The role of continuous fibers. In the strongest composites from professional 3D printers, continuous fibers act as the strengthening fiber constituent, to be combined with a plastic matrix. Continuous fibers are long fiber tows that are coated in thermoplastic. They endow a composite part with the directional strength of metal. They have elastic moduli between 16 times and 46 times greater than those of plastics. As opposed to chopped fibers which are suspended in the plastic, continuous fibers run uninterrupted through a part, thus distributing the load across the part’s three-dimensional geometry. They perform best in tension, so it is critically important to print them with loading conditions in mind.
3D printing composites with continuous fibers. 3D printing parts with continuous fiber reinforcement (CFR) works by combining continuous fibers with a plastic matrix. When printing a part with continuous fiber reinforcement, the professional 3D printer uses two nozzles and extrusion systems. The plastic material is extruded through a heated nozzle, while a second nozzle releases continuous fibers into the material. Releasing the plastic material through the heated nozzle thermally fuses the thermoplastic coating that surrounds each continuous fiber tow, melting it so it adheres into the plastic matrix. Parts can be reinforced in many different ways to optimize for different loading conditions. Fibers can be laid in a wide variety of 2D orientations within each layer of the 3D printed part. A user can also dynamically control the amount of fiber in the part by altering the amount of fiber in a layer, as well as designating how many layers are reinforced. This control enables engineers to 3D print parts exactly as strong as needed.