Working with Carbon Fiber (and other composites) - Tilted Forum Project Discussion Community

xepherys · 07-03-2007, 01:59 PM

Does anyone have experience working composites at a home workshop? After reading this article in MAKE magazine, I think I might want to play around with modifying some of my gadgetry around the house to experiment with composites. I'm looking for people with experience outside the HOW-TO in the article.

telekinetic · 07-03-2007, 02:44 PM

I know a fair bit about it, what would you like to know? I haven't made anything more complex than some multiply wet-layup panels, some pre-preg panels, and a subwoofer compartment, all for a composites class I was taking, but I might be able to point you in the right direction.

xepherys · 07-04-2007, 09:17 AM

Well, I plan mostly to learn by replacing plastic shells for things like game controllers and systems or making a computer case. I'd like to make molds from the original items. What material works best for molds for composites? I usually make molds out of plaster or clay, but I'm not sure if either is well suited for composites.

Also, once the mold is made and the lay-up is done, how much can you work with the surface? I understand that you want to use a fine sandpaper on it then use a spray clearcoat to make it look professional. If additional mild shaping is needed, can you use heavier sandpaper? I know thinning it makes it weaker, but I don't need these to be terribly tough, just nice looking mostly (and a little stronger than plastic).

Thanks!

texascwby7 · 07-06-2007, 09:01 PM

I work at an airplane component composite manufacturing plant. All of our stuff is the prepreg and we bake it in an autoclave to activate the resin. Do not do this in your home stove. THe gases from the resin can impregnate the walls of the interior of your oven and your food will be tainted.
Our molds are either composite molds or aluminum molds (hard, smooth surfaces, not like clay). for controllers and other shells, you would probably need female molds ( so clay mold to plaster to another plaster). The side that is on the mold surface is the smoothest. You'll need some sort of release agent on the molds. I'm not sure if you can get the good chemicals, but since your small timing it and possibly without baking it you can use a mix of dawn soap and water or a grease. get a dixie cup and fill it about 1/8th or 1/4th of the way with dawn and then the rest with water and stir. Apply that to the smooth mold surface. You want it to be very thin....it's like greasing aa pie pan. The prepreg can cure without baking but it takes a day or more depending on the resin matrix. wet layup is easier and usually sets faster. When your're laying up the plys, if the outside surface ply is glass and the next is carbon, then you'll get a glossy look. A clear expoy resin (for example look up http://www.toolchemical.com/products...scriptions.htm ) applied to that surface can smooth out imperfections and keep that glossy look. You can thin it with acetone to make it flow better... any of the resins you choose.
The carbon material drills fine. It can be hard on blades. Sanding, will take a coarse grid to get anywhere. 80 or coarser. You don't want to sand the surface that you'll be looking at....i.e. the controller surface. You'll mess up the weaves and it'll look terrible. Use the molds to controll the surface shape and smoothness. Use multiple plies to create thickness and sand off the backside if you have to sand a surface. one ply of prepreg laid up and cured is about 0.010" thick. Wet lay up (dry plies laid down and wetted with resin) are the same thickness. trimming and sanding the edges are fine to get it to shape.
that's all for now

xepherys · 07-06-2007, 10:36 PM

Pretty much all of that made perfect sense compared to what I'd been reading. The only thing that I'm curious about is the sanding the outside (visible) surface. An article I read suggested to sand it with 2000 grain to more or less buff it, then use a clear coat spray to make sure it keeps it's glossy finish. That's a no go?

When you say use a glass surface ply, do you have a link to any such material? The only things I've found is fiberglass which has a white, beaded appearance and would certainly not make a good outer layer for the carbon.

Back to te outside smoothness. Since I won't be using pre-preg, how can I assure that I infuse the epoxy smoothly enough that it presses into the mold and does not leave pits or uneven spots on the exterior surface?

Thanks!

gruber616 · 01-03-2008, 07:46 PM

hey there... Since this topic is going on, I thought I'd throw out a question. What would the best weave be for strength and smoothness for a semi-spherical shape about the size of a grapefruit? Thanks much.

