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epoxy resin composites with different layer angle
Materials Letters 142 (2015) 242–245
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Electromagnetic interference shielding properties of carbonyl iron powder-carbon fiber felt/epoxy resin composites with different layer angle Tao Hu n, Jun Wang, Julin Wang, Runhua Chen School of material science and engineering, Wuhan University of Technology, Luoshi Road No. 122, 430070 Wuhan, China
art ic l e i nf o
a b s t r a c t
Article history: Received 10 September 2014 Accepted 4 December 2014 Available online 13 December 2014
Carbonyl iron powder-carbon fiber felt/epoxy resin composites with different layer angles were prepared to evaluate electromagnetic interference shielding properties in the X band. The average shielding effectiveness decreased from 53.9 dB to 8.6 dB with increase in the layer angle from 1.981 to 84.61. The average power absorption coefficient increased first and then decreased, and had a maximum value at about 451. The volume conductivity and the average dielectric constant decreased with increase in layer angle. It is found that the composites shield by absorption and reflection and the ratio depends on layer angle. & 2014 Elsevier B.V. All rights reserved.
Keywords: Electrical properties Multilayer structure Electromagnetic interference shielding Layer angle
1. Introduction Electromagnetic interference (EMI) shielding materials are widely used in electric, aerospace and military applications because of the increasing electromagnetic interference problems [1–3]. Shielding effectiveness (SE) can evaluate the relative intensity between power of incident wave (PI) and power of transmitted wave (PT) after transmitting through shields and can be calculated as SE ¼10log(PI/PT). Metal-based shields and conductive polymermatrix composites are two main kinds of EMI shields with high SE, and conductive polymer-matrix composites can overcome the shortcomings (high cost in raw material and processing, prone to corrosion, and heavy weight) of metal-based shields [4–6]. Multilayer composites with radio wave absorber between layers are attracting great attention due to their high shielding effectiveness (SE) and large absorption loss (AL) [7–9]. The function layers are usually parallel to sample surface and supposed perpendicular to incident waves. However, if the function layers have included angles with the sample surface, the electric parameters and the EMI shielding properties will change remarkably, which needs further study. Carbon fiber felts (CFFs) with plane network structure are good shielding materials for good electric conductivity and good mechanical properties [10–12]. Carbonyl iron powders (CIPs) are good radio wave absorbers for prominent magnetic loss [13,14]. In this paper, CIP-CFF/epoxy resin (EP) composites were prepared n
Corresponding author. Tel.: þ 86 15827640909. E-mail address: [email protected] (T. Hu).
http://dx.doi.org/10.1016/j.matlet.2014.12.026 0167-577X/& 2014 Elsevier B.V. All rights reserved.
and made into samples with different layer angle to evaluate EMI shielding applications in the X band. Fig. 1(a) shows the angle between functional layers and sample surface which is named layer angle (θ). Since shielding properties and electric parameters are also affected by frequency, the tested values from 8.2 GHz to 12.4 GHz were calculated into average values to study the independent effect of layer angle.
2. Experimental The CIP-CFF/EP composites were prepared by vacuum bag molding. The mass ratio of the EP (CYD-128, epoxide group content: 0.0051 mol/g, Baling Petrochemical co., LTD, Hunan, China), the modified amine curing agent (active hydrogen content: 0.0213 mol/g, prepared by our laboratory) and CIP (diameter: 2.5 3.5 μm, mass content Z99.5%, Xingrongyuan Technology co., LTD, Beijing, China) was 100:24:75. The CFFs (fiber length: 6 mm, fiber diameter: 6 7 μm, areal density: 28 g/m2, Aoda Composite co., LTD, Shandong, China) were infiltrated by the mixed resin system to prepare prepregs. The composites were cured at the room temperature (about 25 1C) at 0.1 MPa for 24 h and post cured at 80 1C for 4 h. The composites were cut into samples at the designed size (22.86 10.16 4.00 70.02 mm) to fit the wave guild for the X band with the designed layer angle. The sample with layer angle (θ) was shown in Fig. 1(a). The layer angle of each sample was measured through image analysis on the side [the X–Z plane in Fig. 1(a)] of the sample. Fig. 1(b) shows the measurement of layer angle. The layer angle between fiber layers
T. Hu et al. / Materials Letters 142 (2015) 242–245
243
Fig. 1. (a) sample with layer angle (θ), and (b) measurement of layer angle through image analysis.
