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epoxy composites
Journal Pre-proof The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Xiao-Jun Shen, Chen-Yang Dang, Bo-Lin Tang, Xiao-Hui Yang, Hui-Jie Nie, Jing-Jing Lu, Tong-Tong Zhang, Klaus Friedrich PII:
S0264-1275(19)30695-1
DOI:
https://doi.org/10.1016/j.matdes.2019.108257
Reference:
JMADE 108257
To appear in:
Materials & Design
Received Date: 5 August 2019 Revised Date:
5 October 2019
Accepted Date: 5 October 2019
Please cite this article as: X.-J. Shen, C.-Y. Dang, B.-L. Tang, X.-H. Yang, H.-J. Nie, J.-J. Lu, T.-T. Zhang, K. Friedrich, The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites, Materials & Design (2019), doi: https://doi.org/10.1016/ j.matdes.2019.108257. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
Manuscript ID: JMAD-D-19-02331
Dear Editor I would like to declare on behalf of my co-authors that the work described was original research that has not been published previously, and not under consideration for publication elsewhere, in whole or in part. All the authors listed have approved the manuscript that is enclosed.
Xiao-Jun Shen (PhD/Associate Professor/Group Leader) College of Materials and Textile Engineering, Jiaxing University Jiaxing 314001, Zhejiang Province, China Tel.: +86-573-83643022 E-mail address: [email protected]
The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Graphical abstract:
The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Xiao-Jun Shena,b*, Chen-Yang Danga,c, Bo-Lin Tanga, Xiao-Hui Yanga, Hui-Jie Niea,c, Jing-Jing Lua, Tong-Tong Zhanga, Klaus Friedrichb* a
Key Laboratory of Yarn Materials Forming and Composite Processing Technology
of Zhejiang Province, Jiaxing University, Jiaxing, 314001, China. b
Institute for Composite Materials, Technical University of Kaiserslautern,
Kaiserslautern, D-67663, Germany. c
School of Materials Science and Engineering, Changzhou University, Changzhou,
213164, China. ABSTRACT In this study, nano Fe3O4 functionalized graphene oxide (Fe3O4@GO) was employed to enhance the interlaminar shear strength (ILSS) of carbon fabric/epoxy (CF/EP) composites. The composite was fabricated via a vacuum-assisted resin transfer molding process under a magnetic field. The microstructure and reinforcement mechanism of the CF/EP composite was further investigated. The results indicate that the Fe3O4@GO can increase the ILSS of the CF/EP composite by 12.9%, and it can further enhance it to 41% under the magnetic field orientation. Furthermore, it was observed that the oriented Fe3O4@GO can also improve the flexural strength and tensile strength of the CF/EP composite by 29.7% and 40.9%, respectively. The main reason is that the oriented GO arrangement is better ordered and thus can withstand more lateral loads inside the composite. Keywords: Carbon fiber; Polymer-matrix composites (PMCs); Epoxy; Interlaminar shear strength; Magnetic oriented graphene oxide *Corresponding author: Tel: +86-573-83643022. E-mail address: [email protected] (X.-J. Shen), [email protected] (K. Friedrich).
1
1. Introduction Carbon fabric reinforced epoxy (CF/EP) composites have been widely used in many areas, including automobile, aerospace, military, marine, etc., due to their unique properties, such as high strength, lightweight and high modulus [1-4]. However, most of the CF/EP composites are laminated plate structures. The strength in the through-thickness direction is relatively low due to the fact that there are no fibers in the thickness direction. Furthermore, the low strength in the through-thickness direction generally leads to delaminations in the composites, which limits the application of CF/EP composites [1, 5, 6]. The interlaminar shear strength (ILSS) of CF/EP composites depends on the strength of EP and the interfacial adhesion between CF and EP [5, 7]. Thus to improve the ILSS of CF/EP composites, two kinds of methods can be used. On the one hand, the surface of CF should be treated. Wu et al. modified the CF surface by synergistic modification of electrochemical oxidation and sizing treatment to increase the surface activity of CF, which ultimately increased the ILSS of the composite by 158% [8]. Qi et al. reported that grafting rigid (p-phenylenediamine) and flexible structures (ethylenediamine) to the CF surface could improve the interfacial properties of composites. The rigid and flexible structures increased the ILSS of the composite by 44.8% and 38.6%, respectively [9]. On the other hand, the strength of EP can be reinforced by introducing some nanofillers such as nano SiO2, nano TiO2, carbon nanotubes and graphene and its derivatives into the EP matrix [10]. Among them, graphene oxide (GO) is regarded as the ideal nanofiller for enhancing epoxy resins
2
because of its functional groups, such as carboxyl and hydroxyl groups. The latter can react with EP to achieve good interfacial adhesion between EP and GO [11-13]. Bhanuprakash et al. reported that GO can effectively improve the interfacial properties between CF and EP, and increase the ILSS of composites by 47% [2]. However, the disordered structure of the GO is easier to agglomerate than the oriented GO, which is not conducive to fully exerting the enhancement effect of the GO in the composites. This work was inspired by the honeycomb panel model: in the honeycomb panel model, the honeycomb core material plays a major role in bearing the lateral shear force [14]. The honeycomb core layer can be simplified into a plurality of longitudinal support faces. Therefore, in this work the GO platelets were oriented as longitudinal support surfaces between the layers of the carbon fabric. In this way, the oriented GO is supposed to carry the major transverse shear force in the weakest area of the CF/EP composite material (between the CF layers) and to prevent the lateral micro cracks expanding between the composite layers. 2. Experimental Section 2.1 Basic Materials Natural graphite powders were purchased from Qingdao Jinrilai Shimo Co. Ltd, China. Carbon fabric (T300, 3K) was bought from Jiaxing Longshine Carbon Fiber Co. Ltd, China. FeCl3·6H2O and FeSO4·7H2O were obtained from Lanxi Yongli Chemical Co. Ltd, China. Concentrated sulfuric acid and hydrochloric acid were purchased from Xiaoshan Chemical Reagent Co. Ltd, China. EP (diglycidyl ether of
