The indentation fracture toughness (k_c) and its parameters: The case of silica-rich glasses

The fracture toughness of several glasses, including soda-lime-silica and aluminosilicate glasses, was measured by both the indentation fracture (IF) and the single-edge notched beam (SENB) techniques. The flow densification mechanism occurring during indentation for silica-rich compositions leads to discrepancies between the two methods. The influence of the indentation load and the post-indentation fatigue duration on the indentation on the crack length and on the fracture toughness measurement were investigated. Fatigue curves (V-K) were obtained directly from indentation experiments and fatigue parameters were derived. The sub-critical crack growth resistance was found to be improved by increasing the silica content. In comparison with the studied oxide glasses, a Y-SiAlON oxynitride glass exhibits much greater fatigue resistance. The fatigue phenomenon has a major effect on the estimation of K_C from indentation-cracking measurements.