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The effect of triangle-shape carbon fiber on the flexural properties of the carbon fiber reinforced plastics
Materials Letters 73 (2012) 21–23
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
The effect of triangle-shape carbon fiber on the flexural properties of the carbon fiber reinforced plastics Xin Liu a, b, Rongguo Wang b,⁎, Zhanjun Wu a, Wenbo Liu b a School of Aeronautics and Astronautics, Faculty of Vehicle Engineering and Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, P.R. China b National Key laboratory of Science and Technology on advanced composites in Special Environments, Harbin Institute of Technology, Harbin 150001, P.R. China
a r t i c l e
i n f o
Article history: Received 26 October 2011 Accepted 2 January 2012 Available online 8 January 2012 Keywords: Polymeric composites Carbon materials Structural Microstructure
a b s t r a c t The triangle-shape carbon fiber reinforced plastics and the round-shape carbon fiber reinforced plastics were manufactured and the effects of carbon fiber shapes on the flexural properties were investigated. The microstructures and the cross-section areas of the round-shape carbon fiber and the triangle-shape carbon fiber were discussed. As a result, it was found that the triangle-shape carbon fiber reinforced plastics showed higher flexural strength and flexural modulus than round-shape carbon fiber reinforced plastics, and the tensile strength and tensile modulus did not reduced, which was attributed to that the triangle-shape carbon fiber reinforced plastics had larger interfacial contact area than round-shape ones, and the wider interfacial contact area between reinforcement and matrix that could effectively transfer the applied load. The flexural properties of fiber reinforced plastics were improved due to the stronger interfacial binding force. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The use of carbon fiber reinforced plastics (CFRP) has grown considerably in recent years, especially in the aeronautic, aerospace, sporting and automotive industries. CFRP offers unique advantages in terms of their high strength to weight ratio, high stiffness to weight ratio and good corrosive properties [1–3]. The physical and mechanical properties of CFRP are dependent largely on the fiber content, the fiber orientation, the shape of fiber, and variability in the matrix materials [4,5]. In general, the cross-section shape of the reinforcing fibers in composites is round-shape. In structural mechanics, as the optimization of the stress distribution of materials, it is recognized that non-round-shape fiber is better than round-shape fiber in mechanical properties in CFRP [6–8]. The triangle-shape carbon fibers have higher specific surface area than conventional round-shape carbon fibers. The larger area in the surface contacting with matrix can enhance interfacial binding force, consequently could improve the correlative mechanical properties. At present, there are only a limited number of studies on the different cross-section shape of carbon fiber. In this study, the triangle-shape carbon fibers and the roundshape carbon fibers were used to manufacture the CFRP. The effects of the shape of carbon fibers on flexural properties were investigated. The purpose of this paper is to report the effect of the triangle-shape
⁎ Corresponding author. E-mail address: [email protected] (R. Wang). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.01.003
carbon fiber on the mechanical properties of the unidirectional triangle-shape carbon fiber reinforced plastics. Furthermore, the microstructures of the carbon fibers and the carbon fiber reinforced plastics were studied with regard to cross-section shape of carbon fibers. 2. Experimental Commercially available raw materials were used in this study. The triangle-shape carbon fibers and the round-shape carbon fibers were supplied from Shanxi Institute of Coal Chemistry, China. The epoxy resin TDE-85 and the curing agent m-phenylenediamine used in the experiment were from Tianjin Resin Plant, China. And the manufacturer supplied some basic parameters of these raw materials. There are not almost differences about the basic properties of reinforcement materials. Unidirectional carbon fiber reinforced plastics were fabricated by filament winding machine. Under the curing cycle as shown in Fig. 1, the triangle-shape carbon fiber reinforced plastics and the circle-shape carbon fiber reinforced plastics were cured. The carbon fiber volume fraction of specimens was controlled to be approximate 50%. The microstructural features of carbon fibers and CFRP were observed by scanning electron microscopy (SEM, Philips XL30 ESEM-FEG), and the working voltage was set to 15.0 kV in experiment [9–12]. For carbon fibers and carbon fiber reinforced plastics, the magnification was set to 10 k and 3 k respectively. Based on the three point bending test, flexural property was investigated on the 2 mm by 15 mm by 80 mm bars by Zwick/Roell universal testing machine, using a 40 mm span and a crosshead speed of
22
X. Liu et al. / Materials Letters 73 (2012) 21–23 Table 1 Mechanical properties of triangle-shape carbon fiber reinforced plastics and roundshape carbon fiber reinforced plastics.
