Besides, one last question remains. I will have to make the part in 2 parts, then glue them together. is it enough to stick the edges "edge to edge" or do I have to plan a trip? Knowing that I cannot put carbon fabric inside, or make it in one piece ...

Just bonding edge to edge would likely not be the most secure method

Some options include:

Design both moulds so that they deliver two symmetrical halves, then look to bond some carbon strips on the inner surface of one side, allowing an overlap that you can use to bond the other side to

or: make one side a cm or so wider than necessary. You can then look to use 1mm sheet wax (if 1mm is your target thickness) to create a temporary 'joggle' around the excess perimeter length of the mould. This creates a step in the part when de-moulded that would work in much the same way as the first option, but would be integral to the part itself and likely be more straightforward to bond to. A bit of careful measuring and planning required, but it can work really well if not needing to make loads of copies. The sheet wax would stick to the part, but it's not too difficult to scrape away afterwards

You might want to build-in that stepped edge to the mould itself, but that could give rise to issues with the stepped return causing a mechanical lock dependent upon the mould design, so a temporary solution using wax might work out better? 

Great!!! thank you very much, that’s what I thought ... I’m looking for as much strength as possible. I will think of the mold as well ;-)

Last question, before getting started ... I need it to be as solid as possible, how many layers of carbon fabrics do you recommend?
1 / 210g Plain Weave 3k Carbon Fiber (1st layer)
2 / 3mm 3D CORE PET 100 Foam
3 / 300g / - 45 Biaxial 3k Carbon Fiber?
4/ 650g 2x2 Twill 12k Carbon Fibre ?
5 / 375g 5HS 6k Carbon Fiber?
...
Thank you for all this precious information, I will ask you the photos of my work ;-)

thank you, these are boat doors, currently they are made of wood covered with carbon, very very heavy ... so no weight problem, just as much resistance as possible for the hinges and handrail.
Thank’s a lot.

thank you, but I don't want to proceed as the original Parts ;-) I will make a mold (several parts) and make empty parts but as solid « hard » as possible ...

but with several folds of carbon fabrics? Shouldn't we see through?