Study On The CFRP Machining By Micro-texture Milling Tools

The carbon fiber reinforced composite(CFRP)is a kind of light mass,high specific strength,high modulus than,corrosion resistance and high durability features new materials.CFRP is more widely used in the field of aerospace,automobile and other advanced manufacturing etc.Many CFRP are made in required structure size by the preforming way in the process of practical application.However,the carbon fiber reinforced composite(CFRP)in traditional milling process is easy to produce burr,avulsion(tear),stratification and other defects.Changing the contact characteristics of tool-chip interface can be used to improve the cutting process,the effectiveness of which may be achieved by surface texturing of the tools.Thus,two kinds of surface structures were fabricated on the rake face of the carbide double-edge milling tool:(1)linear grooves parallel to the main cutting edge(named PAM);(2)linear grooves perpendicular to the main cutting edge(named PEM).Dry cutting tests were carried out on unidirectional CFRP laminates with different fiber orientations(0o,45o,90o and 135o)using the two developed tools and the conventional tool(named NCM).The surface machining quality was assessed in terms of the surface roughness,burr,tear phenomenon and the way of fiber breakage.The main research contents are as follows:(1)The typical machining defects and fiber shear morphology of CFRP cutting process are analyzed.The main factors affecting the morphology of fiber shear fracture were described.The main fiber fracture morphologies were occurred,i.e.bending-induced fiber fractures,shear-induced fiber fractures,compression-induced fiber fractures and fiber-resin stripping.There different fiber burr morphologies were observed,including the formation of burr on both sides,the formation of burr in cutting direction,and the formation of burr in the direction.(2)The orthogonal test of the cross-direction CFRP fiber layer was used,and the CFRP laminated was cut by NCM tool.The influences of milling process parameters on surface roughness and milling force was analyzed.Then,the single factor test of three kinds of cutter milling four direction CFRP laminated was carried out based on the analysis of the significant processing parameters.The results show that the main shaft revolution and the amount of feed per tooth have high influence on the surface roughness and milling force.The size of surface roughness and milling force decreases with the increase of spindle rotation and increases with the increase of feed quantity.Reasonable surface texture is benefit to reduce surface roughness and milling force.(3)Dry cutting tests were carried out on unidirectional CFRP laminates with different fiber orientations(0o,45o,90o and 135o)using the PAM tools,PEM tool and NCM tool.The surface machining quality was assessed in terms of the surface roughness,burr and fiber shear phenomenon.Analysis found that: the micro-textures effectively reduce milling surface roughness,because the micro-textures can accommodate chip fiber during the process of milling CFRP,which can avoid the fiber make lager bending deformation on the machined surface by changing the chip of the fiber bending deformation degree and direction.Therefore it is benefit to reduce the surface roughness value by reducing the size and quantity of machined surface micro-pits.Meanwhile,the micro-texture tools is more effective in reducing the burr lengths,bending deformation of fiber chip,and the tearing phenomenon of milling.The machined surface burr lengths produced by PAM tool and PEM tool milling is compared with that of NCM tool.(4)The surface morphology of different milling conditions was observed.The mechanism of surface micro-texture in the cutting process is described.The Angle between the instantaneous shear direction and the fiber direction is the shear Angle,which act as a notable effect in the surface machining quality.It is observed that the serious tear and shorter burr appear on the processed surface when the shear angle between 45?and 90?,and it is opposite when the shear angle between 90?and 135?.