Repetitive nano-impact tests as a new tool to measure fracture toughness in brittle materials

Along this work, the feasibility of using repetitive-impact tests with a cube-corner tip and low loads for obtaining quantitative fracture toughness values will be shown. It will be displayed that the impacts are able to produce a cracking similar to the pattern developed for the classical fracture toughness tests in structural ceramics. Moreover, it will be shown how it is possible to identify the crack geometry evolution from Palmqvist crack to half-penny crack with each new impact being able to study the proper evolution of fracture toughness in terms of different indentation models and as a function of the strain rate, ε˙. Fracture toughness values of Al2O3 descend from ∼6.10 MPam (ε˙=103s−1), to ∼3.52 MPam (ε˙=10−3s−1). These values correspond to those found in the literature for α-Al2O3 demonstrating that the use of repetitive-nano-impact tests provides good reproducibility, high accuracy for reliable fracture toughness testing.