3
bisphenol A) resin and the curing agent (593) were obtained from Haining Hailong Chemical Co. Ltd, China. Ethanol, Sodium nitrate and potassium permanganate were purchased from Xiaoshan Chemical Reagent Co. Ltd, China, and used as received. 2.2 Preparation of Fe3O4@GO Graphene oxide (GO) was prepared according to our previous work [15]. Under a nitrogen atmosphere, FeCl3·6H2O and FeSO4·7H2O were added to deionized water (60 ml), and the resultant mixture was treated by ultrasonic technique (400 W) for 0.5 h. The ratio of Fe2+ to Fe3+ was 1:1.25 and the total amount was 0.03 mol. After that, the above mixture was added to a GO suspension (200 ml, 0.2 mg/ml) drop by drop with mechanical stirring. Then, the resultant mixture was heated up to 60
and the
pH value of the mixture was tuned to 9-10 by quickly adding ammonium hydroxide. After that, the mixture was stirred for 2 h with constant temperature. Then, the resultant mixture was washed by deionized water several times till the pH value closed to 7. 2.3 Preparation of Fe3O4@GO/carbon fabric/epoxy composites The schematic of the preparing process of CF/EP composites is displayed in Fig. 1. The as-prepared Fe3O4@GO was dispersed in ethanol to form a 0.2 mg/ml suspension. Then, the above suspension was treated by ultrasonication (400 W) for 0.5 h. After that, the epoxy resin was mixed with the Fe3O4@GO suspension. The resulting mixture was mechanically stirred for 0.5 h, and treated by ultrasonication for another 0.5 h. It was heated in an oven at 80
for 24 h to remove the ethanol. Afterwards, the
curing agent (593) was added to the mixture with a ratio of 30 to 100 (593: EP). The
4
resultant suspension was degassed with a vacuum pump to eliminate air bubbles and residual ethanol. The as-prepared mixture was then transferred to the CF fabric preform to fabricate CF/EP composites by a vacuum assisted resin transfer molding process (VARTM). At the same time, two magnets were arranged on both sides of the CF/EP composites. Curing of the CF/EP composites took place at room temperature for 24 h under the magnetic fields. The volume fraction of CF in the composites was characterized according to the methods described in our previous work [16]. The volume fraction of the CF in this work was 52vol%.
Fig. 1. The schematic of the preparing process of Fe3O4@GO/CF/EP composites. 2.4 Characterization The phase purity of Fe3O4@GO was characterized by X-ray diffraction (XRD), using an X-ray diffractometer with a Cu Kα radiation (λ = 1.5418 Å). The interlaminar shear specimens were prepared according to the standard of ASTM 5
D2344 [17]. The mechanical properties of the composites were measured on a Shimadzu AG-X plus Mechanical Tester using a 50 kN load cell with a crosshead speed of 1 mm/min. At least five specimens were measured for each composition. Scanning electron microscope (SEM) images were obtained by a Hitachi S-4800 microscope (Japan). In particular, the fracture surfaces of the specimens after interlaminar shear testing were examined. Before examination, the fracture surfaces were cleaned using alcohol and then coated with a thin evaporated platinum layer to improve the electrical conductivity. Transmission electron microscope (TEM) images were created on a JEOL JEM-2010 instrument in bright field with an accelerating voltage of 10 kV. Acetone solution containing Fe3O4@GO was dropped onto a copper grid. After drying, it was used to take the TEM images of the Fe3O4@GO. The distribution of Fe3O4@GO in pure EP was observed by inverted phase contrast microscopy (Motic, AE2000). The content of Fe3O4 in Fe3O4@GO was analyzed using a thermogravimetric analyzer (TGA, NETZSCH TG, 209F1), The sample was heated from ambient temperature to 800 10
in air atmosphere at a heating rate of
/min.
3. Results and Discussion 3.1. Characterization of Fe3O4@GO The SEM images of the as-prepared GO and Fe3O4@GO are displayed in Fig. 2a and 2b. The TEM images of the as-prepared GO and Fe3O4@GO are displayed in Fig. 2c and 2d, respectively. As shown in Fig. 2, the in-plane size of GO is about 5 µm and
6
Fe3O4 particles are decorated on the GO surfaces. As shown in Fig. 3, the particle size distribution of Fe3O4 on GO was statistically analyzed, and the results showed that the average particle diameter was about 260 nm. However, from Fig. 2d, it can be seen that many small spheres form a Fe3O4 ball. This may be due to pH values in the range 9-10, so that Fe3O4 surface charges decrease significantly, resulting in an extensive aggregation i.e. the formation of large aggregates [18].
Fig. 2. The SEM images of the (a) as-prepared GO and (b) Fe3O4@GO, the TEM images of (c) as-prepared GO and (d) Fe3O4@GO.
7
Fig. 3. The particle size distribution of Fe3O4 on GO.
Fig. 4. TGA curve of Fe3O4@GO. The TGA curve of the as-prepared Fe3O4@GO fillers is shown in Fig. 4. It implies that the weight loss of 2.6 % between room temperature and 120
can be attributed
to the loss of adsorbed water. The weight increasing between 120 to 200 caused by the oxidation of Fe3O4 to Fe2O3. The drop to 93.8% over 200
was can be
attributed to the decomposition of GO. This means, the residual sample should be 8
Fe2O3. Therefore, the original Fe3O4 should be 90.7% in the sample. Thus, after excluding the water, a mass loading of Fe3O4 in the Fe3O4@GO can be calculated as 93.1 %. The X-ray diffraction (XRD) patterns of Fe3O4 and Fe3O4@GO are displayed in Fig. 5. Six sharp peaks at 2θ =30.3°, 35.6°, 43.3°, 53.6°, 57.1° and 62.9° can be distinguished for Fe3O4, which are assigned to the diffraction of (220), (311), (400), (422), (511) and (440) planes of Fe3O4, respectively [19, 20]. In our previous work, the XRD pattern of GO was reported, in which a broad peak appeared around 2θ =10.2o, corresponding to the (002) plane [21]. Nevertheless, there is no obvious diffraction peak of GO in the XRD pattern of Fe3O4@GO. It can be explained by the fact that the diffraction signals of Fe3O4 are significantly stronger than GO, and the weight content of GO is relatively low in Fe3O4@GO [22]. This is consistent with the values in the standard card (JCPDS card No. 65-3107).
