OOA prepreg

General Composites Discussions Composites Talk
#1

I’m looking to venture out a bit and try this stuff but have a few questions if anyone can help.

  1. Where to buy it. Just looking for a yard to mess around with. I know easy composites sell it but searching maybe for someone in the US.

  2. Can it be used in an oven where I won’t run my pump in? I would debunk the bag and just keep the bag sealed putting it in the oven I have access too.

  3. I’m actually looking to do a tube or mandrel. If I plan to wrap the OOA prepreg around a dissolvable core I would prefer a nice finish on the outside, or as nice as I can get it. I understand there will be post autoclave finishing like light sanding and clear coating but I’m trying to avoid anything huge like fabrics that curled up in bagging material or creased much.

To solve number 3 I’m thinking I could use some perforated release film wrapped overlapping around the entire shaft, then place breathing cloth on the outside of that. But maybe something better then perforated release film is better for a more consistent finish. Is there anything out there that gives a nice finish that you can just drop clear coat on right afterwards and it look good?

#2

For a normal box oven you need to keep the vacuum on while the part cooks, either with the pump running or connected to a vacuum tank/reservoir.

Release film will work ok.

Hand finishing is hand finishing, it can take time and require coats of material to whatever standard you need.

#3

Ah ok. It’s a grieve box with a heat controller. But not pressurized if that’s what you mean…

What will happen if no constant vacuum is applied?

#4

You are very likely to get pinholes if you don’t have an active vacuum connection. Sometimes you will get a part that has a decent enough finish and the pinholes won’t worry you, other times you will need to refinish. It’s the consistency that will drive you crazy.

#5

Does anyone have some recommendations where I can buy some?

#6

Buy some what?

#7

Out of autoclave prepreg

#8

Ah yes, sorry, I forgot your first question.

I dare say that Easy Composites will still be your best bet. You will probably find somewhere in the US that has OOA pre-preg, but whether it is any good is another question. The stuff from Easy Composites just works perfectly, and that is a big thing with OOA. I’ve tried quite a few that claim to be OOA capable, but they all deliver poor results. VTF261 (or EasyPreg) is the only system I have tried that delivers flawless, truly pin-hole free results.

#9

Easy composites don’t actually make anything,they sell other peoples products at a mark up
“easy preg” comes from solway,who bought cytec who in turn took over advanced composites and its advances 261
Solway wont sell small amounts but if you google shd composites they will do small amounts of material and are very helpful and their OOA material is better
All the guys there worked at advanced inc the chemist who is the main man that formulates the resin system
You must apply vac during the whole cure
For a compact clean outer surface spiral wrap with shrink tape
The tighter an neater your wrap the better your Finnish
Make sure you get the pre released so you can remove it post cure, thou I always give mine a extra wipe of release before use

#10

Rockwest carries Mitsubishi/Newport Prepregs, Composite Envisions carries some Tencates and others. I’m working with some NB301 right now OOA and it hasn’t been to bad, depending on the process. Some things we are running cored, others vacuum bag, others pressure inserts or bladders. Not done with the project yet but should have a good idea on process variations in a few weeks.

#11

I’ve used material from APCM (prepregs.com) with some good and bad results. I have gone through 25 yards of DA4090MX from them and have concluded that a properly controlled convection oven, edge breathing, and P3 release film are the key to getting good results. I feel like I’m making headway with it and will be using more.

If you do end up trying some of their material reach out to me so we can exchange notes. I buy through Competition Marketing (http://www.competition-marketing.com/WP/)

#12

If you are making tubes using some sort of mandrel then you can achieve a good finish by wrapping it but recommend using a smooth release film capable of surviving high temperatures like the smooth Teflon coated release films sold by Composite Envisions (and others). If you use perforated films then you will have the perforation pattern on the surface and will need to sand it a little before applying clear coat.

If you aren’t going to use a vacuum then you need make sure the release film is wrapped tight enough to apply pressure evenly around the surface. You can tape it in place. There are special tape-like products sold specifically for this purpose too.

It’s best to avoid any trapped air pockets between the part surface and the smooth release film. I apply the release film with my cold roll laminator sometimes but a squeegee works too. The laminator is just a time saver and not a requirement. With the red high temp release film from CE, you can usually see any trapped air under the film.

#13

KISS method.

If your using foam mandrel or dissolvable mandrel… Just wrap it in your OOA and use high temp heat shrink wrap.
You won’t get a perfect Finnish , but it’s very good , as it makes it very even flat Finnish and bubble free.

It quite readily avalable from electrical supply places up total about 6 or 7 inch dia maybe be bigger.

Also you can get clear heat shrink tape/film from some composite supply places also comes in many different diameters

Cheers tim

#14

Thanks guys.

Yeah I’m going to apply vacuum. I just need to find a small tube that will fit between the grieve door insulation while not keeping the door open.

I also need to find an OOA prepreg still. I wish there were more US manufacturers and ones that provided curing cycle times.

#15

I’ve never used Teflon coated release films. Mainly because I’ve always used peel ply. I did use some Mylar brown stuff before but it left a textured surface instead.

Does the Teflon coated release film work if wrapping around a cylinder in strands? Like if I cut one inch wide strips and wrap it around the shaft overlapping ends? I know if I did that will peel ply the end edges that are cut will leave strands of peel ply on my part and embed itself basically into the first layer of carbon. Without extreme sanding it’s impossible to get out and if I’m using 3k prepreg then it would sand right through he layer.

I’m honestly trying to locate low temperature cure 6k 2x2 OOA prepreg if anyone has a link…

#16

If you want to make a nice tube, use a metal mold and a inflatable bladder. Then you don’t need to use vacuum, you’ll have great compaction. If the mold is polished to mirror, the part should come out the same. You don’t want or need to use release film if you have a nicely polished mold and use semi permanent release. Plus at 150psi, parts come out looking nice.

#17

Not sure why you would want to wrap it in strands. Seems like a lot of extra work for no reason. Why not just wrap it as one piece?

If it is an unusual shape and you are worried it won’t wrap / drape cleanly, then you are better off making a custom silicone vacuum bag to wrap it in. Use sheet wax to replicate the cf thickness when making the silicone bag.

You can get brush-on silicone vacuum bagging rubber from Smooth-on.

Composite Envisions and others sell their prepreg heat cure resin films seperately so you can turn any cf into prepreg if you want. Or… they offer a service to make custom prepreg for you using any fabric you want.

#18

Great post. Will come back and post a few links for sources.