Modelling of Single-Lap Joints Using Cohesive Zone Models: Effect of the Cohesive Parameters on the Output of the Simulations

Abstract

The available techniques for strength prediction of bonded joints have improved over the years. Cohesive zone models (CZM) coupled to finite element method (FEM) analyses surpass the limitations of stress/strain and fracture criteria, and simulate damage growth. CZMs require the instantaneous energy release rates in tension (G _n) and shear (G _s) along the fracture paths and respective fracture energies in tension (G _n ^c) and shear (G _s ^c), and crack growth is ruled by traction-separation laws that are established at the failure paths. Additionally, the cohesive strengths must be defined (t _n ⁰ for tension and t _s ⁰ for shear) relating to the onset of damage. A few techniques are available for the estimation of these parameters (e.g., the property identification technique, the direct method and the inverse method) that differ in complexity and expected accuracy of the results. In this work, the influence of the cohesive law parameters of a triangular CZM used to model a thin adhesive layer in bonded joints is studied, to estimate their effect on the predictions. Some conclusions were established to provide important data for the proper selection of the estimation technique and expected accuracy of the simulation results.

KEYWORDS:

• Bonded joints
• Cohesive zone models
• Finite element method
• Structural adhesive

Notes

Presented in part at the 1st International Conference on Structural Adhesive Bonding (AB2011), Porto, Portugal, 7–8 July 2011.