Damage and plasticity of adhesive layers: An experimental study

AbstractTime independent inelasticity is often modelled as due to plasticity and/or damage. The difference is manifested at reversed loading; plasticity reveals itself by a remaining strain in the unloaded state while damage is revealed by a decrease in the elastic stiffness during unloading. With thin adhesive layers, the deformation is inhomogeneously distributed along the layer. Large deformations occur at the ends of the layer. In the more central parts, the layer is virtually undeformed. This makes a direct measurement of the unloading properties virtually impossible. In the present paper, novel experiments are performed in order to evaluate the inelastic properties of epoxy adhesives. The load is first increased to a level corresponding to 50, 60, 70 or 80% of the fracture energy. The load is then reversed. The first step creates a zone of inelastically deformed adhesive at the start of the layer. During a final loading phase, the properties of this zone are analysed. Major differences due to the loading direction are observed. Some comparisons with simulation models are performed