Temperature distribution and stress relaxation in glass under high temperature exposition

High temperatures, especially non-uniform temperature distributions, on glass structures can induce stress relaxation, viscous material behaviour and glass fracture. Temperature exposure of toughened glass to 290 °C and above can result in a partial reduction in strength of the glass component and, in case of fracture, a change in the fracture pattern due to stress relaxation. To achieve a better understanding of the heat transfer in monolithic and laminated glass, test series in an electric furnace on different glass specimens were carried out. The specimens were made of two compositions, namely monolithic or laminated made of soda-lime silicate glass in a variety of thickness. The test set-up was chosen in a way to create an inhomogeneous temperature distribution from the heat source through the glass in order to create a more realistic load case than an assumption of homogeneity. The results of the experimental examinations were used to develop a first numerical model that was used to visualise details (e.g. temperature and stress distribution). The paper presents results of experimental and numerical examinations to the determination of the temperature and stress distribution in different glass compositions and experimental examinations of the stress relaxation during high temperature exposure and effects on fracture pattern in thermally toughened glass plates. This will pave the way towards understanding glass structures exposed to heat and fire and, as a vision, will form the fundamentals of a design concept.