Infusion issues - why is this bridging happening? (w/ pic)

General Composites Discussions Composites Talk
#21

turns out the leak was coming from my ball port on my vacuum draw line. when it’s shut off but connected to the vacuum pump hose it doesn’t leak (hence it not showing up in my drop tests), but after I infuse and disconnect it does.

So with that being said, I’m still fairly certain this void/bridging isn’t a result of an air leak.
I put a part under with just peel ply and then infusion mesh yesterday and am going to demold it later. No perforated release film so I’m guessing it’s going to be a huge PITA to release, but at least it’ll show me if the problems route cause is the PRF.

If anyone has any tricks for release IM off of just peel ply without using a perforated release film I’d love to hear them. Soller said that they commonly spray their already factory coated peel ply with 770nc and it helps, so I’m considering trying that.

I’ve tried releasing with econoply E (cheap stuff) and econolease (the good stuff) so far, both with very little luck.

#22

Would a few heavy coats of PVA on the backside of the mold seal up any potential air leaks?

#23

Good find… that sort of stuff is a pain. I try to check my pump and connection, especially valves, so I can eliminate this sort of stuff. Even tiny leak can cause major headaches. I usually use clamps on my hose to shut things from intake/vacuum to I can be more sure but still always suspect. Or just leave vacuum on till cure.

As for removing the flow media. You want to leave the peel ply on and take the flow media off? I don’t use the white peel ply as it usually sticks like a mofo to the part. I’ve been using the brown, not sure what material, type peel ply and the flow media just comes off super easily. Releasing peel ply sounds odd… but if it worked, i guess so.

glad you figured it out and looking forward to seeing your successful part!

#24

I base my idea on what knowledge I have of building a forma fit to be an RTM female mould.
In this problem case above invovles the closed system but the result is the same as based on the rules of RTM mould construction and how I think you might fix it.
(Please anyone correct my wrong observations because I learn then from that)

Clearly the resin is getting blocked at that point relative to the pressure gradient behind it, and it

There are several solutions and it depends on your own equipment’s capabilities but I will give you in order of cheapest yet effective:

  1. Try sanding 500mil off of each corner of female/male where that defect is occuring. The fibres/mat are too compressed relative to all other pressure fields of the system.
    The resin is entering the catch-pot and the whole system is infused before still this last spot is not budging.

2*. If after 1. still no success then add the following is another point you can fight it:
Put some special fibre mesh at the entry port (I have seen they do this) which will increase the overall pressure of the resin front into the cavity. (Only if your mould can handle the extra force otherwise
(I am not talking out of my ass but I almost am!)
3*. Check the pressure of your resin input and will need find maximum your mould can handle without opening/leaking and then might need a stepper-pump pressure-control switch that only allows system to reach that maximum pressure/flow-rate of the resin injection.
**(I am not talking out of my ass but I almost am!)

But I think 1. might do it if you have enough tooling gelcoat thickness to sand back 0.5mm off each corner.

#25

Interesting suggestions. I’m not using a closed mold injection system though so 2 and 3 won’t work for me. I also can’t do the first one because that would destroy the geometry of my part.

I spoke to Airtech and they said they’d send me a sample of RB125 in P style perforation which has 50 percent more open area than the P16 that I made these parts with (1.27pct vs 0.8pct). Hopefully that’ll help solve some of the issue; I’ll use that in conjunction with reworking the placement of my infusion mesh.

As of right now I’m not using any PRF and have Resinflow 75 IM in direct contact with an econolease PP layer. And sweet jesus is it still a PITA to get off… I’ve found that removing the bag once the resin kicks (I tried at +4 hours) helps a lot but I won’t be able to do that during production so I’m still looking for alternatives. Let me know if you guys can think of any!

#26

Dose it matter when use different perforation style ?

I don’t think so.

#27

OMG, i have to try this. My last part was near crap due to bad mold, but my sealant wasn’t ever ordered, so i had to bag it anyway. I tried to spray Plastidip on the outside in case it was bagging holes (It’s dry as hell here)…but the Flexseal might work!!

#28

If you do try it, please let me know. Do a write up with some pictures if you can. I see this stuff, or other brands, at home depot and Osh but, haven’t tried it yet. I’m curious to how fast it dries/sets. The commercials show it working on pipers that are gushing water so, it must be fast. Would be damn helpful for those leaky molds!

#29

Yeah, I will grab a can next time I have the card. The plastidip takes several hours to cure…I just wanted something quick and thick that will plug any leak…which well, is the buggering mold anyway.

#30

Wider perf pores will allow more resin to flood the area before the infusion front reaches the end of the part and seals all the trapped air off.

#31

If the mold had a leak or if the line was leaking, then more resin faster won’t help :smiley:

#32

The mold wasn’t leaking!!!

The P1 sample came in last week. I demolded the 2nd and 3rd part yesterday, and they look good! I wanted to wait for confirmation based on the performance of the 2nd and 3rd before posting. I’m happy with the results.

Now I just have to find a more suitable infusion resin (currently using Adtech 820, ~450 cps) and figure out why it was such a bitch to demold those parts… I guess my frekote is going bad…?? :confused:

Anyways, thanks for the help everyone. It looks like the P1 solved it which might mean it was just a resin viscosity issue. Might’ve been possible to properly infuse with the P16 and a thinner resin. I’m doing research on which infusion resin to pick right now and i’ll post about it in the resin infusion selection thread in a bit.

#33

I think P16 is the most suitable for infusion

#34

thanks for the update. Glad your mold was good.

make sure to apply more release as you need it! :smiley:

#35

Looks like the fabric wasn’t pushed far enough into the mold. Try placing the fabric in from one side working in the corners and moving to the other side. Like others have said, pull low vacuum and make sure the fabric hasn’t shifted in the corners and edges, the flat surface should be okay but you need to check the tight corners, I found using small wooden or plastic round clay modeling tools to help push fabric into tight corners, just be careful not to puncture the bag. Do a vacuum check and degas the resin as well.

Form the pic of the mold, how thick is it and are you infusing using the flange? It looked pretty thin and could possibly have a micro crack or spot where it could be leaking air. If you continue to use the same mold you can try envelope bagging the whole mold, just be sure to round and smooth the corners and edges of the mold.