Surface Wettability Of Carbon Fibers Research Articles

Synergetic surface modification of 3D braided carbon fiber-reinforced composites for enhancing mechanical strength

Excellent interfacial bonding contributes to the reduction of internal defects in composites for enhancing the mechanical properties of the 3D braided carbon fiber reinforced composites. In this paper, the effects of plasma and strong acid treatment on the surface morphology, chemical composition, and surface free energy of original carbon fiber braid (CFB) were investigated in detail to reveal the mechanism of synergetic enhancement of surface wettability of carbon fiber by plasma and strong acid. The results showed that the synergetic effect of plasma and strong acid produced significantly improved the resin/fiber interfacial bonding. The interfacial shear strength (IFSS) of the carbon fiber braided reinforced composites (CFBC) treated with the synergetic treatment was 64.6% higher than that of the untreated fiber reinforced composites. The improved interfacial properties increase the polar functional groups on the fiber surface to promote the formation of mechanical interlocking caused by Cassie-Baxter(CB) and Wenzel(WZ) leaps of liquid resin on the fiber surface, and this was verified by molecular dynamics(MD) simulations of carbon fiber-resin interfacial wetting. The simple and effective synergetic reinforcement strategy proposed in this paper can effectively regulate the interfacial bonding and is applicable to the optimal design of original carbon fiber braided reinforced composites.

Pore scale study of heat and mass transfer in ice-containing gas diffusion layer of polymer electrolyte membrane fuel cells

The liquid water transport and ice melting process in gas diffusion layer (GDL) are studied using the enthalpy-based multi-component multiphase flow lattice Boltzmann model. Then the heat and mass transfer process under different inlet heating temperatures, inlet flow velocities, rib-channel width ratios and contact angles of carbon fibers are discussed. The results show that heat convection and heat conduction areas are formed in the GDL, and the increase of the inlet heating temperature promotes ice melting, the heating temperature needs to be high enough to promote the reduction of the mixture content of water and ice. The inlet flow velocity has a great influence on both the ice melting efficiency and the discharge of liquid water. The reduction ratio of melting time from 0.5 m/s to 1.0 m/s is larger than that from 1.0 m/s to 1.5 m/s. The wider rib structure reduces the range of heat conduction region, so it has higher ice melting efficiency. The surface wettability of carbon fibers has no significant effect on ice melting rate in the heat convection area. Overall, the more hydrophilic the surface, the sooner the ice melts, but the more hydrophobic the surface, the more favorable the discharge of liquid water.

The mechanical properties of LDPE composite filled with CF coated by dimethylamine treated TiO2

In order to improve the surface wettability of carbon fiber and enhance its composite interface performance, dimethylamine treated TiO2 was coated on carbon fiber (CF). The surface morphology, surface chemical state, and surface wettability of CF were characterized by SEM, XPS, and TEM tests, and the interlaminar shear strength (ILSS) and cross‐sectional morphology tests were used to test the performance of CF/Low density polyethylene (LDPE) composites. The interface bonding status was analyzed and characterized. The results show that after the surface treatment of CF by dimethylamine treated TiO2, the O/C (atomic ratio) of the surface of CF is increased, and a certain amount of nano‐scale small convex micro‐mechanical structure is given, which improves the surface wetting of CF. The surface of the CF modified by the TiO2 is rough; the contact area between modified CF and LDPE increases.

Interfacial Improvement of Carbon Fiber/Epoxy Composites by Incorporating Superior and Versatile Multiscale Gradient Modulus Intermediate Layer with Rigid-flexible Hierarchical Structure

In order to enhance the interfacial adhesion of carbon fiber (CF) and polymer matrix, a multiscale gradient modulus intermediate layer with rigid-flexible (GO-PA) hierarchical structure was designed and fabricated between CFs and matrix by a facile and businesslike strategy. The polarity, roughness and wettability of CFs surface as well as the thickness of intermediate layer in composite have been significantly increased after rigid-flexible hierarchical structure was constructed. The IFSS, ILSS, compression and impact toughness manifested that the hierarchical structure could bring about a fantastic improvement (76.8%, 46.4%, 40.7% and 37.8%) for the interfacial and mechanical properties than other previous reports. Consequently, the establishment of CF surface with gradient modulus rigid-flexible hierarchical structure via regulation of nanoparticles and polymer array would open a new, viable and promising route to obtaining high-performance composites.

