Friction plug welding of glass fiber reinforced PA6 sheets using a newly designed tool

Abstract

In the present investigation, a new tool was designed and utilized to friction plug weld glass fiber reinforced polyamide sheets. The welding process was divided into two steps: the plug nut generation and the plug weld production. Sound joints were obtained with appropriate welding parameters and the corresponding microstructure was analyzed and the joint mechanical performance was tested. Results showed that the plug nut was composed of three regions with different fiber distributions. The stir zone generated between the unsoftened plug zone and the workpiece base material showed obvious glass fiber orientation towards the rotational direction. At the bottom corner of the plug weld, a banded region with low fiber content was observed. The thermal mechanically affected zone at the weld bottom was more apparent due to the larger axial force resulted from plug plunging. Lap-shear tensile test showed that a steep drop of tensile force occurred at about 850 N and the maximum fracture load reached 1600 N. The joint failed with lower weld pulling out together with partial nugget tearing at the bottom corner of the plug weld. Through SEM, regular fiber orientation was observed on the surface of the pulled-out lower weld.