- Email: [email protected]
Machinability of glass fibre reinforced plastic (GFRP) composite using alumina-based ceramic cutting tools
Journal of Manufacturing Processes 13 (2011) 67–73
Contents lists available at ScienceDirect
Journal of Manufacturing Processes journal homepage: www.elsevier.com/locate/manpro
Review
Machinability of glass fibre reinforced plastic (GFRP) composite using alumina-based ceramic cutting tools M. Adam Khan ∗ , A. Senthil Kumar Department of Production Engineering, Sethu Institute of Technology, Virudhunagar Dist., Tamil Nadu, India
article
info
Article history: Received 24 August 2009 Received in revised form 18 August 2010 Accepted 1 October 2010 Available online 27 October 2010
abstract This paper deals with the machining of glass fibre reinforced plastic (GFRP) composite material. GFRP composite material was fabricated in our laboratory using E-glass fibre with unsaturated polyester resin. GFRP composite specimens were prepared using a filament winding process. Machining studies were carried out using two different alumina cutting tools: namely, a Ti[C, N] mixed alumina cutting tool (CC650) and a SiC whisker reinforced alumina cutting tool (CC670). The machining process was performed at different cutting speeds at constant feed rate and depth of cut. The performance of the alumina cutting tools was evaluated by measuring the flank wear and surface roughness of the machined GFRP composite material. An attempt is made to analyse the main wear mechanism of alumina cutting tools while machining GFRP composite material. © 2010 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
Contents 1. 2.
3.
4.
Introduction........................................................................................................................................................................................................................ Experimental procedure .................................................................................................................................................................................................... 2.1. Preparation of GFRP composite rod ...................................................................................................................................................................... 2.2. Machining study .................................................................................................................................................................................................... Result and discussion......................................................................................................................................................................................................... 3.1. Flank wear of the alumina cutting tool ................................................................................................................................................................ 3.2. SEM observation and wear mechanism ............................................................................................................................................................... 3.3. Surface roughness.................................................................................................................................................................................................. 3.4. Cutting force........................................................................................................................................................................................................... Conclusion .......................................................................................................................................................................................................................... References...........................................................................................................................................................................................................................
1. Introduction GFRP composite material was developed to meet the requirements of the industry for high- strength materials with low weight. The advantages of GFRP material include savings in weight, improvement in strength and decreased cost of material and fabrication. Glass fibre reinforced composites have been used for engineering applications, and various types of glass fibres are used as reinforcements. E-glass fibres are widely used as they have special characteristics such as high strength to weight ratio, good dimensional stability, good resistance to heat, cold, moisture, and corrosion, and good electrical insulation properties. The concept of incorporating a strong fibre or whiskers into a tough or ductile
∗
Corresponding author. Tel.: +91 9843361274; fax: +91 4566308000. E-mail address: [email protected] (M. Adam Khan).
67 68 68 69 69 69 69 71 72 72 72
matrix yields a very high strength to the composite as they carry load [1–4]. Machining glass fibre composite is still a major problem, because of their inert nature, high hardness, and refractoriness [5]. Because of their different applications, the need for machining FRP material has not been fully eliminated. Glass fibre reinforced plastics (GFRPs) are extremely abrasive; thus proper selection of the cutting tool and cutting parameters is very important for a perfect machining process [6]. The mechanism of machining GFRP composite is quite different from that of metals [7–9]. While machining a GFRP, the strong fibre materials cause rapid tool wear and poor surface finish. Tool wear reduction is an important aspect in machining GFPR composites [10]. The surface integrity of a GFRP machined composite is hard to control, including surface roughness, residual stresses and subsurface damages due to varying mechanical properties of the fibre and the matrix [11]. Santhanakrishnan et al. [12] reported that the mechanisms associated with machining of GFRP composite are plastic deformation, shearing,
1526-6125/$ – see front matter © 2010 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jmapro.2010.10.002
68
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
Fig. 1. E-glass fibre reinforced composite rod. Table 1 Properties of E-glass fibre roving. Material
Density (g/cm3 )
Tensile modulus ksi (GPa)
Tensile strength ksi (Mpa)
Tensile strain (%)
E-glass fibre roving (2400 m/kg)
2.6
11,000 (76)
500 (3450)
4.7
and rupture of fibres orientation. Fibre orientation is an important criterion which affects the machining process and strength of the composite [13,14]. Sharma et al. [15] stated that wear performance of the cutting tool decreases with 90° fibre orientation. Sreejith et al. [16] observed that the cutting force and the cutting temperature affect the performance of the cutting tools while machining carbon/carbon composites. Davim et al. [17] used a polycrystalline diamond (PCD) cutting tool to machine FRP tubes and obtained optimal cutting parameters for surface roughness. Sreejith et al. [18] evaluated the performance of a PCD cutting tool while machining carbon/phenolic composite material, by observing the tool wear, cutting force, and cutting temperature. Fereirra et al. [19] also reported that a diamond tool could be used for finish machining as it produced low surface roughness with minimum tool wear. Rahman et al. [20] conducted machining studies on a carbon fibre reinforced plastic (CFRP) composite using various advanced cutting tools and found that PCD tools exhibited high wear resistance. Ulhmann et al. [21] conducted a machining study using diamond-coated carbide and ceramic cutting tools on FRP material, and observed that the diamond-coated carbide and ceramic cutting tools exhibited high wear resistance and high tool life. An alumina-based ceramic cutting tool is one of the attractive alternative cutting tools for machining hard materials [22]. Ceramic cutting tools are cost effective and able to produce a good surface finish at higher cutting speed. Alumina-based ceramic cutting tools are persistently used to machine hard materials, as they can withstand high hot hardness up to 1500 °C with chemical stability [23]. Xu et al. [24] developed an Al2 O3 /Ti[C, N]/SiC whisker cutting tool and conducted machining studies on hard materials, and found that such multiphase ceramic cutting tools have good wear resistance. While machining hard materials, the wear morphology of the alumina cutting tool indicated plastic deformation along with mild abrasion and small glassy deposits were observed [25,26]. Aslan et al. [27] reported that the tool wear of an Al2 O3 mixed ceramic tool decreased almost linearly with cutting speed during hard turning of AISI 4140 steel. Afaghani et al. [28] stated that the presence of whiskers in a composite material resists the extension of crack propagation during machining. A SiC whisker reinforced alumina cutting tool can produce a twofold increase in fracture toughness and it has received widespread acceptance in the aerospace industry, where it is regarded as the state-of-the-art cutting-tool material for the finishing and rough machining of nickel-based superalloys because of its high wear resistance and fracture toughness [29]. Deng et al. [30] made an attempt to machine a nickel-based alloy using Al2 O3 /TiB2 /SiCw ceramic cutting tools and found that the composite tool materials with higher SiC whisker content showed better wear resistance. Abrasive wear was found to be
the predominant flank wear mechanism while machining nickelbased alloy. Aslan [31] made an attempt to machine hard materials using cubic boron nitride (CBN), Al2 O3 + Ti[C, N] cutting tool, coated cermet cutting tool and carbide cutting tool. From the investigation, it is found that the Al2 O3 + Ti[C, N] cutting tool and CBN exhibit better performance and higher tool life than coated cermet and carbide cutting tools. Cutting force analysis plays a vital role in studying the machining process of FRP materials [32]. In general, FRP materials are inhomogeneous, as the reinforcement has anisotropic characteristics. They consist of a load-carrying fibre component which appears as a bundle of fibres, which leads to difficulties in the machining process. In this regard, the cutting force is an important dependent variable of the machining system and it has been investigated by many researchers in various cutting processes. The range of cutting force also varies with respect to the fibre orientation and fibre–matrix volume fraction. In this study, the cutting force along with surface roughness and tool wear were measured on machining GFRP composite materials. It can be observed from the literature that polycrystalline diamond (PCD), cubic boron nitride (CBN), and polycrystalline cubic boron nitride (PcBN) are widely used to machine GFRP materials. Though ceramic cutting tools are cheaper than PCD and PcBN tools, they provide equivalent performance on machining hard materials. However, the performances of ceramic cutting tools have not been evaluated properly on machining GFRP materials. Hence, machining studies have been conducted on GFRP materials using a Ti[C, N] mixed alumina cutting tool and a SiC whisker reinforced alumina cutting tool; the GFRP composite was prepared using unsaturated polyester resin with E-glass fibre as reinforcement. 2. Experimental procedure 2.1. Preparation of GFRP composite rod The GFRP composite rod was prepared in our laboratory. Eglass fibre is chosen for its excellent properties (Table 1), and its composition is presented in Table 2. The glass fibre roving was made to pass through an unsaturated polyester resin bath to get wet and it was wound with a fibre orientation angle of 90° on a steel rod having a diameter of 15 mm. Fig. 1 shows the GFRP composite rod with a steel rod at the centre. The composite was cured for two hours to get the required strength. The GFRP rod of 65 mm diameter and 400 mm length was cut so that it could be held in between the centers in a precision lathe for the machining study. Fig. 2 shows a scanning electron microscope (SEM) micrograph of GFRP composite prepared using the filament winding process. From the SEM picture, it can be noted that the glass fibres are strongly bonded and homogeneously impregnated with the polyester matrix material.
