P 957 - Experimental determination of characteristic values and simulation of structural adhesive bonds with elastoplastic and fracture-mechanical cohesive elements

A prerequisite for the use of these elements is the experimental characterisation of the adhesives. For this reason, both continuum mechanics and fracture mechanics investigations were carried out as part of this project. In addition to the creation of additional material cards, the aim of the present investigations was to check whether the basic experiments can be transferred to other types of adhesives and whether they can be applied to other adhesive layer thicknesses. To this end, the test concepts already known from the previous projects were initially used to analyse the adhesive layers under uniaxial loading. The thick shear tensile test and the head tensile test were used to determine the continuum mechanical parameters, while the tapered double cantilever beam test and variations of the end-notched flexure test were used for the fracture mechanical parameters. The butt-bonded double tube specimen was used to investigate the continuum mechanical behaviour of bonded layers under multiaxial loads. To investigate the fracture mechanical behaviour in mixed mode, an experiment was set up in which the mode ratio is controlled during the test. Three different adhesives with up to three adhesive layer thicknesses and three slip rates were investigated. The adhesive layer replacement modelling of tough modified bonded joints based on fracture mechanics and plasticity theory with damage enables a descriptive replacement modelling to capture adhesive layer thickness-dependent effects, which manifest themselves macroscopically in increased or reduced dissipation. An elastoviscoplastic interface model can be used for the numerically efficient representation of the macroscopic adhesive layer behaviour under quasi-static and dynamic (crash-like) loading. In addition to parameter identification and verification on basic tests, the adhesive layer replacement model is validated on samples with homogeneous and inhomogeneous stress states. The T-joint is used as a component-like validation sample to demonstrate the accuracy of the model under practical loading.