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epoxy Composites Beam
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ScienceDirect Procedia Engineering 79 (2014) 244 – 248
37th National Conference on Theoretical and Applied Mechanics (37th NCTAM 2013) & The 1st International Conference on Mechanics (1st ICM)
Vibration Characteristics of Multi-walled Carbon Nanotubes/epoxy Composites Beam Meng-Kao Yeha, Nyan-Hwa Taib, Dong-Syuan Lina,* a
b
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
Abstract Composites are composed of matrix and reinforcement. Generally the matrix is a polymer material. Carbon nanotubes have excellent mechanical properties, electrical and thermal properties and can be used as a reinforcement. In this study, multi-walled carbon nanotubes (MWNTs)/epoxy specimens was prepared with different MWNTs wt% to explore the vibration characteristics of composites beam. Vibration characteristics including mode shapes and natural frequencies. We measured the Young's modulus, Poisson's ratio and density of the specimens, used as the parameters in finite element analysis to obtain the mode shape and natural frequency of cantilever composite beams. The experiment and simulation results showed that adding MWNTs had some influence on the resonant frequency. ©©2014 Ltd. This is an open access article 2013Elsevier The Authors. Published by Elsevier Ltd. under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the National Tsing Hua University, Department of Power Mechanical Selection and peer-review under responsibility of the National Tsing Hua University, Department of Power Mechanical Engineering. Engineering Keywords: Composites beam; carbon nanotubes; vibration
1. Introduction Compared to a single material, the composite materials generally have a better performance. Recently, "nanocomposites" aroused the majority interest, it uses nanoscale reinforcing materials, such as carbon nanotubes [1]. Carbon nanotubes can be divided into multi-walled carbon nanotubes (MWNTs) and single-walled (SWNTs)
* Corresponding author. Tel.:+886 921708307. E-mail address: [email protected]
1877-7058 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Selection and peer-review under responsibility of the National Tsing Hua University, Department of Power Mechanical Engineering doi:10.1016/j.proeng.2014.06.338
Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
and MWNTs is used in this study. Compared to SWNTs, MWNTs is more easy to obtain in manufacturing processes [2]. Carbon nanotubes have superior mechanical properties and physical properties, its Young's modulus can be up to 1-5 TPa with high toughness, high thermal and electrical conductivity [3, 4]. Carbon nanotubes have been widely used in various fields, such as automotive protection components, semiconductor cooling mechanism, electromagnetic shielding material, etc. Rajoria and Jalili [5] used the CNT composites in the free vibration and forced vibration test, and showed that adding 5 wt% MWNTs in composites could increase 700 % of damping ratio compared to a pure epoxy specimen. This study aims to explore the vibration characteristics of MWNTs/epoxy composites. In this paper, MWNTs with diameter 20-40 nm was added to the epoxy as a reinforcement. Different weight percentage of MWNTs was added to explore the vibration characteristics of MWNTs/epoxy composites beam. 2. Experimental For preparation of specimen matrix, we use the dual formulations epoxy, divided into resin base and hardener, which is thermosetting type polymer materials. Curing conditions of the resin is to place at room temperature for 6-8 hours or to have 80 ć for 50 minutes. Reinforcement used for the study are MWNTs with a diameter of 20-40 nm, an average length of 5-15 μm, and purity ≥ 95%. 2.1. Specimen preparation In this study, to allow adequate dispersion of the reinforcement in the matrix, the sonication step was executed before vacuum treatment to scatter tiny clusters of carbon nanotubes in solution, then ruled out air bubbles by vacuum treatment. After pre-treatment steps, hot hardening process was applied. The mixed solution was poured into a stainless steel molds, in the hot air circulating oven at 70 ć for 30 min. Then the mix compound was placed into hot pressing machine at 120 ć for 2 hours. After the natural cooling to room temperature, the MWNTs/epoxy composites specimen was moved out of the molds for use. The contents of MWNTs were 1 wt%, 2 wt%, 3 wt%, 4 wt% in MWCNTs/epoxy composite specimen. 2.2. Vibration test The MWCNTs/epoxy composite specimen was cut into beams and tested according to ASTM E756-05 [6] specification for vibration measurements. The test piece was cut into length 180 mm, width 12 mm and thickness 3 mm, with a length of 30 mm fixed. The non-contact Doppler vibration instrument was used to measure the resonance frequencies of the composite beam. The Doppler vibration instrument emits laser light on specimen surface and the vibration signal reflects from a reflective sticker on specimen surface. The specimen was hit by a hammer at the tip, the vibration signal was captured through non-contact Doppler vibration instrument and resonant frequency could be obtained by taking the average of 10 measurements. The frequency range was set to 10-1000 Hz. 3. Results and Discussions The MWNTs/epoxy composite specimens with 1.0 wt%, 2.0 wt% , 3.0 wt%, 4.0 wt% MWNTs were first under tensile test to obtain the mechanical properties, the Young's modulus, Poisson's ratio, and density of the composites specimens. Fig. 1 shows the Young's modulus and the Poisson's ratio as a function of CNT weight percentage. The mechanical properties were then used in the finite element analysis.
