Kilowatt average power short-pulse laser processing of CFRP - Quality challenges

Abstract

Laser processing of carbon fiber reinforced plastics (CFRP) is more demanding than most other material concerning thermal damage due to its strongly inhomogeneous structure and the high heat conductivity of the fibers. Short-pulsed lasers conveniently provide the intensity, which is necessary to reduce the thermal damage of the matrix caused by the strong heat flow along the fibers during interaction of the laser with the material. However, average powers above 1 kW are necessary for high cutting velocities or ablation rates as needed for example in automotive applications. With increasing average power, the movement of the focal spot over the processed surface has to be increased in order to avoid local heat accumulation between subsequent laser pulses (HAP). In addition, depending on the contour length, the heat accumulation between consecutive scans (HAS) becomes an issue.The latest results of short-pulse laser processing of CFRP at average powers above 1 kW with a Nanosecond CO2-laser at the wavelength of 10 µm and a Picosecond Yb:YAG laser at the wavelength of 1 µm will be presented. The quality challenges arising from the HAP and HAS effects will be discussed and the limits regarding average power, feed rate, and number of scans will be estimated.Laser processing of carbon fiber reinforced plastics (CFRP) is more demanding than most other material concerning thermal damage due to its strongly inhomogeneous structure and the high heat conductivity of the fibers. Short-pulsed lasers conveniently provide the intensity, which is necessary to reduce the thermal damage of the matrix caused by the strong heat flow along the fibers during interaction of the laser with the material. However, average powers above 1 kW are necessary for high cutting velocities or ablation rates as needed for example in automotive applications. With increasing average power, the movement of the focal spot over the processed surface has to be increased in order to avoid local heat accumulation between subsequent laser pulses (HAP). In addition, depending on the contour length, the heat accumulation between consecutive scans (HAS) becomes an issue.The latest results of short-pulse laser processing of CFRP at average powers above 1 kW with a Nanosecond CO2-laser at the wavelengt...