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Al-stacked panel by profile measurement technique
Burr assessment of punched holes on Al/CFRP/Al-stacked panel by profile measurement technique
13
N. Ishak, A.B. Abdullah, Z. Samad School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia
13.1 Introduction Composite materials are widely used as alternatives to certain metals in manufacturing applications, particularly in the aerospace industry [1]. Punching is one method used to produce holes, particularly on metal. However, this technology is still new for composites, and there are only a few published works on this topic. Chan et al. [2] proposed the technology and evaluated the effect of die clearance on the quality of the produced holes, while Zain et al. [3] extended the study on various puncher profiles. The precision of the punching process can be influenced by the tool geometry, punching design, and process parameters and can be assessed on the basis of a few criteria, including crack formation, damage of peripheral zone, roundness and dimensional error, surface roughness, and damage of surface layer (e.g., delamination and edge chipping) [4]. Other influencing factors include the hole diameter, cylindricity error, out of diameter, and burr formation [5]. Studies have shown that drill geometry is the major influencing factor on the quality of drilled holes compared with drill size, workpiece thickness, volume fraction, fiber orientation, speed, and feed. All the process parameters, except speed, significantly affect thrust force, while workpiece thickness, drill size, lip angle, and speed significantly affect surface roughness [6]. Fuzzing is the formation of burrs at the entry/exit of the hole due to the uncut fibers during machining, and this machining error can be corrected by further machining [4]. Jin et al. [7] investigated the disfigurement formation and control in drilling carbon fiber-reinforced composites (CFRPs) and found that burrs at the exit are longer and larger than those at the entrance. Deburring may add much cost and time for part assembly [8–10]. Ramulu et al. [11] found that in drilling of composite and titanium stacks, dissimilar mechanical and thermal properties increase the burr height at the exit. Wei et al. [12] studied the parameters that affect interlayer burr formed during dry drilling of metal materials, and they found that preloading pressing force is effective in controlling the formation of burr. Kumar and Krishnaraj [13] investigated the effect of spindle speed and feed rate on burr height in drilling of composite/metal stacks under minimal fluid lubricating conditions. They observed that exit burr decreases with an increase in feed rate. Nakao and Watanabe [14] developed an effective measurement of burr using an image-processing technique. Images of burr produced during hole drilling were captured from the side surfaces with the use of four mirrors arranged Hole-Making and Drilling Technology for Composites. https://doi.org/10.1016/B978-0-08-102397-6.00013-1 © 2019 Elsevier Ltd. All rights reserved.
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around the hole with burr. Rezende et al. [15] studied the effect of drill geometry on burr height during drilling of aluminum/PE sandwich material. They found that tool geometry and feed rate are the most influential parameters. The use of a pilot hole increases the burr height at the exit. They employed a toolmaker microscope to measure the burr height. Bi and Liang [16] conducted burr height measurement during drilling of titanium (Ti) and aluminum (Al) alloy stacked materials. The optimal parameters of spindle speed, feed rate, pressure, and stacking sequence were also identified. They used a toolmaker microscope for burr measurement. Zhang et al. [17] studied hole quality on CFRP/aluminum stacked material produced by drilling based on hole accuracy, roughness, and burr height. The burr height was measured at ×50 magnification using a 3D morphology of white light interferometry instrument (RTEC3D). They observed that drill geometry affects burr formation whereas cutting parameter insignificantly affects it. Isbilir and Ghassemieh [18] studied the drilled hole quality produced on CFRP/Ti stacks. The burr height was measured with the use of a surface profilometer (Mitutoyo SV-602; Mitutoyo, Japan). They found that burr height and width increase with an increase in drill wear. Avila et al. [19] comprehensively reviewed the burr formation on various materials (e.g., metal, composite, and composite/metal stack) and methods (e.g., milling and drilling) from different perspectives. They found that burr is unavoidable but can be controlled. Melkote et al. [10] studied the effect of drilling parameters on interfacial burr formation. Kuo et al. [20] evaluated the hole quality of drilled holes on Ti-64/CFRP/AA7050 stacks based on diametrical accuracy, cylindricality, and burr height at different feed rates and tool coatings. Burr height was measured at the entrance and the exit of the hole at four points around the hole via a level-type dial gauge with a resolution of 0.002 mm. They found that burr is attributed to the enlargement of the corner chamfers and the greater wear of the cutting edge than in the former due to chipping/fracture. Brinksmeier and Fangmann [21] studied the effect of orbital drilling on the burr formation of composite/AA2024 stacks. The study considered different tool geometries, different coatings, different cutting parameters, tool wear, and minimum quantity lubrication. Profile measurement is a method that allows the measurement of a real surface topography with the use of optics with limited depths of field and vertical scanning [22]. The scanned image can be utilized to evaluate a few quality indicators, such as roundness [23], twist springback [24], and geometrical defect [25]. The current study aims to investigate the quality of punched holes on composite material by utilizing the profile measurement technique. The quality assessment focused on the burr formed at the hole exit. This study contributes to literature mainly by determining the effect of fiber orientation, panel thickness, and fiber types on burr amplitude.
