Thermo-mechanical investigations for the joining of thermoplastic composite structures via friction stir spot welding

Abstract

The friction stir welding (FSW) or friction stir spot welding (FSSW) with non-consumable tool is one of the established processes for joining of thermoplastics/low melting point metals/alloys. But hitherto little has been reported on joining of similar/dissimilar thermoplastics with FSSW especially with use of semi-consumable/consumable tool. The present study deals with thermo-mechanical investigations for FSSW of thermoplastics with fully/semi-consumable tool as a novel method. The FSSW was performed on 3D printed functional prototypes of acrylonitrile butadiene styrene (ABS) reinforced with 15% Al powder (by weight) as ABS-15Al, with polyamide (PA)6 reinforced with 50%Al powder (by weight) as PA6-50Al. The online monitoring by thermal imaging camera and axial force measurements was performed to investigate variations in tensile, thermal and morphological properties. The influence of input process variables (namely: rotational speed, plunge depth and stirring time) of FSSW joints has been explored. The results of study suggest that for joining of ABS-15Al substrates with PA6-50Al, rotational speed 1400 rpm, plunge depth 2 mm and stirring time 15 s are the best settings from multifactor optimization view point. Further the tensile properties of ABS-15Al joints prepared by FSSW are comparable to virgin ABS thus made it suitable for maintenance and repair applications.