Finite element simulation of tensile bond strength of atmospheric plasma spraying thermal barrier coatings

Before thermal cycling or thermal exposure, tensile failure of atmospheric plasma spraying (APS) thermal barrier coatings (TBCs) usually occurs by spallation of the ceramic coating at or near the bond coating, due to the accumulation of microcracks damage. In the current paper, finite element geometric models based on the real microstructural image of TBCs are generated, and the microcracks growth induced by the uniaxial tensile loading is simulated by employing LS-DYNA code with a failure criterion determined by maximum tensile stress of yttria partially stabilized zirconia (YSZ). Additionally, the modified Brazilian disc specimens with a central hole are used to obtain the intrinsic static failure criterion of non-defective YSZ. By means of a statistical method in conjunction with finite element method (FEM) results, the tensile bond strength of APS TBCs is calculated as 40 MPa in this paper. Meanwhile, damage accumulation and microcrack growth can be observed vividly by simulation processing. The numerical simulation result agrees well with the corresponding experimental result. It is shown that the methodology developed in this paper is very efficient in understanding damage evolution in TBCs.