[DonRotolo]

40x40 is overkill for almost every application in FRC.

That being said, the material is plenty strong, its weakness are where it connects together. Fasteners that depend on friction (such as T-nuts) absolutely will come loose and move. Maybe OK for superstructure, but not for a drive base.

You will be far better served by getting several pieces of extruded box tubing in 1" x 1" with 1/16" and 1/8" wall, plus some 3/4 with 1/16" wall for smaller mechanisms. You will also need some sheet aluminum, start with 4x4 sheets on 1/32", 1/16", 1/8" and maybe 0.093". (It would be very rare to need anything thicker)

Try onlinemetals.com, but beware: They will give you an "extra 5% off" coupon after your first order...so place a small order first, then go for broke. They also run sales on occasion, like 25% off, or free shipping, ror something - so place that first order then see what comes up...