A computational framework for the interplay between delamination and wrinkling in functionally graded thermal barrier coatings

Stiff films bonded to compliant substrates are used in a wide range of technological applications and especially in thermal barrier coatings (TBC). Thin films can be made of Functionally Graded Materials (FGMs) with a heterogeneous composition that usually range from a metallic to a ceramic phase. Aiming at investigating the phenomenon of delamination of thin FGM layers from compressed elastic substrates, a fully 3D nonlinear computational framework combining nonlinear fracture mechanics based on a novel interface element formulation for large displacements and a solid shell finite element to model the thin film is proposed. A comprehensive numerical analysis of delamination in TBCs is carried out, paying a special attention to the interplay between fracture and wrinkling instabilities. Results of the computations are also compared with benchmark 2D semi-analytical results, showing good accuracy of the proposed method that can be applied to general 3D configurations that are difficult to address by semi-analytical approaches.