Experimental investigations on the fracture strength of soda‐lime silica glass at elevated temperatures

The surface strength of glass plays a significant role when dimensioning glass components in structural facades. Commonly soda‐lime silica glass is used as material in architectural glass design. Different environmental conditions for example the load rate, relative humidity, surface flaws etc., but also the ambient temperature can have a strong influence on the resulting surface strength. The relationship between temperature, especially elevated temperatures, and surface strength of soda‐lime silica glass has so far been rarely investigated. Therefore, this paper methodically presents an experimental test setup for the determination of bending strength at elevated temperatures as well as first results. To determine the bending tensile strength of soda‐lime silica glass as float glass, the double ring bending test was conducted on specimens with small test surfaces according to EN 1288‐5. The double ring bending tests were performed using a tensile fatigue testing machine with furnace on circular glass plates of soda‐lime silica glass in a temperature range from room temperature to 550 °C. Before testing, the specimens were first pre‐damaged (inducing crack with diamond), stored and heat treated as the final pre‐treatment step. To determine the load rate for the experiments at elevated temperatures, the experiment was simulated in advance for the various temperatures using the finite element method with consideration of structural relaxation. To account for the structural relaxation, the Narayanaswamy model was utilized.