Bridging problems, bubbles and more oh my! Need help

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#1

I’m not sure what the source of my problems is…

there are never any air leaks…

I massage the carbon into all the crevases as best as I can till my fingers ache, yet I still get a bit of bridging and then the bubbles…:mad:

Is the bridging causing the bubbles? shouldn’t the resin just fill in the gaps? why the bubbles?

why do I get the finer bubles/voids between the weave of the carobn in random areas all over the part?

Could it be that the resin is not thin enough and doesn’t wet everything out ??

Thanks.

#2

another picture

#3

another picture …

#4

and another…

#5

You have any pictures of the layup when its still in the bag?

While you cloth may not be bridging, it looks like the bag is. which will create a low pressure area for air to form/hide.

If the bag were 100% unbridged it would be nearly impossible for that big of bubbles to form.

#6

That and the tiny air bubbles that are trapped inbetween the carbon weave can be eliminated with the proper lay up technique. I sure it is because you are doing a wet lay up by hand? If so the first “gel coat” in the mold should be nearly dry before you start with the resin and cloth. At least this is what i have read.

#7

Are you simply vacuum bagging or are you running an infusion??? :confused:

#8

Quoted from a composite parts maker talking about the same problem.

“It sounds to me like you’re using too much resin. This is a common mistake. You’d think more resin would cause a better finish, but I think it blocks the breather, blocking the escape of air. Try laying only two layers, then bagging it. Try not brushing resin on the mould surface (or gel coat). Your vacuum is a little low, but should be okay, mine only gives 25-27. An autoclave will give a better surface finish. Many of my moulds are too big for my autoclave, but I get a very respectable finish without it.”

The other possiblities discussed were:

  1. bag bridging causing major problems.
  2. possibly not using a perforated peel ply.
#9

Are you using a resin system specifically designed for vacuum infusion? If not that may be causing your problems.

#10

I am doing infusions.

unfortunately I don’t have pics of the dry lay ups in the bag, but let me tell you , there is a huge excess of slack in the bag, I put tons of pleats strategically.

I am not doing any gel coat on theses.

I am not using an infusion specific resin, I am using a general low viscosity polyester.

thanks guys.

#11

Are you using a vacuum gauge to see if you have any bag leaks?

Sorry, just from the photos it looked like a wet lay up. Infusion is better anyway.

#12

The bags all held their vacuum :frowning:

#13

Seems to me, sorry I don’t know much yet, but the bubbles have to be from air or a gas. Air leaking into the bag or suspended in the resin or offgassing from the resin. The last part I did, trying to do a spot infusion, was porous and I could see the bubbles coming up from the cured glass surface. Could your mold have pin holes or something like that?

#14

don’t think the mold has pinholes because it holds it’s vacuum, and the surface is nice and smooth.

It kind of seems like my peel ply traps bubbles underneath it as the resin is flowing…

#15

Is the viscosity of the resin suitable for the infusion process?

#16

It seems like it should be, it infuses at a decent pace over the entire mold. takes maybe 10 minutes length wise on the part picture below…

#17

Someting is wrong with your process. Vacuum too low, resin too thick, too much hardener, restrictive flow media, etc…
That piece should infuse in about 2 minutes.

#18

RC: Are you letting the resin fully saturate the cloth before cutting the resin line off?

It is possible to “float” the bag. Not sure if thats the actually term, but, it can create low pressure points until some of the resin drains. And if it gels before that time, you might get air balling up in those areas.

#19

At 10 minutes to Infuse I see 2 problems…the resin viscocity chosen(too thick) and the long feed rather than the short run needed in most parts.
Run your resin after heating the mold with a halogen lamp from the backside…and also run the path flow across the shortest distance instead of the length.
Try this and report back.Also, stir your resin with a rod instead of a flat stick…less air entrapment.
Is it just me or has this been said on the forum 1000 times before,lordy !
Vinny

#20

Halogen lamp… who needs that if you live in Phoenix :eek: Nice idea though. I’m finding this thread useful. Maybe in the winter time i can heat my molds prior to infusion.

RC51… maybe if you don’t want to have to change resin systems you can thin it.