PA-CF (carbon-fibre-reinforced nylon, most often Nylon 11 CF) is an SLS powder that adds chopped carbon fibre to a polyamide matrix to roughly triple stiffness and lift strength into the ~69 MPa class while staying light. We run it on our Fuse 1+ 30W in Kyiv for jigs, fixtures, UAV structural brackets and metal-replacement parts that need heat resistance and rigidity. It is strongly anisotropic and abrasive, so orientation and handling matter.
This page covers what PA-CF actually delivers on a sintering machine, the real numbers from the material datasheet, where it beats plain PA12, and where it does not. If you are new to the process itself, start with our SLS 3D printing overview.
What is PA-CF / Nylon 11 CF?
PA-CF is a polyamide (nylon) powder blended with short carbon fibres, typically around 10–15% by weight. In the SLS process a laser fuses the powder layer by layer, and the loose powder bed supports the part — so there are no support structures to remove and you can print lattices, captive hinges and enclosed channels in a single build. The carbon fibre does two jobs: it stiffens the part dramatically and it improves dimensional stability and heat resistance versus unfilled nylon.
The most common SLS grade — and the one we stock — is Nylon 11 CF. The base polymer is PA11, a bio-derived nylon known for toughness and impact resistance; loading it with carbon fibre keeps a lot of that toughness while adding rigidity. The trade-off is that the fibres make the powder abrasive and give the printed part a directional grain, which we will get to below.
What are the mechanical properties of PA-CF?
Here are the figures we work to, taken from the Formlabs Nylon 11 CF datasheet (ASTM test methods, parts conditioned at 23 °C / 50% RH). We have listed PA12 and PA11 alongside it so you can see exactly what the carbon fibre buys you — and what it costs.
| Property | Nylon 11 CF (PA-CF) | PA12 (Nylon 12) | PA11 (Nylon 11) |
|---|---|---|---|
| Ultimate tensile strength (X) | 69 MPa | 50 MPa | 49 MPa |
| Tensile strength, Z (build direction) | 38 MPa | ~ same range as X/Y | — |
| Tensile modulus (X) | 5.3 GPa | 1.85 GPa | 1.6 GPa |
| Tensile modulus, Z | 1.6 GPa | ~1.85 GPa | — |
| Elongation at break (X) | 9% | 11% | 40% |
| Flexural strength | 110 MPa | 66 MPa | 55 MPa |
| Flexural modulus | 4.2 GPa | 1.6 GPa | 1.4 GPa |
| Notched Izod impact | 74 J/m | 32 J/m | 71 J/m |
| Heat deflection temp @ 1.8 MPa | 178 °C | 87 °C | 46 °C |
| Heat deflection temp @ 0.45 MPa | 188 °C | 171 °C | 182 °C |
Two numbers do the talking. Flexural modulus jumps from 1.6 GPa (PA12) to 4.2 GPa — that is the stiffness you feel when a bracket stops flexing under load. And heat deflection at 1.8 MPa climbs from 87 °C to 178 °C, which is the difference between a fixture that sags near a heat source and one that holds tolerance. Notched Izod of 74 J/m also tells you the carbon fibre did not make the part brittle the way a glass-filled grade often would — it impacts about as well as unfilled PA11.
How anisotropic is PA-CF, really?
This is the single most important thing to understand before you commit a part to PA-CF, and it is where we see the most field problems. The chopped fibres tend to align in the recoater (X/Y) plane as powder is spread, so properties are strongly direction-dependent:
- Tensile strength: 69 MPa in X, 52 MPa in Y, but only 38 MPa in Z (the build direction).
- Tensile modulus: 5.3 GPa in X collapses to 1.6 GPa in Z — roughly a 3:1 ratio.
- Elongation: 9% in X, 15% in Y, 5% in Z.
