Carbon fiber reinforced polymer (CFRP) has been increasingly applied in various industrial fields due to its unique advantages. However, the machining method of CFRP is gradually transitioning from traditional mechanical machining to laser machining, and key issues such as surface quality control and process parameter matching in laser machining of CFRP remain immature. Traditional mechanical machining often causes defects like edge burrs and delamination, while laser machining faces challenges of uneven energy accumulation, thermal damage to carbon fibers, and unstable surface quality. Therefore, it is necessary to explore the thermal effect mechanism of laser machining on CFRP surfaces, clarify the influence of laser parameters (power and scanning speed) on energy accumulation and surface morphology, and optimize process parameters to achieve efficient CFRP machining with high surface quality, thereby providing theoretical and experimental support for the practical application of CFRP laser machining.

To achieve the above objectives, a combination of numerical simulation and experimental verification was adopted. For the simulation, a Gaussian heat source model for heat transfer was constructed based on the different energy absorption efficiencies of carbon fibers and resin in CFRP. The heat source was corrected by accounting for the dynamic movement parameters of the laser and an equivalent energy field for laser machining of CFRP laminates was established. Software was used to simulate temperature changes under different laser parameters, with the simulation parameters including laser power (5 W~10 W), scanning speed (20 mm/s and 100 mm/s), pulse frequency (200 kHz), pulse width (80 ns), and spot diameter (50 μm) (Table 1, Table 2, Table 3). For the experiment, a CO₂ laser machining system was used, and the control variable method was employed to process CFRP laminates (composed of T300 carbon fibers and epoxy resin, with a size of 200 mm×100 mm×1 mm) (Table 1). Laser power was set to 5 W, 6 W, 7 W, 8 W, 9 W, and 10 W, and scanning speed was set to 20 mm/s, 40 mm/s, 60 mm/s, 80 mm/s, and 100 mm/s. The surface roughness of CFRP after machining was measured, and the surface morphology was observed under a microscope. Additionally, an irregular "tortoise" pattern was machined to verify the machining effect of optimized parameters.

The simulation results showed that temperature distribution on the CFRP surface exhibited a typical Gaussian pattern, corresponding to the Gaussian energy distribution of the laser beam (Fig.4, Fig.5). At a fixed scanning speed of 20 mm/s, the maximum surface temperature on the carbon fiber surface was approximately 978 K when the laser power was 5 W (partial resin decomposition), 1265 K when the power was 7 W (complete resin gasification), and 1785 K when the power was 10 W (partial carbon fiber pyrolysis). When the scanning speed increased to 100 mm/s, the residence time of the laser on the material surface was reduced, leading to lower temperatures: 912 K at 5 W, 1186 K at 7 W, and 1623 K at 10 W. Experimental results indicated that the transverse surface roughness of CFRP was consistently higher than the longitudinal roughness under the same laser parameters, which verified that the direction of energy transfer inside the material was affected by the carbon fiber layup direction (Fig.7a). When the laser power was fixed, surface roughness decreased with increasing scanning speed: at a low scanning speed of 20 mm/s, the maximum roughness reached approximately 19.20 μm due to excessive energy accumulation; at a high scanning speed of 100 mm/s, the minimum roughness was about 7.03 μm (Fig.7a). When the scanning speed was fixed, surface roughness increased with increasing laser power: resin layers were gradually removed when power was ≥7 W, and carbon fiber ablation and pull-out occurred when power reached 9 W~10 W (Fig.7b). For irregular pattern machining, the combination of 30 W power and 20 mm/s scanning speed caused obvious condensed recast material and blurred pattern edges, while the combination of 7 W power and 100 mm/s scanning speed resulted in a clear and sharp pattern contour, achieving the best surface quality (Fig.11).

The Gaussian heat source model for heat transfer established in this study can accurately predict the temperature distribution and surface morphology characteristics of CFRP during laser machining, providing a reliable theoretical basis for process parameter optimization. The relatively optimal process parameters for CO₂ laser machining of CFRP are 7 W laser power and 100 mm/s scanning speed. This combination can effectively avoid excessive energy accumulation, reduce carbon fiber damage, and ensure high surface quality and machining accuracy, which can be applied to fine pattern machining of CFRP.