Mechanical Characterization of Coatings Using Microbeam Bending and Digital Image Correlation Techniques
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A new technique for characterizing end-supported microbeams of coating materials is presented. Microbeams are fabricated using micro-EDM machining to isolate the material under investigation from the underlying substrate. Three- and four-point bending is realized by a custom-built microspecimen testing system, and digital image correlation is employed to capture full-field strains and displacements in theses microbeams. These experiments provide the foundation for the use of finite element modeling and inverse methods to determine the mechanical properties (elastic moduli, strength, interfacial toughness) of the coatings. Here, the experimental details of the microbeam bending experiments are explained, discussed and illustrated through application to a multilayered metal/oxide/ceramic thermal barrier coating system commonly used in aero-turbines.
KeywordsDigital image correlation Microbeam bending Thermal barrier coatings Aerospace materials Young’s modulus Fracture toughness
This work was funded by AFOSR under the MEANS-2 Program (Grant No. FA9550-05-1-0173). The authors would like to thank A.G. Evans and J.W. Hutchinson for creative and enlightening discussions that allowed this technique to come to fruition. We also thank M. Maloney and D. Litton of Pratt and Whitney (USA) for providing the specimens, S. Faulhaber for preparing the disk specimens, J. Mraz (Smaltec) for fabricating the microbeam specimens, and W.N. Sharpe, Jr. and J. Sharon for technical support. C.E. would like to acknowledge partial financial support from the Max-Planck Society. D.S.G. acknowledges support from an Alexander von Humboldt Postdoctoral Fellowship.
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