Hey there, thanks!
The keyblades are made by cutting out the basic shape out of plywood, then I take this stuff called DAS (you can find it any any AC moore or Michaels) and I apply that over the wood, it sticks pretty good, then I paint it and give it a few coats of polyurethane, add a pinch of love, then it's done. As far as structural integrity, they're more of a display item. I suppose you could use it if you're one of those hard-core cosplayers that keeps their props in glass cases (not as if I knew any that actually did that, just assuming ^__^). But it's certainly not one of those things that you can go around whacking things with. I generally just have it sitting on a katana stand in my room.
I'm going to try working with resin coated foam core this Christmas break (I can't get anything done thanks to finals), so I might come up with something that can really take a beating...hopefully!