Selecting The Right CF, Resin, Etc

General Composites Discussions Composites Talk
#1

What guidelines, if any, are out there for the correct combinations of carbon fiber cloth, resins, etc for the automotive industries?

I’m seriously contemplating creating a carbon fiber wide-body kit for myself and a few fellow racers that aren’t happy with the strength & design of the available options.

If I were to design the body panels with a mixture between the steel/aluminum body panels and plastic widebody “add-ons” in a continuous form, could I make a female mold of it? What material would be best to use for the female mold that would allow me to finish the inside of the mold to reduce the finishing work? Durability for multiple molds?

Sorry for the noob questions, but that’s what I am. :slight_smile:

#2

It all depends on what you are looking to achieve.

aesthetic vs. performance

It all boils down to the fact that you get what you pay for.

So to start, if you are looking to re-produce a lot of parts per mold then I would recommend going with epoxy tooling resin and gelcoat to make your molds. If you only need to make a few pieces per mold and want to minimize the cost, then go with polyester tooling resin and gelcoat to create your mold(s).

Similar deal with making the parts. If you want a high compression strength while being as light as possible, go with epoxy laminating resin. Polyester laminating resin is the cheaper alternative although it’s far inferior to epoxy.

As far as reinforcement materials. You can use all carbon graphite for the best strength to weight ratio, or you can use fiberglass for the lowest cost possible. You can intergrate both if you want something in the middle. The addition of kevlar will also help in areas where the parts take a lot of beating and you don’t want it to crack.

So those are the basics. And yes you can make female mold off of what you have described. The mold surface is going to look just as good/bad as your “plug” surface.

hope that helps

#3

That helps quite a bit!

I’m more concerned with performance, but it’s carbon fiber, so unless I really screw it up it can’t be ugly ;).

Now to flaunt my ignorance… do you use just one layer of the carbon fiber twill and fill the rest with resin, or do you use multiple sheets? This is for a Mazda Miata front quarter panels, btw, where weight is a primary concern.

#4

Well you want to keep it at around 50/50 cloth to resin ratio. So if your 1 ply of cloth weights 1 lb, then you don’t want to use anymore than 1lb of resin on that part. With that said 1 ply isn’t going to be enough. If you want to use all carbon, I would recommend at least 3-4 plies of carbon. For stiffness without the additional weight penalty, I would also incorporate some kind of light weight ribs using foam or balsa for example.

#5

it all depends on the application. check my site out and you can see some of the stuff we do. for the scion tc carbon fiber hood we use one layer of cf however for certain parts on the mr2 we used 2-3 layers.