If the parts already have no overlap on the edges, then bond on the joint to hold in place, then laminate carbon tape or cut strips of carbon fabric in several layers over both sides of the join to give actual strength. 

If they are still in the design stage then I would engineer an overlap, probably on the bottom for ease, to ensure you have a good large bonding area to bond the 2 parts together.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant

We are working on a prototype vehicle for SEM Asia competition. We are manufacturing this capsule-like vehicle's monocoque entirely from carbon fiber. I am looking for suggestion as to how to attach the top part of the vehicle to the flat floor ? We have the individual parts shown in the first picture and would like to attach them to form the monocoque shown in the second picture
Both parts are manufactured independently using VARTM, both parts will have excess flanges before trimming.
The upper part is a carbon fiber sandwich with 2mm Lantor soric as core.
The bottom part is a carbon fiber sandwich with 10mm PVC foam as core.

Thanks in advance