Insights into stress corrosion and thermal healing of annealed float glass

The strength of annealed glass is governed by the quality of the edge finish and the presence of surface and edge flaws. While stress corrosion from environmental water (vapor) decreases strength, thermal treatments have been reported to partially increase strength by blunting or healing flaws. However, comparative studies for combined effects of these mechanisms remain unclear, as individual datasets are often tested under varying conditions. In this study, 8 mm thick float glass specimens were tested in four-point bending under controlled displacement rates (0.1-10mm/min) to evaluate the influence of stress corrosion, flaw type and thermal healing. Comparisons were made across series with machine-cut edges, including burr and non-burr orientations, and Poly-V polished edges combined with and without additional heat treatment at 560 ^o C for 2 up to 48 hours. The results confirmed that decreasing the displacement rate decreases strength with the effect being more pronounced for stronger specimens that experience longer times to failure. The influence of thermal treatment on glass strength was found to be non-uniform and selective. Strength increase was mostly observed for specimens with small flaws situated on the upper tail of the Weibull distribution for polished or burr edge glass. However, for larger flaws, limited or no effect of “thermal healing” was noted. Unexpectedly, thermally treated glass tested with the non-burr side in tension, exhibited a decrease in strength, potentially attributed to a shift in fracture origin from surface to edge flaws, suggesting selective flaw blunting after heat treatment. These findings provide new insights into the interrelationship between strength, thermal healing and stress corrosion, highlighting the importance of considering flaw typology, location and severity. The data obtained can support the development of future glass failure prediction models and open opportunities for consideration of flaw healing strategies in structural glass design standards.