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
69
Table 2 Composition of E-glass fibre. Composition Content %
SiO2 52%–56%
AlO2 12%–16%
CaO 16%–25%
B2 O3 8%–13%
Fig. 3. Flank wear versus machining time of alumina cutting tools while machining GFRP composite.
Fig. 2. SEM micro graph of GFRP composite.
2.2. Machining study Machining studies were carried out to machine GFRP composite material in a precision lathe using a Ti[C, N] mixed alumina cutting tool (CC650) and a SiC whisker reinforced alumina cutting tool (CC670). The properties of both the alumina-based ceramic cutting tools are given in Table 3. The machining process was performed with various cutting speeds at constant feed rate and depth of cut. Flank wear and surface roughness were observed during machining of the GFRP composite. The flank wear was measured using a Metzer Toolmakers microscope, the surface roughness (Ra ) was measured using a TR200 surface profile meter, and the cutting force was measured using a strain gauge type dynamometer. 3. Result and discussion 3.1. Flank wear of the alumina cutting tool Tool wear is one of the most important criteria in machining processes; it directly affects the tool life, surface quality, and production cost. Tool wear in machining FRP composite material occurs due to the rubbing of the cutting tool edge with the hard fibres impregnated in the matrix materials. While machining FRP composite material, flank wear is the main form of wear, as other forms of tool wear are negligible. Fig. 3 shows the variation of flank wear with respect to machining time while machining GFRP composite material using the Ti[C, N] mixed alumina cutting tool (CC650) and the SiC whisker reinforced alumina cutting tool (CC670) at 250 m/min. Fig. 4 shows the flank wear versus cutting velocity of the alumina cutting tools after 6 min of machining. The flank wear of the alumina cutting tool increases with respect to speed and machining time and it is higher at higher cutting speeds. The main wear mechanism is abrasion. The glass fibre in the GFRP composites abrades with the cutting tool and removes some of the tool material at the flank face. The wear by abrasion is usually due to the crack development, and the intersection caused by hard fibre chips acting as small indenters on the cutting face. The broken fibres during machining cause further wear at the tool chip interface. As the cutting speed increases, the velocity of abrasion increases, and the rate of contact of broken fibre chips
Fig. 4. Flank wear versus cutting velocity of alumina cutting tools while machining GFRP composite at 6 min.
also increases, leading to a higher flank wear at high speed. Chip formation while machining GFPR materials is an important factor in addition to fibre orientation, fibre delamination, and direction of machining. The fracture of fibre chips causes extreme damage to the cutting tool through abrasion, causing to the development and growth of flank wear. The fibre fracture is due to the combination of crushing and bending caused by the machining process. The broken fibres can be observed from the SEM micrograph, along with the chips of matrix material (Fig. 5). The presence of broken fibres as seen in the SEM micrograph contributes to the abrasive wear. From Fig. 3, it can be noted that the Ti[C, N] mixed alumina cutting tool fails after 8 min of machining at 250 m/min as it crosses the failure criterion for flank wear (i.e. 0.4 mm wear for finish machining). Tool failure of the Ti[C, N] mixed alumina cutting tool occurs after 6 min of machining at 300 m/min; however, the SiC whisker reinforced alumina cutting tool approaches tool failure after 9 min. 3.2. SEM observation and wear mechanism Machining of GFRP material is quite different from machining of metals. Fibre orientation and the cutting tool geometry will have significant contributions in machining fibre composite material. While machining, the interface of the cutting tool and work material is subsequently made to shear if it is ductile and the
70
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
Table 3 The properties of the alumina-based ceramic cutting tool materials. Details of tool material
Unit
Ti[C, N] mixed alumina (CC650)
SiC whisker reinforced alumina (CC670) Al2 O3 80% SiCw 20%
g/cm3 (HV10) MPa GPa MPa m1/2 W/mK K−1 .10−6
Al2 O3 70% TiN 22.5% TiC 7.5% 4.26 1800 550 400 4.0 24 8.6
Composition Density Vickers hardness Transverse rupture strength Young’s Modulus Fracture toughness Thermal conductivity Coefficient of thermal expansion
Fig. 5. SEM micrograph of borosilicate glass fibre chip powder formed while machining GFRP composite with an alumina cutting tool.
crack growth leads to rupture if it is brittle in nature. In FRP, a combination of plastic deformation with shearing and rupture would take place. In the case of machining metals, crater wear appears in the cutting tool edge; however, while machining FRP, the tool edge is abraded by hard abrasive glass fibres. Usually the wear land of the cutting tool used for machining metals will have many rough ridges and grooves, whereas the wear land of alumina ceramic cutting tools used for machining GFRP materials appears to be smooth. This can be observed from the SEM micrographs of alumina cutting tools presented in Figs. 6a and 6b. From the SEM micrographs, it can be clearly seen that the effect of damage at the wear land is more in the Ti[C, N] mixed alumina cutting tool than in the SiC whisker reinforced alumina cutting tool. The reason may be attributed to the effective resistance of crack development by SiC whiskers at the flank face of the SiC whisker reinforced alumina cutting tool. The wear land of the alumina cutting tool appears to have smooth ridges and grooves on machining GFRP composite materials, whereas on machining the steel or cast iron it appears to have rough ridges and grooves [25]. The SEM micrograph of the Ti[C, N] alumina cutting tool has ridges and groves while machining GFRP composite materials (Fig. 7a). The formation of ridges and grooves is due to the high abrasion of microfibres over the edge of the cutting tool. No other chemical reaction appears on the microlevel while machining GFRP composite materials. In addition to abrasive wear, adhesion with microchipping appears on the cutting tool edge, and it can be clearly seen in the SEM micrographs of the alumina cutting tool under high magnification (Fig. 7b). When the cutting tool slides over the high hard abrasive, fibre chips impinge on the cutting tool, leading to the microchipping of the cutting tool. The chipped portion of the cutting tool is filled with the adhesive polymer matrix on the cutting tool edge. However, the adhesion of
3.74 2000 900 390 8.0 18 6
Fig. 6a. SEM micrograph of the SiC whisker reinforced alumina cutting tool edge (CC670).
