CF forming question

[Trenman]

I am trying to create a raised, free standing carbon piece to attach electronics to. I do not NEED to do this, but I am taking on this challenge and probably over engineering for the greater goal of learning to form CF into free one off pieces. There is a wealth of knowledge that I am hoping to tap into because admittedly, I dont know enough yet to do this correctly. That is, I dont yet have the experience with working with CF to know how to do this:

Goal: I would like to make a carbon fiber component tray WITHOUT attaching the CF to any part of the rocket (like how you would in a tip-to-tip lamination). IE. I would like a free standing CF piece that isnt attached to any other piece.

The way I am thinking MAY work (please please chime in if you know a better way):
1) Make a G-10 jig to lay the cf cloth over
2) Lay peel-ply, pulling it tightly around the form and taping down in the back of the disposable jig/mold
3) Lay a layer of epoxy and apply 2-3 sheets of 5.9oz cf cloth over the jig/mold
4) Add a layer of peel ply over the top, like a peel ply sandwich
5) Remove air in a vacuum bagger
6) Let cure and remove peel ply from BOTH sides, leaving a free standing CF piece which can be trimmed up and coated with a finishing light layer of epoxy for appearance.

Am I on to something or am I going about this completely improperly?

 

[troj]

So, basically you want to make a flat "board" of carbon fiber?

If so, you're making it harder than it needs to be.

The easiest way is a couple pieces of heavy glass. Wax both -- simple paste wax will work, whether auto body or floor wax. Apply the wax, leave it as a haze.

Lay down some CF, brush epoxy on it, apply more CF, add more epoxy as necessary, and keep applying layers of CF until you're at about the thickness you want. Don't go nuts on the epoxy or it'll run out all over and cause you grief.

Once you've got the layers you want, lay another piece of glass on top, apply weight, and let it cure. When you're done, use a plastic wedge to help pop the glass pieces apart -- this is why you need heave glass. It will stick a little bit, but with the wax, it pops off pretty easily.

Then, pop the piece off, trim as necessary, and you're done.

I use this method to apply CF and fiberglass to fins and bulkheads.

-Kevin

 

[dixontj93060]

For some reason I interpreted the question differently (and maybe Trenman should clarify), but when he said "free standing" and mentioned tip-to-tip, I was thinking he was talking about a curved surface. In that case you can do it right and make a mold and there are many examples of doing that on this and other forums most specifically in the construction of nosecones. OR, you can do it the cheap and dirty way. I used this method when rebuilding fairings for my son's motorcycle. If you look at the attached picture below you can see it has a lot of complex curves especially toward the front where the air intakes are. In this case I simply used aluminum mesh which you can pick up at any Lowes or Home Depot for a few dollars (the kind with an ~1/4" diamond pattern spacing--see attached). It is easy to bend to nearly any shape. Then I tacked some peel ply in a few spots over the aluminum mesh with CA glue and then applied multiple CF layers (in my case I clamped it to the fairings to get a continuous curve, but if you just need a free standing shape, then layer on the CF with it extending past the mold. Again as Kevin said, don't overdo the epoxy, use just barely enough to wet out the CF. After it dries, just pop off the aluminum/peel ply mold and trim to size.

 

[Trenman]

Although not curved, my application will have various bends, or planes, so the diamond mesh idea sounds like a good one so far

 

[troj]

Although not curved, my application will have various bends, or planes, so the diamond mesh idea sounds like a good one so far

If you plan to make a one-off, then the diamond mesh makes sense.

If you plan to make more than a couple of these, then it might make sense to investigate making a mold.

-Kevin

 

[Trenman]

Instead of wax could you use wax paper or parchment paper?

 

[troj]

Instead of wax could you use wax paper or parchment paper?

Parchment paper is porous and would end up bonded to the part, along with whatever is underneath it. Waxed paper may well end up the same way.

I've tried basket wrap (it's a shrink film) and have learned the hard way that it, too, must be waxed, or it sticks.

Other than materials, such as peel ply, specifically sold for this purpose, paste wax is the most effective material I've found.

-Kevin

 

[rocketsmith]

Parchment paper is porous and would end up bonded to the part, along with whatever is underneath it. Waxed paper may well end up the same way.

I've tried basket wrap (it's a shrink film) and have learned the hard way that it, too, must be waxed, or it sticks.

Other than materials, such as peel ply, specifically sold for this purpose, paste wax is the most effective material I've found.

-Kevin

I use parchment paper exclusively for keeping epoxy from sticking to things. I have never had it stick to epoxy. I use it to lay up sheets for electronics sleds and fins and put 200 pounds of weight on the granite sheets I use to make sure it is flat. I use granite countertop slabs to lay up stuff, as glass, even 1/4" thick, is flexable and may give you a curved sheet. Granite doesn't move and you can get scraps and samples from a local tile and countertop supplier.

 

[troj]

I use parchment paper exclusively for keeping epoxy from sticking to things. I have never had it stick to epoxy. I use it to lay up sheets for electronics sleds and fins and put 200 pounds of weight on the granite sheets I use to make sure it is flat. I use granite countertop slabs to lay up stuff, as glass, even 1/4" thick, is flexable and may give you a curved sheet. Granite doesn't move and you can get scraps and samples from a local tile and countertop supplier.

Interesting. I've got some parchment paper; I'll have to give it a try sometime.

The grant slabs are perfect -- a friend just had granite counters installed, and he kept the sink cutouts for exactly that purpose.