13.2 Methodology The research methodology involved three stages: preparation of the composite panel, experimentation, and analysis of the results.
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13.2.1 Preparation of the composite panel The composite used in the experiment is a laminar composite and was prepared using a hand lay-up technique. For stacking, AA7075 with 0.5 mm thickness was used (Fig. 13.1). A total of 18 specimens were prepared with different fiber orientations; as odd numbers (i.e., 1, 3, 5, 7, 9, 11, 13, 15, and 17), representing the orientation of 0 degrees/90 degrees, and even numbers (i.e., 2, 4, 6, 8, 10, 12, 14, 16, and 18) representing the orientation of 90 degrees/0 degrees (Table 13.1).
Fig. 13.1 Cross-sectional view of punched hole. Table 13.1 Specimens prepared for the experiment Orientation Specimen No
0/90 degrees
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
X
Fiber type
90/0 degrees
Glass
X
X X
X
Carbon
X X
X X
X X
X X X
X X
X
X X
X X
X X
X X X X X X X
Hybrid
X X X X X X
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13.2.2 Experimental setup A universal testing machine was used in performing the punching operation. Four punch travel speeds (i.e., 0.5, 1.5, 3, and 5mm/s) were used. The experiment was repeated for different specimens (composite panels with different thicknesses and orientations). The diameter of the puncher was 10±0.5 mm. The setup is shown in Fig. 13.2. The puncher was purposely designed to belong to position the retractable spring and was hardened to 60 HRC.
13.2.3 Specimen analysis The cut edge quality was evaluated on the basis of the burr formation (i.e., amplitude). During the punching process, the maximum load required for successful punching was recorded to observe the load pattern. Then, the specimens were processed using the 3D surface measurement tool called Alicona IFM for image capturing and analysis of the hole quality. Fig. 13.3A shows the line constructed on the captured image to obtain the profile of the burr. The height of the burr was based on the distance between the flat surface of the panel and the peak of the burr, as shown in Fig. 13.3B.
13.3 Results and discussion Table 13.2 shows the entrance and the exit of the holes produced by the punching process. For the tensile test, we divided the observation into two orientations: unidirectional orientations of 0 degrees/90 degrees and 90 degrees/0 degrees. The results showed that the glass fiber with four plies and a unidirectional orientation of 0
Fig. 13.2 Test rig on Instron Series-3367 for punching operation.
Fig. 13.3 The captured image showing (A) the line constructed and (B) the profile measured using 3D surface measurement method on the exit of the hole. Table 13.2 The entry and exit hole of the m aespl
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d egrees/90 degrees presents higher Young’s modulus than does the specimen with an orientation of 90 degrees/0 degrees. A higher Young’s modulus means higher stiffness. This is due to the fiber form included in the samples. On the contrary, a lower Young’s modulus means higher flexibility of the structure.
13.3.1 Punching load In the experiment, we used an aluminum sheet with a thickness of 0.5 mm to form the stack, and we sandwiched the composite panel between the aluminum sheets. Fig. 13.4 shows the effect of the thickness of glass fiber composite panel on the required load (i.e., maximum value required for a complete punching operation). The sample used was made of glass fiber with three plies. The observation was divided into two orientations: 0 degrees/90 degrees and 90 degrees/0 degrees. At a constant speed, the maximum load increases with an increase in the thickness of the composite panel. Fig. 13.5 shows the effect of the thickness of the carbon fiber composite panel on the maximum load. The graph is divided into two orientations: unidirectional orientations of 0 degrees/90 degrees and 90 degrees/0 degrees. Carbon fiber composite presents a high elastic modulus and is rigid. When the thickness of the panel increases and the speed of the punching is constant, the stress required and the maximum load increase thereby completing the punching process. Fig. 13.6 shows the effect of the thickness of the hybrid composite panel on the maximum load. Hybrid composite is a combination of glass fiber and carbon fiber. The graph trend shows that the composite thickness increases with the maximum load. Samples 5 and 6 require the lowest load compared with the other samples due to their thickness, which is low (four plies). Notably, the thicknesses of samples 5 and 6 are 2.22 and 2.27 mm, respectively. 12,000
Maximum load, N
10,000 8000 6000 4000 2000 0 1
7
13
2
0/90° 0.5mm/s
8 90°/0
1.5mm/s
3.0mm/s
5.0mm/s
Fig. 13.4 Effect of glass fiber composite panel thickness on the maximum load.
14
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14,000 12,000
Max. load, N
10,000 8000 6000 4000 2000 0 3
9
15
4
0/90° 0.5mm/s
10
16
90°/0 1.5mm/s
3.0mm/s
5.0mm/s
Fig. 13.5 Effect of carbon fiber composite panel thickness on the maximum load.
14,000 12,000
Max. load, N
10,000 8000 6000 4000 2000 0 5
11
17
6
0.5mm/s
12
18
90°/0
0/90° 1.5mm/s
3.0mm/s
5.0mm/s
Fig. 13.6 Effect of hybrid composite panel thickness on the maximum load.
