Strength and fracture of glass in the lunar environment

Due to the lack of water on the moon, the effects of hydrolytic depolymerization - stress corrosion cracking - will be nonexistent in glasses produced and used on the moon. This would seem to make lunar glass very attractive for use in a wide variety of space engineering applications. We have applied the equation that describes stress corrosion cracking to lunar glass to show that, indeed, decreasing water vapor pressure results in an increase in strength. Experimental results on simulated lunar glass confirm this. The stress corrosion equation predicts an extremely high strength for glasses produced on the moon. This equation, however, cannot be applied to glasses under anhydrous conditions. In an environment completely devoid of water, the strength of glass will be determined by the fracture of the glass at the tip of a flaw, without the corrosive effects of water. Under this condition, in accordance with fracture theory, the strength of the glass will primarily be a function of the flaw size. Our experimental results show that the presence of surface flaws is more detrimental to the strength of simulated lunar glass than the effect of hydrolytic depolymerization.