-Kevin

 

[dixontj93060]

I may be stating the obvious here, but confusion may be in the term parchment paper. I have a printer as a client that uses this term all the time when speaking about a certain weight and finish of paper he uses. Obviously this is not the stuff. Parchment paper for cooking is used frequently in commercial kitchens and is considered an upgrade from wax paper (see What's the Difference Between Parchment Paper and Waxed Paper?)

Interesting. I've got some parchment paper; I'll have to give it a try sometime.

The grant slabs are perfect -- a friend just had granite counters installed, and he kept the sink cutouts for exactly that purpose.

-Kevin

 

[troj]

I may be stating the obvious here, but confusion may be in the term parchment paper. I have a printer as a client that uses this term all the time when speaking about a certain weight and finish of paper he uses. Obviously this is not the stuff. Parchment paper for cooking is used frequently in commercial kitchens and is considered an upgrade from wax paper (see What's the Difference Between Parchment Paper and Waxed Paper?)

Very interesting; thanks for the link!

I did indeed mean the cooking parchment paper, and I didn't realize it's coated in silicone. That does indeed explain the non-stick, as well as explaining why a previous poster said it doesn't stick to epoxy.

I don't think I currently have any parchment paper at home, but I'll have to get some and give it a shot.

-Kevin

 

[JimJarvis50]

Ditto on the parchment paper. Nothing sticks to it.

I used a couple of natural stone tiles from Lowes on my last fin lamination. They worked pretty well as a nice flat surface.

Jim

 

[Trenman]

Ditto on the parchment paper. Nothing sticks to it.

I used a couple of natural stone tiles from Lowes on my last fin lamination. They worked pretty well as a nice flat surface.

Jim

Great, so I just bought some from amazon. I am going to try to make 2 molds, attach parchment to the top on the lower mold and the underside of the top mold, then peel ply, then 3 layers (or so), then a top layer of peel ply. Then I will the take the top mold (with the parchment paper underneath), lay it on top and clamp with high pressure on each plane.....

I would think this carbon/peel ply/parchment paper sandwich should result in a good product!!

 

[rocketace]

Just a heads up. I have had problems with a CF altimeter sled. CF is electrically conductive, so it creates a short in my MAWD and my Parrot V2. There are several fixes for it, but you can use nylon screws, or nylon washer just so that the mounting bolt doesn't touch the CF.

 

[JimJarvis50]

Great, so I just bought some from amazon. I am going to try to make 2 molds, attach parchment to the top on the lower mold and the underside of the top mold, then peel ply, then 3 layers (or so), then a top layer of peel ply. Then I will the take the top mold (with the parchment paper underneath), lay it on top and clamp with high pressure on each plane.....

I would think this carbon/peel ply/parchment paper sandwich should result in a good product!!

The peel ply finish will be textured - like the cloth itself. I don't know if you want that finish (which I kind of like) or if you might want a smooth finish instead. With parchment paper only, or perhaps waxed (unwaxed?) mylar, you would get a smooth glossy finish. I would normally use peel ply if I was going to glue something to the finish (i.e. if I wanted a good secondary bond).

Jim

 

[Trenman]

Would omitting the peel-ply and just using parchment paper for a glossy finish leave a consistant finish on the CF? I feel like with added pressure, the epoxy would be forced out either way. Or is the difference just enough to leave a glossy finish?

 

[Trenman]

Actually, I could keep the peel ply and just wipe a light layer of epoxy over the finished product and buff it with finesse it. That way I could keep the perfect 50/50 ratio and not worry about making an uneven product... precision is important to me.

 

[JimJarvis50]

Would omitting the peel-ply and just using parchment paper for a glossy finish leave a consistant finish on the CF? I feel like with added pressure, the epoxy would be forced out either way. Or is the difference just enough to leave a glossy finish?

I'm not sure about the surface that the paper would leave. It might be OK, but I'm just not sure. I'm very sure that using mylar and plates for compression would leave a glossy surface. What I don't recall is whether the mylar should be waxed or not. I believe that it should not be (I think that it will peel off the epoxy even if it is not waxed, and that this is the basis of the surface technique that Mick uses when he makes tubes). This might deserve another question.

If you use peel ply, it will take (based on my experience) about two thin coats of epoxy to fill the peel ply weave. They, the surface would need to be sanded and polished. If you want a glossy smooth surface, then just use the mylar. If you use compression, you won't have extra epoxy.

Note that the purpose of the peel ply for making tubes (as I do it) is different than what you're doing here. The only reason to use peel ply for your current task is if you wanted a good surface for secondary bonding.

Jim

 

[powderburner]

Just in case you have trouble forming the CF fabric into the shape you want without having some corners get wrinkled, don't forget you can also use chopped fiber mixed in with the epoxy. I would suggest trying lengths of 1/4 to 1/2 inch for the fiber, but you would probably need to up the resin content by a small percentage.

You can form a slurry into a lot more shapes than you can using the fabric, and it will still give you about half the strength (which was probably 10X over-designed in the first place?)

 

[troj]

Instead of chopped fiber, if you want to be able to shape it, use just a little bit of fumed silica.

When trying to shape fibers, they have this nasty habit of sticking up as the epoxy cures, leading to little pointy bits that are....unpleasant. Been there, done that, they take a while to heal, especially if it's CF fiber!

Fumed silica is great for thickening it just a little bit, or a whole lot, but leaving it more easily shaped, and even when it doesn't get completely smooth, it's just a little bumpy, as opposed to pointy.

Found out from a local guy at a boat shop that it's not uncommon in boat repair to use just a little bit of fumed silica when doing layups, to help keep the epoxy from running.

-Kevin