- Email: [email protected]
Enhanced property analysis of MWCNT epoxy composite
Available online at www.sciencedirect.com
ScienceDirect Materials Today: Proceedings 5 (2018) 27965–27973
www.materialstoday.com/proceedings
ICCMMEMS_2018
Enhanced property analysis of MWCNT epoxy composite Surender Kumara*, Munish Kumarb a*,b
Department of Mechanical Engineering, National Institute of Technology, Jalandhar (PB), India
Abstract Epoxy use in strengthening systems was modified by dispersing MWCNTs. This MWCNTs epoxy composite was fabricated using the solvent-assisted dispersion method and ultrasonic mixing. DMA was conducted to study the effect of MWCNTs dispersion on the mechanical properties of the epoxy composite. Experimental outcomes observed a significant enhancement in the decomposition tensile properties of epoxy composite material, while, glass transition temperature (Tg) was slightly reduced due to the solvent effect. It was proved that using solvent improves the MWCNTs dispersion. Thus, at contents higher than 0.2 wt. %, MWCNTs started to re-bundle in the epoxy matrix which negatively affected the ultimate properties of epoxy composite. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Composite Materials: Manufacturing, Experimental Techniques, Modeling and Simulation (ICCMMEMS-2018). Keywords:Epoxy resin; Glass transition temperature; MWCNTs, Solvent; Dynamic mechanical analysis (DMA)
1. Introduction The properties of epoxy resin enhance by using Multi walled carbon nano tubes (MWCNTs) is a common practice. MWCNTs are excellent nano filler in epoxy resin for improved strength, electrical, thermal conductivity, stiffness and thermal stability [1]. Enhanced properties of the epoxy resin are possible only when MWCNTs disperses homogenously. In this study, MWCNTs were infused in epoxy resin using solvent-assisted dispersion method employing the ultrasonic mixing. This technique was efficiently used to disperse MWCNT’s in epoxy resin [2]. In this technique moderates the vibrational energy to rupture the MWCNT’s which results in reduction of the
* Corresponding author. Tel.: +91-8929579100. E-mail address: [email protected] 2214-7853© 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Composite Materials: Manufacturing, Experimental Techniques, Modeling and Simulation (ICCMMEMS-2018).
27966
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
Nomenclature σ ɛ E Eʺ E ί δ G
stress strain elastic modulus or storage modulus elastic modulus or storage modulus elastic modulus or storage modulus interphase logarithmic decrement shear modulus of rigidity
effective tube length. Many researchers have reported improvement in the MWCNTs dispersion in the epoxy resin by means of the solvent-assisted dispersion method. Acetone was picked up as a solvent in this research to advance the MWCNTs dispersion due to its relatively high polarity and its low boiling point compared to dimethyl formamide. The additional purpose of using acetone for MWCNTs epoxy composite fabrication was to dilute the epoxy resin to diminish the viscosity of the MWCNTs epoxy solution, since the epoxy resin used in this study was extremely viscous. The effect of solvent assisted dispersion of MWCNTs on the properties of epoxy resin was investigated by conducting thermal and mechanical experiments. The nanotubes dispersion status in the polymer matrix was interpreted by SEM test and the effect of the polymer homogeneity on the thermo-mechanical properties of the resulted epoxy nanocomposites was discussed [3-5]. The objective of this research is to improve fundamental understanding of how MWCNTs with solvent affect the curing process, morphology, mechanical, and thermal properties of epoxy based nanocomposites. 2. Past work based on epoxy composite The past efforts by the community of scientists, voluntary organizations and academics for enhancing property of MWCNT epoxy composite are shown in table 1. Table 1. Overview of past work based on epoxy composite. Author
Sample
Elastic modulus [GPa]
Strength [GPa]
Strain [%]
Toughness
S. Ruan et al. [4] (2006)
UHMWPE + 5 wt % MWNT UHMWPE + 5 wt % MWNT
2.62 ± 0.32
0.13 ± 0.004
540.4 ±104.7
593.2 ± 114.5 MPa
136.8 ± 3.8
4.17 ± 0.04
4.65 ± 0.35
110.6 ± 10.5 MPa
H.G. Chae et al. [5] (2006)
PAN + 0.5 wt % SWNT
25.5 ± 0.8
1.06 ± 0.14
7.2 ± 0.6
41 ± 8 MPa
H.G. Chae et al. [6] (2007)
Carbonized PAN + 1 wt % SWNT
450 ± 49
3.2 ± 0.4
0.72 ± 0.05
−
Z. Wang et al. [7] (2007)
PVA + 1 wt % SWNT
~17.5
~1.2
~17.5
−
J.M. Razal et al. [8](2007)
PVA + >60 wt % SWNT
78
1.8
~40
120 ± 152 J·g − 1
M.L. Minus et al. [9](2009)
PVA + 1 wt % SWNT
60 ± 6
1.4 ± 0.1
4.9 ± 0.5
29 ± 6 J·g −1
K. Young et al. [10](2010)
PVA + 2–31 wt % SWNT
244
2.9
~3–10
−
A. Montazeri et al. [11] (2010)
LY 564 epoxy + 3 wt% MWCNT
4.2
0.07
−
−
S.S. Wicks et al.