Fig. 2. SEM images of CIP-CFF/EP composites with different layer angle.
and sample surface were measured for 5 times and got the average value. The SEM (JSM-5610LV, Japan Electronics Ltd., Japan) analysis was on the surface [the X–Y plane in Fig. 1(a)] of the sample. The electrical conductivity was measured by the 4 probe resistance tester (RTS-8, 4 Probes Tech. Ltd, Guangzhou, China). The test direction was parallel to the X axis on the X–Y plane showed in Fig. 1(a). The shielding effectiveness, dielectric constant, and magnetic permeability were calculated by the scattering parameters (S11, S12, S21 and S22) measured through the vector network
analyzer (Agilent N5247A) and the wave guides for the X band whose inner dimensions were 22.86 mm 10.16 mm.
3. Results and discussions Fig. 2 shows the distribution of CIPs and carbon fibers in samples with different layer angle. (a) shows that carbon fiber network can be found in the sample surface with the layer angle
244
T. Hu et al. / Materials Letters 142 (2015) 242–245
Fig. 3. Variation of (a) average volume conductivity and (b) average real part and imaginary part of relative permittivity and relative permeability of CFF-CIP/EP composites with layer angle in the X band.
Fig. 4. Variation of (a) average shielding effectiveness and (b) average power constituent parts of the radio wave of CIP-CFF/EP composites with layer angle in the X band.
1.981. (b) shows that the CIPs distribute in the space between the carbon fibers and do not trend to adhere to the fiber surface. (c) shows the fiber sections at 20.181. (d–f) shows that the obscure fiber cross sections and the continuous carbon fiber can be found only in the junctures of fiber layers and sample surface. The SEM images analysis shows that the conductive network gradually destroys, the continuous fibers decrease and the fiber cross sections increase with increase in layer angle from 01 to 901. The SEM images also show that the CIPs are uniformly distributed in the resin matrix. Fig. 3(a) shows the volume conductivity of the composites decreases with increase in layer angle and the drop rate decreases. Fig. 3(b) shows the variation of real part and imaginary part of relative permittivity (εr0 and εr″) and relative permeability (μr' and μr″) of CFF-CIP/EP composites with layer angle. The εr0 , εr″, μr0 and μr″ were calculated by the scattering parameters through the Nicolson–Ross algorithm [15]. The εr0 and εr″ decrease with increase in layer angle and the drop rate decreases. The μr0 and μr″ increase first and then decrease, the maximum values appear at about 451. Because of three reasons: discontinuous fiber cross sections have lower conductivity than continuous fibers, conductive ability of carbon fiber on radial direction is lower than on axial direction, and contact resistance of two adjacent fibers is much
bigger than fiber itself, with increase in layer angle, SEM images show that continuous fiber network change to discontinuous fiber cross sections and leads to the falling down of electronic transfer efficiency, which leads to decrease in volume conductivity and relative permittivity. Since the loading of CIPs is at a low level and the distribution has only weak orientation, the relative permeability change non-significant with layer angle. Fig. 4 shows the variation of (a) average shielding effectiveness and (b) average power constituent parts [PT, reflected power (PR) and absorbed power (PA)] of radio wave of CIP-CFF/EP composites with layer angle in the X band. The SE decreases with increase in layer angle and the drop rate decreases. The power constituent parts (PT/PI, PR/PI and PA/PI) were calculated by the scattering parameters: P T =P I ¼ 10 jS21 j=10 , P R =P I ¼ 10 jS11 j=10 and PA/PI ¼ 1–PT/ PI–PR/PI. With increase in layer angle, the PR decreases and has a minimum value at about 451. The PA increases first and then decreases, the maximum value appears at about 451. The PT increases with increase in layer angle, the rise rate increases first and then decreases. It can be found that falling of SE are due to leaky wave through non-conductive areas between layers and decrease in volume conductivity and relative permittivity with increase in layer angle. The variation of the power ratio can be explained by the structure factors: with increase in layer angle, the
T. Hu et al. / Materials Letters 142 (2015) 242–245
conductive network gradually destroys, more radio wave can go into the sample and been absorbed by carbon fibers and CIPs, the reflection from the fibers improves the absorption path for the CIPs. The absorbed power arrives at a maximum value at about 451. And with further increase of layer angle, the reflection effect and the absorption path reduce, more radio waves trend to transmit through the interlamination between fiber layers.
