The effects of cutting conditions and tool geometry on mechanics, tool wear and machined surface integrity when routing CFRP composites

Abstract

Carbon-fibre-reinforced plastic (CFRP) composite materials are highly susceptible to tool-wear-induced interlayer delamination and superficial carbonization when subjected to routing, particularly under high cutting speeds (> 100 m/min) and high feed rates (> 0.40 mm/rev). This study modelled orthogonal, mono-oblique, and dual-oblique cuttings in routing CFRP composite workpieces with a consideration of the bending-moment-induced deflections in the cutting tools, and the effects of the cutting conditions on the delayed tool wear, vibrations and the produced machined surface integrity. The interactions of the cutting conditions and the alterations in the cutting edges are discussed and analysed, particularly the quality of the machined surfaces in their forms and topographies. The tool geometries of helical and cross-flute routers outperformed straight-flute routers in preserving tool life, by allowing the cutting forces generated by the primary cutting edges to counteract those generated by the secondary cutting edges, and in so doing, reduce the forces more effectively. Nonetheless, the straight flute router produced a smooth surface without the pulled-out fibres, smearing, or material adhesion produced by the other routers. Statistical methods were used to analyse the relative contributions of the various operating parameters for the least power consumption. We also sought to clarify the cutting mechanisms underlying the observed cutting forces and tool flank wear, as well as to interpret their effects on the machined surface texture, roughness, and topography. In addition, a detailed discussion of fibre fracture mechanisms and subsurface alterations on the matrix material are provided.