Finite element modelling of brittle fracture of thick coatings under normal and tangential loading

This paper addresses coating fracture in hard brittle coatings subjected to combined normal and tangential loads through a finite element based methodology. The coating is modelled as an elastic layer perfectly bonded to an elastic substrate with a pre-microcrack, assumed to initiate at the contact trailing edge due to high tensile stress. The predicted results are consistent with previously published coating fracture results. The model predicts a significant effect of coating thickness on crack propagation for coatings with large elastic mismatch and the final propagated crack profile is predicted to depend on friction coefficient, coating fracture toughness and sliding displacement.

► Crack propagation for large elastic mismatch is sensitive to the coating thickness.
► Crack propagation risk is increased with increasing coating thickness for compliant coatings.
► Crack propagation risk is increased with decreasing coating thickness for stiff coatings.
► Increase in friction will increase the crack length and reduce the crack deviation.
► The amount of the contact displacement may influence the final crack length.