Fig. 6b. SEM micrograph of the Ti[C, N] mixed alumina-based ceramic cutting tool (CC 650).
polymer does not contribute much to the formation of tool wear. The formation of flank wear is mainly due to the abrasion of hard glass fibres on the cutting tools. From the above observations it can be noted that the GFRP composite materials are difficult materials to machine, and that the SiC whisker reinforced alumina cutting tool exhibited better flank wear resistance than the Ti[C, N] mixed alumina cutting tool. While machining GFRP composite with the TiC mixed alumina cutting tool edge, massive deposition of the matrix is observed from the SEM micrographs (Figs. 6b and 7b). From the SEM micrograph, it can be seen that the surface of the Ti[C, N] mixed
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
Fig. 8. Typical machined surface profile observed during machining GFRP composite material.
Ra
Fig. 7a. Ridges and grooves on the wear land of the SiC whisker reinforced alumina cutting tool while machining GFRP composite material.
71
Fig. 9. Surface roughness versus cutting velocity after machining GFRP composite material with alumina cutting tool for 9 min.
Fig. 7b. Bulk deposition of matrix material on the Ti[C, N] mixed alumina cutting tool while machining GFRP composite material.
alumina cutting tool was subjected to microflaking, leading to the development of flank wear. Flaking on the wear land is caused by the high sliding friction between the alumina cutting tool and the GFRP composite material. At higher cutting velocity, the cutting tool edge tends to chip, leading to the removal of a small portion of the tool material on the cutting tool edge, known as flaking. 3.3. Surface roughness In machining processes, surface integrity is one of the main requirements, and it determines the quality of the finished product. While machining fibre composite with cutting tool, the crack generates in deformation zone and it propagates downward. Sometimes, fibres are pulled out and they flow with the cutting tool edge, and others remains with the top part protruding from the cutting surface, as the fibre materials are generally brittle in nature. This can be clearly seen from the SEM micrograph of machined GFRP composite (Fig. 8). In addition, surface flaws due to delamination and interlaminar cracks are also observed while machining GFRP composite materials. It is clearly observed that the strong glass fibre undergoes sharp brittle fracture with deformation of matrix materials in the form of fibre/matrix distortion, fibre
microcracking, and pulverization. Hence the measurement of surface roughness of FRP composites is not easy when compared to that of metals. The factor affecting surface roughness other than surface morphology of GFRP composite is cutting velocity. Fig. 9 shows the surface roughness observed while machining GFRP composite material with alumina cutting tools with respect to cutting velocity. The surface roughness was shown to be improved by increasing the cutting velocity, though the improvement on surface finish was very limited. The direction of measurement of machined surface of FRP composite should be same as the direction of the fibre orientation as it helps to reduce the deviation in the measurement. It can be noted that the surface roughness of machined GFRP composite material ranges from 4.5to6.5 µm (microns). The wide variations in the surface roughness values may be due to the inherent variations in the surface of the matrix and the fibres. The surface roughness of matrix material is generally lower than that of the fibre material. The advantage of machining GFRP materials using alumina-based ceramic cutting tools is that they produce better surface finish than other conventional cutting tools. The surface roughness is very wide in range for the Ti[C, N] mixed alumina cutting tool, having an average surface roughness of 6.146 µm at a cutting velocity of 150 m/min, whereas the average surface roughness for the SiC whisker reinforced alumina cutting tool is 5.148 µm for the same cutting conditions. This is due to the great affinity of the SiC whisker reinforced alumina cutting tool while machining GFRP composite. Ceramic cutting tools eliminate a built-up edge (BUE) forming during machining. The matrix is a thermoset plastic material which is brittle and it does not
72
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
On machining GFRP composite, the Ti[C, N] mixed alumina cutting tool produced a higher cutting force of 265 N at the cutting velocity of 150 m/min than that of the SiC whisker reinforced alumina cutting tool (220 N for the same cutting condition). The cutting force initially decreases significantly as the cutting speed increases. However, the cutting force tends to increase at higher cutting speeds above 250 m/min. The initial decrease in cutting force with respect to the cutting speed is due to the decrease in tool chip contact and increase in the cutting zone area, leading to the reduction in shear strength of the work piece. As the cutting speed increases, the tool wear increases, and work hardening occurs in the work piece. The increase in tool wear makes it difficult for the cutting tool to machine the work piece. Hence, the cutting force tends to increase at higher cutting speeds. In addition, the presence of abrasive particles leads to the fluctuation of the cutting force due to the bulk removal of hard abrasive fibre. 4. Conclusion Fig. 10. Principal cutting force versus cutting velocity of alumina cutting tools while machining GFRP composite at 6 min.
have a tendency to form a BUE. As the cutting speed increases, the possibility of the formation of a BUE is greatly reduced. Hence the surface roughness decreases. However, the SiC whisker reinforced alumina cutting tool is able to produce lower surface roughness with less surface damage than the Ti[C, N] mixed alumina cutting tool, due to its better mechanical and thermal properties. The nose region of the SiC whisker alumina cutting tool is also less affected when compared to that of the Ti[C, N] mixed alumina cutting tool. 3.4. Cutting force The cutting force in the machining process is produced due to the sliding of the cutting tool against the work piece in order to remove the material from the work piece. The cutting tool geometry, tool materials, and machining conditions are responsible for higher cutting forces which in turn produce worse surface texture. The presence of glass fibre with brittle behavior of the reinforcement reduces the contact area and promotes low cutting force. Two main mechanisms represent the cutting force in machining FRP composite, namely shearing in the perpendicular direction and buckling in the parallel direction. In this study, alumina-based ceramic cutting tools were used to machine GFRP composite with a fibre orientation angle of 90° (formed by the hoop winding process). The direction of the cutting tool will be perpendicular to the fibre orientation, and the mechanism of the shearing process persists. The cutting force measured from lathe tool dynamometer while machining GFRP composite using alumina cutting tool at a constant feed rate and depth of cut of 0.06 mm/rev and 0.2 mm, respectively, is shown in Fig. 10. The maximum principal cutting force occurs in the direction of the cutting velocity. In general, the cutting force does not exhibit any particular trend, as the fluctuation of the cutting force appears due to the machining of hard abrasive fibres and soft matrix material in a cyclic manner. Hence, it is very difficult to predict the cutting force while machining FRP composite materials. The principal cutting force obtained during machining GFRP composites is considerably lower than that on machining steel [22,25]. This is due to the difference in composition of GFRP material, its amorphous nature, and the soft condition of the matrix material. As the fibre diameter is very small, bending of the highly abrasive fibre does not require high pressure by the cutting tool edge. In general, the alumina-based ceramic cutting tool with positive rake angle and without a chip breaker was the most effective tool in reducing the cutting force while machining E-glass/polyester-based GFRP composite.
