Before we start your going to need the "carbon fibre" texture GET IT HERE (right click save-as).
Once you've downloaded the carbon fibre texture load up your image you want to carbon fibre, im using a honda s2000, just a random image off google. Right then start off by duplicating your image and selecting the "pen tool", im going to carbonize the bonnet so with the pen tool im going to select the bonnet (zoom in to ensure its nice and neat).
Now with the bonnet selected copy & paste to a new layer and name it bonnet. Now open the carbon fibre texture copy & paste it onto your car image or what ever image your using, postion it just over the bonnet.
ctrl + click your bonnet layer to select it.
Select your carbon fibre layer and inverse the selection "shift + ctrl + i" then hit the delete key, you should be left with something like this.
Now select your bonnet layer and desaturate it "shift + ctrl + u"
then lower the brightness to -100 "image > adjustments >
brightness/contrast" depending on how dark you want it, and last but not
least lower the opacity down to 50% on your carbon fibre layer, you
should be left with something like this.
