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Old 08-02-2013, 12:03 PM   #11
Cleuck

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OOA pregs often have "air passages" or un-pregged tows of material so air can be evacuated in the early stages of cure. Most of the air evacuation happens in plane inter or intra (Between plys or in the actual ply itself). Very little "through plane" permeability takes place. This is why you need little glass tows or a breathable edge dam linking the laminate to you breather. I would stay away from peelply, as it is just soaking up resin. Temp and temp rates are critical in controlling resin/air flow.
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Old 08-02-2013, 08:24 PM   #12
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I am not sure on what kind of prepreg I'm using. It is from my work. It's not out of date, just not certified by the government anymore so they don't care i use some. We do maintenance parts for military aircraft. Mostly metal, but I'm doing some composite parts for them this summer. The finish they get looks like the picture i have below.

I was going to layup a small flat piece next week and see what happens with no breather or peel ply and all the necessary pathways for the air to escape. Ill let it sit under vacuum for a couple of hours before throwing it in the oven. I'll have the part dwell for an hour or so at 150F before going up and holding it at 300F. Hopefully I'll get some better results.
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Old 08-04-2013, 11:35 AM   #13
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Quote:
Originally Posted by carboncactus View Post
If enough people bunch up, you can buy a roll of Umeco VTF261. It costs 50 a metre, but you have to order a 50 metre roll. Easy-preg is a rebranded VTF261. It is pretty unique, and no other manufacturer has made anything like it. I need about 5-10 metres, the user morepower uses it too, and I know someone else that might want some.

Yep..... If a few wanted to have some VTF I would be glad to have some of the material and if we had to buy a full roll for the lowest price I think it could be worth doing. Nothing really beats VTF261 for out of autoclave use.
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Old 08-05-2013, 07:14 AM   #14
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1: Follow layup from the manufactuer. If they call for pref release, you need it to draw out voids, else they might call for solid release, and some sort of glass tows used to release VOCs and air from the release (meaning, tape is applied around the entire edge-of-part to seal the prepreg inside a bag of release....the only gas escape is tiny glass tows, which only allow gas to escape, but keep resin in. Peelply is optional, and should not affect the performance of the material in any way. It will even out the surface for clear coating, but shouldn't draw out resin so that it creates voids.
2: if it's an autoclave specific prepreg, you might never get the voids out.
3: debulk the first layer, and then every 3 layers. This will help get rid of wrinkles later. You can even do every 2 layers. Remember, you can not compress the first layer down by hand. Every layer after that will only magnify the wrinkles made by compressing the layers down in corners, etc.
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Old 08-05-2013, 07:05 PM   #15
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Hello everyone,
New update today. I was able to do two small sheets for testing new techniques today.

Here are the two plates out of the oven.




The layup was relatively simple. I used a 5.7 ounce 2X2 twill weave for one and I believe a satin fabric with a definitely heavier tow, as the final product was noticeably thicker than the twill one.
The two test pieces were 3"x7", with 5 layers each, They were placed on a waxed 1/8" thick aluminum plate.

I only used non-perf release film on the CF, I also used little strips of peel ply in place of glass tow to hopefully help extract the air from the material. The peel ply strips were connected to breather that was on the perimeter of the plate.

I debulked the 5 layers of prepreg for an hour and a half at room temperature.




I then ramped it up to 150F and had it dwell for 90 minutes. Next, I ramped it up to 300F and held it for 4 hours and then I let the part cool down to 140F.

Here is the whole thing just out of the oven.



Right off the bat i noticed that the vacuum bag and relase film got sucked in between the fibers of both materials. I was alittle dissapointed in that part. I did notice however that where the peel ply strips were, they had a more uniform surface than the rest of the part.



The tool side of the part was more interesting. The satin weave prepreg did not do as well as i expected. It was about the same, if not worse than the little box i made. I believe that prepreg had a higher resin system than the twill weave one. I think that is the reason why it did not do so well, and the fact that it had a thicker, heavier weave to it. This means less compaction of the fibers.



The twill weave prepreg turned out a lot better. I was expecting the material to be worse than the satin weave in terms of surface finish. The twill weave had much shallower voids on the surface, some portions have no surface voids at all which is kinda cool. The finish isn't autoclave class by any means, but I do believe that it would only take a single coat of lacquer to fill in the gaps on this part.



I am not satisfied yet, I want to experiment with different combos of breather, peel ply, and release film. I did not debulk in between layers. I think I'll try to do that next time. Most likely after the second layer.

Let me know what you guys think.
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Old 08-05-2013, 11:56 PM   #16
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Before getting into anything else, is it the same resin system in each pre-preg?
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Old 08-06-2013, 12:15 AM   #17
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They were two different resin systems. I know I probably shouldn't do that, but I wanted to compare the two pieces side by side. They have the same curing schedule too.
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Old 08-06-2013, 03:27 PM   #18
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Even with OOA carbon I debulk overnight.... One hour is not a lot of time..

This is made directly off the alloy heel plate and I used a semi perm release. It was bagged with a perf release and debulked overnight. This is 6 layers and it is not a specific OOA Pre-preg. It is a low temp pre-preg RP400 from PRF and works OK but RF464 is more consistently better.


Last edited by morepower; 08-06-2013 at 03:39 PM.
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Old 08-06-2013, 07:11 PM   #19
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Okay, ill try debulking longer. did you delbulk the first two plies at all? Or did you only do it after the whole layup?

My next test will incorporate a bunch of different combos of breather/ release layups. See what happens there.
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Old 08-07-2013, 12:57 AM   #20
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I laid it all down as I just wanted to try it as a test..... But I did leave it overnight.
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