The effect of self-synthesized hydroxyl-terminated hyperbranched polymer interface layer on the properties of carbon fiber reinforced epoxy composites

A simple and green method to functionalize carbon fiber (CF) with hydroxyl-terminated hyperbranched polymer (HTHBP) synthesized directly through one-pot condensation polycondensation between isophorone diisocyanate (IPDI) and tris (hydroxymethyl) aminomethane (TOAM) was reported. The covalent grafting of HTHBP on the CF surface can greatly increase the polar functional groups, roughness and wettability of CF surface, thereby resulting to significant enhancement of interfacial properties of composites. After grafting, the interlaminar shear strength (ILSS), interfacial shear strength (IFSS) and impact strength of CFs/epoxy composites increased from 58.6 to 81.8 MPa, 48.8 to 87.8 MPa and 55.7 to 76.9 kJ·m−2, respectively. Furthermore, this surface functionalization process could remedy the single fiber tensile strength. The interfacial reinforcing mechanism was also revealed by analyzing interfacial microstructure. This research provided a thought that constructing a continuous gradient modulus interphase layer with strong physicochemical interaction and good wettability by a simple and green method, which could reinforce the interfacial performance and have a bright prospect application in high-performance composite.

Graphitic carbon nitride (g-C3N4) interfacially strengthened carbon fiber epoxy composites

In-situ synthesis of C3N4 on the carbon fiber surface was reported for enhancing interfacial properties of carbon fiber reinforced epoxy resin composite. The formed C3N4 on the carbon fiber surface can greatly increase the roughness, polar functional groups and wettability of carbon fiber surface, thereby leading to significant enhancement of interfacial properties of composites. After modification, interlaminar shear strength (ILSS) and interfacial shear strength (IFSS) of carbon fibers composites are increased from 44.3 to 60.7 MPa and from 43.1 to 75.9 MPa, respectively. Moreover, the surface free energy of carbon fibers is increased by 65.6%. The improved interfacial properties endow carbon fiber composites with better mechanical properties, leading to an increased tensile strength of composites from 1063 to 1279 MPa and total absorbed energy of impact experiment from 1.22 to 1.75 J. Meanwhile, the dynamic mechanical properties and hydrothermal aging resistance are also enhanced significantly. The storage modulus increases from 64.3 to 74.1 GPa. The markedly enhancement of interfacial mechanical properties and mechanical properties could be attributed to the improved resin wettability, enhanced mechanical interlocking and increased chemical bonding induced by the existence of C3N4 on the carbon fiber surface.

Influence of Carbon Nanotube Coatings on Carbon Fiber by Ultrasonically Assisted Electrophoretic Deposition on Its Composite Interfacial Property.

Carbon nanotube (CNT) coatings were utilized to enhance the interfacial properties of carbon fiber (CF)/epoxy(EP) composites by ultrasonically assisted electrophoretic deposition (EPD). A characterization of the CF surface properties was done before and after coating (surface chemistry, surface morphologies, and surface energy). The result shows that oxygenated groups concentrations of the CF surfaces experienced significant increases from 12.11% to 24.78%. Moreover, the uniform and homogeneous CNT films were tightly attached on the surface of CF, and the surface wettability of CF is significant improved by enhanced surface free energy when introduced ultrasonic during the EPD process. In addition, the interlaminar shear strength (ILSS) and water absorption of CF/EP composite were measured. Scanning electron microscopy (SEM) revealed that the fracture mechanisms of the new interface layer formed by depositing CNTs on the CF surface contributed to the enhancement of the mechanical performance of the epoxy. This means that the efficient method to improve interfacial performance of composites has shown great commercial application potential.

Interfacial Microstructure and Enhanced Mechanical Properties of Carbon Fiber Composites Caused by Growing Generation 1-4 Dendritic Poly(amidoamine) on a Fiber Surface.

In an attempt to improve the mechanical properties of carbon fiber composites, propagation of poly(amidoamine) (PAMAM) dendrimers by in situ polymerization on a carbon fiber surface was performed. During polymerization processes, PAMAM was grafted on carbon fiber by repeated Michael addition and amidation reactions. The changes in surface microstructure and the chemical composition of carbon fibers before and after modification were investigated by atomic force microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. All the results indicated that PAMAM was successfully grown on the carbon fiber surface. Such propagation could significantly increase the surface roughness and introduce sufficient polar groups onto the carbon fiber surface, enhancing the surface wettability of carbon fiber. The fractured surface of carbon fiber-reinforced composites showed a great enhancement of interfacial adhesion. Compared with those of desized fiber composites, the interlaminar shear strength and interfacial shear strength of PAMAM/fiber-reinforced composites showed increases of 55.49 and 110.94%, respectively.

Preparation of Graphene Oxide Coatings onto Carbon Fibers by Electrophoretic Deposition for Enhancing Interfacial Strength in Carbon Fiber Composites

Graphene oxide (GO) were utilized to improve the interfacial performance of carbon fiber (CF) and epoxy resin. An effective way to prepare graphene oxide/carbon fiber hybrid fiber was proposed by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition process. A characterization of the fiber surface properties was done before and after coating (surface morphologies, surface chemistry, and surface energy). Results showed that a uniform and thick graphene oxide films were tightly attached on the surface of carbon fiber. Moreover, surface wettability of carbon fibers to epoxy resin is significant improved by enhanced surface free energy due to the deposition of GO. Meanwhile, the introduction of GO in the carbon fiber/epoxy resin composites results in a 55.6% enhancement in the interlaminar shear strength, measured by short beam shear tests. Such a fabrication process is simple and effective, without complex chemical reactions and long processing time, and can be a continuous one for industrial scale.