13.3.2 Burr height The burr height was measured at the hole exit using the profile measurement technique as described in the previous section. Figs. 13.7, 13.8, and 13.9 show the results of burr height for glass fiber composite, carbon fiber composite, and hybrid composite panels, respectively. The specimens were separated into two orientations: unidirectional orientations of (a) 0 degrees/90 degrees and (b) 90 degrees/
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Hole-Making and Drilling Technology for Composites 450 400 Burr height, mm
350 300 250 200 150 100 50 0
1
7
13
1.5mm/s
360.9 330.07
203.81 396.28
217.96 241.01
3.0mm/s
115.46
242.53
203.57
5.0mm/s
350.69
190.62
185.75
0.5mm/s
(A) 350
Burr height, mm
300 250 200 150 100 50 0
2
8
14
1.5mm/s
303.81 168.48
246.09 177.26
254.3 211.32
3.0mm/s
303.65
169.42
181.32
5.0mm/s
212.24
187.23
119.27
0.5mm/s
(B) Fig. 13.7 Burr height versus thickness of glass fiber composite panel (A) unidirectional (0/90 degrees) orientation (B) 90 degrees/0 orientations.
0 degrees. The burr height occurring at the hole exit at low punching speed is larger than that occurring at the hole exit at high punching speed. From the graph, the resulting punching hole is found to possess the highest burr height at a punching speed of 0.5 or 1.5 mm/s. The burr formation is mainly influenced by the ductility of the material and cutting speed. Therefore the punching speed and the thickness
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189
600
Burr height, mm
500 400 300 200 100 0
3
9
15
1.5mm/s
238.21 561.61
246.43 335.63
247.93 390.57
3.0mm/s
419.63
146.33
360.04
5.0mm/s
411.09
138.37
280.14
0.5mm/s
(A) 600
Burr height, mm
500 400 300 200 100 0
4
10
16
124.44 514.55
248.09 260.12
346.6 261.35
3.0mm/s
95.9
234.03
187.04
5.0mm/s
367.84
132.34
191.45
0.5mm/s 1.5mm/s
(B) Fig. 13.8 Burr height versus thickness of carbon fiber composite panel (A) unidirectional (0/90 degrees) orientation (B) 90 degrees/0 orientations.
of the composite panel play a minor role in affecting the burr height. Although low burr height is always preferred, burr formation in the punching process is undesirable. The result of unidirectional orientations of (a) 0 degrees/90 degrees and (b) 90 degrees/0 degrees is inconsistent because the mechanical properties of the composite panels differ due to their thickness.
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Hole-Making and Drilling Technology for Composites 300
Burr height, mm
250 200 150 100 50 0
5
11
17
1.5mm/s
162.65 207.59
176.2 246.78
99.26 153.16
3.0mm/s
95.75
168.29
88.31
5.0mm/s
74.46
184.42
39.58
0.5mm/s
(A)
Fig. 13.9 Burr height versus thickness of hybrid fiber composite panel (A) unidirectional (0/90 degrees) orientation (B) 90 degrees/0 orientations.
13.4 Conclusions and recommendations for future work This work aimed to study the effect of process parameters on the quality of punched holes in composite/metal stacked panels. The mechanical properties of the composite were obtained from tensile test. The maximum punching load is inconsistent when various punching speeds are applied but increases when the thickness of the composite
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191
with aluminum stacked panel increases. Next, the burr height of the produced hole was measured at the hole exit. The diameter measured at the entry of the hole is influenced by tool wear and delamination. The results of the diameter analysis showed that the resulting hole is not perfectly round, and its diameter is slightly different from that of the puncher. The deviation in the diameter can be minimized by producing low delamination ratio with low maximum load. The burr height at the hole exit is high at low punching speed. For future work, other parameters, such as die clearance, stacked metal, and tool wear, will be studied to obtain an improved hole for strong and accurate assembly.
Acknowledgment The authors want to acknowledge Universiti Sains Malaysia for their sponsorship through Research University Grant (Acc. No. 1001/PMEKANIK/814270). For Mr. Fakhrul, who helps in conducting the experiments.
