Multi-Scale Characterization of an Adhesive Bondline with Fabrication Induced Defects

Abstract

A multiscale characterization of an adhesive bondline is performed to investigate the fabrication defects dependent failure mechanisms of an I-beam under four point bending. To obtain a realistic representative volume of the bondline at its microscopic level, a 3D all-hexahedral mesh generator is used to create the unit cell model, which is capable of considering multiple material domains. The unit cell model contains the geometric information of glass beads, matrix of adhesive material and voids that are based on their micro-structural descriptions from the sectional 2D X-ray scanned images. The adhesive layer is modeled by cohesive interaction in the macro- beam model. The cohesive properties at the macroscopic level are extracted based on the average stress displacement curve to reserve the equivalent energy dissipation. Using the fabrication defects dependent cohesive properties, the numerical simulation predicts a local-buckling driven failure, which is consistent with the static test observation. Based on the shear dominant bondline failure pattern observed under the fatigue test, a parametric study of cohesive properties is performed to investigate the root cause of shear failure under fatigue which is different from the failure mode under the static test.