Influence of processing parameters on joint shear performance in laser direct joining of CFRTP and aluminum alloy

Abstract

Laser direct joining of a carbon fiber reinforced thermoplastic (CFRTP) and an alloy is prone to thermal defects, thereby reducing the joint performance. This can be avoided by reasonably controlling the joining temperature. To this end, a process optimization method characterized by taking full control of the melting depth and local peak temperature is proposed for representative CFRTP/Al and CFRTP/polymer/Al stacks. For the first time, a temperature simulation model considering the heat transfer during the laser direct joining of heterogeneous CFRTP/alloy stacks is established; the average calculation error of the model is <10%. Based on the simulation results, regression models of the melting depth and local peak temperature are established. Subsequently, constraints are determined by defect distribution observation and joint fracture surface analysis; thus, the optimized ranges of the process parameters are obtained. Finally, through laser direct joining experiments, the improvement in the joint performance is demonstrated and analyzed. The results suggest an enhancement in the strength of the aforementioned stacks under the optimized process, thus proving the rationality of the proposed method by controlling the melting depth and local peak temperature, particularly for CFRTP/polymer/Al stacks with strength close to 30 MPa.