Triangle-shape carbon fiber reinforced plastics Round-shape carbon fiber reinforced plastics
Fig. 1. Curing cycle for the carbon fiber reinforced plastics.
0.5 mm/min. A minimum number of five specimens were tested [13–15].
3. Results and discussion The micrographs of carbon fibers and carbon fiber reinforced plastics are shown in Fig. 2. By the Fig. 2 (a) and (b), the shape of carbon fibers could be identified and the cross-section perimeters of triangle-shape carbon fiber and round-shape carbon fiber were measured to be 28.5 μm and 22.0 μm respectively, which means that the interfacial contact area between triangle-shape
Flexural strength/MPa
Flexural modulus/GPa
1797
115
1500
102
carbon fibers and epoxy resin is larger than the one between round-shape carbon fibers and epoxy resin. Fig. 2 (c) and (d) shows the polished surface of carbon fiber reinforced plastics, revealing a uniform distribution of carbon fibers in the epoxy resin TDE-85 matrix. The results of the flexural properties are listed in Table 1. The average flexural strength of triangle-shape carbon fiber reinforced plastics is 1797 MPa, which increases by 19.8% for the result of the round-shape carbon fiber reinforced plastics (average value is 1500 MPa). For the flexural modulus, the value of the triangleshape carbon fiber reinforced plastics is higher than the datum of the round-shape carbon fiber reinforced plastics by 12.8%, which was due to the higher specific surface area of triangle-shape carbon fibers than conventional round-shape carbon fibers. The flexural loading performance is one of the critical concerns for carbon fiber reinforced plastics, but the flexural property of the conventional unidirectional carbon fiber reinforced plastics is usually weak. This disadvantage limits the development and application of
b
a
2.0µm
2.0µm
d
c
40µm
40µm
Fig. 2. SEM micrographs of triangle-shape carbon fiber and round-shape carbon fiber; (a) triangle-shape carbon fiber, (b) round-shape carbon fiber, (c) triangle-shape carbon fiber reinforced plastics, and (d) round-shape carbon fiber reinforced plastics.
X. Liu et al. / Materials Letters 73 (2012) 21–23
23
b
a
40µm
40µm
Fig. 3. SEM micrographs of fracture surface of carbon fiber reinforced plastics after flextural tests; (a) triangle-shape carbon fiber reinforced plastics, and (b) round-shape carbon fiber reinforced plastics.
the unidirectional carbon fiber reinforced plastics [13,16,17].This study clearly showed the triangle-shape carbon fiber could improve the flexural properties of carbon fiber reinforced plastics, whilst the tensile strength and tensile modulus did not reduced. The increase in flexural properties of the triangle-shape carbon fiber reinforced plastics may be due to the large interfacial contact area between carbon fibers and epoxy resin, which could effectively transfer the applied load and enforce the interfacial binding force [13,18]. Fig. 3 shows the fracture surface of carbon fiber reinforced plastics after bend test. The triangle-shape carbon fiber and epoxy resin showed good interfacial adhesion and gave rise to rough surface microstructures of fractured bend test samples, as shown in Fig. 3 (a). Interface debonding occurred between the round-shape carbon fiber and epoxy resin, as indicated by the smooth carbon fiber surfaces in Fig. 3 (b). 4. Conclusion Triangle-shape carbon fiber reinforced plastics containing approximately 50 vol.% carbon fibers were fabricated by filament winding. The flexural strength and modulus were higher than that of roundshape carbon fiber reinforced plastics, increased by 19.8% and 12.8% respectively. The improvement was attributed to observed crosssection perimeters of carbon fibers and fracture surface of carbon fiber reinforced plastics, which could effectively transfer the applied load and enforce the interfacial binding force. The results presented in this paper point to the new carbon fiber with triangle-shape cross-section could effectively improve the flexural properties without decreasing the tensile properties for unidirectional carbon fiber reinforced plastics. It will be a new promising structure material. References [1] Bai YP, Wang Z, Feng LQ. Interface properties of carbon fiber/epoxy resin composite improved by supercritical water and oxygen in supercritical water. Mater Des 2010;31:1613–6.
