Effect of interface control on bonding behavior of steel and CFRP during laser welding

Abstract

In order to investigate the effect of interface control on bonding behavior of metals and polymer during laser welding, the laser welding of steel and carbon fiber reinforced polymer (CFRP) was studied. Combining experiments with simulation, the effects of laser micro-texture and the interlayer PA66 on the joint mechanical performance, fracture morphology, interfacial pore characteristics, temperature distribution and gas–liquid flow were explored. Experimental results show that when scanning line space is 0.1 mm, the scanning times is 5, and the interlayer thickness is 20um, the shear force of the joint is optimal at 2736 N, which is an increase of about 197 % compared with the joint without interfacial control. The fracture characteristics of controlled joint are a mixture of polymer cohesion fracture and interfacial fracture. During the laser welding, as the molten polymer fills and contacts the high-temperature metal groove, the temperature of the polymer in this area increases, the thermal decomposition intensifies, and the interfacial pore and unbonded characteristics increase. With the increase of interlayer PA66 thickness, the proportion of PA66 in the joint increases, and the thermal decomposition of PA66 without fiber reinforcement intensifies, resulting in an increase in pore and unbonded phenomenon at interface of textured DP780-PA66-CFRP composite joint, and a decrease in joint mechanical performance.