There's a conversation out there, assessing that Carbon Fiber infused polymers are just for looks -- they add no strength, and while they might add to stiffness, they effectively weaken parts.
THIS IS TRUE.
BUT NOT REALLY.
There are three main reasons to add Carbon Fiber to your polymer, specifically your 3D Printed part:
1. Improving Stiffness, Strength-to-Weight ratio
2. Increasing Dimensional Accuracy (less warping)
3. Improved Electrical Resistivity
Let's take a quick look at the first two of these:
There are multiple grades of carbon fiber: some of which are milled carbon, chopped carbon, then Industrial-grade, aerospace-grade, and more.
When it comes to percentage of carbon in the filament, Is it 20% carbon? 30% carbon? In reality, this is the wrong question to ask. There are a few factors which make a difference:
a) Length of fibers
b) Diameter of fibers
c) Grade of fibers
Aerospace-grade carbon is thinner and stiffer than industrial grade Carbon. Our PEEK contains aerospace-grade CF, while our Nylon contains industrial grade; both contain chopped strands.
Because the carbon adds a significant amount of stiffness, the end-result is a MUCH easier part to print.
Many of you are likely familiar with the warping and curling that occurs when printing high-temp plastics like PEEK or PEI -- it's the biggest culprit of failed prints, broken buildplates, and dimensional inaccuracy.
When you print with a carbon-infused filament, however, many of these problems disappear. CFPEEK can feel 10x easier to print, the results have more accurate dimensions, and frankly, it looks way cooler.
The increased stiffness is a plus, but the real win is ease-of-printing, lower print failure rates, and better bridging capability.
(Because of this, you can upgrade any print job in our 3D Print service to CFPEEK, totally free)
Milled carbon fiber is exactly as it sounds; short, almost powdered carbon. Chopped carbon actually starts with strands of carbon. When you start with a 6mm strand, and then extrude into filament through a twin-screw and/or single-screw extruder, it becomes shorter, averaging around 200-300μm.
These strands then align themselves while extruding through the print nozzle, and massively increase stiffness. This is because the carbon is infused in the material -- perhaps not adhered or bonded so much, but integrated into the structure, adding stiffness along the layer lines.
Milled carbon is much less expensive, and still adds stiffness, for example:
0% Carbon fiber - 1950MPa
20% milled carbon fiber - 6000 MPa
10% chopped carbon fiber - 8500 MPa
As you can see, there's a big jump in stiffness with the chopped carbon.
The real question to ask is not "how much stronger is it" or "how much carbon fiber is inside", but instead, "what type of carbon fiber is this using?"
Then, based on your application, making an educated decision to get the right material for the job. Or, of course, drop us a line, and we'll help you figure it out!
At Vision Miner, we enjoy CFPEEK both aesthetically and practically. It prints more easily while maintaining most of the desirable mechanical and chemical properties of PEEK.
* Big thanks to Matt Howlett at 3DXTech for helping the community out with information on this subject!