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SEM image of a borehole wall at af = 300 mm/min and n = 4500 rpm using a AlTiN/TiAlN-coated drill b at f = 300 mm/min and n = 6000 rpm for TiAlN-coated drill
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![Setup of the GLARE® laminate inside the CNC machine [49]](publication/340238006/figure/fig4/AS:873926989193239@1585371839795/Setup-of-the-GLARER-laminate-inside-the-CNC-machine-49_Q320.jpg)
Fibre metal laminates (FMLs) are multilayered metal composite materials currently used in aeronautical structures, especially where fatigue and impact resistance are required. FMLs are produced in large panels and often require assembly using the drilling process for riveting purposes. Hole making is a critical machining process in the joining and...
Citations
... In both cases, FMLs are subjected to secondary operations such as drilling to make holes within the FML structure. It is reported that the number of holes drilled for commercial aircraft assembly varies between 1.5 million and 3 million [11,12]. For the reliable functioning of the assembled part, it is imperative to produce superior surface quality holes, which will result in the mitigation of structural failure due to stress and fatigue. ...
Being a difficult-to-cut material, Fiber Metal Laminates (FML) often pose challenges during conventional drilling and require judicious selection of machining parameters to ensure defect-free laminates that can serve reliably during their service lifetime. Helical milling is a promising technique for producing good-quality holes and is preferred over conventional drilling. The paper compares conventional drilling with the helical milling technique for producing holes in carbon fiber-reinforced aluminum laminates. The effect of machining parameters, such as cutting speed and axial feed, on the magnitude of cutting force and the machining temperature during conventional drilling as well as helical milling is studied. It was observed that the thrust force produced during machining reduces considerably during helical milling in comparison to conventional drilling at a constant axial feed rate. The highest machining temperature recorded for helical milling was much lower in comparison to the highest machining temperature measured during conventional drilling. The machining temperatures recorded during helical milling were well below the glass transition temperature of the epoxy used in carbon fiber prepreg, hence protecting the prepreg from thermal degradation during the hole-making process. The surface roughness of the holes produced by both techniques is measured, and the surface morphology of the drilled holes is analyzed using a scanning electron microscope. The surface roughness of the helical-milled holes was lower than that for holes produced by conventional drilling. Scanning electron microscope images provided insights into the interaction of the hole surface with the chips during the chip evacuation stage under different speeds and feed rates. The microhardness of the aluminum layers increased after processing holes using drilling and helical milling operations. The axial feed/axial pitch had minimal influence on the microhardness increase in comparison to the cutting speed.
... The influence of drilling parameters on thrust force is the same for GLARE as that of other metals and is not affected by fibre orientation. According to the findings, an increase in the feed rate and a decrease in the spindle speed were observed to increase the thrust force [12]. Less damage was observed around the hole when using a lower cutting speed of 1000 rpm, possibly due to the lower cutting temperatures [13]. ...
... The metal sheets function as a backup plate, reducing the likelihood of delamination and deformations around the hole edge at entrance and exit. The tool coating was also found to be an influencing factor in increasing the hole dimensional accuracy [12]. A high feed rate was found unsuitable for drilling of GLARE laminate as it increases the tool vibration and defection in the workpiece, causing an increase in circularity error [15]. ...
... The deviation from nominal hole size ranged between − 2 µm and +8 µm at the top, and between − 19.3 µm and +7 µm at the bottom. These ranges are lower than those that were reported in earlier research on CD of GLARE laminates [11,12,63]. Of course, other factors might have contributed to the hole size in those previous studies which are not studied here such as the use of coolants, drill size, geometry, and coating. ...
... Drill coatings have a significant impact on drilling aeronautical multi-materials comprised of composites and metals because they can increase surface polish and extend drill life. [27] To acquire the empirical model and to optimize the process parameters, drilling operations utilizing HSS have been performed in the Mg AZ31. The author observed that Circularity, Perpendicularity, and Cylindricity depend on Spindle speed, Feed rate, and Drill diameter [28] This article describes an experimental study and analysis of electrical discharge machining (EDM) of the super alloys Inconel 718 and 625. ...
... Compared with the binary deposit Zn-Ni and Zn-Co, the ternary Ni-Cr-Co deposit is found to have more Ni and Co concentration, as higher current density (500-550 A·ft −2 ) followed [40][41][42]. The reason for higher Ni and Co content in the ternary coating is the synergistic catalytic effect in the electrolyte bath [43][44][45]. ...
