Modelling the limits of coating toughness in brittle coated systems

As the accuracy and applicability of existing indentation models to assess coating toughness can be affected by many factors (such as fracture mechanisms, crack type, coating thickness, cracking size etc), it is uncertain to what extent the values obtained are quantitatively correct. Therefore, an estimation of the limits of coating toughness is very useful. In this paper, a limits model is proposed to assess coating toughness based on numerical and phenomenological analysis. This approach provides universal expressions for the lower and upper bounds of fracture dissipated energy for indentation performed under load control and displacement control. It has shown that the lower bound determined in this study is also a good estimation of the coating toughness.