Innovative Production Method of Metal–Polymer Composite Panels by Friction Stir Joining

Overlap joining is one of the most adopted configurations to combine metals and polymers, mostly due to technological limitations of mechanical fastening, conventional welding, and adhesive bonding. Nonetheless, the misalignment of the neutral lines between base materials leads to the development of secondary bending moment that generates a bending stress component, limiting the admissible load. This work investigates the feasibility of friction stir joining AA6082‐T6 aluminum alloy and a glass fiber–reinforced polymer (Noryl GFN2) in buttstrap configuration, aimed at mitigating secondary bending effects. Exploratory trials were performed to simultaneously weld two aluminum plates that overlap a third polymeric plate, varying travel and rotational speeds while maintaining constant vertical position and tilt angle. Nine buttstrap joints were successfully produced, achieving ultimate tensile strengths between 80.3 and 138.9 MPa, corresponding to joints’ efficiencies ranging from 27.7 and 47.9% of the aluminum alloy's strength. The microstructural analysis unveiled that all joints exhibited an interfacial defect among the three plates with characteristics of i) unwelded root defect, typically observed in butt joints, and ii) hook‐shaped defects, mainly associated with overlap joints. The size of the defect significantly affected the effective joining thickness between aluminum plates and, consequently, the associated mechanical performance.