So, what exactly is PETG-CF?
PETG-CF is standard PETG with chopped carbon fibers mixed in. CF stands for Carbon Fiber. The fibers make the material stiffer and more dimensionally stable, while giving it a smooth, matte finish. Since the base material is still PETG, most of its properties remain largely the same.
The fiber content varies by brand. Some filaments contain about 3 percent, while others have 10 percent or more. More fiber usually means more stiffness, but it also makes the material more brittle and abrasive to your printer. Check the packaging to see exactly what you're buying.
Don't confuse PETG-CF with PET-CF. The latter is based on PET, without the glycol, and can withstand significantly higher temperatures. They are two different materials with very similar names.
PETG vs. PETG-CF at a glance
The main difference: PETG-CF is stiffer and more dimensionally stable, while standardPETG PETG is tougher and easier to print. Here’s how they compare feature by feature:
- Stiffness: PETG flexes under load. PETG-CF is noticeably stiffer and resists bending better.
- Tensile strength: Similar, thoughsometimesPETG-CF performs slightly better.
- Impact resistance: PETG is tough and absorbs shocks well. PETG-CF is more brittle and prone to breaking.
- Layer adhesion: PETG has excellent layer bonding. PETG-CF is slightly less effective in this regard.
- Heat resistance: PETG softens around 75–80 °C. PETG-CF also softens around 80 °C.
- Dimensional stability: PETG is good, but PETG-CF is better, with less shrinkage and warping.
- Surface finish: PETG is glossy with visible layer lines. PETG-CF is matte and hides layer lines much better.
- Color and transparency: PETG can be transparent and comes in many colors. PETG-CF is never transparent and is usually dark.
- Nozzle: PETG prints with a standard brass nozzle. PETG-CF requires a hardened nozzle.
- Price: PETG-CF is often €10 more expensive per kilo.
Where PETG-CF filament excels
Stiffness: the biggest difference
This is the reason PETG-CF exists. Regular PETG flexes when you press on it. That’s fine for a small clip, but not for a bracket meant to hold a shelf or a frame that needs to stay straight. The carbon fibers act like rebar in concrete: they hold the material in place. A PETG-CF part will flex noticeably less under the same load.
Dimensional accuracy and less warping
Carbon fiber inhibits shrinkage during cooling. As a result, large, flat parts are less likely to warp, and dimensions stay closer to your design. You’ll notice this especially with parts that need to fit precisely on or into something else. An added bonus: many PETG-CF variants suffer less from stringing—those thin threads between parts—than regular PETG.
A sleek, matte finish
PETG-CF has a smooth, matte surface that largely hides layer lines. This gives a part a more technical and finished look without the need for sanding. For housings, brackets, and visible parts, that’s a real plus.
Where is regular PETG better?
Impact resistance and toughness
This is where you pay the price for that stiffness. Regular PETG is tough: if you drop it or give it a knock, it flexes and springs back. PETG-CF is more brittle. Under a hard impact, it’s more likely to snap than to deform. For anything that gets dropped, clamped, or clicked into place, regular PETG is the safer choice.
Layer adhesion
PETG is known for its strong inter-layer adhesion. The fibers in PETG-CF interfere with that bond slightly. If your part is primarily stressed in the direction of the layers, regular PETG will often hold up better.
Ease of printing and your nozzle
Regular PETG prints on almost any printer with a standard brass nozzle. PETG-CF does not. Carbon fiber acts like sandpaper and will wear out a brass nozzle in no time. You therefore need ahardened nozzle, preferably 0.4 mm or larger. With a smaller nozzle, you run a higher risk of clogs. Both materials absorb moisture, sodry filamentis important in both cases.
Price and selection
PETG is cheaper and offers much more variety: transparent, bright colors, and glossy finishes. PETG-CF is mostly available in dark, matte shades and costs about €10 more per kilo.
