Talk Composites - The Forum for Advanced Composites

Bubbling at the end of the degas

http://www.talkcomposites.com/Topic39862.aspx

By Raf4C - 2/11/2021 10:19:17 PM

Dear all, I need again your precious advices. I started a couple of years ago to make composite laminates by using vacuum infusion with easycomposite equipment and materials. I am satisfied of the laminates that I obtain. However, last week I experienced a new problem. I was degasing the resin+hardener before the infusion (I use the EC20 pump with the big vacuum chamber), the bubbling phase was almost finished, and then, suddenly, the bubbling started again for few seconds. Afterwards, it started again and then stopped after few seconds. This was repeated few times before I stopped the process. It was the first time that this happened. However, I decided to make the infusion with that resin and the results is that I had some voids in the plate that I produced (of course the bag was super OK). Anyone of you can help me regarding this problem? Any Idea?
By Raf4C - 10/26/2022 12:29:19 PM

 
Chris Rogers - 2/16/2021 2:39:23 AM
I agree with Hanaldo on the slow it down thing.  Over-running trapped air, vapor or whatever can cause it to get trapped and make voids.  Was your material all very dry too?  You don't say what your laminate is but is there core?  When you're sure leaks aren't the problem I always look to vapor issues next... and sometimes its a thing.

I disagree with the whole Easy Composites method of turning off the vacuum after the part is filled. 

Documented in this post I did last year:  https://explorecomposites.com/articles/lamination/troubleshooting-vacuum-infusion/ 

It can clearly be done both ways so maybe I'm making too much of it but my opinion is that if you have any leak or trapped air issues this will make them worse.  Degassing is a good idea if you need perfect cosmetics and have the time.  In theory is shouldn't be that useful but it can make a big difference sometimes for reasons I'm not 100% on. There's something fishy about your mix still bubbling after you thought it should have stopped.  If there's gas or volatile stuff in there it will just keep coming.  The vapor pressure vs. vacuum level could be causing moisture to be released only after the vacuum level gets really high - after your normal trapped air bubbles boil off and the resin should be fine.  Shouldn't happen with new resin though! 

Check this out from Vacmobiles in NZ - excellent description of the vapor issue: https://www.vacmobiles.com/vapour_pressure.html

Good luck!

Dear all. Sorry for my late answer, but I want to update you and close the issue. By using a resin break with breather, I obtained laminates without defects.

Thanks a lot to Chris and Hanaldo!!