Fig. 5. XRD patterns of the Fe3O4 and Fe3O4@GO composites. The influence of the molar ratio of Fe2+ and Fe3+ on the formation of Fe3O4 was 9
analyzed by XRD, and the results are shown in Fig. 6. The grain size of Fe3O4 particle was determined according to Scherrer formula [23]: D=
κλ
(1)
βcosθ
where D is the average grain size of the crystal (nm), λ the ray wavelength (nm), κ the peak shape factor (value is 0.81), β the corrected half width, and θ the diffraction angle. The average grain diameter of the Fe3O4 was calculated, and the results are shown in Table 1.
Fig. 6. XRD patterns of Fe3O4 prepared in different molar ratios. Table 1. The effect of the molar ratio of Fe2+ and Fe3+ on the average grain size of Fe3O4. Molar ratio of Fe2+ and Fe3+
Average grain size of Fe3O4 (nm)
1：1
13.1
1：1.25
12.2
1：1.55
11.8
1：1.75
11.3
10
The average grain size of Fe3O4 increased as the ratio of Fe2+ was increased. This is consistent with the results reported in the literature [23]. Although the average grain size of Fe3O4 obtained from the SEM data is much larger than the XRD data, this is mainly because the Scherrer formula calculates the average grain diameter of the Fe3O4, whereas the results observed by SEM and TEM refer to agglomerates of Fe3O4 [18]. The as-prepared GO, Fe3O4 and Fe3O4@GO was also characterized by FTIR to determine its surface functional groups. The results are shown in Fig. 7. It can be observed from the FTIR spectrum that the GO surface is rich in oxygen-containing functional groups, and the peaks at 3392 and 1070 cm−1 can be ascribed to the stretching vibration of -OH and alkoxy [24, 25]. Fe3O4 and Fe3O4@GO showed the Fe-O stretching vibration adsorption peak at 544 and 582 cm-1 [26]. In addition, Fe3O4@GO exhibits a stretching vibration peak of alkoxy at 1053 cm-1, but in comparison with GO, the spectrum of Fe3O4@GO showed a dramatic decrease in the intensity of the adsorption peaks of oxygen-containing functional groups, which indicated that GO has been partially reduced due to heating [27].
11
Fig. 7. FTIR spectrum of the as-prepared GO, Fe3O4 and Fe3O4@GO. 3.2. Magnetic properties of Fe3O4@GO The magnetic hysteresis measurement of the as-prepared Fe3O4@GO was carried out at room temperature in an applied magnetic field, sweeping from –796 to 796 kA/m. The room temperature magnetic hysteresis curves are displayed in Fig. 8 and 9. Different Fe3O4 modified GO samples were prepared by adjusting the molar ratio of Fe2+ and Fe3+ at a GO content of 2 mg/ml, and their magnetic properties were characterized as shown in Fig. 8. The results show that, when the molar ratio of Fe2+ and Fe3+ is 1:1.25, the Fe3O4@GO has the best magnetic properties. The saturation magnetization (Ms) is 11.2 emu/g, the coercivity (Hc) is 0.69 Gs, and the remanence (Mr) is 0.045 emu/g (Fig. 8). It is indicated that the Fe3O4@GO exhibits soft magnetic properties. The effect of GO concentration on the magnetic properties of Fe3O4@GO was also investigated (Fig. 9). It demonstrates that the Ms of Fe3O4@GO increases with decreasing GO concentration. Because the Ms is caused by Fe3O4 in the Fe3O4@GO nanocomposites [28], the relative content of Fe3O4 increases with 12
decreasing GO concentration. When the concentration of GO is 0.2 mg/ml, the Ms of Fe3O4@GO is 30.3 emu/g, the Hc is 1.22 Gs, and the Mr is 0.043 emu/g (Fig. 9).
Fig. 8. Hysteresis loops of Fe3O4@GO obtained by different Fe2+ and Fe3+ molar ratios at a GO content of 2 mg/ml.
Fig. 9. Hysteresis loops of Fe3O4@GO obtained by different GO concentrations with constant molar ratio of Fe2+ and Fe3+ at 1:1.25。 3.3. Mechanical properties of Fe3O4@GO/CF/EP composites The aligned GO structure cannot be seen from the side-view pictures of the CF/EP
13
composites due to the opaqueness of the composites. Therefore, in order to identify the orientation structure of Fe3O4@GO in the EP layer clearly, the difference between the oriented and non-oriented structures of Fe3O4@GO in a pure EP composite was observed by microscopy. As shown in Fig. 10, the non-oriented Fe3O4@GO fillers have a disordered distribution in the resin (Fig. 10a and 10c). On the other hand, the oriented Fe3O4@GO fillers are more ordered along the direction of the magnetic field (Fig. 10b and 10d). The EDAX analysis of Fe3O4@GO modified epoxy composite (Fig. 10e) also confirmed the existence of Fe3O4 in the composite.
Fig. 10. Microscope image of an epoxy composites containing 1wt% Fe3O4@GO: (a) 14
top-view image of composite without magnetic orientation, (b) top-view image of composite with magnetic orientation, (c) side-view image of composite without magnetic orientation, (d) side-view image of composite with magnetic orientation and (e) the SEM image and EDAX analysis of the composite with magnetic orientation. To investigate the effect of the oriented Fe3O4@GO on the ILSS of the CF/EP composites, the non-oriented Fe3O4@GO reinforced CF/EP composites were also studied for comparison. The ILSS of the specimens was calculated according to the following equation (2) [17]: F = 0.75 ×
P b×h
(2)
where F is the short beam shear strength (MPa), P the maximum load (N), b the measured width (mm), and h the measured thickness (mm) of the sample. The results of the ILSS of the composites are displayed in Fig. 11.
Fig. 11. Effect of orientation and contents of Fe3O4@GO relative to EP on the ILSS of CF/EP composites.
