Effects of Mixing the Steel and Carbon Fibers on the Friction and Wear Properties of a PMC Friction Material

Friction, fade and wear characteristics of a PMC friction material containing phenolic resin, short carbon fiber, graphite, quartz, barite and steel fiber were investigated through using a small-scale friction testing machine. Four different friction materials with different relative amounts of the carbon fiber and steel fiber were manufactured and tested. Comparing with our previous work which contained only steel fiber as reinforcement, friction characteristics such as fade and recovery and wear resistance were improved significantly by adding a small amount of carbon fiber. For the mixing of carbon and steel fiber, the best frictional and wear behavior was observed with sample containing 4 weight percentage carbon fiber. Worn surface of this specimen was observed by optical microscopy. Results showed that carbon fibers played a significant role in the formation of friction film, which was closely related to the friction performance. The brake pad with Steel fibers in our previous work, showed low friction coefficient and high wear rate. In addition, a friction film was formed on the surface with a relatively poor quality. In contrast, the samples with mixing the steel and carbon fiber generated a stable friction film on the pad surface, which provided excellent friction stability with less wear.     

Study on friction and sliding wear behavior of woven S-glass fiber reinforced vinylester composites manufactured with different comonomers

The effect of variations in sliding velocity and applied normal load on the friction and sliding wear behavior of glass–vinylester composite (G–V) is studied by measuring the weight change and observing the surface features of worn specimens using scanning electron microscopy (SEM). The G–V composites were manufactured with Bi-directional woven S-glass fibers (65 wt%) reinforced with vinylester resin with different comonomers. Friction and wear experiments were carried at ambient conditions on a Pin on disc machine arrangement. The wear in the experiment was determined from the weight loss measured after running against steel disc at sliding velocities of 1, 2, 3, and 4 m/s and applied normal load of 10, 20, 30, and 40 N. The experimental findings show increase in specific wear rate with increase the applied load. Specific wear rate was maximum for the sample A (Styrene as Comonomer), intermediate for sample B (Methyl acrylate as comonomer), and least for sample C (Butyl acrylate as comonomer). It was also observed that increasing normal load and sliding velocity the coefficient of friction decreases. The scanning pictures show features like tendency for the matrix to adhere towards the fiber, debris formation, network of cracks, agglomeration of debris, and broken fibers depending on the load and velocity employed.     

A Comparative Investigation of the Tribological Behavior of Short Fiber Reinforced Polyimide Composites Under Dry Sliding and Water-Lubricated Condition

The friction and wear behavior of high performance polyimide (PI) and its composites reinforced with short cut fibers such as carbon fiber, glass fiber and quartz fiber was comparatively evaluated under dry sliding and water-lubricated condition, aiming at selecting matching materials for the pumps of pure water power transmission. The wear mechanisms of the composites under the two different sliding conditions were also comparatively discussed, based on scanning electron microscopic examination of the worn composite and steel counterpart surfaces. As the results, the PI composites reinforced with carbon fiber have the best mechanical and tribological properties compared with glass fiber and quartz fiber. PI composites sliding against stainless steel register lower friction coefficients and wear rates under water-lubricated condition than under dry sliding though the transfer of PI and its composites was considerably hindered in this case. PI and its composites are characterized by plastic deformation, micro cracking, and spalling under both dry-and water-lubricated sliding. Such plastic deformation, micro cracking, and spalling is significantly abated under water-lubricated condition. The glass and quart2 fibers were easily abraded and broken when sliding against steel in water environment, the broken fibers transferred to the mating metal surface and increase the surface roughness of mating stainless steel. This is probably the cause of the increased wear rate of glass fiber and quartz fiber PI composites in this case.     

Tribological properties of MoS<Subscript>2</Subscript> and carbon fiber reinforced polyimide composites

The tribological properties of carbon fiber reinforced polyimide (PI) composites with different MoS₂ containing sliding against GCr15 steel were comparatively evaluated on an M-2000 model ring-on-block test rig. The wear mechanisms were also comparatively discussed, based on scanning electron microscopic examination of the worn surface of the PI composites and the transfer film formed on the counterpart. It was found that small incorporation of MoS₂ was harmful to the improvement of friction and wear behaviors of carbon fiber reinforced PI composites. However, it was found that the increasing filler of MoS₂ significantly improved the wear resistance and decreased the friction coefficient of carbon fiber reinforced PI composites. It was also found that the tribological properties of MoS₂ and short carbon fiber reinforced PI composites were closely related with the sliding condition such as sliding rate and applied load.     

