The role of maleic anhydride functionalized graphene oxide in improving the interfacial properties of carbon fibre/bismaleimide composites

This work aims to assess the effect of maleic anhydride functionalized graphene oxide (MAH‐f‐GO) on the interfacial properties of carbon fibre/bismaleimide (BMI) composites by experimental and finite element (FE) methods. Transverse fibre bundle (TFB) specimens with different contents of MAH‐f‐GO nanoparticles were manufactured to investigate the interfacial strength of the carbon fibre/BMI composites. The fracture surface of the TFB specimens was examined by scanning electron microscopy to observe the morphologies of the fibre ? matrix interface. The coefficient of thermal expansion, cure shrinkage and elastic modulus were measured and included in the FE simulation. An FE analysis model was established to simulate the thermal residual stress distribution around the carbon fibre and to estimate the interfacial bonding strength of the TFB specimens. The combination of experimental and FE analysis results indicated that the addition of MAH‐f‐GO nanoparticles noticeably reduced the concentration of residual stress at the fibre ? matrix interface and enhanced the interfacial properties of the carbon fibre/BMI composites.© 2017 Society of Chemical Industry     

功能化石墨烯改性双马来酰亚胺复合材料的微观表征及性能

采用改进Hummers法制备氧化石墨烯（GO）,分别采用水合肼、壳聚糖、KOH还原得到了还原氧化石墨烯（rGO）并对三种还原方法做了对比,选择最佳方案;再通过离子液体（NH₂IL）对rGO功能化得到改性还原氧化石墨烯（NH₂IL-rGO）。以二烯丙基双酚A （BBA）和双酚A双烯丙基醚（BBE）为活性稀释剂,4,4'-二氨基二苯甲烷型双马来酰亚胺（MBMI）为反应单体,制备了MBMI-BBA-BBE （MBAE）树脂基体;同时以NH₂IL-rGO为增强体采用原位聚合法制备NH₂IL-rGO/MBAE复合材料。表征了石墨烯和复合材料的微观形貌并分析了石墨烯对复合材料性能的影响。结果表明：NH₂IL-rGO在树脂基体中以两相形式存在,结构完整,并赋予复合材料优异的性能。当NH₂IL-rGO含量为2%（质量）时,复合材料冲击强度和弯曲强度最大,分别为15.33 kJ/m²和142 MPa,热分解温度为435.73℃、当测试频率为100 Hz～10 kHz时介电常数发生突变达到84。     

Mechanical properties of carbon fiber composites modified with graphene oxide in the interphase

The surface topographies of carbon fibers treated by sizing agents with different graphene oxide (GO) content were investigated by scanning electron microscopy. The surface elements compositions of carbon fibers were determined by X‐ray photoelectron spectrometer. The interfacial properties of composites were studied by interfacial shear strength. The thermo‐mechanical properties of two typical specimens (CF‐G0 and CF‐G1 composites) were investigated by dynamic mechanical thermal analysis. The results showed the introduction of GO sheets on carbon fibers surfaces effectively improved the mechanical properties of carbon fibers/epoxy composites. POLYM. COMPOS., 38:2425–2432, 2017. © 2016 Society of Plastics Engineers     

Performance tuning of glass fiber/epoxy composites through interfacial modification upon integrating with dendrimer functionalized graphene oxide

In this study, glass fiber/epoxy composites were interfacially tailored by introducing polyamidoamine (PAM) dendrimer functionalized graphene oxide (GO) into epoxy matrix. Two different composites each containing varying loading fraction (0.5, 1.0, and 1.5 wt%) of GO and GO-PAM were fabricated via hot press processing. Composites were evaluated for interlaminar shear strength (ILSS), dynamic mechanical properties and thermal conductivity. The inclusion of 1.5 wt% GO-PAM resulted ~57.3%, ~42.7%, and ~54% enhancement in ILSS, storage modulus and thermal conductivity, respectively. Almost, ~71% reduction in coefficient of thermal expansion was also observed at same GO-PAM loading. Moreover, higher glass transition temperature was observed with GO-PAM addition. GO-PAM substantially improved fiber/matrix interfacial adhesion, which was witnessed through scanning electron microscopy. The enhanced thermo-mechanical performance was attributed to interfacial covalent interactions engendered by ring opening reaction between epoxy and amine moieties of PAM dendrimers. These multiscale composites with extraordinary functional properties can outperform conventional counterparts with improved reliability and performance.     