245
Acknowledgment Authors are grateful to the financial support from the National Natural Science Foundation of China under the contract number 51373129.
References 4. Conclusion CIP-CFF/EP composites with different layer angle are prepared for EMI shielding applications in the X band. Shielding effectiveness decreases from 53.9 dB to 8.6 dB with increase in layer angle from 1.981 to 84.61. The ratio of reflected power and absorbed power decreases first and then increase with increase in layer angle. The reflected power has a minimum value, while the absorbed power has a maximum value at about 451. The volume conductivity and the relative dielectric constant decrease with increase in layer angle and leads to decrease of SE. The relative permeability increases first and then decreases, and has a maximum value at about 451. The variable SE is mainly due to the variation of the volume conductivity and the relative dielectric constant with layer angle, which indicates the potential of this composite for variable shielding applications. The results and techniques also suggest that the corner or curved surface of the shielding products with bigger layer angle is easy to leak wave, which needs special attention.
[1] Chung DDL. Carbon 2001;39:279–85. [2] von Klemperer Christopher J, Maharaj Denver. Compos Struct 2009;91: 467–72. [3] Micheli Davide, Apollo Carmelo, Pastore Roberto, Morles Ramon Bueno, Laurenzi Susanna, Marchetti Mario. Acta Astronautica 2011;69:747–57. [4] Ameli A, Jung PU, Park CB. Carbon 2013;60:379–91. [5] Huang Chi-Yuan, Mo Wen-Wei, Roan Ming-Lih. Surf Coat Technol 2004;184:163–9. [6] Tzeng Shinn-Shyong, Chang Fa-Yen. Mater Sci Eng 2001;A302:258–67. [7] Qu Zhaoming, Liu Shanghe, Wang Qingguo, Wang Yilong, Lei Yisan. Mater Lett 2013;109:42–5. [8] Chen Mingxia, Zhu Yong, Pan Yubai, Kou Huamin, Xu Heng, Guo Jingkun. Mater Des 2011;32:3013–6. [9] Gyu Park Jin, Louis Jeffrey, Cheng Qunfeng, Bao Jianwen, Smithyman Jesse. Nanotechnology 2009;20:415702. [10] Wong KH, Pickering SJ, Rudd CD. Compos: Part A 2010;41:693–702. [11] Zhao Naiqin, Zou Tianchun, Shi Chunsheng, Li Jiajun, Guo Weikai. Mater Sci Eng B 2006;127:207–11. [12] Jaehyun Kim Masatoshi Shioya, Kobayashi Haruki, Kaneko Junichi, Kido Masahiko. Compos Sci Technol 2004;64:2221–9. [13] Joseph Nina, Sebastian Mailadil Thomas. Mater Lett 2013;90:64–7. [14] Liu Lidong, Duan Yuping, Liu Shunhua, Chen Liyang, Guo Jingbo. J Magn Magn Mater 2010;322:1736–40. [15] Nicolson AM, Ross GF. IEEE Trans Instrum Measur 1970;19:377–82.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/matlet
Electromagnetic interference shielding properties of carbonyl iron powder-carbon fiber felt/epoxy resin composites with different layer angle Tao Hu n, Jun Wang, Julin Wang, Runhua Chen School of material science and engineering, Wuhan University of Technology, Luoshi Road No. 122, 430070 Wuhan, China
art ic l e i nf o
a b s t r a c t
Article history: Received 10 September 2014 Accepted 4 December 2014 Available online 13 December 2014
Carbonyl iron powder-carbon fiber felt/epoxy resin composites with different layer angles were prepared to evaluate electromagnetic interference shielding properties in the X band. The average shielding effectiveness decreased from 53.9 dB to 8.6 dB with increase in the layer angle from 1.981 to 84.61. The average power absorption coefficient increased first and then decreased, and had a maximum value at about 451. The volume conductivity and the average dielectric constant decreased with increase in layer angle. It is found that the composites shield by absorption and reflection and the ratio depends on layer angle. & 2014 Elsevier B.V. All rights reserved.
