Grafted Carbon Fiber Research Articles

Carbon Fiber Reinforced Thermoplastics Molding by Using Direct Resistance Heating to Carbon Nanofilaments Grafted Carbon Fiber

In the automobile industry, carbon fiber reinforced thermoplastics (CFRTP) have attracted attention as potential materials to reduce the weight of the automobile body. In order to apply CFRTP to mass-produced automobile parts, it is necessary to develop the reduction of molding time and the impregnation method into the carbon fiber (CF) for the thermoplastic resin, which has relatively high viscosity. Although the conventional hot press molding uses only the heat transfer from the mold to the molding materials, it is expected to develop a new molding method for CFRTP using heat generation of the materials themselves to overcome these issues. As a method of heating the carbon fiber, there is a direct resistance heating method, in which carbon fiber is directly energized and heated by Joule heat. We have developed resistance welding methods in which carbon nanotube (CNT) grafted carbon fiber (CNT-CF) is used for the heating elements, and revealed that the higher welded strength is obtained by using CNT-CF instead of CF. Therefore, the carbon nanofilaments (CNF) grafted carbon fiber (CNF-CF) including CNF-CF is expected not only to be used as a resistance heating medium at the time of joining but also as a reinforcing fiber and as a self-heating member at the time of molding. In this study, we develop the CFRTP molding method by using direct resistance heating to CNF-CF in the hot press molding. CFRTP ([0°]20) with the volume fractions (Vf) of 40% are molded by conventional hot press and hot press with direct resistance heating to reinforcing fiber. CF or CNF-CF is used for reinforcement. CFRTP molded by hot press with direct resistance heating to CNF-CF indicated lower void content than CFRTP molded by hot press with direct resistance heating to CF. Compared to CFRTP molding by only hot press, hot press molding with direct resistance heating to CNF-CF can mold CFRTP with low void content.

Effect of Carbon Nanotube Deposition Time to the Surface of Carbon Fibres on Flexural Strength of Resistance Welded Carbon Fibre Reinforced Thermoplastics Using Carbon Nanotube Grafted Carbon Fibre as Heating Element

In recent years, carbon fibre reinforced thermoplastics (CFRTP) are expected to be used as lightweight structural materials for mass-produced vehicles. CFRTP with thermoplastics as matrix allows us to weld them using melting of matrix by heating. We have been developing a direct resistance heating method, which uses carbon fibres as the resistance heating element. Carbon nanotube (CNT) is expected to be used as additive to FRP and we reported that the fibre/matrix interfacial shear strength was improved by grafting CNT on the surface of carbon fibres and tensile lap-shear strength was improved by using CNT grafted carbon fibre as the heating element for welding. For the practical use of CFRTP for structural parts, flexural strength is also necessary to be evaluated. In this study, flexural test was carried out to clarify the effect of CNT deposition time to the surface of carbon fibres on flexural strength of resistance welded CFRTP using CNT grafted carbon fibre as the heating element. The highest flexural strength was obtained when CNT10, for which CNT is grafted on the carbon fibres for deposition time of 10 min, was used for the heating element of resistance welding. In the case of CNT deposition time of 60 min, the lowest flexural strength was obtained because of the poor impregnation of the resin into the carbon fibre due to the excess CNT on the carbon fibres.

Designing the interphase in carbon fiber polymer composites using carbon nanotubes

