How to project templates of carbon fiber for complicated surface?

General Composites Discussions Engineering Talk
#1

Hello,

I’m studying on technical university and my job is to project (to model) the way the carbon fiber has to be put in mould which will be the negative of car body. In brief, my work will be used to create a body of a car of composites.

The problem is that the car body must be made of aerodynamic ,continuous shapes (no low-radius edges) so when the composite will be put then the unwanted folds may appear or that fiber will have to be cut in some places. I have no such an opportunity to make mould first and then put fiber on it as a test and given this, determine the way the templates should look like experimentally . I have to do it the other way round- I have to predict the shape of these templates given the 3d cad model of car body first.

So I would like to know are there any books, articles, methods etc, which tell how to cut that carbon templates for a given surface? Maybe there some graphics which say how to determine the shape of these templates or software(I could import 3d model there)?

Thank you,

#2

Might not help, but CATIA has composite analysis and ply design. it will take the mold surface, and create a flat pattern (actually, I would think many graphics programs would do this)…but it can also drape fabric, and show you where there will be wrinkles, or too much shear.

Now, if you HAD the mold… :slight_smile:

#3

CATIA sounds so good…
But if I read correctly you don’t need actual moulds, just the digital negative surfaces, wich is not that hard to draft.

Rhino can flatten a surface, but only to a certain degree.
Some mathematic magic and Grasshopper in rhino can maybe be used to calculate drapable(as to the composite weave properties) offsets to flatten.

no low-radius edges

hahahahaha, the designer at the car company I worked for had no problem to let me do sub 1 mm radii. Took some time to figure it out for me. Caused a lot of complaining to him…

#4

the fiber is going to need to be cut and patched and tweaked to make it fit. Unless you design the part to specifically to avoid cuts. but when you put the 45 plys down, you’re limited in the length of each ply by the width of the roll, so overlaps will happen inevitably.

If you have a femal mold, then the surface will be smooth.

as for making the templates. There are some software programs that do this, but you’ll have to spend some money for those.

otherwise, you can make the molds, then make your templates from the mold using plastic sheet or something of the like, fit into the mold. there was one person here who told me he vacuum bags the mold, then draws the outline with a sharpie. Haven’t tried that but maybe good?

Creating patterns before the mold does require the software to do it.

If you’re worried about overlaps in the material, then don’t. If you’re mold is good, the surface of the part will be good.

#5

To the people above, Thank for your help, I will try it Catia.

To Sammymatik:

Of course I assume that there will be cuts and overlaps.

Yes it would female mould.

You say there is software for these. Can you say the names(except for Catia)?

I dont have the opportunity to manufacture the mould first but the layout of templates doesnt have to be very accurate. The aim is to prevent the construction from significant wrinkles and know where the important cuts should be placed

#6

Two others… fibersim, haven’t used it but I believe it has this feature as well as a host of others for composites.

Exact flat, also haven’t used it but got demos from the company. They started in making patterns for clothing and interiors but, have been greatly improving features for composites.

I’m confused about what you’re saying about the wrinkles. When you lay up the part there shouldn’t be wrinkles. If there are it means that you need to cut/dart the ply. You dont need to know where the cuts are before hand either, it’s a bit too much info to be concerned with. Really the layup is the easy part. Making patterns can be a pain but once you’re laying up is when you’ll really see how to fix any patterns issues. It’s possible to precut any relief cuts into the plys but, if you’re not going into high production it’s not a big deal.

Just be aware of where you have any tight radius corners and compound radius and that is where you would have issues. So long as the ply shape is about the right size, not too small, you can smooth the ply as you lay it up, patch any holes and you should be good.