Characterization of Friction Stir-Welded Polylactic Acid/Aluminum Composite Primed through Fused Filament Fabrication

There are many possible reasons for low weld strength in FSW of thermoplastic; low thermal conductivity, high energy losses in friction stir welding (FSW), material spill-out, involvement of high mechanical forces, etc. To counter strike the above-mentioned issues which weaken the joint's strengths, two strategies have been approached. The first approach is based upon the preparation of aluminum (Al) layers-reinforced Polylactic acid (PLA)/Al composite material which must have high thermal conductivity and crystallinity for improved heat generation in FSW. In the second approach, the FSW has been performed using a semi-consumable pin of similar materials which can compensate for the materials loss and void formation during FSW. Alternating layer composite of (PLA)/Al was manufactured by modified fused filament fabrication (FFF) 3D printing process then welded by FSW process in next steps. In this study, the FSW process was performed by using a semi-consumable pin profile of PLA with varying tool rotation speed (TRS) (800, 1100, and 1400rpm), depth of semi-consumable pin (SPD) (2, 3 and 4 mm), and transverse speed (TVS) (20, 30 and 40mm/min). FSW joints were subjected to mechanical (tensile strength, percentage elongation, and modulus of toughness), morphological (fracture by scanning electron microscopy and surface profiling), structural (Fourier-transform infrared spectroscopy, x-ray diffraction) for optimizing the FSW process parameters. Analytic hierarchy process and genetic algorithm are implemented to acquire a single set of parameters which would result in the best value of tensile properties. The suggested levels are 1400 rpm, 2 mm, and 31.79 mm/min. of TRS, SPD, and TVS, respectively.

Automated summary

Two strategies are used to address the issue of low weld strength in friction stir welding (FSW) of thermoplastic materials: preparing aluminum-reinforced composite materials with high thermal conductivity and crystallinity, and using semi-consumable pins during FSW to compensate for material loss and void formation. Through systematic experimentation and analysis, the optimal FSW parameters were identified.