A strong mechanical riveting structure in PC and PBT/GF induced by dual-wavelength during laser transmission welding

High-quality plastic joining techniques using welding are urgently required in many engineering areas. Controlling morphology formation in joints plays an important role in the final quality, but relatively controlling methods are still challenging. In this paper, we propose an in-situ formed mechanical riveting structure between polycarbonate (PC) and polybutylene terephthalate reinforced with 10 % glass fiber (PBT/GF), which is induced by dual-wavelength through a home-made setup. First, the spectral properties of PC and PBT/GF are investigated to analyze optical differences at wavelengths of 980 nm and 1710 nm. Morphological characterizations reveal a significant number of glass fibers migrated across the interface and reached the PC side, forming a robust mechanical structure. These migrated glass fibers, serving as a mechanical rivet, could increase the tensile performance of the joints along with interfacial fusion bonding. Furthermore, the simulated temperature field indicates that employing a 980 nm laser effectively increases the welding temperature while preventing the thermal decomposition of the materials. The tensile test results show that the maximum tensile force using the 1710-PC//980-PBT/GF welding method, reaching 29.80 %, 20.40 %, and 111.3 % higher than that of 980-PC, 1710-PC, and 980-PC//1710-PBT/GF joints. And the corresponding displacement achieves 2.0-fold, 1.5-fold, and 4.0-fold increases compared to the above control groups. The fracture surface of the substrate and interfacial failure validate that the improved mechanical performance of joints could be attributed to the formation of a mechanical riveting structure. This paper verifies that dual laser beams could properly regulate the welding temperature field, control the morphology, and enhance the joint’s final performance.