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CARBONLETT, vol. 23, no. 1, pp.1-8, 2017

DOI: http://dx.doi.org/ DOI:10.5714/CL.2017.23.001

Hole quality assessment of drilled CFRP and CFRP-Ti stacks holes using polycrystalline diamond (PCD) tools

Dave Kim1, Aaron Beal2, Kiweon Kang3 and Sang-Young Kim3,♠

Affiliation: 1School of Engineering and Computer Science, Washington State University, Vancouver, WA 98686, USA
2Epic, Verona, WI 53593, USA
3School of Mechanical, Automotive, Naval Architecture and Ocean Engineering, Kunsan National University, Gunsan 54150, Korea

Abstract: Polycrystalline diamond (PCD) tools possessing high hardness and abrasive wear resistance are particularly suited for drilling of carbon fiber reinforced plastic (CFRP) composites, where tool life and consistent hole quality are important. While PCD presents superior performance when drilling CFRP, it is unclear how it performs when drilling multi-stack materials such as CFRP-titanium (Ti) stacks. This comparative study aims to investigate drilling of a Ti plate stacked on a CFRP panel when using PCD tools. The first sequence of the drilling experiments was to drill 20 holes in CFRP only. CFRP-Ti stacks were then drilled for the next 20 holes with the same drill bit. CFRP holes and CFRP-Ti stack holes were evaluated in terms of machined hole quality. The main tool wear mechanism of PCD drills is micro-fractures that occur when machining the Ti plate of the stack. Tool wear increases the instability and the operation temperature when machining the Ti plate. This results in high drilling forces, large hole diameter errors, high surface roughness, wider CFRP exit thermal damage, and taller exit Ti burrs.

Keyword: polycrystalline diamond, carbon fibers, carbon composites, mechanical properties, surface properties