Studies on the friction and wear characteristics of rubber-based friction materials containing carbon and cellulose fibers

The present study was an attempt to examine the effects of carbon and cellulose fibers on the tribological characteristics of rubber-based friction materials (RBFMs). A fiber free RBFM as a reference material and a series of fiber included RBFMs at different volume fractions were prepared by two-roll mill. The friction tests were performed at different sliding velocities and various drum temperatures. The mechanical properties and surface microstructure of friction specimens were also examined. It was revealed that the carbon fiber influences slightly the coefficient of friction (COF) of RBFM but it improves the wear resistance and the fade behavior considerably. It reduces the drum temperature as well. Cellulose fiber though offered high COF but it proved to be destructive from the fade behavior and wear rate point of view due to its weak thermal stability. It was found that the rubber-to-glass transition, which occurred at high sliding velocities, influences the COF, wear rate, and fade behavior of the RBFMs significantly for both fiber free and fiber-containing systems.     

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.     

Surface damage of unidirectional carbon fiber reinforced epoxy composites under reciprocating sliding in ambient air

For many technical applications friction and wear are critical issues. Reinforced polymer-matrix composites are widely used under vibrating contact condition in various automotive and aerospace applications as well as in structural engineering. In this paper, the friction and wear of bulk epoxy and unidirectional carbon fiber reinforced epoxy composite have been investigated under reciprocating sliding against either alumina or stainless steel balls in ambient air. The effect of sliding direction with respect to the long and unidirectional carbon fibers has been studied. We demonstrate that the carbon fiber reinforcement greatly improves the tribological properties of the thermoset epoxy: it reduces the coefficient of friction and the debris formation. It was found that on sliding in the anti-parallel direction a more significant degradation takes place than in the parallel direction. The coefficient of friction measured on bulk epoxy sliding against either stainless steel or alumina is around 0.65, whereas the coefficient of friction measured on epoxy reinforced with carbon fibers is significantly lower, namely down to 0.11. It was found that sliding with a stainless steel ball in a direction parallel to the fiber orientation results in a lower coefficient of friction than sliding in anti-parallel direction. The reduced coefficient of friction is largely influenced by the carbon fiber reinforcement due to the auto-protecting film formed as a paste in the contact area and along the wear track edges. The relationship between friction and degradation of the composite material including surface wear and debris formation are discussed based on an in-depth analysis of the worn surfaces by optical and scanning electron microscopy, micro-Raman spectroscopy, and white light interferometry.     

纳米SiC和微米SiC填充聚醚醚酮的磨损机理研究

利用热压法分别以纳米ＳｉＣ和微米ＳｉＣ作为填产制取了两类不同ＳｉＣ填充的聚醚醚酮复合材料，并对它们在干摩擦条件下的摩擦磨损性能进行了研究，同时还用扫描电子显微镜对摩擦表面形貌进行了观察，进而对材料的磨损机理作了分析与讨论。研究结果表明，１０％（ｗｔ）纳米ＳｉＣ作为填料能有效的改善其填充聚醚醚酮的摩擦磨损性能，而相同含量的微米ＳｉＣ作为填为只能使其填充聚醚醚酮的耐磨性能有所改善，但没有减摩效果。微米     

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.     

Mechanical and tribological properties of ceramic-matrix friction materials with steel fiber and mullite fiber

The purpose of the present work was to investigate and compare the mechanical and tribological behaviors of ceramic-matrix friction material (CMFM) with steel fiber (SF), mullite fiber (MF), and mixing SF and MF. The CMFM was prepared by hot-pressing sintering, and the tribological behaviors were determined using a constant speed friction tester. The worn surfaces and wear debris were observed by a scanning electron microscopy (SEM). Experiment results show that the combination of SF and MF can improve the mechanical properties that each single fiber does not have. The sever fade for the specimen reinforced by single MF during the whole friction testing can be attributed to the poor interface cohesive strength between MF and matrix. Mixing the SF and MF can improve the friction stability, and the friction coefficients for friction material with a mixture of the SF and MF increases with increasing MF content. For all specimens, increasing in the friction temperatures result in the increase of wear rates.     

铝基复合材料摩擦磨损性能研究

为研究碳纤维对Al1O3f/ZL109复合材料摩擦磨损性能的影响,进一步提高金属基体的摩擦磨损性能,利用液态模锻法制备了(Cf,Al2O3f)/ZL109复合材料,并研究了该材料的摩擦磨损性能.结果表明:各种(Cf,Al2O3f)/ZL109复合材料的磨损量均随载荷的增加而增大,但复合材料的磨损量均低于ZL109基体,且在总纤维体积分数为12%的复合材料中,(4?,8%Al2O3f)/ZL109复合材料具有最低的磨损量;各种(Cf,Al2O3f)/ZL109复合材料的摩擦因数均随载荷的增加而减小.(Cf,Al2O3f)/ZL109复合材料的耐磨性由碳纤维与氧化铝纤维性能及基体共同决定.     

