Improving the engineering strength of heat strengthened glass

Although glass is increasingly used as a structural material, glass is not produced to strength standards, like steel and concrete. Of the three types of glass: annealed, heat strengthened and fully tempered, only heat strengthened glass has the properties to function as a safe structural material. These properties are strength, resistance to stress corrosion cracking, and controlled fragmentation. In this paper the factors controlling the strength of heat strengthened glass are assessed. The dominant influence is the spread in compressive pre-strength. Opportunities for quality control of the compressive pre-strength are analysed using experimental results. The consequences for the predictability of the strength and the requirements for quality controlled are discussed.