Over the past several years, there has been an increase in the use of triple-glazed insulating glass (IG) units as opposed to the more well-researched double-glazed IG unit. This expanded use is driven primarily by the ever-increasing demand for more energy-efficient windows and an increase in energy costs. The addition of the third glass plate creates a second gas-space cavity that significantly increases the thermal performance of the triple-glazed IG unit over the double-glazed IG unit.
To reduce the use of raw glass material and overall unit weight of a triple-glazed IG unit, there is an interest in inserting a thin-borosilicate glass plate between two thicker glass plates. The primary purpose of the thin-borosilicate glass plate is to divide the gas-space cavity while the purpose of the outer glass plates is to carry the uniform pressure load. However, the thin-borosilicate glass plate will need to resist some smaller amount of the uniform pressure load.
Currently, there is little widely published information about the strength of thin-borosilicate glass to resist uniform pressure loads. As such, this paper presents the results of testing performed to determine the overall strength of thin-borosilicate glass for use later as plates in a triple-glazed IG unit. This was accomplished using controlled weak-axis, four-point bending testing on 0.5-mm thick borosilicate glass specimens that were subjected to two different loading rates. The primary outcome of this testing shows that the strength of the thin borosilicate glass is, at a minimum, analogous to the typical strength data measured for freshly-manufactured annealed soda-lime float glass and may be well suited for use as the third plate in a triple-glazed IG unit.
