vacuum infusion laminating

[Danielsan]

It will be the last one, what is limited by capacity?

could they be used for RI on small parts, 400l/min gives some 24cubic meters an hour?

greetz,

[Rod T]

I am preparing to build an F32 using Divinycell and carbon fiber with epoxy. I heard about resin infusion and became enamored in the possible advantages of using this method. I set out to do some trials and to study the process. Using ½ diviycell and 10.9 oz carbon on each side, with peel ply, release, and flow medium, I set up a bag around the whole thing, with vacuum and feed lines. I then infused resin and it went well. While that was running I hand laid up some CF on some foam and peel plied it. I did use two slightly different epoxies from the same place, a low viscosity for the bagged and a higher for the hand.
Today, after they set up but they are not fully cured I cut out some 12” x 12” pieces and weighed them. Low and behold the hand layup (270 gram) was lighter than the bagged (290 Gram) . I then pulled the CF off the foam(it was easier to pull off the bagged than the hand) and weighed the foam and saturated CF. The saturated bagged CF weighed 108 gram for a 65% fiber to resin ratio. The saturated hand layup weighed 172 grams for a 40% fiber to resin ratio. The foam however was vastly different with the bagged weighing180 grams versus the hand at 98 grams. The difference in the stiffness was real apparent with the heavier, bagged foam being much stiffer.
I then did some destruction testing which could be flawed as the epoxy was not heat cure. I took 2” wide strips 12” long and supported them on two supports 10” apart. I pulled the middle down with a 3/8 dowel centered across the strip, pulling uniformly. They all broke on the compression side. The bagged broke at 72-75 ponds and the hand broke at 92 lbs.
My questions:
Do my findings seem reasonable?
Is divinycell the wrong foam to use with VIP?
Is there any advantage to the foam taking on more resin?
Any comments or advise?

Some weights per square foot
Bare foam- 90 grams
CF 35 grams two sides 70 grams
Total 160 grams

Infused panel
Foam 180 grams
CF 54 each side 108 grams
Total 290 grams

Hand layup
Foam 98 grams
CF 86 each side 172
Total 270 grams

Rod

[Ron Cook]

Some forms if not desgned for infusion have out-gassing problems. Many of todays infused laminates are done with the core either beening Balsa or Corecel because they don't hve out-gassing problems.
Have a look at prepregs as it sounds like you truly want to do a first class job.

The F32 is a super boat

Ron Cook

[wet feet]

With infusion,what steps do you need to take to eliminate air on both sides of the core? I have seen a few samples where an air pocket was sealed in place by the closed cell core foam being pressed into a concave shape.My feeling is that the same amount of consideration of flow needs to go into the resin feeds that a complex casting gets to ensure that molten metal fills every part of a sand mould ie numerous gates and vents.

[HWL]

Originally Posted by Rod T

I am preparing to build an F32 using Divinycell and carbon fiber with epoxy. I heard about resin infusion and became enamored in the possible advantages of using this method. I set out to do some trials and to study the process. Using ½ diviycell and 10.9 oz carbon on each side, with peel ply, release, and flow medium, I set up a bag around the whole thing, with vacuum and feed lines. I then infused resin and it went well. While that was running I hand laid up some CF on some foam and peel plied it. I did use two slightly different epoxies from the same place, a low viscosity for the bagged and a higher for the hand.
Today, after they set up but they are not fully cured I cut out some 12” x 12” pieces and weighed them. Low and behold the hand layup (270 gram) was lighter than the bagged (290 Gram) . I then pulled the CF off the foam(it was easier to pull off the bagged than the hand) and weighed the foam and saturated CF. The saturated bagged CF weighed 108 gram for a 65% fiber to resin ratio. The saturated hand layup weighed 172 grams for a 40% fiber to resin ratio. The foam however was vastly different with the bagged weighing180 grams versus the hand at 98 grams. The difference in the stiffness was real apparent with the heavier, bagged foam being much stiffer.
I then did some destruction testing which could be flawed as the epoxy was not heat cure. I took 2” wide strips 12” long and supported them on two supports 10” apart. I pulled the middle down with a 3/8 dowel centered across the strip, pulling uniformly. They all broke on the compression side. The bagged broke at 72-75 ponds and the hand broke at 92 lbs.
My questions:
Do my findings seem reasonable?
Is divinycell the wrong foam to use with VIP?
Is there any advantage to the foam taking on more resin?
Any comments or advise?

Some weights per square foot
Bare foam- 90 grams
CF 35 grams two sides 70 grams
Total 160 grams

Infused panel
Foam 180 grams
CF 54 each side 108 grams
Total 290 grams

Hand layup
Foam 98 grams
CF 86 each side 172
Total 270 grams

Rod

now I am really confussed. I was under the impression that one of the main reasons to use infussion in boat manufacturing was 30-50% less resin usage resulting in lighter weight boats. From your experiment it seems to be heavier than hand lay up.