References [1] T. Edward, Composite materials revolutionize aerospace engineering, Ingenia 36 (2008) 24–28. [2] H.Y. Chan, A.B. Abdullah, Z. Samad, Precision punching of hole on composite panels, Ind. J. Eng. Mater. Sci. 22 (2015) 641–651. [3] M.S.M. Zain, A.B. Abdullah, Z. Samad, Effect of puncher profile on the precision of punched holes on composite panels, Int. J. Adv. Manuf. Technol. 89 (2017) 3331–3336. [4] W. Konig, P. Grab, Quality definition and assessment in drilling of fibre reinforced thermosets, Ann. CIRP 38 (1) (1989) 119–124. [5] I.S. Shyha, S.L. Soo, S. Bradley, R. Perry, P. Harden, S. Dawson, Hole quality assessment following drilling of metallic-composite stacks, Int. J. Mach. Tools Manuf. 51 (7-8) (2011) 569–578. [6] B.R.N. Murthy, L.L.R. Rodrigues, N.Y. Sharma, D. Anjaiah, Influence of process parameters on the quality of hole in drilling of GFRP composites—an experimental investigation using DOE, in: International Conference on Mechanical and Electrical Technology, 10-12 September 2010, Singapore, 2010, pp. 87–90. [7] Z.J. Jin, Y.J. Bao, H. Gao, Disfigurement formation and control in drilling carbon fiber reinforced composites, Int. J. Mater. Prod. Technol. 31 (1) (2008) 46–53. [8] X. Rimpault, J.F. Chatelain, J.E. Klemberg-Sapieha, M. Balazinski, Burr height monitoring while drilling CFRP/titanium/aluminium stacks, Mech. Ind. 18 (1) (2017) 114. [9] R. Zitoune, V. Krishnaraj, F. Collombet, Study of drilling of composite material and aluminium stack, Compos. Struct. 92 (2010) 1246–1255. [10] S.N. Melkote, T.R. Newton, C. Hellstern, J.B. Morehouse, S. Turner, Interfacial Burr Formation in Drilling of Stacked Aerospace Materials, in: J.C. Aurich, D. Donfeld (Eds.), Burr—Analysis, Control and Removal, Springer-Verlag, Berlin Heidelberg, 2010, pp. 89–98. [11] M. Ramulu, T. Branson, D. Kim, A study on the drilling of composite and titanium stacks, Compos. Struct. 54 (1) (2001) 67–77.
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[12] T. Wei, H. Jian, L. Wenhe, B. Yin, Z. Lin, Formation of interlayer gap and control of interlayer burr in dry drilling of stacked aluminum alloy plates, Chin. J. Aeronaut. 29 (1) (2016) 283–291. [13] M. Senthil Kumar, A. Prabukarthi, V. Krishnaraj, An experimental investigation on drilling of CFRP/Ti stacks using minimal flow lubricating- (MFL) technique using coated (TiAlN) and uncoated drills, in: 5th International & 26th All India Manufacturing Technology, Design and Research Conference, Assam, India, 2014. 314-1-6. [14] Y. Nakao, Y. Watanabe, Measurements and evaluations of drilling burr profile, Proc. Inst. Mech. Eng. B J. Eng. Manuf. 220 (4) (2006) 513–523. [15] B.A. Rezende, M.L. Silveira, L.M.G. Vieira, A.M. Abrão, P.E. de Faria, J.C.C. Rubio, Investigation on the effect of drill geometry and pilot holes on thrust force and burr height when drilling an aluminium/PE sandwich material, Materials 9 (2016) 774–784. [16] S. Bi, J. Liang, Experimental studies and optimization of process parameters for burrs in dry drilling of stacked metal materials, Int. J. Adv. Manuf. Technol. 53 (2011) 867–876. [17] L. Zhang, Z. Liu, W. Tian, W. andLiao, Experimental studies on the performance of different structure tools in drilling CFRP/Al alloy stacks, Int. J. Adv. Manuf. Technol. 81 (2015) 241–251. [18] O. Isbilir, E. Ghassemieh, Comparative study of tool drilling of CFRP/titanium stack using coated carbide drill, Mach. Sci. Technol. 17 (3) (2013) 380–409. [19] M. Avila, J. Gardner, C. Reich-Weiser, A. Vijayaraghavan, S. Tripathi, D. Dornfeld, Burr minimization strategies and cleanability in the aerospace and automotive industry, SAE Trans. J. Aerospace 114 (1) (2005) 1073–1082. [20] C.L. Kuo, S.L. Soo, D.K. Aspinwall, S. Bradley, W. Thomas, R. M'saoubi, D. Pearson, W. Leahy, Tool wear and hole quality when single-shot drilling of metallic-composite stacks with diamond-coated tools, Proc. Inst. Mech. Eng. B J. Eng. Manuf. 228 (10) (2014) 1314–1322. [21] E. Brinksmeier, S. Fangmann, Burr and cap formation by orbital drilling of aluminum, in: J.C. Aurich, D. Donfeld (Eds.), Burr—Analysis, Control and Removal, Springer-Verlag, Berlin Heidelberg, 2010, pp. 31–45. [22] R. Danzl, F. Helmli, S. Scherer, Focus variation—a robust technology for high resolution optical 3D surface metrology, J. Mech. Eng. 57 (3) (2011) 245–256. [23] A.B. Abdullah, S.M. Sapuan, Z. Samad, H.M.T. Khaleed, N.A. Aziz, Twist springback measurement of autonomous underwater vehicle propeller blade based on profile deviation, Am. J. Appl. Sci. 10 (5) (2013) 515–524. [24] A.B. Abdullah, S.M. Sapuan, Z. Samad, Profile measurement based on focus variation method for geometrical defect evaluation—a case study of cold forged propeller blade, Adv. Mech. Eng. (2014) 874691. [25] A.B. Abdullah, S.M. Sapuan, Z. Samad, Roundness error evaluation of cold embossed hole based on profile measurement technique, Int. J. Adv. Manuf. Technol. 8 (2015) 293–300.
