Fibres · Synthetic
Carbon fibre (3D knitting)
It is not a clothing yarn but an engineering material: extremely stiff, extremely light and with no elasticity. It is knitted only in technical settings, to build three-dimensional structures and reinforcements, not garments to wear.
Translated from Italian. A native knitter has not reviewed this translation yet.
History
It was born in twentieth-century aerospace and sports research, in the search for a material with the strength of steel at a fraction of its weight. From there it entered the composites of aircraft, bicycles and racing cars, and more recently technical textiles: woven, braided and knitted fabrics that become the skeleton of composite parts. Production remains concentrated in a few large industrial supply chains, above all in Japan and the United States.
How the yarn is made
The starting point is almost always a polyacrylonitrile precursor (a fibre related to acrylic), which is first oxidised at low temperature and then carbonised in furnaces at over a thousand degrees in the absence of oxygen. What remains is a continuous filament made almost entirely of carbon, gathered into bundles (known as tows) of thousands of filaments. In technical knitting these bundles are worked as they are or combined with a carrier yarn, never spun like a wool.
Why it is prized
Its value lies in a stiffness-to-weight ratio that no classic textile fibre comes close to. A carbon knit is not there for warmth or handle but to give shape and structure: it keeps the geometry imposed on it, bears high loads and, once impregnated with resin, becomes the reinforcement of a composite part. It is the fibre to choose when mechanical performance matters, not comfort.
Dyeing
It is not dyed. Its colour is that of carbon: a deep graphite black, often with a metallic sheen. Any colour effects come from coloured carrier yarns worked in with it, or from the resin and finishes applied to the finished part, not from the fibre itself.
Care
It is not washed like a garment: it is a technical semi-finished product. Handle it carefully, because the filaments are stiff and brittle when bent, and the micro-splinters can irritate skin and airways. Keep it clean, dry and away from dust, often while it waits to be impregnated with resin.
End of life
It is not biodegradable and recycling is difficult: the main route is pyrolysis, which recovers the fibres by burning off the resin of end-of-life composites, with some loss of performance. Recycled carbon supply chains exist but are still niche. The most sustainable path remains extending its service life in the structural part.
How to recognise it
| Hand | Stiff, dry and cold, slippery and with no springiness whatsoever. To the touch it resembles a bundle of thin metal wires more than a textile yarn, and it tends to shed micro-splinters. |
|---|---|
| Look | Deep graphite black with a silky metallic sheen, without crimp and without halo. The filaments stay straight and parallel, and the whole has a technical, orderly look. |
| Behaviour | It has no elastic recovery and no memory: it does not bounce back, does not give and does not crease, but it holds the shape imposed on it. It is very strong in tension along the yarn, while it is brittle under tight, repeated bending. |
| Burn test | It neither burns nor melts: it is already carbonised. In the flame it stays stable and does not feed combustion; only at very high temperatures in air does it slowly oxidise, glowing red without leaving the melted bead of synthetics. |
| Home tests | Elasticity test: pull and release, carbon neither returns nor stretches, it stays stiff · Burn test: in the flame it does not melt into a bead and does not burn, it stays black and intact · Touch test: cold, stiff and slippery, with micro-splinters, never warm or soft |
| Confused with | Metallic yarns or lurex, also cold and stiff, but carbon does not melt in the flame · Technical aramids such as Kevlar, similar in use but yellow rather than black |
| Only in a lab | Identifying the type of carbon with certainty, and measuring its filament diameter and mechanical performance, requires microscopy and dedicated laboratory tests. |
Physical facts
| Property | Value | Source |
|---|---|---|
| elastic memory | None | research |
| sag | None (structural) | research |
| halo | None | research |
| felting risk | None | research |
| fineness (µm) | 5–7 | research |
| moisture regain (%) | 0.0 | research |
| typical shrinkage (%) | 0–0 | research |
| staple length (mm) | — | research |
measured = a measurement with a reference · iso = a standard · research = a verified source · estimate = plausibility only
Good for
three-dimensional structures and reinforcements · technical fabrics for composites · preforms to be impregnated with resin · high mechanical performance applications
Less good for
clothing and knitwear to wear · stretchy garments or ones that spring back · soft drape · beginner projects