To Failure of Adhesive Layers Under Mixed Mode I+II Loading

An energy criterion for the failure of a thin adhesive layer of finite thickness under mixed mode I+II loading and regular distribution of the stress field in the layer was proposed. The thickness of the adhesive layer was considered as a linear parameter. The criterion takes into account the influence of invariant terms forming the elastic energy density in the end zone of the crack-like defect. In this case, the energy of volume change at positive hydrostatic pressure participates in the loosening of the adhesive and reduces the strength, while negative hydrostatic pressure increases the load-bearing capacity of the material. The product of the linear parameter and elastic energy density in the end zone of a crack-like defect determines the J-integral, which converges to the J-integral for a Griffith’s crack when the linear parameter aspires to zero. The computational convergence of the product of invariant terms of elastic energy density and linear parameter within the framework of numerical solution of the problem by the finite element method under critical external load is investigated. Based on the found invariant energy products and critical values of J-integrals for loading modes I, II, I+II the constants of the criterion proposed for a number of adhesives were determined. A comparison of the calculated critical external critical load for the mixed mode loading with the known results has been carried out.