Fatigue Crack Growth Behavior of Bonded Aluminum Joints

The current paper presents a research aiming at characterizing the fatigue behavior of adhesively bonded aluminum joints. In particular, Double Cantilever Beam (DCB) specimens and End Notch Flexure (ENF) specimens built using the 6061-T651 aluminum alloy substrate and the Araldite 2015 epoxy adhesive were used to evaluate the pure mode I and mode II fatigue crack propagation rates. Besides the fatigue crack growth rates the monotonic quasi-static fracture behaviors of the adhesive joints are also characterized for both loading conditions. Numerical finite element models of the joints are also proposed for the evaluation of the compliance calibration curves, avoiding the need of direct fatigue crack growth measurements, which is a very complex task mainly for the ENF tests. Critical fracture energies (GIc and GIIc) from experimental tests were in the same order of magnitude of the values published in the literature. Concerning the fatigue crack growth behavior, it was verified a higher fatigue crack growth resistance under pure mode II loading. A good agreement was found between the experimental fatigue crack growth data and the modified Paris law that accounts for fatigue crack propagation regimes I and II.