Three dimensional analysis of periodic cracking in FGM coatings under thermal stresses

A three dimensional finite element method is used to examine periodic surface cracking problem in a functionally graded coating subjected to transient thermal loads. The ceramic/metal FGM coating is assumed to contain periodic semi-elliptical cracks and to be perfectly bonded to a homogeneous substrate. The composite structure is subjected to transient residual/thermal stresses. Temperature and displacement fields are computed using a three dimensional finite element approach. Finite element models are created by considering a unit cell in the periodic structure. Mode I stress intensity factors are evaluated by means of the displacement correlation technique (DCT). Presented results illustrate the influence of crack periodicity on the transient behavior of the stress intensity factors.