Keywords: Electrical properties Multilayer structure Electromagnetic interference shielding Layer angle
1. Introduction Electromagnetic interference (EMI) shielding materials are widely used in electric, aerospace and military applications because of the increasing electromagnetic interference problems [1–3]. Shielding effectiveness (SE) can evaluate the relative intensity between power of incident wave (PI) and power of transmitted wave (PT) after transmitting through shields and can be calculated as SE ¼10log(PI/PT). Metal-based shields and conductive polymermatrix composites are two main kinds of EMI shields with high SE, and conductive polymer-matrix composites can overcome the shortcomings (high cost in raw material and processing, prone to corrosion, and heavy weight) of metal-based shields [4–6]. Multilayer composites with radio wave absorber between layers are attracting great attention due to their high shielding effectiveness (SE) and large absorption loss (AL) [7–9]. The function layers are usually parallel to sample surface and supposed perpendicular to incident waves. However, if the function layers have included angles with the sample surface, the electric parameters and the EMI shielding properties will change remarkably, which needs further study. Carbon fiber felts (CFFs) with plane network structure are good shielding materials for good electric conductivity and good mechanical properties [10–12]. Carbonyl iron powders (CIPs) are good radio wave absorbers for prominent magnetic loss [13,14]. In this paper, CIP-CFF/epoxy resin (EP) composites were prepared n
Corresponding author. Tel.: þ 86 15827640909. E-mail address: [email protected] (T. Hu).
http://dx.doi.org/10.1016/j.matlet.2014.12.026 0167-577X/& 2014 Elsevier B.V. All rights reserved.
and made into samples with different layer angle to evaluate EMI shielding applications in the X band. Fig. 1(a) shows the angle between functional layers and sample surface which is named layer angle (θ). Since shielding properties and electric parameters are also affected by frequency, the tested values from 8.2 GHz to 12.4 GHz were calculated into average values to study the independent effect of layer angle.
2. Experimental The CIP-CFF/EP composites were prepared by vacuum bag molding. The mass ratio of the EP (CYD-128, epoxide group content: 0.0051 mol/g, Baling Petrochemical co., LTD, Hunan, China), the modified amine curing agent (active hydrogen content: 0.0213 mol/g, prepared by our laboratory) and CIP (diameter: 2.5 3.5 μm, mass content Z99.5%, Xingrongyuan Technology co., LTD, Beijing, China) was 100:24:75. The CFFs (fiber length: 6 mm, fiber diameter: 6 7 μm, areal density: 28 g/m2, Aoda Composite co., LTD, Shandong, China) were infiltrated by the mixed resin system to prepare prepregs. The composites were cured at the room temperature (about 25 1C) at 0.1 MPa for 24 h and post cured at 80 1C for 4 h. The composites were cut into samples at the designed size (22.86 10.16 4.00 70.02 mm) to fit the wave guild for the X band with the designed layer angle. The sample with layer angle (θ) was shown in Fig. 1(a). The layer angle of each sample was measured through image analysis on the side [the X–Z plane in Fig. 1(a)] of the sample. Fig. 1(b) shows the measurement of layer angle. The layer angle between fiber layers
T. Hu et al. / Materials Letters 142 (2015) 242–245
243
Fig. 1. (a) sample with layer angle (θ), and (b) measurement of layer angle through image analysis.
