Improving the tensile and impact properties of laser welded joints between PP and HDPE/GNP

This paper studies the laser welding of polypropylene (PP) and high-density polyethylene (HDPE) to create hybrid components. The main challenge for PP/HDPE laser welding is the higher melting point of PP compared to HDPE. To address this challenge, graphene nanoplatelets (GNP) were incorporated into HDPE via 3D printing to enhance its thermal and mechanical properties and reduce the melting temperature disparity. Laser welding was then used to join the resulting HDPE/GNP nanocomposite to PP. The performance of the nanocomposite and the weld joints was evaluated through tensile and impact testing, supplemented by SEM and DSC analyses. The effects of laser power, welding speed, and pulse frequency on weld tensile and impact strength were modeled using the response surface methodology (RSM). The results indicate that laser power, welding speed, and pulse frequency significantly influence the mechanical performance of the joints. Increasing laser power and welding speed within the studied ranges generally improves tensile and impact strength by reducing microstructural defects, provided that excessive heat input and thermal degradation are avoided. Optimal joint performance, maximizing both tensile and impact strength simultaneously, was achieved at a laser power of 48.5 W, a welding speed of 20.4 mm/s, and a pulse frequency of 35 Hz.