Novel study of joining of acrylonitrile butadiene styrene and polycarbonate plate by using friction stir welding with double-step shoulder

Friction Stir Welding (FSW) is one of the most efficient joining process for joining of plastics. The aim of the present work is to introduce the concept of a double step shoulder over the conventional single shoulder tool to eliminate the effect of excessive flashing of polymers and investigate the suitable process parameters for FSWed dissimilar joints. Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate (PC) plates of 6 mm thickness were joined in square butt configuration by FSW process with H13 tool steel having Right-Hand Threaded (RHT) cylindrical pin profile. To study the ultimate tensile strength, extensibility, joint efficiency, and fracture locations, a L-27 orthogonal array was designed with input parameters namely, tool rotational speed (rpm), tool traverse speed (mm/s), and tool tilt angle (degrees). The RHT pin profile tool rotate in the clockwise direction while advancing forward gives defect free welding while the counter-clockwise direction of rotation expels the material outside thereby generating defective weld. The diameter of the lower shoulder was kept small for reducing friction between tool work-piece interfaces. Maximum Ultimate Tensile Strength (UTS) of 22.41 MPa (73.16% of base material) was obtained at a tool rotational speed of 1600 rpm, tool traverse speed of 0.2 mm/s and tool tilt angle of 2 degrees. Microstructural analysis revealed an interlocked phenomenon, the transportation of PC flash into the ABS side and tightly locked both polymers. A close relationship between UTS, fracture locations, and microstructures has been established.