Hi folks,

I'm gradually preparing for a big project of building an expedition camper habitation unit.  Essentially a 4x2x2m laminated panel box.  It will be built using aramid/carbon/PU foam/carbon vacuum laminated epoxy matrix panels.

My question is: Please can you point me towards where can I find information that will enable me to calculate the fabric weight/thickness required to give appropriate load bearing capacity?

Commercially available polyester/glass equivalent panels are always quoted in terms of thickness (typically 3mm glass/60mm foam/2mm glass) and this isn't very helpful for me because I can't translate it into fabric weight for aramid and carbon (the foam which will remain 60mm for thermal insulation purposes).

I need to be able to specify layup spec for:

1. Load carrying "beams" longitudinal will be essentially C section (like half RSJ), transverse will be I section (like RSJ).
2. Panel skins for load distribution to the "beams"

There are surely great books out the, which cover the basics. Search for "analysis fibre reinforced composites" or something similar. Sadly, I can't recommend one, because all the basic level literature I've read happend to be in German.
While those books will show you how to calculate your beams, you will most likely find no mathematical answer to the load distribution.
but I really do think you are making it unnecessarily complicated here. A camper box is no aerospace tec. And it sounds like some kind of expedition, which means that you don't know what exacly will happen to you box, and therefore you have to build it much stronger than the pure mathematics will tell you. Damage resistance against skin delamination caused by impacts will be a far greater issue than pure statics/dynamics.
With a 60mm sandwich core a incredible thin carbon skin would be sufficient to drive a car over it. Theoretically. Practically things look different.