15
It indicates that the ILSS of the Fe3O4@GO/CF/EP composites prepared under a magnetic field is much higher than the composites prepared without a magnetic field. When the Fe3O4@GO content is less than 0.3 wt%, the ILSS of the CF/EP composite is improved as increasing the Fe3O4@GO content. It could be due to the enhancement effect of Fe3O4@GO on the EP [29,30]. Furthermore, the magnetic orientation showed an obvious improvement to the ILSS of the CF/EP composites at the same content of Fe3O4@GO. This could be attributed to the ordered Fe3O4@GO which can bear the major transverse shear force. The cross-sectional SEM images of the composites after the short beam shear testing are shown in Fig. 12. It can be seen that the CF/EP composite without Fe3O4@GO was dramatically damaged and the delamination is obvious as shown in Fig. 12a. The cracks grow along the interface between the CF and the EP. For the composites with 1.0 wt% non-oriented Fe3O4@GO, there are also small cracks at the interface between the fibers and the resin, but the crack propagation path of the fracture surface is clearly dispersed and the delamination is not as obvious (Fig. 12b). Moreover, there are no obvious cracks in the composites with 1.0 wt% oriented Fe3O4@GO, as displayed in Fig. 12c. It became evident that the optimal content of oriented Fe3O4@GO to improve the ILSS of the CF/EP composite is 1.0 wt% (Fig. 11). The ILSS of the CF/EP composite reinforced by non-oriented Fe3O4@GO reached a peak value of 48.05 MPa at 0.3 wt% Fe3O4@GO. While the ILSS of the CF/EP composite reinforced by oriented Fe3O4@GO reaches peak value of 59.99 MPa at 1.0 wt% of Fe3O4@GO. However, the ILSS of the CF/EP composites reinforced by oriented or non-oriented Fe3O4@GO
16
decreased with a further increase in the Fe3O4@GO content above the optimal content. The declining tendency seems to be caused by a reaction of the functional group of Fe3O4@GO with the epoxy groups, which influences the curing degree of the EP resin [13]. In addition, defects or aggregation of Fe3O4@GO generated as the content of Fe3O4@GO exceeded the optimal value might also be the reason for the decreasing ILSS of the CF/EP composites [31].
Fig. 12. SEM images of the CF/EP composites: (a) pure CF/EP composites; (b) CF/EP composites with 1.0 wt% non-oriented Fe3O4@GO; (c) cross section of CF/EP composites with 1.0 wt% oriented Fe3O4@GO. In addition, the flexural and tensile properties of the CF/EP composites were investigated; the results are shown in Fig. 13 and 14, respectively. The effects of orientated Fe3O4@GO on the flexural and tensile properties of the CF/EP composite are similar to that of the ILSS. The flexural strength of the composites without orientation was only increased by 4.6% at a 0.5 wt% Fe3O4@GO content. However, the flexural strength of the composite was increased by 29.7% at a content of 0.3 wt% oriented Fe3O4@GO. Moreover, the non-oriented Fe3O4@GO can increase the tensile strength of the composite by 25%. While the tensile strength of the oriented Fe3O4@GO/CF/EP composite can be increased by 40.9%. Furthermore, the flexural and tensile strength of the magnetic oriented composites are much higher than the 17
composites without magnetic orientation at the same content of Fe3O4@GO. It can be concluded that the orientation of the Fe3O4@GO has not only an excellent reinforcing effect on the ILSS of the CF/EP composites but can also greatly improves the flexural and tensile strength of the CF/EP composites. This should be attributed to the oriented Fe3O4@GO which can bear the major transverse shear force.
Fig. 13. The effect of orientation and content of Fe3O4@GO on the flexural strength of CF/EP composites.
Fig. 14. The effect of orientation and content of Fe3O4@GO on the tensile strength of 18
CF/EP composites.
4. Conclusions Fe3O4 magnetic particles can be decorated onto the surface of GO. The optimal molar ratio of Fe2+ and Fe3+ was 1:1.25 for preparing the Fe3O4@GO fillers. The Ms of Fe3O4@GO increased with decreasing GO concentration. With increasing the Fe3O4@GO content, the ILSS, flexural and tensile strength of the CF/EP composite firstly increased and then decreased. In addition, the oriented Fe3O4@GO can improve the mechanical properties of the CF/EP composite much more effectively than the non-oriented Fe3O4@GO. This indicates that the orientation of GO can be a potential method to improve the mechanical properties of CF/EP composites.
CRediT authorship contribution statement Xiao-Jun Shen: Conceptualization, Data curation, Investigation, Methodology, Writing - original draft, Writing - review & editing, Funding acquisition, Project administration, Supervision. Chen-Yang Dang: Data curation, Investigation, Methodology, Validation, Writing - original draft. Bo-Lin Tang: Data curation, Formal analysis, Validation. Xiao-Hui Yang: Data curation, Investigation. Hui-Jie
Nie: Data curation, Methodology. Jing-Jing Lu: Data curation. Tong-Tong Zhang: Data curation. Klaus Friedrich: Methodology, Supervision, Writing - review & editing.
Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 11502096); the program of China Scholarships Council (No.
19
201408330128); the Open Project Program of Key Laboratory of Yarn Materials Forming and Composite Processing Technology of Zhejiang Province (Nos. MTC 2019-04 and MTC 2019-12) and the Student Research Training of Jiaxing University (Nos. CD8517193243 and CD8517193244).
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2017;101:143-50. [27] Moriche R, Sánchez M, Jiménez-Suárez A, Prolongo SG, Ureña A. Strain monitoring mechanisms of sensors based on the addition of graphene nanoplatelets into an epoxy matrix. Composites Science and Technology. 2016;123:65-70. [28] Herea D-D, Chiriac H, Lupu N. Preparation and characterization of magnetic nanoparticles with controlled magnetization. Journal of Nanoparticle Research. 2011;13:4357-69. [29] Li P, Zheng Y, Wu Y, Qu P, Yang R, Li M, et al. Multifunctional liquid-like graphene@Fe3O4 hybrid nanofluid and its epoxy nanocomposites. Polymer Composites. 2016;37:3474-85. [30] He Y, Chen Q, Yang S, Lu C, Feng M, Jiang Y, et al. Micro-crack behavior of carbon fiber reinforced Fe3O4/graphene oxide modified epoxy composites for cryogenic application. Composites Part A: Applied Science and Manufacturing. 2018;108:12-22. [31] Lee M-W, Wang T-Y, Tsai J-L. Mechanical properties of nanocomposites with functionalized graphene. Journal of Composite Materials. 2016;50:3779-89.
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The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Highlights： • The interlaminar shear (ILSS), flexural and tensile strength of a carbon fabric/epoxy composite can be simultaneously improved by oriented Fe3O4@GO.
• The Fe3O4@GO can form an oriented structure in the carbon fabric/epoxy composites by magnetic field orientation.
• The optimal content of oriented Fe3O4@GO for enhancing the ILSS of the carbon fabric/epoxy composite is 1 wt%.
