I would look at a structural adhesive such as our ET515 Semi Flexible 15min Professional Epoxy Adhesive as it has a high flexural strength meaning it is less likely to crack under shock or vibration. 

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

What adhesive do you suggest to join there parts together?

I have used carbon fiber filler to fill the gap in bumper where I joined glass fiber parts to a plastic, and that worked well. I guess that it would be good in this case too. But I don't know what adhesive I should use.

This is mostly body shop work at this stage.  You could use flexible fillers when smoothing the join in, or actually scarf it in with a skim of carbon or thin layers of fibreglass to make a broader join with less chance of cracking.  There are flexible fillers and flex additives for paints for just this kind of thing  - its commonly seen on fibreglass bodykits and also many plastic moulded panels on cars that are painted.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

Hi, I have the same question. I hope that somebody has experience of this. I have widebody rear fender molds, and my plan is to make carbon fiber or fiberglass parts and glue those to the car. The seam would be visible like in the first post photo. I'm afraid that the paint will crack from the seam. 

What is the correct procedure to do this, or is this doomed idea?

Trying to mold my new carbon flares into the body of my car.  I have heard that bonding these together might cause the carbon to crack when the car is adjusting to temperature changes like washing the car with cold water on a hot day.  Would you guys have any recommendations for an adhesive to use to bond the two materials?  Was planning on using 3m 08115 then short strand fiberglass around the seam to add a little more structure. 

Joe