Effect of Carbon Fiber Surface Oxidation on Tribological Properties of PTFE Composite under Oil-Lubricated Conditions

Air-oxidation and ozone surface treatment of carbon fibers (CF) on tribological properties of CF reinforced polytetrafluoroethylene (PTFE) composites under oil-lubricated conditions was investigated. Experimental results revealed that ozone treated CF reinforced PTFE (CF/PTFE) composite had the lowest friction coefficient and wear under various applied loads and sliding speeds compared with untreated and air-oxidated composites. X-ray photoelectron spectroscopy (XPS) study of the carbon fiber surface showed that, after ozone treatment, oxygen concentration was obviously increased, and the amount of oxygen-containing groups on CF surfaces were increased greatly. The increase in the amount of oxygen-containing groups enhanced interfacial adhesion between CF and PTFE matrix, and large scale rubbing-off of PTFE was prevented; therefore, the tribological properties of the composite were improved.     

Friction and wear of rare earths modified carbon fibers filled PTFE composite under dry sliding condition

Carbon fibers (CF) were surface treated with air-oxidation and rare earths (RE), respectively. The friction and wear properties of polytetrafluoroethylene (PTFE) composites filled with differently surface treated carbon fibers, sliding against GCr15 steel under dry sliding condition, were investigated on a block-on-ring M-2000 tribometer. Experimental results revealed that RE treatment largely reduced the friction and wear of CF reinforced PTFE (CF/PTFE) composites. The RE treated composite exhibited the lowest friction and wear under dry sliding. Scanning electron microscopy (SEM) investigation of worn surfaces and transfer films of CF/PTFE composites showed that RE treated CF/PTFE composites had the smoothest worn surface under given load and sliding speed, and a continuous and uniform transfer film formed on the counterface. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that the oxygen concentration was obviously increased after RE treatment, and more carboxyl groups were introduced onto CF surfaces after RE treatment. The increase in the amount of oxygen-containing groups increased the interfacial adhesion between CF and PTFE matrix, and accordingly increased the tribological properties of the composite.     

The effect of interphase modification on carbon fiber/polyarylacetylene resin composites

Interfacial modification for carbon fiber (CF) reinforced polyarylacetylene (PAA) resin, a kind of non-polar, was investigated. The high carbon phenolic resin was used as coating to treat the surface of CF after oxidation. Atomic force microscopy (AFM) with force modulation mode was used to analyze the interphase of composite. The interlaminar shear strength (ILSS) and mechanical properties of CF/PAA composites were also measured. It was found that the CF/PAA composites treated with oxidation and coating after oxidation had transition area between carbon fiber and PAA resin. The existence of transition area led to the improvement of interfacial performance of composites. Specially, the thickness and stiffness of interphase of composite treated with coating after oxidation were more suitable for CF/PAA composites. Thus, the composite treated with coating after oxidation had the highest value of ILSS and the best mechanical properties.     

Effects of carbon fiber surface treatment on the tribological properties of 2D woven carbon fabric/polyimide composites

Polyacrylonitrile (PAN)-based carbon fabric (CF) was modified with strong HNO₃ oxidation and then introduced into polyimide (PI) composites. The friction and wear properties of the carbon fabric reinforced polyimide composites (CFRP), sliding against GCr15 stainless steel rings, were investigated on an M-2000 model ring-on-block test rig under dry sliding. Experimental results revealed that the carbon fiber surface treatment largely reduced the friction and wear of the CFRP. Compared with the untreated ones, the surface-modified CF can enhance the tribological properties of CFRP efficiently due to the improved adhesion between the CF and the PI matrix. Scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) study of the carbon fiber surface showed that the fiber surface became rougher and the oxygen concentration increased greatly after surface treatment, which improved the adhesion between the fiber and the PI matrix and improved the friction-reduction and anti-wear properties of the CFRP. An erratum to this article can be found at     

Enhanced interfacial adhesion between PMMA and carbon fiber by graphene oxide coating

The purpose of this study is to increase the interfacial properties in PMMA/carbon fiber (PMMA/CF) composites Graphene oxide (GO) and brached polyethyleneimine were coated onto the surface of carbon fiber by layer-by-layer assembly in this work. Compared with the origin PMMA/CF composite, the composites reinforced by PMMA/CF–GO showed significant enhancement in interFacial shear strength (IFSS). The improved fiber–matrix adhesion was proved by fracture morphology observation of scanning electron microscopy and almost unaffected mechanical properties of the fiber itself during the coating process. The optimal assembly time was found to be 10 for enhancing the overall composite mechanical performance.     

