Viscoelastic and viscoplastic stress analysis of adhesive joints

Abstract

The viscoelastic and viscoplatic effects in an adhesively bonded joint are very important to understand. Most of the adhesives used in structural applications exhibit some viscoelastic-viscoplastic behaviour, especially at high temperatures and high stress levels. The redistribution of stresses and strains that occur in joints during the viscoelastic-viscoplastic deformation influences the strength of the joints considerably. At low load levels a linear viscoelastic material model may be applicable, and at higher load levels both linear viscoelastic and non-linear viscoplastic material models are active at the same time. This paper presents results from the stress analysis of single lap joints, both with and without a crack, and with viscoelastic and viscoplastic adhesives. The influence of the stress redistribution on the failure load of the joint is discussed, as well as a ‘rule of thumb’ which can account for the viscous effects in the engineering design. The influence of flaws in the joints is also discussed.