Friction and wear behavior of carbon fiber reinforced brake materials

A new composite brake material was fabricated with metallic powders, barium sulphate and modified phenolic resin as the matrix and carbon fiber as the reinforced material. The friction, wear and fade characteristics of this composite were determined using a D-MS friction material testing machine. The surface structure of carbon fiber reinforced friction materials was analyzed by scanning electronic microscopy (SEM). Glass fiberreinforced and asbestos fiber-reinforced composites with the same matrix were also fabricated for comparison. The carbon fiber-reinforced friction materials (CFRFM) shows lower wear rate than those of glass fiber- and asbestos fiber-reinforced composites in the temperature range of 100°C-300°C. It is interesting that the frictional coefficient of the carbon fiber-reinforced friction materials increases as frictional temperature increases from 100°C to 300°C, while the frictional coefficients of the other two composites decrease during the increasing temperatures. Based on the SEM observation, the wear mechanism of CFRFM at low temperatures included fiber thinning and pull-out. At high temperature, the phenolic matrix was degraded and more pull-out enhanced fiber was demonstrated. The properties of carbon fiber may be the main reason that the CFRFM possess excellent tribological performances.     

Effect of Short Fibre Reinforcement on the Friction and Wear Behaviour of Nylon 66

Use of thermoplastic composite material for load bearing components is increasing due to economical processing of complicated shapes in large quantities. Addition of fibre improves the strength and modulus of composites. Although the tribo-behaviour of thermoplastic composites were investigated, the friction and wear mechanisms are not yet fully understood. Friction and wear behaviour of injection unfilled Nylon 66, glass fibre reinforced Nylon 66 and carbon fibre reinforced Nylon 66 is investigated under dry sliding conditions. Tests were conducted at different normal loads and sliding velocities at room temperature. Coefficient of friction, wear loss and heat generation during the wear tests were quantified. Presence of fibre affects coefficient of friction and wear resistance of Nylon 66 matrix composites. The formation and stability of the transfer films affects the wear resistance. The rise in temperature during sliding was also calculated and also measured. The contact temperature rise is influenced by the composition which in turn influences the fibre adhesion and thereby the wear resistance. Glass fibre reinforced Nylon exhibited the lowest wear rate among the materials investigated. Both adhesive and abrasive wear mechanisms were observed in polymer matrix composites.     

滑移速度对铜石墨滑板材料摩擦性能的影响

为研究铜石墨滑板材料在不同滑移速度下的摩擦性能,从摩擦机理角度建立了滑板材料摩擦性能与滑移速度关系的理论模型,假定材料摩擦性能和滑移速度之间存在抛物线型关系,即存在一个最佳滑移速度区域,当滑移速度接近或处于此区域时,摩擦接触面石墨层的形成量和消耗量趋于平衡,材料表面形成了完整的石墨层,铜石墨滑板材料具有稳定的摩擦性能.在不同滑移速度下进行摩擦实验,采用扫描电镜分析磨损表面形貌,结果证明了理论模型的正确性.     

Tribological behaviour and acoustic emissions of alumina, silicon nitride and SAE52100 under dry sliding

The friction, wear and acoustic emission behaviour of various combinations of alumina, silicon nitride, and SAE52100 steel, operating under dry sliding conditions, was investigated. A designed ball-on-flat-disc type of tribometer was used to conduct these experiments. This apparatus, equipped with a force sensor, using silicon strain gauges, measured simultaneously the normal load and friction force. Both forces were used to determine the real-time value of the dynamic coefficient of friction. The AE signal arising from the interaction of the surfaces in dynamic contact was also detected and a data acquisition system was used to gather this signal as well as the outputs from the force sensor, at high frequency. The effects of test duration, sliding speed and normal load on the above mentioned tribological parameters were evaluated. The interest of this study further extended to assess the correlations that may exist between the integrated rms acoustic signal (AE) and the friction mechanisms, wear volume, friction work as well as the material removal power. Under the specific conditions of the present experiments, no consistent relation was found between the variations of AE and corresponding dynamic coefficient of friction (COF) as function of time. The variation of COF and wear rate, obtained considering a fixed total sliding distance of 500 m, as function of a range of sliding speed (0.05–2.5 m/s) and normal load (5–40 N) are presented. It was found that the test duration has an important impact on wear results of the experiments conducted at different sliding speeds and fixed travelling distance. More expected behaviour was observed when the relationships between the AE and wear volume, friction work, and material removal power were investigated considering the data obtained at different loadings and fixed sliding speed. Some models representing interesting relationships which could be used for predicting tribological properties in the case of practical applications, similar to the tribo-systems investigated in this study, are proposed.     