Enhanced interfacial strength and mechanical properties of carbon fiber composites by introducing functionalized silica nanoparticles into the interface

Introducing nanoparticles onto the surface of carbon fibers (CFs) is a useful method for enhancing the quality of fiber-matrix interface. In this work, a liquid sizing agent containing functionalized silica nanoparticles (SiO₂) was well prepared to improve interfacial strength and mechanical properties of composites. In order to enhance the dispersion of SiO₂ nanoparticles in sizing agent, SiO₂ nanoparticles were chemically grafted with 3-aminopropyltriethoxysilane (APS), and then silanized silica (SiO₂-APS) was introduced into the interphase by a conventional sizing process as well. Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA) confirmed the successful preparation of SiO₂-APS. Scanning electron microscopy (SEM) showed that a uniform distribution of SiO₂-APS on the fiber surface and the increased surface roughness. The sized fibers (CF/SiO₂-APS) exhibited a high surface free energy and good wettability based on a dynamic contact angle testing. Interfacial microstructure and mechanical properties of untreated and sized CFs composites were investigated. Simultaneous enhancements of interlaminar shear strength (ILSS) and impact toughness of CF/SiO₂-APS composites were achieved, increasing 44.79% in ILSS and 31.53% in impact toughness compared to those of untreated composites. Moreover, flexural strength and modulus of composites increased by 32.22 and 50.0% according to flexural test. In addition, the hydrothermal aging resistance of CF/SiO₂-APS composites has been improved significantly owing to the introduced Si-O-Si bonds at the interface.     

丁腈橡胶/功能化氧化石墨烯复合材料的研究

用硅烷偶联剂KH590对氧化石墨烯进行功能化改性,得到的功能化氧化石墨烯再通过乳液共混和机械共混等工艺制备了丁腈橡胶/功能化氧化石墨烯复合材料。表征分析了功能化氧化石墨烯的结构和表面形态,研究了丁腈橡胶/功能化氧化石墨烯复合材料的机械性能。结果显示,与氧化石墨烯相比,功能化氧化石墨烯的亲水性和表面形态均发生了较大变化,其与丁腈橡胶形成的复合材料与丁腈橡胶/氧化石墨烯复合材料相比,拉伸强度提高的幅度更大且断裂伸长率降低的幅度更小。     

Thermal stresses and effective properties calculated for fiber composites using actual cylindrically-anisotropic properties of interfacial carbon coating

Thermal stresses in composites composed of fiber (Nicalon™ or carbon fiber), pyrolytic-carbon coating and matrix (SiC) were calculated by the use of the actual properties of carbon coating, which are elastically and thermally cylindrically-anisotropic (transversely-isotropic about radial direction). They were compared with calculations with other anisotropies for the coating, including an often assumed anisotropy which is transversely-isotropic about fiber axis. It was shown that the differences in radial and hoop stresses between the actual and assumed ones could be significant. In addition, effective moduli and CTEs of a composite fiber (fiber/carbon-coating) and those of a composite matrix (carbon-coating/matrix) were derived and used to interpret the resulted thermal stresses.     

Thermal and mechanical properties of liquid silicone rubber composites filled with functionalized graphene oxide

To improve the thermal and mechanical properties of liquid silicone rubber (LSR) for application, the graphene oxide (GO) was proposed to reinforce the LSR. The GO was functionalized with triethoxyvinylsilane (TEVS) by dehydration reaction to improve the dispersion and compatibility in the matrix. The structure of the functionalized graphene oxide (TEVS‐GO) was evaluated by Thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectra, X‐ray diffraction (XRD), and energy dispersive X‐ray spectroscopy (EDX). It was found that the TEVS was successfully grafted on the surface of GO. The TEVS‐GO/LSR composites were prepared via in situ polymerization. The structure of the composites was verified by FTIR, XRD, and scanning electron microscopy (SEM). The thermal properties of the composites were characterized by TGA and thermal conductivity. The results showed that the 10% weight loss temperature (T₁₀) increased 16.0°C with only 0.3 wt % addition of TEVS‐GO and the thermal conductivity possessed a two‐fold increase, compared to the pure LSR. Furthermore, the mechanical properties were studied and results revealed that the TEVS‐GO/LSR composites with 0.3 wt % TEVS‐GO displayed a 2.3‐fold increase in tensile strength, a 2.79‐fold enhancement in tear strength, and a 1.97‐fold reinforcement in shear strength compared with the neat LSR. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42582.     

