Carbon fiber how to - quick write up

General Composites Discussions Articles and Tutorials
#1

Here’s a quick version. I will continue to work on a more detailed version:

Composites 101

This is the short version that goes straight to the step-by-step instruction. I will do a longer, more detailed write-up later on.

  1. Materials, tools, and other requirements:
    a. Carbon fiber fabric (duh)
    b. Epoxy resin
    c. Mixing cup
    d. Cheap throw away bush
    e. Disposable gloves
    f. Blue masking tape
    g. Sheet of plastic (saran wrap?)
    h. Ample working room
    i. Warm working area. Ideal room temperature is 70 degree Fahrenheit

  2. Preparation:

Caution, wear you gloves. This is going to get messy.

You will need to cut the fabric big enough to cover your plug (original piece) plus at least an inch extra on all sides. Use the blue masking tape to tape down along the cutting line and cut in the middle of the tape. This will help the weaves from separating.

Now comes the messy part. Mix your epoxy with the hardener accordingly. Most epoxy resin is mixed with a 3 to 1 resin to hardener ratio. You will also find some epoxy resin with different mixing ratio. Some are even measured by weight ratio and not by volume. It is important to measure the resin and hardener correctly or your part will not cure properly. Pour the resin first then add the hardener. Mix well for 3-5 minutes but not vigorously. Mixing too fast or too hard will cause a lot of air bubbles build up in your resin, which is always a bad thing. If you get too much bubbles after mixing, either let it sit still for another 5 minutes or so, or run a heat gun (a.k.a. hair dryer) over it to get the bubbles to rise and pop.

What’s pot life? That is the time you have to work with the resin before it starts to harden. Usually it’s around 15-30 minutes.

  1. The fun part:

Place your carbon fiber fabric on the plastic and wet both sides of the fabric with the resin using your brush of course. It is important to make sure that the resin gets soaked into the carbon fiber fabric thoroughly and evenly. Now wet the surface of the plug. Pick up the plastic sheet with the wet carbon fiber on it and place it over the plug. Press down and run your finger across the plastic sheet to press the fabric down on the surface. Use your finger to squeeze out any excess resin and air bubbles. Now lift the plastic sheet and let your carbon fiber start its curing process.

Notes: Curing can take anywhere from several hours to a week depending on the epoxy resin and the room temperature. Don’t place it in an area with too much moisture or under the sun. The fabric is cured when you place your finger over it and leaves no sticky fingerprint.

Q&A:

Question: My brush is hardened. Can I use paint thinner to wash it off?
Answer: Nope. That’s why you should use a cheap brush that you can afford to throw away after each use. I know, it adds up.

Question: Why is it taking so long to cure?
Answer: The cure time varies. You can try to speed up the curing time by putting it in a warm area. Running a room heater near it wouldn’t hurt.

Question: Ok, it’s done. But I can still feel the texture of the fabric. What do I do now?
Answer: If you want a flat and smooth surface to give you that 3D effect, you have to build up several more layers of epoxy resin. How many? It’s hard to say because different epoxy has different viscosity characteristic.

v.1.0. By Evan Nguyen for www.carbon-werks.com
Please direct any comments about this article to: info@carbon-werks.com

#2

thanks for the write-up. can’t wait to read more.

also had a question. for the process you described, i can only cover the surface of theobject in carbon fiber. is this the way you would go about making trim pieces for you car (E46 coupe)? wouldn’t this raise the surface of the trim pieces to a point when they won’t fit into the car anymore? i guess i can’t really understand the nature of the fabric until i have it in my hands but i don’t see how you can cover objects that have many contours on them, like the E46 coupe armrests.

also, what about times when u cant use the object you want to cover or u want to make more than one? what about the process of making molds?

#3

:slight_smile: I guess the write up above is good if you cover something flat. I will cover more complex issues such as multi dimensional pieces, mold making, and etc.

#4

Yes! That is what I can’t wait to read ( =

#5

im actually gonna try this with my glovebox little rectangle piece soon…

#6

Evan , good job on the write up . I need to learn how to make pdf documents… is there a website for that?.?.? hehe

Bill

#7

Bill, you just need Acrobat writer and use that to import your word document and convert it to pdf format. PM me if you need help.

