PSI - Issue 39

M.A. Sánchez Miranda et al. / Procedia Structural Integrity 39 (2022) 161–172 Author name / Structural Integrity Procedia 00 (2019) 000–000

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and 11, where ABS (dark zone), correspond to retracting side.

Figure 10. SEM images for specimen 13 in Table 3: PP side (a), and ABS side (b).

Figure 11. SEM images for specimen 14 in Table 3: PP side (a), and ABS side (b).

Uniform mixture of ABS-PP is a main issue for the performance of this dissimilar joining; Figures 10 and 11 show a predominant PP in the advance side and a predominant ABS in retracting side. Better mixture is observed for the advanced side, where the lowest density of PP compared to ABS induces high superficial presence of PP [ 29 ] . No chemical bonding seems developed between these two thermoplastic polymers after the FSW process; rather interface mechanical bonding develops between the random particles of these two polymers, across the stir zone [ 30 ] . Molecular diffusion in liquid state seems to be the main mechanisms of polymers bonding under FSW. A reference model to assess this phenomenon has been developed [ 31 ] ; for the case of dissimilar polymeric FSW joining, the width of the advancing and retreating extrusion zones is determined by the process parameters (rotation speed and advanced speed, pin and shoulder geometry and dimensions), and by the rheology of the two dissimilar polymers. Four zones of mass flow are proposed in the initial deformation stage, in this model : M I for the advancing side, M II for retreating side, M III for the shoulder side and M IV for the pin bottom side, Figure 12.