[2] Bai YP, Wang Z, Feng LQ. Chemical recycling of carbon fibers reinforced epoxy resin composites in oxygen in supercritical water. Mater Des 2010;31:999–1002. [3] Coqueret X, Krzeminski M, Ponsaud P, Defoort B. Recent advances in electronbeam curing of carbon fiber-reinforced composites. Radiat Phys Chem 2009;78: 557–61. [4] Zhou YX, Wang Y, Xia YM, Jeelani S. Tensile behavior of carbon fiber bundles at different strain rates. Mater Lett 2010;64:246–8. [5] Squires CA, Netting KH, Chambers AR. Understanding the factors affecting the compressive testing of unidirectional carbon fibre composites. Composites Part B 2007;38:481–7. [6] Park SJ, Seo MK, Shim HB. Effect of fiber shapes on physical characteristics of noncircular carbon fibers-reinforced composites. Mater Sci Eng A 2003;352:34–9. [7] Harper LT, Turner TA, Warrior NA, Rudd CD. Characterisation of random carbon fibre composites from a directed fibre preforming process: the effect of fibre length. Composites Part A 2006;37:1863–78. [8] Xu ZW, Li JL, Wu XQ, Huang YD, Chen L, Zhang GL. Effect of kidney-type and circular cross sections on carbon fiber surface and composite interface. Composites Part A 2008;39:301–7. [9] Zhao F, Huang YD. Improved interfacial properties of carbon fiber/epoxy composites through grafting polyhedral oligomeric silsesquioxane on carbon fiber surface. Mater Lett 2010;64:2742–4. [10] Ersoy N, Garstka T, Potter K, Wisnom MR, Porter D, Clegg M, et al. Development of the properties of a carbon fibre reinforced thermosetting composite through cure. Composites Part A 2010;41:401–9. [11] Harper LT, Turner TA, Warrior NA, Dahl JS, Rudd CD. Characterisation of random carbon fibre composites from a directed fibre preforming process: analysis of microstructural parameters. Composites Part A 2006;37:2136–47. [12] Gao SL, Mader E, Zhandarov SF. Carbon fibers and composites with epoxy resins: topography, fractography and interphases. Carbon 2004;42:515–29. [13] Fujihara K, Huang ZM, Ramakrishna S, Hamada H. Influence of processing conditions on bending property of continuous carbon fiber reinforced PEEK composites. Compos Sci Technol 2004;64:2525–34. [14] Chambers AR, Earl JS, Squires CA, Suhot MA. The effect of voids on the flexural fatigue performance of unidirectional carbon fibre composites developed for wind turbine applications. Int J Fatigue 2006;28:1389–98. [15] Zhang XH, Xu L, Du SY, Han JC, Hu P, Han WB. Fabrication and mechanical properties of ZrB2–SiCw ceramic matrix composite. Mater Lett 2008;62:1058–60. [16] Figiel ECB, Rezende MC, Lauke B. Mechanical behavior of carbon fiber reinforced polyamide composites. Compos Sci Technol 2003;63:1843–55. [17] Godara A, Mezzo L, Luizi F, Warrier A, Lomov SV, Vuure AWV, et al. Influence of carbon nanotube reinforcement on the processing and the mechanical behaviour of carbon fiber/epoxy composites. Carbon 2009;47:2914–23. [18] He PG, Jia DC, Lin TS, Wang MR, Zhou Y. Effects of high-temperature heat treatment on the mechanical properties of unidirectional carbon fiber reinforced geopolymer composites. Ceram Int 2010;36:1447–53.
