Quote:
Originally Posted by troy_dietz
As a warning, Carbon Fiber filled filament is often marketed as "stronger" and "more durable" than traditional "pure" thermoplastics. This is usually not the case. While there are small finely copped bits of carbon fiber in the filament, they are often nowhere near long enough to add any justifiable strength or rigidity. That usually comes from a better formulated plastic base and not the carbon fiber. (machines that lay a continuous strand of carbon fiber are obviously an exception)
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Quote:
Originally Posted by troy_dietz
You are absolutely correct that there are some brands that have significantly increased strength and durability. Protopasta, 3DXTech, and recently, Colorfabb comes to mind. However, these manufactures are already "a cut above the rest."
Recently, the market has become saturated with inexpensive "exotic" filaments which may actually have modified chemical structures or filler materials (like carbon fiber or wood) but only so that they may trap inexperienced customers with fancy names and a slightly lower price than reputable producers. The benefits of these filaments are usually negligible for the increased price over standard printing materials.
If the manufacturer offers a sample, take it. You might be surprised, but it's still quite likely that you'll be disappointed.
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It sounds like you have quite a bit of experience using different printer filaments and how some 'exotics' are just marketing ploys, but fiber reinforced thermoplastics DO offer some amazing properties. I haven't personally used any commercial CF-plastics with a desktop 3D Printer, but I have some experience with large scale manufacturing using different plastics (mostly ABS, but some PLA and nylon variants as well) reinforced with different fibers (mostly carbon fiber, but also bamboo and flax fibers).
Carbon fiber infused ABS has a higher tensile strength than just ABS while also being slightly less dense. This translates to better strength in the x and y directions for printed parts.
However, the presence of fibers decreases the adherence between layers if you don't incorporate more advanced temperature control layer by layer. So basically, the part will be stronger in the x and y directions and have a higher yield point, but be more prone to delamination and separation between layers.
One important thing to know is that the properties are sensitive to the weight percentage of the carbon fiber. 20% is a good starting point, but I've never seen a commercial filament that provides the percent weight for the amount of carbon fiber, so I've no idea what they're using. If I had to guess, I'd say most use closer to 10%.
tldr; The inclusion of fibers infused in filament (or pellets, though I'd say for the purposes of this thread, we can assume filament) increases the structural properties of the material. This doesn't mean the CF filaments currently on the market are all they claim to be, but I've heard rave reviews and know that the science behind it works, because we see it work on the large scale.