In plain terms: a PA-CF part is at its strongest and stiffest in-plane, and at its weakest along the direction it was grown. Plain PA12 is much closer to isotropic, so PA-CF actually trades some uniformity for a big in-plane gain. The practical rule we follow in the shop is simple — orient the part so the primary load runs in X/Y, not up the Z axis. Get that wrong and a bracket that should survive 69 MPa can fail at 38. We discuss orientation case-by-case before printing structural parts.
What is PA-CF good for?
PA-CF earns its place wherever you need stiffness and heat resistance in a light, complex part:
- Jigs, fixtures and tooling. The high modulus and 178 °C heat deflection mean fixtures stay rigid and dimensionally stable — including soldering, bonding and assembly jigs that sit near heat. This is the bread-and-butter use.
- UAV and drone structural parts. Motor mounts, arm brackets, camera gimbals, payload frames — places where every gram matters and a carbon-filled nylon replaces machined aluminium at a fraction of the weight. See our defence and UAV parts page for how we approach these.
- Automotive and aerospace brackets and ducts. Under-hood and near-engine components that see elevated temperature, plus housings and air-handling ducts that need to hold shape.
- Metal-replacement and spare parts. Stiff functional components where you want to drop weight and skip machining, and low-volume spares that are not worth tooling for.
When should you choose PA-CF over PA12 or PA11?
Most SLS work does not need carbon fibre. PA12 is the right default for the majority of functional parts, enclosures and prototypes — it is tougher in elongation, near-isotropic, easier to finish, and cheaper. Reach for PA-CF only when the part has a specific demand the unfilled nylons cannot meet.
- Choose PA-CF when you need maximum stiffness-to-weight, deflection under load is the failure mode, or the part runs hot (above ~80 °C, where PA12 starts to soften). Jigs and structural brackets are the classic cases.
- Choose PA12 when you want a balanced, predictable, near-isotropic part: housings, ducts, snap-fits, general functional prototypes, and anything that needs uniform strength in all directions.
- Choose PA11 when ductility and impact are the priority — living hinges, clips, parts that must bend and snap back. Note PA11’s heat deflection at 1.8 MPa is low (46 °C); it is a toughness material, not a heat material.
For a head-to-head on the two most common decisions, see our PA12 vs PA-CF comparison. The short version: if you are asking “will this flex or get hot?”, PA-CF; otherwise, PA12.
What are the downsides of PA-CF?
We would not be doing our job if we only listed the wins. Honest limits:
- Anisotropy. Covered above — the Z-direction is materially weaker, so part design and orientation are not optional. This is the number-one cause of disappointing PA-CF parts.
- Abrasiveness. Carbon fibre is hard on equipment. The powder wears recoaters, sieves and seals faster than plain nylon, and it raises handling and process cost. That feeds into a higher price per part than PA12.
- Lower elongation. At 9% (X) it is stiffer but less forgiving than PA11’s 40%. It is not the material for parts that must absorb large deflections or repeated bending.
- Surface and colour. Like all SLS nylon it comes out matte with a fine grain and is naturally dark grey/black; it is a functional finish, not a cosmetic one, though it bead-blasts and dyes well.
- Machine availability. Nylon 11 CF is qualified for the benchtop Fuse 1+ 30W (165 × 165 × 300 mm build), so single-part envelope is limited compared with large-format SLS. For big or high-volume runs we plan the build layout accordingly.
Bottom line: how to choose
Use PA-CF when the engineering demands it — high stiffness-to-weight, dimensional stability under heat, and a complex geometry that benefits from support-free SLS. It is the SLS material we point UAV builders and tooling engineers to. For everything else, plain PA12 is more economical and more isotropic, and PA11 owns the ductile, high-impact niche. The one discipline PA-CF imposes is respecting its grain: design and orient the part so the load lives in the X/Y plane, and it will reward you with metal-replacing performance at a fraction of the weight.
We run SLS in-house in Kyiv and ship across Ukraine. If you have a part and are not sure whether PA-CF, PA12 or PA11 is the right call, send us the model and the load case — we will tell you honestly which one fits and how we would orient it.