The aluminum (Al) alloy AA7075 is widely used in various industries due to its high strength-to-weight ratio, which is comparable and replaceable to steel in many applications. However, it has poor resistance to wear and corrosion compared to other Al alloys. The conventional pressure die coating with Cr and cadmium has led to premature failure while the load is applied. It is indeed to develop a novel coating method to improve the mechanical, wear, and corrosion properties of AA7075 Al alloy. In the present investigation, the binary and ternary metals such as zinc–nickel (Zn–Ni), zinc–cobalt (Zn–Co), and nickel–chromium–cobalt (Ni–Cr–Co) are electroplated on the substrate material (AA7075). In order to ensure optimal coating adhesion, the surface of the substrate material was pre-treated with laser surface treatment (LST). The mechanical and corrosion studies have been carried out on the uncoated and coated materials. It is observed from the findings that the ternary coating has higher wear resistance than the binary-coated material. The ternary coating has 64% higher resistance in the non-heat-treated status and 67% higher resistance in the heat-treated condition compared to the uncoated specimens. The tensile strength (MPa) of Ni–Cr–Co on AA7075 pressure die casting (PDC) is higher than the other deposits (582.24 of Ni–Cr–Co > 566.07 of Zn–Co > 560.05 of Zn–Ni > 553.64 of uncoated condition). The presence of a crystalline structure with the high alignment of Co and Ni atoms could significantly improve the corrosion resistance of Ni–Cr–Co coatings on AA 7075 PDC substrates when compared to binary coatings. The scanning electron microscopy (SEM) images, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy findings on the coated materials have been corroborated with the analyses on mechanical and corrosion properties. The XRD analysis of the Zn–Ni binary coating has reported that the diffraction peaks of γ-NiZn3 (831), γ -Ni2Zn11 (330), and 631 with 2θ values 38, 43, and 73° are confirming the presence of Zn–Ni binary deposit on AA7075 PDC substrate. The XRD pattern of Zn–Co-coated material has revealed that the presence of three strong peaks such as Zn (110), Co (111), and CoZn (211) and two feeble peaks such as ε-CoZn3 (220) and ε-CoZn3 (301) are clearly visible. The XRD pattern of Ni–Cr–Co ternary coating has exhibited that the Ni–Cr–Co ternary deposit is a solid solution with a body-centered cubic structure due to the formation peaks at lattice plane such as (110), (220), and (210) with a crystal lattice constant of 2.88 A°. The SEM image for both the binary- and ternary-coated materials has exhibited that the deposited surface has displayed many shallow pits due to hitting by progressive particles. The SEM image has illustrated the presence of Zn–Ni atoms with smaller globular structure. The surface morphology of binary Zn–Co coating on the PDC AA7075 substrate has unveiled the evenly distributed dot-like structure and submerged Co particles in the galaxy of Zn atoms. To understand the effectiveness of bonding by laser texturing, cross-section SEM has been carried out which furthermore revealed the effective adhesion of Ni–Cr–Co on AA7075 PDC; this could also be the reason for the enhancement of microhardness, wear, and corrosion resistance of the said coating.
... Components of aeronautical structures are generally assembled using fasteners (rivets or screws) introduced into holes made using a drilling process. The number of holes needed for an aircraft structure is very high and can vary from several hundred thousand to several million, depending on the size of the aircraft [52][53][54][55][56][57][58][59][60][61][62]. As an example, on the AIRBUS A380 and FALCON DASSAULT F7X, the number of holes to be made are approximately 2,000,000 and 20,000, respectively, with a distribution of approximately 70% of them in the aluminum structure, 25% in the composite structure, and the remaining 5%, in the titanium structure [63]. ...
Composite material consumption is booming and is expected to increase exponentially in many industrial applications such as aerospace, automotive, marine and defense. However, in most cases, composite products require further processing before they can be used or assembled. Machining of composite materials is extremely difficult due to their anisotropic and non-homogeneous structure. This paper provides a comprehensive review of the literature on composite materials and their machining processes, such as turning, milling and drilling. Damage related to these processes is also discussed. The paper is divided into seven main parts; the first, second and third parts give a brief overview of composite materials, reinforcements used in composite materials and composite manufacturing methods, respectively. The fourth part deals with post-processing machining operations, while the fifth, sixth and seventh parts are devoted to the machining of carbon fiber reinforced polymer composite, glass fiber reinforced polymer and natural fiber reinforced polymer composites, respectively. An analysis of the factors that influence the machining and the machinability criteria used for these materials is also presented, with particular emphasis on cutting forces, tool wear, delamination and surface finish. Non-traditional manufacturing methods are not discussed in this paper.
