Joining of Polyethylene Using a Non-Conventional Friction Stir Welding Tool

Area of Science:

• Materials Science
• Manufacturing Engineering
• Polymer Processing

Background:

• Friction stir welding (FSW) is a solid-state joining process.
• Polyethylene (PE) is a widely used thermoplastic polymer.
• Joining thick PE plates presents challenges in achieving high joint integrity.

Purpose of the Study:

• To investigate the butt-welding of 6 mm-thick polyethylene plates using friction stir welding (FSW).
• To evaluate the influence of non-conventional stationary shoulder tool parameters on weld quality.
• To optimize FSW parameters for enhanced polyethylene joint performance.

Main Methods:

• Utilized a non-conventional stationary shoulder tool for friction stir welding (FSW) of 6 mm-thick PE plates.
• Varied shoulder temperature (unheated vs. 85 °C), rotational speed (870-1500 rpm), welding speed (60-120 mm/min), and plunge depth (5.5-5.7 mm).
• Evaluated weld morphology, hardness, ultimate tensile strength, elongation at break, and fracture modes.

Main Results:

• Shoulder heating significantly improved joint efficiency and reduced internal/external defects like porosity and surface burning.
• Defect-free weld seams were achieved with higher rotational speeds and lower welding speeds.
• A maximum joint efficiency of approximately 97% was obtained at 85 °C shoulder temperature, 1500 rpm, 60 mm/min welding speed, and 5.7 mm plunge depth.
• A joint efficiency of 92% was achieved at a welding speed of 120 mm/min, which is the highest reported speed for >90% efficiency.

Conclusions:

• Shoulder heating is critical for optimizing friction stir welding (FSW) of polyethylene.
• Achieving high joint efficiency in PE welds is possible with optimized FSW parameters, including elevated shoulder temperatures and controlled welding speeds.
• The study demonstrates the feasibility of high-speed FSW for polyethylene with excellent joint quality.