PSI - Issue 47

Mario A. Sánchez Miranda et al. / Procedia Structural Integrity 47 (2023) 310–324 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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In Figure 4 is shown the machine used for the FSW process; this machine comprises: the lathe axis with the rotating tool, the circular bearing exceeding the aluminium plate, the aluminium plate, the rotating pin and the two thermoplastics fixed and aligned (butting disposition).

Tool

Bearing

Aluminium plate

Pin

Thermoplastics

Figure 4. Experimental set up for FSW of two thermoplastics: UHMWPE and PP.

In Figure 4, the aluminium plate is lightly in contact with the polymers during the FSW process. First results reveal no significant material expulsion from the welding bed, caused by pin tool friction stir. A first rough estimation leads to 96% of the thermoplastics remains within the weld bead, retained by the aluminium plate that works as a stationary shoulder. The first results to joint these two polymers were obtained using a moving shoulder, which yielded discontinuities, poor mixing and poor mechanical properties, Figure 5a. The use of stationary shoulder has noticeably increased the performance of FSW, as illustrated in Figure 5b. The use of stationary shoulder (or shoulders), has been investigated previously [33]; the results in joining dissimilar thermoplastics leads to superior surface quality, low variation of applied load during welding which induces reduction of discontinuities and improvement of mechanical properties; as the case of Teflon thermoplastic used as stationary shoulder [34].

Figure 5. a) FSW with rotating shoulder. b) FSW with aluminium plate as stationary shoulder.