Tribological Properties of Surface-Modified Graphene Filled Carbon Fabric/Polyimide Composites

To improve the wear resistance of carbon fabric reinforced polyimide (CF/PI) composite, surface-modified graphene (MG) was synthesized and employed as a filler. The flexural strength, Rockwell hardness and thermal properties of the composites were tested. The composites were also evaluated for their tribological properties in a ring-on-block contact mode under dry sliding conditions. The results showed that the wear rate of MG reinforced CF/PI composites was reduced when compared to unfilled CF/PI composite. It was found that the 1?wt% MG filled CF/PI composites exhibited the optimal tribological properties. The worn surface, wear debris and transfer films were analyzed by scanning electron microscopy (SEM) and optical microscopy (OM) with the results helping to characterize the wear mechanism.     

Quantitative evaluation of interfacial adhesion between fiber and resin in carbon fiber/epoxy composite cured by semiconductor microwave device

Interfacial adhesion between carbon fiber (CF) and epoxy resin in carbon fiber-reinforced epoxy composite, which was prepared by different heating process such as semiconductor microwave (MW) device and conventional electric oven, has been evaluated quantitatively. The interfacial shear strength (IFSS) between CF and epoxy resin, which was an indicator of adhesion on the interface, was measured by a single fiber fragmentation test. The single fiber fragmentation test showed that the IFSSs of the prepared specimens were different by heating methods. In the case of MW process, the curing reaction of epoxy resin on the CF interface would be progressed preferentially due to the selective heating of CF, resulting that the IFSSs of specimens prepared by MW irradiation were increased by enhancing the output power of MW. However, the IFSSs of the specimens were decreased by excessively high output power because the matrix resin on the CF interface was thermally degraded. As results, by optimizing the MW conditions of output power and irradiation time, the IFSS of the sample cured by MW was increased by 21% as compared to oven-heated one. It was found that the interfacial adhesion between CF and epoxy resin would be improved by the MW-assisted curing reaction on the surface of CF.     

Study on the Tribological Properties of Carbon Fabric/Polyimide Composites Filled with SiC Nanoparticles

Carbon fabric reinforced thermoplastic polyimide composites have significant applications in the field of tribology. However, there are relatively few studies that have been focused on the investigation of these materials. In the present study, carbon fabric/polyimide (CF/PI) composites, reinforced further with SiC nanoparticles, were prepared by dip-coating and hot press molding methods. Rockwell hardness and flexural testing of the composites were conducted. The friction and wear behavior of the resulting carbon fabric composites were evaluated in a ring-on-block contact mode under dry sliding condition. The results showed that the SiC nanoparticles significantly improved the hardness and flexural strength when compared to the CF/PI composites without the SiC additions. The CF/PI composites reinforced with 5 vol% SiC nanoparticles demonstrated the most beneficial mechanical and tribological properties compared to the composites with greater and lesser SiC nanoparticles. Scanning electron microscopy (SEM) and optical microscopy (OM) were employed in order to study the mechanism of tribological behavior. A continuous and thin transfer film formed during the friction test of the composites led to a significant improvement of the tribological properties.     

