Reinforced glass: Structural potential of cast glass beams with embedded metal reinforcement

The shaping freedom of cast glass in combination with the robustness of the resulting voluminous components opens up new, exciting directions in the field of structural glass. Yet, cast glass components remain brittle, limiting their structural applications in hyper-static compressive structures designed with conservative safety factors. Stretching these limits, this work investigates the reinforcement of cast glass by incorporating metal bars during the casting process, in a similar principle to reinforced concrete. Aim is to increase the ductility of the composite glass component, provide a warning mechanism prior to ultimate fracture and secure a postfailure load-bearing capacity. The development of hybrid glass components involves kiln-casting experiments using different metal-glass combinations, of similar thermal expansion coefficients. The method of introducing the metal bar in the glass during casting, and the effect of the selected forming temperature are investigated. The resulting metal-glass interfaces are examined for micro-cracks using a digital microscope, and for internal stresses using cross-polarized light. Two material combinations are found successful; soda lime silica with titanium and alkali borosilicate with Kovar. A hybrid borosilicate-Kovar 30*30*240mm beam is further tested in 4-point bending until failure, while its displacement is measured by Digital Image Correlation. The flexural response of the composite component is compared to the performance of unreinforced cast glass beams of similar composition. Although reinforced and unreinforced specimens show a comparable flexural strength, the reinforced specimen exhibits a warning mechanism well before failure, a gradual fracture and a post-failure load-bearing capacity. These attributes encourage the further exploration of cast glass reinforcement.