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Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
(a)
(b)
Fig. 1. (a) Young’s modulus, (b) Poisson’s ratio as a function of CNT weight percentage.
Fig. 2 shows the resonance frequency as a function of MWNTs weight percentage. Fig. 3. shows the first to fourth mode shapes of MWNTs/epoxy composites beam. For the first, third and fourth modes display the bending behavior of up and down motion, while the second mode showed a transverse vibration mode. The resonant frequencies of the pure epoxy resin are, from the first to fourth modes, respectively 28.44 Hz, 144.84 Hz, 202.50 Hz, 544.22 Hz. Adding 1.0 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt% of MWNTs in the MWNTs/epoxy composites, the first mode changed 4.92%, 1.65%, -3.87%, -6.05 %; the second mode varied 4.96% -0.43% -5.28% -5.93%; the third mode changed 3.47%, -0.62%, -5.40%, -6.02%; and the fourth mode varied 5.57% , -0.60%, -5.20%, -6.00%. From the above results it concluded that adding the MWNTs into pure epoxy resin could change the resonance frequency of the MWNTs/epoxy composites in the four modes discussed.
Fig. 2. Resonance frequency as a function of MWNTs weight percentage.
Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
(a) Mode 1
(b) Mode 2
(c) Mode 3
(d) Mode 4
Fig. 3. Mode shapes of MWNTs/epoxy composites.
The finite element analysis software ANSYS ® [7] was used in this study to obtain the resonance frequency of MWCNTs/epoxy composites. To be consistent with the composite specimens used in experiment, the analysis model was set with length 150 mm, width 12 mm and thickness 3 mm. The Young's modulus, Poisson's ratio and density parameter were measured from experiments, and then used in finite element analysis. For the MWNTs/epoxy composites with 1.0 wt %, 2.0 wt%, 3.0 wt%, 4.0 wt% of MWNTs, the first mode changed 0.03%, 1.44%, 0.19%, -0.51%; The second mode varied 0.05%, 1.45%, 0.23% -0.50%; the third mode changed by 0.02%, 1.44%, 0.18% -0.52%; and the fourth mode varied for 0.01%, 1.44%, 0.18%, -0.52%. The simulation results showed that adding a small amount of MWNTs into pure epoxy to make MWNTs/epoxy composites caused the resonant frequency of each mode changed a certain amount. The highest increase appears for the case with 2 wt% MWNTs addition. Resonance frequencies of the four modes rise and fall a little, within 2.0%. Simulation results showed that the resonance frequency of the composites beam is closely related to its Young's modulus. When the Young's modulus rises, the resonance frequency increases also. By comparing the results from analysis and experiment, the experimental resonance frequencies did not exactly coincide with the simulation results. With the MWNTs higher than 2 wt%, the resonance frequency decreases for all four modes. The difference between the experiment and simulation results is about 10% or less; this may be caused by measurement error, boundary conditions, and the model size difference in simulation.
(a)
(b)
Fig. 4. SEM image of the fracture surface with (a) 2 wt% and (b) 4 wt% MWNTs composites.