• The optimal molar ratio of Fe2+ and Fe3+ for preparing Fe3O4@GO nanocomposites was found to be 1:1.25.
Manuscript ID: JMAD-D-19-02331
Dear Editor I would like to declare on behalf of my co-authors that all funds that support this work have already been mentioned in the Acknowledgement section. Each author's contribution to this article is also listed in the article. No conflict of interest exits in the submission of this manuscript, and manuscript is approved by all authors for publication.
Xiao-Jun Shen (PhD/Associate Professor/Group Leader) College of Materials and Textile Engineering, Jiaxing University Jiaxing 314001, Zhejiang Province, China Tel.: +86-573-83643022 E-mail address: [email protected]
S0264-1275(19)30695-1
DOI:
https://doi.org/10.1016/j.matdes.2019.108257
Reference:
JMADE 108257
To appear in:
Materials & Design
Received Date: 5 August 2019 Revised Date:
5 October 2019
Accepted Date: 5 October 2019
Please cite this article as: X.-J. Shen, C.-Y. Dang, B.-L. Tang, X.-H. Yang, H.-J. Nie, J.-J. Lu, T.-T. Zhang, K. Friedrich, The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites, Materials & Design (2019), doi: https://doi.org/10.1016/ j.matdes.2019.108257. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2019 Published by Elsevier Ltd.
Manuscript ID: JMAD-D-19-02331
Dear Editor I would like to declare on behalf of my co-authors that the work described was original research that has not been published previously, and not under consideration for publication elsewhere, in whole or in part. All the authors listed have approved the manuscript that is enclosed.
Xiao-Jun Shen (PhD/Associate Professor/Group Leader) College of Materials and Textile Engineering, Jiaxing University Jiaxing 314001, Zhejiang Province, China Tel.: +86-573-83643022 E-mail address: [email protected]
The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Graphical abstract:
The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Xiao-Jun Shena,b*, Chen-Yang Danga,c, Bo-Lin Tanga, Xiao-Hui Yanga, Hui-Jie Niea,c, Jing-Jing Lua, Tong-Tong Zhanga, Klaus Friedrichb* a
Key Laboratory of Yarn Materials Forming and Composite Processing Technology
of Zhejiang Province, Jiaxing University, Jiaxing, 314001, China. b
Institute for Composite Materials, Technical University of Kaiserslautern,
Kaiserslautern, D-67663, Germany. c
School of Materials Science and Engineering, Changzhou University, Changzhou,
213164, China. ABSTRACT In this study, nano Fe3O4 functionalized graphene oxide (Fe3O4@GO) was employed to enhance the interlaminar shear strength (ILSS) of carbon fabric/epoxy (CF/EP) composites. The composite was fabricated via a vacuum-assisted resin transfer molding process under a magnetic field. The microstructure and reinforcement mechanism of the CF/EP composite was further investigated. The results indicate that the Fe3O4@GO can increase the ILSS of the CF/EP composite by 12.9%, and it can further enhance it to 41% under the magnetic field orientation. Furthermore, it was observed that the oriented Fe3O4@GO can also improve the flexural strength and tensile strength of the CF/EP composite by 29.7% and 40.9%, respectively. The main reason is that the oriented GO arrangement is better ordered and thus can withstand more lateral loads inside the composite. Keywords: Carbon fiber; Polymer-matrix composites (PMCs); Epoxy; Interlaminar shear strength; Magnetic oriented graphene oxide *Corresponding author: Tel: +86-573-83643022. E-mail address: [email protected] (X.-J. Shen), [email protected] (K. Friedrich).
1
1. Introduction Carbon fabric reinforced epoxy (CF/EP) composites have been widely used in many areas, including automobile, aerospace, military, marine, etc., due to their unique properties, such as high strength, lightweight and high modulus [1-4]. However, most of the CF/EP composites are laminated plate structures. The strength in the through-thickness direction is relatively low due to the fact that there are no fibers in the thickness direction. Furthermore, the low strength in the through-thickness direction generally leads to delaminations in the composites, which limits the application of CF/EP composites [1, 5, 6]. The interlaminar shear strength (ILSS) of CF/EP composites depends on the strength of EP and the interfacial adhesion between CF and EP [5, 7]. Thus to improve the ILSS of CF/EP composites, two kinds of methods can be used. On the one hand, the surface of CF should be treated. Wu et al. modified the CF surface by synergistic modification of electrochemical oxidation and sizing treatment to increase the surface activity of CF, which ultimately increased the ILSS of the composite by 158% [8]. Qi et al. reported that grafting rigid (p-phenylenediamine) and flexible structures (ethylenediamine) to the CF surface could improve the interfacial properties of composites. The rigid and flexible structures increased the ILSS of the composite by 44.8% and 38.6%, respectively [9]. On the other hand, the strength of EP can be reinforced by introducing some nanofillers such as nano SiO2, nano TiO2, carbon nanotubes and graphene and its derivatives into the EP matrix [10]. Among them, graphene oxide (GO) is regarded as the ideal nanofiller for enhancing epoxy resins
2
because of its functional groups, such as carboxyl and hydroxyl groups. The latter can react with EP to achieve good interfacial adhesion between EP and GO [11-13]. Bhanuprakash et al. reported that GO can effectively improve the interfacial properties between CF and EP, and increase the ILSS of composites by 47% [2]. However, the disordered structure of the GO is easier to agglomerate than the oriented GO, which is not conducive to fully exerting the enhancement effect of the GO in the composites. This work was inspired by the honeycomb panel model: in the honeycomb panel model, the honeycomb core material plays a major role in bearing the lateral shear force [14]. The honeycomb core layer can be simplified into a plurality of longitudinal support faces. Therefore, in this work the GO platelets were oriented as longitudinal support surfaces between the layers of the carbon fabric. In this way, the oriented GO is supposed to carry the major transverse shear force in the weakest area of the CF/EP composite material (between the CF layers) and to prevent the lateral micro cracks expanding between the composite layers. 2. Experimental Section 2.1 Basic Materials Natural graphite powders were purchased from Qingdao Jinrilai Shimo Co. Ltd, China. Carbon fabric (T300, 3K) was bought from Jiaxing Longshine Carbon Fiber Co. Ltd, China. FeCl3·6H2O and FeSO4·7H2O were obtained from Lanxi Yongli Chemical Co. Ltd, China. Concentrated sulfuric acid and hydrochloric acid were purchased from Xiaoshan Chemical Reagent Co. Ltd, China. EP (diglycidyl ether of
