helicopter blades, radomes, and airplane tails are produced with filament winding processes.

Commercial applications of filament wound parts; wind-turbine blades, shafts, reinforced tubes, and special storage tanks.

#### Materials

In the filament winding processes, epoxy resins are generally used as matrix components. And the continuous filament materials are generally boron, Kevlar, carbon, and glass. Polyesters and phenolic resins are also used.

## Conclusion

This is the general information about the filament winding processes available in the industry. Because the composite technique is the most developing material technology, techniques like filament winding also require further developments from engineers or technicians like you.