Assessment of the mechanical behavior of bonded glass-to-glass transparent epoxy adhesive joint at elevated temperatures for load-bearing elements

Abstract

Glass is increasingly used as a structural material in buildings, not only for enclosing spaces but also for bearing loads. To meet architect requirements for a uniform structure without appearance disturbance, adhesively bonded joints are preferred over mechanical fasteners. However, in the construction industry, most technical guidelines cover only soft structural silicone sealants, while stiffer adhesives like epoxy resins are not considered. Alternatively, the specific transparent epoxy adhesives offer a high potential for bonded glass assemblies, enabling thinner joints and a fully transparent junction. Indeed, under real service conditions, elevated temperatures are one of the worst factors affecting the mechanical properties of structural bonded joints. Therefore, in this paper, an experimental program was conducted to evaluate the performance of transparent bonded glass joints with epoxy resin over a wide range of temperatures. Tensile and shear tests were performed on bulk-cured adhesive samples and bonded glass-to-glass block shear specimens respectively, at room temperature (RT), 40, 60, and 80 °C. The differences in surface characteristics such as roughness, wettability, and surface free energy (SFE) between both glass sides were examined. The results showed that tensile and shear strengths decreased with increasing temperatures. Furthermore, the shear strength was influenced by the surface properties of the glass sides. At all tested temperatures, the rougher bonded glass side specimens revealed higher shear strength coupled with a mixed failure while a loss of adhesion characterised the smoother glass surfaces.