pic: What is that black goo ?

[MrForbes]

The type of attachment method you use should depend on a lot of variables. For our robot frame we are using fiberglass channel, but needed a plate to cover the bottom for mounting stuff, and to make it more rigid, along with corner braces. We decided that using 1/16" aluminum sheet and 3/16" rivets would be the best way to do this.

The curing time of epoxy makes it pretty much out of the question for quick fixes at competitions, but in the assembly Gdeaver shows above, it is indeed very unlikely that the epoxied joint will fail. You have to use your judgement about how likely it is that a glued joint will fail in a way that you can't repair it quickly if needed, and think about other ways to set up the joint so that it will be more reliable.