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.