Mechanical characterization of brittle materials using instrumented indentation with Knoop indenter

International audienceConventional Knoop indentation test is widely used for material characterization, and it is especially helpful for elastic modulus determination of ceramic materials by means of the Marshall's method. However, the use of Knoop indenter in instrumented indentation does not find the same usefulness due to the difference in elastic recovery along the different axis, particularly for highly elastic materials like ceramics and glasses. The unusual elastic recovery of Knoop impression has been reported in the literature but there is no convenient method allowing the consideration of the specific elastic response of a Knoop indentation in the computation of the mechanical properties of materials.This is the reason why a simple approach for an accurate determination of hardness and elastic modulus by instrumented indentation using Knoop indenter is proposed in this work. This methodology is based on a careful determination of the elastic recovery along the different dimensions of Knoop indent. As a result, we show that Vickers and Knoop instrumented indentation lead to the same values both for hardness and elastic modulus