Friction and Wear Behaviors of Surface-Modified Carbon Fabric/Epoxy Resin Composites

Carbon fabric (CF) was pretreated by air-plasma bombardment and then further modified by deposition of polydopamine on the surface of the pretreated CF. Epoxy resin composites reinforced by unmodified or surface-modified carbon fabric were fabricated. The friction and wear behaviors of the resulting composites were evaluated in a ring-on-block contact mode. The flexural strength and Rockwell hardness of the composites were also evaluated. The morphologies of the worn surfaces of the unmodified and modified composites were analyzed by scanning electron microscopy. The surface treatment increased the surface roughness and changed the surface topography of the CF, which contributed to enhancing the interfacial adhesion of the composites and thus improved the mechanical properties and tribo-performance. The friction and wear properties of both the unfilled and filled composites were highly dependent on the load and sliding velocity. Moreover, the results were supplemented with scanning electron micrographs to help understand the possible wear mechanisms.     

The Effect of Triethylene-Tetramine Treatment of Carbon Fibers on Performance of Composites

Amino groups can be introduced to the surface of carbon fibers (CF) by triethylene-tetramine (TETA) treatment. Carbon fibers coated with triethylene-tetramine (TETA) were treated at 400°C for 30 s in an oxidizing furnace. Differential scanning calorimetry studies showed that the surface functional groups of CF reacted with TETA. The changes of the surface composition and structure of CF were tested by X-ray photoelectron spectrometry (XPS). The interfacial interaction between the resulting CF and an epoxy matrix was also characterized by scanning electron microscopy (SEM) and three-point short-beam shear testing. The XPS results indicate that the number of amino groups on the surface of the CF was significantly increased after being treated with TETA. The interlaminar shear strength (ILSS) of TETA-treated CF-reinforced resin composites (CFRP) was increased by 30% compared with untreated ones, and in the treated CF fracture sections, CFRP pores and carbon fiber pullout were seldom observed. The failure of composites reinforced by treated CF shows a cohesive failure effect in the interface layer.     

Lignocellulosic composites with grafted polystyrene interfaces

The effects of surface grafting of a polymer onto lignocellulosic fiber surface and processing methods on both the interfacial interactions and the resulting composite properties of the fiber-reinforced thermoplastic composites were investigated. Chemithermomechanical pulp (CTMP) wood fiber was used as a reinforcement, which has been chemically modified by radical polymer grafting of styrene onto the fiber surfaces. The chemically modified CTMP fiber was then compounded with polystyrene (PS). Two different processing methods, both compression and injection moldings, were performed to prepare the wood-fiber-reinforced composites. Experimental results showed that surface modification of wood fiber leads to an obvious increase in mechanical properties of the fiber-reinforced composites as compared to the untreated fiber composites. The enhancement of mechanical properties is much greater through injection molding compared with compression molding owing to occurrence of orientation, and better mixing and interaction between the fiber and the matrix by injection molding. An improvement in fiber wetting properties and adhesion by the matrix was observed through scanning electron microscopy for the surface grafted fiber reinforced composites. Untreated wood fiber exhibited a smooth surface without adhered polymer, indicating poor adhesion, while polymer attached to the surface was seen on treated cellulose fiber due to the higher fiber-matrix interactions.     

Thermal and Mechanical Properties of Epoxy/Carbon Fiber Composites Reinforced with Multi-walled Carbon Nanotubes

Multi-scale hybrid composite laminates of epoxy/carbon fiber (CF) reinforced with multi-walled carbon nanotubes (MWCNTs) were fabricated in an autoclave. For laminate fabrication, 0.5 wt% of pristine MWCNTs or silane-functionalized MWNCTs (f-MWCNTs) were dispersed into a diglycidyl ether of bisphenol-A epoxy system and applied on the woven carbon fabric. The neat epoxy/CF composite and the MWCNTs-reinforced epoxy/CF hybrid composites were characterized by thermogravimetric analysis (TGA), thermomechanical analysis (TMA), tensile testing, and field emission scanning electron microscopy (FE-SEM). A significant improvement in initial decomposition temperature and glass transition temperature of epoxy/CF composite was observed when reinforced with 0.5 wt% of f-MWCNTs. The coefficient of thermal expansion (CTE), measured by TMA, diminished by 22% compared to the epoxy/CF composite, indicating an improvement in dimensional stability of the hybrid composite. No significant improvement in tensile properties of either MWCNTs/epoxy/CF composites was observed compared to those of the neat epoxy/CF composite.     

