Investigation on cutting mechanism and micro-damage evolution in orthogonal cutting of T300/USN20000-7901 unidirectional laminates.

This paper investigated the cutting behaviors and chip formation in machining of carbon fiber reinforced polymer (CFRP) composites. The single cutting edge and unidirectional (UD) laminates of six different fiber orientations from 0° to 150° with an interval of 30° were employed in the orthogonal cutting test. The effects of fiber cutting angle, cutting speed and cutting depth on cutting mechanism and micro-damage evolution were estimated. Cutting force and thrust force obtained by dynamometer were used to evaluate the interaction between the tool and the workpiece. Subsurface damage was assessed by damage depth and failure mode of microstructure such as fiber and matrix. The machined surface roughness was used to characterize the machined surface quality. The results indicated that the average cutting force at θ > 90° was 7.58 times higher than that at θ < 90° and large deformed fibers below the machined surface existed elasticity recovery in the former case. The cutting speed and cutting depth had the most significant effects on the cutting force at θ = 90° where the fiber bending deformation and fiber kinking keep cutting force at a high level. The micromorphology of machined surface and subsurface revealed four typical cutting mechanisms, namely, interface-debonding, fracture-sliding, shearing-fracture, and bending-fracture in the range of θ = 0 ~ 180°. The variation trend of surface roughness with cutting parameters at θ > 90° is obvious and in consistent with that of cutting force. The most efficient factor on the roughness is found to be the fiber cutting angle accounting for 98.60%, followed by the cutting depth (0.55%) and cutting speed (0.25%). The interaction between the factors is not significant according to the results of ANOVA. [ABSTRACT FROM AUTHOR]