Contents lists available at SciVerse ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
The effect of triangle-shape carbon fiber on the flexural properties of the carbon fiber reinforced plastics Xin Liu a, b, Rongguo Wang b,⁎, Zhanjun Wu a, Wenbo Liu b a School of Aeronautics and Astronautics, Faculty of Vehicle Engineering and Mechanics, State Key Laboratory of Structural Analysis for Industrial Equipment, Dalian University of Technology, Dalian 116024, P.R. China b National Key laboratory of Science and Technology on advanced composites in Special Environments, Harbin Institute of Technology, Harbin 150001, P.R. China
a r t i c l e
i n f o
Article history: Received 26 October 2011 Accepted 2 January 2012 Available online 8 January 2012 Keywords: Polymeric composites Carbon materials Structural Microstructure
a b s t r a c t The triangle-shape carbon fiber reinforced plastics and the round-shape carbon fiber reinforced plastics were manufactured and the effects of carbon fiber shapes on the flexural properties were investigated. The microstructures and the cross-section areas of the round-shape carbon fiber and the triangle-shape carbon fiber were discussed. As a result, it was found that the triangle-shape carbon fiber reinforced plastics showed higher flexural strength and flexural modulus than round-shape carbon fiber reinforced plastics, and the tensile strength and tensile modulus did not reduced, which was attributed to that the triangle-shape carbon fiber reinforced plastics had larger interfacial contact area than round-shape ones, and the wider interfacial contact area between reinforcement and matrix that could effectively transfer the applied load. The flexural properties of fiber reinforced plastics were improved due to the stronger interfacial binding force. © 2012 Elsevier B.V. All rights reserved.
1. Introduction The use of carbon fiber reinforced plastics (CFRP) has grown considerably in recent years, especially in the aeronautic, aerospace, sporting and automotive industries. CFRP offers unique advantages in terms of their high strength to weight ratio, high stiffness to weight ratio and good corrosive properties [1–3]. The physical and mechanical properties of CFRP are dependent largely on the fiber content, the fiber orientation, the shape of fiber, and variability in the matrix materials [4,5]. In general, the cross-section shape of the reinforcing fibers in composites is round-shape. In structural mechanics, as the optimization of the stress distribution of materials, it is recognized that non-round-shape fiber is better than round-shape fiber in mechanical properties in CFRP [6–8]. The triangle-shape carbon fibers have higher specific surface area than conventional round-shape carbon fibers. The larger area in the surface contacting with matrix can enhance interfacial binding force, consequently could improve the correlative mechanical properties. At present, there are only a limited number of studies on the different cross-section shape of carbon fiber. In this study, the triangle-shape carbon fibers and the roundshape carbon fibers were used to manufacture the CFRP. The effects of the shape of carbon fibers on flexural properties were investigated. The purpose of this paper is to report the effect of the triangle-shape
⁎ Corresponding author. E-mail address: [email protected] (R. Wang). 0167-577X/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2012.01.003
carbon fiber on the mechanical properties of the unidirectional triangle-shape carbon fiber reinforced plastics. Furthermore, the microstructures of the carbon fibers and the carbon fiber reinforced plastics were studied with regard to cross-section shape of carbon fibers. 2. Experimental Commercially available raw materials were used in this study. The triangle-shape carbon fibers and the round-shape carbon fibers were supplied from Shanxi Institute of Coal Chemistry, China. The epoxy resin TDE-85 and the curing agent m-phenylenediamine used in the experiment were from Tianjin Resin Plant, China. And the manufacturer supplied some basic parameters of these raw materials. There are not almost differences about the basic properties of reinforcement materials. Unidirectional carbon fiber reinforced plastics were fabricated by filament winding machine. Under the curing cycle as shown in Fig. 1, the triangle-shape carbon fiber reinforced plastics and the circle-shape carbon fiber reinforced plastics were cured. The carbon fiber volume fraction of specimens was controlled to be approximate 50%. The microstructural features of carbon fibers and CFRP were observed by scanning electron microscopy (SEM, Philips XL30 ESEM-FEG), and the working voltage was set to 15.0 kV in experiment [9–12]. For carbon fibers and carbon fiber reinforced plastics, the magnification was set to 10 k and 3 k respectively. Based on the three point bending test, flexural property was investigated on the 2 mm by 15 mm by 80 mm bars by Zwick/Roell universal testing machine, using a 40 mm span and a crosshead speed of
22
X. Liu et al. / Materials Letters 73 (2012) 21–23 Table 1 Mechanical properties of triangle-shape carbon fiber reinforced plastics and roundshape carbon fiber reinforced plastics.
