(UPDATE 1/16/18 – Since we received so many responses to this blog, we revisited the topic. Read here.)
Without being directly informed about wet and dry carbon fiber, any normal individual may overlook the differences. Although the desired look is purely personal preference, the design, manufacturing, and care of wet and dry carbon fiber differ greatly. The term carbon fiber is widely used to describe these similar looking panels that are effectively lighter in weight than their metal or plastic counterparts. There are differences in the way in which the panels are made, the ingredients used to make the panels, and the structural design that effect each panel’s strength, weight, and inevitably their cost.
What is Wet Carbon Fiber?
Wet carbon fiber is the carbon fiber that has that overall glossy finish to it that you might see on a high end Mercedes, for example. Generally cheaper than dry carbon fiber, wet carbon fiber can be produced mainly in one of two ways: painting or infusion. Painting: No matter how carbon fiber is made, there are certain quality controls in the manufacturing to ensure that it doesn’t just fall apart. However, the painted method for wet carbon fiber seems to be the loosest on those quality controls. On the other hand, it’s also the cheapest option for the manufacturer and consumer.
This process involves painting an epoxy onto the woven carbon fiber structure and curing it with an exterior heating source. This is the least effective way to cure and properly bond the epoxy. This process results in a finished product that has a varied consistency in the epoxy distribution, weight, and strength. Even the slight imperfections in the epoxy during this curing process can result in drastic drop offs in structural strength. Infusion: This particular method involves using high amounts of pressure and a vacuum (clearly not a cleaning vacuum, but a vacuum in which there is absolutely no air). While the carbon fiber is weaved, an epoxy is applied to the surface and with the high amounts of pressure and a vacuum, the epoxy is pushed through the fibers until the consistency of epoxy throughout the fibers is measurably accurate. The structure is then cured and tested for approval.
Dry Carbon Fiber:
Dry carbon fiber is quite a bit different. It costs more but is roughly 70% lighter than wet carbon fiber and is just as strong. The reason that dry carbon fiber looks “dry” is because it’s the most strict in terms of quality control. Dry carbon fiber is made by coating each specific weave with a appropriate amount of epoxy while it’s being made, before it has set or cured. This optimizes its strength and limits the amount of unnecessary epoxy in the structure. This is how it significantly cuts down on weight. Because the epoxy is not coated on the surface and baked in, it has that dry look to it. Because dry carbon fiber is so much more expensive, you’re most likely to see it only on performance cars that are enhanced for the track.
How to Clean and Protect it: Wet carbon fiber, as you may have guessed it, looks wet and glossy. This makes it perfect for a nice poly sealant to protect from water spots, hazing, and other blemishes. If these blemishes do occur (as they do sometimes straight from the factory), use a carbon glaze or polish to remove them. With dry carbon fiber, because it doesn’t have that gloss, you surely don’t want to add one to this finish. So using a matte cleaning kit would do a great job in protecting that look. This matte kit refers to the soap to wash it as well as the sealant for long term protection.
Totally wrong. (Carbon fibre manufacturer talking).
You can make wet carbon fibre having matte surface, and vice versa, looks make no difference at all.
Wet carbon fibre means carbon fibre has been impregnated in epoxy by hand, and ususally cured in an oven, or even at room temperature, and the terminology of “wet” carbon fibre is beceause in the process of manufacturing the part, you actually have to manually “wet” the carbon fibre cloth with epoxy. Infusion is a wet carbon fibre technique wich consist of infusing the carbon fibre with epoxy resin by “soaking” epoxy into it while the part is under vaccum pressure, wich often produces better results when mastered than just applying resin directly onto the cloth while laying it up into the mold.
Dry carbon fibre is a completely different process, wich consist of having “pre-impregnated” (also reffered as prepreg) fibres. This means the carbon fibre cloth is already impregnated by resin by manufacturer. Prepreg carbon fibres usually need to be stored at -20°C to not cure by themselves at room temperature. Then, in most cases, the prepreg part is cured in an Autoclave. This results in better quality parts for various reasons, mostly beceause more pressure applied on the part during vaccum, and thus reducing the resin/fibre ratio needed in the part. This is reffered as “Dry” carbon fibre beceause you do not actually need to manually “wet” the carbon fibre witih epoxy since they are already pre-impregnated.
Anyways, the fact you have a matte or glossy finish actually makes NO difference at ALL. You can apply a glossy layer of gelcoat to a dry carbon fibre part, and you can have a matte finish in a wet-layup process. Mostly, the glossy/matte finish is depending if your mold has a matte or glossy finish, or you can just simply grit with soft sandpaper a glossy part to get a matte finish.
