Fracture testing of adhesive joints in mixed-mode I plus III

The Mixed-Mode Controlled Double Cantilever Beam (MC-DCB) test has been developed to test samples under mixed-mode loading in a combination of mode I and mode III. The mixed-mode ratio is defined based on J-integral and the principle of superimposition holds even in the case of nonlinear fracture behavior. This mixed-mode ratio is externally controlled to be constant during the entire test duration by realizing the MC-DCB test setup as a dual-actuator test in a biaxial testing machine. In this work, test results at constant mode-mixity on two different kinds of adhesive joints are presented: elastic-plastic adhesive joints made of SikaPower (R)-498 and rather brittle adhesive joints made of Henkel Teroson (R) EP4510GB. These recently achieved test results give more detailed information on the fracture behavior of the particular adhesive joints. With regard to cohesive zone modelling of possible joint failure, the traction-separation behavior at the initial crack tip has been evaluated by considering the crack-tip opening displacement, which has been measured by digital image correlation in the experiments. (c) 2022 The Authors. Published by Elsevier B.V.