Development of empirical model for abrasive wear volume of sisal fibre–epoxy composites

Abstract

In this paper, an empirical model was developed for high stress abrasive wear behaviour of unidirectional sisal fibre reinforced epoxy composites under varying operating parameters, for which a number of experiments were carried out to determine the abrasive wear behaviour of the composites. Polysulphide modified epoxy resin was used to make composites having three different sisal fibre concentrations in three different fibre orientations, namely longitudinal, transverse and normal. Abrasive wear of composites depends on operating parameters, such as applied load, grit size, sliding distance and weight percentage of sisal fibre. The abrasive wear data have been analysed using statistical analysis, and empirical relations are proposed.     

On sliding friction and wear of polyetheretherketone (PEEK) composites at elevated temperatures

The friction and wear behaviour of polyetheretherketone (PEEK) composites, incorporating different amounts of short carbon fibres with different surface treatments, was studied under dry sliding conditions against smooth steel on a pin-on-disc apparatus at different temperatures. Wear of the composites was reduced considerably in all cases, but, whatever the surface treatment, wear increased with increasing temperature for all proportions off fibres. For minimum friction coefficient there was an optimum proportion of fibre volume fraction of about 10 vol.%. The effect of the fibre surface treatment was not significant for the tribological behaviour of the PEEK composites. To predict wear performance, a wear model proposed by Friedrich and Voss seemed to work properly, and, furthermore, a friction model was developed to predict the friction behaviour of PEEK composites with short carbon fibres.     

Coefficient of Friction Measurements for Thermoplastics and Fibre Composites Under Low Sliding Velocity and High Pressure

Friction materials for typical brake applications are normally designed considering thermal stability as the major performance criterion. There are, however, brake applications with very limited sliding velocities, where the generated heat is insignificant. In such cases it is possible that friction materials which are untypical for brake applications, like thermoplastics and fibre composites, can offer superior performance in terms of braking torque, wear resistance and cost than typical brake linings. In this paper coefficient of friction measurements for various thermoplastic and fibre composite materials running against a steel surface are presented. All tests were carried out on a pin-on-disc test-rig in reciprocating operation at a fixed sliding speed and various pressure levels for both dry and grease lubricated conditions. Moreover, a generic theoretical framework is introduced in order to interpret the changes of friction observed during the running-in phase.     

La2O3对铜基自润滑复合材料高温摩擦磨损性能的影响

为进一步提高铜基自润滑复合材料的硬度和高温摩擦磨损性能,采用粉末冶金热压法向铜-石墨烯-WS2复合材料中引入La2O3增强相颗粒,并对铜-石墨烯-WS2复合材料和La2O3增强铜-石墨烯-WS2复合材料在不同温度下的摩擦磨损性能进行对比研究。结果表明:复合材料烧结过程中各组元没有发生分解或互相反应,烧结后材料结构致密并且各组元均匀分布于基体中,La2O3增强相的引入在提高复合材料硬度的同时会降低材料热导率;室温下2种复合材料摩擦因数和磨损率比较相近,而高温下石墨烯和WS2的氧化导致Cu-RGO-WS2复合材料摩擦磨损性能下降,而La2O3则能发挥增强相作用和高温自润滑作用,使Cu-RGO-WS2-La2O3复合材料的高温摩擦磨损性能更优异。室温下铜-石墨烯-WS2复合材料的磨痕处仅发生了轻微的塑性变形,而La2O3增强铜-石墨烯-WS2复合材料的磨损机制主要是磨粒磨损;高温下铜-石墨烯-WS2复合材料的磨损机制为黏着磨损,而La2O3增强铜-石墨烯-WS2复合材料的磨损机制则为磨粒磨损和疲劳磨损。     

制动摩擦副材质对其摩擦性能影响的研究

对有机石棉和半金属衬片材料与不同化学组分的灰铸铁制动盘（鼓）进行摩擦性能试验。分析了对偶材质对衬片磨损及摩擦系数的影响及衬片材质对制动盘（鼓）磨损的影响。提出了评定衬片材料的耐磨性必须标明对制动盘（鼓）的损伤及制动副材料的最佳选配问题。     