13
N. Ishak, A.B. Abdullah, Z. Samad School of Mechanical Engineering, Universiti Sains Malaysia, Nibong Tebal, Malaysia
13.1 Introduction Composite materials are widely used as alternatives to certain metals in manufacturing applications, particularly in the aerospace industry [1]. Punching is one method used to produce holes, particularly on metal. However, this technology is still new for composites, and there are only a few published works on this topic. Chan et al. [2] proposed the technology and evaluated the effect of die clearance on the quality of the produced holes, while Zain et al. [3] extended the study on various puncher profiles. The precision of the punching process can be influenced by the tool geometry, punching design, and process parameters and can be assessed on the basis of a few criteria, including crack formation, damage of peripheral zone, roundness and dimensional error, surface roughness, and damage of surface layer (e.g., delamination and edge chipping) [4]. Other influencing factors include the hole diameter, cylindricity error, out of diameter, and burr formation [5]. Studies have shown that drill geometry is the major influencing factor on the quality of drilled holes compared with drill size, workpiece thickness, volume fraction, fiber orientation, speed, and feed. All the process parameters, except speed, significantly affect thrust force, while workpiece thickness, drill size, lip angle, and speed significantly affect surface roughness [6]. Fuzzing is the formation of burrs at the entry/exit of the hole due to the uncut fibers during machining, and this machining error can be corrected by further machining [4]. Jin et al. [7] investigated the disfigurement formation and control in drilling carbon fiber-reinforced composites (CFRPs) and found that burrs at the exit are longer and larger than those at the entrance. Deburring may add much cost and time for part assembly [8–10]. Ramulu et al. [11] found that in drilling of composite and titanium stacks, dissimilar mechanical and thermal properties increase the burr height at the exit. Wei et al. [12] studied the parameters that affect interlayer burr formed during dry drilling of metal materials, and they found that preloading pressing force is effective in controlling the formation of burr. Kumar and Krishnaraj [13] investigated the effect of spindle speed and feed rate on burr height in drilling of composite/metal stacks under minimal fluid lubricating conditions. They observed that exit burr decreases with an increase in feed rate. Nakao and Watanabe [14] developed an effective measurement of burr using an image-processing technique. Images of burr produced during hole drilling were captured from the side surfaces with the use of four mirrors arranged Hole-Making and Drilling Technology for Composites. https://doi.org/10.1016/B978-0-08-102397-6.00013-1 © 2019 Elsevier Ltd. All rights reserved.
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Hole-Making and Drilling Technology for Composites
around the hole with burr. Rezende et al. [15] studied the effect of drill geometry on burr height during drilling of aluminum/PE sandwich material. They found that tool geometry and feed rate are the most influential parameters. The use of a pilot hole increases the burr height at the exit. They employed a toolmaker microscope to measure the burr height. Bi and Liang [16] conducted burr height measurement during drilling of titanium (Ti) and aluminum (Al) alloy stacked materials. The optimal parameters of spindle speed, feed rate, pressure, and stacking sequence were also identified. They used a toolmaker microscope for burr measurement. Zhang et al. [17] studied hole quality on CFRP/aluminum stacked material produced by drilling based on hole accuracy, roughness, and burr height. The burr height was measured at ×50 magnification using a 3D morphology of white light interferometry instrument (RTEC3D). They observed that drill geometry affects burr formation whereas cutting parameter insignificantly affects it. Isbilir and Ghassemieh [18] studied the drilled hole quality produced on CFRP/Ti stacks. The burr height was measured with the use of a surface profilometer (Mitutoyo SV-602; Mitutoyo, Japan). They found that burr height and width increase with an increase in drill wear. Avila et al. [19] comprehensively reviewed the burr formation on various materials (e.g., metal, composite, and composite/metal stack) and methods (e.g., milling and drilling) from different perspectives. They found that burr is unavoidable but can be controlled. Melkote et al. [10] studied the effect of drilling parameters on interfacial burr formation. Kuo et al. [20] evaluated the hole quality of drilled holes on Ti-64/CFRP/AA7050 stacks based on diametrical accuracy, cylindricality, and burr height at different feed rates and tool coatings. Burr height was measured at the entrance and the exit of the hole at four points around the hole via a level-type dial gauge with a resolution of 0.002 mm. They found that burr is attributed to the enlargement of the corner chamfers and the greater wear of the cutting edge than in the former due to chipping/fracture. Brinksmeier and Fangmann [21] studied the effect of orbital drilling on the burr formation of composite/AA2024 stacks. The study considered different tool geometries, different coatings, different cutting parameters, tool wear, and minimum quantity lubrication. Profile measurement is a method that allows the measurement of a real surface topography with the use of optics with limited depths of field and vertical scanning [22]. The scanned image can be utilized to evaluate a few quality indicators, such as roundness [23], twist springback [24], and geometrical defect [25]. The current study aims to investigate the quality of punched holes on composite material by utilizing the profile measurement technique. The quality assessment focused on the burr formed at the hole exit. This study contributes to literature mainly by determining the effect of fiber orientation, panel thickness, and fiber types on burr amplitude.
