The Strength of Aged Glass

Glass is known for its excellent durability, but the strength of glass is very sensitive to the characteristics of its surface, which in turn accumulates damage during its service life. There is however a lack of strength data on weathered or aged glass, particular on thermally or chemically treated glass.

In this study a carefully calibrated sand trickling test is used to reproduce the surface damage found on naturally weathered annealed glass after 20-years in service. The sand trickling regime is then used on of different types of glass that vary in terms of glass composition (soda-lime-silica / alumiosilicate) and residual stress profile (annealed / fully toughened / chemically toughened / bi-toughened). The aged glass specimens and un-aged control specimens are tested destructively in a coaxial double ring set-up and fractrography is used to identify and measure the critical flaw size on each specimen. The strength data are analysed statistically and the design strengths for each glass type are obtained.

It is found that all glasses suffer a loss in strength after artificial ageing, but some treatments are significantly more resistant to ageing than others.