Epoxy, Resin 105 and + 2 wt %
2.7
0.248
−
3.74 KJ/m²
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27967
[12] (2010)
aligned MWCNT
D.C. Davis et al. [13] (2011)
Epoxy resin + 0.5% functionalized CNT
74
0.747
−
−
T. H. Hsieh et al. [14] (2011)
Epoxy resin (LY- 556) + 0.5 wt % MWCNT
3.26
-
−
133 J/m²
Y. Li et al. [15](2012)
Epoxy resin JER 806 + 2% MWCNT
2.85
0.048
_
0.65
J. Meng et al. [16](2013)
PVA + 10 wt % SWNT
36.3 ± 1.3
2.5 ± 0.1
10.7 ± 0.7
101.4 ± 11.4 J·g −1
Y. Shimamura. et al. [17] (2014)
Epoxy resin + As spun yarn MWCNT
30
0.2
−
−
T. Tsuda et al. [18] (2014)
Epoxy resin + 4.5
Vf CNT
18.8
0.097
−
−
Epoxy resin + 10.5 Vf CNT
27.8
0.153
−
−
Epoxy resin + 21.4 Vf CNT
50.1
0.181
−
−
Epoxy resin + 29.6 Vf CNT
73.4
0.193
−
−
Epoxy resin + 32.8 Vf CNT
89.8
0.217
−
−
Epoxy resin + 42.3 Vf CNT
82.9
0.319
−
−
Epoxy resin + 15.3 Vf CNT
42.9
0.230
−
−
M. Mecklenburg et al. [19] (2015)
Epoxy + Alignment of CNTs
3
0.075
−
−
B. Voit et al. [20] (2015)
LLDPE + NC 7000 + 2 wt % MWCNT
0.239
0.0135
−
−
LLDPE + NC 7000 + PEG + 2 wt % MWCNT
0.177
0.0124
−
−
LLDPE + NC 7000 + PEGNH 2 + 2 wt % MWCNT
0.204
0.0113
−
−
LLDPE + NC 7000 + PEGCOOH + 2 wt % MWCNT
0.206
0.0126
−
−
0.224
0.0118
−
−
21.80
0.26993
−
−
Epoxy resin + 0.3 wt % MWCNT at70°C
24.68
0.33056
−
−
Epoxy resin + 0.5 wt % MWCNT at 70°C
24.69
0.30983
−
−
1.03
0.058
−
−
Epoxy resin; LY 556 + 0.6 wt % MWCNT
1.06
0.060
Epoxy resin; LY 556 + 1.0 wt % MWCNT
1.0
0.055
2.3
.048
−
−
2.32
0.049
2.52
0.050
LLDPE + NC 7000 + PEGDE + 2 wt % MWCNT D. K. Rathore et al. [21] (2016)
S. Gantayat et al. [22] (2017)
D. He et al. [23](2017)
Epoxy resin + 0.1 wt % MWCNT at 70°C
Epoxy resin; LY 556 + 0.4 wt % MWCNT
Epoxy resin S1080 + 0.02 wt% CNTs-Al2O3 Epoxy resin S1080 + 0.05 wt% CNTs-Al2O3 Epoxy resin S1080 + 0.1 wt%
KJ/m²
27968
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973 CNTs-Al2O3
D. Hu et al. [24](2017)
M.R. Zakaria et al. [25] (2017)
(CNT) + Polyimide Concentrated sol. 0 %
25
0.4
−
−
(CNT) + Polyimide Concentrated sol. 2 %
85
2.0
−
−
(CNT) + Polyimide Concentrated sol. 4 %
85
1.5
−
−
(CNT) + Polyimide Concentrated sol. 6 %
85
1.4
−
−
Epoxy + 0.5 wt % MWCNT
1.68
0.05025
−
−
Epoxy + 1.0 wt % MWCNT
1.87
0.05865
−
−
Epoxy + 3.0 wt % MWCNT
1.69
0.05448
−
−
3. Material and experimental method The epoxy resin used in this study is the commercially available Araldite-standard (Huntsman, Bangalore, India) which is a type of Bisphenol-A. Araldite-standard is the mostly used resin in construction applications. The Araldite-standard resin used for the experiments had a glass transition temperature (Tg) of ~ 40 oC, a tensile strength of 17 MPa, and an elastic modulus of around 1.13 GPa, with the industry recommended mixing ratio of 100:80. The multi-walled carbon nanotubes were purchased from United Nanotech Innovations Pvt. Ltd. Bangalore, India. MWCNTs had a diameter range of 5-20 nm, length range of 10 µm, and specific surface area of 330 (m2/g). MWCNTs had >98% purity containing ash content of >0.2 wt. %, an amorphous carbon content of >2 wt. %. High purity acetone and ethanol were from Laboratory Reagents and Fine Chemicals (Deejay Chemicals, Jalandhar, India). Ethanol was used for carbon nanotubes treatment before nanocomposite fabrication. The as-received MWCNTs were left in a high purity (99%) ethanol solution (1:10 concentration) for 2 days in a vacuum chamber to remove the amorphous carbon and de-agglomeration of the tubes. After the adequate curing, nanotubes were dried in a vacuum oven for an hour at 100 oC and then were cooled down to the ambient temperature in a desiccator to be used for the nanocomposite fabrication. MWCNTs epoxy composites were prepared by dispersing specified weight percentage of treated MWCNTs (0.1%, 0.2% & 0.3%) in acetone and sonicating (Digital Ultrasonic Cleaner, Labgear International Ambala, India) for 1 hour (33 KHz) to get a homogeneous suspension. The next step was the addition of epoxy resin to the mixture and sonicating for another 1 hour. Sonication was performed in 40s out of every 60s to prevent increasing the mixture temperature over the limit. Further, the mixing beaker was submerged in a mixture of ice and water to avoid rise in temperature during sonication and keep it below 40 oC. After homogeneously mixing MWCNTs suspension with the resin, mixture was heated on a hot plate for 1h at 80 oC to evaporate the solvent followed by degassing in a vacuum oven for at least 6h. After cooling down the mixture to the room temperature in a desiccator, hardener was added by hand-mixing. The optimum mixing ratio of (resin: hardener) for Araldite-standard, to get the maximum degree of curing, is 100:80 recommended by factory. Reference nanocomposites were also prepared without using solvent. The treated MWCNTs were dispersed directly into the curing agent, since the curing agent had a much lesser viscosity than the resin. Later the mixing was complete, MWCNTs epoxy mixture was poured into a silicon mould, designed according to the ASTM standard D3039, and were placed on a vibrating table for 10 min. to settle in the mould properly. Sample was cured in mould at 40 oC in oven for 3 hours. Lately samples were cooled down at ambient temperature [10-18]. 4. MWCNTs epoxy composite characterization Dynamic mechanical properties were measured using a DMA 2000B, Triton Technology Ltd. UK. The fabricated samples were cut in to the dimensions of 50 mm × 5 mm × 2 mm to fit inside the DMA machine as shown in figure 1. DMA temperature was set at 120 oC with heating ramp rate was 5 oC/min. The sample was tested in three point
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27969
Fig. 1 DMA machine with MWCNTs epoxy samples (a) epoxy without MWCNTs (b, c & d) epoxy with 0.1, 0.2 & 0.3 wt. % MWCNTs respectively
bending with frequency 1 Hz and strain 0.05%. Three replications were done for each sample. Loss modulus (Eʺ), storage modulus (Eʹ), and tan δ (Eʺ/ Eʹ) were obtained from DMA analysis. Tg obtained from the peak point of tan δ. Dynamic stress σ and strain ԑ σ = σo sin (ωt + δ) ԑ = ԑo sin (ωt) The stress is divided into an in-phase component (σo cos δ) and an out of phase component (σo sin δ) σ = σo sin (ωt) cos δ + σo cos (ωt) + sin δ Eʹ and Eʺ for the in-phase (real) and out of phase (imaginary) for moduli yield σ = ԑo Eʹ sin (ωt) + ԑo Eʺ cos (ωt)
ԑ = ԑo exp (iωt)
σ = σo exp (ωt + δ)і ʹ
ʺ
The above equation shows that the complex modulus obtained from a DMA test consist of real and imaginary parts. Real or storage part defines the ability of the material to store potential energy and release it upon deformation. Imaginary or loss percentage is associated with energy dissipation in the form of heat upon deformation. G* = Gʹ + іGʺ Where Gʹ is storage modulus and Gʺ is loss modulus. ʺ
Phase angle
ʹ
Storage modulus is associated with stiffness of a material and is also related to Young modulus (E) [19- 23].
