If you are using wood, one material comes to mind for strength: LVL/Microlam
Laminated veneer lumber/engineered beams. It's essentially a plywood beam two inches thick.
http://www.weyerhaeuser.com/files/do...351_TB-500.pdf
You can apply whatever veneer you like--walnut, bubinga, jotoba, you pick!
See if you can make your joints as well as these guys!
https://www.youtube.com/watch?v=QPUPyuz_ink and
https://www.youtube.com/watch?v=Hk4cwtQJmwU