The machinability of GFRP composite material using alumina cutting tools has been analysed. Both the alumina cutting tools used underwent gradual progressive abrasive wear with respect to the cutting speed. The abrasive wear is quite smooth and less with the SiC whisker reinforced alumina cutting tool than with the Ti[C, N] mixed alumina cutting tool while machining GFRP composite material, which is due to the presence of highly abrasive fibres. Variations in surface roughness values were noticed due to the inherent variation in the surface roughness of the matrix and the fibres. The SiC whisker reinforced alumina cutting tool produced a better surface finish than the Ti[C, N] mixed alumina cutting tool. In conclusion, the performance of the SiC whisker reinforced alumina cutting tool is better than that of the Ti[C, N] mixed alumina cutting tool on machining GFRP composite. References [1] Komanduri R. Machining of fibre reinforced composite. Machining Science & Technology 1997;1(1):113–52. [2] Smith WilliamF, Hashemi Javad. Foundation of materials science and engineering. forth ed. NY: Mc-Graw Hill International Edition; 2006. [3] Agarwal BhagwanD, Broutman LawrenceJ. Analysis and performance of fibre composites. second ed. USA: A Wiley-Interscience Publications; 2000. [4] Jones RobertM. Mechanics of composite materials. second ed. Taylor & Francis Inc.; 1999. [5] Jain VK, Choudhury SK, Ramesh KM. On the machining of alumina and glass. International Journal of Machine Tools and Manufacture 2002;42:1269–76. [6] Paulo Davim J, Silva LeonardoR, Festas António, Abrão AM. Machinability study on precision turning of PA66 polyamide with and without glass fiber reinforcing. Materials and Design 2009;30:228–34. [7] Palanikumar K. Application of Taguchi and response surface methodologies for surface roughness in machining glass fibre reinforced plastics by PCD tooling. International Journal of Advanced Manufacturing Technology 2008;36(1–2): 19–27. [8] Geier MH. Quality handbook for composite materials. Chapman & Hall Publications; 1994. [9] Lee ES. Precision machining of glass fibre reinforced plastics with respect to tool characteristics. International Journal of Advanced Manufacturing Technology 2001;17:791–8. [10] Palanikumar K, Paulo Davim J. Assessment of some factors influencing tool wear on the machining of glass fibre-reinforced plastics by coated cemented carbide tools. Journal of Materials Processing Technology 2009;209:511–9. [11] Zhang LC. Cutting composites: a discussion on mechanics modeling. Journal of Materials Processing Technology 2009;209:4548–52. [12] Santhanakrishnan G, Krishnamurthy R, Malhotra SK. High speed tool wear studies in machining of glass fibre reinforced plastic. Wear 1989;132:327–36. [13] Bhatnagar N, Ramakrishnan N, Naik NK, Komanduri R. On the machining of fibre reinforced plastic (FRP) composite laminates. International Journal of Machine Tools and Manufacture 1995;35(5):701–16. [14] Venu Gopala Roa G, Mahajan Puneet, Bhatnagar Naresh. Machining of UD—GFRP composites chip formation mechanism. Composites Science and Technology 2007;67:2271–81. [15] Sharma M, Rao IM, Bijwe J. Influence of orientation of long fibers in carbon fiber–polyetherimide composites on mechanical and tribological properties. Wear 2009;267:839–45.
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73 [16] Sreejith PS, Krishnamurthy R, Malhotra SK. Effect of specific cutting pressure and temperature during machining of carbon/phenolic ablative composite using PCBN tools. Journal of Materials Processing Technology 2007;183:88–95. [17] Davim Paulo, Mata Francisco. Optimisation of surface roughness on turning fibre reinforced plastics (FRP’s) with diamond cutting tools. The International Journal of Advanced Manufacturing Technology 2005;26:319–23. [18] Sreejith PS, Krishnamurthy R, Malhotra SK, Narayanasamy K. Evaluation of PCD tool performance during machining of carbon/phenolic ablative composites. Journal of Materials Processing Technology 2000;104:53–8. [19] Fereirra JR, Coppini NL, Levy Neto F. Characteristics of carbon–carbon composite turning. Journal of Materials Processing Technology 2001;109: 65–71. [20] Rahman M, Ramakrishna S, Prakash , Tan . Machinability study of carbon fibre reinforced composite. Journal of Materials Processing 1999;89–90:292–7. [21] Uhlmann E, Lachmund U, Brucher M. Wear behavior of HFCVD—diamond coated carbide and ceramic tools. Surface and Coatings Technology 2000;131: 395–9. [22] Senthil Kumar A, Raja Durai A, Sornakumar T. Machinability of hardened steel using alumina based ceramic cutting tools. International Journal of Refractory Metals & Hard Materials 2003;21:109–17. [23] Grzesik W. Wear development on wiper Al2 O3 –TiC mixed ceramic tools in hard machining of high strength steel. Wear 2009;266:1021–8. [24] Xu CH, Feng YM, Zhanga RB, Zhao SK, Xiao X, Yu GT. Wear behavior of Al2 O3 /Ti(C, N)/SiC new ceramic tool material when machining tool steel and cast iron. Journal of Materials Processing Technology 2009;209:4633–7.
73
[25] Senthil Kumar A, Raja Durai A, Sornakumar T. The effect of tool wear on tool life of alumina-based ceramic cutting tools while machining hardened martensitic stainless steel. Journal of Materials Processing Technology 2006;173: 151–6. [26] Gogolewski P, Klimke J, Krell A, Beer P. Al2 O3 tools towards effective machining of wood-based materials. Journal of Materials Processing Technology 2009; 209:2231–6. [27] Aslan Ersan, Camuscu Necip, Birgoren Burak. Design optimization of cutting parameters when turning hardened AISI 4140 steel (63 HRC) with Al2 O3 +TiCN mixed ceramic tool. Materials and Design 2007;28:1618–22. [28] Afaghani JED, Yamaguchi K, Horaguchi I, Nakamoto T. Whisker behaviors and tool wear in cutting of unidirectional SiC whisker-reinforced plastic. Wear 1996;195:223–31. [29] Li XS, Low IM. Evaluation of advanced alumina-based ceramic tool inserts when machining high-tensile steel. Journal of Materials Science 1994;29: 3121–7. [30] Jianxin Deng, Xuefeng Yang, Jianhua Liu. Self-lubricating behaviours of ceramic tools in dry cutting. International Journal of Machining and Machinability of Materials 2006;1(2):213–22. [31] Aslan E. Experimental investigation of cutting tool performance in high speed cutting of hardened X210 Cr12 cold-work tool steel (62HRC). Materials and Design 2005;26(1):21–7. [32] Paulo Davim J, Silva LeonardoR, Festas António, Abrão AM. Machinability study on precision turning of PA66 polyamide with and without glass fiber reinforcing. Materials and Design 2009;30:228–34.
