Measuring interface parameters and toughness - A computational study

Interface toughness of a ductile thin film sandwiched between substrates, G amma (ss), can be evaluated from test data which exhibit steady crack growt h characteristics. Gamma (ss) is the sum of the adhesion energy of the inte rface Gamma (0) and the plastic dissipation in the film and substrates Gamm a (p). A proper characterization of the quality of interface adhesion requi res knowledge of two quantities: the adhesion energy Gamma (0) and the adhe sion strength <(<sigma>)over bar> In the present investigation based on a f our-point bend geometry, the interface between the ductile film and the sub strate is modelled by an adhesion law described in terms of Gamma (0) and < (<sigma>)over bar>. The effects on interface toughness of <(<sigma>)over ba r>, of Gamma (0), and of the geometry and material properties of the layers are studied using a computational model of the test geometry. Through fitt ing model predictions against test data, a method of evaluating Gamma (0) a nd <(<sigma>)over bar> is suggested. (C) 2001 Acta Materialia Inc. Publishe d by Elsevier Science Ltd. All rights reserved.