27970
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
5. Results and discussion In figure 2 shows the SEM test image of the MWCNTs epoxy composite. A poor spreading of MWCNTs in epoxy matrix was identified due to bundling. Due to the Vander Waals forces among the MWCNTs tend to generate agglomeration in the polymer matrix [24]. The other reason for the non-homogeneous dispersion of MWCNTs could be the really high viscosity of epoxy resin which partial the movement of the tubes and prevented the suitable circulation of them throughout the network. SEM test images of the MWCNTs obtained with solvent are shown in figure 2 (b & c). In this figure 2 (a), relatively uniform distribution of MWCNTs 0.2 wt. % was attained as a result of using solvent. Dispersing MWCNTs into the solvent assisted the de-bundling of MWCNTs which led to a more homogeneous dispersion. Besides, adding solvent considerably dropped the viscosity of the system which resulted in the more homogeneous distribution of MWCNTs in the epoxy resin. It shows in figure 2 (b & c) MWCNTs dispersion statuses in the epoxy systems, at a higher level of magnification. In this figure 2 (c), at the contents higher than 0.2 wt. %, MWCNTs started tore-bundle, even in case of using solvent. MWCNTs agglomerations will negatively affect the mechanical properties of the polymer by creating empty spaces in the epoxy matrix and reducing the density and rigidity of epoxy [29]. MWCNTs combinations also deteriorate the glass transition performance of epoxy by giving growth to the thermal motions in epoxy matrix [1].
Fig.2SEM tests for fracture surface of MWCNTs epoxy composite (a) Sample 1 mix. 0.2 wt. % (Mag. 10,000X) (b, c) Sample 2 & 3 based on solvent (Mag. 12,000X) respectively
5.1. Dynamic mechanical analysis (DMA) Test The DMA experimental outcomes of the MWCNTs epoxy composites are shown in figure 3 (a). The glass transition temperature (Tg) is evaluated from the ultimate position of tan δ. DMA results for samples shown figure 3. Even though MWCNTs 0.1 wt. % is mixed with epoxy resin but it did not change Tg. While, adding 0.2 wt. % of MWCNTs caused a minor increase the Tg. It was occurred due to the existence of MWCNTs in the epoxy based system. MWCNTs were involved to the matrix molecular chains and limited their motions, which subsequently, enlarged the Tg of the composite. On other end mixing of 0.3 wt. % of MWCNTs were caused a drop in Tg. It further proves the fact that with the MWCNTs contents higher than 0.2 wt. %, it will agglomerate in the epoxy network. The MWCNTs agglomeration creates a large number of vacant spaces between the matrix molecules and lead to an increase in the segmental motions in the polymer network, which accordingly, lowers for Tg [23]. Aggregate the MWCNTs content will increase the number of agglomerations and thus the vacant spaces in the polymer network, which results in a minor Tg values. The other probable motive for Tg reduction is the fact that MWCNTs bundles attract as numerous epoxy functional groups as they can in their local vicinity and prevent them from reacting with the amine groups of the hardener during the cure process. This is notorious as non-stoichiometric balance between the epoxide rings of the resin and hardener amine groups, which could prime to an un-complete Tg [30]. DMA test for MWCNTs epoxy composites solvent represent in figure 3 (b). Mixing 0.1 wt. % and 0.2 wt. %
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27971
MWCNTs to sample 1 composite was caused a moderate reduction in the Tg of epoxy composite. This performance could be explained with the solvent effect. MWCNTs into the epoxy matrix and constrained the segmental motions which led to a rise in the Tg. Thus, the residual amount of the solvent residues in the network, even long evaporation method. The enduring solvent in the network acts as dirtiness gives rise to the thermal motions of the molecular segments of the polymer and results in the decrease Tg [31]. In the figure 3 (b) mixing 0.3 wt. % of MWCNTs were
(a)
(b)
Fig. 3 DMA test for (a) MWCNTs with epoxy (b) MWCNTs epoxy composite with solvent
(a)
(b)
Fig. 4 Tensile test for (a) MWCNTs epoxy composite (b) MWCNTs epoxy composite with solvent
27972
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
dropped the Tg ~ 23 oC, compared to epoxy (without MWCNTs). The vast drop could be clarified by the agglomeration of MWCNTs and residual solvent in the network, both of which negatively effect on Tg behaviour of epoxy resin by rising the thermal motions in the composite matrix. 5.1.1. Tensile Test The stress-strain curves of the MWCNTs epoxy composite are analyzed in figure 4 (a, b). The tensile strength of epoxy composites was enriched by MWCNTs dispersion. When MWCNTs are dispersed in epoxy matrix, they attract molecular segments with their high active surface area and create a large number of MWCNTs epoxy composite films which act as reinforcements [12]. Beside, MWCNTs prevent the crack propagation through epoxy network and increase the tensile strength of epoxy composite. Figure 4 (a, b) indicates the stress in MWCNTs epoxy composites. The tensile strength was enhanced from 27.6 MPa for epoxy (without MWCNTs) to 31.7 MPa for MWCNTs epoxy composite adding 0.2 wt. % of MWCNTs. While, by mixing 0.3 wt. % of MWCNTs, the composite strength was dropped to 26.4 MPa. It was due to the aggregation of MWCNTs which eased the crack propagation in test sample. In addition probable intention is the stress concentration in the agglomeration areas which initiates crack in the test sample. Figure 4 (b) showed that solvent assist dispersion of MWCNTs enlarged the tensile properties of the epoxy sample. Mixing 0.3 wt. % of MWCNTs increased the tensile strength of epoxy composite by ~28%. This was due to uniform dispersion of MWCNTs, compared to MWCNTs epoxy composite. 