Experimental study on drilling mechanisms and strategies of hybrid CFRP/Ti stacks

Abstract

Mechanical drilling has been frequently used for hole making of hybrid CFRP/Ti stacks in order to ensure excellent fastening assembly. Owing to their inhomogeneous behavior and poor machinability, drilling CFRP/Ti stacks in one-shot time has brought great challenges to the modern manufacturing community. Compared to the previous studies on drilling CFRP/Ti, this paper aims to highlight the following aspects: (i) the features of tool-work interaction and machinability classification in the bi-material drilling, (ii) the influences of different cutting sequences on CFRP/Ti drilling responses, and (iii) the effects of different tool geometries/materials on CFRP/Ti drilling performance. The experimental results have shown that the drill geometrical features, which ensure the cutting contacts of the stack combination, have a more significant effect on CFRP/Ti drilling output than tool material composition. The Ti?CFRP drilling strategy promotes higher quality of the machined hole surfaces (e.g., more consistent hole diameters and much better surface finish) with lower Ti burr extents, while the CFRP?Ti drilling strategy reduces only the induced delamination. The experiments discussed in this paper allow besides several recommendations for the cutting sequence selection and drill geometrical design when drilling hybrid CFRP/Ti stacks.