Static assessment of the mixed-mode behaviour of three epoxy adhesives

Abstract The present work aims to obtain the full fracture envelopes of three different adhesives used in the automotive industry by determining the fracture energy in in mode I, mode II and various mixed-mode combinations. Double Cantilever Beam (DCB) and End-Notched Flexure (ENF) tests were performed to assess mode I and mode II fracture behaviour, while for mixed-mode analysis a versatile apparatus was used to perform a wide range of combinations from mode I to mode II. The innovative technique allows for separate determination of mode I and mode II contributions, while classical mixed-mode approaches only allow for the total to be determined. The results reveal the adequacy of the mixed-mode apparatus, presenting consistent values for the fracture energies in every mixed-mode combination studied. The fracture envelopes follow a quadratic criterion for the studied adhesives, and the results are consistent with other literature works.