Influence of Milling Process Parameters on the Surface Integrity of CFRP

To improve the performance of mobile vehicles like aircrafts and cars or to increase the performance of wind power plants the intensified lightweight design of structural components comes along with the substitution of metallic materials by composites such as fiber-reinforced plastics. The application of such materials allows no degradation of the components service life and hence no reduction of the surface and component integrity. During machining of such heterogeneous materials, damage to the surface and sub-surface structure can be induced as the machining properties of fibers and matrix differ significantly. In the present study a circumferential milling process of unidirectional CFRP was investigated. For this purpose the cutting parameters and conditions such like cutting speed, fiber orientation and workpiece temperature have been varied. The examination of cross-sectional micro-graphs shows that the damage mechanism as well as the depth of sub-surface damages is strongly dependent on the fiber orientation of the CRFP material. A significant reduction of sub-surface damages was observed for higher workpiece temperatures which could provide a potential for higher process performance by maintaining the components integrity at the same time. Furthermore it was found that higher cutting speeds result in fiber bending in the sub-surface region of the milled surfaces. For lower workpiece temperatures a crucial raise of cutting forces was found.