Investigation of Dissimilar Friction Stir Welding of Metals and Polymers

Abstract

Friction stir lap welding has emerged as a promising technique for joining dissimilar materials, particularly metal-polymer combinations such as AA5052 and polypropylene (PP). This study aimed to investigate the impact of FSW tool design and welding parameters on joint quality, specifically for the metal-on-top lap joint configuration. A comprehensive experimental study was conducted to identify the most important process parameters, and then investigate their effect on joint quality. The study employed ANOVA, chemical, and microstructure analyses to examine the feasibility of welding the novel hybrid structure of AA5052 and PP. TGA, EDS, and Raman were used to understand chemical bonding. In addition, digital microscopes and SEM are used to inspect the mechanical interlocking. It was found that a tapered fluted pin made from a self-tapping screw with a flat rotating shoulder effectively penetrated the aluminum and initiated mixing to create a strong lap joint. The optimal process parameters for the dissimilar joint were determined to be at a rotational speed of 1400 RPM and a traverse speed of 20 mm, resulting in a load of 336 N and a lap tensile strength of 3.8 MPa. The study concluded that traverse speed is the most influential variable as it significantly affects all the studied factors. Also, mechanical interlocking proved to be more prominent to joint strength than chemical bonding. The research project aimed to provide a deeper understanding and more detailed knowledge of the dissimilar joining of AA5052 with PP sheets, with a particular focus on the effect of tool design on weld quality.

Overall, this research provided valuable insights into the application of FSW for joining metal-polymer materials and demonstrated the potential of this technique for producing high-quality, strong joints in dissimilar materials. Further research could explore different tool designs and welding parameters to optimize the process and improve joint strength and quality.

Date of Award	Apr 2023
Original language	American English
Supervisor	Fahad Almaskari (Supervisor)