ultrasonic degassing

General Composites Discussions Equipment Talk
#1

I’m running into an issue with clear gel carbon parts where I have small air/silver spots in the weave and thru the laminate. It apears my bag is good and I am well sealed and my resin looks to not have too many bubbles in it however after 30 or so parts all with the same amount of miniscule air spots I would like to perfect this problem.

All the reearch I’ve done lately on degassing seems like a natural cure. Vacuum degassing isnt really degassing…all that does is allow large air bubbles to come to the surface and with out an agitator doesn’t seem to be a cure.

Ultrasonic degassing looks to be the best bet. Any recomendations on equip for it? Best I’ve found is a dental tool style 3L for about $250 where I’ll put my mixed pot over the transducer and give it a couple mins.

I’m open to ideas.

thanx.

#2

probably isnt from degassing unless your not degassing long enough. usually 10-15 mins is needed. probably your problem is infusing too fast or poor flow media or laminate setup.

#3

I haven’t been degassing at all. Im using the green greenflow which is super fast but not sure how to slow it down.

#4

You can slow the resin flow by reducing the size of your intake line and/or partially clamping your intake line. Here is a cheap flow regulator. http://www.fibreglast.com/product/Flow_Regulator_01605_A/Vacuum_Bagging_Tools

#5

Indeed many flow media are way too fast for a proper infusion. You need to match your infusion mesh to the project (laminate thickness / resin demand)

Why not do the following:
Degas the simple way, under a high vacuum, and add a scotchbrite to the resin pot. This helps creating the large bubbles which go up and out of the resin.
Now get as good as possible a vacuum on your part. Beware that there is a point (some 20 mbar) where water cooks at ambient temperature. It might seem that the vacuum stabilised at that point, but it also might be possible that water in the fibers is cooking off. Give it some time to do so. Many times you see the pressure drop after 10 minutes, 30 minutes, or even as long as 6 hours. (especially when there is a lot of moisture / large objects / balsa wood / humid air in the storage area, etc)
Now when the water is gone, and you have done a succesful drop test, infuse your resin. After the infusion, raise the vacuum level to well above the boiling point of water, say 50 mbar. Let cure.

Another approach is the use of Dahltexx material, to get rid of air. More info on the Airtech website.

#6

If you will make it as herman said there shoulb be no further problems. Degasing the resin is the most important thing. If you use a membrane like the Dahltexx or the MTI hose you do not have to drop the vacuum.

#7

The only reason for dropping vacuum is to make sure gas does not develop from water which might be in your materials. Epoxy can accumulate some water. Keep the lid closed.

#8

Thanx guys, very helpfull. Interesting note on the water…down here in florida we have a lil bit of humidity and I did notice in my logbook that my worst speckled parts were on high humid days. So I will let that sit for a bit longer under full vacuum. I will also switch to a much smaller feed line and see if that helps the flow rate. I am infusing with polyester so 10 mins to degass may be a bit long but I may try a two stage degass before and after mixing.

thanx again.

#9

try oven drying your laminating materials before set up. It will help reduce moisture. definately degass your resin prior. if your using green flow medium try the red ( airtech has it ).

slowing down the flow… yeah probably a smaller inlet diameter.

#10

Ultrasonic degassing overkill or best way to remove air bubbles?
I wonder how much that particular machine in the video cost.

#11

One thing I completely missed: What is your infusion speed? Try slowing it down, to give the fiber more time to saturate.