While a carbon-fibre cover for your Iphone may seem like a very nice gadget, in fact it is not --- real CF is electrically conductive, and will dampen or "attenuate" the near Gigahertz radio transmissions that makes your Iphone work ...

Been there --- tried that, but actually copying the part in black Diolen "carbonfibre-look-alike" will probably work fine :-)
For my first try i simply used the actual Iphone as "plug" just wrapped it tight in shrink wrap... (old 3GS phone) the result was great looking but caused very poor reception in marginal areas ... I used the very light 90 g/m 1K "mini-roll" for the wraparound part, and some ordinary 200g twill for the back.
After curing the part snapped off easily, and after trimming, sanding and a layer of clear laquer it looked great... but it ended up being cut up to use for some small parts for an RC - car ...hmmm ....
I have made quite a few CF covers for metal cups (camping gear) Very simple to make, almost always come out very nice .. Also made a few boxes for (sun)glasses. Use a cheap plastic one for parts and the two halves for "plugs" ... makes great gifts ....
"Sapere Aude"... Dare to KNOW!
The written word is the only truly efficient vehicle for transmitting a complex concept from mind to mind...
103% of all people do not understand statistics...
Do not adjust our mind, theres a fault in reality :-)