PSI - Issue 1

V. Anes et al. / Procedia Structural Integrity 1 (2016) 218–225

225

8

V. Anes et al. / Structural Integrity Procedia 00 (2016) 000–000

Fig. 12. Stress intensity factors I, II, and III of longitudinal cracks at doubler front end.

4. Conclusion

In this paper, the e ff ect of low temperatures in the corrosion strength of a bonded joint of two dissimilar materials was studied. The study started by determining the stress levels experienced by the joint for temperatures ranging from -50°C to 50°C. Next, it was determined the adhesives stress levels in the same temperature range, and finally, the stress intensity factors created by thermal stresses were estimated for longitudinal cracks usually found in the joint. It was concluded that for the most severe thermal loadings, the thermal stresses at doubler front end do not have the required amplitude to cause the joint damage, but the stress amplitudes reserved for drag forces is strongly reduced. The bonding strength of the EA-934 and EA-9394 adhesives was correlated with their stress levels experienced at the joint. The EA-9394 adhesive proved to have better mechanical performance, thus their use is advised in this type of joints. Moreover, the EA-934 have lower lap shear strength and experiences higher bonding stresses, which suggests a higher susceptibility to microcracks formation at very low temperatures, which may explain the contamination found in the corrosion spots.

Acknowledgements

The first author gratefully acknowledge financial support from FCT - Fundac¸a˜o para Cieˆncia e Tecnologia (Por tuguese Foundation for Science and Technology), for the Ph.D. Grant PD / BD / 52344 / 2013.

References

Achenbach, J., Thompson, D., 1991. Towards quantitative non-destructive evaluation of aging aircraft, in: Structural Integrity of Aging Airplanes. Springer, pp. 1–13. Bierwagen, G., Brown, R., Battocchi, D., Hayes, S., 2010. Active metal-based corrosion protective coating systems for aircraft requiring no chromate pretreatment. Progress in Organic Coatings 67, 195–208. Cina, B., 1974. Reducing the susceptibility of alloys, particularly aluminium alloys, to stress corrosion cracking. US Patent 3,856,584. DuQuesnay, D., Underhill, P., Britt, H., 2003. Fatigue crack growth from corrosion damage in 7075-t6511 aluminium alloy under aircraft loading. International Journal of Fatigue 25, 371–377. Liao, M., Renaud, G., Bellinger, N., 2007. Fatigue modeling for aircraft structures containing natural exfoliation corrosion. International Journal of Fatigue 29, 677–686. da Silva, L.F.M., 2011. Handbook of adhesion technology: with 97 tables. Springer Science & Business Media. Voevodin, N., Kurdziel, J., Mantz, R., 2006. Corrosion protection for aerospace aluminum alloys by modified self-assembled nanophase particle (msnap) sol–gel. Surface and Coatings Technology 201, 1080–1084.