Hardness and toughness of sodium borosilicate glasses via Vickers's indentations

Abstract This study investigates the mechanical response of sodium borosilicate (SBN) glasses as a function of their chemical composition. Vickers's indentation tests provide an estimate of the material hardness ( H V ) and indentation fracture toughness ( K C VIF ) plus the amount of densification/shear flow processes. Sodium content significantly impacts the glass behavior under a sharp indenter. Low sodium glasses maintain high connected networks and low Poisson's ratios ( ν ). This entails significant densification processes during deformation. Conversely, glasses with high sodium content, i.e. large ν , partake in a more depolymerized network favoring deformation by shear flow. As a consequence, indentation patterns differ depending on the processes occurring. Densification processes appear to hinder the formation of half-penny median–radial cracks. Increasing ν favors shear flow and residual stresses enhance the development of half-penny median–radial cracks. Hence, K C VIF decreases linearly with ν .