How thick would you need to make an all carbon fiber front bumper fascia?
thick enough not to break
hmm i would say at least 5 layers of 300 gr/m cloth (for example)
but then again, i tend to make my parts too thin anyway…
Street car or a race car? 
It really depends on the shape of the part and how its going to be used.
What is a ‘front bumper fascia’?
do a test 
I build sprintscooters wich reach 130 km/h. 2 layers of twill weave 200 grams seem strong enough for non stress areas. Next season we’ll switch to 1 layer of 300 grams biax cloth. I guess you could get away with 2 layers, certainly with some nice shapes
This is hardly enough info to provide a proper answer. It depends on so many things, and “thickness” alone means nothing.
My suggestion is to do your own testing of different sample panels for deflection, strength, and impact resistance. Gotta put in some work, just as most others do.
True…the amount of convex shapes and lengths of long spans determines most of what you ask.
Some areas can be a few layers ,for example…the complex curves…while the long straight spans may require bulkier reinforcement or more layers properly indexed within the weave.
I guess to test your thoughts…you could pull a lightweight built part and mount it…then poke around the surface finding the weak spots and then plan from there.
All true… shape factor will determine thickness.
I think the first one I will do like WorldWealth said… make it with about 5 layers of 200 gram and see from there.
I’m thinking due to the shape unidirectional cloth may be the way to go with just one or two layers in 90degree. so…
90, 0, 0, 0, 0, 90 This would probably also allow the bumper to deflect and return to it’s shape if it bumped something.
Z06 corvette fenders are laid up in prepreg 0, 0, 0, 0, 0, 90.
I’m thinking they did it this way so the fender would deflect if hit by a shopping cart or something bumped into the fender.
I think i am going to try a more simple body panel first and see how it does. May be a while anyhow.