[Rod T]

The CF glass is much lighter but the foam took on a lot more resin when infusing.
Hand layup I was 40 glass 60 resin and VF I was 65 glass 35 resin (right whjere I had hoped).
The thing that bothered me more was that the hand layup was stronger by 25- 30 %. My test may not mean anything but I think it does.

The foam could have outgassed some but I saw no signs that it was a problem just that resin migrated into the foam surface.
Thanks for inputs
Rod

[Rod T]

Regard question on steps to bag both sides- I repeated the CF,peel ply,release fabric and breather with feed lines and vacuum lines both sides. I bagged all the way around rather than bag to a surface.
Rod

[yokebutt]

Rod,
The lower strength in your experiment might be due to the skins becoming thinner when compacted with vacuum, and thus less inclined to stay straight in compression.

Divinycell gaining extra weight from infusion is curious, since it's a closed-cell foam, only the cut cells on the surface should, theoretically that is, fill with resin. There is, of course, always the possibility that the foam is reacting to the resin, been known to happen.

Good luck with your project,
Yokebutt.

[Ron Cook]

HWL,
Did you pre-coat the foam with a hot coat and let it kick before using it in the infusion experiments?

If air is being traped in the laminate where those pieces de-bulked properly first? You have to de-bulk your laminate stack by pulling a vaccum and holding it for awhile before you can open the resin manifold and let the resin in.

The resin infusion process require a very high vaccum.

Ron Cook

[yokebutt]

Rod,
I should add that I do think a compacted laminate is preferable, even if you just use bagged wet lay-up. Keeping air bubbles out and maintaining an even fiber/resin ratio is important for the final result to be good.

Yokebutt.

[henrikb]

I'm currently helping a friend building a small trimaran. The hull is 8mm divinycell (H100) with 400g carbon on each side.
The core is shaped and laid in a female plug. We discovered that the 8mm core leaks air right trough! Pre-coating is not enough, the core surface needs to be filled with thickened epoxy and then faired, just to seal the surface!
So I can understand that the core will soak resin if not properly sealed, closed cells, "yeah right"...

[Rod T]

Thanks for the comments,
Pre coated with a hot coat. No I am using epoxy.
High vacuum- 29 inches of mercury for about an hour before infusion.
Lower strength - I agree that the compacted laminate could not take compression as well. And I agree that it is a better product.
Divinycell gaining weight did surprise me - I am doing a hand layup, vacuum bagged at 15 inches of Hg to see if the higher vacuum afected the foam taking on resin.

Divinycell leaking- I put a test bag, sealed to the foam, on one side of a 2'x4' chunk of 1/2" foam and it drew down to 29 " Hg and held good, with the sealant tape sealing to raw foam.
Rod

[War Whoop]

Originally Posted by Rod T

Thanks for the comments,
Pre coated with a hot coat. No I am using epoxy.
High vacuum- 29 inches of mercury for about an hour before infusion.
Lower strength - I agree that the compacted laminate could not take compression as well. And I agree that it is a better product.
Divinycell gaining weight did surprise me - I am doing a hand layup, vacuum bagged at 15 inches of Hg to see if the higher vacuum afected the foam taking on resin.

Divinycell leaking- I put a test bag, sealed to the foam, on one side of a 2'x4' chunk of 1/2" foam and it drew down to 29 " Hg and held good, with the sealant tape sealing to raw foam.
Rod

I am at a loss for words here in 25 years of wet bagging and plus now Owning my own Infusion system I have never seen results like this?? My burn tests indicate @30% resin (glass laminate) SP Ampreg 22 and vector ply 17+18 OZ fabric.Better go rethink something.

[HWL]

Originally Posted by Ron Cook

HWL,
Did you pre-coat the foam with a hot coat and let it kick before using it in the infusion experiments?

If air is being traped in the laminate where those pieces de-bulked properly first? You have to de-bulk your laminate stack by pulling a vaccum and holding it for awhile before you can open the resin manifold and let the resin in.

The resin infusion process require a very high vaccum.

Ron Cook

ron,
rod t, is the one with the experiment. thanks for your input though,hwl

[Rod T]

Hey War whoop,
You sound like you have had a lot of experience with resin infusion. Have you done it on foam cores and checked the total weight and then individual parts weight. I got my resin content in the laminate down to 35% but the divinycell took on a lot of weight- i.e. it doubled its weight.

I just weighed a hand lay up/ vacuum bagged (at 18 " Hg) and it weighed 2/3 of the resin infusion because the foam did not take on as much resin. It was 204 grams/ sqare foot versus the 290 of the infused and the fiber/resin ratio was the same.

IS there something wrong, that I am missing? Is this an abnormal result or is it due to the divinycell or my screw up.
Thanks for comments.
Rod T