Experimental evaluation of the interfacial properties of carbon nanotube coated carbon fiber reinforced hybrid composites

A floating catalyst chemical vapor deposition (CVD) unit was utilized to grow CNT onto the surface of carbon fiber (CF). The surface morphology of the resultant fibers, CNT population density and alignment pattern were found to be depended on the CNT growth temperature, growth time, and atmospheric conditions within the CVD chamber. In contrast to the neat‐CF reinforced composites, improved interfacial shear strength (IFSS) between CF and matrix were obtained when the surface of CF was coated by CNT. Particularly, CF treatment condition for CNT‐coating with 700°C reaction temperature and 30 min reaction time has shown a considerable increase in IFSS approximately of 45% over that of the untreated fiber from which it was processed. The proper justification of fiber–matrix adhesion featured by composite interfacial properties was explained through IFSS. POLYM. COMPOS., 36:1941–1950, 2015. © 2014 Society of Plastics Engineers     

Observation of mechanical percolation in functionalized graphene oxide/elastomer composites

We have covalently functionalized graphene oxide (GO) with octadecylamine (ODA) to form GO–ODA. This material can be dispersed in tetrahydrofuran (THF) and subsequently formed into composites with polymers such as thermoplastic polyurethane (TPU). We have characterized the mechanical properties of composites of GO–ODA in TPU. No increase in stiffness was observed at loading levels below 2.5 vol%. Reinforcement appeared to start sharply at this volume fraction and subsequently increased as a power law with increasing volume fraction. This behavior is typical of percolation and shows that the low-strain stress is not increased until the functionalized graphene flakes form a percolating network. Slightly different behavior is observed for properties related to material failure. The ultimate tensile strength increased linearly with graphene content up to the percolation threshold before subsequently falling off. Similarly the strain at break was constant below the percolation threshold but fell off dramatically above it. This work shows the importance of network formation in the reinforcement of elastomeric materials.     

Fiber/Matrix mechanical interaction in carbon fiber/bismaleimide model composites

The fiber/matrix interaction of high modulus (M40) and intermediate modulus (T800) carbon fibers with a bismaleimide resin has been studied by means of three micromechanical techniques involving a single fiber, namely, fragmentation, Raman spectroscopy, and pullout. A number of chemical treatments aimed at improving the fiber/matrix stress transfer at elevated temperature were tested. The stress transfer proved to be reduced by the temperature in the same way for all interfacial conditions. The limitations to the micromechanical characterization of model composites in temperature are emphasized.     

Incorporation of hyperbranched polyamide‐functionalized graphene oxide into epoxy for improving interfacial and mechanical properties

The incorporation of hyperbranched polyamide‐functionalized graphene oxide (HPA‐GO) into epoxy was proposed to improve the interfacial and mechanical properties. Benefiting from improved dispersion and strengthened interfacial interaction, epoxy composites with HPA‐GO showed significant improvements in mechanical and thermomechanical properties at low GO loading. The interaction at the HPA‐GO/epoxy interface was investigated to confirm the occurrence of chemical bonding. Strong interfacial bonding improved the stress transfer and distribution of HPA‐GO/epoxy interface. Accordingly, the overall strength of epoxy composites was effectively improved on account of the uniform dispersion of HPA‐GO and interfacial chemical interaction between HPA‐GO and epoxy. Compared with neat epoxy resin, the inclusion of 0.10 wt% HPA‐GO led to 310.5 and 37.2% increase in impact strength and tensile strength, respectively. © 2019 Society of Chemical Industry     

Improvement of interfacial interactions in CF/PEEK composites by an s-PSF/graphene oxide compound sizing agent

The interfacial interactions of carbon fiber (CF)-reinforced polymer composites is a key factor affecting the overall performance of the material. In this work, we prepared a sulfonated poly(ether sulfone)–graphene oxide mixed sizing agent to modify the interface of CF/PEEK composites and improve the interfacial properties between the PEEK matrix and CF. Results showed that the mechanical and interfacial properties of CF/PEEK composites are improved by the sizing agent. Specifically, the flexural strength, flexural modulus and interlaminar shear strength of the materials reached 847.29 MPa, 63.77 GPa, and 73.17 MPa, respectively. Scanning electron microscopy confirmed markedly improved adhesion between the resin matrix and fibers. This work provides a simple and effective method for the preparation of high-performance CF/PEEK composites, which can improve the performance of composites without degrading the mechanical property of pristine CF.     

