Optimal Parameters for Joining Polymer and Aluminum with an Adhesive Layer Using Friction Stir Welding in Aerospace Industry

Paying attention to the increasing use of metal-polymer composites in aerial and space structures and their economic efficiency, it is possible to achieve a more economical and high-quality connection by determining the appropriate parameters. The purpose of this article is to calculate the optimal parameters for the friction stir welding (FSW) process to properly join aluminum to polymer. Polycarbonate sheets and aluminum alloy sheets, widely used materials in the aerospace industry, were employed for FSW. Initially, a traditional FSW was conducted without additional material. Subsequently, for two samples, a layer of epoxy glue was placed between the two sheets, followed by FSW. On the second sample, a restorative FSW was performed with a 10 mm comb stirrer head. The results indicated that the most optimal condition was a spindle speed of 1400 r/min and a welding speed of 50 mm/min, particularly for the sample with epoxy glue and repair welding. Traditional FSW showed flaws, while FSW with adhesive displayed fewer defects. Repair welding significantly influenced the FSW joint, enhancing the cleanliness of the macroscopic appearance of the weld surface. In the tensile test, it was observed that the tensile strength of the repair weld exceeded that of the joint welded by two traditional methods and with glue. Microscopic results revealed more holes in FSW with two traditional methods and with glue, gradually reducing defects during repair welding.