Naked Carbon Fiber: What is it and Why is it Popular
Every now and again you hear about a car that features naked carbon fiber. For example, HyperCard maker Koenigsegg released the KNC Regera in late December 2018. The ‘KNC’ designation stands for ‘Koenigsegg naked carbon’. So what’s the deal? How is naked carbon fiber any different than other carbon fiber? And why would someone want it?
First thing’s first. Before discussing the finer details of naked carbon fiber, it is important to talk about how a carbon fiber car body is constructed. What the average person on the street considers carbon fiber is really a plastic material. It is a carbon fiber reinforced plastic (CFRP) created by combining carbon fiber fabric with an epoxy resin that, when heated, cures to form a plastic material.
Moreover, carbon fiber is not even a fabric itself. It is a fiber created by forcing carbon molecules to align end-to-end to create a carbon tow. That tow is then spun to create carbon thread which can then be woven to make a fabric or fabricated into finished parts through spinning or braiding.
Fabricating a Car Body
The most common method for fabricating car bodies from carbon fiber is to fabricate individual panels and and then join those panels together. Fabricators start with a tool (a.k.a., a mold) made of metal, foam, or some other material.
Fabricators then lay down multiple layers of prepreg materials. A prepreg is a piece of carbon fiber fabric impregnated with epoxy resin at the factory. Layers of fabric are laid over the tool until the desired thickness is achieved. Then the layers are pressed or vacuum-bagged to ensure that all of the air is removed and the epoxy is uniformly distributed throughout.
Finally, the tool and its multiple layers are placed in an autoclave. Inside they are cured under high heat and pressure. The curing process turns the epoxy into a plastic that is reinforced on the inside by the carbon fiber fabric.
About Naked Carbon Fiber
Now we get to the distinct characteristic that makes naked carbon fiber what it is. According to engineers at Salt Lake City’s Rock West Composites, a carbon fiber part fresh out the autoclave can be cleaned, buffed, and used as-is. It can also be finished with a clear coat or some sort of pigmented finish.
Those parts that are left unfinished are considered naked. They are cleaned and buffed, but that’s it. Now, why would anyone want naked carbon fiber instead of a finished product? It is all aesthetic.
A finished carbon fiber part boasts a glossy sheen thanks to its clear coat. If the part has been pigmented, it could be just about any color. But naked carbon fiber is almost always black. Why? Because the fabric itself is black. As for the epoxy resin, it is transparent.
A Different Kind of Look
Naked carbon fiber has a very different look to it. It is still shiny to some degree, thanks to buffing, but the sheen is not as brilliant as finished carbon fiber. You can also see more of the fabric underneath because there is no heavy layer of clear coat getting in the way.
This gives naked carbon fiber a more understated look. It shines a little bit, but not so much. More importantly, you can see virtually every detail of the embedded fabric. You can see the cross-weave pattern; you can see individual threads of fiber if you look really closely. And now you know what naked carbon fiber is.