Fracture energy characterisation of a structured interface by means of a novel J-Integral procedure

Abstract

In the present investigation, a J-Integral formulation for non-flat crack paths, in the framework of the cohesive zone model, is developed. The formulation allows fracture energy properties in a direction that is not necessarily coplanar with the global crack advance to be analysed. Specifically, the effective fracture energy, ${\overline{J}}_c^x$ , has been examined based on the horizontal projection of the crack advance, $a_x$ (also called effective crack length). The use of $a_x$ is convenient in several situations as the case of patterned interfaces in adhesive joints. Finite-element analysis of double cantilever beam specimens including a trapezoidal patterned interface were employed to check the accuracy of this new definition of the contour integral. Post-process of the finite-element model, including those variables involved in the fracture energy calculation, is discussed together with some considerations that distinguish the energy evaluation procedure for flat profiles from structured designs. Finally, ${\overline{J}}_c^x$ values obtained using the modified J-Integral formulation are compared with $G_c^x$ values obtained from the load–displacement curve method for comparison purposes.