Evaluation of cryogenic cooling and minimum quantity lubrication effects on machining GLARE laminates using design of experiments

The current study investigates the influence of applying cryogenic liquid nitrogen cooling and minimum quantity lubrication (MQL) during drilling of glass aluminium reinforced epoxy (GLARE) fibre-metal laminates. Cutting forces, surface roughness, cutting tool condition and post-machining microhardness of the surface of the upper and lower aluminium sheets near the edge of drilled holes were investigated. The findings are also compared with results from previous dry drilling trials of a similar GLARE grade. An analysis of variance ANOVA was carried out to evaluate the impact of cutting parameters, and cooling conditions, and their percentage contributions when drilling GLARE. The use of MQL and cryogenic liquid nitrogen coolants increased the cutting forces; however, they both reduced the surface roughness of machined holes, adhesions and built-up edge formation on the cutting tool compared to dry drilling. Inspection of post-machining microhardness of the upper and lower aluminium sheets near the hole edges showed that it increased when using both coolants.