Hello Everyone!

Great to see this forum. There are lots of good posts and helpful people, encouraging to see!

I'm new to the forum but have 20 years with composites.

I'm about to build a vacuum table for curing pre-preg parts.Usually cured around 90 degrees.

The table will be about 9m x 4m. Steel frame with composite top

I was planning on a 8/10mm solid carbon top. I'm starting to think a cored panel would be better, stiffer and flatter. My concern is thermal insulation.

Does anyone have experience building a vac table of this size and use?

Any thoughts and help would really be appreciated.

Have a great weekend.

Thanks

Have used solid, balsa cored and aluminum honeycomb cored - not as big but close.  Are you doing boat things?

For 90C, balsa with 2mm-ish carbon skins infused will work ok but there will be some insulating issues if you're trying to ramp up fast but for large cored panels and slow cooks it's fine.  20mm balsa is a nice mix of stiff enough and not too thick.  Its just less likely to warp or have issues with deflecting when you move it or place heavy things on it.  Easier to damage though.  25mm vs 10mm - the stiffness is massively different.  8mm sounds too thin - 12mm might not be too much if you go single skin.  The metal frame will need to be attached so the pieces float as the different CTEs of the material happen - it can be a lot at 9m long!  Sliding "clips" with bonded-head bolts or a silicone adhesive might work. 

Aluminum honeycomb is the best because it conducts heat beautifully and you could have the stiffness of 50mm thick core too - but to do that you pretty much need a table already so you can do it with pre-preg.  Maybe you could do separate cured skins and bond with high temp adhesive but it would be a project.  

I've found getting a really big flat mold is a giant hassle in itself!  If you have that then I don't think you'd have a real problem with any of the options - they just do different things well.

Glad you like the EC! project - still baby steps but its been fun so far and I'm learning tons!  

The balsa is strange because you'd think it would behave badly - and it is tough to control moisture in infusions compared to foam - but once laminated it seems to be pretty stable.  It won't take 200C but for the under 100-110C range is seems pretty good.  Plenty of people who know more than me choose it!  Using a high Tg resin like the Gurit T-prime or similar is a good idea - and giving it a good post-cure on the mold to at least to 50 or 60C.  The skins need to be thick enough to handle use - at least 2 or 3 mm.  And you want the densest balsa you can get. 

I did have issues with unsupported post-cure and warping with one table but it was more of an uneven heating issue - ended up crowned by 1-2mm which was a bummer!  I'd also recommend making the flanges around the edge as deep as possible - I learned that 50mm is not enough!  100 would be better.  You're in bigger table territory then I ever got - I hope it goes well.  Would be interested to learn what you decide to do core-wise and how it comes out!