Large Tube - Closed split mould


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Robert72
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Hello all, posting again after working overseas for a bit. Hope you are all well etc. First of all thank you for taking time to read this, it may be slightly long winded.

I made my split mould for a large diameter tube. The mould is 300mm id x 400 od x 1500mm long. So far I have attempted to bag the layup, sealing on the on the inner mould surface. Of course this was useless because of the splits.
The next attempt was to envelope bag, I couldn't get a vacuum probably due to the bag piercing on the mould exterior.
So the next thing I was going to try was breather clothing the exterior and envelope bagging, until it dawned on me that the resin is going to migrate through the splits into the breather and make a right old mess.
So what are my options? I have considered silicon sealing the splits on the exterior and proceeding with the envelope in an attempt to stem the flow of resin into the breather. Or I could perhaps resin up the exterior and attempt to seal the bag on the interior again, basically seal the splits and treat it as a large panel type bagging.
Any thoughts on the best option going forward in an attempt to get this part complete. The second option is preferred as it will simplify bagging greatly (this is heavy and enveloping is difficult). I realise there is probably no right or wrong answer as such, however any input from you experienced moulders would be greatly appreciated. Pictures to follow:




Fasta
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Maybe consider that if there are no leaking bolt fastening holes in the flange/join area then you can run the tacky bag tape around the outside split join to seal.

Then you use regular clamps to hold the moulds together at the flange so you can then do infusion process exactly as you wish.



Another method could be to join the moulds with a resin or glue compatible with the infusion resin soley for the sake of creating a seal, it would release out of the flange area with the completed tube and then just a flashing along the tube to clean off?




Robert72
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Hi Fasta thanks for your reply, no there are bolts in the flanges, i forgot to mention in my previous post. I think that means I am going to have to tape and release over them, seal the flange with silicone and envelope, then hope for the best. It really leaves me with no options. All part of the learning process I guess. Next time i shall use a tapered mandrel!

Chris Rogers
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Can you use the seams to your advantage as vacuum manifolds?  If you infuse from the inside middles of each half and pull vacuum at the seam using some spiral wrap or flow mesh on the outside - so the seam is the air-channel?  Might be hard to get the resin to converge at the same time... Or you could feed resin in one seam and pull vacuum on the other. I have done this but the split line of the tooling had some features that made it work.  

What is the layup?  How many plies and how are you connecting the two halves?  Core?

You might be able to fill in the area between the ribs on the back with very cheap insulation foam and have that make the bag less difficult.  But its extra work...

The resin will only go where there is a path and you may be able to block it by leaving the breather on the back pulled back from the edge by a bit - and hosing the sealed back of the tools with PVA or something might help.

Do they have to be co-cured in one piece or could you layup in halves and tape together?  Or wet-bag?






Fasta
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Robert72 - 2/22/2021 9:30:54 AM
Hi Fasta thanks for your reply, no there are bolts in the flanges, i forgot to mention in my previous post. I think that means I am going to have to tape and release over them, seal the flange with silicone and envelope, then hope for the best. It really leaves me with no options. All part of the learning process I guess. Next time i shall use a tapered mandrel!

Taping over the holes will not work as the vacuum will just pull/push air through the tape edges.

Fill the holes with glue, clamp the mould halves together instead.
Bag tape to seal around the outside flange/split and then do the inside bag only infusion.





Hanaldo
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RTV silicone gasket maker is your friend here...
Warren (Staff)
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It peels off easily afterwards too. You could spend time sanding the outside of the mould to remove sharp edge issues.  Then of course you could envelope bag the whole thing as suggested before. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
Robert72
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Thanks all for your replies. I have breathered the mould external for envelope bagging.
The layup is 4 plies of 200g, 3mm of 3D core PET 100, 4 plies of 200g.
Not sure about the best infusion arrangement here?
I have peel ply overall, the first third has infusion mesh, the middle third is bare to act as a brake, and the last third has mesh. I think this might work or should I use mesh over the whole lot? I have spiral tube going around the circumference at the inlet, should I also have it at the outlet?

Regards.
Robert72
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Hope my description makes sense? If not this picture might help....


Hanaldo
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Mesh the whole thing, and just cut the mesh back about 3" in front of your vacuum connector. You don't want your brake zone in the middle, remember that the resin is flowing through the entire part, not just the flow front. So if you have a brake zone in the middle, the resin can not speed up again once it hits the last third of mesh, it is still having to flow through the brake zone. 

You also don't really need a large brake zone here, the resin should flow quite evenly through the whole part. So all you really want is to slow the flow for the last part of the infusion.
GO

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