Finite element simulation and experimental determination of interfacial adhesion properties by wedge indentation

Abstract

This paper presents our recent study on determination of interfacial adhesion properties of soft-film-on-hard-substrate (SFHS) systems using finite element simulation (FEM) and wedge indentation experiments. The objectives of this study are: (i) to simulate the interfacial delamination processes during wedge indentation experiments; (ii) to study the effects of interfacial delamination on the characteristics of the indentation load–displacement (P–h) curves, (iii) to determine the interfacial adhesion properties; and (iv) to compare the simulation and experimental results. During the FEM simulation, a traction-separation law is used to describe the interfacial adhesion properties due to the large-scale yielding during indentations. The effects of main parameters in the traction-separation law, i.e. interfacial strength and interfacial energy, to the initiation of interfacial delamination are studied by parametric studies. An interface energy-strength contour, which can be used to determine the interfacial adhesion properties of the thin-film/substrate systems based on a wedge indentation experiment, is developed from the outcomes of the FEM simulation of the indentations using wedge tips with the inclusion angles of 90° and 120°. Using the respective interface energy-strength contours, the interfacial energy and strength of a BlackDiamond® (BD)/Si system and a methylsilsesquioxane (MSQ)/Si system are determined. The simulated results are then compared with the previous experimentally derived interfacial fracture toughness values and some further discussions are given.