聚苯酯填充聚四氟乙烯复合材料摩擦学行为研究

采用聚苯酯（Ekonol）、Ekonol／PAB纤维增强聚四氟乙烯（PTFE）制备利用转移膜润滑的摩擦副材料，并研究了两组材料在于摩擦条件下与9Cr18轴承钢对摩时的摩擦学性能；运用扫描电镜分析了两组材料磨损表面形貌和磨损机理。结果表明：随着Ekonol含量的增大，Ekonol填充PTFE复合材料的摩擦因数逐渐增大，当Ekonol质量分数超过25％时摩擦因数略有下降，磨损方式由以犁削磨损为主转变为以疲劳磨损为主；而Ekonol／PAB纤维填充门FE复合材料的摩擦因数，随Ekonol含量的增大而增大，磨损方式由以粘着磨损为主转变为以疲劳磨损为主。Ekonol／PAB纤维填充PTFE复合材料的摩擦学性能优于Ekonol填充PTFE复合材料。     

Sliding wear behavior of planar random zinc-alloy matrix composites

The friction and wear behavior of planar random zinc-alloy matrix composites reinforced by discontinuous carbon fibres under dry sliding and lubricated sliding conditions has been investigated using a block-on-ring apparatus. The effects of fibre volume fractions and loads on the sliding wear resistance of the zinc-alloy matrix composites were studied. Experiments were performed within a load range of 50–300 N at a constant sliding velocity of 0.8 m s⁻¹. The composites with different volume fractions of carbon fibres (0–30%) were used as the block specimens, and a medium-carbon steel used as the ring specimen. Increasing the carbon fibre volume fraction significantly decreased the coefficient of friction and wear rates of both the composites and the medium-carbon steel under dry sliding conditions. Under lubricated sliding conditions, however, increasing the carbon fibre volume fraction substantially increased the coefficient of friction, and slightly increased the wear of the medium-carbon steel, while reducing the wear of the composite.Under dry sliding conditions, an increasing load increased not only the wear rates of both the composite and the unreinforced zinc alloy, but also those of their corresponding steel rings. However, the rate of increase of wear with increasing load for both the composite and its corresponding steel ring was much smaller than for the unreinforced zinc alloy and its corresponding steel ring. The coefficient of friction under dry sliding conditions appeared to be constant as load increased within a load range of 50–150 N for both the composite and the unreinforced zinc alloy, but increased at the higher loads. Under any load the coefficient of friction of the composite was lower than half that of the unreinforced zinc alloy under dry sliding conditions.     

GF/PTFE自润滑纤维复合材料磨损性能热衰退研究

针对高频摆动关节轴承摩擦热对自润滑纤维复合材料摩擦磨损性能的影响,研制了高频使用条件下的玻璃纤维增强聚四氟乙烯(GF/PTFE)自润滑纤维复合材料,利用MYB～500高频高载摆动摩擦磨损试验机,对其进行不同摩擦温度下的摩擦磨损性能测试,研究摩擦热作用下材料自润滑性能和磨损性能衰退特征,分析磨损产物和摩擦表面以及不同摩擦温度下材料的磨损机理。结果表明,摩擦热对材料自润滑性能影响显著,适当的摩擦温度范围能够保证材料的自润滑性能,摩擦温度和摩擦因数之间互为耦合作用,对材料的磨损性能具有一定的影响;高摩擦热作用于自润滑过程及机理的改变,造成材料的磨损性能衰退现象。因此,不同温度下材料的磨损特征具有明显的差异化,其中低摩擦温度下(60～120℃)材料自润滑性能优异,磨损率很低;140℃摩擦温度条件下材料摩擦磨损性能开始衰退;材料在高摩擦温度下(140～180℃)的磨损初期自润滑性能良好、磨损轻微,而中后期磨损严重。微观分析表明,低摩擦温度下材料的磨损机理以轻微粘着和疲劳磨损为主;高摩擦温度下材料的磨损以片状剥落、纤维剪切破坏为主,且磨损面局部损伤特征明显,磨损严重。     

带式输送机树脂基摩擦片干式制动条件下摩擦学行为

采用热压烧结技术制备桐油改性酚醛树脂和腰果壳油改性酚醛树脂基摩擦片,通过CFT环块摩擦磨损试验机研究其在不同的制动速度、制动正压力下以及在瞬时制动时的摩擦因数以及磨损率的变化规律,采用扫描电镜(SEM)对试样摩擦后的表面形貌进行观察分析。结果表明,2种树脂基摩擦片摩擦因数以及磨损率变化规律具有一致性:摩擦因数均随着制动正压力与制动速度的增加而减小;磨损率随着制动速度的增加而减小,随着制动正压力的增加而增加。以桐油改性酚醛树脂为基体,碳纤维为增强纤维的摩擦片在瞬时制动时具有较稳定的摩擦因数,而且在不同制动正压力与制动速度下磨损率较低。     

Traditional and new approaches to the development of wear‐resistant polymer composites

This overview describes the development of polymeric composites for operation with low friction and wear against steel counterparts, with special emphasis on injection‐mouldable short‐fibre‐reinforced thermoplastics. This work has aimed to optimise their friction and wear properties and to carry out systematic parameter studies using artificial neural networks; information is presented on the systematic development of continuous‐fibre polymer‐based composites with high wear resistance and on the prediction of their load‐bearing capacity using a finite‐element approach. Finally, some new steps towards the development of functionally graded tribo‐materials are described.     

