A model for the evaluation of indentation crack arrest fracture toughness of supported films

A simple model is proposed for the evaluation of crack-arrest fracture toug hness K-Ic0 of thin films by Vickers indentation. This approach applies to films thinner than the penetration depth of the Vickers indenter. The model equations are provided in closed form, even though they are so complex tha t they must be integrated numerically in practical applications. The proble m of the evaluation of K-Ic0 for thin films and substrates is derived in ge neral form and applied to three cases: (i) evaluation of K-Ic0 for the film in the case that the depth of the crack in the film is smaller than the fi lm thickness, (ii) evaluation of K-Ic0 for the film in the case that the cr ack emanating from the film either crosses the film/substrate interface or is stopped by it, (iii) evaluation of K-Ic0 for the substrate in the case t hat the crack emanating from the film crosses the film/substrate interface. The model was tested with original and literature experimental data: (i) r evision K-Ic0 values of electroless Ni-P thin films were re-evaluated, (ii) K-Ic0 of electroless Ni-P thin films of various thickness with various loa ds were measured (original data) and computed, (iii) K-Ic0 of electroless N i-P substrates coated with electrodeposited Au-Cu were measured (original d ata) and computed. (C) 2001 Kluwer Academic Publishers.