Effect of graphene oxide on the interlaminar fracture toughness of carbon fiber/epoxy composites

Graphene oxide (GO) nanoparticles were introduced in the interlaminar region of carbon fiber–epoxy composites by dispersing it in a thermoplastic polymer carrier such as polyvinylpyrrolidone (PVP). Mode‐I fracture toughness (G_IC) was investigated using double cantilever beam testing to evaluate the effect of the GO on the delamination behavior of the composite. The GO content was varied from 0% to 7% by weight as a function of the PVP content. Improvement of ～100% in the Mode I fracture toughness (G_IC) was observed compared to composites with no GO. The optimum amount of nanoparticles for improving the interlaminar fracture toughness was found to be ～0.007% by weight of the composite. The increase in the value of flexural strength value was also observed. Scanning electron microscopy of fracture surfaces, X‐ray diffraction, and transmission electron microscopy, and reflectance Fourier transform infrared spectra, as well as Raman spectroscopy results, are presented to support the conclusions. POLYM. ENG. SCI., 59:1199–1208 2019. © 2019 Society of Plastics Engineers     

Properties of carbon fiber and composites modified with different‐sized graphene oxide sheets

The graphene oxide (GO) sheets with different size distributions were effectively separated by a centrifugation method. The exfoliated single‐layer structure and the size of GO sheets were verified by scanning electron microscopy (SEM), atomic force microscope (AFM), and metallurgical microscope, respectively. Two different‐sized GO sheets water suspensions were obtained, which were then directly dispersed in carbon fiber (CF) sizing agent, respectively. The influences of the different‐sized GO sheets on CF and CF composites were explored. The workability in later process of CF and CF surface morphology were characterized by abrasion resistance, fluffs and breakage, stiffness, and SEM. SEM micrographs demonstrated that a nonuniform distribution of the large‐sized GO was lapped on CF whereas the small‐sized GO was uniformly leaned on CF. The interlaminar shear strength of the small‐sized GO/CF reinforced composite could reaches the maximum value. It indicated that the interfacial region between CF and polymer matrix could be enhanced by adjusting the size of GO sheets. POLYM. COMPOS., 37:2719–2726, 2016. © 2015 Society of Plastics Engineers     

Improved interfacial properties of carbon fiber-reinforced epoxy composites with Fe2O3/graphene nanosheets using a magnetic field

The performance of carbon fiber-reinforced composites largely depends on the properties of the fiber-matrix interface. Here, to improve the interfacial strength properties of carbon fiber/epoxy composites, we doped different concentrations of Fe₂O₃/graphene nanosheets onto the interfacial region of the carbon fiber composites by nano-coating technology. With the aid of the magnetic field, the arrangement of nanosheets could be controlled in the interface. The nanosheets can be arranged on the carbon fiber surface parallel or perpendicularly with different concentrations. The tensile strength and interfacial shear strength of the modified fiber microcomposites had increased by 22.1 and 44.4% respectively with 1.0 mg/mL Fe₂O₃/graphene nanosheets. The results indicated that the Fe₂O₃/graphene nanosheets have an important influence on the carbon fibers and carbon fibers composites.     

Dispersion, interfacial interaction and re-agglomeration of functionalized carbon nanotubes in epoxy composites

The surface, interfacial and dispersion properties of carbon nanotubes (CNTs), and the mechanical properties of the CNT/epoxy composites affected by CNT functionalization are investigated. It is demonstrated that there exists strong correlations between amino-functionalization, dispersion, wettability, interfacial interaction and re-agglomeration behaviour of CNTs and the corresponding mechanical and thermo-mechanical properties of CNT/epoxy composites. The amino-functionalized CNTs exhibit higher surface energy and much better wettability with epoxy resin than the pristine CNTs, and the attached amine molecules arising from the functionalization effectively inhibit the re-agglomeration of CNTs during the curing of resin. These ameliorating effects along with improved interfacial adhesion between the matrix and functionalized CNTs through covalent bonds result in improved flexural and thermo-mechanical properties compared with those without functionalization.     

Improvement of carbon fiber/PEEK hybrid fabric composites using plasma treatment

A carbon fiber (CF)/polyetheretherketone (PEEK) composite was manufactured using hybrid fabrics composed of CF and PEEK fiber. The fiber/matrix interface was modified by low temperature oxygen plasma treatment. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Fourier transform attenuated total reflection infrared spectroscopy (FTIR-ATR) were used to relate the roughness and the functionality of the CF surface with the interfacial adhesion strength of the CF/PEEK composite. Scanning electron micrographs showed that plasma treatment increased the roughness of the CF surface up to 3 min of plasma treatment time; and prolonged treatment resulted in overall smoothing. XPS results confirmed that increasing treatment time marginally increased surface functionality: treatment for more than 5 min decreased the surface functionality by removing the active site of the CF surface. In addition, flexural strength and interlaminarshear strength (ILSS) of the CF/PEEK composite were measured. Their maximum values were observed at 3 min of plasma treatment time as a result of surface roughening by plasma etching. The SEM results were correlated with mechanical properties of the CF/PEEK composite.