a b s t r a c tCarbon fiber reinforced polymer (CFRP) usage in the aerospace industry has been steadily increasing due to its superior material properties such as high strength, low weight, high resistance to corrosion, and a low thermal expansion coefficient. In addition, CFRP parts are produced near-net-shape, a process that eliminates rough machining operations. However, machining operations such as drilling, side milling, and slotting are still necessary to give the CFRP parts their final shape. A majority of the studies on machining of CFRP laminates are on drilling. The number of studies on milling of CFRPs is quite limited. In this study, a mechanistic cutting force model for milling CFRPs is proposed based on experimentally collected cutting force data during slot milling of unidirectional CFRP laminates using two different polycrystalline diamond cutters. Cutting force coefficients in radial and tangential directions are calculated as a function of fiber cutting angle. The relationship is represented with simple sine functions. The mechanistic model is shown to be capable of predicting cutting forces during milling of multidirectional CFRP laminates. The experimental milling force measurements and predicted milling forces agree well with each other. Surface milling experiments were also conducted to investigate the relationship between milling forces and surface quality. Some suggestions on surface milling of CFRP laminates are given based on these observations.

Cataloged from PDF version of article.Carbon fiber reinforced plastics (CFRPs) have many desirable properties, including high strength-toweight\ud ratio, high stiffness-to-weight ratio, high corrosion resistance, and low thermal expansion. These\ud properties make CFRP suitable for use in structural components for aerospace applications. Drilling is\ud the most common machining process applied to CFRP laminates, and it is difficult due to the extremely\ud abrasive nature of the carbon fibers and low thermal conductivity of CFRP. It is a challenge for manufacturers\ud to drill CFRP materials without causing any delamination on the work part while also considering\ud the economics of the process. The subject of this study is the drilling of fabric woven type CFRP laminates\ud which are known to be more resistant to delamination than unidirectional type CFRP laminates.\ud The objective of this study is to investigate the influence of double point angle drill geometry on drilling\ud performance through an experimental approach. An uncoated carbide and two diamond coated carbide\ud drills with different drill tip angles are employed in drilling experiments of aerospace quality thick fabric\ud woven CFRP laminates. Force and torque measurements are used to investigate appropriate drilling\ud conditions based on drill geometry and ideal drilling parameters are determined. Tool life tests of the\ud drills were conducted and the condition of the diamond coating is examined as a function of drilling\ud operational parameters. High feed rate drilling experiments are observed to be favorable in terms of drill\ud wear. Feed is observed to be more important than speed, and the upper limit of feed is dictated by the\ud drill design and the rigidity of the machine drill. Hole diameter variation due to drill wear is monitored\ud to determine drill life. At high feeds, hole diameter tolerance is observed to be more critical than hole\ud exit delamination during drilling of fabric woven CFRP laminates.\ud © 2012 Elsevier B.V. All rights reserved

Carbon fiber reinforced plastics (CFRPs) possess desirable material properties that satisfy the aerospace industry's high strength to weight ratio objective. Therefore, CFRPs are commonly used in structural parts, either alone or together with aluminum and titanium alloys. Drilling of CFRPs has been studied extensively in the literature in recent years, with special emphasis on process parameters and delamination. This study identifies mechanical properties of uni-directional CFRPs through drilling tests. Drilling of uni-directional CFRP plates with and without pilot holes has been performed, and cutting and edge force coefficients are identified. A polycrystalline diamond (PCD) drill was used in tests since this type of drill is commonly used in practice. Finally, validation tests on multi directional CFRP laminates have been performed and good results have been obtained. © 2014 CIRP

Carbon fiber reinforced polymers (CFRPs) are known to be difficult to cut due to the abrasive nature of carbon fibers and the low thermal conductivity of the polymer matrix. Polycrystalline diamond (PCD) drills are commonly employed in CFRP drilling to satisfy hole quality conditions with an acceptable tool life. Drill geometry is known to be influential on the hole quality and productivity of the process. Considering the variety of CFRP laminates and available PCD drills on the market, selecting the suitable drill design and process parameters for the CFRP material being machined is usually performed through trial and error. In this study, machining performances of four different PCD drills are investigated. A mechanistic model of drilling is used to reveal trade-offs in drill designs and it is shown that it can be used to select suitable feed rate for a given CFRP drilling process.

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