Contents lists available at ScienceDirect
Journal of Manufacturing Processes journal homepage: www.elsevier.com/locate/manpro
Review
Machinability of glass fibre reinforced plastic (GFRP) composite using alumina-based ceramic cutting tools M. Adam Khan ∗ , A. Senthil Kumar Department of Production Engineering, Sethu Institute of Technology, Virudhunagar Dist., Tamil Nadu, India
article
info
Article history: Received 24 August 2009 Received in revised form 18 August 2010 Accepted 1 October 2010 Available online 27 October 2010
abstract This paper deals with the machining of glass fibre reinforced plastic (GFRP) composite material. GFRP composite material was fabricated in our laboratory using E-glass fibre with unsaturated polyester resin. GFRP composite specimens were prepared using a filament winding process. Machining studies were carried out using two different alumina cutting tools: namely, a Ti[C, N] mixed alumina cutting tool (CC650) and a SiC whisker reinforced alumina cutting tool (CC670). The machining process was performed at different cutting speeds at constant feed rate and depth of cut. The performance of the alumina cutting tools was evaluated by measuring the flank wear and surface roughness of the machined GFRP composite material. An attempt is made to analyse the main wear mechanism of alumina cutting tools while machining GFRP composite material. © 2010 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved.
Contents 1. 2.
3.
4.
Introduction........................................................................................................................................................................................................................ Experimental procedure .................................................................................................................................................................................................... 2.1. Preparation of GFRP composite rod ...................................................................................................................................................................... 2.2. Machining study .................................................................................................................................................................................................... Result and discussion......................................................................................................................................................................................................... 3.1. Flank wear of the alumina cutting tool ................................................................................................................................................................ 3.2. SEM observation and wear mechanism ............................................................................................................................................................... 3.3. Surface roughness.................................................................................................................................................................................................. 3.4. Cutting force........................................................................................................................................................................................................... Conclusion .......................................................................................................................................................................................................................... References...........................................................................................................................................................................................................................
1. Introduction GFRP composite material was developed to meet the requirements of the industry for high- strength materials with low weight. The advantages of GFRP material include savings in weight, improvement in strength and decreased cost of material and fabrication. Glass fibre reinforced composites have been used for engineering applications, and various types of glass fibres are used as reinforcements. E-glass fibres are widely used as they have special characteristics such as high strength to weight ratio, good dimensional stability, good resistance to heat, cold, moisture, and corrosion, and good electrical insulation properties. The concept of incorporating a strong fibre or whiskers into a tough or ductile
∗
Corresponding author. Tel.: +91 9843361274; fax: +91 4566308000. E-mail address: [email protected] (M. Adam Khan).
67 68 68 69 69 69 69 71 72 72 72
matrix yields a very high strength to the composite as they carry load [1–4]. Machining glass fibre composite is still a major problem, because of their inert nature, high hardness, and refractoriness [5]. Because of their different applications, the need for machining FRP material has not been fully eliminated. Glass fibre reinforced plastics (GFRPs) are extremely abrasive; thus proper selection of the cutting tool and cutting parameters is very important for a perfect machining process [6]. The mechanism of machining GFRP composite is quite different from that of metals [7–9]. While machining a GFRP, the strong fibre materials cause rapid tool wear and poor surface finish. Tool wear reduction is an important aspect in machining GFPR composites [10]. The surface integrity of a GFRP machined composite is hard to control, including surface roughness, residual stresses and subsurface damages due to varying mechanical properties of the fibre and the matrix [11]. Santhanakrishnan et al. [12] reported that the mechanisms associated with machining of GFRP composite are plastic deformation, shearing,
1526-6125/$ – see front matter © 2010 The Society of Manufacturing Engineers. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jmapro.2010.10.002
68
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
Fig. 1. E-glass fibre reinforced composite rod. Table 1 Properties of E-glass fibre roving. Material
Density (g/cm3 )
Tensile modulus ksi (GPa)
Tensile strength ksi (Mpa)
Tensile strain (%)
E-glass fibre roving (2400 m/kg)
2.6
11,000 (76)
500 (3450)
4.7
and rupture of fibres orientation. Fibre orientation is an important criterion which affects the machining process and strength of the composite [13,14]. Sharma et al. [15] stated that wear performance of the cutting tool decreases with 90° fibre orientation. Sreejith et al. [16] observed that the cutting force and the cutting temperature affect the performance of the cutting tools while machining carbon/carbon composites. Davim et al. [17] used a polycrystalline diamond (PCD) cutting tool to machine FRP tubes and obtained optimal cutting parameters for surface roughness. Sreejith et al. [18] evaluated the performance of a PCD cutting tool while machining carbon/phenolic composite material, by observing the tool wear, cutting force, and cutting temperature. Fereirra et al. [19] also reported that a diamond tool could be used for finish machining as it produced low surface roughness with minimum tool wear. Rahman et al. [20] conducted machining studies on a carbon fibre reinforced plastic (CFRP) composite using various advanced cutting tools and found that PCD tools exhibited high wear resistance. Ulhmann et al. [21] conducted a machining study using diamond-coated carbide and ceramic cutting tools on FRP material, and observed that the diamond-coated carbide and ceramic cutting tools exhibited high wear resistance and high tool life. An alumina-based ceramic cutting tool is one of the attractive alternative cutting tools for machining hard materials [22]. Ceramic cutting tools are cost effective and able to produce a good surface finish at higher cutting speed. Alumina-based ceramic cutting tools are persistently used to machine hard materials, as they can withstand high hot hardness up to 1500 °C with chemical stability [23]. Xu et al. [24] developed an Al2 O3 /Ti[C, N]/SiC whisker cutting tool and conducted machining studies on hard materials, and found that such multiphase ceramic cutting tools have good wear resistance. While machining hard materials, the wear morphology of the alumina cutting tool indicated plastic deformation along with mild abrasion and small glassy deposits were observed [25,26]. Aslan et al. [27] reported that the tool wear of an Al2 O3 mixed ceramic tool decreased almost linearly with cutting speed during hard turning of AISI 4140 steel. Afaghani et al. [28] stated that the presence of whiskers in a composite material resists the extension of crack propagation during machining. A SiC whisker reinforced alumina cutting tool can produce a twofold increase in fracture toughness and it has received widespread acceptance in the aerospace industry, where it is regarded as the state-of-the-art cutting-tool material for the finishing and rough machining of nickel-based superalloys because of its high wear resistance and fracture toughness [29]. Deng et al. [30] made an attempt to machine a nickel-based alloy using Al2 O3 /TiB2 /SiCw ceramic cutting tools and found that the composite tool materials with higher SiC whisker content showed better wear resistance. Abrasive wear was found to be
the predominant flank wear mechanism while machining nickelbased alloy. Aslan [31] made an attempt to machine hard materials using cubic boron nitride (CBN), Al2 O3 + Ti[C, N] cutting tool, coated cermet cutting tool and carbide cutting tool. From the investigation, it is found that the Al2 O3 + Ti[C, N] cutting tool and CBN exhibit better performance and higher tool life than coated cermet and carbide cutting tools. Cutting force analysis plays a vital role in studying the machining process of FRP materials [32]. In general, FRP materials are inhomogeneous, as the reinforcement has anisotropic characteristics. They consist of a load-carrying fibre component which appears as a bundle of fibres, which leads to difficulties in the machining process. In this regard, the cutting force is an important dependent variable of the machining system and it has been investigated by many researchers in various cutting processes. The range of cutting force also varies with respect to the fibre orientation and fibre–matrix volume fraction. In this study, the cutting force along with surface roughness and tool wear were measured on machining GFRP composite materials. It can be observed from the literature that polycrystalline diamond (PCD), cubic boron nitride (CBN), and polycrystalline cubic boron nitride (PcBN) are widely used to machine GFRP materials. Though ceramic cutting tools are cheaper than PCD and PcBN tools, they provide equivalent performance on machining hard materials. However, the performances of ceramic cutting tools have not been evaluated properly on machining GFRP materials. Hence, machining studies have been conducted on GFRP materials using a Ti[C, N] mixed alumina cutting tool and a SiC whisker reinforced alumina cutting tool; the GFRP composite was prepared using unsaturated polyester resin with E-glass fibre as reinforcement. 2. Experimental procedure 2.1. Preparation of GFRP composite rod The GFRP composite rod was prepared in our laboratory. Eglass fibre is chosen for its excellent properties (Table 1), and its composition is presented in Table 2. The glass fibre roving was made to pass through an unsaturated polyester resin bath to get wet and it was wound with a fibre orientation angle of 90° on a steel rod having a diameter of 15 mm. Fig. 1 shows the GFRP composite rod with a steel rod at the centre. The composite was cured for two hours to get the required strength. The GFRP rod of 65 mm diameter and 400 mm length was cut so that it could be held in between the centers in a precision lathe for the machining study. Fig. 2 shows a scanning electron microscope (SEM) micrograph of GFRP composite prepared using the filament winding process. From the SEM picture, it can be noted that the glass fibres are strongly bonded and homogeneously impregnated with the polyester matrix material.
