An experimental investigation on surface quality of CFRP after milling in cutting fluid environment

Abstract

Carbon fiber reinforced polymer (CFRP) are becoming more widely used in replacing metallic component as it offers better strength-to-weight ratio compared to steel while having high corrosive resistance. Although CFRP have always been manufactured near to net-shape, secondary machining process is still required to achieve the final dimension. Machining can cause CFRP to experience surface defects such as delamination, fiber pull-out and smeared matrix which lead to part rejection. The aim of this study is to investigate the effect of cutting parameters on the surface roughness and its quality. In this investigation, cutting speeds of 132, 151 and 170 m/min with constant feed rate of 1800 mm/min were applied during end milling of CFRP using uncoated tungsten carbide end mill tool in cutting fluid condition. It was observed that high cutting speed (170 m/min) produced 45.3% lower Ra than lower cutting speed (132 m/min) after machining for 6500 mm cutting distance. The occurrence of thermally degraded resin on the machined surface was apparent at higher cutting distance between 3000 to 6500 mm. Also, it was observed that the smearing of thermally degraded resin was more obvious on higher cutting speed when compared at 132 m/min cutting speed suggesting that at higher cutting speed more heat generated that resulted in increasing the cutting temperature. Fiber pullout was also found on the machined surface and the cavity formation changes with increasing of cutting distance resulting in relatively larger cavity.