6. Conclusion Epoxy composite was revised by infusing MWCNT, with and without using solvent it was demonstrated that using solvent improves the morphology of the MWCNTs epoxy system by uniformly dispersing the MWCNTs into the epoxy matrix. This controlled to a substantial improvement in mechanical properties of the epoxy composite. Mixing 0.2 wt. % MWCNTs to the epoxy resin using solvent assisted dispersion method improved the tensile strength by 28 %. Thermal decomposition temperature was also enhanced due to the reinforcing role of MWCNTs in epoxy matrix. Though, Tg was either reduced or remained unchanged. While dispersing 0.2 wt. % of MWCNTs without using solvent enlarged the Tg of epoxy due to the presence of MWCNTs in the system. Two mechanisms were competing to affect the Tg (a) the residual solvent in the system acting as dirtiness and giving rise the thermal motions in the matrix and (b) MWCNTs limiting the segmental motions in the matrix by strongly attaching to the molecular chains of epoxy. Improving the thermal properties as well as maintaining the achieved enrichments in the mechanical properties for future work. References [1]. M. Tarfaoui, K. Lafdi, A. E. Moumen, Mechanical properties of carbon nanotubes based polymer composites, Composite Part B,103, 113– 121, 2016. [2]. X. Cao, X. Wei, G. Li, C. Hu, K. Dai, J. Guo, G. Zheng, C. Liu, C. Shen, Z. Guo, Strain sensing behaviours of epoxy nanocomposites with carbon nanotubes under cyclic deformation, Polymer,112, 1–9, 2017. [3]. F. Collins, J. Lambert, W. Duan, The influences of admixtures on the dispersion, workability, and strength of carbon nanotube-OPC paste mixtures, Cem. Concr. Compos. 34, 201–207, 2012. [4]. S. Ruan, P. Gao, T.X. Yu, Ultra-strong gel-spun UHMWPE fibers reinforced using multi-walled carbon nanotubes, Polymer, 47, 1604– 1611, 2006. [5]. H.G. Chae, M.L. Minus, S. Kumar, Oriented and exfoliated single wall carbon nanotubes in polyacrylonitrile, Polymer, 47, 3494–3504, 2006. [6]. H.G. Chae, M.L. Minus, A. Rasheed, S. Kumar, Stabilization and carbonization of gel spun polyacrylonitrile/single wall carbon nanotube composite fibers,Polymer, 48, 3781–3789, 2007. [7]. Z. Wang, P. Ciselli, T. Peijs, The extraordinary reinforcing efficiency of single-walled carbonnanotubes in oriented poly (vinyl alcohol) tapes,Nat. Nanotechnol, 18, 1-9, 2007. [8]. J.M. Razal, J.N. Coleman, E. Munoz, B. Lund, Y. Gogotsi, H.Ye, S. Collins, A.B. Dalton, R.H. Baughman, Arbitrarily shaped fiber assemblies from spun carbon nanotube gel fibers, Adv .Funct. Mater, 17, 2918–2924, 2007. [9]. H.G. Chae, M.L. Minus, S. Kumar, Interfacial crystallization in gel-spun poly (vinyl alcohol)/single-wall carbon nanotube composite fibers, Macromol. Chem. Phys, 210, 1799–1808, 2009.
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27973
[10]. K.Young, F.M. Blighe, J.J. Vilatela, A.H. Windle, I.A. Kinloch, L.B. Deng, R.J. Young, J.N. Coleman, Strong dependence of mechanical pro perties on fiber diameter for polymer-nanotube composite fibers: Differentiating defect from orientation effects, ACS Nano, 4, 6989– 6997, 2010. [11]. A. Montazeri, J. Javadpour, A. Khavandi, A. Tcharkhtchi, A. Mohajeri, Mechanical properties of multi-walled carbon nanotube/epoxy composites, Mater. Des, 31, 4202–4208, 2010. [12]. S.S. Wicks, R. G. Villoria, B. L. Wardle, Interlaminar and intralaminar reinforcement of composite laminates with aligned carbon nanotubes,Compos. Sci. Technol., 70, 20–28, 2010. [13]. D. C. Davis, J. W. Wilkerson, J. Zhu, V. G. Hadjiev, A strategy for improving mechanical properties of a fiber reinforced epoxy composite using functionalized carbon nanotubes, Compos. Sci. Technol., 71, 1089–1097, 2011. [14]. T. H. Hsieh, a. J. Kinloch, A. C. Taylor, I. A. Kinloch, The effect of carbon nanotubes on the fracture toughness and fatigue performance of a thermosetting epoxy polymer, J. Mater. Sci., 46, 7525–7535, 2011. [15]. Y. Li, N.Hu, T. Kojima, T. Itoi, T. Watanabe, T. Nakamura, N. Takizawa, H. Fukunaga, experimental study on mechanical properties of epoxy/mwcnt nanocomposites—effects of acid treatment, pressured curing, and liquid rubber, J. Nanotechnol. Eng. Med., 3, 011004, 2012. [16]. J. Meng, Y. Zhang, K. Song, M.L. Minus, Forming crystalline polymer-nano interphase structures for high modulus and high tensile strength composite fibers,Macromol. Mater. Eng. Materials, 6,2566, 2013. [17]. Y. Shimamura et al., Tensile mechanical properties of carbon nanotube / epoxy composite fabricated by pultrusion of carbon nanotube spun yarn preform, Compos. PART A, 62, 32–38, 2014. [18]. T. Tsuda, T. Ogasawara, S. Moon, K. Nakamoto, N. Takeda, Three dimensional orientation angle distribution counting and calculation for the mechanical properties of aligned carbon nanotube / epoxy composites. Compos. PART A,65, 1–9, 2014. [19]. M. Mecklenburget al., On the manufacturing and electrical and mechanical properties of ultra-high wt.% fraction aligned MWCNT and randomly oriented CNT epoxy composites, Carbon N. Y.,91, 275–290, 2015. [20]. B. Voit, M. Thomas, P. Petra, Dispersion of carbon nanotubes into polyethylene by an additive assisted one-step melt mixing approach,66, 210–221, 2015. [21]. D. K. Rathore, R. K. Prusty, D. S. Kumar, B. C. Ray, Mechanical performance of CNT-filled glass fiber / epoxy composite in in-situ elevated temperature environments emphasizing the role of CNT content, Compos. PART A,84, 364–376, 2016. [22]. S. Gantayat, D. Rout, S. K. Swain, Mechanical properties of functionalized multi-walled carbon nanotube / epoxy nanocomposites. Mater. Today Proc., 4, 4061–4064, 2017. [23]. D. He et al., Multifunctional polymer composites reinforced by carbon nanotubes – Alumina hybrids with urchin-like structure, Mater. Today Commun, 11, 94–102, 2017. [24]. D. Hu et al., Ultrastrong and excellent dynamic mechanical properties of carbon nanotube composites,Compos. Sci. Technol., 141, 137– 144, 2017. [25]. M.R. Zakaria, M. Helmi, A. Kudus, H. Akil, Comparative study of graphene nanoparticle and multiwall carbon nanotube filled epoxy nanocomposites based on mechanical, thermal and dielectric properties, Compos. Part B, 119, 57–66, 2017.
