Parameter optimisation of friction stir welded dissimilar polymers joints

There has been a significant increase in the use of polymeric materials in various areas of industry and engineering, which were previously dominated by metallic components. Recently, the possibility of implementing friction stir welding (FSW) technology for welding polymer-polymer and polymer-metal has come under investigation. Polymeric materials behave differently from metallic ones, and there is still a limited number of research works in the literature concerning this specific topic. In this study, a stationary shoulder made of Teflon was used to weld thin plates of polypropylene and polyethylene together in the lap-joint configuration without external heating. Using a stationary shoulder, the probe generates all the frictional heat and stirs the nearly molten material under an axial force. This article is focused on parameter optimisation for friction stir welded lap joints of dissimilar polymers using a new tool concept. It was concluded that the tool design has the most effective role regarding the lap-shear strength of joints. Welds fabricated with the optimised welding parameters present good surface quality and strength. Moreover, for welding polymeric materials with this method, the main defects have been found on the retreating side of the welds. This behaviour can be explained by insufficient heat generation on the retreating side as well as poor thermal conductivity of polymeric materials.