A new methodology for characterizing traction-separation relations for interfacial delamination of thermal barrier coatings

Abstract

The ability to characterize the interfacial delamination properties of thermal barrier coatings (TBCs) is of great technological importance for lifetime assessment of such coatings under service conditions. The purpose of this paper is to report on our novel experimental-plus-simulation-based approach to determine the relevant material parameters appearing in a traction-separation-type law which should be useful for modeling delamination failures in TBCs. We combine load–displacement measurements obtained from (i) a standard tension experiment; (ii) a novel shear experiment; and (iii) a novel asymmetric four-point bending mixed-mode experiment, with simulations of these experiments using a representative traction-separation law in a finite-element program, to extract the requisite material parameters for this traction-separation model. The methodology is applied to determine the material parameters for a TBC system (consisting of an air-plasma-sprayed yttria-stabilized-zirconia top-coat and an MCrAlY bond-coat sprayed on a superalloy substrate) which has been isothermally exposed to air at 1100 °°C for 144 h prior to testing.