Different Carbon Fiber Composite Fabrication Processes

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Whereas it is possible to create carbon fiber products with customized properties, it is interesting to learn about the various processes of fabrication of products out of these new age materials. Some of the popular processes used in industry are being narrated here below.

Hand Lay up:

The simplest technique of processing composite materials is hand lay-up. Although it appears simple but is in fact also the most skilled one. In this process, a ready mold is used to create layers of resin and reinforcement materials which could be fibers or woven fabrics or chopped strand matts which are precut in the shapes as per desired buildup of the component. Thermosetting Polymers together with curing agents are also applied on the surfaces of mats.

Tools such as brush and rollers are used for better control of material spread.

After completion of the curing process at predefined temperatures based on material nature and the component being built, the solid molded component can be removed and taken for further processes like trimming of edges or final touch-up

Pros:

• Large sizes of carbon fiber products can be built
• Better control of layer build-up based on operator skill
• Flexibility

Cons:

• Mold building maybe time consuming and expensive
• Operator skill level and attention plays an important role and may have a direct relation with the quality of component produced
• Operator safety is important

Resin Transfer Molding (RTM):

This technique is popular in the aerospace and wind energy industry for manufacturing in batches, large sized carbon fiber products.

In this process, layers of reinforcement are laid in the lower mold (which is generally made from Aluminum, and in two pieces, the upper and the lower). Thereafter, the mold is closed and heated. Resin is poured and generally assisted by vacuum to enable perfect penetration across the full volume of the mold. This is why, sometimes it is referred to as VARTM (Vacuum Assisted Resin Transfer Molding). The process is characterized by low pressure and low temperature. After completion of the curing process, the mold is opened and the component can be removed and sent for finishing activity.

The process is economical and environment friendly and commonly deployed for making large objects. However, there might be instances of dry points where the penetration of resin was incomplete.

Additive Manufacturing

3D printing of materials, more commonly known as additive manufacturing is gaining momentum in every field and particularly in the carbon fiber products manufacturing industry. With this technique, materials are built as a stack of cross-sectional material-layout, layer by layer. The most important techniques of additive manufacturing are FDM (Fused Deposition Modelling) and SLS (Selective Laser Sintering).

Additive manufacturing of CFRP Carbon fiber reinforced polymers thermoplastic matrix is very much feasible and in practice these days. Composites using carbon-filled and precursors are very much possible to build.

Fused Deposition Modelling:

It is a process of printing a specific material using extruder by building layer by layer to give final shape to a targeted component or test piece.

Pros:

• Most complicated 3D shapes can be designed and manufactured easily
• Designing in CAD provides a lot of useful information well in advance, concerning for instance, total amount of material required, weight of the components being built, based on the specific density of the materials used. Tensile and flexural properties, modulus and stress levels
• Zero wastage as compared with material removal technologies
• Rapid prototyping for trials purpose is the best possibility using additive manufacturing, before mass production and the 3D printing technique solves this easily
• Double nozzles enable deployment of resins and thermoplastic fiber or filament simultaneously or alternatively, to build a solid component
• Directional setting of fiber material is possible with the use of integrated continuous Carbon fiber printing
• Because of the wide flexibility in this process, it is popular with core research organizations as well

Cons:

• Build volumes are limited based on the capacity of the machine
• Accuracy levels are affected with large build volumes
• The process is slightly slow
• Woven fabrics cannot be used as only powder material is possible to deploy
• Porosity of the component built may be higher as compared with other techniques
• Limited range of customization possible

Selective Laser Sintering:

It's a fast-laying twin printing technique nowadays used in the carbon fiber composites industry. A SLS printer uses powder instead of filament to build accurate layers. After a predefined layering step, instant Laser heating is applied on selective surface profiles based on CAD data to set the material at a temperature slightly lower than its melting point.

Pultrusion:

This method is mostly used to fabricate elements or articles that have a uniform cross section across their length. Examples include carbon fiber tubes, pipes, beams, and channels used extensively in complex processing industry, and chemical industry.  More specifically, carbon fiber tubes, carbon fiber prepreg tubes,  It is generally a continuous processing line beginning with a resin bath through which, the carbon fibers are allowed to pass, followed by a curing chamber followed by the set of rollers that are pulling the impregnated (prepeg) fibers, and finally a cutting area where definite lengths are cut. This process is best suited for continuous production of composite articles in running lengths.

Filament Winding:

Filament winding process is best suited for manufacturing cylindrical objects and large diameter tubes like carbon fiber prepeg tubes. In this technique, a mandrel of a definite diameter and length is rotated to continuously pull resin impregnated carbon fiber and results in controlled winding of the material over the mandrel. This is followed by curing and finishing. The cylinders or tanks thus produced have capabilities to withstand very high pressures and hence find application in fluid and gas industry.

Roll-wrapping:

This is a form of filament winding wherein carbon fiber sheets and strands are made to wrap around a rotating mandrel in a helical fashion in multilayer. This process is highly suitable for producing carbon fiber roll-wrapped tubes. Not only tubes, even carbon fiber roll-wrapped cones and complex 3d profiles of carbon fiber roll-wrapped tubes are made this way. Important example is the frame of a bike.