碳纤维增强尼龙1010的力学性能及其对摩擦磨损的影响

用碳纤维填充尼龙1010制备了碳纤维增强尼龙复合材料,并对碳纤维增强尼龙复合材料的力学性能和摩擦学性能进行了实验研究。力学实验结果表明:碳纤维增强使尼龙复合材料的拉伸强度、表面硬度增大,碳纤维增强尼龙材料的拉伸强度在20%碳纤维含量时达到最大值;碳纤维表面处理对尼龙复合材料的拉伸强度有很大影响,碳纤维表面氧化处理提高了碳纤维增强尼龙复合材料的拉伸强度。摩擦磨损实验表明:碳纤维增强尼龙复合材料的摩擦系数和磨损率与其拉伸强度和硬度有密切关系。随着拉伸强度和硬度的提高,尼龙复合材料摩擦系数和磨损率降低;摩擦系数和磨损率与拉伸强度具有反比关系,与材料硬度具有二次方程关系,与碳纤维填充量之间存在负指数变化规律。      

多纤维增强重型汽车制动器摩擦材料的摩擦磨损性能研究

采用芳纶浆粕、玻璃纤维、硅灰石纤维和钛酸钾晶须多纤维混杂增强制备重型汽车制动器摩擦材料.利用XD-MSM型定速摩擦试验机,考察了摩擦材料的摩擦系数和磨损率随温度变化的情况,并且通过扫描电镜观察了摩擦材料在不同温度下磨损后的表面形貌,分析其摩擦磨损机理.研究结果表明,所研制的摩擦材料具有足够的机械性能和优异的摩擦磨损性能,热衰退小、恢复性能好、耐磨损,可满足重型汽车制动性能的要求.材料在中高温下主要是磨粒磨损和热疲劳磨损,同时伴随着粘着磨损.     

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.     

Dry sliding wear behavior of stir cast aluminium base short steel fiber reinforced composites

Dry sliding wears behavior of die cast aluminium alloy composites reinforced with copper-coated short steel fibers were investigated using a pin-on-disk wear-testing machine. The composites were prepared by liquid metal route using vortex method. The weight percentage of copper-coated steel fibers was varied from 2.5 to 10. The density and hardness of the composite increased linearly with increasing wt% of steel fibers. The wear rate decreased by 40% with addition of 10% weight percentage of fibers. A linear dependence of wear rate on fiber content and hardness of MMC is observed. The unreinforced aluminium and composites containing upto 5-wt% of fibers exhibited a sliding distance dependent transition from severe to mild wear. However, composites containing 10-wt% fiber showed only mild wear for all sliding distance. It was also observed that with increase in the fiber content to 10-wt% the coefficient of friction decreased by 22%. The duration of occurrence of the severe wear regime and the wear rate decreased with increasing fiber content. For the composite the wear rate in the mild wear regime decreased with increase in fiber content reaching a minimum. From the analysis of wear data and detail examination of (a) wear surface and (b) wear debris two modes of wear have been identified to be operative, in these materials. These are (i) adhesive wear in the case of unreinforced matrix and in MMC with low wt% (upto 5-wt%) fibers (ii) abrasive wear in case of MMC with high wt% of fibers.     

粉煤灰增强树脂基摩擦材料磨屑形貌及成分分析

通过干法热压工艺制备了粉煤灰增强树脂基摩擦材料,利用D-MS型定速式摩擦试验机测其在不同温度下的摩擦磨损性能,并收集磨屑。借助扫描电子显微镜观察、分析样品摩擦后的表面和磨屑形貌,研究了摩擦材料磨损的内在机制,并借助X射线衍射仪、X射线能谱仪、红外光谱仪进行综合表征。结果表明,添加粉煤灰的树脂基摩擦材料摩擦表面形成连续、稳定的摩擦膜,能够有效改善树脂基摩擦材料的摩擦磨损性能。对磨屑的分析实验证明摩擦膜的产生与粉煤灰中SiO2和Al2O3有关。     

