Micro Indentation Fracture Toughness Assessed by Energy-Based Method: The Method Improvement and Affecting Factors

Abstract

This paper reported an improved energy-based method to assess the fracture properties of a quasi-brittle material (cement paste) by using micro indentation technique. The model was initiated by the additionally generated fracture energy that is assumed to be averagely distributed in indentation, and only involves the load-displacement curves that follow power functions. An explicit equation for estimating the plastic energy considering the effect of holding procedure that has not been considered before was established, which, together with the principle of energy balance, allows us to assess the fracture energy, energy release rate and fracture toughness of quasi-brittle materials. The accuracy, reliability and robustness of the model were validated by the experimental data with changing the maximum load, loading speed and holding time. Overall, the micro fracture testing method developed here provides an efficient way to assess the fracture properties of quasi-brittle materials in micro scale.