By smp4616 - 9/19/2019 10:24:33 AM
I tried an interesting experiment yesterday, I infused a part using only bagging film and distribution line. The reason behind this experiment was that I wanted to see the difference between infusing and curing under constant vacuum vs. curing under essentially atmospheric pressure. My infusion parts using flow media, peel ply and curing under constant vacuum had an issue where the carbon seemed to be resin lean at the surface, strength was there but when applying clearcoat, the clearcoat would pinhole all over the surface, making the parts really hard to finish without adding a lot of weight. My theory was that the capillary action that allows carbon to soak up resin was being counteracted by the vacuum on the layup, as well as the force of the bagging film trying to spring back from the flow media. Though the infusion rate was quite a bit slower in my experiment, and it was really critical that the bag was completely leak free, the results appear good so far, the part looks much "wetter" on the surface, so I'll be interested to see what clearcoat does. I imagine infusion rate could also be improved by using larger diameter resin input hose. Parts of the back of the part also had some resin wrinkles where the bagging film creased, so maybe adding peel ply would make for a better back surface. There were noticeably no voids on the surface as well, I think this is due to allowing the bagged layup to go to atmospheric pressure while curing, making any bubbles that would have been apparent under vacuum collapse under atmospheric pressure.
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By Warren (Staff) - 9/19/2019 3:01:51 PM
Vacuum has little to do with it in this case based on your description. Resin infuses very slowly through carbon without a flow media. On a small sample this is not a problem. Had you tried a big sheet or part, you may find you will have run out of time before it gelled.
With infusion, depending on number of layers etc, you can end up infusing a part and what looks like a complete infusion is still a little dry. Also on smaller parts, the resin can skim across the top really quickly.
Where infusions are a little dry, what we recommend is allowing the resin feed to stay open for another 30 seconds or so after shutting the vacuum line. That allows a bit of extra resin into the laminate.
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