具有纳米调制结构的AlTiN/AlCrN复合涂层在干摩擦条件下的摩擦磨损性能研究

目的 研究干摩擦条件下不同AlTiN/AlCrN多层膜纳米调制结构对摩擦磨损行为的影响。方法 将处理过的合金工具钢和单晶硅片作为膜层生长的基底材料,在膜层制备之前,先对基底材料进行预处理,然后使用多靶磁控溅射纳米膜层系统沉积一系列不同调制周期和调制比的AlTiN/AlCrN纳米多层膜。通过控制涂层总厚度不变,在调制比为1︰1时,设计不同的调制周期,择优选出磨损量最小、耐磨性最好的调制周期,并以此为恒定值,进而设计不同调制比的试样。采用X射线衍射仪(XRD)、摩擦磨损试验机分析与表征纳米多层膜的微观结构和性能,研究调制周期和调制比对AlTiN/AlCrN纳米多层膜微观结构和干摩擦条件下摩擦磨损性能的影响。结果 AlTiN/AlCrN纳米多层膜主体均为面心立方结构,且在(111)、(200)和(220)晶面择优取向。调制结构对多层膜的磨损特性影响较大,当调制周期为14.4 nm时,在干摩擦条件下AlTiN/AlCrN纳米多层膜的摩擦磨损量最小;在调制周期恒定为14.4 nm情况下,当调制比为3︰1时,在干摩擦条件下AlTiN/AlCrN纳米多层膜的耐磨性能最好;AlTiN/AlCrN纳米多层膜的磨损机理主要以磨粒磨损和黏附磨损为主。结论 优化的AlTiN/AlCrN多层膜纳米调制结构技术可应用在切削刀具的表面再制造领域,从而延长刀具工作寿命,通过涂层良好的耐磨性能提升设备的加工效率。     

Effect of volume fraction of carbon fibers on wear behavior of Al/Al2O3/C hybrid metal matrix composites

Wear behavior of Al/Al₂O₃/C hybrid metal matrix composites fabricated by squeeze casting method was characterized. The effects of volume fraction of carbon fiber on wear behavior of hybrid composites was investigated. Wear behavior of Al/Al₂O₃/C composites was characterized by the dry spindle wear test under various sliding speeds.

The wear resistance of Al/Al₂O₃/C composites was remarkably improved over Al/Al₂O₃ composites by adding carbon fibers to Al/Al₂O₃/C composites. Specifically, at the intermediate sliding speed the wear resistance of Al/Al₂O₃/C composites containing 8 vol.% carbon fiber was found to be better than that of the rest of the carbon hybrid composites. From fractographic studies, damaged sections in wear surfaces of hybrid composites at intermediate sliding speed were not observed due to the formation of solid lubrication film. The solid lubrication film which was formed as a result of adding carbon fibers improved the wear resistance of carbon hybrid composites because this film reduced the high friction force between MMCs and counter material.     

碳毡/铜复合材料的摩擦磨损特性研究

本文研究了用电沉积法制备的碳毡/铜复合材料的摩擦磨损特性。研究结果表明,在干摩擦条件下,复合材料的耐磨性主要与摩擦副间维持连续有效碳膜时间的长短有关,该时间取决于碳毡纤维的体积分数。在油润滑条件下,碳毡/铜复合材料的耐磨性与复合材料的硬度及纤维弯曲和破断所消耗能量的多少有关。在这两种条件下,复合材料的耐磨性均明显优于常用耐磨铜合金ZQSn6-6-3.     

氟化钙和炭纤维混杂增强尼龙复合材料的摩擦学性能和磨损机理

以注塑成型法制备了无机填料氟化钙(CaF2)和炭纤维增强尼龙1010复合材料,采用MM-200型磨损试验机考察了复合材料的摩擦磨损性能。研究结果表明,CaF2和炭纤维的复合添入可显著改善尼龙复合材料的摩擦学性能。其中30％CF～10％CaF2-Nylon的耐磨性能比30％CF-Nylon提高近5倍,而摩擦系数降低了约1／4．CaF2和CF增强尼龙复合材料在摩擦过程中发生了协同效应,CF-CaF2-Nylon在对偶钢环表面上生成富含钙元素的连续薄转移膜。提高了转移膜和对偶间的结合强度以及复合材料耐磨性能．     

喷射成形Vanadis 10冷作模具钢的摩擦磨损性能研究

采用喷射成形技术制备了高合金Vanadis10冷作模具钢。利用金相显微镜观察了喷射态Vanadis10钢的显微组织。借助SRV高温摩擦磨损试验机,研究了鼠N4／Vanadis10钢配对时的摩擦磨损性能。采用扫描电子显微镜（SEM）和能谱分析仪（EDS）,观察和分析了其磨损表面形貌和表面元素成分,并对其主要磨损机理进行了分析。结果表明：喷射态Vanadis10钢具有细小、均匀的微观组织。随着载荷的增加,其摩擦系数减小;随着频率的增加,其摩擦系数增大。摩擦过程中材料的磨损机理包括：磨粒磨损,粘着磨损。     