摩托车盘形制动器摩擦片材料磨损形貌分析

采用XDZ-A型摩擦材料制样机将有机石棉摩擦片材料制备成试验所需的标准试样,用X-DM型调压变速摩擦试验机模拟摩托车制动实际工况,对标准试样开展不同压力、滑动速度和温度下的组合试验.对扫描电子显微镜(SEM)观测到的有机石棉摩擦片材料与灰铸铁HT250摩擦盘对磨后的磨损形貌进行了分析.分析结果表明:无论是正压力、速度的增大还是温度的升高,都使得摩擦片磨损越来越严重,形貌越来越复杂.     

Effects of Resin Type and Fiber Length on the Mechanical and Tribological Properties of Brake Friction Materials

In this study, the effects of resin type and fiber length on mechanical properties and friction characteristics of automotive brake materials were studied. Three types of resin, viz. straight phenolic resin (SR), cashew nut shell liquid modified resin (CR), and melamine resin (MR) were used as matrix material. Lapinus with different lengths was used as inorganic fiber. Three series of friction composites composed of nine composites in the form of brake materials were manufactured. Physical, mechanical, and tribological properties of all composites were investigated. The friction tests were performed using a Chase type friction tester. The results showed that both resin type and fiber length played an important role on the mechanical and tribological properties of the friction materials. The highest and the lowest friction coefficient for resin types were recorded for SR and MR composites, respectively, while MR and CR composites showed the highest and the lowest wear resistance, respectively. For the fiber length considered, increasing the fiber length increased the wear resistance of the composites. The coefficient of friction, in general, showed a good correlation with the wear resistance of the composites. But, there was no clear correlation with the mechanical and tribological properties of the composites. The morphological features of worn surfaces and wear debris of the composites were analyzed in order to understand the friction and wear mechanisms of this tribosystem.     

Tribological behavior of natural fiber reinforced PLA composites

The application spectrum of natural fiber reinforced polymer composites is growing rapidly in various engineering fields. The present study explores the possibilities of reinforcing thermoplastic bio-polymer with locally available inexpensive plant fibers for developing a new tribo-material. Three different types of natural fibers (nettle, grewia optiva and sisal) were incorporated into PLA polymer to develop laminated composites using a hot compression technique. TGA analysis was carried out to investigate the thermal stability of developed composites. Wear and frictional characteristics of developed composites were investigated under dry contact condition at different operating parameters, such as applied load (10–30 N), sliding speed (1–3 m/s) and sliding distance (1000–3000 m). The experimental results indicate that incorporation of natural fiber mats into PLA matrix significantly improves the wear behavior of neat polymer. There was 10–44% reduction in friction coefficient and more than 70% reduction in specific wear rate of developed composites as compared to neat PLA. The worn surface morphology was studied using scanning electron microscope (SEM) to analyze the wear mechanism in different types of developed composites.     

剑麻纤维和低密度聚乙烯填充聚甲醛复合材料的摩擦磨损性能

通过双螺杆挤出熔融共混的方法制备剑麻纤维(SF)和低密度聚乙烯(LDPE)共同填充的聚甲醛复合材料,在HT-500型高温摩擦磨损试验机上考察其干滑动摩擦条件下的摩擦磨损性能,并通过扫描电子显微镜(SEM)观察其磨损表面形貌,分析磨损机制。结果表明:添加适量的LDPE能显著降低POM的摩擦因数和磨损率,当LDPE质量分数为5%时,复合材料的摩擦因数下降21.7%,磨损率降低10%;随SF质量分数的增加,POM/5%LDPE/SF复合材料的摩擦因数和磨损率呈现先增大后减小再增大的趋势,当SF质量分数为5%时,复合材料摩擦磨损性能优异,在转速为1 120 r/m in,恒定载荷为8 N的实验条件下,其稳定摩擦因数为0.16,磨损率为1.61×10-6mm3/(N.m)。纯POM磨损方式以黏着磨损为主,POM/5%LDPE/SF复合材料以疲劳磨损为主,伴随有转移膜的剥落。     

