Hi all,
I am doing some wet carbon fiber lay up on few interior car parts. I had a look online and some specialized shops parts turn out very, very good. Some do them hand laid, some by infusion and some vacuum bagged. Which is the best?
Now my questions are:
What type of resin do these companies use? Vinyl ester/poly ester or epoxy…or it might be something else?
I did some parts myself and they turned out very good but one of them turned with a slightly hazy epoxy. I know it might have been caused by the humidity in the air (it was quite humid at the time) but could there be any other causes for hazy resin?
How do these professional guys clean or keep clean the edges of their parts? I am assuming they are masking them but there are situations when you cant mask it.
For parts inside the engine compartment ( engine covers, etc), what type of resin should I use? I dont want them to turn yellow in couple of months or even collapse from the engine temp.
Infusion will give you the lightest part with a high structural strength compared to weight. Further more it is a clean and healthy process, but you need more consumables and tools and depending on the geometry a good infusion strategy.
Vacuum bagging will give you perfect finish and lightweight parts too. You are more exposed to the epoxy than with infusion, but the results are more predictable. I would recommend this for you.
Hand layup doesn’t have the consumables and tools overhead, but will give you heavier and not as perfect (but still good) looking parts.
Hard to tell, one can use any three, but I guess they all use epoxy with carbon.
Epoxy is the most expensive but also the strongest and more important it wets out the tiny carbon fibers very well. VE and PE are weaker than EP and doesn’t give you the best bond to the carbon. They are more commonly used with glass fiber.
Combination of humidity and temperature. Contamination of the resin.
Keep the edges clean of what? Usually they make the part wider than needed and then trim the oversize after curing.
If colour is you concern then look for crystal clear resins. Generally Epoxys tend to lose their strength with higher temperatures. For parts with higher thermal resistance look for “high Tg” resins/hardeners. These will usually need to be postcured (baked) at certain temperatures and times to reach their ultimate strength.
There is no best… You need to use what you can work with. In my opinion infusion gives the most predictable results, but it can be really fiddly on small parts. However, for optical carbon parts infusion at very deep vacuum levels, then releasing the vacuum (somewhat) is the key to void free laminates. I find this very much harder to achieve with hand laminating or vacuum bagging.
Now my questions are:
What type of resin do these companies use? Vinyl ester/poly ester or epoxy…or it might be something else?
Carbon parts for interiors are seldomly mechanically stressed. For low stressed parts, even polyester is OK. The advantage of polyester is its curing speed, and the UV stability.
I did some parts myself and they turned out very good but one of them turned with a slightly hazy epoxy. I know it might have been caused by the humidity in the air (it was quite humid at the time) but could there be any other causes for hazy resin?
Very likely humidity. Keep in mind that fibers can also hold a lot of moisture, up to 4%, without you noticing.
How do these professional guys clean or keep clean the edges of their parts? I am assuming they are masking them but there are situations when you cant mask it.
I do not get the picture.Can you elaborate?
For parts inside the engine compartment ( engine covers, etc), what type of resin should I use? I dont want them to turn yellow in couple of months or even collapse from the engine temp.
Your advice/opinion would be greatly appreciated.
Fro the engine dept you need a higher temperature resin, especially near the exhaust or worse, the turbo. (best is to steer away from these parts). Fortunately the UV resistance is not so important there. I guess a good vinylester can help you out there.
Well considering that skinning the parts in Cf will be only for cosmetic reasons i dont think and extra 100gr will really count in terms of weight.
I have never worked with vacuum bagging but I am more than keen to do it if there are considerable benefits to it. I guess (and I am only speaking from hand laying point of view but I have seen both and you cant really tell the difference) the difference between hand laying and vacuum bagging is minimal given that I might be able to push the CF on to the part but I want to know if I am correct. It would involve a bot more time in the process (and expenses) but I guess a better outcome is to be expected? I have spoken to few guys that do it at a professional level and some do the hand lay up and their parts turn out really good. I guess it all comes down to experience.
Some said that they are using an industrial adhesive to have the CF onto the part as tight as possible. I have been using the actual epoxy when it reaches the tacky stage. Is this the right way to go?
Alo, one question i meant to ask: How can I best avoid the pin holes. I had couple of them on one part but the rest turned out with no pinholes which makes me wonder what I have done …ermm right.
With the vynil ester on parts, the only thing I am concerned is the force (which is not great) that is applied to install the part might actually break/crack/spider web the layers.
I guess I will continue to use epoxy. I have been using the West Systems which are quite ok, but are there any other epoxy/resins that are of a better quality? Anyone recommends anything in particular? Fiber Glast stuff look quite interesting. Any other?
If weight and structural resistance are not the most important, you can go with e-glass fibers or a natural fiber like flax and one decorative layer of carbon. You can also consider Basalt, it looks close to carbon, but is much cheaper.
True. If you do a good hand layup job the visible differences are small compared to a vacuum process. Main difference in terms of beauty is a more consistent thickness of the resin surrounding the fibers and a very little less ondulation of the fibers.
You can use this only for fixation of the first layer. For wet out of the stack you have to use the neat resin. There should be as little as possible between the layers. Many use spray on adhesive, but very little of it. When doing a hand layup you normally would do this not at once. You first cover your part with resin and then lay the 1st cloth on it and wet it out from the bottom side, you work the cloth into the resin. Then you wait until it reaches tacky state and then lay the next layer on top of it. This and all subsequent layers will then be wetted out from top with fresh resin. So if you have e.g. 5 layers and need 30min per layer the whole thing will take 2.5h.
With vacuum you do this in one shot.
A part of a part or a whole part?
If it’s only a part of a part I would guess you took too much time. If it has been a whole part it’s hard to tell, many possibilities.
No need to worry. For cosmetic parts even VE and PE are sufficient.
I don’t know Fibre Glast by myself, but you can’t go wrong with West System, it is good quality stuff.
There are many examples on Youtube, e.g. http://youtu.be/LdEjcNqyUMw.
The guys in this video have a very small and easy part, so they do every layer right after the previous. Since you asked about adhesives I assume that your parts are bigger and not as easy to lay up. If this is the case you can wait longer between the individual layers, so the bottom layers are a little more stiff when you add another one. Compaction is always done with the steel roller. You can use adhesive for fixation when going with infusion, but not for compaction. With the wet lay up you don’t need adhesive.
Never wait with the next layer until the resin is hard, this will give you mechanical bond only and not a chemical one. If for some reasons you have to wait until it is hard use peel ply on top. You then remove the peel ply before you do the next layer and it gives you a rough surface, where the fresh resin can have a good bond. If you accidentally let the resin cure, then you have to sand it before putting the next layer on.
I now see it is overlaying existing stuff. In that case you can indeed use epoxy and let that tackify, or use spray glue to install the fiber. Then go over it with epoxy, sand, sand, sand, sand and finish.
