hello guys,i'm work with composites materials,but I have a question that I hope you help me to solve...how it's made this carbon steering wheel??

This part looks like it has a solid core that remains in place once the part has been cured, this is not uncommon. Chances are its a pre-preg carbon around a rohacell core  or similar  that has been machined to the correct size and shape. Once the core has been wrapped it is placed in the mould and closed up placed in  a bag and autoclaved to cure.

The Ebay item you are linking to IS a custom skinning job.  I have had this make of Audi steering wheel in my hands, and its a nice carbon skinning job, with new leather sewn on top in the two grip areas.  I think there is a few layers of either glass or CF under the top one, which makes the wheel a bit thicker than the standard one.

Steering wheels are not that difficult to skin, but to do a proper job you need to get a specialist to do the leather/alcantara parts, unless you are confident in that area as well

All the nicely CF skinned whells I hav handled vere stripped of all old foam and leather/plastic, and re-covered with leather after the CF skinning job.

I have seen af few wheels for older cars without airbag, that were a custom built up job in CF-only (two part mould for the rim, with the centre a part of one pf the moulds.  Grip areas were  Alcantara over hard foam rubber. (on top of narrower parts of CF rim )... Very light and strong --- cool stuff...

If your car has an old style bolted on wheel, with no airbag, you can build your own wheel from scratch.. the size and shape you like...

Good luck!

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we do these steering wheel they done custom a lot things here to write and steering wheel to do one of the hardest job with hands like shift knob!