The effects of minimum quantity lubrication and cryogenic liquid nitrogen cooling on drilled hole quality in GLARE fibre metal laminates

The cooling technology used in the machining process can influence the surface integrity of aerospace structural components. This study investigates the impact of using cryogenic liquid nitrogen and minimum quantity lubricating coolants on the drilled hole quality in GLARE 2B 11/10-0.4 fibre metal laminates. The hole quality is assessed by inspecting the burr formation on the hole edge of the upper and lower aluminium sheets, and by inspecting the deviation of nominal hole size and circularity. The results were compared with dry (unlubricated) drilling trials from a previous study on GLARE laminates of similar grade. This study also investigates the influence of flow rate and air pressure on the hole quality. The results show that using cryogenic and minimum quantity lubrication coolants can significantly reduce exit burr formation.