Characterization and modelling of the 3D elastic-plastic behaviour of an adhesively bonded joint under monotonic tension/compression-shear loads: influence of three cure cycles
Résumé
Characterization and modelling of the 3D elastic-plastic behaviour of ductile adhesive materials are all but straightforward. Advanced models and significant experimental work are required in order to achieve good accuracy over a wide range of different loading conditions combining tension or compression with shear. Indeed, advanced constitutive laws taking into account hydrostatic stress dependency and non-associated formalism have to be defined. As a consequence, the experimental characterization of an adhesive within a bonded assembly has to include different load combinations. In this study, a modified Arcan specimen is used to obtain a large experimental data base covering tension, tension-shear, shear and compression-shear results for a bi-component epoxy-based adhesive (Huntsman™ Araldite 420 A/B). Three different bonding conditions are considered; the curing temperature (50 or 110 °C) and aged time at the test (within a week or after a 6 months storage at room temperature) being the two parameters investigated. A simplified inverse identification method based on these results is proposed for the identification of a 3D elastic-plastic model proposed by Mahnken and Schlimmer. In particular, the number of identification steps involving coupled finite element analysis and optimization software is considerably reduced. The comparison between the predicted and experimental results demonstrates the good capabilities of the model and underlines its limitations considering the flow rule definition in a specific case. Results show that both the curing temperature and the aged time have a substantial influence on the yield surface and final strength of the adhesive whereas the hardening curve seems less affected. Some possible improvements in the modelling of the adhesive under monotonic proportional loads are proposed as a conclusion.