Friction and wear studies of polyimide composites filled with short carbon fibers and graphite and micro SiO2

Polyimide (PI) composites filled with short carbon fibers (SCFs), micro SiO₂, and graphite (Gr) particles were prepared by means of hot press molding technique. The friction and wear properties of the resulting composites sliding against GCr15 steel were investigated on a model ring-on-block test rig. Experimental results revealed that single incorporation of graphite and SCF significantly improve the tribological properties of the PI composites, but micro SiO₂ was harmful to the improvement of the friction and wear behavior of the PI composite. It is found that a combinative addition of Gr, SCF and micro SiO₂ was the most effective in improving the friction-reducing and anti-wear abilities of the PI composites. Research results also show that the filled PI composites exhibited better tribological properties under higher PV-product.     

Study on the synergistic effect of carbon fiber and graphite and nanoparticle on the friction and wear behavior of polyimide composites

In this paper, the effect of short carbon fiber (SCF), graphite (Gr) and nano-Si₃N₄ on the friction and wear behavior of polyimide (PI) composites were studied using a block-on-ring arrangement. Experimental results revealed that single incorporation of SCF and Gr can improve the friction-reducing and anti-wear abilities of the PI composites significantly. However, nano-Si₃N₄ deteriorated the wear resistance of the PI composite drastically as single filler. A synergistic effect was found for the combination of nano-Si₃N₄ and SCF and Gr, which lead to the best tribological properties. It also can be found that the filled PI composites exhibited better tribological properties under higher PV product (the product of load and sliding speed). Moreover, the filled PI composites showed better tribological properties under oil lubrication and worse tribological properties under water lubrication compared with that under dry sliding condition.     

The friction and wear properties of carbon nanotubes/graphite/carbon fabric reinforced phenolic polymer composites

In this paper, either graphite (Gr) or carbon nanotubes (CNTs), or both of them were incorporated into carbon fabric reinforced phenolic (CFRP) composites, preparing by a dip-coating and heat molding process, the tribological properties of the resulting composites were investigated using a block-on-ring arrangement. The worn surfaces were observed by scanning electron microscope to understand the mechanism. Experimental results showed that the optimal Gr was more beneficial than CNTs in improving the tribological properties of the CFRP composites when they were singly incorporated. It is well worth noting that the friction and wear behavior of the CNTs-filled CFRP composites were improved further when Gr was added, indicating that there is a synergistic effect between them. Tribological tests under different sliding conditions revealed that the Gr and CNTs-filled CFRP composites seemed to be the most suitable for tribological applications under higher sliding speed and load, and oil lubrication.     

Study on the friction and wear behavior of basalt fabric composites filled with graphite and nano-SiO2

To improve the friction and wear behavior of basalt fabric reinforced phenolic composites, single graphite or nano-SiO₂ and both of them were incorporated. The tribological properties of the resulting composites under different sliding conditions were investigated systematically on a model ring-on-block test rig. The friction and wear mechanisms of the composites were studied through analyzing the worn surfaces and transfer films by a scanning electron microscopy (SEM). Experimental results showed that graphite (Gr) was more beneficial than nano-SiO₂ in improving the tribological properties of basalt fabric composites (BFC) when they were singly incorporated. It is well worth noting that the friction and wear behavior of the filled composites was improved further when nano-SiO₂ and graphite were added together, indicating that there was a synergistic effect between them. Tribological tests under different sliding conditions revealed that the BFC/Gr/SiO₂ composites seemed to be more suitable for tribological applications under higher sliding speed and load.     

Friction and wear properties of UHMWPE composites reinforced with carbon fiber

The artificial joint acetabular material ultrahigh molecular weight polyethylene (UHMWPE) was reinforced with carbon fibers (CF) in different contents. The effects of CF content on hardness and tribological properties of the materials were studied. The morphologies of wear surfaces were examined with a Scanning Electron Microscope (SEM). The results show that the hardness and wear resistance of CF-reinforced UHMWPE composites increased with CF content; the friction coefficients under distilled water lubrication were decreased greatly by the addition of CF; that adherence, plowing, plastic deformation and fatigue wear are dominant for the UHMWPE under dry sliding, and that abrasive wear and drawing out of CF from the wear surface of the composites are dominant for the CF-UHMWPE composites under both dry and distilled water lubrication conditions.     

