Dynamic fracture analysis of multiple defects in an imperfect FGM coating-substrate layers

•Analysis of an imperfect FGM coating substrate layers with several defects is studied.•Imperfect bonding between layers is assumed.•The imperfect bonding assumption has a significant effect on DSIF of cracks.•The analysis can be applied for any number of defects with arbitrary patterns.

Fracture behavior of an orthotropic strip with an orthotropic functionally graded coating weakened by multiple defects under time-harmonic excitation is investigated in this paper. Imperfect bonding between layers is assumed and the problem is divided to analytical and computational parts using distributed dislocation technique. The dislocation densities are employed to determine dynamic stress intensity factors for multiple smooth cracks and hoop stress on cavities. Cavities are considered as closed curved cracks without singularity. Several examples are provided to investigate the effects of angular frequency of loading, characteristic length of defects and material properties on the dynamic fracture behavior of interacting cracks and cavities. The obtained results can be used to design coating-substrate structures under anti-plane time-harmonic loading.