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
69
Table 2 Composition of E-glass fibre. Composition Content %
SiO2 52%–56%
AlO2 12%–16%
CaO 16%–25%
B2 O3 8%–13%
Fig. 3. Flank wear versus machining time of alumina cutting tools while machining GFRP composite.
Fig. 2. SEM micro graph of GFRP composite.
2.2. Machining study Machining studies were carried out to machine GFRP composite material in a precision lathe using a Ti[C, N] mixed alumina cutting tool (CC650) and a SiC whisker reinforced alumina cutting tool (CC670). The properties of both the alumina-based ceramic cutting tools are given in Table 3. The machining process was performed with various cutting speeds at constant feed rate and depth of cut. Flank wear and surface roughness were observed during machining of the GFRP composite. The flank wear was measured using a Metzer Toolmakers microscope, the surface roughness (Ra ) was measured using a TR200 surface profile meter, and the cutting force was measured using a strain gauge type dynamometer. 3. Result and discussion 3.1. Flank wear of the alumina cutting tool Tool wear is one of the most important criteria in machining processes; it directly affects the tool life, surface quality, and production cost. Tool wear in machining FRP composite material occurs due to the rubbing of the cutting tool edge with the hard fibres impregnated in the matrix materials. While machining FRP composite material, flank wear is the main form of wear, as other forms of tool wear are negligible. Fig. 3 shows the variation of flank wear with respect to machining time while machining GFRP composite material using the Ti[C, N] mixed alumina cutting tool (CC650) and the SiC whisker reinforced alumina cutting tool (CC670) at 250 m/min. Fig. 4 shows the flank wear versus cutting velocity of the alumina cutting tools after 6 min of machining. The flank wear of the alumina cutting tool increases with respect to speed and machining time and it is higher at higher cutting speeds. The main wear mechanism is abrasion. The glass fibre in the GFRP composites abrades with the cutting tool and removes some of the tool material at the flank face. The wear by abrasion is usually due to the crack development, and the intersection caused by hard fibre chips acting as small indenters on the cutting face. The broken fibres during machining cause further wear at the tool chip interface. As the cutting speed increases, the velocity of abrasion increases, and the rate of contact of broken fibre chips
Fig. 4. Flank wear versus cutting velocity of alumina cutting tools while machining GFRP composite at 6 min.
also increases, leading to a higher flank wear at high speed. Chip formation while machining GFPR materials is an important factor in addition to fibre orientation, fibre delamination, and direction of machining. The fracture of fibre chips causes extreme damage to the cutting tool through abrasion, causing to the development and growth of flank wear. The fibre fracture is due to the combination of crushing and bending caused by the machining process. The broken fibres can be observed from the SEM micrograph, along with the chips of matrix material (Fig. 5). The presence of broken fibres as seen in the SEM micrograph contributes to the abrasive wear. From Fig. 3, it can be noted that the Ti[C, N] mixed alumina cutting tool fails after 8 min of machining at 250 m/min as it crosses the failure criterion for flank wear (i.e. 0.4 mm wear for finish machining). Tool failure of the Ti[C, N] mixed alumina cutting tool occurs after 6 min of machining at 300 m/min; however, the SiC whisker reinforced alumina cutting tool approaches tool failure after 9 min. 3.2. SEM observation and wear mechanism Machining of GFRP material is quite different from machining of metals. Fibre orientation and the cutting tool geometry will have significant contributions in machining fibre composite material. While machining, the interface of the cutting tool and work material is subsequently made to shear if it is ductile and the
70
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
Table 3 The properties of the alumina-based ceramic cutting tool materials. Details of tool material
Unit
Ti[C, N] mixed alumina (CC650)
SiC whisker reinforced alumina (CC670) Al2 O3 80% SiCw 20%
g/cm3 (HV10) MPa GPa MPa m1/2 W/mK K−1 .10−6
Al2 O3 70% TiN 22.5% TiC 7.5% 4.26 1800 550 400 4.0 24 8.6
Composition Density Vickers hardness Transverse rupture strength Young’s Modulus Fracture toughness Thermal conductivity Coefficient of thermal expansion
Fig. 5. SEM micrograph of borosilicate glass fibre chip powder formed while machining GFRP composite with an alumina cutting tool.
crack growth leads to rupture if it is brittle in nature. In FRP, a combination of plastic deformation with shearing and rupture would take place. In the case of machining metals, crater wear appears in the cutting tool edge; however, while machining FRP, the tool edge is abraded by hard abrasive glass fibres. Usually the wear land of the cutting tool used for machining metals will have many rough ridges and grooves, whereas the wear land of alumina ceramic cutting tools used for machining GFRP materials appears to be smooth. This can be observed from the SEM micrographs of alumina cutting tools presented in Figs. 6a and 6b. From the SEM micrographs, it can be clearly seen that the effect of damage at the wear land is more in the Ti[C, N] mixed alumina cutting tool than in the SiC whisker reinforced alumina cutting tool. The reason may be attributed to the effective resistance of crack development by SiC whiskers at the flank face of the SiC whisker reinforced alumina cutting tool. The wear land of the alumina cutting tool appears to have smooth ridges and grooves on machining GFRP composite materials, whereas on machining the steel or cast iron it appears to have rough ridges and grooves [25]. The SEM micrograph of the Ti[C, N] alumina cutting tool has ridges and groves while machining GFRP composite materials (Fig. 7a). The formation of ridges and grooves is due to the high abrasion of microfibres over the edge of the cutting tool. No other chemical reaction appears on the microlevel while machining GFRP composite materials. In addition to abrasive wear, adhesion with microchipping appears on the cutting tool edge, and it can be clearly seen in the SEM micrographs of the alumina cutting tool under high magnification (Fig. 7b). When the cutting tool slides over the high hard abrasive, fibre chips impinge on the cutting tool, leading to the microchipping of the cutting tool. The chipped portion of the cutting tool is filled with the adhesive polymer matrix on the cutting tool edge. However, the adhesion of
3.74 2000 900 390 8.0 18 6
Fig. 6a. SEM micrograph of the SiC whisker reinforced alumina cutting tool edge (CC670).
