Pinholes in surface after resin infusion 2

[crud]

Please help me before i go insane... After every infusion i do (practcing on glass using carbon fibre and plain weave e glass) There are small gaps between every tow in the weave. I have tried everything i can think of to stop this. I am using carbon that is stored in bubble wrap, epoxy infusion resin, i acheive full vac and no loss of vacuum. As i do it on glass i can see where the problem lies.... During infusion it works perfectly, but as soon as i clamp the feed line small voids form in the weave. I also de gas the resin for 10 minutes first. Any help would be very much appreciated.

 

[crud]

Thanks for this mike. I thought i had got the process sorted untill i tried to make a carbon bonnet vent in my new mould. It came out sub standard. But when i was doing the flat sheet i was sort of doing what you had just described. On my new mould i have about a 5 inch flange around the part for the bag. But even this seems to be too small. I think 10 inchs would have given me the space i need to do it properly. However i am going to try again today doing the set up exactly as you have just described but but my layup in the vacuum bag instead of sealing to the flange. This should give me enough room to put a breather around the perimiter. I will let you know tomorrow how this comes out.

I do agree that without a breathable perimiter as soon as the resin has passed over the fabric and goes to the edges that vacuum is reduced due to the resin blocking the vacuum from the back to the front. So what i think happens is when the part is infused or nearly infused the vacuum pressure drops from the back of the part towards the front.

I could be wrong but ill give it a go anyway.

Cheers, Chris.

 

[crud]

I have a question for you mike if thats ok? When you have a perfect infusion do you see any bubbles that appear to get trapped in the weave of the cloth? I have found on mine that when i get a really good one i hardley see any bubbles in the back but.... if i get any bubbles that appear in the weave that i can see throught the bag, when i de-mould the part this is where any imperfections seem to be. If i squeegee the bag with my finger nail i can see as if there is trapped air that moves when physically pushed. I have never put a guage on my bagged layup and think this may be a good idea to see whats going on with the pressure.

Regards, Chris.

 

[MotoMike]

Chris,

I have a couple of countersinks in my mould where I put screws to mount the part. I will sometimes get a few bubbles at the top of those, but fortunately I drill those out. I figure it may be bubbles from not degassing the resin and since the countersinks are the high points they end up there. I have always thought that if I see a bubble like you describe I have a leak and can track it to there.

Put your resin trap and gauge as close to the part as possible.

I will give you a little hint on infusing and limiting the air you introduce to the part. Get yourself a funnel or a soda bottle and modify the cap so it fits your tubing. I modify soda bottles by cutting the bottoms off. Mount them in something upside down. Pour your epoxy into them and let the epoxy run down into the part rather than letting vacuum pull it up while trying to keep the tube under the fluid. Don't do this with polyester or vinyl ester resin as it will go right through the plastic and make a mess (from experience). It seems to work well with most epoxies though. I just find this easier to eliminate air when infusing and most of the bubbles in the epoxy will migrate to the top of the soda (the bottom actually) bottle and never make it into the part.

Give it a try and let me know how you make out.

Mike

 

[SandEngXp]

A little different tack.

I suspect that the bubbles you are experiencing are caused during resin exotherm. Temperature increases and flashes volatiles or dissolved air in the resin. starting point will always be an inclusion or fiber tip. It will be worse in areas of thicker laminate.

Reformulate your resin so it has a gentle gel formation prior to exotherm. You should much fewer voids.

Chris

 

[Hojo1122]

It sounds like your draining your part because either your laminate or infusion mesh is connected to your vacuum source. You should have at least 3-6" of space between where your laminate ends and your vacuum source is, the only thing connected the two should be peel ply. You also want to keep full vacuum the entire time, theres no reason to lower your vacuum if you do it right. Depending on your laminate and size, clamp the resin source off either a couple inches short of your laminate or at the end of your laminate depending on the excess resin in your flow medium. Experience will help you determine when. I also find that the red mesh has the best cosmetics, and the green has been RC with a very slight compromise in surface quality but absoultly no pinholes in either. You should be able to get a perfect pinhole free surface out of mold with no surface coats/gel coats required.

 

[Hojo1122]

*better RC* ment to say above.

 

[Hojo1122]

another point to add is you must have a perfect vacuum with absolutly no leaks. You ahould be able to cut your vacuum source off before in infusing for atleast 15-30 minutes and see absolutly no drop in vac. level. One peelply strand can ruin this. Do not attempt to infuse unless you have no drop!

 

[bellx1]

Exactly what Hojo said. One peel ply strand ruined one of my infusions so take the time to check your seal carefully.

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