Laser Processing Parameters Optimization of Carbon Fiber Reinforced Structural Plastics

Composites based on continuous carbon fiber and polymer resins (CFRP) offer higher weight strength than many structural metals, enabling significant weight reductions in various industries. A key challenge in fabricating complex CFRP structures is the trimming of blanks, which often leads to delamination and defects when using traditional methods like milling or waterjet cutting. While laser cutting mitigates some damage, differences in absorption and thermal conductivity between carbon fiber and epoxy resin result in uneven heating and defect accumulation. This study aims to identify the most effective operational modes of shortpulse femtosecond lasers to optimize processing speed and surface quality in CFRP trimming. A series of experiments determined the most efficient laser ablation parameters for CFRP, defined as the ratio of ablated material volume to applied energy. Results showed that increasing the pitch value (distance between parallel laser scanning tracks) improves ablation efficiency but reduces uniformity and predictability. Optimal efficiency is achieved with pitch values of 0.7-1 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{m}$</tex> at 2.5-3 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mu \mathrm{J}$</tex> energy, and 0.1 <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.4 \mu ~\mathrm{m}$</tex> at 3.5- <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$4 \mu ~\mathrm{J}$</tex> energy. Higher energy values decrease efficiency. Larger pitch values result in increased processing roughness and depth, with significant variations observed at higher energies. SEM analysis indicated uniform surfaces post-ablation, with reduced epoxy resin and exposed carbon fibers. EDS analysis revealed a slight increase in carbon content and a decrease in oxygen, indicating selective epoxy resin ablation. These findings suggest that ablation efficiency and surface quality depend nonlinearly on pitch width and pulse energy, offering a narrow window for optimal CFRP laser processing. These results can enhance CFRP cutting, texturing, and drilling, potentially improved by adjusting laser wavelength or adding special additives to the polymer matrix.