Laser-based repair of carbon fiber reinforced polymers with polyamide 6 matrix material

In the aviation industry, carbon fiber reinforced plastics (CFRP) are used as a standard material. Due to the high strength-to-weight ratio, weight can be saved and the fuel consumption, for example of airplanes or cars, can be reduced. More and more thermoplastics are used as matrix materials, because they enable new production and repair processes. In order to reduce repair costs, an automated, reliable and fast process is needed. For the repair of CFRP with polyamide 6 (PA6) matrix material, a laser-based ablation process for the removal of the damaged material and a laser welding process for the refill of the scarf with a patch are being developed. The ablation of the scarf and the cutting of the patch are conducted with a high power nanosecond pulsed laser, which has a maximum power of P_L = 1500 W and emits at a wavelength of λ = 1030 nm. For the joining process, an automatically controlled heat conduction welding process is developed. Therefore, a diode laser with a maximum average power of P_L = 300 W and a wavelength of λ = 940 nm is utilized. For the analysis of the ablation and cutting process, samples were analyzed in order to determine the heat affected zone. For the evaluation of the welding process, overlap samples were welded and tested to determine the weld seam strength. In addition, cross sections were prepared and analyzed for defects. Finally, the results were correlated in order to determine a high process quality.