Stresses in Adhesive Joints Due To Moisture and Temperature

Abstract

This paper presents an analysis of the bonding stresses at the interface between an adhesive layer and an adherent when the exposed edges of the adhesive absorb moisture or when the joint is subjected to an elevated temperature. The analysis is based upon variational principles and is therefore approximate in nature. Nevertheless, the results provide a satisfactory explanation to the debonding phenomena that were observed at the center of the adhesive joint as well as near the exposed edges. It is shown that the maximal interlaminar tensile-stress can occur at either of the above sites and that the exact location of the maximal stress depends on the geometry of the joint and on the progress of moisture-diffusion. It is also shown that the interlaminar shear-stress does not vanish at the point where the interface between adhesive and adherent intersects the free-edge. This is consistent with the exact solution that contains a corner- singularity at that point and contradicts several calculations which arbitrarily omitted this singularity.