Influence of matrix carbon texture on the temperature field of carbon/carbon composites during braking

The friction, wear and thermal properties and temperature fields of three C/C composites with different matrix carbon textures were investigated in simulations of normal landing condition for aircraft brake disks. Temperature fields were also simulated using a finite element method. The matrix carbon textures had important influence on temperature fields. The sample with rough laminar pyrolytic carbon is the best choice for airplane brake disk due to its excellent friction, wear and thermal properties and lower temperature at the friction interface and thermal gradient by contrast with the samples with resin-derived carbon and smooth laminar pyrolytic carbon.     

The effect of fibre reinforcement on the friction and wear of polyamide 66 under dry rolling–sliding contact

An investigation into the effect of fibre reinforcement on the friction and wear of PA66 in rolling–sliding contact is reported. Three types of short fibre—aramid, carbon and glass—were examined with the composites running against identical materials in a twin disc machine. It was found that the aramid-fibre reinforcement did not significantly alter the friction of the matrix material. However, both the carbon-fibre and glass-fibre reinforcement reduced the coefficient of friction substantially. Wear of the aramid- and carbon-fibre composites was essentially linear with time and generally around ten times greater than that of the unreinforced material. The wear of the glass-fibre composite was complex with an initial period where the wear rate was similar to that of the unreinforced material. After a significant depth of wear had occurred the wear rate changed to a value similar to, but slightly higher than, that of the other reinforced materials.It appears that one of the major benefits of introducing fibre reinforcement, particularly glass, is that it reduces the coefficient of friction and hence allows the material to be used for higher duties without exceeding the softening point of the matrix. This increase in duty is, however, at the expense of an increased wear rate and shorter component life.     

Tribo-mechanical properties of glass fibre reinforced polypropylene composites

Fibre reinforced polypropylene (PP) composites are frequently used for structural applications. In this context, it is of particular importance how much the tribological properties of PP can be improved by fibre reinforcement. Based on experimental investigations, this issue is discussed in the article by studying the tribo-mechanical properties of different PP composites. The relevant parameters of friction and wear are presented in order to provide a comprehensive data set for applications. Additionally, the wear mechanisms are studied phenomenologically by means of optical microscopy. It was shown that the tribo-mechanical properties of PP can be significantly influenced with a suitable reinforcement.     

Friction and wear performances of brake material dry sliding against a composite with a semi-interpenetrating network structure of ceramics and Al-alloy

The friction and wear performances of brake material dry sliding against semi-interpenetrating network ceramics/Al-alloy composites were determined using a SRV testing machine. For applied loads from 40-160 N, the friction decreased at 100 and 250 °C. The former friction was superior to the latter. Wear increased at 100 °C but decreased at 250 °C, and converged gradually in both cases. Friction fade took place at high temperatures, followed by overrecovery upon cooling. Higher temperatures increased wear. The proposed friction models incorporated with scanning electron microscopy and energy dispersive X-ray analysis explain the test results better.     

Fundamental studies on the brake friction of resin-based friction materials

The effects of various factors on brake friction were studied on the braking of a cast iron disk by small brake specimens made of resin, resin-asbestos composites and three-component composites. When the disk temperature rises, the resin-based composites containing asbestos and high melting point additive exhibit considerably lower friction during braking following high friction in the initial braking stage. The initial high friction is attributed to the deformation resistance of the resin in the composite. Low friction is attributed to the lubricating action of resin decomposition products in the neighbourhood of the filler raised to a high temperature by frictional heating. Increase of friction toward the end of braking is mainly due to increase of the true contact area as the frictional speed decreases. Variation of the average frictional coefficient during braking with load and the initial speed is generally small. There is no correlation between the mechanical properties and the brake frictional behaviour of resin-based composites.     

Dry sliding friction and casing wear behavior of PCD reinforced WC matrix composites

The friction and casing wear properties of PCD reinforced WC matrix composites were investigated using a cylinder-on-ring wear-testing machine against N80 casing steel counterface under dry sliding conditions. The results indicate that the friction and casing wear rate of PCD reinforced WC matrix composites are the lowest among the materials. As the applied load and sliding speed steadily increase, the friction coefficients of PCD reinforced WC matrix composites decrease. In addition, the casing wear rates increase with increasing load, but decline with sliding velocity. The dominant wear mechanism of the PCD composite is the micro-cutting wear, accompanied by adhesive wear.