Laser-based thermomechanical joining of semi-transparent thermoplastics with technical steel

The laser-based thermomechanical joining process was adopted to produce hybrid components made of AISI 304 stainless steel and semi-transparent thermoplastic materials, i.e. polypropylene and polyamide. The process parameters, i.e. laser power, laser-polymer interaction time, and metal surface texture, were optimized using the full factorial experimental approach, and the joints' quality and performance were examined to determine the best operational parameters' combination. Shear tests were carried out to evaluate the resistance of the joints, while morphological and fracture surface analyses were performed to have a better understanding of the phenomena that emerged during the joining process. The findings demonstrated that the shear force and the joint area were significantly influenced primarily by the texture, followed by the laser power, and finally the interaction time. The optimal combination allowed the realization of joints whose maximum shear force reached around 750 N for polypropylene and around 2200 N for polyamide, achieving respectively 60% and 53% of the tensile force of the polymer base materials.