Experimental characterization and finite element modeling of critical thrust force in cfrp drilling

Composite laminates are used in many applications in ae-rospace/defense industries due to their high strength-to-weight ratio and corrosion resistance properties. In general, composite materials are hard-to-machine materials which exhibit low drilling efficiency and drilling-induced delamination damage at exit. Hence, it is important to understand the drilling processes for composite materials. This article presents a comprehensive study involving experimental characterization of drilling process to understand the cutting mechanism and relative effect of cutting parameters on delamination during drilling of carbon fiber reinforced plastic (CFRP). Thrust force and torque data are acquired for analyzing the cutting mechanism, initiation and propagation of delamination, and identification of critical thrust force below which no damage occurs. An FE model for prediction of critical thrust force has been developed and validated with experimental results. A [0/90] composite laminate is modeled simulating the last two plies in exit condition and a thin interface layer is inserted in between the plies to capture delamination extent. The tool geometry is modeled as “rigid body” with geometric features of twist drill used in experiments. The tool is indented on the workpiece to simulated tool feeding action into the workpiece. The FE model predicts the critical thrust force within 5% of the experimentally determined mean value.