“…However, as was shown in our previous work, the results may be hard to interpret since they are indirectly asso ciated with material toughness (not just interfacial toughness) and deformation modes, and may even give contradicting results [6,7]. In our experimental work, we investigated Rockwell indenta tion of thermal barrier coatings, where the indentation was con ducted on the surface of a thermal barrier system so to establish the interfacial fracture toughness [6].…”