Investigation of Drillability of CFRP/Al 7075 Stack

Composite/metal stack materials, which have excellent mechanical properties, are wideyl used in aerospace industry. However, their machining operation is challenging due to two different material. In this study stack materials consisting of CFRP and Al 7075-T6 were drilled with different drilling parematers to investigate delamination defect, thrust force, inner surface roughness of hole and wear of the cutting tool. Cutting speeds of 50 and 200 m/min, feed rates of 0.10 and 0.20 mm/rev were selected as cutting parameters. The materials were drilled respectively in CFRP/Al 7075 and Al 7075/CFRP directions to observe effect of machining direction in the experiments Drilling experiments were carried out with an uncoated 9 mm diameter drill at variable and constant speeds. Experimental results showed that the surface roughness increased with the increase of cutting speed and feed rate, delamination increased in experiments where cutting tool came out of CFRP, thrust force at variable speeds increased and low amount of wear of cutting tool thanks to internal cooling.