3
bisphenol A) resin and the curing agent (593) were obtained from Haining Hailong Chemical Co. Ltd, China. Ethanol, Sodium nitrate and potassium permanganate were purchased from Xiaoshan Chemical Reagent Co. Ltd, China, and used as received. 2.2 Preparation of Fe3O4@GO Graphene oxide (GO) was prepared according to our previous work [15]. Under a nitrogen atmosphere, FeCl3·6H2O and FeSO4·7H2O were added to deionized water (60 ml), and the resultant mixture was treated by ultrasonic technique (400 W) for 0.5 h. The ratio of Fe2+ to Fe3+ was 1:1.25 and the total amount was 0.03 mol. After that, the above mixture was added to a GO suspension (200 ml, 0.2 mg/ml) drop by drop with mechanical stirring. Then, the resultant mixture was heated up to 60
and the
pH value of the mixture was tuned to 9-10 by quickly adding ammonium hydroxide. After that, the mixture was stirred for 2 h with constant temperature. Then, the resultant mixture was washed by deionized water several times till the pH value closed to 7. 2.3 Preparation of Fe3O4@GO/carbon fabric/epoxy composites The schematic of the preparing process of CF/EP composites is displayed in Fig. 1. The as-prepared Fe3O4@GO was dispersed in ethanol to form a 0.2 mg/ml suspension. Then, the above suspension was treated by ultrasonication (400 W) for 0.5 h. After that, the epoxy resin was mixed with the Fe3O4@GO suspension. The resulting mixture was mechanically stirred for 0.5 h, and treated by ultrasonication for another 0.5 h. It was heated in an oven at 80
for 24 h to remove the ethanol. Afterwards, the
curing agent (593) was added to the mixture with a ratio of 30 to 100 (593: EP). The
4
resultant suspension was degassed with a vacuum pump to eliminate air bubbles and residual ethanol. The as-prepared mixture was then transferred to the CF fabric preform to fabricate CF/EP composites by a vacuum assisted resin transfer molding process (VARTM). At the same time, two magnets were arranged on both sides of the CF/EP composites. Curing of the CF/EP composites took place at room temperature for 24 h under the magnetic fields. The volume fraction of CF in the composites was characterized according to the methods described in our previous work [16]. The volume fraction of the CF in this work was 52vol%.
Fig. 1. The schematic of the preparing process of Fe3O4@GO/CF/EP composites. 2.4 Characterization The phase purity of Fe3O4@GO was characterized by X-ray diffraction (XRD), using an X-ray diffractometer with a Cu Kα radiation (λ = 1.5418 Å). The interlaminar shear specimens were prepared according to the standard of ASTM 5
D2344 [17]. The mechanical properties of the composites were measured on a Shimadzu AG-X plus Mechanical Tester using a 50 kN load cell with a crosshead speed of 1 mm/min. At least five specimens were measured for each composition. Scanning electron microscope (SEM) images were obtained by a Hitachi S-4800 microscope (Japan). In particular, the fracture surfaces of the specimens after interlaminar shear testing were examined. Before examination, the fracture surfaces were cleaned using alcohol and then coated with a thin evaporated platinum layer to improve the electrical conductivity. Transmission electron microscope (TEM) images were created on a JEOL JEM-2010 instrument in bright field with an accelerating voltage of 10 kV. Acetone solution containing Fe3O4@GO was dropped onto a copper grid. After drying, it was used to take the TEM images of the Fe3O4@GO. The distribution of Fe3O4@GO in pure EP was observed by inverted phase contrast microscopy (Motic, AE2000). The content of Fe3O4 in Fe3O4@GO was analyzed using a thermogravimetric analyzer (TGA, NETZSCH TG, 209F1), The sample was heated from ambient temperature to 800 10
in air atmosphere at a heating rate of
/min.
3. Results and Discussion 3.1. Characterization of Fe3O4@GO The SEM images of the as-prepared GO and Fe3O4@GO are displayed in Fig. 2a and 2b. The TEM images of the as-prepared GO and Fe3O4@GO are displayed in Fig. 2c and 2d, respectively. As shown in Fig. 2, the in-plane size of GO is about 5 µm and
6
Fe3O4 particles are decorated on the GO surfaces. As shown in Fig. 3, the particle size distribution of Fe3O4 on GO was statistically analyzed, and the results showed that the average particle diameter was about 260 nm. However, from Fig. 2d, it can be seen that many small spheres form a Fe3O4 ball. This may be due to pH values in the range 9-10, so that Fe3O4 surface charges decrease significantly, resulting in an extensive aggregation i.e. the formation of large aggregates [18].
Fig. 2. The SEM images of the (a) as-prepared GO and (b) Fe3O4@GO, the TEM images of (c) as-prepared GO and (d) Fe3O4@GO.
7
Fig. 3. The particle size distribution of Fe3O4 on GO.
Fig. 4. TGA curve of Fe3O4@GO. The TGA curve of the as-prepared Fe3O4@GO fillers is shown in Fig. 4. It implies that the weight loss of 2.6 % between room temperature and 120
can be attributed
to the loss of adsorbed water. The weight increasing between 120 to 200 caused by the oxidation of Fe3O4 to Fe2O3. The drop to 93.8% over 200
was can be
attributed to the decomposition of GO. This means, the residual sample should be 8
Fe2O3. Therefore, the original Fe3O4 should be 90.7% in the sample. Thus, after excluding the water, a mass loading of Fe3O4 in the Fe3O4@GO can be calculated as 93.1 %. The X-ray diffraction (XRD) patterns of Fe3O4 and Fe3O4@GO are displayed in Fig. 5. Six sharp peaks at 2θ =30.3°, 35.6°, 43.3°, 53.6°, 57.1° and 62.9° can be distinguished for Fe3O4, which are assigned to the diffraction of (220), (311), (400), (422), (511) and (440) planes of Fe3O4, respectively [19, 20]. In our previous work, the XRD pattern of GO was reported, in which a broad peak appeared around 2θ =10.2o, corresponding to the (002) plane [21]. Nevertheless, there is no obvious diffraction peak of GO in the XRD pattern of Fe3O4@GO. It can be explained by the fact that the diffraction signals of Fe3O4 are significantly stronger than GO, and the weight content of GO is relatively low in Fe3O4@GO [22]. This is consistent with the values in the standard card (JCPDS card No. 65-3107).
