I am fairly new to building carbon fiber panels and I recently started vacuum bagging. I am using west system 105 epoxy resin. I spread a layer of resin in my mold and let stand for roughly an hour. Then, I place my carbon in and saturate with resin. I continue this too my desired thickness. I am using 5.7oz 2x2 twill fabric and typically I am laying 3 layers in for my panels. I place it in my vacuum bag with a layer of peel ply, perforated film, and then the bleeder cloth. I pull vacuum for about 10-15 minutes just depends on the size I am building. When the panel cures it’s like the resin pulls through the weave and I don’t have a smooth outer finish. I have put more resin over the top to try and create a smooth glossy finish and it bleeds through the entire panel. I have also used automotive clear with the same result. Does anyone have any ideas how to get a smooth outer finish? I just feel like too much resin pulls out of the fabric and the bleeder cloth absorbs it especially because everything I try bleeds through the entire carbon fiber panel. Any suggestions would greatly be appreciated, thanks.
have you tried it without the bleeder cloth and use a mesh instead?
No I have not, would that keep more resin in the carbon fiber fabric?
I am in no way an expert on the subject… I myself am newer with vacuum bagging also. But in theory it seems to me that without the bleeder cloth the resin would not wick up into the cloth and be pulled away from carbon.
Hopefully someone with years experience in this method could chime in with some input for you.
But you could always try a small test setup with the cloth and with the mesh to see if you get a different outcome.
How much vacuum do you pull ?
You are using the first layer of epoxy like a gelcoat. Let it dry completely, at least 6 hours before you put on the carbon. Letting the resin stand for an hour will only allow it to exotherm and gel, but it will not stop fabric from printing through. If you need it to cure faster, use a heat gun. But I would let that first layer gel till it is hard, then put on my fabric and vacuum. That will solve your problem.
Leave in the breather cloth, as you want it to soak up excess resin so your part is not resin rich. Getting excess resin out of your part will help to achieve a good fabric to resin ratio, and make the part lighter.
Do these steps and you should not have print through problems.
Also you should/can be using surface coat instead of resin on the mold. A surface coat may help with print through and generally is thicker to avoid sag on vertical surfaces. As wild card says, you need to let it cure properly before lamination. Generally you leave the surface coat until it is ‘Tack Free’. Meaning until you can touch it and none comes off on your finger. This can be anywhere from a few hours to more, depending on the epoxy and the temperature.
As for the dry laminate. You’re using perforated film and breather, so you are going to bleed resin out. The reason to use perforated release film to bleed resin out into the bleeder and thus creating a higher fiber volume in the part. Wet layups tend to be more resin rich so bleeding some resin away may be useful. If you want to control the bleed either get a perforated film with less/smaller holes or use a non-perf and make your own perforations. Generally I don’t do wet layups but when I do, I just make sure to use enough resin, probably like 50/50 ratio to fabric.
really sounds like you need to use non-perf. I personally don’t use perforated very often. Parts that you want a nice beauty type finish in are better off rich.
And for vacuum I pull max. Without bleeder you shouldn’t be pulling resin out of the laminate. Also you want vacuum through the entire cure process so like 4-8 hours. I usually just leave it running till I come back.
if you really want a piano type finish, you can always do post cure finishing work and it’ll get you a great finish every time.
You have to hold your vacuum steady until the part cures, you cant pull it for a while and then just let it go release
Thanks for the help guys I will definitely try letting my initial layer of resin cure before laying the fabric. I pull full vacuum now but I only run it for 10-15 mins and shut it off so I’ll let it run until the part fully cures as well. Once I finish a panel I’ll post results.
Also you should/can be using surface coat instead of resin on the mold. A surface coat may help with print through and generally is thicker to avoid sag on vertical surfaces.
What do you recommend for surface coat instead of resin? My question is by letting my first layer of resin cure fully how can I make sure it is a smooth finish? Can I use my brush to apply the resin or do I have to spray it in the mold? I am worried about small air bubbles in the first layer, any suggestions?
Hi Gilbert,
I see a few issues, which can be addressed: First we would need to know the function of your panel: cosmetic or structural? If you can, please let us know the product, (suitcase, machinery part, etc) which helps in steering you into the right direction.