The preparation and characteristic of maleic anhydride grafted polyethylene (PE-g-MA) filled CNT/PMMA composite film

ABSTRACT

In order to improve the tribological properties of PMMA, the PMMA composites incorporated with CNT powders were prepared. The effect of CNT content on tribological properties of the composites was investigated. When CNT content is 0.5 wt%, the friction coefficients of the 0.5%CNT/PMMA composite are the smallest, which are about 0.15 and are 67% less than those of the pure PMMA composite, and its wear resistance remains the same as the pure PMMA composite. Incorporating 0.5 wt% CNT into the PMMA composite may develop a continuous transferred film on the worn surface. As a result, the friction coefficients of the composite are reduced and its wear mechanism is mainly fatigue spalling. The addition of PE-g-MA improved the friction and wear properties of CNT/PMMA composite.     

梯度自润滑复合材料在不同滑动摩擦下的摩擦学特性

梯度自润滑复合材料是一种新型润滑材料,利用粉末冶金工艺设计和制备了该材料,考察了其在不同摩擦条件下的摩擦学特性,并对其摩擦磨损机理进行了分析和研究.结果表明:梯度自润滑复合材料随着复合固体润滑剂含量的增多,摩擦学性能明显改善,但润滑剂含量过高将导致材料表面硬度过低;该材料适用于高载倚下的润滑部件;脂润滑条件下,复合固体润滑剂与润滑脂结合在摩擦面上形成的膏状润滑膜使梯度自润滑复合材料的摩擦学性能显著改善;在脂润滑高载荷条件下,梯度自润滑复合材料的磨损主要发生在磨损初期,之后磨损极小,摩擦系数也趋于减小.     

Effect of surface oxidation treatment on the tribological performance of carbon fiber reinforced polyimide composites

The effect of ozone surface treatment of carbon fibers (CF) on the tensile strength and tribological properties of carbon fiber reinforced polyimide (CF/PI) composite was investigated. Experimental results revealed that the tensile strength of ozone and air oxidation treated CF reinforced PI composite was improved compared with that of untreated composite. Compared with the untreated and air‐oxidated CF/PI composite, the ozone treated composite had the lowest friction coefficient and specific wear rate under given applied load and reciprocating sliding frequency. Ozone treatment effectively improved the interfacial adhesion between CF and PI. The strong interfacial adhesion of the composite made CF not easy to detach from the PI matrix, and prevented the rubbing‐off of PI, accordingly improved the friction and wear properties of the composite.     

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。     

三维编织复合材料在润滑条件下的摩擦性能

利用树脂传递模塑(RTM)工艺制备了三维编织炭纤维/环氧(C3D/EP)复合材料.采用MM-200型摩擦磨损试验机研究了该材料润滑条件下的摩擦磨损性能,探讨了载荷及滑动速度等外界因素的影响;并采用XL30 ESEM电子显微镜观察磨损表面形貌,分析了其磨损机理.结果表明,润滑条件下复合材料的摩擦磨损性能远优于干摩擦,且磨合期较短;随着载荷的增加,复合材料的摩擦系数和比磨损率降低,但滑动速度对摩擦磨损性能的影响很小;润滑条件下的磨损机理主要是磨粒磨损.     

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.     

碳纤维及石墨填充聚四氟乙烯复合材料的摩擦学性能研究

利用M-200型环-块摩擦磨损试验机对石墨(Gr.)及碳纤维(CF)填充聚四氟乙烯(PTFE)复合材料的摩擦磨损性能进行了研究,探讨了石墨及碳纤维的协同润滑效应.认为碳纤维的加入大大提高了复合材料的承载能力,石墨的加入减小了碳纤维表面与对偶的摩擦系数,从而降低了碳纤维的脱落趋势,提高了复合材料的耐磨性.利用扫描电子显微镜(SEM)对PTFE复合材料的摩擦面及对偶转移膜进行了观察.结果表明,本实验中20%的石墨和10%碳纤维填充PTFE复合材料的摩擦磨损性能最好,且在高载荷下的摩擦磨损性能尤为突出,具有一定的应用价值.     