Triangle-shape carbon fiber reinforced plastics Round-shape carbon fiber reinforced plastics
Fig. 1. Curing cycle for the carbon fiber reinforced plastics.
0.5 mm/min. A minimum number of five specimens were tested [13–15].
3. Results and discussion The micrographs of carbon fibers and carbon fiber reinforced plastics are shown in Fig. 2. By the Fig. 2 (a) and (b), the shape of carbon fibers could be identified and the cross-section perimeters of triangle-shape carbon fiber and round-shape carbon fiber were measured to be 28.5 μm and 22.0 μm respectively, which means that the interfacial contact area between triangle-shape
Flexural strength/MPa
Flexural modulus/GPa
1797
115
1500
102
carbon fibers and epoxy resin is larger than the one between round-shape carbon fibers and epoxy resin. Fig. 2 (c) and (d) shows the polished surface of carbon fiber reinforced plastics, revealing a uniform distribution of carbon fibers in the epoxy resin TDE-85 matrix. The results of the flexural properties are listed in Table 1. The average flexural strength of triangle-shape carbon fiber reinforced plastics is 1797 MPa, which increases by 19.8% for the result of the round-shape carbon fiber reinforced plastics (average value is 1500 MPa). For the flexural modulus, the value of the triangleshape carbon fiber reinforced plastics is higher than the datum of the round-shape carbon fiber reinforced plastics by 12.8%, which was due to the higher specific surface area of triangle-shape carbon fibers than conventional round-shape carbon fibers. The flexural loading performance is one of the critical concerns for carbon fiber reinforced plastics, but the flexural property of the conventional unidirectional carbon fiber reinforced plastics is usually weak. This disadvantage limits the development and application of
b
a
2.0µm
2.0µm
d
c
40µm
40µm
Fig. 2. SEM micrographs of triangle-shape carbon fiber and round-shape carbon fiber; (a) triangle-shape carbon fiber, (b) round-shape carbon fiber, (c) triangle-shape carbon fiber reinforced plastics, and (d) round-shape carbon fiber reinforced plastics.
X. Liu et al. / Materials Letters 73 (2012) 21–23
23
b
a
40µm
40µm
Fig. 3. SEM micrographs of fracture surface of carbon fiber reinforced plastics after flextural tests; (a) triangle-shape carbon fiber reinforced plastics, and (b) round-shape carbon fiber reinforced plastics.
the unidirectional carbon fiber reinforced plastics [13,16,17].This study clearly showed the triangle-shape carbon fiber could improve the flexural properties of carbon fiber reinforced plastics, whilst the tensile strength and tensile modulus did not reduced. The increase in flexural properties of the triangle-shape carbon fiber reinforced plastics may be due to the large interfacial contact area between carbon fibers and epoxy resin, which could effectively transfer the applied load and enforce the interfacial binding force [13,18]. Fig. 3 shows the fracture surface of carbon fiber reinforced plastics after bend test. The triangle-shape carbon fiber and epoxy resin showed good interfacial adhesion and gave rise to rough surface microstructures of fractured bend test samples, as shown in Fig. 3 (a). Interface debonding occurred between the round-shape carbon fiber and epoxy resin, as indicated by the smooth carbon fiber surfaces in Fig. 3 (b). 4. Conclusion Triangle-shape carbon fiber reinforced plastics containing approximately 50 vol.% carbon fibers were fabricated by filament winding. The flexural strength and modulus were higher than that of roundshape carbon fiber reinforced plastics, increased by 19.8% and 12.8% respectively. The improvement was attributed to observed crosssection perimeters of carbon fibers and fracture surface of carbon fiber reinforced plastics, which could effectively transfer the applied load and enforce the interfacial binding force. The results presented in this paper point to the new carbon fiber with triangle-shape cross-section could effectively improve the flexural properties without decreasing the tensile properties for unidirectional carbon fiber reinforced plastics. It will be a new promising structure material. References [1] Bai YP, Wang Z, Feng LQ. Interface properties of carbon fiber/epoxy resin composite improved by supercritical water and oxygen in supercritical water. Mater Des 2010;31:1613–6.