Differences in dry sliding wear behavior between HVAF-sprayed amorphous steel and crystalline stainless steel coatings

Dry sliding wear behavior of amorphous steel coating(ASC) and crystalline stainless steel coating(SSC)manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of friction(COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation.Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness(H), reduced Young's modulus(E_r), and ratios of H/Erand H~3/E_r~2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.     

空心微珠-碳纤维共混改性聚酰亚胺复合材料的摩擦学性能

通过模压成型制备了碳纤维与空心微珠共混改性的聚酰亚胺复合材料, 采用MRH-3型摩擦磨损试验机研究了空心微珠含量、滑动速度及载荷对复合材料摩擦学性能的影响, 并对其磨损形貌及机制进行了分析。结果表明: 空心微珠-碳纤维/聚酰亚胺复合材料摩擦学性能优于其单独填充的聚酰亚胺基复合材料; 空心微珠含量对共混改性的复合材料摩擦系数影响不大, 但其磨损率随着空心微珠含量的增加先减小后增大; 15%空心微珠-10%碳纤维(质量分数)共混增强的复合材料的减摩耐磨性能最佳; 随着滑动速度提高, 空心微珠-碳纤维/聚酰亚胺复合材料的摩擦系数下降, 磨损率增大; 空心微珠-碳纤维/聚酰亚胺复合材料摩擦系数随着载荷增加先下降后上升, 而磨损率则随着载荷增加而增大; 空心微珠-碳纤维/聚酰亚胺的主要磨损机制在较低载荷时为磨粒磨损, 在较高载荷时为粘着磨损和磨粒磨损。     

Comparative study of wear performance of particulate and fiber-reinforced nano-ZnO/ultra-high molecular weight polyethylene hybrid composites using response surface methodology

The effects of two types of filler reinforcements i.e. particulate (talc particles) and fiber (Glass Fiber (GF)) as secondary reinforcements in ultra-high molecular weight polyethylene (UHMWPE)-based composites on the wear and friction properties were discussed in this paper. These UHMWPE hybrid composites were fabricated by the addition of 10 wt% of talc and glass fiber at a fixed nano-ZnO loading of 10 wt% using a hot compression moulding technique. The wear and friction properties of these hybrid composites were investigated using a pin-on-disc tester with different operating conditions of applied loads, sliding speeds and sliding distances based on response surface Box–Behnken design. Response Surface Methodology (RSM) was applied to model the effects of various variables of applied load, sliding speed and distance on the wear volume loss and average coefficient of friction (COF) of UHMWPE hybrid composites. The mathematical regression models of the wear volume and average COF were derived from the analysis of variance (ANOVA). Optimization of the independent variables to minimize the wear and friction responses of both UHMWPE composites was estimated using RSM. The mathematical models showed that applied load, sliding speed and distance have significant effects on the wear and friction properties of both UHMWPE composites in the tested range of variables. The most significant, in order of the variables that affect the volume loss and friction of UHMWPE composites is load, followed by sliding distance and speed. In addition, the combined effects of load and distance indicate the highest significance on volume loss and average COF for both UHMWPE hybrid composites as compared to other variable interactions. GF/ZnO/UHMWPE exhibited better wear performance compared to talc/ZnO/UHMWPE hybrid composites. The severity of worn surfaces of the GF/ZnO/UHMWPE was less than that of talc/ZnO/UHMWPE. The GF/ZnO/UHMWPE produced transfer films that were more uniform and had better coverage compared to talc/ZnO/UHMWPE.     

Structures formed during the friction of a metal-ceramic composite on steel under high-velocity sliding conditions

We present the results of investigations of the structures of friction surfaces and tribological characteristics of a ceramic-metal (WC-steel 110G13) composite upon dry friction on steel in a rod-on-disk configuration in a range of sliding velocities from 0.65 to 40 m/s at a pressure of 2 MPa. The region of catastrophic wear in this system is observed at 23–30 m/s and is followed by a region of steady-state wear at a sliding velocity above 30 m/s. The sharp increase in the rate of wear at 23–30 m/s is related to a change in the wear mechanism. It is established that three layers with different structures and properties are formed in the WC-steel 110G13 composite near the friction surface.     

