CFRP grinding under different coolant conditions

Abstract

Carbon fiber reinforced polymers (CFRP) are a class of materials used in various applications such as lightweight construction due to their outstanding physical and mechanical properties. The heterogeneous structure of composite materials makes them more difficult to be machined. Delamination due to machining is a typical quality problem that can ultimately lead to component failure. The high-strength and abrasive carbon fibers cause significant tool wear. The plastic matrix poses a further problem, as it is very temperature-sensitive and hardly thermally conductive. CFRP is usually machined under dry conditions with a geometrically defined cutting edge processes.

This paper investigates the grinding process of CFRP with superabrasive grinding tools in dry condition, Minimum Quantity Lubrication (MQL) and wet lubrication conditions with two different nozzle types. The evaluation is based on the machining forces, delamination on the surfaces and the surface roughness. In addition, the influence of the bond and the abrasive on the machining forces and the wear behaviour of the tools is investigated. The results show that the machining forces depend heavily on the machining conditions. With certain machining parameters, dry machining induces higher process forces than wet machining. In addition, dry and MQL machining causes more residue of the machined material to adhere to the workpiece and tool. The forces and quality of the machined workpieces using minimum quantity lubrication are almost identical to the results of wet machining. From this point of view, minimum quantity lubrication is a good strategy for CFRP grinding. The cleaning effort for the workpieces and the machine should also be taken into the consideration. The chip spaces of vitrified bonded grinding tools tend to be filled with chips caused loading of the wheel. Finally, the study shows that grinding with cooling lubricant outperforms dry machining and results in better quality parts.