Temperature effects in end milling carbon fiber reinforced polymer composites

The temperatures at the cutting area rise excessively in machining of CFRP due to the low thermal conductivity of the material. And machining damages become aggravated with cutting-area temperatures approaching to the glass transition temperature of resin matrix. Therefore, controlling the cutting-area temperature at the suitable range is remarkably important for improving machining qualities. This article presented experimental investigations into cutting-area temperature influences on cutting force, surface integrity, as well as subsurface quality in end milling of multi-directional CFRP composites, and further discussed cutting mechanism variations. The cutting-area temperatures were controlled under three ranges by employing pressured cryogenic nitrogen gas and no coolants. The machining quality under low temperature in general was better than that under high temperature. Particularly, morphologies under high temperatures indicated fibers were bended to fracture resulting in severe subsurface damages. In contrast, the hardened matrix at low temperatures offered fibers better support, and the composites were easily squeezed to rupture which led to superior cutting performance. However, as the temperature reached extremely low, the cutting force increased dramatically and then could reduce tool life. Thus the suitable temperature range is proposed for the first time in machining CFRP.