Influences of laser profiles on the weld quality of glass fiber reinforced PBT using laser transmission welding

Laser transmission welding (LTW) plays an important role in plastic connection for fabricating large and complex products. The laser profile as a key parameter determines the spatial energy distribution, affecting the temperature gradient of the welding path and the quality of the weld seam. In this study, the effect of two laser profiles, the Gaussian and Flat-top beams on the temperature field and weld quality was studied through experiments and simulation. First, the transmission behavior of the laser beams is studied through the spectrometer and photosensitive paper, revealing the laser spot energy distribution and spatial changes after passing through the laser-transparent layer. Furthermore, the tensile force test demonstrated that the weld seam prepared by the Gaussian beam present higher tensile force, with a tensile force of 634.18 N at the line density of 11.2 J/mm, 24.23 % higher than that of the Flat-top beam. Moreover, the simulation result from the finite element model found that the maximum welding temperature of the Flat-top beam is 39.42 % higher than that of the Gaussian beam, consistent with the results of morphological and mechanical results. This study might present a potential way for selecting the laser profile in LTW, further improving weld quality through optimizing process windows.