Advanced nanoindentation testing: Beyond the Oliver–Pharr method

The Oliver–Pharr method was developed in the 1990s and since then, it has revolutionized the ability to extract mechanical properties besides hardness values from simple instrumented indentation, so-called nanoindentation, experiments. It relies on the elegant relationship between the applied load and the indentation depth to calculate the contact stiffness, and from there the material’s hardness and its elastic modulus. This breakthrough had far-reaching implications, allowing scientists and engineers to explore materials behavior at very small length scales. However, as the field of nanoindentation evolved, researchers recognized that there was much more to uncover. To address complex challenges such as heterogeneous materials, thermally activated deformation mechanisms, or nonambient testing conditions, advanced nanoindentation techniques have emerged. These offer an expanded toolkit for characterizing materials individually, within composites, or system components. The methods also allow us to gain deeper insights into the underlying mechanical deformation behavior involving various environmental conditions and a wide range of testing temperatures and deformation rates. In addition, they open the field toward evolving high throughput and statistical analyses.