#8

Ok guys part II is up - http://www.carbon-werks.com/forum/viewtopic.php?t=23

Part III will cover mold making and whatever else that I might have forgotten from part I and II.

Bill is working on something too so I will keep you guys updated.

#9

Question: Ok, it’s done. But I can still feel the texture of the fabric. What do I do now?
Answer: If you want a flat and smooth surface to give you that 3D effect, you have to build up several more layers of epoxy resin. How many? It’s hard to say because different epoxy has different viscosity characteristic.

Will subsequent layers of epoxy resin stick to the previous layer?
Do subsequent layers have to be applied while the old layer is still tacky or completely dry (or does it matter)?

#10

Ideally you should apply the next layer as the existing layer is just tacky enough so that it won’t sag when you brush on a new layer. It’s ok too if your existing layer is already cured. Some light sanding is ideal in this case although not neccessary. If your epoxy has a wax oily like substance in it then you should definately get rid of that before applying the next layer.

#11

I’m a little confused about what to do around the edges of a piece.

Scenario: trying to cover an existing E36 interior part with CF, e.g. the little piece above the glovebox.

So you cut enough fiber material to cover the piece plus about a half inch all the way around. You put the epoxy on everything and place the fiber on the part.

But you don’t wrap any fiber around the edges of the part, correct? So when it dries you’ve got half an inch of hard FRP that you have to cut off.
Or maybe not.

Do you cut the excess off before it hardens all the way? Or do you wait until it hardens and use something to cut it and then sand the edges smooth? What do you use to cut it?

As I said, I’m a little confused about the finish on the part.

Can you elaborate?

#12

You can just use the sharp razor to trim off along the edge. You can do so as soon as it cures hard enough where the fabric won’t budge or you can wait until it completely cures. With just one coat of epoxy, you should be able to trim it using a razor without a problem.

#13

I don’t understand how the Carbon Fiber layer doesn’t stick to the plug. If you cover the plug with epoxy, and then lay on a epoxy-covered layer of carbon fiber, and let it cure… how does it come apart?! Are there certain materials that the epoxy won’t stick to, or what?

#14

They sell a certain kind of plug wax I think.

#15

I would think that would be an important step in this little how-to :?

#16

I wonder about that. Do you peel the tape off? Do you cut it off since it SHOULD be on the excess, not the finished product?
What about having nice straight edges for a very complicated part, where one single piece will NOT cover the entire mold (like placing the sides of a fender as a cut out piece, and the top another, then of course, layer some more to join the seams)

#17

Resin does not bond to any type of plastic. If your plug is made of wood or metal then you’re fine. Other than that you risk the chance of delamination down the road. Some sooner than later.

#18

I don’t peel the tape off. It’s part of the excess that gets trimmed off. That’s why you should always have at least an inch or two of excess material yet not too much. The only way you can get perfectly clean line is via prepreg… other than that you’re still going to get some fray no matter what. There are some tricks that you can try though.

a. spray some adhesive (3M Super 77 for example) along the line that you’re going to cut. It’ll hold everything together so that you can cut a nice and neat line. The problem is the area becomes tacky and it’s hard to handle.

b. take a bottle of clear nail polish and draw a line along where you want to cut. Don’t use too much nail polish because the resin won’t be able to penetrate those areas and wet out your carbon cloth completely. So let the nail polish cure and cut along the line.

#19

I don’t quite understand what this means, I’m sorry…

so, if my plug is plastic, metal, or wood, I can just lay the resin-soaked carbon fiber on the resin-coated plug, and then when it cures, just remove the carbon fiber from the plug?? If its another material, then I have to use some sort of ‘plug wax’ so I can seperate the two? what about fiberglass? I’f I have a fiberglass mold and am laying the carbon-fiber upon it, will I be able to remove the carbon when it cures, or do I need the wax? Thanks for your help.

#20

Odd, coulda swore I posted this yesterday.
Anyway.

Does the blue tape come off at any point? After wetout?
Or do I keep the taped edges OUTSIDE the mold peice; if so, then what if I have a large compliated mold, where I need to lay the CF in sections in the mold, but want a nice clean edge to each piece?