A Comprehensive Review on Friction Stir Welding of High-Density Polyethylene

A relatively new technique, friction stir welding (FSW), that works on the solid-state joining principle has shown significant development in recent years. This technique is based on the generation of thermal energy necessary to form the joint through the friction and material deformation caused by a non-consumable tool plunging into the workpiece. The FSW has previously been used for welding metallic materials such as aluminum and its alloys that were difficult to join using conventional methods. However, instead of the use of heavier metals in the automotive, aviation, and many other engineering industries, the preference for lightweight materials such as polymer materials due to their specific strength, corrosion resistance, high degree of processing, and design freedom as well as their lightness, has resulted in the emergence of the need for new techniques for joining these materials. The FSW technique has attracted great attention because of less material waste, less energy requirement, less distortion, and residual stresses. It is an environmentally friendly and economical method, unlike fusion welding techniques. Although significant progress has been made in this method, which has great potential in polymer welding applications, difficulties remain in welding high-density polyethylene (HDPE) with the FSW, which has a growing demand in many industrial applications. In addition, the limited number, as well as shallow of compiled studies on this subject in the literature, encouraged us to carry out this study. This review summarizes the results from previous studies focusing on the weldability of HDPE materials using the FSW technique. Furthermore, in this article, the operation of the process, its history, advantages, and limitations compared to other methods, materials that have hitherto been welded with it, its critical parameters that affect the mechanical properties of the welded joint, and the methods used for the characterization of the structure after the process, are reviewed. Finally, it is aimed to better understand the joining process and to shed light for researchers in future works on welding HDPE material with the FSW.