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.     

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.     

The effect of surface treatment of carbon fiber on the flexural property of thermoplastic polyimide composite

Rare earth solution (RES) surface modification and air-oxidation methods were used to improve the interfacial adhesion of the carbon fiber reinforced polyimide (CF/PI) composite. The flexural property of the PI composites reinforced by the carbon fibers treated with different surface modification methods was comparatively investigated. Results showed that the flexural strength of CF/PI composite was improved after RES treatment. The improvement of impact and flexural property of the CF/PI composite was mainly due to the improvement in interfacial adhesion after RES treatment. X-ray photoelectron spectroscopy (XPS) study of carbon fiber surface showed that the oxygen concentration was obviously increased after RES treatment. The increase in the amount of organic functional groups increased the interfacial adhesion between CF and PI matrix.     

A Study on the Mechanical and Tribological Properties of Carbon Fabric/PTFE Composites

Carbon fabric reinforced polytetrafluoroethylene (PTFE) composites with different PTFE content, viz. 30, 40, 50, 60, and 70 vol%, were fabricated by a dispersion impregnation technique followed by a hot-press process. The composites were evaluated for their mechanical and tribological properties. The tribological tests were conducted on a friction and wear tester with a ring-on-block arrangement. The mechanical properties were also tested and their relationship with tribological properties was analyzed. The worn surface and wear debris were analyzed by a scanning electron microscope (SEM) to study the wear mechanism. It was found that the resin content had a great influence on both the mechanical properties and the tribological properties, and the tribological properties were correlated with the mechanical properties. The composite with 50 vol% PTFE showed promising tribological behaviors under the selected test conditions.     

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     

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.     

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.     

The friction and wear properties of divinylbenzene-grafted UHMWPE fiber-filled serpentine/PTFE composite

Divinylbenzene-grafted Ultra-high-molecular-weight polyethylene (UHMWPE) fibers were used to reinforce the Polytetrafluoroethylene (PTFE) composite and the friction and wear behaviors of UHMWPE/PTFE composite were studied on the ring-block machine under vacuum condition. The worn surfaces of specimens were investigated using scanning electron microscopy and energy dispersive spectroscopy (EDS). The results showed that the friction coefficient and temperature of UHMWPE/PTFE composites with surface-treated UHMWPE fiber were apparently lower than that with untreated one. In conclusion, the surface treatment favored the improvement of the higher interface strength and so had good effect on improving the tribological properties of the composites. The dominant wear mechanisms were adhesion wear, plastic deformation, brittle facture, and spalling. The EDS analysis of the worn surface indicated the trend of the tribochemical reaction of the Fe related to the transfer of the PTFE.     

The Mechanical and Tribological Properties of Aramid (Twaron) Fabric/Polytetrafluoroethylene Composites

A series of composites with Twaron fabric as reinforcement and polytetrafluoroethylene (PTFE) as matrix were fabricated with various contents of PTFE, viz. 30, 40, 50, 60, and 70 vol%. The Rockwell hardness and tensile strength of the composites were tested according to the corresponding standards. The composites were also evaluated for their tribological behaviors on an MPX-2000A friction and wear tester. The worn surface and wear debris of the composites were observed by scanning electron microscopy (SEM) and the mechanism is discussed. The PTFE content in the composites had a great influence on both the mechanical and tribological properties. The composite with 40 vol% PTFE provided the proper wetting of the fibers and the best load transfer efficiency and, hence, showed the best mechanical properties and tribological behaviors.     

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.     

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.     

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.     

The gamma irradiation of PBO fiber on the mechanical and tribological properties of PTFE composites

The mechanical and tribological behavior of gamma irradiated poly(p-phenylene benzobisoxazole) (PBO) fiber filled polytetrafluoroethylene (PTFE) composites was investigated. The gamma irradiated PBO fiber composite had the highest inter-laminar shear strength value of all the combinations because its higher bond strength may have hindered a large fiber/matrix debonding. X-ray photoelectron spectroscopy results indicate that the contents of polar groups on the surface of gamma irradiated PBO fiber increase compared to PBO fiber. The wear tests were conducted on a ring-on-block apparatus using composite block against polished metal counterparts under dry sliding conditions. It can also be found that gamma irradiation treatment was helpful to the improvement of the anti-wear ability of the PTFE composite which was related to the abrasive wear mechanism.     

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.     

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.     

Friction and wear properties of PA6 filled PTFE composites under oil lubrication

Blending polytetrafluorothylene (PTFE) to PA6 at different compositions was produced in a corotating twin-screw extruder where, PTFE acts as the polymer matrix and PA6 as the dispersed phase. The tribological properties of PTFE composites filled with PA6 under oil lubrication were investigated. The worn surface morphologies of neat PTFE and its composites were examined by scanning electron microscopy (SEM) and the wear mechanisms were discussed. The presence of PA6 particles dispersed in the PTFE continuous phase exhibited superior tribological characteristics to unfilled PTFE. The optimum wear reduction was obtained when the content of PA6 is 30 vol%.     

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.     

Development and characterization of alkali treated abaca fiber reinforced friction composites

Abaca fibers show tremendous potential as reinforcing components in composite materials. The purpose of this study is to investigate the effect of abaca fiber content on physical, mechanical and tribological properties of abaca fiber reinforced friction composites. The friction composites were fabricated by a compression molder and investigated using a friction test machine. The experiment results show that surface treatment of abaca fibers could improve the mechanical properties of abaca fiber and interface bonding strength of the abaca fiber and composite matrix. Density of friction composites decreased with the increasing of abaca fiber content (0 wt%–4 wt%). The different content of abaca fibers had less effect on hardness of specimens, whereas large of impact strength. The specimen F3 with 3 wt% abaca fibers had the lowest wear rate and possessed the best wear resistance, followed by specimen F4 with 4 wt% abaca fibers. The worn surface morphologies were observed using the Scanning Electron Microscopy for study the tribological behavior and wear mechanism. The results show that a large amount of secondary contact plateaus presented on the worn surface of specimen F3 which had relatively smooth worn surface.     

Fiber-matrix adhesion mechanism of pitch-based carbon fiber composites

The fiber-matrix adhesion mechanism in high modulus pitch-based carbon fiber-epoxy matrix composites has been studied. The surface morphology and chemistry of the carbon fibers were examined by microscopic (SEM, STM), thermodynamic and spectroscopic (XPS, Raman) techniques. The interlaminar shear strength and transverse tensile strength of the composites made from surface-treated and untreated fibers were also obtained. In the microscopic analysis, there was no difference in the surface roughness between the surface-treated and untreated fibers. In the thermodynamic and spectroscopic analyses, surface treatment of the carbon fibers increased the amount of surface oxygen. The results indicated that the major role of the surface treatment on the carbon fiber-epoxy resin adhesion is not the mechanical interlocking effect by the surface roughness. The formation of surface oxygen-containing functional groups is assumed to account for the increase in fiber-matrix interfacial adhesion.     

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.