Stiffer doesn't mean stronger
This is the misunderstanding that often leads people to choose the wrong filament. "Carbon" sounds stronger, but the real benefit is in stiffness. Research into PETG and CF-PETG shows thatthe flexural strength of CF-PETG is significantly higher, while the tensile strength of both is comparable. In that study, standard PETG broke in a ductile way: it deformed before it snapped.
What does that mean for you? A shelf bracket made of PETG-CF will sag less. A clip that you frequently bend open and shut, however, is more likely to break if made of PETG-CF. Ask yourself whether your part needs to stay rigid or needs to have some give. Choose PETG-CF for the former, and standard PETG for the latter.
Heat and outdoors: less of a difference than you think
Many people expect PETG-CF to handle heat much better. That’s a bit of a letdown. The base material is still PETG, which softens around 75 to 80 °C. The fibers help the part hold its shape a little longer under heat, but they don't turn it into a heat-resistant material. Will your part be sitting behind a car windshield in the summer? Then both are a gamble. In that case, look at themost heat-resistant filament.
Both perform reasonably well outdoors. PETG handles water and impact well, and the dark, fiber-filled version is slightly better at blocking UV. Will your part be in direct sunlight for years? Then ASA beats them both. Read which3D printing materials work best for outdoor use, or compareASA with PETG directly.
When should you choose PETG and when should you choose PETG-CF?
Choose standard PETG if your part:
- needs to be able to drop, clamp, or click without breaking
- needs to be transparent or a specific color
- is being printed on a printer with a standard nozzle
- needs to be functional above all else and as cheap as possible
Choose PETG-CF if your part:
- needs to stay rigid under load, like a bracket, frame, or mount
- needs to be dimensionally accurate and must not warp
- needs to look sleek and matte without any post-processing
Don't choose either if the part will be exposed to temperatures above 75 °C for long periods, or if it will be under heavy mechanical stress and needs to be wear-resistant. For the latter, you're better off with carbon fiber nylon. Read more about that in our guide onnylon filamentor in the comparisonnylon vs PETG. Still doubting between PETG and a simpler material? Then check outPLA vs PETG.
The material is only half the story
Choosing the right filament is a great first step, but it doesn't determine everything. How strong your print ultimately is depends just as much on the print orientation, the number of walls, and the infill. A PETG part with smart settings will often last longer than a PETG-CF part that is positioned incorrectly on the print bed.
Want to know what other factors are at play? Readhow to choose the right filament for your print. Already have a 3D file? Get itchecked for free: within 48 hours, we'll let you know which material and settings are best for your part.
Frequently asked questions about PETG and PETG-CF
Is PETG-CF stronger than PETG?
PETG-CF is primarily stiffer, not necessarily stronger. Its flexural strength is higher, but its tensile strength is comparable to that of standard PETG. PETG-CF is actually more likely to break upon impact because it is more brittle.
Do you need a hardened nozzle for PETG-CF?
Yes. Carbon fiber wears down a brass nozzle in no time, which will degrade your print quality. Use a hardened steel nozzle of at least 0.4 mm to prevent wear and clogs.
Is PETG-CF suitable for outdoor use?
Yes, PETG-CF handles rain and changing weather just fine, and the dark fiber variant is slightly more UV-resistant than standard PETG. For parts that will be in direct sunlight for years, ASA is a better choice.
Is PETG-CF more heat-resistant than PETG?
A little bit. The fibers help the part hold its shape slightly longer, but PETG-CF also starts to soften around 80 °C. For really hot environments, you're better off choosing a material like ASA or PC.
Is PETG-CF harder to print than PETG?
Not really. PETG-CF often prints even cleaner, with less stringing and warping. The main requirements are a hardened nozzle and dry filament.
Should I choose PETG-CF or ASA?
That depends on where your part will be used. PETG-CF wins on stiffness and ease of printing. ASA wins on heat resistance and long-term UV resistance. For outdoor use in the sun or in a hot environment, go with ASA.