13.2 Methodology The research methodology involved three stages: preparation of the composite panel, experimentation, and analysis of the results.
Burr assessment of punched holes
183
13.2.1 Preparation of the composite panel The composite used in the experiment is a laminar composite and was prepared using a hand lay-up technique. For stacking, AA7075 with 0.5 mm thickness was used (Fig. 13.1). A total of 18 specimens were prepared with different fiber orientations; as odd numbers (i.e., 1, 3, 5, 7, 9, 11, 13, 15, and 17), representing the orientation of 0 degrees/90 degrees, and even numbers (i.e., 2, 4, 6, 8, 10, 12, 14, 16, and 18) representing the orientation of 90 degrees/0 degrees (Table 13.1).
Fig. 13.1 Cross-sectional view of punched hole. Table 13.1 Specimens prepared for the experiment Orientation Specimen No
0/90 degrees
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
X
Fiber type
90/0 degrees
Glass
X
X X
X
Carbon
X X
X X
X X
X X X
X X
X
X X
X X
X X
X X X X X X X
Hybrid
X X X X X X
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13.2.2 Experimental setup A universal testing machine was used in performing the punching operation. Four punch travel speeds (i.e., 0.5, 1.5, 3, and 5mm/s) were used. The experiment was repeated for different specimens (composite panels with different thicknesses and orientations). The diameter of the puncher was 10±0.5 mm. The setup is shown in Fig. 13.2. The puncher was purposely designed to belong to position the retractable spring and was hardened to 60 HRC.
13.2.3 Specimen analysis The cut edge quality was evaluated on the basis of the burr formation (i.e., amplitude). During the punching process, the maximum load required for successful punching was recorded to observe the load pattern. Then, the specimens were processed using the 3D surface measurement tool called Alicona IFM for image capturing and analysis of the hole quality. Fig. 13.3A shows the line constructed on the captured image to obtain the profile of the burr. The height of the burr was based on the distance between the flat surface of the panel and the peak of the burr, as shown in Fig. 13.3B.
13.3 Results and discussion Table 13.2 shows the entrance and the exit of the holes produced by the punching process. For the tensile test, we divided the observation into two orientations: unidirectional orientations of 0 degrees/90 degrees and 90 degrees/0 degrees. The results showed that the glass fiber with four plies and a unidirectional orientation of 0
Fig. 13.2 Test rig on Instron Series-3367 for punching operation.
Fig. 13.3 The captured image showing (A) the line constructed and (B) the profile measured using 3D surface measurement method on the exit of the hole. Table 13.2 The entry and exit hole of the m aespl
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Hole-Making and Drilling Technology for Composites
d egrees/90 degrees presents higher Young’s modulus than does the specimen with an orientation of 90 degrees/0 degrees. A higher Young’s modulus means higher stiffness. This is due to the fiber form included in the samples. On the contrary, a lower Young’s modulus means higher flexibility of the structure.
13.3.1 Punching load In the experiment, we used an aluminum sheet with a thickness of 0.5 mm to form the stack, and we sandwiched the composite panel between the aluminum sheets. Fig. 13.4 shows the effect of the thickness of glass fiber composite panel on the required load (i.e., maximum value required for a complete punching operation). The sample used was made of glass fiber with three plies. The observation was divided into two orientations: 0 degrees/90 degrees and 90 degrees/0 degrees. At a constant speed, the maximum load increases with an increase in the thickness of the composite panel. Fig. 13.5 shows the effect of the thickness of the carbon fiber composite panel on the maximum load. The graph is divided into two orientations: unidirectional orientations of 0 degrees/90 degrees and 90 degrees/0 degrees. Carbon fiber composite presents a high elastic modulus and is rigid. When the thickness of the panel increases and the speed of the punching is constant, the stress required and the maximum load increase thereby completing the punching process. Fig. 13.6 shows the effect of the thickness of the hybrid composite panel on the maximum load. Hybrid composite is a combination of glass fiber and carbon fiber. The graph trend shows that the composite thickness increases with the maximum load. Samples 5 and 6 require the lowest load compared with the other samples due to their thickness, which is low (four plies). Notably, the thicknesses of samples 5 and 6 are 2.22 and 2.27 mm, respectively. 12,000
Maximum load, N
10,000 8000 6000 4000 2000 0 1
7
13
2
0/90° 0.5mm/s
8 90°/0
1.5mm/s
3.0mm/s
5.0mm/s
Fig. 13.4 Effect of glass fiber composite panel thickness on the maximum load.
14
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14,000 12,000
Max. load, N
10,000 8000 6000 4000 2000 0 3
9
15
4
0/90° 0.5mm/s
10
16
90°/0 1.5mm/s
3.0mm/s
5.0mm/s
Fig. 13.5 Effect of carbon fiber composite panel thickness on the maximum load.
14,000 12,000
Max. load, N
10,000 8000 6000 4000 2000 0 5
11
17
6
0.5mm/s
12
18
90°/0
0/90° 1.5mm/s
3.0mm/s
5.0mm/s
Fig. 13.6 Effect of hybrid composite panel thickness on the maximum load.
