Investigation of the mechanical properties of friction stir welded PA6-based polymer nanocomposite and optimizing experimental conditions

The newly fabricated two-phase composite of polyamide-6/nitrile butadiene rubber reinforced with halloysite nanotubes was welded by heat-assisted friction stir welding. The welding process was carried out via a heating system placed inside the stationary shoe-shoulder under different process conditions and materials to achieve sound joints. Influence of tool rotational speed, tool traverse speed, and HNTs content as the three input parameters on mechanical properties has been investigated using response surface methodology. Analysis of variance was utilized to establish the significance of independent variables on welding overall quality characteristics. The multi-response optimized variables were found to be as follows: rotational speed = 900 (RPM), traverse speed = 14 (mm min−1), and HNT = 6.72%. Under these conditions, the maximum values attained for tensile strength, Young's modulus and impact strength were 59.1 (MPa), 1416.3 (MPa) and 124.1 (J m−1), respectively. Optimal results have been validated through confirmation experiments. Morphological and microstructural characterization of the fractured surface of samples using scanning electron microscopes revealed that the increase of shear stress due to tool stirring action as well as the addition of halloysite nanotubes improves the interfacial interactions and produce fine rubber phase of PA6/NBR composites.