Fig. 5. XRD patterns of the Fe3O4 and Fe3O4@GO composites. The influence of the molar ratio of Fe2+ and Fe3+ on the formation of Fe3O4 was 9
analyzed by XRD, and the results are shown in Fig. 6. The grain size of Fe3O4 particle was determined according to Scherrer formula [23]: D=
κλ
(1)
βcosθ
where D is the average grain size of the crystal (nm), λ the ray wavelength (nm), κ the peak shape factor (value is 0.81), β the corrected half width, and θ the diffraction angle. The average grain diameter of the Fe3O4 was calculated, and the results are shown in Table 1.
Fig. 6. XRD patterns of Fe3O4 prepared in different molar ratios. Table 1. The effect of the molar ratio of Fe2+ and Fe3+ on the average grain size of Fe3O4. Molar ratio of Fe2+ and Fe3+
Average grain size of Fe3O4 (nm)
1：1
13.1
1：1.25
12.2
1：1.55
11.8
1：1.75
11.3
10
The average grain size of Fe3O4 increased as the ratio of Fe2+ was increased. This is consistent with the results reported in the literature [23]. Although the average grain size of Fe3O4 obtained from the SEM data is much larger than the XRD data, this is mainly because the Scherrer formula calculates the average grain diameter of the Fe3O4, whereas the results observed by SEM and TEM refer to agglomerates of Fe3O4 [18]. The as-prepared GO, Fe3O4 and Fe3O4@GO was also characterized by FTIR to determine its surface functional groups. The results are shown in Fig. 7. It can be observed from the FTIR spectrum that the GO surface is rich in oxygen-containing functional groups, and the peaks at 3392 and 1070 cm−1 can be ascribed to the stretching vibration of -OH and alkoxy [24, 25]. Fe3O4 and Fe3O4@GO showed the Fe-O stretching vibration adsorption peak at 544 and 582 cm-1 [26]. In addition, Fe3O4@GO exhibits a stretching vibration peak of alkoxy at 1053 cm-1, but in comparison with GO, the spectrum of Fe3O4@GO showed a dramatic decrease in the intensity of the adsorption peaks of oxygen-containing functional groups, which indicated that GO has been partially reduced due to heating [27].
11
Fig. 7. FTIR spectrum of the as-prepared GO, Fe3O4 and Fe3O4@GO. 3.2. Magnetic properties of Fe3O4@GO The magnetic hysteresis measurement of the as-prepared Fe3O4@GO was carried out at room temperature in an applied magnetic field, sweeping from –796 to 796 kA/m. The room temperature magnetic hysteresis curves are displayed in Fig. 8 and 9. Different Fe3O4 modified GO samples were prepared by adjusting the molar ratio of Fe2+ and Fe3+ at a GO content of 2 mg/ml, and their magnetic properties were characterized as shown in Fig. 8. The results show that, when the molar ratio of Fe2+ and Fe3+ is 1:1.25, the Fe3O4@GO has the best magnetic properties. The saturation magnetization (Ms) is 11.2 emu/g, the coercivity (Hc) is 0.69 Gs, and the remanence (Mr) is 0.045 emu/g (Fig. 8). It is indicated that the Fe3O4@GO exhibits soft magnetic properties. The effect of GO concentration on the magnetic properties of Fe3O4@GO was also investigated (Fig. 9). It demonstrates that the Ms of Fe3O4@GO increases with decreasing GO concentration. Because the Ms is caused by Fe3O4 in the Fe3O4@GO nanocomposites [28], the relative content of Fe3O4 increases with 12
decreasing GO concentration. When the concentration of GO is 0.2 mg/ml, the Ms of Fe3O4@GO is 30.3 emu/g, the Hc is 1.22 Gs, and the Mr is 0.043 emu/g (Fig. 9).
Fig. 8. Hysteresis loops of Fe3O4@GO obtained by different Fe2+ and Fe3+ molar ratios at a GO content of 2 mg/ml.
Fig. 9. Hysteresis loops of Fe3O4@GO obtained by different GO concentrations with constant molar ratio of Fe2+ and Fe3+ at 1:1.25。 3.3. Mechanical properties of Fe3O4@GO/CF/EP composites The aligned GO structure cannot be seen from the side-view pictures of the CF/EP
13
composites due to the opaqueness of the composites. Therefore, in order to identify the orientation structure of Fe3O4@GO in the EP layer clearly, the difference between the oriented and non-oriented structures of Fe3O4@GO in a pure EP composite was observed by microscopy. As shown in Fig. 10, the non-oriented Fe3O4@GO fillers have a disordered distribution in the resin (Fig. 10a and 10c). On the other hand, the oriented Fe3O4@GO fillers are more ordered along the direction of the magnetic field (Fig. 10b and 10d). The EDAX analysis of Fe3O4@GO modified epoxy composite (Fig. 10e) also confirmed the existence of Fe3O4 in the composite.
Fig. 10. Microscope image of an epoxy composites containing 1wt% Fe3O4@GO: (a) 14
top-view image of composite without magnetic orientation, (b) top-view image of composite with magnetic orientation, (c) side-view image of composite without magnetic orientation, (d) side-view image of composite with magnetic orientation and (e) the SEM image and EDAX analysis of the composite with magnetic orientation. To investigate the effect of the oriented Fe3O4@GO on the ILSS of the CF/EP composites, the non-oriented Fe3O4@GO reinforced CF/EP composites were also studied for comparison. The ILSS of the specimens was calculated according to the following equation (2) [17]: F = 0.75 ×
P b×h
(2)
where F is the short beam shear strength (MPa), P the maximum load (N), b the measured width (mm), and h the measured thickness (mm) of the sample. The results of the ILSS of the composites are displayed in Fig. 11.
Fig. 11. Effect of orientation and contents of Fe3O4@GO relative to EP on the ILSS of CF/EP composites.
