INFLUENCE OF WATER ON STRESS CORROSION CRACKING OF EPOXY BONDS

Environment assisted fracturing, or stress corrosion cracking of adhesive joints in liquid water or a humid atmosphere was shown to occur at values of applied crack extension force ςa considerably below those required for onset of opening‐mode rapid fracture ςc. The minimum value of ςa below which no cracking was observed, ςSSC, was dependent on the relative humidity and the particular adhesive used. For two adhesive systems, the one with the lower hardener content and post cure temperature showed both a lower absolute value of ςSSC and a lower ratio of ςSSC to ςc. The value of ςSSC for both adhesive systems decreased as the humidity was increased. As the relative humidity approached 100%, the value of ςSSC approached its value for liquid water. Values of ςc for the two adhesives differed by a ratio of approximately 2:1. When water was introduced to the crack tip, ςc for the less tough material increased while it was not significantly changed for the tougher material. Copyright © 1969 John Wiley & Sons, Inc.