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Effect of Surface Treatment and Tool Rotational Speed in Aluminum to Polymeric Composite Joint Produced Using Friction Stir/Adhesive Hybrid Process

Mohsenirad, Mahtab | 2021

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 54943 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Movahedi, Mojtaba
  7. Abstract:
  8. Today because of increasing use of fuel, environmental problems and problems due to heavy structures in different industries it is important to use structures with high specific strength. Using different materials in structures like polymers accompanying aluminum could be useful. Polymers are light, heat insulating and have a high corrosion resistance. Polypropylene is one of the useful polymers which can have high impact energy and strength via adding Elastomer and Talc powder, relatively. One of the common ways in joining metal to polymer uses adhesive. It has variety of benefits such as low distortion in joining, different materials joints and having joints with complex geometry. Welding is another way of joining which can have fewer surface pretreatments, shorter time and fewer chemical residues. Welding/adhesive hybrid joints can use all of the benefits of these joining processes. Here we study Al 5052/PP+10% Elastomer+20% Talc joints produced using friction stir welding in different rotational speeds from 300 to 1100 rpm. Also the effect of chemical surafce pretreatment with acid on aluminum and plasma on polymer on microstructure, adhesion and mechanical properties in conditions of with and without surface pretreatments and hybrid joints with both pretyreatments on metal and polymer were studied. Results showed that in all of rotational speeds in conditions of with and without surface pretreatment on aluminum, aluminum anchors were made in interface of base aluminum and stir zone that can be microscopic mechanical interlocks which can increase the joint strength. While the rotational speed is increasing the area of these anchors and height of injection in polymer reduced due to thermomechanical function of pin and these anchors changed their direction from inside of stir zone to outside of that. After surface treatment on aluminum surface, roughness of that increased and microscopic mechanical interlocks were made. Because of having more mechanical interlocks than aluminum anchors these interlocks were more important in joint strength and fracture force of joint increased and even doubled (in 700 rpm from 254 N to 694 N). In addition, plasma surface treatment on polymer increased wetting of adhesive on polymeric composite therefore adhesion strength of joint rose and could be more than double. In hybrid joints mechanical interlocks were made too and joint strength could be more than triple in condition of no surface treatments and fracture force of hybrid joint reached its highest in 700 rpm at 829 N
  9. Keywords:
  10. Aluminum ; Polypropylene ; Elastomers ; Talc ; Friction Stir Welding ; Adhesives ; Rotate Speed Tools ; Compound Metal-Polymer Bonding ; Plasma Surface Modification

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