07-03-2007, 01:59 PM	#1 (permalink)
xepherys <3 TFP Location: 17TLH2445607250	Working with Carbon Fiber (and other composites) Does anyone have experience working composites at a home workshop? After reading this article in MAKE magazine, I think I might want to play around with modifying some of my gadgetry around the house to experiment with composites. I'm looking for people with experience outside the HOW-TO in the article. __________________ The prospect of achieving a peace agreement with the extremist group of MILF is almost impossible... -- Emmanuel Pinol, Governor of Cotobato My Homepage

07-03-2007, 02:44 PM	#2 (permalink)
telekinetic zomgomgomgomgomgomg Location: Fauxenix, Azerona	I know a fair bit about it, what would you like to know? I haven't made anything more complex than some multiply wet-layup panels, some pre-preg panels, and a subwoofer compartment, all for a composites class I was taking, but I might be able to point you in the right direction. __________________ twisted no more

07-04-2007, 09:17 AM	#3 (permalink)
xepherys <3 TFP Location: 17TLH2445607250	Well, I plan mostly to learn by replacing plastic shells for things like game controllers and systems or making a computer case. I'd like to make molds from the original items. What material works best for molds for composites? I usually make molds out of plaster or clay, but I'm not sure if either is well suited for composites. Also, once the mold is made and the lay-up is done, how much can you work with the surface? I understand that you want to use a fine sandpaper on it then use a spray clearcoat to make it look professional. If additional mild shaping is needed, can you use heavier sandpaper? I know thinning it makes it weaker, but I don't need these to be terribly tough, just nice looking mostly (and a little stronger than plastic). Thanks! __________________ The prospect of achieving a peace agreement with the extremist group of MILF is almost impossible... -- Emmanuel Pinol, Governor of Cotobato My Homepage

07-06-2007, 10:36 PM	#5 (permalink)
xepherys <3 TFP Location: 17TLH2445607250	Pretty much all of that made perfect sense compared to what I'd been reading. The only thing that I'm curious about is the sanding the outside (visible) surface. An article I read suggested to sand it with 2000 grain to more or less buff it, then use a clear coat spray to make sure it keeps it's glossy finish. That's a no go? When you say use a glass surface ply, do you have a link to any such material? The only things I've found is fiberglass which has a white, beaded appearance and would certainly not make a good outer layer for the carbon. Back to te outside smoothness. Since I won't be using pre-preg, how can I assure that I infuse the epoxy smoothly enough that it presses into the mold and does not leave pits or uneven spots on the exterior surface? Thanks! __________________ The prospect of achieving a peace agreement with the extremist group of MILF is almost impossible... -- Emmanuel Pinol, Governor of Cotobato My Homepage

07-06-2007, 09:01 PM	#4 (permalink)
texascwby7 Upright	I work at an airplane component composite manufacturing plant. All of our stuff is the prepreg and we bake it in an autoclave to activate the resin. Do not do this in your home stove. THe gases from the resin can impregnate the walls of the interior of your oven and your food will be tainted. Our molds are either composite molds or aluminum molds (hard, smooth surfaces, not like clay). for controllers and other shells, you would probably need female molds ( so clay mold to plaster to another plaster). The side that is on the mold surface is the smoothest. You'll need some sort of release agent on the molds. I'm not sure if you can get the good chemicals, but since your small timing it and possibly without baking it you can use a mix of dawn soap and water or a grease. get a dixie cup and fill it about 1/8th or 1/4th of the way with dawn and then the rest with water and stir. Apply that to the smooth mold surface. You want it to be very thin....it's like greasing aa pie pan. The prepreg can cure without baking but it takes a day or more depending on the resin matrix. wet layup is easier and usually sets faster. When your're laying up the plys, if the outside surface ply is glass and the next is carbon, then you'll get a glossy look. A clear expoy resin (for example look up http://www.toolchemical.com/products...scriptions.htm ) applied to that surface can smooth out imperfections and keep that glossy look. You can thin it with acetone to make it flow better... any of the resins you choose. The carbon material drills fine. It can be hard on blades. Sanding, will take a coarse grid to get anywhere. 80 or coarser. You don't want to sand the surface that you'll be looking at....i.e. the controller surface. You'll mess up the weaves and it'll look terrible. Use the molds to controll the surface shape and smoothness. Use multiple plies to create thickness and sand off the backside if you have to sand a surface. one ply of prepreg laid up and cured is about 0.010" thick. Wet lay up (dry plies laid down and wetted with resin) are the same thickness. trimming and sanding the edges are fine to get it to shape. that's all for now

01-03-2008, 07:46 PM	#6 (permalink)
gruber616 Upright	hey there... Since this topic is going on, I thought I'd throw out a question. What would the best weave be for strength and smoothness for a semi-spherical shape about the size of a grapefruit? Thanks much.