<p>Carbon fiber reinforced polymer (CFRP) composites are widely utilized in aerospace applications owing to their superior physical properties. Milling is a critical manufacturing process for achieving dimensional tolerances, geometric accuracy, and surface quality requirements of CFRP components. However, due to CFRP's inherent heterogeneity and anisotropy, it is classified as a typical difficult-to-machine material. The milling process is particularly complex, involving intricate material removal mechanisms, and frequently induces severe machining defects. This paper establishes a finite element simulation model for oblique cutting of CFRP with different fiber orientation angles (<i>θ</i>), investigating the material failure behavior and fiber fracture process during oblique cutting, as well as the relationship between the tool inclination angle (<i>i</i>) and chip dimensions. The morphology of chips and surface topography under different tool inclination angles are analyzed. The fiber orientation angle significantly influences the failure mode of materials and the formation of surface damage.</p> Graphical abstract <p>Graphical abstract illustrates the oblique cutting of CFRP through finite element simulation and experiments, revealing the relationship between fiber orientation angle and machined surface damage</p> <p></p>