What Are Composites?

When you start to use 3D printers, you will undoubtedly come across ‘composites.’ Many designs require composites for completion but it’s pretty difficult to achieve this when you are unsure what composites are. Luckily, we are here to clear this mystery up for you.

Simply put, the definition of composites is a combination of different components. A composite is two or more materials that have different chemical or physical properties. Varying composites are used in different industries such as construction where composites are combined to act as concrete. However, they remain separate and unique from one another as they do not fully merge into each other.

Although composites is a term widely used in engineering, 3D printing composites are materials that have been reinforced with fibers. These fibers tend to be extremely beneficial when merged with another material and are rarely used on their own to create a piece of material.

Rather than being used on their own, these fibers are added to a matrix (two materials with different physical and chemical properties). This is done in the form of short fibers and/or in the form of continuous reinforcements of the fiber. One of the most commonly used fibers in 3D printing is currently carbon fiber due to it having one of the highest and most powerful strength-to-weight ratios.

So, in other words, composites deliver their most useful traits and properties to help improve the final product and outcome. In the majority of industries, most composites are typically designed with a specific use in mind. These include added durability, strength, and efficiency which are all useful traits for a successful 3D project.

Continue reading as we discuss 3D printing composites in further detail so you can understand these materials going forward.

Why are Materials Reinforced with Fibers?

Composites are supremely useful and beneficial when creating a lightweight item that requires strong parts. In 3D printing, there are two types of reinforcements – short fiber and continuous fiber.

Short fibers, also known as chopped fibers, consist of tiny segments (less than a millimeter in length). These are combined with traditional thermoplastics to help increase rigidity and stiffness.

These also help strengthen the components to a certain degree. These chopped fibers can be mixed with thermoplastics like PLA, ABS, or nylon. Each manufacturer adds and blends a unique amount of short fibers to their plastic polymer. This results in filament spools of varying strengths and stiffness.

The number of short fibers used also has a significant impact on the quality of your print. If you go above a certain threshold, the 3D print could lose its surface finish.

For the highest and best performance, you will be looking at continuous fiber reinforcement. It is not a straightforward process to make continuous fiber composite parts, especially when you compare it to the creation of short fiber composite parts.

This is because the fibers have to be integrated into a thermoplastic material continuously as it gets extruded. These fibers can also be dispatched depending on the design techniques being used. This helps to optimize a component’s strength-to-weight ratio and consumption of material techniques also referred to as DfAM (Design for Additive Manufacturing).

Because of continuous fiber reinforcement, manufacturers have found that it is possible to produce parts as strong as metal!

When we consider the fibers that are available on the market today, carbon fiber is certainly the most popular and widely used.

As well as this, fiberglass is also used frequently. This is a type of fiber-reinforced plastic that adopts glass fiber and Kevlar (a strong, heat-resistant synthetic fiber). Fiberglass is popular thanks to its cost-effectiveness. It adds strength to plastic materials while Kevlar boasts a very high shock resistance meaning it tends to bend rather than break even under intense pressure.

Short (Chopped) Fiber Materials

As we mentioned, short or chopped fiber-filled plastics are the most commonly used type of composite 3D printing plastics. The chopped compost 3D printed material most widely used is chopped carbon fiber.

As we stated, this is when carbon fiber pieces are blended with traditional 3D printing plastics such as PLA, ABS, and nylon.

These fibers help take out some of the stresses of the material. This works similarly to how concrete is added to cement to boost overall strength. The properties of typically lower-grade materials are then boosted as well as the thermal stability of the mechanical properties.

The range of operating temperatures is widened so the material’s behavior is easier to predict in high and low temperatures.

Short composite 3D printing materials take traditional, standard plastic that may lack certain properties and help boost its strength, durability, and firmness. This results in a higher-performing material than in its original form.

Continuous Fiber Materials

Continuous fiber 3D printing supplies continuous strands of fiber reinforcement to a component. This helps it achieve metal-like strength but at a fraction of metal’s weight.

You only need to use two print nozzles to power the printer and see it build the matrix materials out of thermoplastic. This helps to flatten any continuous strands of these fibers into the 3D-printed part. This entire process is known as Continuous Fiber Fabrication (CFF).

Kevlar strands are used in continuous fiber. These are ironed into a part to increase impact resistance through the use of a composite fiber printing nozzle. Unlike short (chopped) fibers, continuous strands can absorb and dispense different loads across their whole length.

When these fibers are placed into a thermoplastic matrix, the component can then handle higher loads better and absorb much larger and more powerful impacts. All in all, continuous fibers help a part achieve the strength of metal but at a fraction of its weight.

Continuous fibers act as the backbone of a 3D-printed part. These can then be laid down in unique patterns to optimize that component’s strength to support heavier weights. Fibers can be placed in specific areas based on where the part will experience the heaviest loads.

Therefore, you can add strength exactly where you need it most. Compared to traditional deposition-based 3D printers, as well as short fibers, this is very different. This is because continuous fiber materials allow you to evenly distribute different properties throughout the entire component.

In Summary

We hope this article has helped you understand composites for 3D printing so you can adopt either short (chopped) fiber materials or continuous fiber reinforcements for your next 3D printing project.

Michael Moore