The Effect of Pin Design on the Mechanical Behavior of Polypropylene-Polypropylene Joining through Friction Stir Welding

Document Type : Research Paper

Authors

1 Department of Material Science and Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran

2 Department of Material Science and Engineering, Faculty of Engineering, University of Zanjan, Zanjan, Iran.

10.22063/jipst.2025.35618.2360

Abstract

Hypothesis: Today, the friction stir welding (FSW) is known as a safe method for joining two parts especially thermoplastic polymers. One of the most effective parameters is designing the pin for creation of joint. In this research,  the effect of pin shape was investigated on the FSW of polypropylene (PP)\polypropylene
Methods: To do so, the pins were designed with different geometries: conical threaded cylinder, and threaded. After welding the PP-PP plates by designed pins the tensile, flexural, impact and hardness tests were performed to investigate the mechanical behavior of created joints. Also, scanning electron microscopy was used for microstructure study
Findings: The tensile strength of the sample joined with the threaded cylindrical pin was 18.6 MPa, which had the highest tensile strength efficiency of weld (approximately 82%) as compared with other samples. Also, the weld fracture toughness of this sample under tensile test was 1862.6 mJ/mm3, which was an efficiency of approximately 51%. The values of flexural strength and fracture toughness in bending test of threaded sample were 75 and 60%, respectively. The welded sample with the threaded cylinder had the highest absorbed energy (533 kJ/m3), which was about 39% and 25% higher than values of the conical (383 kJ/m3) and threaded conical (425 kJ/m3) samples respectively. The microstructure investigations of the created welds showed that in the sample welded with the conical pin, the polymeric fibers were created in the interface of PP-PP. However, the samples welded with threaded cylinder and threaded conical pins had dense structures. The results showed that the threaded cylinder pin is the most appropriate pin for creating joint between two PP plates with the FSW method.

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