Residual stresses in symmetric double lap and double strap joints

Abstract

This work presents a one-dimensional analysis of the bonding stresses at the interfaces between the adhesive bond lines and the adherents for both the symmetric, double lap and double strap joints, due to several typical moisture profiles distributed along the adhesive material. The analysis considers linear elastic behavior and presupposes the forms of kinematic fields. The formulation then follows variational principles and the interlaminar stresses are evaluated as Lagrange multipliers which are incorporated into the internal energy. Based on the derivation of linear elastic residual stresses, linear viscoelastic solutions are also obtained by Direct Method. The finite element method (FEM) is adopted to yield numerical predictions in comparison with the linear elastic and viscoelastic solutions. The stresses along the normalized length, the x-axis. are very close for 0 ⩽ x ⩽ 0.7; for 0.7 <x ⩽ 1 both linear elastic and viscoelastie solutions are very close and the FEM solution reaches singularity at the free edge due to the so-called edge effect. In addition, the theoretical and numerical results all indicate that the most detrimental stresses arise at the free edges during moisture desorption.