Could need some advice on flow front


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petereng
petereng
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Hi- 1000gsm is not very thick. Some years ago I was working on mast laminates of 25-30mm thick of carbon infused. Thats thick. So 1) the big problem with carbon is that the UDs often don't infuse well. But it seems some of yours does so maybe another problem. If you hold the UD up to the light can you see through it? If not probably not the right UD for infusion. Check with your supplier and ensure the UD you have or going to have is being infused by someone 2) Dry spots are lack of vacuum.. was the 0.93 bar in the bag at the furthest part away from the vac side of the job? or at the pump?  Then vacuum decreases through the fill due to outgassing (which if you degassed right won't happen). The advice about slowing down the fill is very good. Clamp the inlet so it flows quite slow, allowing the bottom and top to fill together.  Plus use a slow medium. And lastly did you have enough resin? Did you have resin left in the pot and lines?

Plus if you fill on a slight angle say 10degs uphill this will help scavenge any gasses to the pump via the MTI tube. The dry spot maybe water vapour so leave your job under vacuum for say 1 hr to remove steam form the job. By vacuum soak I mean under vacuum pump. Some people turn the pump off which means gasses or water vapour can't be transported out of the bag. 

cheers Peter
deagrateful
deagrateful
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Nearly 10 KG of resin goes into the part. 2/3 of this is infused fairly quickly and then a second batch is mixed up and lasts until the end of the infusion. Pot life in my workshop (18 degrees) is around 2 hours (xtra slow) assuming I don't heat the resin. If the resin is warmed and the viscosity reduced then the infusion is sped up, but at the cost of a shorter pot life. I also use 2 seperate large containers to feed the resin which obviously helps to avoid any sort of exothermic reaction.
Hanaldo
Hanaldo
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3 hours!? How long is your pot life?? 
deagrateful
deagrateful
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Maybe I can help as I've just been infusing a chair core which is a 7mm hit in one go (650 gms CF either side of several layers of quadaxial e-glass). Use a slow mesh and make sure you allow the resin to continue into the part for a while after it's reached the MTI hose. For me (on a 1.5 m2 360 degrees shape) the part wet's out in around 45 mins but isn't at a reasonable VF for a cosmetic part until about the 3 hour mark. This is with a very slow mesh/ silicone peel combination (Compoflex SB RF3). This seems to work every time now but the first time I was having issues like yourself. 

Let me know if I can help at all!

Kris
Hanaldo
Hanaldo
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Jeez, and here I am tossing up between cutting my fabric at 600mm and risking not covering the entire part or cutting it at 610mm and wasting excess Tongue
gnidnu
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Thank you all so much for your replies, really appreciate your advice. Smile
Warren (Staff)
Warren (Staff)
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As already said, UD and the overall thickness is slowing things down.  The core will also slow things down.  Therefore you must slow your resin down and if necessary use a slower hardener to give you a usable pot life.

Biaxial cloth infuses ok when done slowly as there are still some gaps, pure UD is very hard to infuse.

Cutting down the excess fabric will save you a lot of material waste and resin waste. Also it means the resin has less distance to travel which is always a good thing.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
ChrisR
ChrisR
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As mentioned, that's quite a thick stack, slow that sucker down.

Do a test infusion, the same stack, the same length but less width, lay up on a sheet of glass so you can see the mould side during the infusion. During the infusion mark the top and bottom with a marker pen every few seconds, that way you can see how the resin is flowing afterwards.

For a stack that thick with so many layers I'd think you'd need to keep the vac on before infusing for at least an hour to make sure all the air is fully removed.

I've not used MTI but have read loads about it, I think in your case you need to loose it and work on the inlet/outlet positions using regular methods i.e. stopping the mesh before the outlet, just having peelply. I have seen at a demonstration a 25thk solid layup laminate infused without MTI.

edit: just looked at the attachment, sorry but WOW thats a really massive waste of materials for such as small finished product! I thought the whole mould was the finished item!
Edited 10 Years Ago by ChrisR
ajb100
ajb100
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As above, that's a large stack to be working with, slow the resin right down and give it a chance to soak through. Resin doesn't flow vertically through ud/borax as well as woven fabrics so that won't be helping
Hanaldo
Hanaldo
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Yeh that's a hugely thick laminate for infusion, especially when it is 95% uni. You would need to slow the infusion right down, and I would probably double up on the infusion mesh. 
GO

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