Joining <scp>CFRTP</scp> ‐ <scp>TC4</scp> hybrid structures with laser rotating welding technique: Joining mechanism, parameter optimization, and mechanical properties

Abstract The lap welding of TC4 (Ti‐6Al‐4V) and carbon fiber reinforced thermoplastic composites (CFRTP) was conducted using laser rotating welding. The difficulty of joining CFRTP and TC4 is that the thermal expansion coefficient between the two materials is very different, which easily produces residual stress and eventually leads to low joint strength. In addition, the melting point and thermal conductivity of the two materials are very different, and it easily causes thermal decomposition due to excessive heat input during welding. In order to meet this challenge, a combination of simulation and experimental methods was employed to analyze the joint formation mechanism and the impact of connection parameters on heat input. The findings indicate that the optimal shear resistance of the CFRTP‐TC4 joint is achieved with a laser power of 70 W and a welding speed of 2 mm/s. At consistent heat input levels in the fusion zone, the shear force of the joint exhibits minimal fluctuation. The failure modes of CFRTP‐TC4 joints under tensile stress and varying fatigue load levels were also examined. The primary failure mode identified is the interlaminar tearing of the CFRTP material. By fitting experimental data across different fatigue load levels, a fatigue life expression suitable for CFRTP‐TC4 joints was derived. This expression allows for a more accurate evaluation of the joint's fatigue performance in practical applications, thereby facilitating design optimization and enhancing material reliability. Highlights The temperature field of laser welding was simulated by FEM (finite element method). Joints can be reinforced by surface pretexturing and adding resin. The main parameters have essential effects on the strength of joints.