... Detailed statistical analysis of existing trends in the evaluation of various process conditions (Ref. Fig. 11) highlights that there has been a tendency to define or describe the drilling process via the characterization of thrust force and torque [43,62,85,99,101,123,132,135,143,[156][157][158][159][160][161], delamination [43,52,62,99,114,115,119,123,132,134,135,156,[162][163][164], drilling temperature [9,10,28,30,31,44,64,76,96,97,113,120,128,129,131,135,137,142,143,150,151,157,163,[165][166][167][168][169][170] and other process conditions. A more detailed discussion of effects of process conditions on various aspects of the drilling procedure is proposed in the following subsections. ...
CFRP/Ti stacks have attracted considerable attention over the past decades as a promising alternative to individual fibrous composites and metallic alloys due to their improved properties and enhanced structural functions. Mechanical drilling is a compulsory but challenging process to shape these compound stacks to desired dimensions and target quality. Despite a large volume of studies already addressing the conventional twist drilling of CFRP/Ti stacks, a comprehensive understanding of their fundamental drilling mechanisms is still lacking. The present paper aims to report the state-of-the-art advances achieved in the fields of CFRP/Ti machining. Aspects including chip removal, damage formation, mechanical/thermal effects, influences of process conditions, hole quality attributes, and tool wear mechanisms are carefully reviewed. An emphasis is placed on the discussion of the interface drilling behaviors as well as the impacts of different drilling sequence strategies on the machining outputs of CFRP/Ti stacks. The current research limitations and future research perspectives are pointed out. The review paper could provide technical guidance for both scientific and industrial communities to achieve the damage-free drilling of CFRP/Ti stacks.
... From a study performed with these three coatings, the TiAlN drills produced the largest thrust and cutting forces, with the AlTiN/TiAlN resulting in the lowest values. Additionally, this coating presented a better self-lubricating effect due to its multilayer structure, which also increases its hardness, resulting in a better performance achieved during drilling [97]. coating presented a better self-lubricating effect due to its multilayer structure, which also increases its hardness, resulting in a better performance achieved during drilling [97]. ...
... Additionally, this coating presented a better self-lubricating effect due to its multilayer structure, which also increases its hardness, resulting in a better performance achieved during drilling [97]. coating presented a better self-lubricating effect due to its multilayer structure, which also increases its hardness, resulting in a better performance achieved during drilling [97]. Diamond CVD coatings are many times chosen as well, due to their enhanced characteristics when compared to the remaining options, although sometimes they experience some lack of adhesion. ...
Composite materials such as Fiber Metal Laminates (FMLs) have attracted the interest of the aerospace and automotive industries due to their high strength to weight ratio, but to use them as structures it is necessary to master the manufacturing and wiring techniques of these materials. Therefore, this paper aims to address and summarize the drilling and milling processes in FMLs based on a literature review of papers published from 2000 to 2023. Parameters used in multi-material manufacturing and machining such as drilling and milling, tool geometry, tool coating, lubricants and coolants published by researchers were analyzed, compared and discussed. Machining process parameters related to sustainability were also analyzed. A SWOT analysis was carried out and discussed to identify opportunities for improvement in the machining process. There are opportunities to develop the surface treatment of aluminum alloys, such as testing other combinations than those already used, testing non-traditional surface treatments and manufacturing modes, and developing sustainable techniques during the FML manufacturing process. In the area of tooling, the opportunities are mainly related to coatings for tools and changing machining parameters to achieve an optimum finished part. Finally, to improve the sustainability of the process, it is necessary to test coated drills under cryogenic conditions to reduce the use of lubricants during the machining process.
... It might be preferable to utilize a support on the interior of the pipes while drilling process in order to minimize damages, keeping into mind the damage creation, particularly at the hole exit. Another interesting study [81] of coatings over drill tools has significantly affected the hole dimension and circularity. The coated drill also have a significant impact on drilling aeronautical distinct materials comprised of metal and composites because they may increase surface quality and extend tool life. ...
