Problems with air bubbles


Author
Message
kropucnik
kropucnik
Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)Junior Member (13 reputation)
Group: Forum Members
Posts: 1, Visits: 6
Hi, 

Newbie here. I am trying with making a part and i can't get rid of the bubbles. 



I usually get a lot of small voids and few huge bubbles. I prepare the mould with 5 coats of buffed wax (Axel PasteWiz) and a layer of PVA for a sure release. I heat the mould with a hot air gun and also heat the mixed resin and hardner. Then i apply 6 layers of carbon fibers, heating in between every layer. 

Any idea what I am doing wrong?
Warren (Staff)
Warren (Staff)
Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)Supreme Being (22K reputation)
Group: Administrators
Posts: 2.5K, Visits: 8.5K
A lot of those voids are due to the fabric lifting off the tight recess and corners. You can see the resin has become hazy where it is much thicker. In such cases where the fabric bridges a corner, any air entrapped tends to migrate there and can look much worse.

Ensuring the fabric stays in place is key, as is bristle rolling the wetted fabric to get out as much air as possible.  The less air, the less voids.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant
Fasta
Fasta
Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)
Group: Forum Members
Posts: 468, Visits: 3.5K



A few options.

You could use a lighter softer carbon like 90g.

You could change to a vacuum process.

Or if you can get a coat of your resin onto the surface of the mould first and then wait for this to tack gel like. Then press your dry fabric to the resin and continue to layup with a new resin brew.

Or add a small amount thixotropic additive like Cabosil to your layup resin. Just a little to make the resin slightly thicker and do your layup as normal and that will help hold the fabric to the shapes easier although the Cabosil may slightly cloud the resin. Maybe??




Edited 10 Years Ago by Fasta
Hanaldo
Hanaldo
Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)Supreme Being (21K reputation)
Group: Forum Members
Posts: 2.5K, Visits: 28K
Yeh silica definitely clouds the resin, not good for cosmetic parts. 

I always got the best results applying the first layer of resin and allowing it to tack. Pop the air bubbles with a heat gun. I was never fantastic at wet laying though... Vacuum all the way! 
TCS
TCS
Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)Supreme Being (109 reputation)
Group: Forum Members
Posts: 13, Visits: 52
Evening,

Looking at the images I would say you are using a too heavy fabric to follow the tool in a wet lay application. You will see improvement simply by reducing fabric weight. For a far superior product I'd recommend changing your process to infusion.

As a hand lay process I'd suggest you also try intermediate cures between plies. i.e. allow the first 1 or 2 plies to cure before backing up with additional plies
Edited 10 Years Ago by TCS
Dravis
Dravis
Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)Supreme Being (5.1K reputation)
Group: Forum Members
Posts: 592, Visits: 1.9K
I agree with the other posters ..   Small parts with tight corners do not mix well with medium weight cloth/fabric and wet -lay ..

As soon as you have vacuum or infusion, and prepare your "stack" well, most of the bridging and trapped air will not be a problem.

To wet lay small parts with small radius corners, you really do need to use light weight CF cloth -  Also Plain weave is harder to get to follow complex shapes and compound curves than Twill weave.

"Sapere Aude"... Dare to KNOW!

The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...

103% of all people do not understand statistics...

Do not adjust our mind, theres a fault in reality :-)
GordonFreeman
GordonFreeman
Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)
Group: Forum Members
Posts: 2, Visits: 57
Hi, new to the forum.

I've been trying to make my own carbon plates between two sheets of acrylic. I'm having good luck but I'm getting small bubbles/voids on the surface. The voids almost always follow the pattern of the carbon.

The best results I've gotten is this:

1. Prep acrylic with carnuba wax, then a few coats of PVA.
2. Mix epoxy up, I have not been degassing it.
3. Brush on a first thick layer on the acrylic.
4. Put first layer of carbon down, carefully brush on the next layer of epoxy, repeat.
5. Pour a bit of excess epoxy in the middle
6. Carefully place the other acrylic sheet on top, bending slightly to make first contact in the middle on top of the excess epoxy.
7. Slowly push down in the middle to squish the excess epoxy out from the middle to the outsides.
8. Place a board and weight on top and let cure.

Sometimes there are small bubbles/voids on both sides of the finished plate, less on the bottom side.

I've tried glass plates but have not successfully removed them without breaking them.

I'll see if I can get a good picture of the problem.

Thanks
Fasta
Fasta
Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)
Group: Forum Members
Posts: 468, Visits: 3.5K
In your process you have not mentioned using any roller to push the air out and flatten the weave.




GordonFreeman
GordonFreeman
Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)Forum Member (26 reputation)
Group: Forum Members
Posts: 2, Visits: 57
Should I roll it right after putting down an other layer?

Thanks
Fasta
Fasta
Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)Supreme Being (4K reputation)
Group: Forum Members
Posts: 468, Visits: 3.5K
You can roll every layer, wet it out and roll lightly over the fabric with a metal bolt type roller (or other). This flattens the weave a bit and squeezes air out of the material and gaps.

Then add another layer.


GO

Merge Selected

Merge into selected topic...



Merge into merge target...



Merge into a specific topic ID...




Similar Topics

Reading This Topic

Explore
Messages
Mentions
Search