Laser-assisted joining of black high-density polyethylene with aluminum: experimental study and statistical analysis

This work presents a characterization study of an innovative heat-conduction laser joining process for manufacturing hybrid components composed of metal, specifically 6000 series aluminum alloy, and polymer, specifically high-density polyethylene. After conducting initial thermo-mechanical characterization of the polymer material and preliminary laser irradiation tests on aluminum surface samples, the process window for laser processing was identified to activate hybrid joining while avoiding polymer degradation mechanisms. Several process factors were examined, including laser power, interaction time, and surface texture, with the goal of enhancing mechanical interlocking with the molten polymer following irradiation by a static laser beam. The development of a custom experimental setup for laser joining and the application of the Design of Experiments methodology enabled the optimization of process parameters, ensuring the production of high-quality, high-performance joints, as demonstrated by single-lap shear tests. EDXS analysis confirmed the chemical integrity of the interface, showing that the bonding is purely mechanical interlocking without elemental diffusion. The experimental results confirmed the technological feasibility of the proposed laser heat conduction joining process for hybrid components, demonstrating that it is fast, cost-effective, eco-sustainable, automatable, and efficient across all scenarios analyzed. The results showed how the ultimate shear force was higher on average in the case of 200 W power, 50 s time and texture A. Under optimal joining conditions, i.e., 30 s interaction time, texture A, 200 W power, maximum shear force and apparent shear strength exceeded 2000 N and approximately 5.5 MPa, respectively, yielding a joint efficiency of about 31.2%.