Did anyone do some comparison-prints /-tests between different carbon fiber / glass fiber filled filaments? I am printing some specimen with different CF-filaments to test them for rigidity and stuff… Any input would be highly recommended…
I just got my hand on:
Not all printers will handle the filaments, at least thats what the markforge makers state. Their printer is designed and built to handle carbon fiber and metallic filaments.
Well, I am (or my printers are, at least) capable of printing them all 
I am more interested in a comparison of properties…
Graphene is the most important .
i have not done any scientific comparisons, but i have printed some of those.
it’s been my experience that the carbon filled plastics print very well, look extremely good, but in the end - hurt the mechanical properties of those filaments. for example - i had a really hard to print mechanical part on a design i was working on, and while the carbon filled petg was much easier to print. it definitely was not as “strong” as plain old petg. it was more rigid/brittle and leaning towards PLA strength.
i have not tried XT-CF20, but i have heard good things about it, though i am doubtful.
my best experience has been with polycarbonate filament (even polymaker’s version is pretty good with a plus is that it’s easier to print). and annealed nylon - though annealing nylon is an adventure on it’s own (with pretty great rewards mind you).
yes, think of the impregnated filaments as contaminated. The primary carrier, ABS, PLA PETG, etc becomes less strong because of the impregnated mateial, whatever it may be. In the case of sintered metals, one extruder 3d printers can’t get hot enough to melt the metals. In reality, the metals will melt the carrier material if it gets too hot, so its a catch 22 on filaments with impregnated materials. They will have the looks of the harder element, but won’t have the real strength. 3d printers that have more than one extruder can layer and overlap one element filaments, which will result in a stronger part. In practise this will allow you to create an outer shell of one material, and have an inner fill material of another, resulting in a parts with more desired properties.
The reality is, most filament manufacturers doing composites are just throwing a bunch of chopped fibers into regular filament pellets and calling it good. That’s not a very good way to get the base resin to bond to the fiber fill, yet a good bond is completely necessary for the part to actually get stronger when you add fiber to it. Raising modulus is easy, but actually raising yield strength is a bit harder.
I suggest not buying any composite filaments from vendors that aren’t willing to provide basic material test data. (Preferably modulus, yield strength, HDT/Vicat, and Izod.) This is why I’m a big fan of 3dxtech for composites – they publish data!
If a filament manufacturer doesn’t bother to test the material, they’re either not real engineers (polymer, mechanical, or otherwise), or aren’t intending to sell the filament for engineering purposes.
If they do test it but don’t publish results, the results probably weren’t very good.
There’s work being done to improve layer bonding, and also increase fiber length. The material I’ve tested really got me excited. Even with pliers, I had a tough time damaging 3mm thick a test part that was built vertically.