Molecular simulations of the strength enhancement of pre-stressed silica glass upon exposure to moisture

Molecular dynamics simulations were used to evaluate the fracture strength of pre-stressed silica glass exposed to water molecules, with and without heating. The pre-stressed wet glasses had a strength enhancement of 5-7% in comparison to the original dry glasses. Heating the glasses while pre-stressed with included water resulted in an even greater strength enhancement. The glasses with a higher concentration of structural defects in the dry glass have an expected lower dry-glass strength in comparison to the glass with fewer defects. However, the weaker dry glass shows a greater strength enhancement after pre-stressed water exposure caused by the increase in the silanol concentration in the more defective glass that offsets the otherwise weakened glass. Increased silanol concentration has been shown to increase the expansion of silica glass, creating an increased compressive stress on the pre-stressed-wet glass relaxed to original dimensions, allowing for an increased strength enhancement.