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Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
Fig. 4 shows SEM micrographics to demonstrate the dispersion of the MWNTs within the epoxy matrix. From Fig. 4, both 2 wt% or 4 wt% samples have MWNTs aggregates at the fracture surface. The tangled MWNTs and roughness surface in higher loading sample demonstrate that the homogenization process of nanotubes was difficult. A weak interaction between the epoxy matrix and the nanotube lead to uncompletely covered and agglomeration [8]. This may explain why the introduction of MWNTs wouldn’t improve more mechanical properties of composites. 4. Conclusions In this paper, the vibration characteristics of MWNTs/epoxy composites beam was investigated. We used the Doppler vibration instrument to measure the resonant frequency of MWNTs/epoxy composites beam and the finite element code ANSYS was used in the vibration analysis. Simulation results showed that the resonance frequency of the composites beam is closely related to its Young's modulus. When the Young's modulus rises, the resonant frequency increases also. The experimental results showed that adding appropriate amounts of MWNTs can slightly increase the resonant frequency. These results can be used for future studies. Acknowledgements The work was sponsored by the National Science Council, Taiwan, ROC, under the grant NSC 99-2221-E-007042-MY3 and NSC 102-2221-E-007-030-MY3. The support is greatly acknowledged. References [1] [2] [3] [4] [5] [6] [7] [8]
R.F. Gibson, Principles of Composite Material Mechanics, McGraw-Hill, New York, U. S., 1997. H.M. Cheng, Carbon Nanotubes, Wu-Nan Book Inc., Taipei, Taiwan, 2004. M.F. Yu, O. Lourie, M.J. Dyer, K. Moloni, T.F. Kelly, R.S. Ruoff, Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load, Science 287 (2000) 637–640. A. Allaoui, S. Bai, H.M. Cheng, J.B. Bai, Mechanical and electrical properties of a MWNT/epoxy composite, Composites Science and Technology 62 (2002) 1993–1998. H. Rajoria, N. Jalili, Passive vibration damping enhancement using carbon nanotube-epoxy reinforced composites, Composites Science and Technology 65 (2005) 2079–2093. ASTM E756-05, Standard Test Method for Measuring Vibration-Damping Properties of Materials, Annual Book of ASTM Standards 8.1.,2010. ANSYS Release 12.1, ANSYS, Inc., PA, 2009. F.H. Gojny, J. Nastalczyk, Z. Roslaniec, K. Schulte, Surface modified multi-walled carbon nanotubes in CNT/epoxy-composites, Chemical Physics Letters 370 (2003) 820–824.
ScienceDirect Procedia Engineering 79 (2014) 244 – 248
37th National Conference on Theoretical and Applied Mechanics (37th NCTAM 2013) & The 1st International Conference on Mechanics (1st ICM)
Vibration Characteristics of Multi-walled Carbon Nanotubes/epoxy Composites Beam Meng-Kao Yeha, Nyan-Hwa Taib, Dong-Syuan Lina,* a
b
Department of Power Mechanical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan
Abstract Composites are composed of matrix and reinforcement. Generally the matrix is a polymer material. Carbon nanotubes have excellent mechanical properties, electrical and thermal properties and can be used as a reinforcement. In this study, multi-walled carbon nanotubes (MWNTs)/epoxy specimens was prepared with different MWNTs wt% to explore the vibration characteristics of composites beam. Vibration characteristics including mode shapes and natural frequencies. We measured the Young's modulus, Poisson's ratio and density of the specimens, used as the parameters in finite element analysis to obtain the mode shape and natural frequency of cantilever composite beams. The experiment and simulation results showed that adding MWNTs had some influence on the resonant frequency. ©©2014 Ltd. This is an open access article 2013Elsevier The Authors. Published by Elsevier Ltd. under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/). Selection and peer-review under responsibility of the National Tsing Hua University, Department of Power Mechanical Selection and peer-review under responsibility of the National Tsing Hua University, Department of Power Mechanical Engineering. Engineering Keywords: Composites beam; carbon nanotubes; vibration
1. Introduction Compared to a single material, the composite materials generally have a better performance. Recently, "nanocomposites" aroused the majority interest, it uses nanoscale reinforcing materials, such as carbon nanotubes [1]. Carbon nanotubes can be divided into multi-walled carbon nanotubes (MWNTs) and single-walled (SWNTs)
* Corresponding author. Tel.:+886 921708307. E-mail address: [email protected]
1877-7058 © 2014 Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/3.0/).