13.3.2 Burr height The burr height was measured at the hole exit using the profile measurement technique as described in the previous section. Figs. 13.7, 13.8, and 13.9 show the results of burr height for glass fiber composite, carbon fiber composite, and hybrid composite panels, respectively. The specimens were separated into two orientations: unidirectional orientations of (a) 0 degrees/90 degrees and (b) 90 degrees/
188
Hole-Making and Drilling Technology for Composites 450 400 Burr height, mm
350 300 250 200 150 100 50 0
1
7
13
1.5mm/s
360.9 330.07
203.81 396.28
217.96 241.01
3.0mm/s
115.46
242.53
203.57
5.0mm/s
350.69
190.62
185.75
0.5mm/s
(A) 350
Burr height, mm
300 250 200 150 100 50 0
2
8
14
1.5mm/s
303.81 168.48
246.09 177.26
254.3 211.32
3.0mm/s
303.65
169.42
181.32
5.0mm/s
212.24
187.23
119.27
0.5mm/s
(B) Fig. 13.7 Burr height versus thickness of glass fiber composite panel (A) unidirectional (0/90 degrees) orientation (B) 90 degrees/0 orientations.
0 degrees. The burr height occurring at the hole exit at low punching speed is larger than that occurring at the hole exit at high punching speed. From the graph, the resulting punching hole is found to possess the highest burr height at a punching speed of 0.5 or 1.5 mm/s. The burr formation is mainly influenced by the ductility of the material and cutting speed. Therefore the punching speed and the thickness
Burr assessment of punched holes
189
600
Burr height, mm
500 400 300 200 100 0
3
9
15
1.5mm/s
238.21 561.61
246.43 335.63
247.93 390.57
3.0mm/s
419.63
146.33
360.04
5.0mm/s
411.09
138.37
280.14
0.5mm/s
(A) 600
Burr height, mm
500 400 300 200 100 0
4
10
16
124.44 514.55
248.09 260.12
346.6 261.35
3.0mm/s
95.9
234.03
187.04
5.0mm/s
367.84
132.34
191.45
0.5mm/s 1.5mm/s
(B) Fig. 13.8 Burr height versus thickness of carbon fiber composite panel (A) unidirectional (0/90 degrees) orientation (B) 90 degrees/0 orientations.
of the composite panel play a minor role in affecting the burr height. Although low burr height is always preferred, burr formation in the punching process is undesirable. The result of unidirectional orientations of (a) 0 degrees/90 degrees and (b) 90 degrees/0 degrees is inconsistent because the mechanical properties of the composite panels differ due to their thickness.
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Hole-Making and Drilling Technology for Composites 300
Burr height, mm
250 200 150 100 50 0
5
11
17
1.5mm/s
162.65 207.59
176.2 246.78
99.26 153.16
3.0mm/s
95.75
168.29
88.31
5.0mm/s
74.46
184.42
39.58
0.5mm/s
(A)
Fig. 13.9 Burr height versus thickness of hybrid fiber composite panel (A) unidirectional (0/90 degrees) orientation (B) 90 degrees/0 orientations.
13.4 Conclusions and recommendations for future work This work aimed to study the effect of process parameters on the quality of punched holes in composite/metal stacked panels. The mechanical properties of the composite were obtained from tensile test. The maximum punching load is inconsistent when various punching speeds are applied but increases when the thickness of the composite
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191
with aluminum stacked panel increases. Next, the burr height of the produced hole was measured at the hole exit. The diameter measured at the entry of the hole is influenced by tool wear and delamination. The results of the diameter analysis showed that the resulting hole is not perfectly round, and its diameter is slightly different from that of the puncher. The deviation in the diameter can be minimized by producing low delamination ratio with low maximum load. The burr height at the hole exit is high at low punching speed. For future work, other parameters, such as die clearance, stacked metal, and tool wear, will be studied to obtain an improved hole for strong and accurate assembly.
Acknowledgment The authors want to acknowledge Universiti Sains Malaysia for their sponsorship through Research University Grant (Acc. No. 1001/PMEKANIK/814270). For Mr. Fakhrul, who helps in conducting the experiments.
