STUDY OF THE SUBSTRATE CRACK PENETRATION MECHANISMS IN CRACK-DETECTED COATING SYSTEM

The two-phase model and three-phase model of crack penetration/deflection at the interfaces in the crack-detected smart coating system were established utilizing the energy-based criterion. The effects of the relative crack growth length, the elastic mismatch parameters and the thickness of the interface layer on the ratio of energy release rates for the penetrated and deflected cracks were studied by the finite element method. When the substrate crack reaches an interface between substrate and driving layer, the results show that the ratio of energy release rate not only has a strong dependence on elastic mismatch between driving layer and substrate, but elastic mismatch between sensing layer and driving layer for the thinner driving layer as well. Moreover, with increase of the thickness of the driving layer, the dependence on elastic mismatch between sensing layer and driving layer decreases gradually. Compared with the experiment results, the numerical results can interpret the interface behavior of substrate crack and can be used for the optimization design of the crack-detected coating sensors.