Selection and peer-review under responsibility of the National Tsing Hua University, Department of Power Mechanical Engineering doi:10.1016/j.proeng.2014.06.338
Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
and MWNTs is used in this study. Compared to SWNTs, MWNTs is more easy to obtain in manufacturing processes [2]. Carbon nanotubes have superior mechanical properties and physical properties, its Young's modulus can be up to 1-5 TPa with high toughness, high thermal and electrical conductivity [3, 4]. Carbon nanotubes have been widely used in various fields, such as automotive protection components, semiconductor cooling mechanism, electromagnetic shielding material, etc. Rajoria and Jalili [5] used the CNT composites in the free vibration and forced vibration test, and showed that adding 5 wt% MWNTs in composites could increase 700 % of damping ratio compared to a pure epoxy specimen. This study aims to explore the vibration characteristics of MWNTs/epoxy composites. In this paper, MWNTs with diameter 20-40 nm was added to the epoxy as a reinforcement. Different weight percentage of MWNTs was added to explore the vibration characteristics of MWNTs/epoxy composites beam. 2. Experimental For preparation of specimen matrix, we use the dual formulations epoxy, divided into resin base and hardener, which is thermosetting type polymer materials. Curing conditions of the resin is to place at room temperature for 6-8 hours or to have 80 ć for 50 minutes. Reinforcement used for the study are MWNTs with a diameter of 20-40 nm, an average length of 5-15 μm, and purity ≥ 95%. 2.1. Specimen preparation In this study, to allow adequate dispersion of the reinforcement in the matrix, the sonication step was executed before vacuum treatment to scatter tiny clusters of carbon nanotubes in solution, then ruled out air bubbles by vacuum treatment. After pre-treatment steps, hot hardening process was applied. The mixed solution was poured into a stainless steel molds, in the hot air circulating oven at 70 ć for 30 min. Then the mix compound was placed into hot pressing machine at 120 ć for 2 hours. After the natural cooling to room temperature, the MWNTs/epoxy composites specimen was moved out of the molds for use. The contents of MWNTs were 1 wt%, 2 wt%, 3 wt%, 4 wt% in MWCNTs/epoxy composite specimen. 2.2. Vibration test The MWCNTs/epoxy composite specimen was cut into beams and tested according to ASTM E756-05 [6] specification for vibration measurements. The test piece was cut into length 180 mm, width 12 mm and thickness 3 mm, with a length of 30 mm fixed. The non-contact Doppler vibration instrument was used to measure the resonance frequencies of the composite beam. The Doppler vibration instrument emits laser light on specimen surface and the vibration signal reflects from a reflective sticker on specimen surface. The specimen was hit by a hammer at the tip, the vibration signal was captured through non-contact Doppler vibration instrument and resonant frequency could be obtained by taking the average of 10 measurements. The frequency range was set to 10-1000 Hz. 3. Results and Discussions The MWNTs/epoxy composite specimens with 1.0 wt%, 2.0 wt% , 3.0 wt%, 4.0 wt% MWNTs were first under tensile test to obtain the mechanical properties, the Young's modulus, Poisson's ratio, and density of the composites specimens. Fig. 1 shows the Young's modulus and the Poisson's ratio as a function of CNT weight percentage. The mechanical properties were then used in the finite element analysis.
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Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
(a)
(b)
Fig. 1. (a) Young’s modulus, (b) Poisson’s ratio as a function of CNT weight percentage.
Fig. 2 shows the resonance frequency as a function of MWNTs weight percentage. Fig. 3. shows the first to fourth mode shapes of MWNTs/epoxy composites beam. For the first, third and fourth modes display the bending behavior of up and down motion, while the second mode showed a transverse vibration mode. The resonant frequencies of the pure epoxy resin are, from the first to fourth modes, respectively 28.44 Hz, 144.84 Hz, 202.50 Hz, 544.22 Hz. Adding 1.0 wt%, 2.0 wt%, 3.0 wt%, 4.0 wt% of MWNTs in the MWNTs/epoxy composites, the first mode changed 4.92%, 1.65%, -3.87%, -6.05 %; the second mode varied 4.96% -0.43% -5.28% -5.93%; the third mode changed 3.47%, -0.62%, -5.40%, -6.02%; and the fourth mode varied 5.57% , -0.60%, -5.20%, -6.00%. From the above results it concluded that adding the MWNTs into pure epoxy resin could change the resonance frequency of the MWNTs/epoxy composites in the four modes discussed.
Fig. 2. Resonance frequency as a function of MWNTs weight percentage.
Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
(a) Mode 1
(b) Mode 2
(c) Mode 3
(d) Mode 4
Fig. 3. Mode shapes of MWNTs/epoxy composites.
