Maximum shielding stress intensity factors in silica

Abstract

When water penetrates into silica surfaces near a crack tip, it reacts with the SiO$_{2}$ network and generates hydroxyl $\equiv$SiOH. Due to the hydroxyl generation, silica expands and gives rise for swelling stresses. The consequence is a fracture mechanics shielding stress intensity factor K$_{sh}$<0. The fracture mechanical treatment of swelling in the crack-tip region is significantly complicated by the occurrence of damage due to the production of hydroxyls. A maximum possible shielding effect is obtained by using an asymmetry parameter h=1 in the crack wake ($\delta$$_{h}$<0) and neglecting the tension region ahead the crack tip, where strong damage is present under hydrostatic tension ($\delta$$_{h}$<0) .