Dry carbon fibre is a very costly process, beceause first, you need an autoclave, prepreg carbon fibre is way more expensive than just buying carbon fibre cloth and epoxy, and then, the molds and vaccum tooling need to be of higher quality and high temperature resistant since prepreg usually need to cure at higher temperature than usual lamination epoxies. For example, you can realise a mold for a “wet-layup” process with just a gelcoat and some polyesther, while you’d use an aluminum machined mold for high temperature autoclave applications.
Mostly, the strenght of carbon fibre depends of the density of the part, wich is greater in dry carbon fibre parts beceause of the autoclave curing process, is highly dependent of curing temperatures and propreties of the epoxy used itself. Strenght comes from the carbon fibre itself, so, more fibre – less resin is a must, but not too low to avoid “air voids” into the part wich would cause structural issues. Autoclave allows for a lower resin/fibre ratio without having structural problems beceause the higher pressure in the autoclave vaccum increases the “compactation” of the part.
For maintenance, it actually depends more if the part has a gelcoat or a varnish applied to it or not. If not, the fibres are closer to the surface, and you’d risk to damage it by using inappropriate products. Gelcoat-Varnish parts are actually better protected.
^ Give this man a medal.
I collect (semi) high quality pocket knives. They usually have titanium handles. I just ordered my first flipper with carbon fiber scales, I’ve never owned anything that had carbon fiber at all. This material is completely new to me. I believe they are dry carbon fiber scales since it’s a dull rough looking finish. Not the shiny plastic looking wet type. How would you suggest I care and maintain the carbon fiber? Do I need to do anything to it at all besides keep it clean? Is there anything that I absolutely should NOT do to it? For example, Does it absorb water if it got wet by accident?
Basically, it is carbon fiber trapped in epoxy resin. So, it is like plastic. Don’t use solvants on it. Do not sand it otherwise it will screw the surface finish. It is resistant to temperature to a certain limit (depending on the resin used, but i wouldnt expose it to more than 50°C for a random carbon fiber part), and the resin can haze if exposed to sun for a long time (unless it is an uv resistant resin, but there is not really any way you can know about it).
What are the properties of carbon fiber.
https://uploads.disquscdn.com/images/5d8eb9e57cad5e472a7c27c2ba90cee1bc5ed5c33c765e872f0a15dd9c772797.jpg Ay yo… RESPECT! One question… with “Dry Carbon” can one get a few coats of clear coat on the parts to give it more protection and shine? Looking at getting some CF body parts for my hog to drop some good weight.
Yes, simply apply a shiny clear coat to a “matte” cf part and it’ll be shiny.
hi Jean. I just want to learn prepreg process’ parameters. Do u know it?
Wow Jean.
That was some education right their. Thank you for making this a lot more understandable.
If I may ask a question or two?
I’ve been experimenting with a new design of drone frame using the lesser quality 3k 2/2 twill carbon fibre (c.f.) called Black stuff from Easy composites. Cheapest option at the time.
So, I’m hand laying up on a two piece mould (due to the really tight Vs I’m expecting to achieve with 14 layers of c.f.).
So, after curing I do get the shape I want with its strength but can’t seem to get a glossy finish.!
And second. After curing the cut out shapes for the frame are solid until heat is applied for shrinking down the heat Sleeving then the c.f. bends like spaghetti.
P.s. I’m not curing in oven. Just at room temperature.
Can you give me any advise please that won’t cost the earth?
Thank you in advance.
the strenght of carbon fibre depends of the density
it also depends on the resin you use. Good resin hold different layers of fabric super close to each other so the physics will do the work, each layer will bite each other to hold the shape they have. Also good resin itself can be harder than other.
Just add on, all others are right.
He did specify that the strength also depends on the properties within the epoxy
i couldnt make prepreg stuff because of i dont know and find its process parameters. i just want to make simple speargun for myself. Do you all help me please?
Check out easy composites they have some tutorials
Why do people write articles on stuff they know nothing about…. The same carbon fiber is used to make prepreg as regular cf fabric.
You can measure and add precise amounts of resin regardless of the process.
Part strength comes from design. Parts made with prepreg are no stronger than parts made by adding the resin yourself, if you know what you are doing. Using heat cure resin (instead of room temp) allows you to increase strength by debulking but that works even if you add the resin yourself. There is no magic with prepreg
You can heat cure, cure under vacuum, compression mold or use an autoclave with any process.
I make my own prepreg with heat cure resin and get better results than the overpriced commercial prepreg.