Measuring Reliable Elastic Modulus on Brittle Materials by Indentation

Abstract

Mechanical properties such as elastic modulus can be tested and acquired by using various methods for materials. Nanoindentation is a reliable and robust tool to extract material properties in recent years. It is challenging to obtain brittle material’s elastic modulus traditionally because of cracks and defects generation. In this research, an indirect indentation method called the Chen-Prorok model, which is based on the Zhou-Prorok model can predict the brittle material’s elastic modulus by depositing a thin layer of film on it and indenting into the film without penetrating brittle material. This indirect method prevents damages on brittle material with a protective coating. Within this research, the film thickness was characterized by several ranges and tested to optimize the application of the Chen-Prorok model. The possible reasons were explained by analyzing the deposition and indentation processes. A different sputter method was chosen to coat film on the substrate that works better than previous methods in a few hundred nanometers range. The test results from nanoindentation are comparable to previous research within the nanoscale. The new sputter method enables the deposition process economically and efficiently compared with conventional methods.

Next, the key factors of elastic properties like Poisson’s ratio were discussed and decoupled in the indirect indentation method. This research confirmed that the indirect indentation method was barely affected by these factors. Furthermore, different thickness film and substrates combinations were examined to prove the model accuracy of extracted elastic modulus from brittle materials. Overall, this work improves the extraction of unknown brittle material’s elastic behavior conveniently and accurately in the nanoindentation field. Additionally, the deposition process was simplified and suggested by introducing a new method within hundred nanometers range for nanoindentation tests.