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Refilled Friction Stir Spot Joining of Aluminum to Polymer Sheets

Karami Pabandi, Hossein | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48813 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Kokabi, Amir Hossein; Movahedi, Mojtaba
  7. Abstract:
  8. Today, dissimilar joining of metal to polymer is in increasing demand in automotive and aerospace industries. Conventional methods for dissimilar joining of metal to polymer have limitations such as need for complex system and high surface sensitivity. Therefore, in this study, it has been tried to join pre-drilled aluminum sheets to polymer, based on frictional heat and creation of interlocks between the base parts. Refilling the hole is the main advantage of the method. AA5052 sheet with 2 mm thickness and polypropylene reinforced with 3 wt% short-carbon-fiber composite were used as primary materials. The effect of hole diameter in 4 and 5.5 mm and tool rotational speed in 500, 1000, 1500 and 2000 rpm were investigated on the joint properties. Shear-tensile, cross-tension and hardness tests, differential scanning calorimetery (DSC), temperature measurement and scanning electron and optical microscopes were used for characterization of the joints. The results showed that the presence of initial hole on the aluminum sheet had a significant impact on the joint strength. While the maximum fracture load in the sample joined with 2000 rpm and without hole was 81±20 N, the fracture load of 443±62 N was achieved by formation of interlocks between aluminum and Polymer sheets inside the hole with diameter of 5.5 mm at the same rotational speed. At the joint interface, a reaction layer containing of 21 to 38 wt.% Al with the thickness of 12 to 16 μm was formed between aluminum and re-solidified polymer. The results of hardness test and DSC analysis showed that the hardness and crystallinity of the re-solidified polymer decreased with increase of tool rotational speed
  9. Keywords:
  10. Dissimilar Joint ; Polypropylene ; Friction Stir Spot Welding ; Aluminum Alloy 5052 ; Refilling Hole ; Ratchet ; Short Carbon Fiber

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