ScienceDirect Materials Today: Proceedings 5 (2018) 27965–27973
www.materialstoday.com/proceedings
ICCMMEMS_2018
Enhanced property analysis of MWCNT epoxy composite Surender Kumara*, Munish Kumarb a*,b
Department of Mechanical Engineering, National Institute of Technology, Jalandhar (PB), India
Abstract Epoxy use in strengthening systems was modified by dispersing MWCNTs. This MWCNTs epoxy composite was fabricated using the solvent-assisted dispersion method and ultrasonic mixing. DMA was conducted to study the effect of MWCNTs dispersion on the mechanical properties of the epoxy composite. Experimental outcomes observed a significant enhancement in the decomposition tensile properties of epoxy composite material, while, glass transition temperature (Tg) was slightly reduced due to the solvent effect. It was proved that using solvent improves the MWCNTs dispersion. Thus, at contents higher than 0.2 wt. %, MWCNTs started to re-bundle in the epoxy matrix which negatively affected the ultimate properties of epoxy composite. © 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Composite Materials: Manufacturing, Experimental Techniques, Modeling and Simulation (ICCMMEMS-2018). Keywords:Epoxy resin; Glass transition temperature; MWCNTs, Solvent; Dynamic mechanical analysis (DMA)
1. Introduction The properties of epoxy resin enhance by using Multi walled carbon nano tubes (MWCNTs) is a common practice. MWCNTs are excellent nano filler in epoxy resin for improved strength, electrical, thermal conductivity, stiffness and thermal stability [1]. Enhanced properties of the epoxy resin are possible only when MWCNTs disperses homogenously. In this study, MWCNTs were infused in epoxy resin using solvent-assisted dispersion method employing the ultrasonic mixing. This technique was efficiently used to disperse MWCNT’s in epoxy resin [2]. In this technique moderates the vibrational energy to rupture the MWCNT’s which results in reduction of the
* Corresponding author. Tel.: +91-8929579100. E-mail address: [email protected] 2214-7853© 2018 Elsevier Ltd. All rights reserved. Selection and Peer-review under responsibility of International Conference on Composite Materials: Manufacturing, Experimental Techniques, Modeling and Simulation (ICCMMEMS-2018).
27966
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
Nomenclature σ ɛ E Eʺ E ί δ G
stress strain elastic modulus or storage modulus elastic modulus or storage modulus elastic modulus or storage modulus interphase logarithmic decrement shear modulus of rigidity
effective tube length. Many researchers have reported improvement in the MWCNTs dispersion in the epoxy resin by means of the solvent-assisted dispersion method. Acetone was picked up as a solvent in this research to advance the MWCNTs dispersion due to its relatively high polarity and its low boiling point compared to dimethyl formamide. The additional purpose of using acetone for MWCNTs epoxy composite fabrication was to dilute the epoxy resin to diminish the viscosity of the MWCNTs epoxy solution, since the epoxy resin used in this study was extremely viscous. The effect of solvent assisted dispersion of MWCNTs on the properties of epoxy resin was investigated by conducting thermal and mechanical experiments. The nanotubes dispersion status in the polymer matrix was interpreted by SEM test and the effect of the polymer homogeneity on the thermo-mechanical properties of the resulted epoxy nanocomposites was discussed [3-5]. The objective of this research is to improve fundamental understanding of how MWCNTs with solvent affect the curing process, morphology, mechanical, and thermal properties of epoxy based nanocomposites. 2. Past work based on epoxy composite The past efforts by the community of scientists, voluntary organizations and academics for enhancing property of MWCNT epoxy composite are shown in table 1. Table 1. Overview of past work based on epoxy composite. Author
Sample
Elastic modulus [GPa]
Strength [GPa]
Strain [%]
Toughness
S. Ruan et al. [4] (2006)
UHMWPE + 5 wt % MWNT UHMWPE + 5 wt % MWNT
2.62 ± 0.32
0.13 ± 0.004
540.4 ±104.7
593.2 ± 114.5 MPa
136.8 ± 3.8
4.17 ± 0.04
4.65 ± 0.35
110.6 ± 10.5 MPa
H.G. Chae et al. [5] (2006)
PAN + 0.5 wt % SWNT
25.5 ± 0.8
1.06 ± 0.14
7.2 ± 0.6
41 ± 8 MPa
H.G. Chae et al. [6] (2007)
Carbonized PAN + 1 wt % SWNT
450 ± 49
3.2 ± 0.4
0.72 ± 0.05
−
Z. Wang et al. [7] (2007)
PVA + 1 wt % SWNT
~17.5
~1.2
~17.5
−
J.M. Razal et al. [8](2007)
PVA + >60 wt % SWNT
78
1.8
~40
120 ± 152 J·g − 1
M.L. Minus et al. [9](2009)
PVA + 1 wt % SWNT
60 ± 6
1.4 ± 0.1
4.9 ± 0.5
29 ± 6 J·g −1
K. Young et al. [10](2010)
PVA + 2–31 wt % SWNT
244
2.9
~3–10
−
A. Montazeri et al. [11] (2010)
LY 564 epoxy + 3 wt% MWCNT
4.2
0.07
−
−
S.S. Wicks et al.
