Effect of water content in phosphate glasses on slow crack growth rate

Slow crack growth in phosphate glasses with different water contents was me asured at 225 degrees C and room temperature under different water vapor pr essures using double-cleavage-drilled compression (DCDC) samples. Higher wa ter vapor pressure caused a faster crack growth velocity at a constant temp erature for all samples. At 225 degrees C under a constant water vapor pres sure, glasses with higher water content exhibited greater crack velocity. H owever, at room temperature under a constant water vapor pressure, samples with lower water content exhibited a higher crack velocity. This room tempe rature behavior is probably caused by water uptake by the sample during the crack growth measurement. In support of this hypothesis, weight gain was o bserved when the glasses were exposed to humid atmosphere at room temperatu re, with the samples having lower water content exhibiting the greater weig ht gain. (C) 1999 Elsevier Science B.V. All rights reserved.