Hole Quality Observation in Single-Shot Drilling of CFRP/Al7075-T6 Composite Metal Stacks Using Customized Twist Drill Design

Abstract

In the modern aircraft manufacturing industry, the use of fiber metal stack-up material plays an important role. During assembly, these stack-up materials need to be drilled, and single-shot drilling is the best option to avoid misalignments. This paper discusses hole quality in terms of hole edge defects and hole integrity with respect to tool geometry. In this study, tungsten carbide (WC) twist-type drills with various geometric features were fabricated, tested, and evaluated. Twenty custom twist drill bits with primary clearance angles ranging from 6° to 8°, chisel edge angles from 30° to 45°, and point angles from 130° to 140° were fabricated. The CFRP and Al 7075-T6 were stacked up, and a feed rate of 0.05 mm/rev and spindle speed of 2600 rev/min were used for all drilling experiments. The experimental array was constructed using response surface methodology (RSM) to design the experiments. The impact of factors and their importance on hole quality were investigated using analysis of variance (ANOVA). The study demonstrates that the primary clearance angle, followed by the chisel edge angle, is the most important factor determining hole quality. As a function of tool geometry, correlation models between exit delamination and burr height were developed. The findings suggested that, within the range of parameters examined, the proposed correlation models might be utilized to predict performance measures. For drilling CFRP/AL7075-T6 stack material in a single shot, the ideal twist drill geometry was determined to be a 45° chisel edge angle, 8° primary clearance angle, and 130° point angle. For optimum drill geometry, the discrepancy between the expected and actual experiment values was 0.11% for exit delamination and 9.72% for burr height. The findings of this research elucidate the relationship between tool geometry and hole quality in single-shot drilling of composite-metal stacks, and more specifically, they may serve as a useful, practical guide for single-shot drilling of CFRP/Al7075-T6 stack for the manufacture of aircraft.

Characterization of nanocomposite tetrahedral amorphous carbon coated drill bits for improved drilled-hole quality in carbon fiber-reinforced polymer/Al7075-T6 stacks

“…The properties of CFRP used here are as follows; tensile strength is 2723 MPa, elasticity module is 164 GPa, elongation percentage is 1.62, flexural strength is 1500 MPa, interlaminar shear strength is 80 MPa, density is 1.601 g/cm 3 and hardness is 180 HV. 28,29 Cutting tool Due to its excellent wear resistance while drilling abrasive materials like CFRP, a sintered rod of tungsten carbide (WC) was chosen as the drill bit material. Furthermore, WC has the advantage of having a Vickers hardness value (1625 HV) and density (14.35 g/cm 3 ) much higher than those of the workpiece.…”

“…The properties of CFRP used here are as follows; tensile strength is 2723 MPa, elasticity module is 164 GPa, elongation percentage is 1.62, flexural strength is 1500 MPa, interlaminar shear strength is 80 MPa, density is 1.601 g/cm 3 and hardness is 180 HV. 28,29…”

“…A tool with a diameter of 4.85 mm, 45° of chisel edge angle, 6° of primary clearance angle and 130° of point angle was used in this study. 29 The drill bits are manufactured by Gandtrack Asia Sdn. Bhd.…”

A comparative study of hole integrity performance in composite‐metal stacks using coated and uncoated tungsten carbide drill bits

“…The main problem during the drilling of stack up material is the difference in diameters between the materials. This is due to the different material properties, especially the modulus of elasticity of the materials, which contribute to different elastic deformation making it hard to control the diameter between the stack up materials [13]. If the hole in one materials of the stack is undersized (hole diameter < tool diameter) or oversized (hole diameter > tool diameter), a repair process needs to be implemented and that process, generally adds extra time and costs for the assembly process.…”

Numerical and Experimental Study of Crack Propagation in the Tensile Composite Plate with the Open Hole

“…The complexity of the above issue resulting from the possibility of shaping the properties of laminated composites makes this research problem still valid. In the literature one can find studies [20][21][22] which propose solutions to the problem of hole formation in composite materials.…”