Experiments are conducted to quantitatively assess the effect of carbon nanotubes (CNTs) on the interfacial properties in carbon fiber/epoxy composites by directly growing CNTs on the surface of carbon fiber (CF). Wetting behavior of single carbon fiber filaments with epoxy matrix before and after CNT grafting is investigated through contact angle measurements. An improvement in wettability is observed after the incorporation of CNTs on the fiber surface. Effect of wettability on the size and properties of interphase is studied through well designed micro-mechanical tests on single fiber composites processed with unsized and CNT grafted carbon fibers. While nanoindentation testing is performed for quantitative determination of interphase size and stiffness, single fiber micro-debond tests are used to evaluate the interfacial shear strength (IFSS) in unsized carbon fiber/epoxy and CNT grafted carbon fiber/epoxy composites. Consistent with the wettability analysis, CNT grafting enhances the size, stiffness and IFSS of CF/epoxy composites. In addition, it is shown that even though larger CNT growth time on the surface of carbon fiber provides thicker interphase region but tends to degrade the stiffness of interphase and IFSS of CNT grafted carbon fiber/epoxy multiscale composites. Scanning electron microscopy (SEM) analysis of pulled-out and debonded fibers reveal different interfacial failure mechanism in the presence and absence of CNTs on the surface of CF. The present study quantitatively shows the presence of an interphase region surrounding the carbon fiber after CNT grafting on their surface. The existence of interphase is important from the view point of structural integrity of composites as it eliminates the unwanted stress concentration at the fiber/polymer interface by gradual transformation of properties from highly stiff fiber to comparatively weaker matrix. Moreover, the present study provides us a tool to design the interphase in hybrid composites as per the requirement of a specific application.

Comparison of rigid and flexible structural daimines grafted carbon fiber for enhancing the interfacial and mechanical properties of carbon fiber/epoxy composites

ABSTRACTInterfacial strength between fiber and matrix is an important factor affecting the mechanical properties of carbon fiber composites. Different daimines, ethylenediamine (EDA) and p-phenylenediamine (PPD), were grafted on carbon fiber to enhance interfacial strength of composites. Functional groups and chemical composition were tested by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Thermaogravimetric analysis and Roman spectroscopy. Scanning electron microscope was used to characterized surface morphology. Results revealed that EDA with flexible structure was more easily grafted onto surface. In contrast, PPD with rigid structure could improve the interfacial performance better. More importantly, carbon fiber grafted on both EDA and PPD had the highest wettability and interlaminar shear strength owing to the presence of sufficient functional groups on carbon fiber surface. Compared with untreated carbon fibers, the surface energy and the interlaminar shear strength of the grafted EDA and PPD carbon fibers increased by 38.57% (50.98 mN/m) and 44.81% (69.8 MPa) respectively. The investigation provides an approach to enhance the mechanical properties of fiber composites by controlling the structure of grafted components.

Recovery of cesium using NiHCF/NiAl-LDHs/CCFs composite by two-stage membrane-free ESIX process

In this work, aspartic acid-functionalized poly glycidyl methacrylate grafted carbon fibers (CCFs) were prepared by electrochemically mediated atom transfer radical polymerization to form three dimensional (3D) chelating precursor; Ni/Al layered double hydroxides and nickel hexacyanoferrate were respectively deposited in suit to form 3D functional composite for the recovery of cesium (NiHCF/NiAl-LDHs/CCFs). The characterization was confirmed by FE-SEM, XRD, IR, XPS and electrochemistry techniques. Meanwhile, a two-stage membrane-free electrically switched ion exchange sorption and desorption process- (MF-II-ESIX) was suggested for the recovery of Cs+ using NiHCF/NiAl-LDHs/CCFs from aqueous solution. The maximal adsorption capacity of 167.5 mg g−1 could be obtained at -0.4 V for 4 h in pH 6.0. The Cs+ adsorbed at NiHCF/NiAl-LDHs/CCFs could be effectively desorbed by cycle voltammeter in a potential range of −0.1 to 1.2 V with 120 cycles in pH 7.0, 0.1 M NH4Cl.

Improving the interfacial and flexural properties of carbon fiber–epoxy composites via the grafting of a hyperbranched aromatic polyamide onto a carbon fiber surface on the basis of solution polymerization

ABSTRACTHyperbranched aromatic polyamide (HBP) was grafted successfully onto carbon fibers (CFs) on the basis of solution polymerization to enhance the interfacial adhesion strength of CF‐reinforced epoxy resin composites. The microstructure and interfacial properties of the CFs before and after decoration were researched. The results indicate that HBP was deposited uniformly onto the CFs with γ‐aminopropyl triethoxysilane as the bridging agent. The active groups, roughness, and surface energy of the modified fiber [hyperbranched aromatic polyamide grafted carbon fiber (CF–HBP)] increased visibly in comparison with those of the untreated CFs. The CF–HBP composites revealed simultaneous remarkable enhancements (65.3, 34.3, and 84.8%) in their interfacial shear strength, flexural strength, and modulus, respectively; this was attributed to the improvement in the fiber–epoxy interface through enhanced chemical interactions, mechanical interlocking, and wettability. These agreed with the scanning electron microscopy observations from the fracture surface morphologies of the composites. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47232.

