Mixed-Mode I + II fracture characterization of bonded joints using a novel Multi-Mode Apparatus

Abstract

The present work presents the experimental test results to assess the toughness of an adhesive joint, using a previously defined crack equivalent data reduction scheme applied to a new multi-mode apparatus, inspired in a load jig previously developed by Fernlund and Spelt. The patented jig allows for easy alteration of the mode-mixity and permits covering the full range of mixed-mode I+II combinations. A data reduction scheme based on specimen compliance, beam theory and crack equivalent concept is used to overcome several difficulties inherent to the test analysis. The method assumes that the performed test can be viewed as a combination of the double cantilever beam and asymmetrically loaded endnotched flexure tests, which provide modes I and II fracture characterization, respectively. A numerical analysis including a cohesive mixed-mode I+II damage model was performed considering different mixed-mode loading conditions to validate the proposed data reduction scheme. Issues regarding self-similar crack growth and fracture process zone development are discussed. It was verified that the considered in-plane mix mode fracture criterion is well captured using the proposed data reduction scheme.