Effect of scanning mode on temperature field and interface morphology of laser joining between CFRTP and TC4 titanium alloy

Abstract

Dissimilar components composed of CFRTP (Carbon Fiber Reinforced Thermoplastic Polymer) and TC4 titanium alloy are increasingly applied in the aerospace field. The scanning mode offers a significant influence on the quality of laser joining joint between CFRTP and TC4 titanium alloy. Therefore, the laser joining between TC4 titanium alloy with surface microgrooves and CFRTP has been implemented under oscillating laser joining mode and linear laser joining mode respectively in the present research. The temperature distribution is qualitatively explored based on the established mathematical model of laser joining between CFRTP and TC4 titanium alloy. The interface morphology and the joining strength of CFRTP/TC4 titanium alloy lap joints under oscillating laser joining and linear laser joining are compared. The results indicate that the simulated temperature distribution shows good agreement with the experimental results. Compared with linear laser joining, the oscillating laser joining weakens the heat concentration and creates a heating zone with larger area and more uniform temperature distribution. The interface morphology of laser joining CFRTP/TC4 titanium alloy joints obtained by oscillating laser joining presents better resin filling and fewer bubble defects due to the temperature variation of the form of unequal amplitude oscillations, with the resin filling ratio of 92.20% and the porosity of 3.78%. In contrast, the linear laser scanning mode with a large number of large-sized bubbles in the filling resin and small-sized fusion gaps distributed at the interface holds a resin filling rate of 60.11% and a porosity of 32.89%. By adopting the joining method with oscillating laser scanning mode, higher quality joints can be obtained with the joining strength of 24.48 MPa.