Epoxy, Resin 105 and + 2 wt %
2.7
0.248
−
3.74 KJ/m²
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27967
[12] (2010)
aligned MWCNT
D.C. Davis et al. [13] (2011)
Epoxy resin + 0.5% functionalized CNT
74
0.747
−
−
T. H. Hsieh et al. [14] (2011)
Epoxy resin (LY- 556) + 0.5 wt % MWCNT
3.26
-
−
133 J/m²
Y. Li et al. [15](2012)
Epoxy resin JER 806 + 2% MWCNT
2.85
0.048
_
0.65
J. Meng et al. [16](2013)
PVA + 10 wt % SWNT
36.3 ± 1.3
2.5 ± 0.1
10.7 ± 0.7
101.4 ± 11.4 J·g −1
Y. Shimamura. et al. [17] (2014)
Epoxy resin + As spun yarn MWCNT
30
0.2
−
−
T. Tsuda et al. [18] (2014)
Epoxy resin + 4.5
Vf CNT
18.8
0.097
−
−
Epoxy resin + 10.5 Vf CNT
27.8
0.153
−
−
Epoxy resin + 21.4 Vf CNT
50.1
0.181
−
−
Epoxy resin + 29.6 Vf CNT
73.4
0.193
−
−
Epoxy resin + 32.8 Vf CNT
89.8
0.217
−
−
Epoxy resin + 42.3 Vf CNT
82.9
0.319
−
−
Epoxy resin + 15.3 Vf CNT
42.9
0.230
−
−
M. Mecklenburg et al. [19] (2015)
Epoxy + Alignment of CNTs
3
0.075
−
−
B. Voit et al. [20] (2015)
LLDPE + NC 7000 + 2 wt % MWCNT
0.239
0.0135
−
−
LLDPE + NC 7000 + PEG + 2 wt % MWCNT
0.177
0.0124
−
−
LLDPE + NC 7000 + PEGNH 2 + 2 wt % MWCNT
0.204
0.0113
−
−
LLDPE + NC 7000 + PEGCOOH + 2 wt % MWCNT
0.206
0.0126
−
−
0.224
0.0118
−
−
21.80
0.26993
−
−
Epoxy resin + 0.3 wt % MWCNT at70°C
24.68
0.33056
−
−
Epoxy resin + 0.5 wt % MWCNT at 70°C
24.69
0.30983
−
−
1.03
0.058
−
−
Epoxy resin; LY 556 + 0.6 wt % MWCNT
1.06
0.060
Epoxy resin; LY 556 + 1.0 wt % MWCNT
1.0
0.055
2.3
.048
−
−
2.32
0.049
2.52
0.050
LLDPE + NC 7000 + PEGDE + 2 wt % MWCNT D. K. Rathore et al. [21] (2016)
S. Gantayat et al. [22] (2017)
D. He et al. [23](2017)
Epoxy resin + 0.1 wt % MWCNT at 70°C
Epoxy resin; LY 556 + 0.4 wt % MWCNT
Epoxy resin S1080 + 0.02 wt% CNTs-Al2O3 Epoxy resin S1080 + 0.05 wt% CNTs-Al2O3 Epoxy resin S1080 + 0.1 wt%
KJ/m²
27968
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973 CNTs-Al2O3
D. Hu et al. [24](2017)
M.R. Zakaria et al. [25] (2017)
(CNT) + Polyimide Concentrated sol. 0 %
25
0.4
−
−
(CNT) + Polyimide Concentrated sol. 2 %
85
2.0
−
−
(CNT) + Polyimide Concentrated sol. 4 %
85
1.5
−
−
(CNT) + Polyimide Concentrated sol. 6 %
85
1.4
−
−
Epoxy + 0.5 wt % MWCNT
1.68
0.05025
−
−
Epoxy + 1.0 wt % MWCNT
1.87
0.05865
−
−
Epoxy + 3.0 wt % MWCNT
1.69
0.05448
−
−
3. Material and experimental method The epoxy resin used in this study is the commercially available Araldite-standard (Huntsman, Bangalore, India) which is a type of Bisphenol-A. Araldite-standard is the mostly used resin in construction applications. The Araldite-standard resin used for the experiments had a glass transition temperature (Tg) of ~ 40 oC, a tensile strength of 17 MPa, and an elastic modulus of around 1.13 GPa, with the industry recommended mixing ratio of 100:80. The multi-walled carbon nanotubes were purchased from United Nanotech Innovations Pvt. Ltd. Bangalore, India. MWCNTs had a diameter range of 5-20 nm, length range of 10 µm, and specific surface area of 330 (m2/g). MWCNTs had >98% purity containing ash content of >0.2 wt. %, an amorphous carbon content of >2 wt. %. High purity acetone and ethanol were from Laboratory Reagents and Fine Chemicals (Deejay Chemicals, Jalandhar, India). Ethanol was used for carbon nanotubes treatment before nanocomposite fabrication. The as-received MWCNTs were left in a high purity (99%) ethanol solution (1:10 concentration) for 2 days in a vacuum chamber to remove the amorphous carbon and de-agglomeration of the tubes. After the adequate curing, nanotubes were dried in a vacuum oven for an hour at 100 oC and then were cooled down to the ambient temperature in a desiccator to be used for the nanocomposite fabrication. MWCNTs epoxy composites were prepared by dispersing specified weight percentage of treated MWCNTs (0.1%, 0.2% & 0.3%) in acetone and sonicating (Digital Ultrasonic Cleaner, Labgear International Ambala, India) for 1 hour (33 KHz) to get a homogeneous suspension. The next step was the addition of epoxy resin to the mixture and sonicating for another 1 hour. Sonication was performed in 40s out of every 60s to prevent increasing the mixture temperature over the limit. Further, the mixing beaker was submerged in a mixture of ice and water to avoid rise in temperature during sonication and keep it below 40 oC. After homogeneously mixing MWCNTs suspension with the resin, mixture was heated on a hot plate for 1h at 80 oC to evaporate the solvent followed by degassing in a vacuum oven for at least 6h. After cooling down the mixture to the room temperature in a desiccator, hardener was added by hand-mixing. The optimum mixing ratio of (resin: hardener) for Araldite-standard, to get the maximum degree of curing, is 100:80 recommended by factory. Reference nanocomposites were also prepared without using solvent. The treated MWCNTs were dispersed directly into the curing agent, since the curing agent had a much lesser viscosity than the resin. Later the mixing was complete, MWCNTs epoxy mixture was poured into a silicon mould, designed according to the ASTM standard D3039, and were placed on a vibrating table for 10 min. to settle in the mould properly. Sample was cured in mould at 40 oC in oven for 3 hours. Lately samples were cooled down at ambient temperature [10-18]. 4. MWCNTs epoxy composite characterization Dynamic mechanical properties were measured using a DMA 2000B, Triton Technology Ltd. UK. The fabricated samples were cut in to the dimensions of 50 mm × 5 mm × 2 mm to fit inside the DMA machine as shown in figure 1. DMA temperature was set at 120 oC with heating ramp rate was 5 oC/min. The sample was tested in three point
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27969
Fig. 1 DMA machine with MWCNTs epoxy samples (a) epoxy without MWCNTs (b, c & d) epoxy with 0.1, 0.2 & 0.3 wt. % MWCNTs respectively
bending with frequency 1 Hz and strain 0.05%. Three replications were done for each sample. Loss modulus (Eʺ), storage modulus (Eʹ), and tan δ (Eʺ/ Eʹ) were obtained from DMA analysis. Tg obtained from the peak point of tan δ. Dynamic stress σ and strain ԑ σ = σo sin (ωt + δ) ԑ = ԑo sin (ωt) The stress is divided into an in-phase component (σo cos δ) and an out of phase component (σo sin δ) σ = σo sin (ωt) cos δ + σo cos (ωt) + sin δ Eʹ and Eʺ for the in-phase (real) and out of phase (imaginary) for moduli yield σ = ԑo Eʹ sin (ωt) + ԑo Eʺ cos (ωt)
ԑ = ԑo exp (iωt)
σ = σo exp (ωt + δ)і ʹ
ʺ
The above equation shows that the complex modulus obtained from a DMA test consist of real and imaginary parts. Real or storage part defines the ability of the material to store potential energy and release it upon deformation. Imaginary or loss percentage is associated with energy dissipation in the form of heat upon deformation. G* = Gʹ + іGʺ Where Gʹ is storage modulus and Gʺ is loss modulus. ʺ
Phase angle
ʹ
Storage modulus is associated with stiffness of a material and is also related to Young modulus (E) [19- 23].
