Wet Milling of Cfrp

Abstract

Carbon-fibre-reinforced polymers (CFRP) have been steadily gaining relevance for several decades. According to Composite Materials e.V., CFRPs will continue to be an important economic influence in the future, particularly due to the increasing production of wind turbines. Despite near-component production, machining of the material - and thus the machinability of it - is necessary for the creation of the final product. Machinability is complicated by the temperature response of CFRP and the severe wear of cutting tools.

The aim of the project was to improve the machinability by using cooling lubricant. For this purpose, suitable components and additives were determined. From these, cooling lubricants were formulated and tested in a series of swelling and machining trials.

The machined samples were examined for chipping, fraying, delamination and cleanability. Especially tool life, cutting edge rounding, machining quality and machining performance were taken into consideration to evaluate the cooling lubricants. A mineral oil-based cooling lubricant with increased pH-values and the additive produce very good machining results in terms of component quality. As expected, the machined surfaces with cut fibres proved harder to clean than the smooth polymer surfaces.

Our cost calculation in comparison to established machining methods for CFRP generally proves the economic-effectiveness of using cooling lubricants. However, costs should be evaluated for each individual product line and its corresponding operation and certification requirements.

The objectives developed in the requirements analysis were achieved in cooperation between the institutes Fraunhofer IPA and Fraunhofer IGB.

Keywords: CFRP wet milling, cooling fluids