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Old 06-10-2019, 05:06 PM   #1
fartbox420
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Default Composite parts and materials: learning to make carbon fiber parts

Over the last few months i have become increasingly interested in the process of making Carbon Fiber parts and learning about a variety of composite materials and techniques. I am not an expert, but i will share what i am able to learn and the things i am able to create.

The two main materials used are a cloth material like carbon fiber cloth and an Epoxy Resin. There are many types of cloth material, several types of carbon fiber alone. There are different types of resin, but you have to make sure its Epoxy resin. These are the basics.

I Started with the easiest technique, the skinning technique. This basically wetting a part with epoxy then draping a cloth like carbon fiber over it. Making sure it lays flat and be careful not to distort the weave or the finished product have wiggly lines instead of straight lines. For this first piece i skinned one of the 'Exterior Lower Moldings' of my 04 wrx. It sits behind the rear door on the bottom of the wheel well.

I decided to use a Hybrid fabric made of twill weaved Carbon fiber and Kevlar. The fabric i bought had the Kevlar dyed blue. (note: Kevlar is a name brand by Dupont, kinda like Kleenex is to tissue. The generic name is Aramid.)





I know the lighting is not great, i will add other pics when it stops raining out.

Besides the passenger side lower molding, my next piece will hopefully be a front lip. This will be a more complicated process known as vacuum bagging infusion, where i will need to make a mold, add my fabric, and the use a vacuum to pull the epoxy through the mold to create the part.

Comments are welcome. **Also please post and share your own parts if are you have gotten into composite making.**
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Last edited by fartbox420; 06-25-2019 at 10:35 AM.
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Old 06-11-2019, 08:06 AM   #2
Homemade WRX
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Awesome. Keep after it.
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Old 06-12-2019, 11:46 AM   #3
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Here are some better pictures of the Carbon Kevlar. You can see the blue a lot better.





buffing the epoxy is time consuming, so i will put some clear over top to help with the finish and UV protection.
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Old 06-19-2019, 01:18 PM   #4
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So i made a mistake, when i clear coated it, i accidentally grabbed a different type of clear for the second coat. well, the two types of clear reacted and started almost bubbling. the surface looked i put paint remover on. So now i have to sand it down again and re-clear. A simple mistake can create a big mess and a lot of extra work.
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Old 06-22-2019, 11:18 AM   #5
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I sanded down to the epoxy and re-clear coated it.


Good enough for now.
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Old 06-28-2019, 11:32 AM   #6
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I have started the work for my front lip. I have been getting it smooth, and ready to make a mold of. The plastic lip came with molding lines and rough edges that had to be smoothed out. after sanding and filling little imperfections, i was time to make flanges for the lip, to make the mold off of. You want a bit of overlap to make it work. It gives some room for the vacuum bagging materials to stick to.



i need to tape the joints with packing tape, then fill in the edges with some sort of filleting wax so there is nowhere for the resin to make a mechanical lock and the mold will pop off of the "plug" (plastic lip).

once i have the plug ready, then it will be time for the tooling gel coat to make the first layer of the mold.
hopefully i will get more done soon, but im also doing my steering rack swap at the same time. Not enough hours in the day, either that or i need to quit my job, lol.
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Old 06-29-2019, 01:14 PM   #7
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looking awesome so far! subscribing because I've been wanting to learn how to make carbon parts for a while now.
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Old 07-02-2019, 10:31 AM   #8
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After covering the seams where the flanges meet each other, i went along the edges of the lip to fill all the cracks to make a smooth transition. I would have had to order filleting wax so i started with Plasticine then switched to wax from a wax ring seal for a toilet.



once that was dont i sprayed a coating of PVA mold release agent on the lip. I did one coat but i really should have did two. One tack coat and then a thicker coat. Some PVA can be brushed on, but i used a LPHV (Low Pressure High Volume) sprayer. Once the PVA was dry (green tinge) i started coating it with Mold Release Wax. i did about 4 coats, i think i might do one more before it start the Tooling Gel Coat layer.

Before i brush on the Tooling coat, i will take my fiberglass cloth for building up the mold and cut pieces shaped like the mold. i will do this before to save time. For videos to help learn about this process check out Youtube channels by Easy Composites and Matthieu Libeert. Both very helpful.
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Old 07-08-2019, 03:18 PM   #9
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So the Gel Coat laid down fine. And i put the tight knit fiber cloth over it.





Once that cured i began to lay down the chop strand mat cloth, thats when things got messy. Without the right tools laying down the chop strand mat is finicky and messy as all hell. I dont have picture how it currently sits. I'm contemplating whether i should add more fiber glass layers for strength or try to remove the buck from the mold.

Im also debating making the lip from Carbon/Kevlar (with blue Kevlar) or just carbon fiber cloth. I dont know if the carbon/kevlar i have is wide enough.
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Old 07-10-2019, 03:53 PM   #10
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After adding some more fiberglass, it was stronger but still looks a mess.



Oh well, time to remove the plug from the mold.







It didn't come out as smoothly as i would have liked. I think i should have done more than one coat of Tooling Gel Coat. Because of the tight angles of the lip, some parts were thin and left holes and divots in the mold where the fine fabric lifted some of the gel coat, i guess it wasn't set enough as well. I should be able to fix the imperfections with more gel coat. For a first try it could be worse, but if it is hard to get smooth, i might try to make the mold again.


Once the mold is good enough i will have to time the weather to make the carbon fiber lip. The epoxy resin (most, if not all) will have very specific usability windows of temperature and humidity. i think below 60% humidity is a big one.

Last edited by fartbox420; 07-11-2019 at 02:29 PM. Reason: Pictures
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Old 07-11-2019, 04:49 PM   #11
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updated last post with pictures.
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Old 07-12-2019, 12:50 PM   #12
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I have decided that fixing the first mold would take too much time/effort so i am going to start again. I will be changing a few things. First i will do least two coats of gel coat, sanding between coats. Then wait until it is more tacky before the fiberglass cloth.
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Old 07-16-2019, 10:43 AM   #13
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Small update, i started to make a new mold. I reduced the number of flanges used, the front is one piece. I did the first coat of PVA mold release. For a fine spray you need a gun that sprays at like 50-90 psi, something i dont have. I used a wagner motocoat HPLV sprayer. The results are al ittle spotty but after another coat is should be good enough. Then comes the mold release wax. After that, i can start Tooling gel coat.
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