This is really cool! Don't all the ladder test cases that achieve >~50 simply snap the PETG implements though? So isn't the test capturing the force to snap PETG at that thickness vs. the actual bonds?
- adhesive failure: the adhesive splits from the substrate
- cohesive failure: the split occurs within the adhesive
- substrate failure: the split occurs within the substrate.
Whichever of these that is weakest limits the maximum strength of the bonded item.
He concludes that those adhesives are causing the PETG to become brittle, and you should prefer others which don’t.