27970
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
5. Results and discussion In figure 2 shows the SEM test image of the MWCNTs epoxy composite. A poor spreading of MWCNTs in epoxy matrix was identified due to bundling. Due to the Vander Waals forces among the MWCNTs tend to generate agglomeration in the polymer matrix [24]. The other reason for the non-homogeneous dispersion of MWCNTs could be the really high viscosity of epoxy resin which partial the movement of the tubes and prevented the suitable circulation of them throughout the network. SEM test images of the MWCNTs obtained with solvent are shown in figure 2 (b & c). In this figure 2 (a), relatively uniform distribution of MWCNTs 0.2 wt. % was attained as a result of using solvent. Dispersing MWCNTs into the solvent assisted the de-bundling of MWCNTs which led to a more homogeneous dispersion. Besides, adding solvent considerably dropped the viscosity of the system which resulted in the more homogeneous distribution of MWCNTs in the epoxy resin. It shows in figure 2 (b & c) MWCNTs dispersion statuses in the epoxy systems, at a higher level of magnification. In this figure 2 (c), at the contents higher than 0.2 wt. %, MWCNTs started tore-bundle, even in case of using solvent. MWCNTs agglomerations will negatively affect the mechanical properties of the polymer by creating empty spaces in the epoxy matrix and reducing the density and rigidity of epoxy [29]. MWCNTs combinations also deteriorate the glass transition performance of epoxy by giving growth to the thermal motions in epoxy matrix [1].
Fig.2SEM tests for fracture surface of MWCNTs epoxy composite (a) Sample 1 mix. 0.2 wt. % (Mag. 10,000X) (b, c) Sample 2 & 3 based on solvent (Mag. 12,000X) respectively
5.1. Dynamic mechanical analysis (DMA) Test The DMA experimental outcomes of the MWCNTs epoxy composites are shown in figure 3 (a). The glass transition temperature (Tg) is evaluated from the ultimate position of tan δ. DMA results for samples shown figure 3. Even though MWCNTs 0.1 wt. % is mixed with epoxy resin but it did not change Tg. While, adding 0.2 wt. % of MWCNTs caused a minor increase the Tg. It was occurred due to the existence of MWCNTs in the epoxy based system. MWCNTs were involved to the matrix molecular chains and limited their motions, which subsequently, enlarged the Tg of the composite. On other end mixing of 0.3 wt. % of MWCNTs were caused a drop in Tg. It further proves the fact that with the MWCNTs contents higher than 0.2 wt. %, it will agglomerate in the epoxy network. The MWCNTs agglomeration creates a large number of vacant spaces between the matrix molecules and lead to an increase in the segmental motions in the polymer network, which accordingly, lowers for Tg [23]. Aggregate the MWCNTs content will increase the number of agglomerations and thus the vacant spaces in the polymer network, which results in a minor Tg values. The other probable motive for Tg reduction is the fact that MWCNTs bundles attract as numerous epoxy functional groups as they can in their local vicinity and prevent them from reacting with the amine groups of the hardener during the cure process. This is notorious as non-stoichiometric balance between the epoxide rings of the resin and hardener amine groups, which could prime to an un-complete Tg [30]. DMA test for MWCNTs epoxy composites solvent represent in figure 3 (b). Mixing 0.1 wt. % and 0.2 wt. %
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27971
MWCNTs to sample 1 composite was caused a moderate reduction in the Tg of epoxy composite. This performance could be explained with the solvent effect. MWCNTs into the epoxy matrix and constrained the segmental motions which led to a rise in the Tg. Thus, the residual amount of the solvent residues in the network, even long evaporation method. The enduring solvent in the network acts as dirtiness gives rise to the thermal motions of the molecular segments of the polymer and results in the decrease Tg [31]. In the figure 3 (b) mixing 0.3 wt. % of MWCNTs were
(a)
(b)
Fig. 3 DMA test for (a) MWCNTs with epoxy (b) MWCNTs epoxy composite with solvent
(a)
(b)
Fig. 4 Tensile test for (a) MWCNTs epoxy composite (b) MWCNTs epoxy composite with solvent
27972
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
dropped the Tg ~ 23 oC, compared to epoxy (without MWCNTs). The vast drop could be clarified by the agglomeration of MWCNTs and residual solvent in the network, both of which negatively effect on Tg behaviour of epoxy resin by rising the thermal motions in the composite matrix. 5.1.1. Tensile Test The stress-strain curves of the MWCNTs epoxy composite are analyzed in figure 4 (a, b). The tensile strength of epoxy composites was enriched by MWCNTs dispersion. When MWCNTs are dispersed in epoxy matrix, they attract molecular segments with their high active surface area and create a large number of MWCNTs epoxy composite films which act as reinforcements [12]. Beside, MWCNTs prevent the crack propagation through epoxy network and increase the tensile strength of epoxy composite. Figure 4 (a, b) indicates the stress in MWCNTs epoxy composites. The tensile strength was enhanced from 27.6 MPa for epoxy (without MWCNTs) to 31.7 MPa for MWCNTs epoxy composite adding 0.2 wt. % of MWCNTs. While, by mixing 0.3 wt. % of MWCNTs, the composite strength was dropped to 26.4 MPa. It was due to the aggregation of MWCNTs which eased the crack propagation in test sample. In addition probable intention is the stress concentration in the agglomeration areas which initiates crack in the test sample. Figure 4 (b) showed that solvent assist dispersion of MWCNTs enlarged the tensile properties of the epoxy sample. Mixing 0.3 wt. % of MWCNTs increased the tensile strength of epoxy composite by ~28%. This was due to uniform dispersion of MWCNTs, compared to MWCNTs epoxy composite. 