Thoughts on using carbon fiber?

[Alfaguy]

I was thinking about using carbon fiber ( you can buy it in sheets) to strengthen the plastic surrounding the sun roof. Has anyone tried this?

 

[mike-y]

How would you attach/bond the CF to the plastic? maybe just glue or epoxy would work?

Working with CF is a bit tricky, and just FYI, do not try cutting it without using a proper respirator. CF dust can really wreck your lungs if inhaled.

 

[dtfd]

Where exactly are you planning on gluing down the CF to help with strength? Are you sure that the CF would actually be doing anything? What direction are the forces involved acting on the plastic coming from?

If you want to have some CF trimmed for aesthetics by all means go for it, I just don't understand what you mean by strengthening the plastic with CF.

It's also worth noting that carbon fiber's strength is along the axis of the fibers. It's not very strong at all against a perpendicular force to the direction of fibers.

How would you attach/bond the CF to the plastic? maybe just glue or epoxy would work?

Working with CF is a bit tricky, and just FYI, do not try cutting it without using a proper respirator. CF dust can really wreck your lungs if inhaled.

Also gloves and a long sleeve.

Shit is worse than fiberglass.

 

[kevinkar]

It's also worth noting that carbon fiber's strength is along the axis of the fibers. It's not very strong at all against a perpendicular force to the direction of fibers.

Which is why carbon fiber is usually multiple layups of plies at various angles (0, 45, 90, 135) to provide strength in more than one direction. That plus each ply is typically woven in a 90 degree pattern so a single ply is strong in at least two perpendicular directions. But a lot of stiffness is also imparted by the resin used as well which of course bonds all the plies together creating one very rigid panel.

Problem here is you'd have to bond the carbon fiber to the roof and a lot of strength would be dependent on the bonding agent, epoxy or whatever is used to attach the carbon fiber. In aerospace design, any "glue" needs to be stronger than the items being bonded to ensure the bond functions as good as or better than the parts. You want the part to fail before the bond. Here I'd expect a carbon fiber panel to be much stiffer than the roof panel and, with regular flexing, heating/cooling, etc, I'd expect the carbon fiber to detach at some point due to the different stiffnesses. You'd also want to rivet it in place to keep it attached if/when the bond fails as well as carry some of the loads between roof and carbon fiber bits.

This likely would not help unless done right and would be more for looks than anything.

 

[dtfd]

Which is why carbon fiber is usually multiple layups of plies at various angles (0, 45, 90, 135) to provide strength in more than one direction. That plus each ply is typically woven in a 90 degree pattern so a single ply is strong in at least two perpendicular directions. But a lot of stiffness is also imparted by the resin used as well which of course bonds all the plies together creating one very rigid panel.

True, what I was referring to by the axis of the fibers is the fact that a carbon sheet if laid flat (what I'm imaging OP to be talking about) has its strength on the x and y axis. Carbon fiber is relatively weak to forces along the z axis, a single sheet of cf WILL bow regardless of weave type. More layers will of course remedy that but if they're worried about strength using a material whose strength is dependent on the direction the force is coming from isn't the best bet.

Aluminum might be the better (and cheaper) solve here.

 

[Stanislao]

i've been playing with carbon fiber, forged carbon and carbon fiber layering both in plastic .
forged carbon is a pain to work with i would not recommend all for aesthethic only.


I think OP is trying to install a carbon fiber layer over the sunroof panel. pretty similar to what is done on interior or mirror covers.
i think it would help prevent the sunroof from cracking because it cracks mainly because weather exposure weakening the plastic trim. Also 1 or 2 layers of carbon fiber is extremely flexible and probably if it cracks it would not notice under the layers of carbon fiber.
its barely impossible to work in the roof. you would need to buy a new one and carbon fiber layer it.