The finite element analysis software ANSYS ® [7] was used in this study to obtain the resonance frequency of MWCNTs/epoxy composites. To be consistent with the composite specimens used in experiment, the analysis model was set with length 150 mm, width 12 mm and thickness 3 mm. The Young's modulus, Poisson's ratio and density parameter were measured from experiments, and then used in finite element analysis. For the MWNTs/epoxy composites with 1.0 wt %, 2.0 wt%, 3.0 wt%, 4.0 wt% of MWNTs, the first mode changed 0.03%, 1.44%, 0.19%, -0.51%; The second mode varied 0.05%, 1.45%, 0.23% -0.50%; the third mode changed by 0.02%, 1.44%, 0.18% -0.52%; and the fourth mode varied for 0.01%, 1.44%, 0.18%, -0.52%. The simulation results showed that adding a small amount of MWNTs into pure epoxy to make MWNTs/epoxy composites caused the resonant frequency of each mode changed a certain amount. The highest increase appears for the case with 2 wt% MWNTs addition. Resonance frequencies of the four modes rise and fall a little, within 2.0%. Simulation results showed that the resonance frequency of the composites beam is closely related to its Young's modulus. When the Young's modulus rises, the resonance frequency increases also. By comparing the results from analysis and experiment, the experimental resonance frequencies did not exactly coincide with the simulation results. With the MWNTs higher than 2 wt%, the resonance frequency decreases for all four modes. The difference between the experiment and simulation results is about 10% or less; this may be caused by measurement error, boundary conditions, and the model size difference in simulation.
(a)
(b)
Fig. 4. SEM image of the fracture surface with (a) 2 wt% and (b) 4 wt% MWNTs composites.
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Meng-Kao Yeh et al. / Procedia Engineering 79 (2014) 244 – 248
Fig. 4 shows SEM micrographics to demonstrate the dispersion of the MWNTs within the epoxy matrix. From Fig. 4, both 2 wt% or 4 wt% samples have MWNTs aggregates at the fracture surface. The tangled MWNTs and roughness surface in higher loading sample demonstrate that the homogenization process of nanotubes was difficult. A weak interaction between the epoxy matrix and the nanotube lead to uncompletely covered and agglomeration [8]. This may explain why the introduction of MWNTs wouldn’t improve more mechanical properties of composites. 4. Conclusions In this paper, the vibration characteristics of MWNTs/epoxy composites beam was investigated. We used the Doppler vibration instrument to measure the resonant frequency of MWNTs/epoxy composites beam and the finite element code ANSYS was used in the vibration analysis. Simulation results showed that the resonance frequency of the composites beam is closely related to its Young's modulus. When the Young's modulus rises, the resonant frequency increases also. The experimental results showed that adding appropriate amounts of MWNTs can slightly increase the resonant frequency. These results can be used for future studies. Acknowledgements The work was sponsored by the National Science Council, Taiwan, ROC, under the grant NSC 99-2221-E-007042-MY3 and NSC 102-2221-E-007-030-MY3. The support is greatly acknowledged. References [1] [2] [3] [4] [5] [6] [7] [8]
R.F. Gibson, Principles of Composite Material Mechanics, McGraw-Hill, New York, U. S., 1997. H.M. Cheng, Carbon Nanotubes, Wu-Nan Book Inc., Taipei, Taiwan, 2004. M.F. Yu, O. Lourie, M.J. Dyer, K. Moloni, T.F. Kelly, R.S. Ruoff, Strength and breaking mechanism of multiwalled carbon nanotubes under tensile load, Science 287 (2000) 637–640. A. Allaoui, S. Bai, H.M. Cheng, J.B. Bai, Mechanical and electrical properties of a MWNT/epoxy composite, Composites Science and Technology 62 (2002) 1993–1998. H. Rajoria, N. Jalili, Passive vibration damping enhancement using carbon nanotube-epoxy reinforced composites, Composites Science and Technology 65 (2005) 2079–2093. ASTM E756-05, Standard Test Method for Measuring Vibration-Damping Properties of Materials, Annual Book of ASTM Standards 8.1.,2010. ANSYS Release 12.1, ANSYS, Inc., PA, 2009. F.H. Gojny, J. Nastalczyk, Z. Roslaniec, K. Schulte, Surface modified multi-walled carbon nanotubes in CNT/epoxy-composites, Chemical Physics Letters 370 (2003) 820–824.