Making a hallow carbon fiber item from a mold

Sevs753

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So next year, i'm going to be undertaking a project making something out of carbon fiber. It's going to be thick enough that making it solid is not going to be easy or cheap. Is there a way that i can make the entire piece at once but have it hallow? or would it be easier to make the top half and the bottom half separately and patch it together after the fact?
 
Is it possible to use another substance (Styrofoam, wood. plastic, etc.) and form that to the shape and then wrap it to make the part(s)? I have seen videos of different parts being made over a mold with the help of a vacuum before the part is cooked. Not all that different than how a fiberglass mold is used.
 
It's possible but i wouldn't want to leave the base inside. What I'm making is a modified copy of an existing item so what im planning on doing is making a fiberglass mold of parts of the item(the parts that will differ from the original), making a copy of the parts, modifying it as desired and then using that to make a new mold of the entire item. From there, i want to make the final product from carbon fiber. That last step is where im looking for advice.
 
The finish on the inside doesnt matter. It will be sealed off. The outside needs to be smooth. I just want it to be hollow so i dont have the added weight (and expense) of making the part solid carbon fiber.
 
What is the general shape of the object? There are different ways to "lay up" CF...are you using pre-woven sheets, or creating the piece as it's woven like a drive shaft?

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You could fill your interior with honeycomb for added strength, or use wax that can be melted out through a hole or two.
 
I just realized ive been using the wrong word. It shouldmbe 'hollow', rather that 'hallow'.

What is the general shape of the object? There are different ways to "lay up" CF...are you using pre-woven sheets, or creating the piece as it's woven like a drive shaft?

I'm going to use pre-woven sheets. The object is a spoiler for a car. We were just going to make it out of fiberglass but we thought we would go for carbon fiber instead. Most definitely overkill but it will be cool in the end.

Can't you make two halves, bind them together and cure them as one piece?

Whatdo you mean by that? I was thinking about making two halves, then using thin strips of pre-woven carbon fiber attach the two halves. it would be pretty much the same process as making the halves (carbon fiber + resin) but just applied directly to the halves instead of using a mold. Sorry if that sounds like im stating the obvious. I've very new to working with composites.

You could fill your interior with honeycomb for added strength, or use wax that can be melted out through a hole or two.

What would i use for honeycomb? I also thought about wax but i dont know if it would be strong enough to keep its shape while i lay out the carbon fiber. Do they make special wax for this kind of thing?
 
I'd recommend testing any approach before going full-scale.

Good old paraffin should do, alternatively polystyrol that gets "washed" out with a solvent (nasty business!)... just make sure your resin doesn't also dissolve it after covering it in parting agent.
Anything will work as honeycomb, from cardboard to kevlar.


How large are we talking about, and what general shape?
 
Depending on how complex the shape is, I would use wood to make the final mold and make it in two pieces,(top and bottom). YOu may need to make it in more if it is really complex. You may still need to apply a vacuum(wrap it in a bag and smooth it to shape) to get it to hold shape while it cures.
 
its going to be based on this spoiler. the supports will be custom and the tips wont be so long and pointy. (large image so thumbnailed. click for full size)

 
I've had quite a bit of CF experience in college. I can help you out when time comes to actually carve the plug or make the layups.
 
I've had quite a bit of CF experience in college. I can help you out when time comes to actually carve the plug or make the layups.

Awesome! Thanks! I'll PM you in the spring when I start actually making the mold and such. Lack of a garage and winter make it difficult to work with fiberglass
 
Awesome! Thanks! I'll PM you in the spring when I start actually making the mold and such. Lack of a garage and winter make it difficult to work with fiberglass

Are you going to be using foam to make a plug first?
 
i have the actual spoiler it will be based from. i was going to make a fiberglass copy that i will modify to what i want and i was planning on then making a full mold from that. the full mold would then be used to create the carbon fiber version
 
I've had quite a bit of CF experience in college. I can help you out when time comes to actually carve the plug or make the layups.

I was going to offer up my FSAE experience, but it looks like the Russian has you covered off on that front.
 
I was going to offer up my FSAE experience, but it looks like the Russian has you covered off on that front.

I definitely appreciate the offer! When spring comes and I start actual work on this, i'll be sure to post about questions and such I have. CrzRsn is local to me so he can help in person if he is willing but I welcome all input on exact materials and procedures to use.

After photoshopping the spoiler onto my car,as is and with the modifications i planned, i'm going to leave the shape as it is and just move the supports inward and make them shorter. That should make the process a little easier.
 
I definitely appreciate the offer! When spring comes and I start actual work on this, i'll be sure to post about questions and such I have. CrzRsn is local to me so he can help in person if he is willing but I welcome all input on exact materials and procedures to use.

After photoshopping the spoiler onto my car,as is and with the modifications i planned, i'm going to leave the shape as it is and just move the supports inward and make them shorter. That should make the process a little easier.

I'm happy to offer advice. PM me your current plan and I'll add whatever value I can.
 
I'm happy to offer advice. PM me your current plan and I'll add whatever value I can.

Thanks. I'm going to be getting some measurements today that will help determine if i need to lengthen/shorten the base spoiler to fit the car so once i get that, i'll PM you my plan. I'll also be going into a little more detail when i update my pyc thread tofay/tomorrow.
 
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