Synergism of carbon fiber and polyimide in polytetrafluoroethylene-based composites: Friction and wear behavior under sea water lubrication

Polytetrafluoroethylene-based (PTFE-based) composites reinforced simultaneously with carbon fiber (CF) and polyimide (PI) of different volume fractions were prepared. The microstructure and phase composition of as-prepared PTFE-based composites were analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Besides, their friction and wear behavior under sea water lubrication was evaluated in relation to the synergistic effect between CF and PI using a ring-on-block test rig, and their worn surfaces were also analyzed using SEM. Results showed that the incorporation of PI induced loosening of the microstructure of PTFE but increased the wear resistance. Contrary to the above, the incorporation of CF led to increased compactness of PTFE, and the compactness as well as wear resistance of the PTFE-based composites increased with the increase of CF content. More importantly, the simultaneous incorporation of PI and CF at a proper volume fraction led to drastically reduced wear rate of PTFE under sea water lubrication. This implies that there exists synergistic friction-reducing and wear-resistant effect between PI and CF. As a result, the PTFE-based composite containing 5% PI (volume fraction) and 15% CF had the best wear resistance, showing promising application in ocean environment.     

Effect of addition of graphite particulates on the wear behaviour in aluminium–silicon carbide–graphite composites

Aluminium matrix composites with multiple reinforcements (hybrid AMCs) are finding increased applications because of improved mechanical and tribological properties and hence are better substitutes for single reinforced composites. Few investigations have been reported on the tribological behaviour of these composites with % reinforcement above 10%. The present study focuses on the influence of addition of graphite (Gr) particulates as a second reinforcement on the tribological behaviour of aluminium matrix composites reinforced with silicon carbide (SiC) particulates. Dry sliding wear tests have been performed to study the influence of Gr particulates, load, sliding speed and sliding distance on the wear of hybrid composite specimens with combined % reinforcement of 2.5%, 5%, 7.5% and 10% with equal weight % of SiC and Gr particulates. Experiments are also conducted on composites with % reinforcement of SiC similar to hybrid composites for the sake of comparison. Parametric studies based on design of experiments (DOE) techniques indicate that the wear of hybrid composites decreases from 0.0234 g to 0.0221 g as the % reinforcement increases from 3% to 7.5%. But the wear has a tendency to increase beyond % reinforcement of 7.5% as its value is 0.0225 g at.% reinforcement of 10%. This trend is absent in case of composites reinforced with SiC alone. The values of wear of these composites are 0.0323 g, 0.0252 g and 0.0223 g, respectively, at.% reinforcement of 3%, 7.5% and 10% clearly indicating that hybrid composites exhibit better wear characteristics compared to composites reinforced with SiC alone. Load and sliding distance show a positive influence on wear implying increase of wear with increase of either load or sliding distance or both. Whereas speed shows a negative influence on wear indicating decrease of wear with increase of speed. Interactions among load, sliding speed and sliding distance are noticed in hybrid composites and this may be attributed to the addition of Gr particulates. Such interactions are not present in composite reinforced with SiC alone. Mathematical models are formulated to predict the wear of the composites.     

Tribological properties of fluorinated graphene reinforced polyimide composite coatings under different lubricated conditions

The tribological properties of polyimide (PI) and PI/fluorinated graphene (FG) nanocomposites, as a new class of graphene reinforced polymer, are investigated using a ball-on-disk configuration under different lubricated conditions of dry sliding, water lubrication and oil lubrication. Experimental results reveal that single incorporation of FG can effectively improve the tribological performance of PI under all the three conditions. In addition, compared to the results under dry sliding, the phenomenon that the friction coefficient decreases while the wear rate increases under water lubrication condition is observed and researched in detail. The worst anti-wear performance under water-lubricated condition can be ascribed to the fact that the water can be adsorbed by the polar imide radicals of the PI and PI/FG nanocomposite, therefore leading to the property deterioration of the PI and PI/FG nanocomposite coatings.     

