The effect of heat-moisture aging on elastic-deformation properties and the type of failure of adhesive joints in testing for cracking resistance

Results of testing of two groups of film adhesives that differ in their chemical natures, service temperatures, and elastic-deformation characteristics, such as VK-3, VK-50, and VK-26M phenolic rubber adhesives and high-strength VK-51A epoxy adhesive, are reported. The locus of failure of adhesive joints after wedge tests in the initial state and after heat-moisture aging is studied using a scanning electron microscope. It is revealed that, as result of heat-moisture aging, the locus of failure of adhesive joints changes for VK-51A (with and without EP-0234 primer) and VK-3 adhesives, whereas it remains unchanged for VK-50 (with EP-0234 primer) and VK-26M adhesives.