The truth is you need an engineering degree and a specialism in FEA to analyze composite layups accurately as they are very complex.
Some advice though (btw i'm not a qualified engineer):
Things like stiffness and load bearing of a part are just as much down to the geometry and shape as to material used. How that shape distributes the loads on the part is very important, you can optimize the material layup after you have the most efficient geometry and structure.
Best thing to get close to selecting a more efficient layup would be to make a bunch of small samples that are identical in shape/very similar (go for a rectangle) but different in lay up / manufacturing technique and then try and do some controlled testing on them like a deflection test (if your interested in stiffness) and then select the layup with the most desired results.
The deflection test could be very low tech, you could simply clamp one end of the test specimen and then hang a weight off the other end and measure the distance the specimen has flexed with a ruler then you could compare results from others to see the relationship between the amount of carbon (or other materials
) in the part vs the stiffness. Don't assume it will be an even or constant relationship.
Carrying on from that if you want to understand as to why when you slightly increase the thickness of a core material in a composite panel is massively increases the stiffness then google "Second moment of area for a rectangle". This a very basic engineering principal which is made up of even more simple ones but is used a lot to design structures.
That will get you started or at least give you an inkling into what you are getting your self into
Dave