First time infusion problems

Hi all,
Spent quite a fair bit of time reading up before even considering Vac infusion and after many months I finally got everything together and had a go.

I started out making a new set of molds and beefed these up with some nice big flanges to give me plenty of room.
Polished , waxed and applied PVA as per normal.

From here I laid in 3 layers of 400g Double Bias mat, peel ply and Flow mesh 115.
Put down a perimeter of tacky tape and cut some 38um bagging film, oversize and pleated in all 4 corners .
Added my vaccum source and pulled the whole lot down to around 28 inHg .

After a few adjustments , everything looked good so I mixed my resin ( Vinylester) added a splash of black pigment and proceded with what looked like a successful first go.
The following day I de-molded to find my results were not as good as Id hoped.

Pics below show pockets that the media didn't pull down to



Close up shows areas that didn't seem to wet out completly.



Any help on guiding me in the right direction to solve these issues would be greatly appreciated !

 

I have no infusion experience, but lots of experience with wet bagging. Those all look like microvoids. Typically microvoids occur, based on only my reading, from running pressures too high.

the larger voids I see are related to peelply not making contact or bridging

I would recommend you make a small sample part at a lower pressure.

Coincidentally, microvoids exist in all my parts. I wetbag generally at full pressure. So I see these everytime I make a part. I am using epoxy and the parts do not fall apart on testing. I found that lowering the pressures resulted in more air pockets and I decided to trade them for microvoids. But I am not pleased to have them.

I would say testing with varied pressure is a first start.

For the larger voids, that is peelply bridging. You cannot expect peelply to behave perfectly on non-flat surfaces without thinking it through or multiple pieces and some post mould fairing.

Also, all my troubles with microvoids seem to be more common on the mould side. When I impact test a hand laminated panel versus one with microvoids; the microvoid panel wins everytime; despite the terrible appearance.

 

I don't have a great solution on peelply bridging, but perhaps you can explain in detail how you laid/cut the peelply and others can critique.

I would say a single piece of peelply would not work here for starters.

Also, certain peelplies behave a lot differently. A thinner material is able to be pulled and moved easier than say a thicker one..

 

Bag leaks caused bubble accumulation in spots.

 

Where do you see bubbles?

 

Everywhere. The white streaks are entrained air.

Unless leaks are dealt with promptly, they tend to be trapped behind the resin front.

 

This isn't an uncommon first attempt, resin moving too quickly or too slowly through certain areas can cause the bubbles and dry resin starved spots. With the correct flow these places would fill in with resin.

How big is the part?

Where did you place the vacuum and feed lines?

What VE resin are you using?

How long did it take to infuse the part?

What was the gel time of the resin?

 

Interesting how things turn out with changing pressure. I was hoping to not use gelcoat as these would have a painted finish but previous experience hand laying without gelcoat left me with millions of tiny air pockets to fill before painting.... a nightmare in itself !

 

Maybe this is where I went wrong.
I cut the peelply and layed it in one piece .
I was thinking a spray adhesive to tack down eack layer may be a better way to go but it makes scence now, how a single cut piece of peelply would have given the results that it did.

 

I found a couple of air leaks initially but sealed these up.
I let it sit for half an hour under vaccum and there was no pressure drop before or after resin infusion . The following day, there was around half the vaccum still reading on the gauge.

 

I didn't realize the speed of resin moving though the part had an impact. Obviously too quick and the media wouldn't wet out completly.

The part is around 12inches wide x 15 inches long and the resin was pulled along the length.
Both vac and feed lines were centeral at either end and both had a silicone " Tee piece" sitting over spiral tubing that spread thr width at either end.
The resin flow seemed very evenly spread from start to finish.
The resin was an infusion only vinylester and catalyzed at 2%, as recomended.
Aprox 15 mins to infuse the part but that would be a guess, I never actually timed it and gel time would have been aprox 1 hour after shutting the vac pump down.

 

You mention shutting the pump down before the resin gels... this could be a big part of the problem. The biggest issue is vacuum integrity - you have to have a near-perfect bag. Try doing a "drop test" to check the bag is good.

Three things to look into:

Slip joints: you have to cut the fiber and lap it into outside corners. It is very hard to get a good surface if you are trying to "stretch" the carbon into corners - because it doesn't stretch! Laps are better.

Everybody is right about slowing the feed down. You also need a "resin break" of peel ply before the vacuum side to slow the resin down and let the part fill.

And the vacuum needs to stay on until the resin is gelled - dial the vacuum back if you need to but if you shut it off any tiny leaks or trapped gas will go where the pressure is lowest - in the corners and on the surface.

This is all totally normal for a first try - you'll be getting beautiful parts in no time - but it is frustrating!

 

Ideally the resin should gel within 5 minutes of when its full. And as mentioned, the vacuum needs to stay on until it's at least partially cured.