A Study of the Friction Stir Lap Welding of AA5052 and Polypropylene

Abstract

Friction stir lap welding (FSLW) remains a pioneering technique for creating hybrid joints between AA5052 aluminium alloy and polypropylene (PP), particularly with the metal-on-top configuration. Building upon previous research, this study introduces a tapered fluted pin tool design and investigates its effectiveness in the welding process. Our results, supported by ANOVA, chemical, and microstructural analyses, reiterate that the optimal welding parameters stand at a rotational speed of 1400 RPM and a traverse speed of 20 mm/min. This combination produces a joint tensile strength of 3.8 MPa, signifying 16.54% of the weaker material’s inherent strength. Microstructural evaluations revealed a unique composite of aluminium chips intermeshed with PP, strengthened further by aluminium hooks. Crucially, mechanical interlocking plays a predominant role over chemical bonding in achieving this joint strength. The study underscores the absence of significant C-O-Al bonds, hinting at the PP degradation without the thermo-oxidation process. Additionally, joint strength was found to inversely correlate with the interaction layer’s thickness. The findings fortify the promise of FSLW with the novel fluted pin design for enhancing joints between AA5052 and PP, emphasising the potential of mechanical interlocking as a principal factor in achieving high-quality welds.

Feasibility study of friction stir joining of aluminium with carbon fibre reinforced thermoplastic composite

“…14 Usually hybrid joints generated by FSW are either characterized by a flat interface between both materials 15 or extensive mixing of both materials. 16 FSW can also be applied if the upper aluminium sheet was pre-processed to have through-holes adjacent to the seam. In this case, driven by axial tool and clamping pressure, the molten thermoplastic flows into the holes and reconsolidates, forming macro mechanical interlocking.…”