The thermal properties during pulse laser processing of carbon fiber reinforced polymer (CFRP) are significant for optimizing process parameters and strategies. An important factor in laser ablation of CFRP materials is the temperature rise caused by carbon fiber absorption of light. However, most of them employ computer-aided design software to simulate the internal temperature field of materials presently, with few underlying algorithms for heat transfer simulation. We study the ablation of the CFRP plate by optical fiber pulse infrared laser, build a new heat transfer model, and carry out the numerical analysis and the laser ablation experiment of the CFRP plate. The experimental results show that the theoretical model is correct and feasible, thus providing references for laser processing research of CFRP materials.

During laser CFRP plate processing, the laser beams have a certain moving speed. According to this characteristic, a linear Gauss heat source is proposed to simulate the moving temperature field of laser ablation. Based on the Fourier heat transfer model, the heat transfer physical model of the nanosecond pulse laser processing CFRP plate is built, and the finite difference time domain method is adopted to analyze the model. The laser ablation of the isosceles triangle pattern in a 0.5 mm thick CFRP plate is conducted by nanosecond pulse lasers. Then, the surface roughness data after ablation is obtained by a surface roughness tester. According to the above experimental results, we verify the correctness and feasibility of the model and obtain sound process parameters of laser processing CFRP.

The MATLAB numerical analysis temperature simulation results and comparative analysis on corresponding parameters of the ultra-depth-of-field photos are presented. Fig. 10(a) shows the surface morphology of the CFRP plate when the laser power is 1 W. At this time, the maximum temperature of the material surface [470 K, Fig. 1(a)] is close to the resin decomposition temperature. The resin presents a molten state on the tow area of parallel arranged carbon fiber and then solidifies along the carbon fiber arrangement structure. Part of the molten resin penetrates the gap of the carbon fiber, while the carbon fiber has little change. Fig. 10(b) shows the surface morphology of the CFRP plate under the laser power of 5 W. At this time, the maximum temperature of the CFRP plate surface is 1158 K [Fig. 1(b)], which surpasses the decomposition temperature and gasification temperature of the resin material. The thicker part of the resin surface layer does not evaporate and is also affected by the thermal expansion pressure to form curved resin layer fragments, which is inserted into the air. When the laser power increases to 9 W, as shown in Fig. 10(c), the highest surface temperature of the CFRP plate is as high as 1500 K [Fig. 1(c)], which greatly surpasses the resin gasification temperature and exceeds the carbon fiber decomposition temperature (1153 K). The thicker resin layer is largely evaporated, but there is still a small amount of residue. Meanwhile, we decompose a small amount of carbon fibers, break the carbon filament, and expose it to the air. The evolution rule of surface roughness and the sample variance of performance data stability with laser power and laser scanning speed are shown in Fig. 14. Under the scanning speed of 200 mm/s, the performance data stability is sound and the sample variance is 1.889. At the scanning speed of 200 mm/s and laser power P=9 W, the CFRP surface temperature increases, and the epoxy resin is evaporated, with the surface roughness decreasing to 7.20 μm. According to the evolution law of CFRP material ablation quality, when the laser power and laser scanning speed are 9 W and 200 mm/s respectively, the ablation quality of CFRP materials processed by nanosecond pulse lasers is ideal.

Based on the linear velocity of laser beams, we build a heat transfer model of filament Gauss heat source for nanosecond pulse laser ablation of CFRP materials. The model only requires parameters such as laser and material properties, and its numerical simulation results are compared with the surface topography photos obtained by the super depth of field three-dimensional microscope. The experimental results are consistent with the numerical analysis results, which verifies the correctness and feasibility of the numerical simulation. This model is universal and widely applicable to provide theoretical guidance for heat transfer research on the surface of laser ablated materials. The combination experiment of laser ablation parameters for CFRP plates is carried out. The surface roughness of the ablated plate is measured with a roughness detector. The results show that good processing performance can be obtained under the laser power of 9 W and laser scanning speed of 200 mm/s. At this time, the surface roughness and sample variance are 7.20 μm and 1.889 respectively.