The synergistic action between anhydride grafted carbon fiber and intumescent flame retardant enhances flame retardancy and mechanical properties of polypropylene composites

ABSTRACTThe applications of polypropylene/carbon fiber (PP/CF) composite are hindered by the high flammability of PP substrate. This work reports a facile solvothermal method to modify CF though grafting maleic anhydride (MAH) on its surface, with the goal of enhancing the compatibility of intumescent flame retardant (IFR) with PP substrate, thus enhancing the flame-retardant and mechanical performance of the resulting PP/CF/IFR composite. The effect of maleic anhydride-g-carbon fiber (MAH-g-CF) to IFR ratio on the overall performance of the composite was assessed. The possible interactions between MAH-g-CF and IFR were characterized by dynamic thermomechanical analysis and Fourier-transform infrared spectroscopy. Results show that when 3 wt% MAH-g-CF and 22 wt% IFR were added to the PP substrate, the composite exhibited a much lower heat release rate value and smoke suppression ability. Meanwhile, the composites achieved 26.7 MPa in tensile strength and 50.6 MPa in flexural strength. We propose that MAH on MAH-g-CF acts as a compatibilizer that improves the adhesion and cross-linking between CF and IFR, thereby enhancing mechanical strength and flame-retardancy of the PP/IFR/MAH-g-CF composite.

Effects of grafting strength and density on interfacial shear strength of carbon nanotube grafted carbon fibre reinforced composites

This paper presents a test method of twin-fibre single-lap joint bonded with a micro-droplet of epoxy and subjected to tensile loading for determining fibre-matrix interfacial shear strength (IFSS). Twenty-five carbon fibre (CF)/epoxy specimens and fifty-six carbon nanotube (CNT)-grafted CF/epoxy specimens were prepared and tested. The average IFSS measured for specimens with a mean grafting density of 10.9, 25.8, 35.1 or 58.8 CNTs per μm2 can be improved by 51%, 101%, 155% and 273% (223%) respectively comparing to that without grafted CNTs. A multi-scale analytical model that relates micro-scale IFSS to nanoscale CNT grafting strength and density is developed and then used for predicting the IFSS of CNT-CF reinforced composites. There exists a good correlation between the measured and predicted IFSS of specimens with different grafting densities.

Bending Properties of CFRTP Laminate Using CNT Grafted Carbon Fiber

Carbon Fiber Reinforced Thermoplastics (CFRTP), which have a short production cycle time and high specific strength and stiffness, are focused on in the automobile industry. Generally, the mechanical properties of FRP are affected by the interfacial strength between the reinforcing fiber and matrix, so the control of the interfacial strength between the reinforcing fiber and matrix is important. Compared to CFRP with epoxy resin, the interfacial strength between the reinforcing fiber and matrix of CFRTP is relatively low. Recently, a method to improve the interfacial strength between the reinforcing fiber and matrix by grafting Carbon Nanotube (CNT) on the carbon fiber has been developed. In this study, the bending properties of CFRTP laminates using CNT grafted plain woven carbon fiber fabric were clarified. Bending strength of CFRTP laminates using CNT grafted plain woven carbon fiber fabric were higher than that using as-received plain woven carbon fiber fabric.

