Elsevier

Surface and Coatings Technology

Volume 272, 25 June 2015, Pages 176-181
Surface and Coatings Technology

Influence of graphene oxide coatings on carbon fiber by ultrasonically assisted electrophoretic deposition on its composite interfacial property

https://doi.org/10.1016/j.surfcoat.2015.04.008Get rights and content

Highlights

  • Graphene oxide coated carbon fiber was prepared by EPD.

  • SEM results indicate that fiber surfaces were deposited with GO.

  • Ultrasonic is beneficial to EPD of GO on carbon fiber surface.

  • GO enhanced the surface activity and wettability of carbon fibers.

  • GO has contributed to the interfacial properties of composite.

Abstract

Graphene oxide coatings were utilized to enhance the interfacial properties of carbon fibers. In this work, a facile route is proposed to prepare graphene oxide/carbon fiber hybrid fiber via ultrasonically assisted electrophoretic deposition (EPD) without complex chemical reactions and long processing time. Surface functional group, surface roughness and surface morphologies of carbon fibers were examined by Fourier transform infrared spectrometer (FTIR), atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. Surface free energy of the fiber was characterized by dynamic contact angle analysis (DCAA). The results indicated that the deposition of graphene oxide introduced some polar groups to carbon fiber surfaces and changed the surface morphologies of carbon fibers. Surface wettability of carbon fibers may be significantly improved by increasing surface free energy of the fibers due to the deposition of graphene oxide. Comparing the results with EPD-only, ultrasonically assisted EPD increased the thickness and uniformity of graphene oxide coatings whereas only sparse deposition formed without ultrasonic. Short beam shear test was performed to examine the impact of carbon fiber functionalization on the mechanical properties of the carbon fiber/epoxy resin composites. An improvement of 55% from 36.7 to 56.9 MPa in interlaminar shear strength confirms the remarkable improvement in the interfacial adhesion strength of the composites.

Graphical abstract

Introduction

Carbon fiber (CF) was developed into an important reinforcement material used in the fabrication of high performance composites. The mechanical properties of carbon fiber reinforce composite are closely related to its interfacial bond strength of carbon fiber and matrix. Accordingly, the interface plays a pivotal role in stress transfer, the degree of which determines important design criteria including strength, stiffness, and weight. However, the interface bonding of untreated carbon fiber that has large surface inertia and resin matrix is weak which affects the carbon fiber composite material's excellent performance into full play [1], [2], [3], [4]. As a result, extensive research have been devoted to the surface treatment of CF to improve interfacial properties of CF reinforced composites, such as sizing process [5], electrochemical method [6], plasma treatment [7], [8] and preparation of graphene oxide (GO)/CF hybrid fiber [9]. Among these methods, introducing GO on the surface of CF can improve the interfacial adhesion significantly, because GO on carbon fiber surface can well-combine with the epoxy due to its epoxide groups, and other oxygen-based functional groups can establish the hydrogen bonding with epoxy resin [10]. Grafting GO onto fiber surface is an efficient method to improve the interfacial property of CF composites [11].As the ideal nanofillers, graphene oxide (GO) in composites has been increasingly adopted to give an insight into research on hybrid composites [12], [13], [14].

Recently, many grafting methods have been proposed such as chemical grafting [15] and electrophoretic deposition (EPD) [16], [17]. Both methods reported successful attachment of GO on the fiber surface. However, too many chemical treatments and long processing time employed for chemical grafting method make it less environmentally friendly, taken together with the difficulties in processing large panels and the practical application. EPD is known to be one of the most promising manipulation techniques to produce large-scale reinforcement of nano-particles in composite applications, which offers several advantages over other surface coating approaches, such as process simplicity, uniformity of the deposited films and good control of the deposited thickness [18]. All these attributes can be exploited for the preparation of GO/CF hybrid fiber to avoid these problems [19], [20], [21], [22].

Most studies reported improved properties of composites. However, limited attention has been paid to the effect of electrophoretically deposited GO on the interface between reinforcing fibers and matrices received. In this study, a facile route is proposed to prepare graphene oxide/carbon fiber hybrid fiber via electrophoretic deposition (EPD) without complex chemical reactions and long processing time. Special emphasis has been put on the influence of graphene oxide coatings on carbon fiber by ultrasonically assisted electrophoretic deposition on its composite interfacial property. Surface roughness and surface morphologies of the fibers were examined using atomic force microscopy (AFM) and scanning electron microscopy (SEM), changes in surface chemistry were studied using Fourier transform infrared spectrometer (FTIR), surface free energy and contact angle of the fibers were characterized by dynamic contact angle analysis (DCAA), and the mechanical properties of composites were evaluated by interlaminar shear strength (ILSS).

Section snippets

Materials and processing

PAN-based CF tow (T700, 12 K and diameter about 7 μm) was purchased from Toray Industries, Japan. Natural graphite flakes (99% purity, diameter about 25 μm) were purchased from Nanjing Xianfeng. Port. Co., Ltd. The epoxy resin was bought from Yueyang Chemical Reagent Co., Ltd. of China. The curing agent was supplied by Shanghai Jingchun Chemical Reagent Co., Ltd. of China.

The CF tow was refluxed in acetone at 80 °C for 72 h, then washed with deionized water repeatedly and dried under vacuum at 80 °C

Surface roughness and surface morphologies of carbon fiber

Fig. 2 shows typical SEM micrographs of the surface and cross-section of CF at different stages. Initially, the surface of desized CF was rough and grooves were distributed in a longitudinal direction of CF (Fig. 2a), as shown in Fig. 2(c) and (e), GO was deposited on the surface of CF, which indicated that EPD was an effective method to prepare GO/CF hybrid fiber. Another observation that can be seen from the SEM images of GO/CF hybrid fiber is homogeneous and thick GO films due to ultrasonic,

Conclusions

In the present study, graphene oxide was successfully coated onto carbon fiber surfaces via ultrasonically assisted electrophoretic deposition, which avoids complex chemical reactions and long processing duration, thereby provides great potential for industrial applications. SEM and AFM analysis showed that graphene oxide film with high roughness is homogeneously formed on carbon fibers, DCAA results indicated that the deposition of GO significantly improved surface free energy of carbon fiber

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