Numerical analysis of adhesive shrinkage due to thermal cycling

Summary form only given. For bonded joints containing certain types of adhesives, residual stresses may become more tensile following exposure to cyclic temperature conditions. The more tensile state increases the likelihood of debonding. Significant shrinkage 15% or more of some adhesives has been observed following such debonding if the joint continues to be exposed to thermal cycles. The effect of thermal cycling on the stress state and deformation following debonding in such adhesive materials was investigated using finite element analysis. Viscoelastic materials were found to continue shrinking under cyclic thermal conditions when friction exists between adhesive and substrate. The work explored the effects of coefficient of friction, thermal cycling profile, and viscoelastic properties of the adhesive. Due to problems encountered in our attempts at 3D analyses, 2D geometries of two different types were investigated in this study. Fixed substrates were used in the first geometry type, but loss of contact between adhesive and substrate was seen. For the second case, the adherends were moved at the end of each thermal cycle to maintain contact between adhesive and substrate. The results of the numerical work indicate that viscoelasticity, constraints, and friction are the three requirements for the anomalous shrinkage of the adhesive under thermal cycling.