Effect of CNT Grafting on Carbon Fibers on Impact Properties of CFRTP Laminate

Carbon fiber reinforced thermoplastics (CFRTP) are expected to be used as a structural material for aircraft and automobiles not only for their mechanical properties such as high specific strength and high specific rigidity but also for their high recyclability and short molding time. Generally, in a composite material having a laminated structure, interlaminar delamination is often caused by an out-of-plane impact, so the interlayer property plays an important role in the mechanical properties. It has been reported that the fiber/matrix interfacial strength increases by grafting carbon nanotubes (CNT) on the carbon fiber surface. In this study, CNT grafted carbon fibers were used for reinforcement of CFRTP laminate for the improvement of impact properties of CFRTP laminates. The impact absorbed energy of the CFRTP laminate using CNT grafted carbon fibers as reinforcing fiber was higher than that using untreated CF.

Hybrid ZnO Nanorod Grafted Carbon Fiber Reinforced Polymer Composites; Randomly versus Radially Aligned Long ZnO Nanorods Growth.

Integrating nano-sized reinforcing materials into carbon fiber polymer composites (CFRPs) could enhance several aspects of their mechanical performance; e.g., interfacial strength, delamination resistance and vibrations attenuation. In this study, ZnO nanorods were grown on the surface of carbon fibers to create hybrid reinforcements. The hydrothermal synthesis of ZnO nanorods was tuned such that relatively long (>2.0 μm) nanorods can be grown. This synthesis technique requires pre-deposition of a thin seeding layer of ZnO particulates on the carbon fibers to initiate the ZnO nanorods growth. Depending on the method by which the seeding layer is deposited, the grown ZnO nanorods could display different morphologies. In this study, two different techniques were utilized to pre-deposit the ZnO seeding layer on the carbon fibers; ZnO nanoparticles/solution mixture airbrush spraying, and magnetron sputtering. The carbon fibers pre-coated with the airbrush spraying method yielded forests of randomly oriented ZnO nanorods, while the fibers pre-coated via the sputtering technique exhibited radially aligned ZnO nanorods forests. Hybrid CFRPs were fabricated based on the aforementioned carbon fiber fabrics and tested via 3-point bending dynamic mechanical analysis (DMA) and quasi-static tension tests. The loss tangent of the CFRPs, which delineates the damping capability, increased by 28% and 19% via radially and randomly grown ZnO nanorods, respectively. The in-plane tensile strength of the hybrid CFRPs were improved by 18% for the composites based on randomly oriented ZnO nanorods over the carbon fibers. The fractographs of the tension samples were also captured to reveal the role of the long ZnO nanorods in the in-plane performance of the hybrid CFRPs.

Rheology, Non-Isothermal Crystallization Behavior, Mechanical and Thermal Properties of PMMA-Modified Carbon Fiber-Reinforced Poly(Ethylene Terephthalate) Composites.

Poly(ethylene terephthalate) (PET) composites containing carbon fiber (CF) or polymethyl methacrylate (PMMA)-grafted carbon fiber (PMMA-g-CF) were prepared by melt compounding. The rheology, non-isothermal crystallization behavior, and mechanical and thermal properties of pure PET, PET/CF and PET/PMMA-g-CF composites were investigated. The results show that the addition of CF or PMMA-g-CF significantly increases the storage modulus (G′), loss modulus (G″), and complex viscosity (η*) of the composites at low frequency. The Cole-Cole plots confirm that the surface modification of CF leads to a better interaction between the CF and PET, and then decreases the heterogeneity of the polymeric systems, which is confirmed by the SEM observation on the tensile fracture surface of the composites. Non-isothermal crystallization analysis shows that the CF or PMMA-g-CF could serve as nucleation agent to accelerate the crystallization rate of the composites, and the effect of PMMA-g-CF is stronger than that of CF. The result is further confirmed by the analysis of the crystallization activation energy for all composites calculated by the Flynn-Wall-Ozawa method. Moreover, the tensile and impact strength and the thermal stability of the composites are improved by CF, while the incorporation of PMMA-g-CF further enhances the tensile and impact strength and thermal stability.

