The Complete Guide to 3D Printing Composites

In recent years, composite 3D printing has grown rapidly in popularity. In a composite material, at least two different materials are joined together with separate purposes. One material serves as the matrix and is intended to maintain the structure, while the other provides additional properties as a reinforcing material. In fact, the goal of composites in general is to add new properties or characteristics while also overcoming certain drawbacks of the original material (which is the matrix). For example, it is possible to give the material better mechanical properties, flame retardancy, more stability, resilience, etc. Composites can be distinguished as a whole on the basis of their material characteristics (metallic, mineral, ceramic, organic) or on the basis of their geometry.

There are a few different forms of composites including: particle composites; fiber composites (short fiber, long fiber, continuous fiber ); layered composites; and impregnated composites. Out of these, fiber composites are those most often seen in 3D printing. Fiber composites are particularly popular in materials engineering because they allow materials to be reinforced in certain directions. Probably the most popular on the market is carbon fiber, followed by glass fiber, which are also the most commonly used in additive manufacturing. Carbon fiber’s popularity as well stems from the fact that it has one of the highest strength-to-weight ratios. This allows for strong but light parts, ideal for industries like aerospace.

A 3D printed part using carbon fiber reinforcement, resulting in higher strength-to-weight ratio and less material consumption (photo credits: 9TLabs)

Properties of Composite Materials in 3D Printing

Composites are extremely beneficial when making lightweight yet strong parts. The fibers add strength to a part without adding weight. As mentioned, there are two types of reinforcements, short fiber or continuous fiber. In the first case, chopped fibers, which consist of segments less than a millimeter in length, are mixed into traditional thermoplastics to increase the stiffness and to a lesser extent the strength of components. Chopped fibers can be mixed with thermoplastics such as nylon, ABS or PLA. Every manufacturer will add and blend a different amount of short fibers to its plastic polymer, resulting in filament spools of different strengths. You should also be aware that print quality will be impacted by the quantity of chopped fibers. Above a certain threshold, the 3D printed part will lose in surface finish.