References [1] T. Edward, Composite materials revolutionize aerospace engineering, Ingenia 36 (2008) 24–28. [2] H.Y. Chan, A.B. Abdullah, Z. Samad, Precision punching of hole on composite panels, Ind. J. Eng. Mater. Sci. 22 (2015) 641–651. [3] M.S.M. Zain, A.B. Abdullah, Z. Samad, Effect of puncher profile on the precision of punched holes on composite panels, Int. J. Adv. Manuf. Technol. 89 (2017) 3331–3336. [4] W. Konig, P. Grab, Quality definition and assessment in drilling of fibre reinforced thermosets, Ann. CIRP 38 (1) (1989) 119–124. [5] I.S. Shyha, S.L. Soo, S. Bradley, R. Perry, P. Harden, S. Dawson, Hole quality assessment following drilling of metallic-composite stacks, Int. J. Mach. Tools Manuf. 51 (7-8) (2011) 569–578. [6] B.R.N. Murthy, L.L.R. Rodrigues, N.Y. Sharma, D. Anjaiah, Influence of process parameters on the quality of hole in drilling of GFRP composites—an experimental investigation using DOE, in: International Conference on Mechanical and Electrical Technology, 10-12 September 2010, Singapore, 2010, pp. 87–90. [7] Z.J. Jin, Y.J. Bao, H. Gao, Disfigurement formation and control in drilling carbon fiber reinforced composites, Int. J. Mater. Prod. Technol. 31 (1) (2008) 46–53. [8] X. Rimpault, J.F. Chatelain, J.E. Klemberg-Sapieha, M. Balazinski, Burr height monitoring while drilling CFRP/titanium/aluminium stacks, Mech. Ind. 18 (1) (2017) 114. [9] R. Zitoune, V. Krishnaraj, F. Collombet, Study of drilling of composite material and aluminium stack, Compos. Struct. 92 (2010) 1246–1255. [10] S.N. Melkote, T.R. Newton, C. Hellstern, J.B. Morehouse, S. Turner, Interfacial Burr Formation in Drilling of Stacked Aerospace Materials, in: J.C. Aurich, D. Donfeld (Eds.), Burr—Analysis, Control and Removal, Springer-Verlag, Berlin Heidelberg, 2010, pp. 89–98. [11] M. Ramulu, T. Branson, D. Kim, A study on the drilling of composite and titanium stacks, Compos. Struct. 54 (1) (2001) 67–77.
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[12] T. Wei, H. Jian, L. Wenhe, B. Yin, Z. Lin, Formation of interlayer gap and control of interlayer burr in dry drilling of stacked aluminum alloy plates, Chin. J. Aeronaut. 29 (1) (2016) 283–291. [13] M. Senthil Kumar, A. Prabukarthi, V. Krishnaraj, An experimental investigation on drilling of CFRP/Ti stacks using minimal flow lubricating- (MFL) technique using coated (TiAlN) and uncoated drills, in: 5th International & 26th All India Manufacturing Technology, Design and Research Conference, Assam, India, 2014. 314-1-6. [14] Y. Nakao, Y. Watanabe, Measurements and evaluations of drilling burr profile, Proc. Inst. Mech. Eng. B J. Eng. Manuf. 220 (4) (2006) 513–523. [15] B.A. Rezende, M.L. Silveira, L.M.G. Vieira, A.M. Abrão, P.E. de Faria, J.C.C. Rubio, Investigation on the effect of drill geometry and pilot holes on thrust force and burr height when drilling an aluminium/PE sandwich material, Materials 9 (2016) 774–784. [16] S. Bi, J. Liang, Experimental studies and optimization of process parameters for burrs in dry drilling of stacked metal materials, Int. J. Adv. Manuf. Technol. 53 (2011) 867–876. [17] L. Zhang, Z. Liu, W. Tian, W. andLiao, Experimental studies on the performance of different structure tools in drilling CFRP/Al alloy stacks, Int. J. Adv. Manuf. Technol. 81 (2015) 241–251. [18] O. Isbilir, E. Ghassemieh, Comparative study of tool drilling of CFRP/titanium stack using coated carbide drill, Mach. Sci. Technol. 17 (3) (2013) 380–409. [19] M. Avila, J. Gardner, C. Reich-Weiser, A. Vijayaraghavan, S. Tripathi, D. Dornfeld, Burr minimization strategies and cleanability in the aerospace and automotive industry, SAE Trans. J. Aerospace 114 (1) (2005) 1073–1082. [20] C.L. Kuo, S.L. Soo, D.K. Aspinwall, S. Bradley, W. Thomas, R. M'saoubi, D. Pearson, W. Leahy, Tool wear and hole quality when single-shot drilling of metallic-composite stacks with diamond-coated tools, Proc. Inst. Mech. Eng. B J. Eng. Manuf. 228 (10) (2014) 1314–1322. [21] E. Brinksmeier, S. Fangmann, Burr and cap formation by orbital drilling of aluminum, in: J.C. Aurich, D. Donfeld (Eds.), Burr—Analysis, Control and Removal, Springer-Verlag, Berlin Heidelberg, 2010, pp. 31–45. [22] R. Danzl, F. Helmli, S. Scherer, Focus variation—a robust technology for high resolution optical 3D surface metrology, J. Mech. Eng. 57 (3) (2011) 245–256. [23] A.B. Abdullah, S.M. Sapuan, Z. Samad, H.M.T. Khaleed, N.A. Aziz, Twist springback measurement of autonomous underwater vehicle propeller blade based on profile deviation, Am. J. Appl. Sci. 10 (5) (2013) 515–524. [24] A.B. Abdullah, S.M. Sapuan, Z. Samad, Profile measurement based on focus variation method for geometrical defect evaluation—a case study of cold forged propeller blade, Adv. Mech. Eng. (2014) 874691. [25] A.B. Abdullah, S.M. Sapuan, Z. Samad, Roundness error evaluation of cold embossed hole based on profile measurement technique, Int. J. Adv. Manuf. Technol. 8 (2015) 293–300.