HOLD on there cowboy! Nice to see a science project that is interesting to us bolters. Now about the results (there is always a guy like me). The surface area of the glued pieces is much greater than the welds. The bolted breakthru is predictable because of the thin metal and holes too close to edge. From the pictures, you have overlapped the bonded section to create about a 30-50 times greater surface area. The "beads" of weld and glue must be the same or the surface area must be the same. The Butt welded piece seems to have broken loose at the weld, as in cold weld or no penetration. Bonding may still prove to be stronger, but not by this test. Manufacturing uses bonding because it is strong enough for their application and has many manufacturing advantages over welding. One of the biggest advantages is that the surface treatment is not damaged by bonding and corrosion will not be a factor between the pieces. This opinion is intended for discussion here and is not for your 10 year old to see. I am not intending to say anything but good about his experiment, knowledge and the fun he must have had with his Dad.

Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn