Surface quality evaluation for CFRP milling and its impact on the mechanical properties

Wide applications of carbon fiber–reinforced polymer (CFRP) components in modern manufacturing enterprises have led to significant demand in the secondary machining processes. However, the machining surface quality characterization and its impact on the material’s mechanical performance are not fully investigated. In this paper, a quantitative characterization method is proposed for assessing CFRP milling surface quality by combining SEM and image segmentation techniques, which was evaluated using three indices, namely, surface roughness, surface void fraction, and depth of affected zone. Finite element simulation and experiments about side milling of unidirectional CFRP with 90° fiber orientation were conducted to investigate the effects of milling conditions on the resulting surface quality indices. It was found that feed rate and cutting edge radius are two dominant factors that affect the surface void and the depth of affected zone, and the down-milling style is accompanied by greater machining damages due to the difference fiber cutting angle compared with up-milling. Meanwhile, the influence of the above three indices on the tensile and compressive strength of CFRP specimen was also obtained. It is concluded that the depth of the affected zone has a more significant effect on the strength degradation of machined CFRP materials.