Energy-Based Analysis of Nanoindentation Curves for Cementitious Materials

Abstract

Energies dissipated during indentation are often employed to develop mathematical relations for the computation of nanoscale mechanical properties of a material. In this study, experimental nanoindentation curves pertaining to cement paste are extensively analyzed using the energy principle. As a result, energy ratios are found to be capable of accurately modeling the indentation behavior when used as parameters specific to a given nanoindentation curve. The efficacy of the elastic energy recovered during unloading in the determination of contact depth and initial unloading stiffness is also evaluated herein. While the expression representing the unloading curve yields an accurate value of contact depth, it generally overestimates the initial unloading stiffness. Considering this shortcoming of functional analysis-based expressions used for representing nanoindentation curves, a new procedure for the computation of initial unloading stiffness is proposed. The results obtained with this new approach are in reasonable agreement with those obtained experimentally.