Fiber-resin thermal equilibrium in low-power laser-assisted micro-milling of CFRP: one-dimensional heat transfer modelling and its effects on cutting forces, surface quality, and tool wear

Abstract

Carbon fiber reinforced polymers (CFRP) are widely used in aerospace and other fields because of their good mechanical properties, but they are difficult to machine using conventional micro-milling (CM) and laser machining. When milling CFRP in a traditional way, it generates a relatively large cutting force because the tool directly contacts the workpiece, heat-affected zone (HAZ) will be generated because the laser requires high power to cut the fiber. To optimize this problem, this research proposes a method of laser-assisted micro-milling (LAMM), which firstly uses laser to form a 0.5 mm wide preheating slot, and then micro-milling it. To this end, a one-dimensional heat transfer model is employed to estimate the required laser power, bringing the resin into a decomposed state while leaving the fibers unaffected, building a thermal-equilibrium state of fiber and resin by controlling the laser power. Compared with other processing methods, the method proposed in this paper can effectively reduce the damage caused by thermal effects and achieve better processing quality. In this way, the HAZ can be reduced, and the micro-milling condition will be better. Comparative experiments under different spindle speeds, feed rates, axial depths of cut, and laser powers show that LAMM markedly enhances machining performance: The average total cutting forces can be reduced mostly by up to 18.37% at different spindle speeds, 19.61% at different feed per tooth values, and up to 20.24% at different axial depths of cut, surface defects such as fiber pull-out and resin smearing are mitigated; the surface quality is significantly improved, area roughness Sa decreases by 37.42%, 17.56%, and 15.76% in the initial, middle, and final groove segments, respectively. The arithmetic mean roughness in middle segment is measured on wide direction, with 36.23% reduction. Tool wear is also alleviated, with the cutting edge radius under LAMM averaging only about 25% of that in CM. The results demonstrate that LAMM, guided by the thermal behavior of CFRP constituents, effectively improves surface integrity and tool longevity, offering a promising approach for high-precision micro-machining of CFRP composites.