Continuous carbon nanotube synthesis on charged carbon fibers

Carbon nanotube grafted carbon fibers (CNT-g-CFs) were prepared continuously, spool to spool, via thermal CVD. The application of an in-situ potential difference (300 V), between the fibers and a cylindrical graphite foil counter electrode, enhanced the growth, producing a uniform coverage of carbon nanotubes with diameter ca. 10 nm and length ca. 125 nm. Single fiber tensile tests show that this approach avoids the significant reduction of the underlying carbon fiber strengths, which is usually associated with CVD grafting processes. Single fiber fragmentation tests in epoxy, with in-situ video fragment detection, demonstrated that the CNT-g-CFs have the highest interfacial shear strength reported for such systems (101 ± 5 MPa), comparable to state-of-the-art sizing controls (103 ± 8 MPa). Single fiber pull-out data show similar trends. The short length of the grafted CNTs is particularly attractive for retaining the volume fraction of the primary fibers in composite applications. The results are compared with a short review of the interfacial data available for related systems.

Effect of carbon nanotube grafting on the wettability and average mechanical properties of carbon fiber/polymer multiscale composites

An experimental investigation is performed to relate the wetting behavior of unsized and carbon nanotube (CNT) grafted carbon fibers to the average mechanical properties of unsized and CNT grafted carbon fiber/polymer multiscale composites. Contact angle measurements and single fiber pull out tests show that the choice of polymer matrix plays a crucial role in determining whether the incorporation of CNTs on the fiber surface enhances or degrades the wettability and hence average mechanical properties of carbon fiber/polymer composites. CNT grafting leads to a significant improvement in interfacial shear strength as well as flexural and tensile response of carbon fiber/polymer composites with the epoxy resin. However, incorporation of CNTs on fiber surface has no significant effect on the average mechanical properties of carbon fiber/polyester composites. Moreover, it is recorded that the relative enhancement in properties after CNT grafting depends on the fiber orientation in CNT grafted carbon fiber/epoxy composites. POLYM. COMPOS., 39:E1184–E1195, 2018. © 2018 Society of Plastics Engineers

Applying a potential difference to minimise damage to carbon fibres during carbon nanotube grafting by chemical vapour deposition

The application of an in situ potential difference between carbon fibres and a graphite foil counter electrode (300 V, generating an electric field ca 0.3–0.7 V μm−1), during the chemical vapour deposition synthesis of carbon nanotube (CNT) grafted carbon fibres, significantly improves the uniformity of growth without reducing the tensile properties of the underlying carbon fibres. Grafted CNTs with diameters 55 nm ± 36 nm and lengths around 10 μm were well attached to the carbon fibre surface, and were grown without the requirement for protective barrier coatings. The grafted CNTs increased the surface area to 185 m2 g−1 compared to the as-received sized carbon fibre 0.24 m2 g−1. The approach is not restricted to batch systems and has the potential to improve CNT grafted carbon fibre production for continuous processing.

Improvement of interfacial properties in bismaleimide composites using functionalized graphene oxide grafted carbon fiber

A hierarchical reinforcement, which was used to improve the interfacial properties of bismaleimide (BMI) composites, was prepared by grafting functionalized graphene oxide (GO) onto a carbon fiber surface. The GO and carbon fibers were first functionalized separately to create interactional functional groups on their surfaces. The grafting process was then realized by an amidation reaction of the amine and acyl chloride function groups formed on GO and carbon fibers, respectively. The surface groups of functionalized GO and carbon fibers were identified by an X‐ray photoelectron spectroscopy (XPS). The resulting reinforcement was further characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and dynamic contact angle analysis. Experimental results showed that the functionalized GO were successfully grafted onto the carbon fibers surfaces and significantly increased the surface energy of carbon fibers. The study also indicated that the prepared hierarchical reinforcement could significantly improve the interfacial adhesion of resulting BMI composite. POLYM. ENG. SCI., 58:886–893, 2018. © 2017 Society of Plastics Engineers

Wear resistance of poly(2-methacryloyloxyethyl phosphorylcholine)-grafted carbon fiber reinforced poly(ether ether ketone) liners against metal and ceramic femoral heads.

