The Oak Ridge team has a lot of capabilities in materials and processes to help in formulating the right type of materials with carbon fibers. Last year, the lab established a carbon fiber composites consortium. Since carbon fiber composites made out of autoclave with FDM represents a major shift, development will proceed in stages.
During the first 18 months or so, the partners will determine how to put milled, or chopped, carbon fiber in thermoplastics in an FDM process, and how to tailor the material's mechanical properties. The next stage will extend to the three-year mark and perhaps beyond. This will focus on laying down continuous carbon fiber on a center line of plastic wire, depositing that and growing it with the FDM process, and cutting it. "Since you can lay fiber in multiple directions, we'll take advantage of all the known statistical composite analysis tools, and integrate them into the FDM process," said DeGrange.
FDM is better suited to this project than other additive manufacturing techniques because it's one of the easiest to bring new materials to, especially multifunctional or filled materials, and for delivering them as a filament feedstock, said DeGrange. "It's easier to put carbon-loaded materials in a plastic line and maintain homogeneous repeatability than it would be to try this in a powder bed, for example."
Both methods have advantages, but when filling up a powder bed system with most plastics, the materials typically can't be recycled. The spectrum of thermoplastic materials that can be run in FDM is broader than with powder, and there's very little waste.