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Joining of Aluminum to Polymeric Composite Using Friction Stir-Adhesive Hybrid Process

Shiravi Khozani, Hossein Ali | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52640 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Movahedi, Mojtaba
  7. Abstract:
  8. Nowadays, metal-polymer dissimilar joints have attracted the attention of many industries, and the aplication of these joints in various industries such as automotive and aerospace is increasing. However, due to considerable differences in physical properties of metals and polymers, proper bonding between these materials is not easily possible, and metal-polymer joining remains one of the major challenges in the development of advanced composite structures. The adhesive/friction stir joining hybrid process is a relatively new idea that has been proposed to achieve longer lasting bonds and more safe structures. Using this process for metal-polymer joining can take advantage of both methods; namely the higher strength, preventation of the polymer melt from leaving the joint, better joint appearance, and sealing the joint by removing the gap between overlapped sheets simultaneously. In this study, joining of Al5052 alloy aluminum alloy to polypropylene polymer (PP) and PP-20% Talc polymer matrix composite by friction stir welding and the feasibility of using hybrid adhesive/friction stir joining process to improve the properties of this joint was investigated. Studies included determining the effect of pin geometry (cylindrical, threaded tapered pin, triangular, and triflute) on the appearance and profile of the joint and effect of tool transition speed (at three levels of 50, 100 and 150 mm/min) and the chemical composition of the polymer (PP And PP-20% Talc) on the microstructure and mechanical properties of the joints. Results showed that the best joint appearance and the highest load bearing capacity is obtained by triangular pin. In the microscopic images, an interaction layer was observed at the aluminum/stir zone interface. The adhesion of this layer to aluminum and polymer resulted in improved joint quality and strength. The addition of talcum powder to polypropylene resulted in improved tensile properties of the joint due to the decrease in the shrinkage of the solidified polymer as well as the increase in adhesion and strength of the interaction layer. Increasing tool transition speed from 50 mm/min to 100 mm/min resulted in increase of the size of aluminum anchors inside the polymer. Also, due to lower heat input to the weld area, the amount of thermal shrinkage decreased, and the adhesion of the interaction layer to the stir zone polymer increased. But further increasing tool transition speed (up to 150 mm/min), cavities were formed in the aluminum/stir zone interface, and although the size of aluminum anchors increases, the overall joint strength decreases. The shear tensile test results showed that the tool transition speed of 100 mm/min resulted in the highest peak load at both Al/PP and Al/PP-20%Talc with values of 284 N and 315 N, respectively. The joints fractured from the Al/stir zone interface. An acrylic-based adhesive, 2ONE, and a methacrylic-based adhesive, Permabond TA4610, were used in hybrid adhesive bonding/friction stir joining process. Investigation of the hybrid joints showed that only when the adhesion of the adhesive to both base sheets is good, the adhesive can increase the peak load of the hybrid joint (up to 330 N). Otherwise, the use of adhesive reduces the load bearing capacity of the joint
  9. Keywords:
  10. Dissimilar Joint ; Friction Stir Welding ; Polypropylene ; Adhesives ; Aluminum Alloy 5052 ; Compound Metal-Polymer Bonding ; Talc

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