The Viscoelastic Shear Behavior of a Structural Adhesive

Erol Sancaktar, The University of Akron

Abstract

The increased use of adhesives in the automobile, aerospace and other industries is noted. The need to understand the viscoelastic nature of polymeric adhesives is assessed. Previous bulk tensile constant strain-rate, creep, relaxation, and delayed failures studies on an epoxy adhesive are summarized. New constant strain-rate and creep data for symmetric rail shear and symmetric lap shear geometries of the same epoxy adhesive are reported. It is shown that significant viscoelastic shear behavior, including delayed failures, do occur. The linear viscoelastic methods and results from previous tensile studies are extended to the condition of shear. Predictions are shown to be at variance with experimental results. The reasons for deviations are discussed; i.e., the possibility that linear viscoelastic analytical procedures are inappropriate and the likelihood that viscoelastic phenomena are different in bulk tensile, bulk shear and lap shear geometries