Fig. 6b. SEM micrograph of the Ti[C, N] mixed alumina-based ceramic cutting tool (CC 650).
polymer does not contribute much to the formation of tool wear. The formation of flank wear is mainly due to the abrasion of hard glass fibres on the cutting tools. From the above observations it can be noted that the GFRP composite materials are difficult materials to machine, and that the SiC whisker reinforced alumina cutting tool exhibited better flank wear resistance than the Ti[C, N] mixed alumina cutting tool. While machining GFRP composite with the TiC mixed alumina cutting tool edge, massive deposition of the matrix is observed from the SEM micrographs (Figs. 6b and 7b). From the SEM micrograph, it can be seen that the surface of the Ti[C, N] mixed
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
Fig. 8. Typical machined surface profile observed during machining GFRP composite material.
Ra
Fig. 7a. Ridges and grooves on the wear land of the SiC whisker reinforced alumina cutting tool while machining GFRP composite material.
71
Fig. 9. Surface roughness versus cutting velocity after machining GFRP composite material with alumina cutting tool for 9 min.
Fig. 7b. Bulk deposition of matrix material on the Ti[C, N] mixed alumina cutting tool while machining GFRP composite material.
alumina cutting tool was subjected to microflaking, leading to the development of flank wear. Flaking on the wear land is caused by the high sliding friction between the alumina cutting tool and the GFRP composite material. At higher cutting velocity, the cutting tool edge tends to chip, leading to the removal of a small portion of the tool material on the cutting tool edge, known as flaking. 3.3. Surface roughness In machining processes, surface integrity is one of the main requirements, and it determines the quality of the finished product. While machining fibre composite with cutting tool, the crack generates in deformation zone and it propagates downward. Sometimes, fibres are pulled out and they flow with the cutting tool edge, and others remains with the top part protruding from the cutting surface, as the fibre materials are generally brittle in nature. This can be clearly seen from the SEM micrograph of machined GFRP composite (Fig. 8). In addition, surface flaws due to delamination and interlaminar cracks are also observed while machining GFRP composite materials. It is clearly observed that the strong glass fibre undergoes sharp brittle fracture with deformation of matrix materials in the form of fibre/matrix distortion, fibre
microcracking, and pulverization. Hence the measurement of surface roughness of FRP composites is not easy when compared to that of metals. The factor affecting surface roughness other than surface morphology of GFRP composite is cutting velocity. Fig. 9 shows the surface roughness observed while machining GFRP composite material with alumina cutting tools with respect to cutting velocity. The surface roughness was shown to be improved by increasing the cutting velocity, though the improvement on surface finish was very limited. The direction of measurement of machined surface of FRP composite should be same as the direction of the fibre orientation as it helps to reduce the deviation in the measurement. It can be noted that the surface roughness of machined GFRP composite material ranges from 4.5to6.5 µm (microns). The wide variations in the surface roughness values may be due to the inherent variations in the surface of the matrix and the fibres. The surface roughness of matrix material is generally lower than that of the fibre material. The advantage of machining GFRP materials using alumina-based ceramic cutting tools is that they produce better surface finish than other conventional cutting tools. The surface roughness is very wide in range for the Ti[C, N] mixed alumina cutting tool, having an average surface roughness of 6.146 µm at a cutting velocity of 150 m/min, whereas the average surface roughness for the SiC whisker reinforced alumina cutting tool is 5.148 µm for the same cutting conditions. This is due to the great affinity of the SiC whisker reinforced alumina cutting tool while machining GFRP composite. Ceramic cutting tools eliminate a built-up edge (BUE) forming during machining. The matrix is a thermoset plastic material which is brittle and it does not
72
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73
On machining GFRP composite, the Ti[C, N] mixed alumina cutting tool produced a higher cutting force of 265 N at the cutting velocity of 150 m/min than that of the SiC whisker reinforced alumina cutting tool (220 N for the same cutting condition). The cutting force initially decreases significantly as the cutting speed increases. However, the cutting force tends to increase at higher cutting speeds above 250 m/min. The initial decrease in cutting force with respect to the cutting speed is due to the decrease in tool chip contact and increase in the cutting zone area, leading to the reduction in shear strength of the work piece. As the cutting speed increases, the tool wear increases, and work hardening occurs in the work piece. The increase in tool wear makes it difficult for the cutting tool to machine the work piece. Hence, the cutting force tends to increase at higher cutting speeds. In addition, the presence of abrasive particles leads to the fluctuation of the cutting force due to the bulk removal of hard abrasive fibre. 4. Conclusion Fig. 10. Principal cutting force versus cutting velocity of alumina cutting tools while machining GFRP composite at 6 min.
have a tendency to form a BUE. As the cutting speed increases, the possibility of the formation of a BUE is greatly reduced. Hence the surface roughness decreases. However, the SiC whisker reinforced alumina cutting tool is able to produce lower surface roughness with less surface damage than the Ti[C, N] mixed alumina cutting tool, due to its better mechanical and thermal properties. The nose region of the SiC whisker alumina cutting tool is also less affected when compared to that of the Ti[C, N] mixed alumina cutting tool. 3.4. Cutting force The cutting force in the machining process is produced due to the sliding of the cutting tool against the work piece in order to remove the material from the work piece. The cutting tool geometry, tool materials, and machining conditions are responsible for higher cutting forces which in turn produce worse surface texture. The presence of glass fibre with brittle behavior of the reinforcement reduces the contact area and promotes low cutting force. Two main mechanisms represent the cutting force in machining FRP composite, namely shearing in the perpendicular direction and buckling in the parallel direction. In this study, alumina-based ceramic cutting tools were used to machine GFRP composite with a fibre orientation angle of 90° (formed by the hoop winding process). The direction of the cutting tool will be perpendicular to the fibre orientation, and the mechanism of the shearing process persists. The cutting force measured from lathe tool dynamometer while machining GFRP composite using alumina cutting tool at a constant feed rate and depth of cut of 0.06 mm/rev and 0.2 mm, respectively, is shown in Fig. 10. The maximum principal cutting force occurs in the direction of the cutting velocity. In general, the cutting force does not exhibit any particular trend, as the fluctuation of the cutting force appears due to the machining of hard abrasive fibres and soft matrix material in a cyclic manner. Hence, it is very difficult to predict the cutting force while machining FRP composite materials. The principal cutting force obtained during machining GFRP composites is considerably lower than that on machining steel [22,25]. This is due to the difference in composition of GFRP material, its amorphous nature, and the soft condition of the matrix material. As the fibre diameter is very small, bending of the highly abrasive fibre does not require high pressure by the cutting tool edge. In general, the alumina-based ceramic cutting tool with positive rake angle and without a chip breaker was the most effective tool in reducing the cutting force while machining E-glass/polyester-based GFRP composite.
