Study on laser-assisted joining of titanium (Ti6Al4V) to polyether ether ketone (PEEK) for Enhanced hybrid joints

In the present paper, a 200 W diode laser equipped with a beam expander was adopted to create hybrid joints between pure PEEK polymer and titanium alloy (Ti6Al4V). To this end, a new setup was developed: the laser was equipped with a 5x beam expander, allowing the laser beam a spot of about 30 mm, and the joints were performed in static conditions. The latter allows more efficient control of the joining process, identifying the technological window of processability of the polymer, thus avoiding ineffective heating or excessive degradation during laser-assisted joining operations. Moreover, the adopted setup is very cost-effective from an industrial perspective, depending on the low powers applied, compared with those adopted in the literature. Single-lap joints were carried out in order to study the influence of the laser parameters on the joint strength. Before joining, two different textures were performed on the titanium surface; mechanical tests were carried out to determine the optimal processing conditions, while fracture surface analysis and morphological one were performed in order to better understand the phenomena developing during the joining process. The design of experiments (DoE) approach and analysis of variance (ANOVA) were adopted to identify significant process control factors and analyze how they influence joint performance. From the results, the new setup allows a joint efficiency of about 30 % in the best conditions, a very high value, compared to other traditional joining processes, such as adhesive bonding.