A Deep Look at Fiber Reinforced Filament

Jul 25

In my last video I inspected a piece of carbon fiber reinforced filament using a digital microscope. I further demonstrated the risks of handling carbon fiber filaments by rubbing it against my finger and showing clear images of the fibers that were embedded in my hand as a result.

These fibers are dangerous, because they will readily puncture any skin or living tissue they come into contact with minimal force. The carbon fiber particles are extremely thin, and will pass through flesh like a hot knife through butter. As prior reading for this article, you should watch the video below. If you've already seen it, feel free to skip ahead.

I received a few common questions and comments on that video. It's definitely worth browsing through them because I can’t relay all of them in this article.

Many people shared their experience with carbon fiber filaments that was similar to what I showed in the video. Subject matter experts - people who allegedly have worked in areas involving carbon fiber and fiberglass installation, as well as one user who claimed to be an asbestos inspector and claimed there was a lot in common between asbestos fibers and carbon fiber.

However, there were a few questions and concerns that came up time many times over in the comments.

1) People wanted to know if 3D printed parts had the same exposure risks that were demonstrated with the filament.

2) People wanted to know if Glass Fiber Reinforced Filament had the same issues with loose fibers.

3) There was a common (but incorrect) belief, that carbon fiber is harmless because it is made of carbon, and we are carbon-based life forms, so it's biocompatible and our bodies should be able to break it down

I want to start by addressing point 3, because this sort of misinformation can be the most harmful, and could lead to ignore safety advice.

Carbon fiber is made of carbon in the same way that diamonds are made of carbon.

It's the same element, but it's a completely different form to what our bodies are composed of. These are not organic, soluble, or biodegradable particles. It is much more similar to fiberglass than carbohydrates, and due to the chemical stability of the fibers, they will not be readily dissolved by our bodies. What is more likely to happen is that your body will attempt to encapsulate it in a prison of scar tissue. But since the fibers are so sharp, and so incredibly strong, they will just piece through it, and move to a new location. These types of fibers can cause widespread damage to the body, especially if ingested or inhaled.

Ideally, these fibers will get embedded into your epidermis, and shed away. But if you touch another part of your body, or you eat some potato chips, or rub your eyes, or pick your nose. They can be transferred to other parts of the body where they can become permanently lodged. If they pierce through the thick outer layer of dead skin cells, known as the epidermis, they could enter your dermis, which is innervated, cause itching and inflammation.

Questions 1 and 2 are answered in the second video, which is embedded below:

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If you watched the video, hopefully it will have answered the questions about printed parts and glass fiber. My overall recommendation would be to discontinue use of fiber reinforced filaments, unless the manufacturer has clearly demonstrated, ideally with independent testing, that the fibers are safe.

Also in that video, I promised to show you some high resolution pictures of the printed parts and filament used in my experiments. Here they are. Feel free to zoom in and take a close look. Squarespace’s image hosting is excellent.

From left to right, we have the 10 samples A through I from the video
SAMPLE A (WHITE FIBERS) - GLASS FIBER ABS
SAMPLE B (FUZZY, BLACK) - CARBON FIBER NYLON
SAMPLE C (FUZZY, GREY) - CARBON FIBER PLA
SAMPLE D (SKIN TONE) - WOOD FILL PLA (BIRCH)
SAMPLE E (CHARCOAL) - WOOD FILL PLA (EBONY)
SAMPLE F (SHINY BLACK) - POLYCARBONATE
SAMPLE G (SHINY FLECKS) - GALAXY BLACK PLA
SAMPLE H (3 COLORED) - SILK PLA
SAMPLE I (JAGGED WHITE) - HIGH FLOW PLA

This is a macro photo of the Extruder Tensioning clamp from a PRUSA MK4 made of PETG-CF.

There are 3 main parts to this photo. The left side shows a raw, unfinished PETG-CF part that I received with my PRUSA MMU3. The right side shows a similar part that has been treated with a clear-coat of Superglue. The lower part of the photo shows a steel spacer that is part of the extruder assembly. Note the brushed metal appearance. At this level of detail you can resolve the layer lines, and see what the seam looks like. But lets get in a little closer so we can see the individual fibers.

This is a close-up of the same 3D Printed part. On the right half of the image you can see the effect of clear-coating has on the surface finish. It becomes glossy and the fibers .

The fibers on the left are sticking out of the print, and could be rubbed off by hand. However, when I rubbed the clear-coated section against my skin, none of the fibers came off, and my skin was protected from the fibers. Both of these claims were demonstrated in the previous video, along with a demonstration of the materials and methods used to clear-coat the part. It only took a few minutes to apply, a few more minutes to dry.

The fibers have a lot of surface area, so superglue will tend to wick onto them and encapsulate them due to surface tension. Superglue has the added benefit of strongly adhering to the fibers so even if they aren't encapsulated, they will be bonded to the surface of the part, and will be less likely to come loose.

This closeup of a part made with MultiJet Fusion looks like a static TV screen. The white particles are not fully melted to the part, and can be worked loose with a brush or with packing tape.

Closing Thoughts

Carbon Fiber has amazing material properties. It can be used to make machines stronger, lighter, and more efficient. But in my opinion, in the context of a 3D printing hobby, carbon fiber filament is completely unnecessary. Just search online and look at the photos people are sharing of their PLA-CF prints.

Customers buy their first printer, spend a little extra on some 'fancy' carbon fiber filament, and start printing off computer mice, Nintendo Switch controllers, food storage containers, fidget toys, phone cases, sunglass cases, beer cozies…

The companies selling printers and filament have a moral responsibility to educate their customers on safe usage of their products. And proactively identifying safety hazards, instead of waiting for some random YouTuber to do it. If this got through multiple layers of marketing, reviewers, and consumer protections, to the point where people are literally handing toys to kids with carbon fiber fragments hanging out of them.

What other health and safety concerns exist in 3D printing that we have not discovered yet?