Glass fiber reinforced polymer (GFRP) with excellent wave-transparent properties are the preferred choice for optoelectronic devices and microwave dielectric materials owing to their high strength, light weight, and excellent electrical properties. Traditional cutting techniques for processing GFRP have problems such as severe tool wear, low efficiency, and low accuracy. The application of laser processing can solve these problems and has broader application prospects. However, some problems remain in the processing of reduced materials by a single laser beam, such as the shielding of the subsequent laser by the pyrolysis gas, transformation of the target absorption mode due to incomplete pyrolysis of the residual carbon, and irregularity of the ablation morphology. The laser processing assisted by tangential air flow can solve these problems and improve the efficiency of material processing. In this study, a detailed investigation on the target perforation time, ablation morphology, and temperature distribution on the ablation surface under different power densities and tangential air flow was carried out. These results are helpful for improving the processing efficiency and profile of GFRP.
A fiber laser (wavelength of 1070 nm) with a maximum output power of 20 kW was used to interact with the GFRP in a relatively confined metal target chamber. Tangential air flow was provided by an air compressor and flowed out through a nozzle, and the air flow rate was measured using the Pitot tube method. A manometer was used to measure the pressure of the tangential air flow output from the nozzle; therefore, the stability of the air flow was monitored. The range of air flow rate used in the experiment was 0-1.0 Ma. The temperature evolution from the front and rear surfaces of the target was recorded using an infrared thermometer imager. The temperature data of the perforation point was extracted to draw a temperature change curve with time, and the perforation time was obtained from the falling edge of the temperature curve.
The perforation effects of GFRP are investigated at different laser power densities (848-1556 W/cm2) and tangential air flow velocities (0-1.0 Ma). It is found that the effect of increasing the laser power density on the ablation rate of GFRP is more significant than that of varying the tangential air flow rate (Figs.4 and 8). With an increase in the tangential air flow rate, the perforation time shows a decreasing trend and then a slow increase (Fig.8). This behavior is related to three effects caused by the tangential air flow: reducing the surface residual carbon content to promote the bulk absorption of the target (Fig.5), enhancing the heat convection on the target surface to accelerate the cooling (Fig.7), and providing tangential shear force to produce a mechanical erosion effect.
The perforation effect of GFRP at different laser power densities (848-1556 W/cm2) and tangential air flow rates (0-1.0 Ma) is investigated using a continuous laser with a wavelength of 1070 nm. The experimental results show that the perforation time decreases with increasing power density. A large amount of pyrolysis gas is generated in a shorter time period at higher power densities, which further results in a higher pore pressure and promotes the exfoliation process of the target. The effects of tangential air flow on the GFRP perforation process include reducing the surface residual carbon content to promote the bulk absorption process of the target, enhancing the cooling effect on the target surface, and providing a tangential shear force to produce a mechanical erosion effect. The three effects caused by tangential air flow have an obvious competitive relationship in the perforation process of the target. For the laser power density of 848 W/cm2, when the tangential air flow rate is ≤ 0.4 Ma, the effect of tangential air flow is mainly used to promote resin pyrolysis, reduce the residual carbon content, and change the target absorption mode. Hence, the target perforation time decreases with an increase in the air flow rate. When the tangential air flow rate is in the range of 0.8-1.0 Ma, the cooling effect is more obvious. Therefore, the perforation time of the target material increases slowly with an increase in the air flow rate. In addition, compared with the tangential air flow rate, the effect of the power density on the perforation time of the GFRP is more significant.