Fig. 2. SEM images of CIP-CFF/EP composites with different layer angle.
and sample surface were measured for 5 times and got the average value. The SEM (JSM-5610LV, Japan Electronics Ltd., Japan) analysis was on the surface [the X–Y plane in Fig. 1(a)] of the sample. The electrical conductivity was measured by the 4 probe resistance tester (RTS-8, 4 Probes Tech. Ltd, Guangzhou, China). The test direction was parallel to the X axis on the X–Y plane showed in Fig. 1(a). The shielding effectiveness, dielectric constant, and magnetic permeability were calculated by the scattering parameters (S11, S12, S21 and S22) measured through the vector network
analyzer (Agilent N5247A) and the wave guides for the X band whose inner dimensions were 22.86 mm 10.16 mm.
3. Results and discussions Fig. 2 shows the distribution of CIPs and carbon fibers in samples with different layer angle. (a) shows that carbon fiber network can be found in the sample surface with the layer angle
244
T. Hu et al. / Materials Letters 142 (2015) 242–245
Fig. 3. Variation of (a) average volume conductivity and (b) average real part and imaginary part of relative permittivity and relative permeability of CFF-CIP/EP composites with layer angle in the X band.
Fig. 4. Variation of (a) average shielding effectiveness and (b) average power constituent parts of the radio wave of CIP-CFF/EP composites with layer angle in the X band.
1.981. (b) shows that the CIPs distribute in the space between the carbon fibers and do not trend to adhere to the fiber surface. (c) shows the fiber sections at 20.181. (d–f) shows that the obscure fiber cross sections and the continuous carbon fiber can be found only in the junctures of fiber layers and sample surface. The SEM images analysis shows that the conductive network gradually destroys, the continuous fibers decrease and the fiber cross sections increase with increase in layer angle from 01 to 901. The SEM images also show that the CIPs are uniformly distributed in the resin matrix. Fig. 3(a) shows the volume conductivity of the composites decreases with increase in layer angle and the drop rate decreases. Fig. 3(b) shows the variation of real part and imaginary part of relative permittivity (εr0 and εr″) and relative permeability (μr' and μr″) of CFF-CIP/EP composites with layer angle. The εr0 , εr″, μr0 and μr″ were calculated by the scattering parameters through the Nicolson–Ross algorithm [15]. The εr0 and εr″ decrease with increase in layer angle and the drop rate decreases. The μr0 and μr″ increase first and then decrease, the maximum values appear at about 451. Because of three reasons: discontinuous fiber cross sections have lower conductivity than continuous fibers, conductive ability of carbon fiber on radial direction is lower than on axial direction, and contact resistance of two adjacent fibers is much
bigger than fiber itself, with increase in layer angle, SEM images show that continuous fiber network change to discontinuous fiber cross sections and leads to the falling down of electronic transfer efficiency, which leads to decrease in volume conductivity and relative permittivity. Since the loading of CIPs is at a low level and the distribution has only weak orientation, the relative permeability change non-significant with layer angle. Fig. 4 shows the variation of (a) average shielding effectiveness and (b) average power constituent parts [PT, reflected power (PR) and absorbed power (PA)] of radio wave of CIP-CFF/EP composites with layer angle in the X band. The SE decreases with increase in layer angle and the drop rate decreases. The power constituent parts (PT/PI, PR/PI and PA/PI) were calculated by the scattering parameters: P T =P I ¼ 10 jS21 j=10 , P R =P I ¼ 10 jS11 j=10 and PA/PI ¼ 1–PT/ PI–PR/PI. With increase in layer angle, the PR decreases and has a minimum value at about 451. The PA increases first and then decreases, the maximum value appears at about 451. The PT increases with increase in layer angle, the rise rate increases first and then decreases. It can be found that falling of SE are due to leaky wave through non-conductive areas between layers and decrease in volume conductivity and relative permittivity with increase in layer angle. The variation of the power ratio can be explained by the structure factors: with increase in layer angle, the
T. Hu et al. / Materials Letters 142 (2015) 242–245
conductive network gradually destroys, more radio wave can go into the sample and been absorbed by carbon fibers and CIPs, the reflection from the fibers improves the absorption path for the CIPs. The absorbed power arrives at a maximum value at about 451. And with further increase of layer angle, the reflection effect and the absorption path reduce, more radio waves trend to transmit through the interlamination between fiber layers.