First the layup:
You apply a layer of West 105/205. After 1 hour, is it still wet(tish), or tacky / rubbery? In any case, if you want it to act as a surface layer / gelcoat, you want to at least have it cured up to a fairly hard state. With 105/205, amine blush (greasy surface) can be an issue. If this happens, let cure completely, and scuff with a scotchbrite, water and ammonia.
Then the 3 layers of fabric. Make sure you slightly oversaturate your first layer (weigh your resin). Once under vacuum, this helps moving air from the first layer into the nextlayers, and into the bleeder.
The other layers go on normal, the last layer can even go on a bit dryish.
Over it goes peelply (optional) and perforated film. Do you know what perforations this film has? It typically has a number like P1, P3, etc.
P3 is the most popular.
Bleeder. In theory your bleeder should be thick enough to allow uptake of excess resin, but still allow a vacuum path.
Vacuum: Once done, you pull a vacuum. How much? The amount of vacuum needed is dependant on several factors, including:
-resin viscosity (is dependant on type, and time between mixing and pulling vacuum)
-perforation style
-cure time
-desired fiber to volume ratio
For P3 perforation, a vacuum of 14"Hg (50% vacuum) usually is more than plenty. You can go to 70% vacuum, but only if the epoxy is higher viscosity.
Also wait for about 30-45 minutes before pulling a vacuum. This helps increase the viscosity of the epoxy somewhat.
And important: Once a vacuum is pulled, only shut it off when the product is cured. Shutting off the vacuum before final cure allows the fibers to spring back, giving a very porous laminate.
Wet bagging definately is not the simplest procedure. It involves a lot of knowledge on the behaviour of your material, on laminating techniques, and processes. In that respect, infusion might be more simple, but please let us know what the product is.
Thanks Herman for the information, I am building body panels for my sprint car. They are not weight bearing but I would like they to be able to take a hit from rocks and mud without shattering. The way I have been doing it, after waiting an hour the resin is still wet for sure. Also, after I have finished my third layer I don’t let it sit at all before pulling vacuum. I pull full vacuum on every piece because I don’t have a valve on my pump to control that (sounds like I need to invest in that). Would you recommend a surface clear gelcoat instead of using the resin? I have some panels that have a lot of angles and I am worried the resin will sag and not stay even on the part. I also just use a brush to pay the resin, would I have a better quality finish if I sprayed in the surface layer?
You could either use a gelcoat, or just resin.
You can roll and tip the surface layer. The West rollers are very good in applying a nice and even surface. Otherwise a felt roller will do.
these panels are to be painted? Or clear carbon?
You will definately need to invest in a vacuum regulator of some sort.
They are going to be clear carbon finish
For clear carbon panels, I would definately investigate in infusion. Especially with MTI hose, and their recommendations (basicly: very good vacuum, and degassed resin) you have instant good results (pinhole free)
My 2 cents.
1: test a panel with less bleeder
2: and most important. LEAVE THE VACUUM RUNNING! When you shut off the vacuum, how do you know that the bag doesn’t go back to atmospheric pressure? if this happens, there is no compaction force. Then all the layers relax, and come off the mold. Keeping the vacuum on (and again, maybe less bleeder?), it will keep the fabric pressed against the mold!!!
3: when you say “outer surface” you mean the mold side, or bag side? You will never get a perfect flat bag side surface. The release, bag, etc will conform to the fabric surface. If you mean mold side is not flat, see 1 and 2.
pics?
I tried letting my first layer fully cure, then I sanded it and applied another layer and the carbon fiber. I pulled full vacuum and left the pump on until it fully cured. I had an issue where the resin didn’t bond from the first cured layer and the next layer so I destroyed a mold. I use partall #2 as my release agent because it seems to be the only thing that doesn’t allow the resin to separate when I am applying my layer of resin in the mold. Someone on here mentioned that I don’t need to pull full vacuum and I should start around 5in of mercury. That being said I can’t find a regulator to control the vacuum pump. I could tell with full vacuum my bleeder cloth is too saturated and I am pulling too much resin out of the carbon fiber.