Measurement of Reliable Indentation Elastic Modulus in Brittle Materials from Berkovich Nano Indentation

Abstract

Determining the elastic modulus of brittle materials from unloading segments during standard indentation testing is complicated by surface generations of cracks and other defects form. This work describes a method to reliably extract the elastic modulus of brittle materials from Berkovich indents under the continuous stiffness mode. It involves depositing and indenting a metallic film of known Poisson’s ratio onto the ceramic. The Zhou-Prorok model is employed and rearranged to express the experimental data as a function of the ceramic substrate’s elastic modulus. This generates a linear portion in the curve which directly relates to the substrate modulus and Poisson’s ratio. Measuring the slope of the treated experimental data reveals the substrate’s values. This method enables the elastic properties of brittle ceramic to be determined by generating and indenting a film/substrate composite with a metallic film. This enables the elastic behavior of the brittle ceramic to be assessed without the indenter penetrating it. This method can assess properties of an unknown film/substrate.