Influence of carbon nanotubes coatings onto carbon fiber by oxidative treatments combined with electrophoretic deposition on interfacial properties of carbon fiber composite

To improve the interfacial performance of carbon fiber (CF) and epoxy resin, carbon nanotubes (CNTs) coatings were utilized to achieve this purpose through coating onto CF by the treatment with hydrogen peroxide and concentrated nitric acid combined with electrophoretic deposition (EPD) process. The influence of electrophoretically deposited CNTs coatings on the surface properties of CFs were investigated by Fourier transform infrared spectrometer, atomic force microscopy, scanning electron microscopy and dynamic contact angle analysis. The results indicated that the deposition of carbon nanotubes introduced some polar groups to carbon fiber surfaces, enhanced surface roughness and changed 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 CNTs. The thickness and density of the coatings increases with the introduction of pretreatment of the CF during the EPD process. Short beam shear test was performed to examine the effect of carbon fiber functionalization on mechanical properties of the carbon fiber/epoxy resin composites. The interfacial adhesion of CNTs/CF reinforced epoxy composites showed obvious enhancement of interlaminar shear strength by 60.2% and scanning electron microscope photographs showed that the failure mode of composites was changed after the carbon fibers were coated with CNTs.

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

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 56.9MPa in interlaminar shear strength confirms the remarkable improvement in the interfacial adhesion strength of the composites.

The role of grafting force and surface wettability in interfacial enhancement of carbon nanotube/carbon fiber hierarchical composites

The grafting force of carbon nanotube (CNT) on carbon fiber (CF) and the wettability of CF surface were experimentally studied, where hierarchical CNT/CF reinforcement was prepared using chemical vapor deposition (CVD). Then, their effects on interfacial improvement were experimentally and theoretically investigated. The results show that the CNT/CF grafting force is so strong, more than 5μN, and CNT/CF attachment can sustain the fracture of the CNTs. This is expected to be contributed to the improvement of interfacial properties. However, the deposited catalyst deteriorates the wettability, which could seriously degrade the interfacial properties. As a result, experimental results from the micro-droplet test show that there is only a 30% increase in the interfacial shear strength of hierarchical CNT/CF reinforced composite comparing with that of as-received CF reinforced composite. An analytical model was developed to predict the effects of CNT/CF grafting force on interfacial improvement, and the predicted results are in agreement with the experimental one.

Surface analysis of plasma grafted carbon fiber

The surface characteristics of carbon fibers were studied by X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and wetting measurements. The surface of carbon fiber was modified by means of plasma graft silsesquioxane. The oxygen/carbon and silicon/carbon ratio increased rapidly after treatments. Fitting the C 1s, O 1s, and Si 2p spectra demonstrated that new photopeaks were emerged, which were indicated C–Si, Si–O groups, respectively. The degree of surface roughness and the wettability of carbon fiber surface were both increased by plasma graft silsesquioxane. The results may shed some light on the design of the appropriate surface structure, which could react with resin, and the manufacture of the carbon fiber reinforced composites.

Control of interfacial adhesion in continuous carbon and kevlar fiber reinforced polymer composites

Carbon fiber surfaces were treated by cold plasmas of oxygen, nitrogen, argon, ammonia, and propylene. A two-component bismaleimide, an epoxy, and a model thermoplastic resin polypropylene were used as the matrices for composites. The effectiveness of various plasmas in improving the interfacial adhesion between carbon fibers and matrix resins was demonstrated. Predominant adhesion promotion mechanisms as influenced by various plasma treatments were determined. Oxygen and argon plasmas were found to promote mechanical keying by increasing the level of fiber surface roughness and porosity. The wettability of carbon fiber surface by the matrix resin was also enhanced by oxygen plasmas and argon plasmas (to a lesser extent), as evidenced by the increased total surface energies and their polar components. These surface energy increases are mainly due to the various oxygen-containing functional groups observed on the oxygen plasma-treated surface. For the cases of ammonia and combined ammonia/argon plasma treatments, possible chemical bonding between bismaleimide and the plasma-deposited amine groups is one important promoter of interfacial bonding. In these cases increased wettability was also observed. Ammonia and ammonia/argon plasmas appear to be the more appropriate treatments for carbon-fiber/thermoset resin composites considering that they generally do not induce any appreciable reduction in fiber strength. In contrast, excessively prolonged exposure of carbon fibers to oxygen, nitrogen or argon plasma could lead to a significant reduction in fiber strength. The plasma-polymerized polypropylene deposited on the fiber surface was capable of improving the compatibility and adhesion between the fiber and the polypropylene matrix.