Mechanical properties and weld characteristics of friction stir welding of thermoplastics using heat-assisted tool

Friction stir welding (FSW) is a welding technique in which a non-consumable rotating tool with a profiled pin is pressed on the adjoining surfaces and transverse along the welding direction to produce a weld trail. The technique was first applied to metals and alloys; lately, its use has also been extended to thermoplastic polymers. In this work, FSW of HDPE thermoplastic polymer has been investigated and effort is made to achieve welds properties comparable to the base material. FSW of thermoplastics is different from metals because of their different nature and thermal conductivity. Conventional FSW techniques are not effective in its current form and inhibit many challenges to welding of HDPE. To address these problems, a specialized heat-assisted welding tool was developed and mounted on CNC machine to carry out extensive welding investigations. Statistical techniques were used to investigate the effect of temperature, rotational and transverse speed on the weld characteristics. It was revealed that temperature is the most significant factor followed by rotational and traversing speeds. In general, a higher temperature in combination with lower transverse speeds produced the most desirable results. In terms of ultimate tensile strength (UTS), weld joint efficiency of 98% of the base material was achieved through optimization of process parameters. Ultimate tensile strength of 23 MPa and combined weld efficiency of 66% was achieved which is closely comparable to the base material. This work is a leap forward towards understanding the FSW of a vast range of the thermoplastic.