Fatigue response of adhesive joints between additively manufactured substrates

This research study investigates on the influence of material manufacturing on the fatigue strength of adhesively bonded joints. Firstly, the effect of stress ratio and material manufacturing of aluminum Double Lap Joints (DLJs) in fatigue lap shear tests is discussed. The test samples are all bonded using the same new single-part epoxy whose characterization is still not available. A virtual model of the aluminum Double Lap Joint has been built, using commercially available finite element softwares like HYPERMESH and ABAQUS. The aim is to characterize the adhesive, in order to obtain a reliable model able to simulate real life mechanical behavior of a complex bonded joint configuration. Virtual results of the DLJ models are compared with the outcomes of the experimental testing. The main objective of this first part is to find a methodology for adhesive fatigue life prediction, starting from the DLJ virtual model and the results coming from experimental fatigue tests. For this purpose, the software nCode Design Life is used. Secondly, high cycle fatigue tests are conducted on two configurations of Single Lap Joints (SLJs). The substrates are made of 17-4 PH stainless steel. In the first configuration Additive Manufactured substrates have been bonded together using a commercially available two-part epoxy, while in the second configuration wrought substrates have been used. The main objective of this second part is to assess the influence of the different material manufacturing on fatigue strength. The fatigue tests are carried out at constant stress amplitude for two mean stresses. The effect of the mean stress is discussed.