PSI - Issue 5

Shayan Eslami et al. / Procedia Structural Integrity 5 (2017) 1433–1438 Shayan Eslami et al./ Structural Integrity Procedia 00 (2017) 000 – 000

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Figure 4-Fatigue behavior of tested specimens

The most majority of the fabricated FSW joints had brittle behavior during the static test, consequently poor fatigue life was expected. However, the obtained joints showed to have a good fatigue life even with this brittle behavior of the weld nugget. Generally, main defect in polymeric FSW occurs on the retreating side of the welds [3]. The retreating side of the welds suffer from lack of generated heat when compared with the advancing side due to the low thermal conductivity of polymeric materials, leading to crack initiation at the retreating side.

4. Conclusion

In this study, the fatigue life of friction stir welded dissimilar polypropylene-to-polyethylene in lap shear configuration is presented and compared with the base materials. From the obtained results it is concluded:  The developed FSW tool produced strong welds between dissimilar polymers without using additional heating source;  In general, FSW polymeric materials proved to be a reliable method for joining polymers under static and cyclic stress condition;  Using high testing frequency, the PP specimens failed from the thermal failure and necking due to the high testing frequency;  The FSW joints failed brittaly from retreating side due to fatigue failure;  The failure occurred from retreating side of the welds for both static and fatigue tests.