Development of experimental methods in the fields of non-linear fracture mechanics, investigating adhesive joints subjected to mixed-mode loading

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Adhesive bonding represents an established joining technology these days. Beside requirements regarding stiffness or damping properties, the fracture behaviour of adhesive joint subjected to mechanical loading is of prime interest. As example, the realistic prediction of joint failure is one of the most important criteria in automotive crash applications.Experimental characterization of joint failure is done in fracture mechanical tests. The achieved results are used to formulate appropriate models including corresponding parameters, while the particular loading conditions have a huge influence on the observed fracture behaviour. Combined peel and shear loading is called mixed-mode loading, and methods of linear-elastic fracture mechanics are an established approach for experimental characterization. Those methods cannot be applied without limitations to adhesive joints, which consist of adhesives showing nonlinear material behaviour.Within the framework of a finished research project, a novel test setup and two novel evaluation methods have been developed, which do not underlie limitations of linear-elastic fracture mechanics and therefore can be applied to non-linear joint behaviour. The essential novelty is a possible separation of J-integral into its contributions to the single fracture modes. A further major novelty is test control on those contributions or on total J-integral, which allows identification of traction at the crack tip.The main goal is to generate deeper understanding and further development of the proposed methods. This is achieved by experimental and by numerical investigations on two different kinds of adhesives to emphasize the influence of material behaviour on test results. In addition, the focus is extended to a novel test setup, on which the novel methods are applied. The second test setup generates information on another type of mixed-mode loading