The effectiveness of resin-based repairs on the inert strength recovery of glass

• We investigate the effectiveness of resins in repairing surface flaws in glass.
• Testing shows that acrylic resin can strengthen glass but are weakened by water.
• Testing shows that strength recovery is dependent on flaw type, resin type, exposure.
• Results suggest that strengthening is caused by more than one mechanism.
• Study shows importance of statistical analysis of test data.

Glass used in buildings is often exposed to sources of surface damage which can have a significant effect on its strength. Existing research suggests that the flaws in glass can successfully be repaired by transparent polymeric resins, but the reasons for the increase in strength are not fully understood and the research to-date is not easily transferable to building applications.In this study 304 soda lime silica glass specimens covering three flaw scenarios, three repair scenarios and two post-repair exposures are tested in inert conditions. Contact angle measurements and post-failure fractographic analyses are also performed to determine wettability of the resin and resin penetration respectively.The results show that resin repairs can increase the inert strength of glass, but the results suggest that the strengthening in normal environments results from a combination of at least two mechanisms of which suppression of sub-critical crack growth is one. The acrylic resin used in this study showed the largest strength recovery, but exposure to water had an adverse effect on the inert strength of repaired specimens. Finally, the statistical analysis shows that the mean strength values often reported in literature are not always representative of lower fractile values required in engineering applications.