[lovelj]

Very cool part. Cothran should be familiar with this. He works in our lab.

A little bit more information. We've printed with carbon fiber reinforced ABS for about 5 years. It's a game changer.

First, the carbon fiber (if done right) increases strength, stiffness, thermal conductivity and (most importantly) reduces the coefficient of thermal expansion. We've printed complex parts on a Solidoodle with 20% CF ABS, printed the exact same thing out of ABS on our Fortus 900 and compared geometrically with our laser scanner. CF ABS on a Solidoodle is more accurate than ABS on a Fortus. In a nutshell, good material in a crappy machine beats crappy material in a good machine. You don't need an oven to control residual stress, warp and curl. We've done this on big machines (google Big Area Additive Manufacturing). Carbon fiber reinforced thermoplastics is secret sauce in the BAAM machines. We've printed parts 20 feet long with no distortion.

Second, the fact that someone's strength went down tells me the fiber isn't wetting out well with the base material. All carbon fibers have sizing (or chemistry) on their outer surface that impacts their ability to fuse with a secondary material. If you are using carbon fiber that is sized to interface with resins (typical for aerospace), it won't wet out well and you'll get poor adhesion between the fiber and thermoplastic. I'd suggest making your own filament and get pellets from someone like Techmer. You can get the loading anywhere from 5% up to 50%. 20% to 30% seems to be the sweet spot. We get 2 to 3X increase in strength and 8X increase in stiffness. Cost wise, 20% CF ABS is about $5/lb. PolyOne sells good material as well. Another material that is very interesting is PLA with Bamboo. We printed some large parts with 10% bamboo that turned out beautiful. Getting ready to try 20% bamboo.

In terms of properties, realize that they will be anisotropic. All the fibers line up with the bead (the nozzle acts like a funnel). So you're strength goes up in the bead direction but the best you'll get is about 80% to 90% of the base thermoplastic properties in the bead to bead and z-strength.

All in all, if you get the fiber with about 20% CF, you'll overcome a lot of the warp and curl problems.

Thanks for sharing.