Damage evolution model for bonded and clamped interfaces under cyclic shear loading

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School of Engineering | Master's thesis
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68 s. + liitt. 13
The focus of this thesis is to develop a Paris law type model for predicting the life of a bonded and clamped (hybrid) interface. A toughened epoxy adhesive (3M DP490) is used, with high strength steel as substrate. Napkin ring type specimens machined from high strength steel are used for the experiments. Bonded and non-bonded quasi-static tests are performed on the hybrid interface at 4, 50 and 100 MPa clamping forces to understand the interaction of friction and the adhesive. A bilinear traction separation law is used to approximately represent the quasi-static response of the hybrid interface. Data from the low cycle fatigue tests carried out at 4, 50 and 100 MPa clamping forces is used for the development of the model. Fatigue limits of the joint at the aforementioned clamping forces are found by performing high cycle fatigue tests. These results are then compared to results from a non-toughened epoxy (3M DP760). Results from the model imply that it is fairly accurate in predicting the lives of most of the low cycle fatigue specimens. It was also found that the toughened epoxy (3M DP490) is not better in cyclic loading than the non-toughened epoxy (3M DP760). The interaction of friction and adhesive at the hybrid interface is something that could not be studied due to time constraints and should be a subject for future investigations. The effect of frequency on the behaviour of the hybrid interface during a fatigue test is also a subject for future investigations.
Marquis, Gary
Thesis advisor
Hurme, Susanna
cohensive zone model, traction separation law, toughened epoxy, power law, damage mechanics
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