I recently attempted to infuse a mold for a automotive fender. It had 3 layers of surface coat then 11 layers of 5.7 oz 2X2 twill. There are a lot of dry spots in the mold. When infusing I envelope bagged the mold. On top of the carbon were 1 peel ply, preforated plastic and the geen flow media. From above it appeared to flow well and completly wet out. But after debagging I found dry spots as big as 4"X4". Any ideas? I might ad that each layer of material was placed using 3M 77 adhesive.
Hi,
Same goes to me. when applying the 3M adhesive, we might fount that the surface feel tacky and seem dry spot occured.
I’m sure others will ask so I might as well be the first.
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How long was your infusion time
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Do you have any pictures of your dry spots
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What epoxy are you using
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Have you ever had this issue before with this many layers
Infusion time was about 20 minutes. Don’t have any pics of the dry spots and not sure they would show up in pics. I used Adtech 820 epoxy. In the past I have done wet lay ups on these molds. Most of my previous infusions have been 5 layers at most. An employee new to this work did the fiber layup and I suspect there was a lot of 3M 77 used.
More questions:
-what perforated film was used?
-what flow mesh was used?
Pictures would be great.
Might be a 3M problem. I know that you are goog and know what you are doing so I don’t think you made any classic mistakes.
The 3M. stays very tacky, like the airtac2 and can closes the way for the resin when you use too much and the laminate is compacted by vacuum. This can cause not complete saturated spots.
Another thing that might went wrong is the use of low perforation film, and fast flow medium.
Carbon is very slow at impregnation. Choose a slow infusion medium.
Herman, I used p preforation plastic and green flow mesh. Thanks for your help. I suspect the 3M 77. The employee doing the layup seemed to have used a lot. I really wondered about the number of layers being a factor.
Best thing is to have the employees pay for the spray glue themself…
Green flow mesh is not much of a help: I have 4 different green ones (at least)
Could the green infusion mesh sold by easycomposites ltd be considered a fast infusion one for?
Did not see a green one?
Sorry Herman, I’ve been away from my computer. Flow media is Airtech greenflow 75.
Thats nox a wooven one if I am correct. That may also be a little fast for a small part, but if you have perfect vacuum, degased resin and use the MTI hose it will also work.
Dominic, I have some airtech resin flow 60. Am I correct in thinking this is a slower infusion mesh and may help my problem? Also perfect vacumn has been difficult due to the complexity of the part. Usually around 25inches of vacumn. These are molds.
Can you maesure your absolute pressure?
No, I don’t have a gauge for absolute pressure.
That helps a lot! I can recomend the Greisinger GDH 200-14. Not too expensive and also used by most professional companies.
@ 25inches guage pressure, you need much more vacuum to ensure successful infusions. They can be done @ lower vacuum, BUT, when you have very strong vacuum and a very tight vacuum, everything else is much more tolerant to mistakes such as poor infusion strategy, dry spots, poor wetout etc… a strong and tight vacuum pays better dividends than anything else.
On speed of Airtech infusion meshes: did I already post this one:
That depends on your location;) That why I don’t like to work with relativ pressure, even it changes from da to day.