The machinability of GFRP composite material using alumina cutting tools has been analysed. Both the alumina cutting tools used underwent gradual progressive abrasive wear with respect to the cutting speed. The abrasive wear is quite smooth and less with the SiC whisker reinforced alumina cutting tool than with the Ti[C, N] mixed alumina cutting tool while machining GFRP composite material, which is due to the presence of highly abrasive fibres. Variations in surface roughness values were noticed due to the inherent variation in the surface roughness of the matrix and the fibres. The SiC whisker reinforced alumina cutting tool produced a better surface finish than the Ti[C, N] mixed alumina cutting tool. In conclusion, the performance of the SiC whisker reinforced alumina cutting tool is better than that of the Ti[C, N] mixed alumina cutting tool on machining GFRP composite. References [1] Komanduri R. Machining of fibre reinforced composite. Machining Science & Technology 1997;1(1):113–52. [2] Smith WilliamF, Hashemi Javad. Foundation of materials science and engineering. forth ed. NY: Mc-Graw Hill International Edition; 2006. [3] Agarwal BhagwanD, Broutman LawrenceJ. Analysis and performance of fibre composites. second ed. USA: A Wiley-Interscience Publications; 2000. [4] Jones RobertM. Mechanics of composite materials. second ed. Taylor & Francis Inc.; 1999. [5] Jain VK, Choudhury SK, Ramesh KM. On the machining of alumina and glass. International Journal of Machine Tools and Manufacture 2002;42:1269–76. [6] Paulo Davim J, Silva LeonardoR, Festas António, Abrão AM. Machinability study on precision turning of PA66 polyamide with and without glass fiber reinforcing. Materials and Design 2009;30:228–34. [7] Palanikumar K. Application of Taguchi and response surface methodologies for surface roughness in machining glass fibre reinforced plastics by PCD tooling. International Journal of Advanced Manufacturing Technology 2008;36(1–2): 19–27. [8] Geier MH. Quality handbook for composite materials. Chapman & Hall Publications; 1994. [9] Lee ES. Precision machining of glass fibre reinforced plastics with respect to tool characteristics. International Journal of Advanced Manufacturing Technology 2001;17:791–8. [10] Palanikumar K, Paulo Davim J. Assessment of some factors influencing tool wear on the machining of glass fibre-reinforced plastics by coated cemented carbide tools. Journal of Materials Processing Technology 2009;209:511–9. [11] Zhang LC. Cutting composites: a discussion on mechanics modeling. Journal of Materials Processing Technology 2009;209:4548–52. [12] Santhanakrishnan G, Krishnamurthy R, Malhotra SK. High speed tool wear studies in machining of glass fibre reinforced plastic. Wear 1989;132:327–36. [13] Bhatnagar N, Ramakrishnan N, Naik NK, Komanduri R. On the machining of fibre reinforced plastic (FRP) composite laminates. International Journal of Machine Tools and Manufacture 1995;35(5):701–16. [14] Venu Gopala Roa G, Mahajan Puneet, Bhatnagar Naresh. Machining of UD—GFRP composites chip formation mechanism. Composites Science and Technology 2007;67:2271–81. [15] Sharma M, Rao IM, Bijwe J. Influence of orientation of long fibers in carbon fiber–polyetherimide composites on mechanical and tribological properties. Wear 2009;267:839–45.
M. Adam Khan, A. Senthil Kumar / Journal of Manufacturing Processes 13 (2011) 67–73 [16] Sreejith PS, Krishnamurthy R, Malhotra SK. Effect of specific cutting pressure and temperature during machining of carbon/phenolic ablative composite using PCBN tools. Journal of Materials Processing Technology 2007;183:88–95. [17] Davim Paulo, Mata Francisco. Optimisation of surface roughness on turning fibre reinforced plastics (FRP’s) with diamond cutting tools. The International Journal of Advanced Manufacturing Technology 2005;26:319–23. [18] Sreejith PS, Krishnamurthy R, Malhotra SK, Narayanasamy K. Evaluation of PCD tool performance during machining of carbon/phenolic ablative composites. Journal of Materials Processing Technology 2000;104:53–8. [19] Fereirra JR, Coppini NL, Levy Neto F. Characteristics of carbon–carbon composite turning. Journal of Materials Processing Technology 2001;109: 65–71. [20] Rahman M, Ramakrishna S, Prakash , Tan . Machinability study of carbon fibre reinforced composite. Journal of Materials Processing 1999;89–90:292–7. [21] Uhlmann E, Lachmund U, Brucher M. Wear behavior of HFCVD—diamond coated carbide and ceramic tools. Surface and Coatings Technology 2000;131: 395–9. [22] Senthil Kumar A, Raja Durai A, Sornakumar T. Machinability of hardened steel using alumina based ceramic cutting tools. International Journal of Refractory Metals & Hard Materials 2003;21:109–17. [23] Grzesik W. Wear development on wiper Al2 O3 –TiC mixed ceramic tools in hard machining of high strength steel. Wear 2009;266:1021–8. [24] Xu CH, Feng YM, Zhanga RB, Zhao SK, Xiao X, Yu GT. Wear behavior of Al2 O3 /Ti(C, N)/SiC new ceramic tool material when machining tool steel and cast iron. Journal of Materials Processing Technology 2009;209:4633–7.
73
[25] Senthil Kumar A, Raja Durai A, Sornakumar T. The effect of tool wear on tool life of alumina-based ceramic cutting tools while machining hardened martensitic stainless steel. Journal of Materials Processing Technology 2006;173: 151–6. [26] Gogolewski P, Klimke J, Krell A, Beer P. Al2 O3 tools towards effective machining of wood-based materials. Journal of Materials Processing Technology 2009; 209:2231–6. [27] Aslan Ersan, Camuscu Necip, Birgoren Burak. Design optimization of cutting parameters when turning hardened AISI 4140 steel (63 HRC) with Al2 O3 +TiCN mixed ceramic tool. Materials and Design 2007;28:1618–22. [28] Afaghani JED, Yamaguchi K, Horaguchi I, Nakamoto T. Whisker behaviors and tool wear in cutting of unidirectional SiC whisker-reinforced plastic. Wear 1996;195:223–31. [29] Li XS, Low IM. Evaluation of advanced alumina-based ceramic tool inserts when machining high-tensile steel. Journal of Materials Science 1994;29: 3121–7. [30] Jianxin Deng, Xuefeng Yang, Jianhua Liu. Self-lubricating behaviours of ceramic tools in dry cutting. International Journal of Machining and Machinability of Materials 2006;1(2):213–22. [31] Aslan E. Experimental investigation of cutting tool performance in high speed cutting of hardened X210 Cr12 cold-work tool steel (62HRC). Materials and Design 2005;26(1):21–7. [32] Paulo Davim J, Silva LeonardoR, Festas António, Abrão AM. Machinability study on precision turning of PA66 polyamide with and without glass fiber reinforcing. Materials and Design 2009;30:228–34.