短碳纤维增强铜基复合材料的摩擦磨损性能研究

采用冷压烧结工艺制备了短碳纤维增强铜基复合材料,考察了该复合材料的干摩擦磨损性能.讨论了短碳纤维含量、载荷、转速等对复合材料摩擦性能的影响.结果表明:复合材料的耐磨性能明显优于基体材料;随着碳纤维含量的增加复合材料的耐磨性能进一步提高;随载荷和转速的提高,摩擦系数和磨损量也随之增加;复合材料由纯铜的粘着磨损转变为剥层磨损,并均伴有一定的氧化磨损.     

Studies on Mechanical, Friction, and Wear Characteristics of Kevlar and Glass Fiber-Reinforced Friction Materials

Asbestos possesses properties that are ideally suitable for use as a friction material in automotive and a number of other applications. Animal and human studies carried out since the early 1900s have established that asbestos is carcinogenic and that exposure to especially asbestos dust causes a large number of diseases. Realizing the health hazards posed by asbestos, many countries started phasing out asbestos from all asbestos-containing products since the 1980s. Some of them imposed a total ban in the 1990s on the use of asbestos-containing friction products. This situation forced many manufacturers to look for alternatives to asbestos. But the efforts have only been partly successful. The search is, therefore, still on to find suitable substitutes for asbestos. Though steel wool, Kevlar, glass, and a number of other mineral fibers have been tried out on an experimental basis over the last two decades, glass and Kevlar fibers, in particular, have shown promise as potential substitutes for asbestos. These days, therefore, studies on polymer-based friction materials reinforced with glass, Kevlar, and ceramic fibers are being pursued with much fervor. However, conflicting views are prevailing even today as to the suitability of asbestos-free composites for automotive applications and freedom from the concomitant health risks posed by them. In the present work, therefore, phenolic resin matrix samples reinforced with different amounts of glass and Kevlar fibers were produced and characterized for their mechanical, physical, friction, and wear properties to assess their suitability for light passenger car applications. The study establishes that composites based on glass and Kevlar fibers show good mechanical, physical, friction, and wear characteristics, enhancing thereby their suitability for automotive applications. The property improvements achieved are correlated to the composition, microstructure, and the changes taking place on the surface of the friction composites.     

Friction and wear of friction composites reinforced by natural fibres

In the present work, friction material composites were proposed to be used as automotive friction materials. The composites were reinforced by agricultural fibres of corn, palm, and sugar bars. The conventional friction materials based on asbestos cause serious lung diseases and being cancerous potential. The aim of the present work is to replace them by the proposed composites because they are environmentally friendly friction material for brake lining and clutch facings. Agricultural wastes of sugar bars, corn and palms fibres were prepared to obtain fibres of length less than 5 mm. The fibre materials were mixed by carbon, barium sulfate, silica, metallic powders and phenol formaldehyde. The proposed composites were pressed in the die at 105°C temperature. The produced specimens were subjected to machining processes to obtain the cylindrical form of 8 mm diameter. Experiments were carried out using test rig designed and manufactured to measure both friction and wear. It consists of a rotating hollow flat disc made of carbon steel, with an outside diameter of 250 mm and 16 mm thickness. The experiments investigated the effect of agriculture fibre wastes (corn, sugar bars, and palms fibres) on friction coefficient and wear. Wear mechanisms of the proposed composites were characterized by scanning electronic microscopy. The tribological properties of the proposed composites materials were compared to three commercial brake linings. Based on the experimental results it was found that, addition of agriculture fibre wastes (corn, sugar bars, and palms fibres) to composites materials increased friction coefficient and decreased wear. Friction coefficient slightly increased, while wear drastically decreased with increasing fibres content. The maximum friction value (0.58) was obtained by composites containing 30 wt.% iron and 25 wt.% sugar bar fibres. The corn fibres were more compatible with aluminum powder where it gave the highest friction coefficient and relatively lower wear compared to other composites. Wear resistance of the tested composites containing bunches and aluminum represented the lowest values among composites containing corn and bunches fibres. The lowest wear values were observed for composites containing 25 wt.% corn fibres and 30 wt.% aluminum and composites containing 20–25 wt.% sugar bar fibres.