Milling properties of Kevlar 49 fiber composite based on fiber orientation in cryogenic cooling

Aramid fiber–reinforced epoxy resin matrix composite is an anisotropic and heterogeneous material. And the machinability is strongly dependent on the fiber orientation. In this paper, a composite milling model was established based on fiber orientation θ. Meanwhile, a series of cryogenic cooling milling experiments were carried out to research the influence of fiber orientation on surface morphology, surface roughness, milling force, and tool wear. The results show that the acute angle milling has more advantages than the obtuse one. When tool sweeps at about θ = 55°, the maximum milling force can be gotten. And the maximum shearing action can be reached for latitude fiber at θ = 30°, as well as effectively chip broken for latitude and longitude fibers. Similarly, with increased θ, the shearing fracture is weakened with insufficient chip breaking, but none affected for longitude fibers. Besides, it can be predicted that when the cutting speeds are 50, 100, and 150 m/min, as well as fiber orientation 26°, 34°, and 35°, respectively, the processed surface roughness is 0.93 μm, 0.71 μm, and 0.6 μm. At the same time, tool wear is relatively serious with θ = 40° with a stable tool wear stage, and the processing effect is not affected. Furthermore, using the bigger cutting parameters, the better cryogenic cooling milling effect can be obtained at fiber orientation near 30° with less burr defect.