245
Acknowledgment Authors are grateful to the financial support from the National Natural Science Foundation of China under the contract number 51373129.
References 4. Conclusion CIP-CFF/EP composites with different layer angle are prepared for EMI shielding applications in the X band. Shielding effectiveness decreases from 53.9 dB to 8.6 dB with increase in layer angle from 1.981 to 84.61. The ratio of reflected power and absorbed power decreases first and then increase with increase in layer angle. The reflected power has a minimum value, while the absorbed power has a maximum value at about 451. The volume conductivity and the relative dielectric constant decrease with increase in layer angle and leads to decrease of SE. The relative permeability increases first and then decreases, and has a maximum value at about 451. The variable SE is mainly due to the variation of the volume conductivity and the relative dielectric constant with layer angle, which indicates the potential of this composite for variable shielding applications. The results and techniques also suggest that the corner or curved surface of the shielding products with bigger layer angle is easy to leak wave, which needs special attention.
[1] Chung DDL. Carbon 2001;39:279–85. [2] von Klemperer Christopher J, Maharaj Denver. Compos Struct 2009;91: 467–72. [3] Micheli Davide, Apollo Carmelo, Pastore Roberto, Morles Ramon Bueno, Laurenzi Susanna, Marchetti Mario. Acta Astronautica 2011;69:747–57. [4] Ameli A, Jung PU, Park CB. Carbon 2013;60:379–91. [5] Huang Chi-Yuan, Mo Wen-Wei, Roan Ming-Lih. Surf Coat Technol 2004;184:163–9. [6] Tzeng Shinn-Shyong, Chang Fa-Yen. Mater Sci Eng 2001;A302:258–67. [7] Qu Zhaoming, Liu Shanghe, Wang Qingguo, Wang Yilong, Lei Yisan. Mater Lett 2013;109:42–5. [8] Chen Mingxia, Zhu Yong, Pan Yubai, Kou Huamin, Xu Heng, Guo Jingkun. Mater Des 2011;32:3013–6. [9] Gyu Park Jin, Louis Jeffrey, Cheng Qunfeng, Bao Jianwen, Smithyman Jesse. Nanotechnology 2009;20:415702. [10] Wong KH, Pickering SJ, Rudd CD. Compos: Part A 2010;41:693–702. [11] Zhao Naiqin, Zou Tianchun, Shi Chunsheng, Li Jiajun, Guo Weikai. Mater Sci Eng B 2006;127:207–11. [12] Jaehyun Kim Masatoshi Shioya, Kobayashi Haruki, Kaneko Junichi, Kido Masahiko. Compos Sci Technol 2004;64:2221–9. [13] Joseph Nina, Sebastian Mailadil Thomas. Mater Lett 2013;90:64–7. [14] Liu Lidong, Duan Yuping, Liu Shunhua, Chen Liyang, Guo Jingbo. J Magn Magn Mater 2010;322:1736–40. [15] Nicolson AM, Ross GF. IEEE Trans Instrum Measur 1970;19:377–82.