[2] Bai YP, Wang Z, Feng LQ. Chemical recycling of carbon fibers reinforced epoxy resin composites in oxygen in supercritical water. Mater Des 2010;31:999–1002. [3] Coqueret X, Krzeminski M, Ponsaud P, Defoort B. Recent advances in electronbeam curing of carbon fiber-reinforced composites. Radiat Phys Chem 2009;78: 557–61. [4] Zhou YX, Wang Y, Xia YM, Jeelani S. Tensile behavior of carbon fiber bundles at different strain rates. Mater Lett 2010;64:246–8. [5] Squires CA, Netting KH, Chambers AR. Understanding the factors affecting the compressive testing of unidirectional carbon fibre composites. Composites Part B 2007;38:481–7. [6] Park SJ, Seo MK, Shim HB. Effect of fiber shapes on physical characteristics of noncircular carbon fibers-reinforced composites. Mater Sci Eng A 2003;352:34–9. [7] Harper LT, Turner TA, Warrior NA, Rudd CD. Characterisation of random carbon fibre composites from a directed fibre preforming process: the effect of fibre length. Composites Part A 2006;37:1863–78. [8] Xu ZW, Li JL, Wu XQ, Huang YD, Chen L, Zhang GL. Effect of kidney-type and circular cross sections on carbon fiber surface and composite interface. Composites Part A 2008;39:301–7. [9] Zhao F, Huang YD. Improved interfacial properties of carbon fiber/epoxy composites through grafting polyhedral oligomeric silsesquioxane on carbon fiber surface. Mater Lett 2010;64:2742–4. [10] Ersoy N, Garstka T, Potter K, Wisnom MR, Porter D, Clegg M, et al. Development of the properties of a carbon fibre reinforced thermosetting composite through cure. Composites Part A 2010;41:401–9. [11] Harper LT, Turner TA, Warrior NA, Dahl JS, Rudd CD. Characterisation of random carbon fibre composites from a directed fibre preforming process: analysis of microstructural parameters. Composites Part A 2006;37:2136–47. [12] Gao SL, Mader E, Zhandarov SF. Carbon fibers and composites with epoxy resins: topography, fractography and interphases. Carbon 2004;42:515–29. [13] Fujihara K, Huang ZM, Ramakrishna S, Hamada H. Influence of processing conditions on bending property of continuous carbon fiber reinforced PEEK composites. Compos Sci Technol 2004;64:2525–34. [14] Chambers AR, Earl JS, Squires CA, Suhot MA. The effect of voids on the flexural fatigue performance of unidirectional carbon fibre composites developed for wind turbine applications. Int J Fatigue 2006;28:1389–98. [15] Zhang XH, Xu L, Du SY, Han JC, Hu P, Han WB. Fabrication and mechanical properties of ZrB2–SiCw ceramic matrix composite. Mater Lett 2008;62:1058–60. [16] Figiel ECB, Rezende MC, Lauke B. Mechanical behavior of carbon fiber reinforced polyamide composites. Compos Sci Technol 2003;63:1843–55. [17] Godara A, Mezzo L, Luizi F, Warrier A, Lomov SV, Vuure AWV, et al. Influence of carbon nanotube reinforcement on the processing and the mechanical behaviour of carbon fiber/epoxy composites. Carbon 2009;47:2914–23. [18] He PG, Jia DC, Lin TS, Wang MR, Zhou Y. Effects of high-temperature heat treatment on the mechanical properties of unidirectional carbon fiber reinforced geopolymer composites. Ceram Int 2010;36:1447–53.