Comparison of friction and wear performances of brake materials containing different amounts of ZrSiO4 dry sliding against SiCp reinforced Al matrix composites

Low friction levels for brake materials dry sliding against Al matrix composites (Al-MMCs) were observed. Al matrix composites reinforced with 30 vol.% SiC_p (34 μm) were used first to fabricate a new brake drum in place of the conventional cast iron brake drum for a Chase Machine. Experimental studies on the brake materials differing in amounts of zirconium silicate (0 wt%, 4 wt%, 8 wt%, and 12 wt% ZrSiO₄) dry sliding against the Al-MMCs drum were performed on the Chase Machine in order to examine their effects on friction and wear performances. The test procedures include friction fade and recovery, load and speed sensitivities at 177 °C and 316 °C, and wear. Experimental results show that the brake material containing 8 wt% ZrSiO₄ had the best wear resistance and higher friction level. The brake material containing 12 wt% ZrSiO₄ had the highest friction level, but wear increased rapidly. The deterioration of the latter wear suggests that this brake material is unreliable in commercial applications.     

Friction and wear behavior of carbon nanotubes reinforced polyamide 6 composites under dry sliding and water lubricated condition

The friction and wear behavior of carbon nanotube reinforced polyamide 6 (PA6/CNT) composites under dry sliding and water lubricated condition was comparatively investigated using a pin-on-disc wear tester at different normal loads. The morphologies of the worn surfaces and counterfaces of the composites were also observed with scanning electron microscopy (SEM). The results showed that CNTs could improve the wear resistance and reduce the friction coefficient of PA6 considerably under both sliding conditions, due to the effective reinforcing and self-lubricating effects of CNTs on the PA6 matrix. The composites exhibited lower friction coefficient and higher wear rate under water lubricated condition than under dry sliding. Although the cooling and boundary lubrication effect of the water contributed to reduce the friction coefficient of the composites, the adsorbed water lowered the strength of the composites and also inhibited the formation of transfer layers on the counterfaces resulting in less wear resistance. With the increasing normal loads, the friction coefficient of the composites increased under the dry sliding and decreased under the water lubricated condition, owing to inconsistent influences of shear strength and real contact areas. The specific wear rate of the composites increased under both sliding conditions.     

Dry rolling and sliding friction and wear of organophilic layered silicate/hydrogenated nitrile rubber nanocomposite

Dry rolling and sliding tribological behaviors of hydrogenated nitrile rubber (HNBR) and its compound, containing 10 parts per hundred rubber (phr) organophilic layered silicates (OLS), were evaluated. As OLS modifier a quaternary amine with hydroxyl and double bonds was selected to support the intercalation/exfoliation by triggering possible interactions with HNBR. According to X-ray diffraction results the OLS was intercalated. Network-related parameters were deduced from dynamic-mechanical thermal analysis (DMTA). The tribological parameters, i.e., coefficient of friction (COF) and specific wear rate (W _s), were determined in various home-made test configurations. The OLS reinforcement of HNBR affected the COF and improved the resistance to rolling and sliding wear (except fretting) compared to the pure HNBR. The worn surfaces of the rubber compounds were inspected in scanning electron microscope (SEM) and the dominant wear mechanisms concluded.     

PTFE微粉/CF改性PEEK复合材料的摩擦磨损性能

为解决核电水循环系统中鼓型旋转滤网驱动装置的耐腐蚀问题,本文研究了碳纤维和聚四氟乙烯微粉改性的聚醚醚酮复合材料在干摩擦、水润滑和油润滑条件下的摩擦磨损性能.通过机械共混、高温模压的方法,制备了不同质量分数的聚四氟乙烯(PTFE)微粉/碳纤维(CF)/二硫化钼(MoS_2)/聚醚醚酮(PEEK)复合材料.采用拉伸试验机和塑料洛氏硬度计测试其力学性能,采用摩擦磨损试验机测试了复合材料在干摩擦、水润滑和油润滑条件下的摩擦磨损性能,采用扫描电子显微镜对其摩擦表面形貌进行分析.结果表明:复合材料在水润滑和油润滑时摩擦系数及磨痕宽度均较小,但水润滑时摩擦系数波动幅度较大且磨痕宽度略高;复合材料在干摩擦条件下的磨损机制以磨粒磨损为主,伴有疲劳磨损,油润滑时摩擦面可形成连续的润滑膜而保持光滑,水润滑时水流冲刷破坏了摩擦面上固体润滑膜的稳定性;CF质量分数增加时,复合材料的洛氏硬度和压缩强度递增,压缩强度达到164 MPa,PTFE微粉质量分数增加时,复合材料的洛氏硬度和压缩强度递减;CF质量分数增加时,复合材料的干摩擦系数及磨痕宽度下降,PTFE微粉质量分数增加时,复合材料的干摩擦系数下降,达到0.17.     