Fiber-reinforced polymer (FRP) composites play a vital role in the production of structural and semi-structural components for engineering applications. The drilling process is a commonly employed machining process for FRP composites to join the FRP structural elements. Usually, the FRP composites possess a heterogeneous nature because of their multi-layered structure, hybridization, and the presence of multi-phase materials. Hence, common problems like delaminations, fuzzing, buckling, cracking, matrix and fiber burning occur during the drilling operations. These problems cause dimensional inaccuracy, poor surface finish, and tool wear and reduce the mechanical strength of the composites. The optimum drilling parameters (drill geometry, speed, feed, and depth of cut) selection for the specific materials is good to achieve effective drilling performance and better surface quality of the holes. Yet, little study has been done on how all of these factors affect the size of the drilled hole. The majority of drilling studies on FRPCs in the past have focused on how to improve the hole quality by maximizing processing conditions, and there has been little discussion on the correlation between drilling conditions, physical properties, and production techniques. This is what motivated to review the characteristics and properties analysis of FRP composites. As a consequence of this research, it is anticipated that scientists and researchers would place a greater emphasis on the drilling characteristic of the workpieces made from FRPCs than on other attributes. This review clearly presents an overview of FRP composites drilling that had progressed from 2000 to 2021. The analysis of different drilling conditions and parameters like thrust force, drill geometry, temperature, speed, and feed also includes the post-drilling analysis through delaminations, thermal damage, and surface roughness. Furthermore, the recent developments in carbon, glass, and natural fiber reinforced polymer composites are studied with both conventional and nonconventional drilling techniques. Based on the above studies, some future challenges and conclusions are drawn from this review.
... It is possible that the heightened friction and interaction between the tool-workpiece interface resulted in elevated boundary temperatures. Adding a larger wt% fraction of rGO nanofiller or failing to maintain optimum feed rate or drilling speed tends to aggravate the maximum extent of matrix depletion and smearing [92][93][94]. ...
The damages and imperfections in the drilled holes might cause excessive strains on the rivet and lead to assembly failure. One of the most common forms of damage in machined Carbon fiber-reinforced plastic (CFRP) composites is the burr formation and irregular machined surface. This current study investigates the effect of different loading of reduced Graphene Oxide (rGO) nanoflakes in modified CFRPs on the quality indices of drilled holes, including burr formation at the exit, surface roughness, and cutting forces. The Box-Behnken experimental design (BBD) was employed to conduct the drilling investigation on rGO-modified CFRP (CF/rGO) nanocomposite. The samples were prepared at three different (0.5,1.0,1.5%) weight fractions of rGO nanofiller material, and the effect of varying parameters, like drilling speed and feed rate was investigated. Digital image processing (DIP) was utilized to examine the factors contributing to burr formation at the exit of drilled holes, as measured by the Burr Area Factor (BAF). The analysis of variance (ANOVA) revealed that the rGO wt% and feed rate is the most prominent parameter while the drilling process. The optimal parametric condition was obtained as rGO wt% = 1.0%, Drill speed = 1800 rpm, and feed rate = 60 mm/min, while the optimum responses resulted in Thrust force = 36.716 N, Torque = 0.181 Nm, Surface Roughness = 1.120 μm, and Burr area factor = 0.108. In addition, these results demonstrated that a moderate rGO wt% loading, a higher drill speed, and a lower feed rate could produce the minimal Thrust force, Torque, Surface Roughness, and Burr area factor simultaneously. Further, the Scanning electron microscopy (SEM) findings were used to evaluate the outcomes of the optimum setting.
... The hole accuracy attained here was in accordance with industry standards. This means the diameter tolerances fell within the range of the H8 zone, i.e., 18 µm [31,51]. The evaluation of the hole diameter error is shown in Figure 18 for both CFRP and Al7075-T6 plates. ...
... The hole accuracy attained here was in accordance with industry standards. This means the diameter tolerances fell within the range of the H8 zone, i.e., 18 μm [31,51]. The evaluation of the hole diameter error is shown in Figure 18 for both CFRP and Al7075-T6 plates. ...
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.
Keywords:
single-shot drilling; CFRP/Al stacks; hole quality; optimization; twist drill; ANOVA