Younger, active patients who undergo total hip arthroplasty (THA) have increasing needs for wider range of motion and improved stability of the joint. Therefore, bearing materials having not only higher wear resistance but also mechanical strength are required. Carbon fiber-reinforced poly(ether ether ketone) (CFR-PEEK) is known as a super engineering plastic that has great mechanical strength. In this study, we focused on poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC)-grafted CFR-PEEK and investigated the effects of PMPC grafting and the femoral heads materials on the wear properties of CFR-PEEK liners. Compared with untreated CFR-PEEK, the PMPC-grafted CFR-PEEK surface revealed higher wettability and lower friction properties under aqueous circumstances. In the hip simulator wear test, wear particles generated from the PMPC-grafted CFR-PEEK liners were fewer than those of the untreated CFR-PEEK liners. There were no significant differences in the size and the morphology of the wear particles between the differences of PMPC-grafting and the counter femoral heads. Zirconia-toughened alumina (ZTA) femoral heads had significantly smoother surfaces compared to cobalt-chromium-molybdenum alloy femoral heads after the hip simulator test. Thus, we conclude that the bearing combination of the PMPC-grafted CFR-PEEK liner and ZTA head is expected to be a lifelong bearing interface in THA. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1028-1037, 2018.

Effects of grafting low-generation poly(amido amine) onto carbon fiber surface by in situ polymerization on the mechanical properties of fiber composites

Low-generation poly(amido amine) (PAMAM)-grafted carbon fibers (CFs) emerged as a new reinforcement for improving the mechanical properties of fiber composites. In this work, hybrid reinforcement, which could greatly enhance the surface roughness and wettability of CF, was prepared via growing PAMAM onto fiber surface by in situ polymerization.The modified surface morphology and chemical composition were investigated by scanning electron microscopy, atomic force microscopy, dynamic contact angle analysis test, and X-ray photoelectron spectroscopy. Experimental results indicated PAMAM dendrimers grown on the CF significantly enhanced interfacial properties of the resulting composites. In addition, compared with the desized CF composites, the CF grafted with PAMAM composites exhibited 34.65% enhancement in the interfacial shear strength.

Enhanced mechanical properties of multiscale carbon fiber/epoxy composites by fiber surface treatment with graphene oxide/polyhedral oligomeric silsesquioxane

Graphene oxide (GO) and polyhedral oligomeric silsesquioxane (POSS) grafted carbon fiber (CF) was demonstrated to reinforce the mechanical properties of fiber composites. Such a fiber composite was prepared by grafting POSS onto the CF surface using GO as the linkage. The presence of GO linkage and POSS could significantly enhance both the area and wettability of fiber surface, leading to an increase in the interfacial strength between fibers and resin. Compared with the desized CF composites, the grafted CF composites fabricated by compression molding method exhibited 53.05% enhancement in the interlaminar shear strength. The changed surface morphology, surface composition and surface energy were supposed to be related with the interfacial performance of unidirectional composites, as revealed by scanning electron microscopy, atomic force microscope, dynamic contact angle test and X-ray photoelectron microscopy charaterizations.

Directly grafting graphene oxide onto carbon fiber and the effect on the mechanical properties of carbon fiber composites

Amino-functionalized graphene oxide (GO-NH2) was directly grafted onto carbon fiber surface by covalent bonding in an attempt to improve the mechanical properties of carbon fiber composites. The effect of surface modification on the properties of carbon fiber and the resulting carbon fiber composites was investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and interfacial shear strength (IFSS). As revealed by Fourier transform infrared spectroscopy (FT-IR), GO-NH2 was successfully grafted on the carbon fiber surface. From dynamic contact angle analysis (DCAT) and XPS values, such GO-NH2 grafted carbon fiber exhibited significant improvements in surface energy and functional groups of the carbon fiber surface, which lead to an increase of 36.4% in the IFSS of its composites. Such hierarchical reinforcement shows great potential for enhancing interfacial properties in carbon fiber-reinforced composites.