15
It indicates that the ILSS of the Fe3O4@GO/CF/EP composites prepared under a magnetic field is much higher than the composites prepared without a magnetic field. When the Fe3O4@GO content is less than 0.3 wt%, the ILSS of the CF/EP composite is improved as increasing the Fe3O4@GO content. It could be due to the enhancement effect of Fe3O4@GO on the EP [29,30]. Furthermore, the magnetic orientation showed an obvious improvement to the ILSS of the CF/EP composites at the same content of Fe3O4@GO. This could be attributed to the ordered Fe3O4@GO which can bear the major transverse shear force. The cross-sectional SEM images of the composites after the short beam shear testing are shown in Fig. 12. It can be seen that the CF/EP composite without Fe3O4@GO was dramatically damaged and the delamination is obvious as shown in Fig. 12a. The cracks grow along the interface between the CF and the EP. For the composites with 1.0 wt% non-oriented Fe3O4@GO, there are also small cracks at the interface between the fibers and the resin, but the crack propagation path of the fracture surface is clearly dispersed and the delamination is not as obvious (Fig. 12b). Moreover, there are no obvious cracks in the composites with 1.0 wt% oriented Fe3O4@GO, as displayed in Fig. 12c. It became evident that the optimal content of oriented Fe3O4@GO to improve the ILSS of the CF/EP composite is 1.0 wt% (Fig. 11). The ILSS of the CF/EP composite reinforced by non-oriented Fe3O4@GO reached a peak value of 48.05 MPa at 0.3 wt% Fe3O4@GO. While the ILSS of the CF/EP composite reinforced by oriented Fe3O4@GO reaches peak value of 59.99 MPa at 1.0 wt% of Fe3O4@GO. However, the ILSS of the CF/EP composites reinforced by oriented or non-oriented Fe3O4@GO
16
decreased with a further increase in the Fe3O4@GO content above the optimal content. The declining tendency seems to be caused by a reaction of the functional group of Fe3O4@GO with the epoxy groups, which influences the curing degree of the EP resin [13]. In addition, defects or aggregation of Fe3O4@GO generated as the content of Fe3O4@GO exceeded the optimal value might also be the reason for the decreasing ILSS of the CF/EP composites [31].
Fig. 12. SEM images of the CF/EP composites: (a) pure CF/EP composites; (b) CF/EP composites with 1.0 wt% non-oriented Fe3O4@GO; (c) cross section of CF/EP composites with 1.0 wt% oriented Fe3O4@GO. In addition, the flexural and tensile properties of the CF/EP composites were investigated; the results are shown in Fig. 13 and 14, respectively. The effects of orientated Fe3O4@GO on the flexural and tensile properties of the CF/EP composite are similar to that of the ILSS. The flexural strength of the composites without orientation was only increased by 4.6% at a 0.5 wt% Fe3O4@GO content. However, the flexural strength of the composite was increased by 29.7% at a content of 0.3 wt% oriented Fe3O4@GO. Moreover, the non-oriented Fe3O4@GO can increase the tensile strength of the composite by 25%. While the tensile strength of the oriented Fe3O4@GO/CF/EP composite can be increased by 40.9%. Furthermore, the flexural and tensile strength of the magnetic oriented composites are much higher than the 17
composites without magnetic orientation at the same content of Fe3O4@GO. It can be concluded that the orientation of the Fe3O4@GO has not only an excellent reinforcing effect on the ILSS of the CF/EP composites but can also greatly improves the flexural and tensile strength of the CF/EP composites. This should be attributed to the oriented Fe3O4@GO which can bear the major transverse shear force.
Fig. 13. The effect of orientation and content of Fe3O4@GO on the flexural strength of CF/EP composites.
Fig. 14. The effect of orientation and content of Fe3O4@GO on the tensile strength of 18
CF/EP composites.
4. Conclusions Fe3O4 magnetic particles can be decorated onto the surface of GO. The optimal molar ratio of Fe2+ and Fe3+ was 1:1.25 for preparing the Fe3O4@GO fillers. The Ms of Fe3O4@GO increased with decreasing GO concentration. With increasing the Fe3O4@GO content, the ILSS, flexural and tensile strength of the CF/EP composite firstly increased and then decreased. In addition, the oriented Fe3O4@GO can improve the mechanical properties of the CF/EP composite much more effectively than the non-oriented Fe3O4@GO. This indicates that the orientation of GO can be a potential method to improve the mechanical properties of CF/EP composites.
CRediT authorship contribution statement Xiao-Jun Shen: Conceptualization, Data curation, Investigation, Methodology, Writing - original draft, Writing - review & editing, Funding acquisition, Project administration, Supervision. Chen-Yang Dang: Data curation, Investigation, Methodology, Validation, Writing - original draft. Bo-Lin Tang: Data curation, Formal analysis, Validation. Xiao-Hui Yang: Data curation, Investigation. Hui-Jie
Nie: Data curation, Methodology. Jing-Jing Lu: Data curation. Tong-Tong Zhang: Data curation. Klaus Friedrich: Methodology, Supervision, Writing - review & editing.
Acknowledgements This work was financially supported by the National Natural Science Foundation of China (No. 11502096); the program of China Scholarships Council (No.
19
201408330128); the Open Project Program of Key Laboratory of Yarn Materials Forming and Composite Processing Technology of Zhejiang Province (Nos. MTC 2019-04 and MTC 2019-12) and the Student Research Training of Jiaxing University (Nos. CD8517193243 and CD8517193244).
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The reinforcing effect of oriented graphene on the interlaminar shear strength of carbon fabric/epoxy composites Highlights： • The interlaminar shear (ILSS), flexural and tensile strength of a carbon fabric/epoxy composite can be simultaneously improved by oriented Fe3O4@GO.
• The Fe3O4@GO can form an oriented structure in the carbon fabric/epoxy composites by magnetic field orientation.
• The optimal content of oriented Fe3O4@GO for enhancing the ILSS of the carbon fabric/epoxy composite is 1 wt%.
• The optimal molar ratio of Fe2+ and Fe3+ for preparing Fe3O4@GO nanocomposites was found to be 1:1.25.
Manuscript ID: JMAD-D-19-02331
Dear Editor I would like to declare on behalf of my co-authors that all funds that support this work have already been mentioned in the Acknowledgement section. Each author's contribution to this article is also listed in the article. No conflict of interest exits in the submission of this manuscript, and manuscript is approved by all authors for publication.
Xiao-Jun Shen (PhD/Associate Professor/Group Leader) College of Materials and Textile Engineering, Jiaxing University Jiaxing 314001, Zhejiang Province, China Tel.: +86-573-83643022 E-mail address: [email protected]