Experimental study of coated tools effects in dry cutting of natural fiber reinforced plastics

• We study the effect of coated tools on milling process of flax fiber composites.
• Cutting edge radius made by coating has a significant effect on surface finish.
• The pertinent scales for surface finish analysis are between 50 μm and 1 mm.
• Fiber shearing starts once the chip thickness exceeds the cutting edge radius.
• TiB2 and diamond coatings are wear resistant against flax composite machining.

This work aims to investigate the tribological effects of coated tools on the surface finish of natural fiber reinforced plastics (NFRPs) during profile milling process with particular emphasis on the natural fiber cutting mechanisms and tool wear. Both up-milling and down-milling configurations were considered. The cutting experiments were carried out on unidirectional flax fibers reinforced polypropylene resin (UDF/PP) using three different cutting tools. Uncoated tungsten carbide, titanium diboride (TiB2) coated and diamond coated were used to conduct profile milling tests. Tribological cutting contacts were evaluated by measuring the specific cutting energy. Surface state was acquired by a scanning electronic microscope (SEM) and an optical microscope (OM). Surface topography was measured using a 2D Surfascan stylus profilometer. Machined NFRP surface finish was characterized using standard and multiscale analysis based on wavelets transform.Results show that the cutting edge radius made by tool coating has a significant effect on surface finish. Natural fiber shearing is more efficient once the removed chip thickness exceeds the cutting edge radius value. Moreover, it had been demonstrated that the pertinent scales for surface finish analysis are between 50 μm and 1 mm which correspond to the multiscale fiber reinforcement structure. Furthermore, and unlike the uncoated tool, TiB2 and diamond coatings allow a good wear resistance of the cutting tools against the tribological solicitations of flax composite machining.