Mechanical and tribological properties of acrylonitrile–butadiene rubber filled with graphite and carbon black

In this work, acrylonitrile–butadiene rubber (NBR)/expanded graphite (EG)/carbon black (CB) micro- and nanocomposites were prepared by two different methods, and the resulting mechanical and tribological properties were compared with those of NBR/CB composites. Meanwhile, the effects of graphite dispersion and loading content, as well as the applied load and sliding velocity on the tribological behavior of the above composites under dry friction condition were also evaluated. The worn surfaces were analyzed by scanning electron microscopy (SEM) to disclose wear mechanism. As expected, the better the dispersion of graphite, the more remarkable enhancement on tensile and dynamic mechanical properties, and the greater reduction in the coefficient of friction (COF) and specific wear rate (W_s). It was found that a small amount of EG could effectively decrease COF and W_s of NBR/CB composites because of the formation of graphite lubricant films. The COF and W_s of NBR/CB/EG composites show a decreasing trend with a rise in applied load and sliding velocity. NBR/CB/EG nanocomposite always shows a stable wearing process with relatively low COF and W_s. It is thought that well-dispersed graphite nano-sheets were beneficial to the formation of a fine and durable lubricant film.     

一种新型短切碳纤维增强纸基摩擦材料研究

以短切碳纤维为增强纤维,采用湿法工艺研制成功一种新型无石棉纸基摩擦材料,采用TG-DTA热分析方法、定速摩擦试验和惯量摩擦研究了摩擦材料耐热性能、摩擦性能和磨损性能.试验结果表明,新研制的炭纤维增强纸基摩擦材料的起始分解温度和失重速率等耐热性能指标优良,动摩擦系数高达0.136～0.149,且摩擦系数稳定,磨损率低,是一种理想的新型无石棉纸基摩擦材料.     

炭/碳化硅复合材料在高温燃气环境中的铰链传动与摩擦行为

采用化学气相渗透法(CVI)制备了二维炭纤维增强碳化硅(C/SiC)全陶瓷基复合材料铰链试样. 高温燃气风洞实现了铰链试样在1800℃高温氧化气氛中传动与摩擦行为的试验模拟. 基于耦合应力等效模拟系统的开发, 采用摩擦力矩的变化表征材料的传动与摩擦行为. 对比分析了材料在室温与高温下以传动为背景的高载荷、低转速摩擦磨损行为及机理. C/SiC复合材料铰链试样在高温燃气环境中稳定的摩擦力矩和对滑动时间的不敏感, 验证了材料在高温下更稳定、更可靠的高温摩擦性能及热承载能力. 高温下表面生成的氧化反应膜通过应力的重新分布起到有效的保护与润滑作用.     

Friction and wear behavior of three-dimensional braided carbon fiber/epoxy composites under lubricated sliding conditions

The friction and wear characteristics of three-dimensional (3D) braided carbon fiber-epoxy (C_3D/EP) composites under lubricated sliding conditions against a quenched medium-carbon steel counterface were studied. Wear tests were performed under different loads at two velocities. Comparative wear tests under dry conditions were carried out to investigate the influence of lubrication. Tribological properties of the C_3D/EP composites with various fiber loadings and two different fiber-matrix adhesion strengths were assessed. It was found that the lubricated contact promoted lower wear rates and friction coefficients. Compared to dry sliding, the tribological performance of the C_3D/EP composites under lubrication was less dependent on fiber content, fiber-matrix bonding, load, and velocity than dry sliding. The worn surfaces of the C_3D/EP composites were analyzed by scanning electron microscopy (SEM) to explore the relevant mechanisms.