I am a bit new to this type of lay-up so things I don’t believe or going as they should. I am trying to make a guitar part which looks something like a hubcap. I am trying to make this from carbonfiber and am using epoxy resin from US composite. I have a good sound mold however everytime I pull a part I do get some small traces of gelcoat on my part and I have to wet sand and polish my mold everytime to get a good surface to pull another part. My real problem is that my part never seems to be wetted enough as I just don’t get a good resin coat on my finished surface and I have several spots where there are air bubbles ( mainly in the curved areas of my part ) I notice when I am doing the infusion that when the resin reaches my exit tube to my catch pot it is foamy and seems to be a lot of air escaping from my part as the resin will rise and fall some in the tube ( I never really get a lot of resin in the tube however) I never let the resin run out on my inlet side as I clamp it off before it sucks any air. I also keep increasing the amount of resin I use and am pretty sure I am using enough resin. my part is about 10 1/2" in diameter and roughly 1/4" deep to 1 1/4 deep at the deepest point. I am using 12oz of resin and the part seems to wet out during the infusion proccess however thats not the case for some reason. I’m not sure what all info you all would need to give me some direction to go. I am using a spiral infusion tube which is about 1/8" 0r 3/16 dia and a 1/4" supply tube. My exit tubing is about 3/8" dia and the carbonfiber I am using is 3K and I use 4 layers then a peelply layer then my infusion mesh which is green and about a 3/16" or 1/4" weave I guess I found I have to place that clear perforated material on top of that as my bagging film was getting tiny leaks in it from the infusion weave when I would vacuum it all down. I also have to put pleats in the bagging material in order to get it to conform to the contours of my part and I am having some problems getting good seals in my pleats. My vacuum seems to be holding at 29Hg for about 20min and drops really slowly from there. I do not let my pump run or cycle after I clamp the inlet tube off I simply shut the pump down and seal the exit tube with a clamp as well. I do notice as soon as I do this my part with start to go from a black wetted look to a white or clear air kind of look as if all the air or something has not been removed and is moving back into the bag, I don’t know. The bag pressure seems to be holding as the bag film is extremly tight against my part, not very scientific I know but not sure how else to gauge my bag pressure after I have sealed it off. I would feel alot better if I could do a test ( without introducing resin) and my pump would not cycle for say an hour or better but that has only happened once and my part still had a few bubbles and didn’t seem to be wetted throuhly ( I had only used 6 oz of resin that time) I’d be more than happy to give you anymore info you’d need and even be willing to send someone one of my failed parts if that would help me solve my issues. I have been at this for months, actually since last fall and have even tried several different mold materials with no luck. Please am I doing anything right or what, thanks for any advise.
Mark
To my knowledge, US Composites does not sell infusion epoxy. (Or has that changed in the last month?) Also, do you use their generic green bagging material they sell? I stopped using it. I’m too new myself to offer good advice, but something strikes me… How long do you pull down a vacuum before you start? It’s been mighty humid here in the midwest, and not being patient is a big gotcha. You must boil off the moisture in the fabric, and that takes time. When it’s very dry, I pull for 45min, but when it’s humid, 90min or more. Infusion, (esp. Epoxy due to it’s long cure times), does not tolerate air leaks. If it’s not perfect, don’t proceed until it is. I know it sucks to rip it all off and redo it all again, but bagging material and sticky tape are a whole lot cheaper than CF and epoxy. 
Your time spent to do it right is money in the bank! 
You should have a zero drop in a 15 minute test if using a basic analog vacuum gauge. If you see a drop that means you have a leak and air will ruin your part. Good quality bag film is very important for vacuum integrity.
If you clamp both ports and the bag is leaking the laminate stack will rebound (go from it’s compressed state to it’s relaxed state). Fabrics that are allowed to rebound will end up being aerated. Essentially the stack becomes thicker but there isn’t then enough resin to fill the rebounded thickness. The vacuum level that was used to infuse the part must be maintained until the resin has set.
US Composite 635 is a pretty thick resin for doing infusion. I’m surprised that you are getting the laminated stack to fill.
If your bag is leaking the vacuum will suck air into the laminate. This results in an aerated layup, inadequate saturation, and thicker low Vf% laminates.
wyowindworks
Thanks for the reply, my part is wetted pretty well but you can see that it is a bit starved. I have a ester resin that I bought from US Composite but when I tried using it it left the pattern of my carbonfiber cloth in my mold and I had to sand and polish my mold so I was affraid to try again as I didn’t want to ruin my mold. Also the fact that my lay-up is black an looks wet when I’m doing the infusion and then when I clamp it off the whole thing turns kind of clear or white is that an indication of air or moisture or a leak, any thoughts.
Thanks
Mark
Mark, it sounds like you have a couple of issues: 1) Mold release, 2) the infusion
What is the mold surface made from? What release system are you using?
…then when I clamp it off the whole thing turns kind of clear or white is that an indication of air or moisture or a leak, any thoughts
Does the part come out milky colored? What bagging film are you using?
Without seeing exactly what you are talking about, the issue sounds like a bag leak. As the fibers rebound, while the vacuum decreases, air is pulled into the layup. This will turn the layup whitish. Although, if the fabric contains a lot of moisture then some resins will turn milky.
wyowindworks
Fist off my mold is made with polyester tooling resin and on the surface I used the orange tooling gel coat. I did some reading after joining this forum and found out about the mold having to be seasoned so I’m guessing that is a bit of the issue with the mold. I have only been using mold release wax that I purchased from US Composite. I have PVA but have never gotten a good surface finish when I have used it. I do however after reading up understand that I need to us it for at least 2 or 3 pulls to season the mold.
Secondly I am using 3K carbonfiber for my part so a great finished surface is a must. I understand I may need to buff and polish my part after I pull it but I don’t want to have to do anything else.
Thirdly I have been purchasing most of my infusion materials from a company in the UK. They sell the spiral tubing and the reusable tubing fittings for my bagging film. I am also buying my pealply and infusion mesh from them and I have purchased 2 types of bagging materials from them as well. I have the standard film and that film that is extremly stretchable so as not to have to pleat it. I have been using the standard stuff and pleating but am having a great deal of difficulty in getting a perfect seal. I use the sealing tape and have been buying that from a place in Calif. I have also tried a tacky tape product from a place in TX. No matter what I do I seem to be getting a leak or a few leaks as I am unable to hold a 29Hg vacuum for more than 5 or 10 min. I have tried a stethescope to find the leaks but at 51 and to much shop time my hearing is terrible so no luck. I am also using that clear perforated film on top of the infusion mesh because I seemed to have an issue with the outer edges of the mesh being sharp enough to cause leaks in my bagging film. I don’t use that white fiber material ( what do they call it air medium or something ) but have read that some guys use it to get a good air flow over the mold.
Lastly I think the clear coloration I am seeing when I clamp off the supply and vacuum tube is air coming back into the lay-up, as my part does not have a white milky surface. Actually ly the surface of my part is not really bad except it is a bit starved of resin and has a few ( about 3 maybe 1/4" sized air bubbles in it ) as for the compaction of the layers I’m not sure as I haven’t cut into it to check that but it is extremly strong and ridged. The resin that comes out of the lay-up into the collection tube is extremly foamy so is that a sign that I have a leak in my bagging film. Some how I just have this feeling it’s all about a leak.
Thanks again for all your help
Mark