Temperature-dependent material removal during pulsed laser processing of CFRP composites

Abstract

Understanding the material removal mechanism and thermal characteristics in pulsed laser machining of carbon fiber reinforced polymer (CFRP) composites is significantly important for optimizing the process parameters and strategies, which helps improve the processing quality of workpiece and inhibit the processing defects. However, the current studies mainly focused on the effect of process parameter variation on heat affected zone (HAZ) size and processing efficiency during pulsed laser processing of CFRP laminates. These studies did not well reveal the formation mechanism of machining defects related to temperature characteristics during the material removal process. Herein, this study proposes a material removal mechanism referred to thermal evaporation and oxidation of fiber and matrix, and mechanical removal associated with the temperature characteristics in pulsed laser machining of CFRP composites. Comparative laser ablation experiments of CFRP were conducted in air and in vacuum to verify the material removal mechanism. Besides, temperature characteristics and dynamic images during CFRP removal process were obtained via utilizing an infrared pyrometer and a high-speed camera, respectively. The results show that, in the absence of atmospheric pressure, the work done by recoil pressure improves the mechanical removal efficiency, and the jetting speed of removed carbon fiber reaches up to 45 m/s. The existence of airflow results in improving instantaneous temperature, but reducing average temperature in laser processing region.