مشخصات پژوهش

In the present study, friction stir spot welding of PTFE sheets is investigated. Due to the special properties of this polymer, its welding is a challenging task. According to the primary tests, the friction stir spot welding of PTFE is possible, however, it requires more dwell time, i.e. a dwell time of at least 6 min is required to achieve a joint with an acceptable strength. All specimens were welded with a tool rotational speed of 1250 rpm, and a dwell time of 9 min. Two tool geometries including a conventional tool with a cylindrical pin and a pinless tool were investigated. The spot-welded samples with the pinless tool have no keyhole. Each tool was used to spot weld two different samples with different tool shoulder plunge depths of 0.1 and 0.2 mm. The tensile-shear test was used to evaluate the tensile strength of the welded samples. The results suggest that friction stir welding is a joining method that could be used to join PTFE sheets successfully. Although the welding time is an issue that may hinder the application of this method to join PTFE sheets. The pinless tool produces joints with higher strength. Increasing the plunge depth also increases the joint strength. The highest strength that was obtained by spot-welded samples is 373.7 N which was obtained by the sample that was welded with the pinless tool and a plunge depth of 0.2 mm.