Lifetime Assessment for Thermal Barrier Coatings: Tests for Measuring Mixed Mode Delamination Toughness

Refinements to the Mixed-Mode Bending Test for Delamination Toughness

The mixed-mode bending (MMB) test for delamination toughness was first introduced in 1988. This simple test is a combination of the standard Mode I (opening) test and a Mode II (sliding) test. This MMB test has become widely used in the United States and around the world for mixed-mode toughness measurements. Because of the widespread use of this test method, it is being considered for standard...

Delamination of multilayer thermal barrier coatings

Multilayer thermal barrier coatings (TBCs) on superalloy substrates are comprised of an intermetallic bond coat, a thermally grown oxide (TGO) layer, and a porous zirconia top coat that provides thermal protection. The TGO attains a thickness of 1±10 lm prior to failure, while the bond coat and zirconia layer are each about 50±100 lm thick. The preferred method for manufacturing TBCs comprises ...

Reaction, transformation and delamination of samarium zirconate thermal barrier coatings

Delamination resistance of thermal barrier coatings containing embedded ductile layers

Micromechanical models are developed to explore the effect of embedded metal layers upon thermal cycling delamination failure of thermal barrier coatings (TBCs) driven by thickening of a thermally grown oxide (TGO). The effects of reductions in the steady-state (i.e. maximum) energy release rate (ERR) controlling debonding from large interface flaws and decreases in the thickening kinetics of T...

Mixed-Mode Bending Method for Delamination Testing

A mixed—mode delamination test procedure was developed combining double cantilever beam (DCB) mode I loading and end-notch fixture (ENF) mode II loading on a split unidirectional laminate. By loading with a lever, a single applied load simultaneously produces mode I and mode II bending loads on the specimen. This mixed-mode bending (MMB) test was analyzed using both finite-element procedures an...