This paper aims to characterise surface morphology and 3D roughness parameters of unidirectional carbon fibre reinforced plastic (UD-CFRP) milled at 0°, 45°, 90°, and 135° fibre orientation angles (FOAs). Side milling experiments are conducted on UD-CFRP laminates. Surface damage forms and texture direction of milled surface are analysed. Spatial frequency of defects on CFRP surface is quantitatively determined using radially averaged 2D PSD. The kinematic-dynamic surface topography is reconstructed considering feed, runout and vibration, then the ideal roughness parameters, S_a, S_q, S_sk, and S_ku are calculated and compared with the measured ones, finally the material factor-induced roughness components are quantified. Results show that CFRP surface has no regular feed marks. The frequency of fibre breakage or surface defects is greater than tooth passing frequency. FOAs sorted by their average S_a in descending order is 135°>90°>45°>0°, where surface defects contribute 93.9%, 77.1%, 73.2%, 72.2% of the total roughness respectively, which suggests that surface defects show a more important role than tool kinematics and vibration in formation of milled surface. The negative Skewness (S_sk < 0) and high Kurtosis (S_ku = 4.0–11.5) of milled surface signify porosity and the presence of many anomalous deep valleys in milled surface, respectively.

The ultrahigh strength 300M steel has been commonly used in the manufacture of aircraft landing gear and rotor shaft parts due to its excellent mechanical properties. Creep feed grinding is one of the essential operations during the whole component manufacturing processes. In this work, the feasibility of creep feed grinding of 300M steel by using the hard zirconium corundum wheel was theoretically and experimentally evaluated. A variety of responses including grinding forces, temperature fields, specific grinding energy, surface integrity and chip modes were carefully recorded. Besides, the mechanism of ground surface profile generation and the spatial frequency spectrum of the surface profile were tentatively analyzed. It was found that the wheel speed has a relative influence on the grinding forces and temperatures of which the work hardening effect dominates the material removal with lower wheel speed while the thermal softening becomes crucial as the wheel speed exceeds the critical value for the studied 300M steel. Furthermore, a scattered spatial frequency spectrum for the generated surface profile was noticed with lower wheel speed while the spectrum gathers towards the lower frequency values with higher amplitude as the wheel speed increases. The shearing chip and flowing chip dominates the main chip type, indicating the excellent abrasive sharpness during the grinding process. In general, the used zirconium corundum wheel presents feasibility for the creep feed grinding of 300M steel because of the high material removal rate, absence of surface burn, low wheel wear and higher compressive residual stresses.