6. Conclusion Epoxy composite was revised by infusing MWCNT, with and without using solvent it was demonstrated that using solvent improves the morphology of the MWCNTs epoxy system by uniformly dispersing the MWCNTs into the epoxy matrix. This controlled to a substantial improvement in mechanical properties of the epoxy composite. Mixing 0.2 wt. % MWCNTs to the epoxy resin using solvent assisted dispersion method improved the tensile strength by 28 %. Thermal decomposition temperature was also enhanced due to the reinforcing role of MWCNTs in epoxy matrix. Though, Tg was either reduced or remained unchanged. While dispersing 0.2 wt. % of MWCNTs without using solvent enlarged the Tg of epoxy due to the presence of MWCNTs in the system. Two mechanisms were competing to affect the Tg (a) the residual solvent in the system acting as dirtiness and giving rise the thermal motions in the matrix and (b) MWCNTs limiting the segmental motions in the matrix by strongly attaching to the molecular chains of epoxy. Improving the thermal properties as well as maintaining the achieved enrichments in the mechanical properties for future work. References [1]. M. Tarfaoui, K. Lafdi, A. E. Moumen, Mechanical properties of carbon nanotubes based polymer composites, Composite Part B,103, 113– 121, 2016. [2]. X. Cao, X. Wei, G. Li, C. Hu, K. Dai, J. Guo, G. Zheng, C. Liu, C. Shen, Z. Guo, Strain sensing behaviours of epoxy nanocomposites with carbon nanotubes under cyclic deformation, Polymer,112, 1–9, 2017. [3]. F. Collins, J. Lambert, W. Duan, The influences of admixtures on the dispersion, workability, and strength of carbon nanotube-OPC paste mixtures, Cem. Concr. Compos. 34, 201–207, 2012. [4]. S. Ruan, P. Gao, T.X. Yu, Ultra-strong gel-spun UHMWPE fibers reinforced using multi-walled carbon nanotubes, Polymer, 47, 1604– 1611, 2006. [5]. H.G. Chae, M.L. Minus, S. Kumar, Oriented and exfoliated single wall carbon nanotubes in polyacrylonitrile, Polymer, 47, 3494–3504, 2006. [6]. H.G. Chae, M.L. Minus, A. Rasheed, S. Kumar, Stabilization and carbonization of gel spun polyacrylonitrile/single wall carbon nanotube composite fibers,Polymer, 48, 3781–3789, 2007. [7]. Z. Wang, P. Ciselli, T. Peijs, The extraordinary reinforcing efficiency of single-walled carbonnanotubes in oriented poly (vinyl alcohol) tapes,Nat. Nanotechnol, 18, 1-9, 2007. [8]. J.M. Razal, J.N. Coleman, E. Munoz, B. Lund, Y. Gogotsi, H.Ye, S. Collins, A.B. Dalton, R.H. Baughman, Arbitrarily shaped fiber assemblies from spun carbon nanotube gel fibers, Adv .Funct. Mater, 17, 2918–2924, 2007. [9]. H.G. Chae, M.L. Minus, S. Kumar, Interfacial crystallization in gel-spun poly (vinyl alcohol)/single-wall carbon nanotube composite fibers, Macromol. Chem. Phys, 210, 1799–1808, 2009.
S. Kumar, M.. Kumar/ Materials Today: Proceedings 5 (2018) 27965–27973
27973
[10]. K.Young, F.M. Blighe, J.J. Vilatela, A.H. Windle, I.A. Kinloch, L.B. Deng, R.J. Young, J.N. Coleman, Strong dependence of mechanical pro perties on fiber diameter for polymer-nanotube composite fibers: Differentiating defect from orientation effects, ACS Nano, 4, 6989– 6997, 2010. [11]. A. Montazeri, J. Javadpour, A. Khavandi, A. Tcharkhtchi, A. Mohajeri, Mechanical properties of multi-walled carbon nanotube/epoxy composites, Mater. Des, 31, 4202–4208, 2010. [12]. S.S. Wicks, R. G. Villoria, B. L. Wardle, Interlaminar and intralaminar reinforcement of composite laminates with aligned carbon nanotubes,Compos. Sci. Technol., 70, 20–28, 2010. [13]. D. C. Davis, J. W. Wilkerson, J. Zhu, V. G. Hadjiev, A strategy for improving mechanical properties of a fiber reinforced epoxy composite using functionalized carbon nanotubes, Compos. Sci. Technol., 71, 1089–1097, 2011. [14]. T. H. Hsieh, a. J. Kinloch, A. C. Taylor, I. A. Kinloch, The effect of carbon nanotubes on the fracture toughness and fatigue performance of a thermosetting epoxy polymer, J. Mater. Sci., 46, 7525–7535, 2011. [15]. Y. Li, N.Hu, T. Kojima, T. Itoi, T. Watanabe, T. Nakamura, N. Takizawa, H. Fukunaga, experimental study on mechanical properties of epoxy/mwcnt nanocomposites—effects of acid treatment, pressured curing, and liquid rubber, J. Nanotechnol. Eng. Med., 3, 011004, 2012. [16]. J. Meng, Y. Zhang, K. Song, M.L. Minus, Forming crystalline polymer-nano interphase structures for high modulus and high tensile strength composite fibers,Macromol. Mater. Eng. Materials, 6,2566, 2013. [17]. Y. Shimamura et al., Tensile mechanical properties of carbon nanotube / epoxy composite fabricated by pultrusion of carbon nanotube spun yarn preform, Compos. PART A, 62, 32–38, 2014. [18]. T. Tsuda, T. Ogasawara, S. Moon, K. Nakamoto, N. Takeda, Three dimensional orientation angle distribution counting and calculation for the mechanical properties of aligned carbon nanotube / epoxy composites. Compos. PART A,65, 1–9, 2014. [19]. M. Mecklenburget al., On the manufacturing and electrical and mechanical properties of ultra-high wt.% fraction aligned MWCNT and randomly oriented CNT epoxy composites, Carbon N. Y.,91, 275–290, 2015. [20]. B. Voit, M. Thomas, P. Petra, Dispersion of carbon nanotubes into polyethylene by an additive assisted one-step melt mixing approach,66, 210–221, 2015. [21]. D. K. Rathore, R. K. Prusty, D. S. Kumar, B. C. Ray, Mechanical performance of CNT-filled glass fiber / epoxy composite in in-situ elevated temperature environments emphasizing the role of CNT content, Compos. PART A,84, 364–376, 2016. [22]. S. Gantayat, D. Rout, S. K. Swain, Mechanical properties of functionalized multi-walled carbon nanotube / epoxy nanocomposites. Mater. Today Proc., 4, 4061–4064, 2017. [23]. D. He et al., Multifunctional polymer composites reinforced by carbon nanotubes – Alumina hybrids with urchin-like structure, Mater. Today Commun, 11, 94–102, 2017. [24]. D. Hu et al., Ultrastrong and excellent dynamic mechanical properties of carbon nanotube composites,Compos. Sci. Technol., 141, 137– 144, 2017. [25]. M.R. Zakaria, M. Helmi, A. Kudus, H. Akil, Comparative study of graphene nanoparticle and multiwall carbon nanotube filled epoxy nanocomposites based on mechanical, thermal and dielectric properties, Compos. Part B, 119, 57–66, 2017.