What am I doing wrong?

I made a mould at last that does the job but I am having problems with bubbles and voids! I am doing it with resin infusion and epoxy resin. At first I thought is was a leak but the second one I did I left for 24hours and it didn’t drop any HG at all. Should the voids not fill with resin? Here are some pics to help.

The Mould

The part

">carbon parts :: IMGP1673.jpg picture by drtcmm - Photobucket

">carbon parts :: IMGP1675.jpg picture by drtcmm - Photobucket

The problem is your geometry. Your’re going to have a hard time getting the resin to flow into those small spaces. If you really want raised letter fill in those parts with gelcoat first and then lay down your fabric and infuse.

canyon would that be classed as bridgeing

also ur flages look small

Yes it is! Forgot to mention that but there you have it. The jargon for your problem and the cause.

Thanks Brainstorm!

Just learning because i had simlar problems. Biger pleats on my next part.

will the finished part look good if I ues gel coat first? Can it be sprayed?

do you degass your resin?

ok look what you have to do. First you make the vacuum and when the air is completely out then with you hand or with small tool (I am using one small piece of soft wood) press all the corners, holes, areas with strange curves etc. With this way you fill up all the areas that bagging didn’t cover. Careful, press it slowly and not all in one place because there is a case to make hole in the bagging. I am doing the same thing especially in areas like yours.

Do it and you will see. :wink:

There was a similar thread on another forum.

Causes are plenty, solutions are plenty as well. Probably a combination of solutions will get you rid of the bubbles.

The bubbles can develop because of low capilary action in that area (that is always where the bubbles form)

-indeed work the fabric so it enters the lettering more. Apply a very, very light vacuum, then work the fabric with a HDPE stick. Apply some more vacuum, and see if there is anything that needs correcting.

-use a different mold release. This can cause bubbling as well.

-turn the mould in a different position during infusion

-next one is tricky: infuse with the following stack:

fabric
perf film
inf medium
Dahltexx SP2 (resin barrier)
inf medium or breather

Infuse with a lower pressure than normal (say 80% vacuum)
After infusion, apply a vacuum on the breather, as high as possible. This will enlarge the bubbles, drawing them through the membrane. I made some parts that way, they came out perfect. Lots of layup though.

Yep… degass your infusion resin in a vacuum chamber, for say 5 minutes at full vacuum. I usually use a 30-45 minute pot life epoxy for infusions. I place my mixed resin cup in a tub of hot water for a couple minutes, allowing all the trapped air to rise and exit the resin.

Also clamp off your resin inlet line close to the resin mix. This will minimize how much air gets inside the laminate.

Those letters may never completely come out perfect… raised letters and logos are a p.i.t.a. You can leave the infusion medium netting OFF those letters because the medium will cause bridging there. The resin will flow a 3-4 inches on it’s own without it.

You can use two vacuum pumps… one for main suction to infuse with like normal. Keep the second pump handy to hook up the resin inlet line after you have fully infused the part. Drawing vacuum from both ends should help eliminate some trapped air. Just remember to clamp off your resin line before hooking up the second vacuum pump, and be sure to use a resin trap before the pump. Excess resin will clog your vac pump otherwise.

I think what Herman is saying is to double vacuum bag the part. The first bag set up is normal set up for infusion. The second bag has breather and uses a second vacuum pump. Breather will cause further compression of the laminate. I have heard of technicians double bagging a lay up.

No, you missed what I said, but I cannot blame you, the process is a bit more difficult to explain.

Dahltexx is a coated peelply, which lets air though, but not resin. If you infuse at moderate vacuum, you keep a bot of air in the pockets (instead of vacuum). After infusion, crank up the vacuum, and the air will expand, creating a path to escape through the membrane. The resin cannot pass, and will stay in the part.

Most gelcoats can be sprayed, check the datasheets. I just entered some nice vinylester and iso-npg gelcoats into my catalogue, which are just for carbon infusion. However, then you will need to infuse with poly or VE.

there are also epoxy gelcoats, I have them from Sicomin.

I heart membrane!!! Make sure said membrane is compatible with your resin. Our goretex material doesn’t work with VER, it’ll bleed right through the layer. Another kind (it’s blue, and maybe from Airtech?) works fine.

not sure of your process Herman, but we just infuse normally, and even let the resin line open the entire time. As long as you have no leaks, in the air, all air is sucked out, resin is replacing the voids. No need to clamp, since once the voids are filled, resin has no place to go. The hard part about membrane infusion, is that you can not see the resin flow!! No idea if there is race tracking, which isn’t normally a problem since the air will just be sucked UP through the stack, not across the laminate plane. (unless you have a caul plate…)

there’s ways of putting little windows in to the membrane aswell rather than doing it totally blind. For those who do not know, using these membranes requires paperwork to be side for EADS before using.

What are the advantages of membrane infusion vs regular permeable peel ply infusion?

its a dual chamber setup. so the membrane seperates the two chambers. it allows air to permate through the membrane but resin can not(unless viscosity is dropped drastically). The advantage is the ability to pull air from the entire part, rather than just at the end. end result is lower aircontent, and possibly higher fiber volume if done correctly.

So with membrane infusion you need two pumps? One for the partial pressure infusion and one for the final removal of the air?

vacuum is applied to chamber 2 only in this perticular setup

About EADS: Only if you tape the membrane to the flange. Ask your Airtech rep.

Indeed this setup is more cumbersome, but sometimes there just does not seem to be another solution. It is not my favourite setup as a user (as a supplier I like it, lots of stuff to throw away.)

The Dahltexx stuff is blue indeed.

Thank you for all the replies but I think I may have to try making some other parts first because I dont have the money for lots of waste at the minute. Maybe I will try it again in a few months.