Influence of Fiber Surface Treatment on Mechanical Properties of CF/PET Composites

Carbon fiber (CF) / poly (ethylene terephthalate) (PET) composites were prepared with various contents (2–15wt%) of short carbon fibers. To investigate the effect of surface treatment of the CF on the mechanical properties of the composites, three specimens were prepared; those with short carbon fibers (called SCF), short carbon fibers oxidized with nitric acid (called NASCF) and the fibers oxidized with nitric acid and treated with silane coupling agent (called SCSCF). Flexural, tensile and impact tests were performed to observe mechanical behavior of the specimens. The morphology of the specimens was also studied with a scanning electron microscope (SEM). SCSCF composite had better mechanical properties than the other composites with the same content of carbon fibers since the coupling agent resulted in better interfacial adhesion between the fiber and the matrix.     

A Fluoropolymer Coating on Carbon Fibers Improves Their Adhesive Interaction with PTFE Matrix

Carbon fibers were treated in a HF glow discharge in tetrafluoroethylene and octafluorocyclobutane in order to improve their adhesion to poly(tetrafluoroethylene) matrix. As the result of the plasma treatment, a thin (20–140 nm) fluoropolymer coating was deposited onto the fiber surface. The structure of this coating was studied by means of IR spectroscopy, XPS, AFM and SEM techniques. The coating material appeared to be similar to PTFE in its chemical composition but distinguished by branched, partially crosslinked, amorphous structure and included unsaturated chemical bonds. The coating thickness of 70 nm was sufficient to effectively screen the field of molecular forces of the initial substrate, thus, decreasing the surface energy of the fibers and improving their compatibility with the PTFE matrix. The adhesive strength in the PTFE–carbon fiber systems, measured by means of the microbond test, more than doubled upon the plasma treatment (the local interfacial shear strength increased from 10.7 to 29.7 MPa, apparent IFSS from 4.3 to 7.8 MPa), and the interfacial frictional stress increased by 70%. The new composite material consisting of 20% short coated carbon fibers in the PTFE matrix showed better mechanical, thermal and tribological characteristics as compared with the composite reinforced with untreated fibers.     

Enhanced surface free energy of polyimide fibers by alkali treatment and its interfacial adhesion behavior to epoxy resins

In this article, polyimide (PI) fibers were modified by alkali treatment, and PI fiber-reinforced epoxy composites were fabricated. The effects of different alkali treatment times on the surface properties of the PI fibers and the adhesion behaviors of PI fiber/epoxy composites were studied. The surface morphologies, chemical compositions, mechanical properties, and surface free energy of the PI fibers were characterized by atomic force microscopy, X-ray photoelectron spectroscopy, single-fiber tensile strength analysis, and dynamic contact angle analysis, respectively. The results show that alkali treatment plays an important role in the improvement of the surface free energy and the wettability of PI fibers. We also found that, after the 3 min, 30 °C, 20 wt% NaOH solution treatment, the fibers possessed good mechanical properties and surface activities, and the interlaminar shear strength of the composites increased to 64.52 MPa, indicating good interfacial adhesion properties.     

Novel Jute/Polycardanol Biocomposites: Effect of Fiber Surface Treatment on Their Properties

In the present study, novel biocomposites with chopped jute fibers and thermosetting polycardanol were prepared using compression molding technique for the first time. Prior to biocomposite fabrication, jute fiber bundles were surface-treated at various concentrations using 3-glycidoxypropyltrimethoxy silane (GPS) and 3-aminopropyltriethoxy silane (APS), respectively. The interfacial shear strength, flexural properties and thermal properties of jute/polycardanol biocomposites reinforced with untreated and silane-treated jute fibers were investigated by means of single fiber microbonding test, three-point flexural test, dynamic mechanical analysis, thermogravimetric analysis and thermomechanical analysis. Both GPS and APS treatments played a role in improving the interfacial adhesion, reflecting that the organofunctional groups located at the end of silane coupling agents may contribute to linking between jute fibers and a polycardanol resin. As a result, it gave rise to increased interfacial shear strength of the biocomposites. Such interfacial improvement also led to increasing the flexural strength and modulus, storage modulus, thermal stability and thermomechanical stability.     

