Environmental Fatigue of Silicate Glasses in Humid Conditions

Failure strains of commercial silica, soda-lime-silicate, and E-glass fibers were measured using two-point bending in room temperature humid air. Humidity dependence and dynamic fatigue behavior were studied, and the fatigue reaction orders in terms of humidity were determined. In the humidity range tested (similar to 0.1% to similar to 100%), the dynamic fatigue parameters for silica and E-glass are found to be greater in lower humidity (similar to 0.1% to similar to 10%), whereas the fatigue parameter for soda-lime-silicate is independent of humidity. The humidity dependence of failure strains for all three glasses was more pronounced in high humidity (similar to 10% to similar to 100%) than in low humidity (similar to 0.1% to similar to 10%), indicating that the reaction order decreases with decreasing humidity. These observations were correlated with the different structures of the glasses and their corresponding fatigue mechanisms.