Congrats to ya Brian, and this is an excellent introduction to understanding stress analyses for our son. Ya never know, you may have a budding engineer in the family.
At my last job before I retired, we used lots of glue joints. Usually carbon fiber panels but ocasionally combinations of steel and carbon. We used Instron Universal Materials Testing Machines to pull the samples which gave us a graph of the tension, yield points and point of failure.
In sheer the glues are great but their peel strength usually leaves a lot to be desired. This is something to consider in its aplication or when your designing a joint. As you know, a tee joint welded from one side can be broken with relatively little force with the palm of your hand, but when filleted from both sides is nearly impossible to break. Joint design is very dependant on the way the load is being applied.
Testing a joint the way you are, does test the tensile strength somewhat but there is also the peel strength component to it because of the side loading of the joint. Normally a joint test specimen for sheer strength would be made using two single layers at each end sandwiched between two layers of material in the middle. That way there is more of an even pull on the joint with very little side loading. The bearing area as you mentioned also is a key factor on the strength of the joint.
I’m sure properly prepared glue joints would be more than adequate to hold body panels together, after all 30% to 40% of the 737 that takes you on vacation is glued together.
By the way, what glue are you using??
Denny Graham
Sandwich, IL
