On the influence of the mechanical characteristics of a thin adhesion layer on the composite strength. Part 2. Elastic-plastic deformation

The limiting state of a thin adhesive layer at its normal rupture in the plane stressed and plane deformed states is considered. The behavior of the layer is described by an ideal elastoplastic model with the Tresca - Saint-Venant yield condition. The deformation of the layer is carried out by means of consoles operating within the framework of the relations of the Mindlin - Reissner plate theory. In the area of plastic flow of the adhesive layer, the condition of complete plasticity is assumed. The presence of several diagonal components of the stress tensor in the layer, which are related to the cantilever stresses by the equilibrium conditions, is taken into account. On the basis of the problem posed, analytical representations are obtained for the displacement field of cantilevers in the region of conjugation with the layer. On the basis of experimental data on the destruction of adhesive layers with given mechanical properties, the critical values of J-integrals are found depending on the type of the considered plane problem for the layer. It is shown that a decrease in the thickness of the adhesive layer leads to an unlimited growth of deformations in its end zone, however, the values of the J-integrals stabilize. In this case, in the case of a plane deformed state, the length of the plastic zone decreases and the main contribution to the J-integral is made by the energy component. In a plane stressed state, the length of the plastic zone increases, and the dissipative component of the J-integral exceeds the energy one. A significant difference in the critical values of the J-integral is obtained, which is a consequence of the developed plasticity zone in the plane stress state. For plane deformation in extremely thin adhesive layers, taking into account their elastoplastic properties is insignificant and the values of the J-integral can be found within the framework of a linearly elastic model of adhesive behavior or in a model with rigid coupling of mating bodies, which excludes the mechanical properties of the adhesive from consideration.