On the interfacial constitutive laws of mixed mode fracture with various adhesive thicknesses

Interfacial toughness and interfacial strength, as two critical parameters in an interfacial traction–separation law, have important effect on the fracture behaviors of adhesively bonded joints. In this work, the global and local fracture tests are employed to investigate the effect of adhesive thickness on interfacial energy release rate, interfacial strength, and shapes of the interfacial traction–separation laws under the mixed I/II mode loading condition. Basically, the measured interface laws based on the single leg bending (SLB) specimens reflect the equivalent and lumped interfacial fracture behaviors which include the cohesive fracture, damage and plasticity. Several new and interesting experimental results were obtained. The experimentally determined interfacial traction–separation laws may provide valuable baseline data for the parameter calibrations in numerical models. The current experimental results may also facilitate the understanding of adhesive thickness-dependent interface fracture of bonded SLB joints.

► It is proved that the peel mode and shear mode can be decoupled in single leg bending (SLB) specimen.
► Global-local fracture test is conducted.
► Cohesive laws are determined.
► Effect of adhesive thickness on the mixed mode fracture is evaluated.