Influence of interfacial reaction on interfacial performance of carbon fiber and polyarylacetylene resin composites

The influence of interfacial reaction on interfacial performance of carbon fiber/polyarylacetylene resin composites was studied. For this purpose, vinyltrimethoxysilane containing a double bond was grafted onto the carbon fiber surface to react with the triple bond of polyarylacetylene resin. The reaction between polyarylacetylene resin and vinyltrimethoxysilane was proved by reference to the model reaction between phenylacetylene and vinyltrimethoxysilane. Surface chemical analysis by XPS, surface energy determination from the dynamic contact angle, and the interfacial adhesion in composites was evaluated by interfacial shear strength test as well. It was found that vinyltrimethoxysilane, which can react with polyarylacetylene resin, had been grafted onto the carbon fiber surface. Furthermore, because the reaction between polyarylacetylene resin and vinyltrimethoxysilane took place at the interface, the interfacial adhesion in composites was significantly increased, and the improvement of interfacial adhesion was all attributed to the interfacial reaction.     

Fabrication and Flexural Properties of Bagasse Fiber Reinforced Biodegradable Composites

Biodegradable composites made from bagasse fiber and biodegradable resin were fabricated and the flexural properties of the composites investigated in terms of the effects of fiber length, fiber volume fraction, and different alkali treatments of the bagasse fibers. The flexural properties of the composites increased with the increase in fiber length but decreased below the critical fiber length. The flexural properties increased with the increase in fiber volume fraction. The scanning electron microscope (SEM) micrographs showed that compression of the cellulose structure of bagasse fiber after preparation could have caused enhancement in the flexural properties. Furthermore, when comparing the effects of different alkali treatments of the bagasse fibers, maximum improvement in the flexural properties was observed for the 1% NaOH solution treated fiber composites. After alkali treatment, fibrillation occurred and the surface of the treated fibers became finer; this could contribute to improvement in the fiber‐matrix adhesion and result in enhancing the flexural properties.     

Modification of nano-kenaf surface with maleic anhydride grafted polypropylene upon improved mechanical properties of polypropylene composite

The surface of nano-kenaf fiber is modified with maleic anhydride grafted polypropylene (MA-g-PP) and added into PP and the mechanical properties and the flow property of the composite are investigated. The addition of MA-g-PP in nano-kenaf/PP composite increases the tensile strength, the elongation%, and the impact strength (I.S.), while it decreases the flow property (melt flow index) compared to without MA-g-PP composite (nano-kenaf/PP). The scanning electron microscope photograph shows it also increases interfacial adhesion between nano-kenaf and PP matrix. Regardless of MA-g-PP, nano-kenaf fibers shows better adhesion with PP compared to micron-kenaf fibers. Addition of MA-g-PP further improved interfacial adhesion between nano-kenaf surface and PP matrix compared to without MA-g-PP nano-kenaf compound. The addition of MA-g-PP apparently improves the interfacial adhesion between nano-kenaf surface and PP by formation of 3-dimensional network structure.     

Improved mechanical properties of carbon fiber reinforced PTFE composites by growing graphene oxide on carbon fiber surface

The mechanical properties of carbon fiber reinforced polymer composites depend upon fiber-matrix interfacial properties. To improve the mechanical properties of ?bers/PTFE composites without sacri?cing tensile strength of ?bers, graphene oxide (GO) was introduced onto the surface of CFs by chemical vapour deposition (CVD). This hybrid coating increased the wettability and surface roughness of carbon fibers, which led to improved affinity between the carbon fibers and PTFE matrix. The resulting hybrid-coated carbon fiber-reinforced composites showed an enhancement in the short beam strength compared to un-coated carbon fiber composites. Meanwhile, a signi?cant increase of interlaminar shear strength (ILSS), interface shear strength tests (IFSS) and impact property were achieved in the 5-min-modi?ed CFs.