There are now several different types of composite parts readily available for use. I was interested earlier in the pultruded carbon rods, but then I was thinking how to connect them with each other easily and there was no good solution for that. I was randomly surfing the web and found this one:
Ready-made carbon sheets (could be used as bulkheads and wing ribs)
Pultruded carbon rods
Connection parts for the pultruded carbon rods.
With the connection parts available for example from this company, one could build a new kind of tube-fabric airplane or facet mobile, just glue some rods and sheets together and you are done. No welding required and end result will be stronger and lighter! It could be possible also build wing spar/internal wing structure like on the sky lifts from the rods and connection parts. It could be interesting how much longer wings could be achieved by optimized rod structure (and it could lead to higher aspect ratio for the same weight without aileron reversal and flutter problems).