An overview of friction stir welding of high-density polyethylene

Friction stir welding (FSW) and friction stir spot welding (FSSW) of thermoplastics is becoming popular because of its many industrial applications. This paper specifically reviews the experimental studies available on the FSW and FSSW of high density polyethylene (HDPE), as it is a high demand thermoplastic material used in many industrial applications. The effect of process parameters (tool rotational speed, traverse speed, plunge depth, etc.), tool material and geometry (profile and size), and medium conditions (open-air, submerged, heat-assisted, cooling-assisted, etc.) on the weld joint mechanical properties are discussed. These studies help with narrowing the ranges of all the parameters involved, to optimize welding conditions to achieve highest joint strength. ANOVA (analysis of variance)-based studies are also discussed which help in determining the relative significance of the parameters affecting the joint strength. The thermal behavior of the weld joints, through differential scanning calorimetry (DSC) studies, has also been discussed. Finally, a few recommendations for future studies are presented.