PPESK树脂基复合材料的摩擦磨损性能

以含二氮杂萘酮结构的聚醚砚酮（ＰＰＥＳＫ）树脂为基体,填加固体润滑剂和短炭纤维（ＣＦ）制备了新型耐热脂基复合材料,研究了摩擦条件下（如载荷,行程等）和ＣＦ含量对复合材料的摩擦磨损性能的影响,分析了ＰＰＥＳK树脂及复合材料的磨损机理,结果表明,短ＣＦ和固体润滑剂的加入可有效改善ＰＰＥＳＫ的摩擦磨损性能,当ＣＦ含量为１０％时,复合材料的摩擦系数与聚西四氟乙烯（ＰＴＦＥ）相当,但比磨损率降低２个数量级,与纯树脂相比,磨擦系数减小为原来的二分之一,而复合材料的磨损特性主要表现为粘着磨损,ＰＰＥＳＫ树脂基复合材料批基体,聚四氟乙烯（ＰＴＦＥ）具有更好的耐磨性和自润滑性。     

Tribological properties of powder metallurgy – Processed aluminium self lubricating hybrid composites with SiC additions

In this experimental study, aluminium (Al)-based graphite (Gr) and silicon carbide (SiC) particle-reinforced, self-lubricating hybrid composite materials were manufactured by powder metallurgy. The tribological and mechanical properties of these composite materials were investigated under dry sliding conditions. The results of the tests revealed that the SiC-reinforced hybrid composites exhibited a lower wear loss compared to the unreinforced alloy and Al–Gr composites. It was found that with an increase in the SiC content, the wear resistance increased monotonically with hardness. The hybridisation of the two reinforcements also improved the wear resistance of the composites, especially under high sliding speeds. Additionally, the wear loss of the hybrid composites decreased with increasing applied load and sliding distance, and a low friction coefficient and low wear loss were achieved at high sliding speeds. The composite with 5 wt.% Gr and 20 wt.% SiC showed the greatest improvement in tribological performance. The wear mechanism was studied through worn surface and wear debris analysis as well as microscopic examination of the wear tracks. This study revealed that the addition of both a hard reinforcement (e.g., SiC) and soft reinforcement (e.g., graphite) significantly improves the wear resistance of aluminium composites. On the whole, these results indicate that the hybrid aluminium composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, predominantly in the aerospace and automotive engineering sectors.     

Friction and wear of epoxy/TiO2 nanocomposites: Influence of additional short carbon fibers, Aramid and PTFE particles

An epoxy-based nanocomposite containing graphite powder (7 vol%) and nano-scale TiO₂ (4 vol%) was developed for tribological evaluation. A series of composites containing additional fillers such as short carbon fibers (SCF), Aramid and polytetrafluoroethylene (PTFE) particles was developed and evaluated in adhesive and low amplitude oscillating wear modes. The incorporation of SCF and Aramid particles resulted in a remarkable improvement in the sliding wear resistance. However, SCF impaired the low amplitude oscillating wear resistance. The further addition of PTFE to the SCF filled nanocomposites reduced the friction and wear under both wear conditions. However, an adverse effect of PTFE was found for the Aramid particles filled nanocomposites. Under sliding conditions, the lowest wear rate and coefficient of friction showed the 2–4 vol% PTFE filled SCF nanocomposite. Aramid particles containing nanocomposites (without PTFE) exhibited the best wear and friction behavior under low amplitude oscillating wear conditions among the selected composites. The wear mechanisms were studied by scanning electron microscopy.     

Evaluation on tribological design coatings of Al2O3, Ni–P–PTFE and MoS2 on aluminium alloy 7075 under oil lubrication

The current work evaluated the friction and wear properties of tribological design surface coatings on aluminium alloy 7075 under various speed and nominal contact pressure. Hard-anodized Aluminium Oxide (Al₂O₃), burnished Refractory Metal Sulfide (MoS₂) and composite electroless nickel coatings with polytetrafluoroethylene (Ni–P–PTFE) particles were subjected to pin-on-disc sliding test against grey cast iron (GCI) under Mach 5 SL SAE 10 W-30 lubrication. The results indicated that Ni–P–PTFE composite coating possessed excellent friction–reduction capability but limited wear resistance due to low mechanical strength. Al₂O₃ coated sample showed outstanding wear resistance with high friction characteristic leading to high surface contact temperature. Furthermore, MoS₂ coating improved the wear resistance of the aluminium alloy.