Influence of content of carbon fabric on the low amplitude oscillating wear performance of polyetherimide composites

Tribo-potential of bi-directionally (BD) reinforced polymer composites is not yet adequately explored especially in low amplitude oscillating wear (LAOW)/fretting wear mode. Hence five composites of Polyetherimide (PEI) containing carbon fabric (plain weave) in the range 40–85 by vol% were developed by impregnation technique followed by compression molding. These composites along with unfilled PEI were evaluated for their LAOW performance on SRV Optimol tester under different loads using ball-on-plate configuration. The performance was compared with that of composite evaluated in earlier work but developed with different processing technique (hand lay up). With increase in load, specific wear rates of all the composites increased while friction coefficient (μ) decreased. It was concluded that carbon fabric inclusion in all amounts proved significantly beneficial for improving friction and wear performance and limiting load of PEI. Very high and very low amount of CF (85 and 40 vol%) proved least beneficial from strength and tribo-performance point of view. Composites with moderate amount of CF (65 and 55 vol%) proved most promising with almost similar potential in reducing μ and wear rate of PEI. Overall CF in the range of 55–65 vol% appeared to be the optimum range for tailoring the strength properties along with tribo-performance in fretting wear mode. The impregnation technique proved significantly better than the hand lay up technique for enhancement in strength and tribo-performance. SEM studies on worn surface proved helpful in understanding wear mechanisms.

Abrasive wear performance of carbon fabric reinforced polyetherimide composites: Influence of content and orientation of fabric

Dry abrasive wear performance of five plain weave carbon fabric (CF) reinforced Polyetherimide (PEI) composites, developed with increasing CF contents (in the step of 10 vol%) is reported in this paper. It was observed that composite reinforced with 65 vol% CF (IP₆₅) exhibited the best tensile and shear strength and closely followed the leader (IP₇₅) in flexural strength. IP₆₅ when abraded against silicon carbide paper showed highest wear resistance (W_R) and lowest friction coefficient (μ) among all composites. The composites IP₈₅ and IP₄₀ containing highest and lowest amount of CF respectively showed least enhancement in strength properties and poorest wear performance. Parallel studies on the influence of fabric orientation with respect to the sliding plane and direction, on W_R showed that when CF was oriented parallel to the sliding plane, it had poorest wear resistance. The performance improved for the composites when fabric was oriented normal to the plane. The parallel or anti-parallel orientation of warp or weft fibers with respect to sliding direction showed marginal changes in friction and wear performance. Wear mechanisms were suggested and strongly supported by worn surface analysis using SEM.Efforts were also done to investigate the wear-property correlation. It was observed that the W_R was directly proportional to the product of interlaminar shear strength (I_s) and elastic modulus (E). Fairly good linearity was shown for specific wear rate (K₀) as a function of factor (μP/I_sE) where μ is coefficient of friction and P is the normal pressure (N/mm²).     

Effect of laser irradiation on abrasive wear of glass fibre polyester composite

Low power laser irradiation improves the wear resistance of glass-fibre-reinforced polyester composites, if irradiation time is restricted to short periods. Laser irradiation (i) enhances crosslinking in unsaturated polyester, (ii) modifies surface microstructure and (iii) increases the hardness of the composite material. Improved mechanical properties, in turn, increase the material's resistance to wear.     

Investigations on the influence of graphite filler on dry sliding wear and abrasive wear behaviour of carbon fabric reinforced epoxy composites

In this experimental study, the dry sliding wear and two-body abrasive wear behaviour of graphite filled carbon fabric reinforced epoxy composites were investigated. Carbon fabric reinforced epoxy composite was used as a reference material. Sliding wear experiments were conducted using a pin-on-disc wear tester under dry contact condition. Mass loss was determined as a function of sliding velocity for loads of 25, 50, 75, and 100 N at a constant sliding distance of 6000 m. Two-body abrasive wear experiments were performed under multi-pass condition using silicon carbide (SiC) of 150 and 320 grit abrasive papers. The effects of abrading distance and different loads have been studied. Abrasive wear volume and specific wear rate as a function of applied normal load and abrading distance were also determined.The results show that in dry sliding wear situations, for increased load and sliding velocity, higher wear loss was recorded. The excellent wear characteristics were obtained with carbon-epoxy containing graphite as filler. Especially, 10 wt.% of graphite in carbon-epoxy gave a low wear rate. A graphite surface film formed on the counterface was confirmed to be effective in improving the wear characteristics of graphite filled carbon-epoxy composites. In case of two-body abrasive wear, the wear volume increases with increasing load/abrading distance. Experimental results showed the type of counterface (hardened steel disc and SiC paper) material greatly influences the wear behaviour of the composites. Wear mechanisms of the composites were investigated using scanning electron microscopy. Wear of carbon-epoxy composite was found to be mainly due to a microcracking and fiber fracture mechanisms. It was found that the microcracking mechanism had been caused by progressive surface damage. Further, it was also noticed that carbon-epoxy composite wear is reduced to a greater extent by addition of the graphite filler, in which wear was dominated by microplowing/microcutting mechanisms instead of microcracking.     

Influence of weave of carbon fabric on low amplitude oscillating wear performance of Polyetherimide composites

Three composites were fabricated based on Polyetherimide (PEI) matrix and carbon fabric (CF) (55 vol.%) of different weaves, viz. plain, twill and satin (4H) by impregnation technique. These composites were evaluated for various mechanical properties and tribological performance in low amplitude oscillating wear (LAOW)/fretting wear mode. It was observed that CF reinforcement led to a significant enhancement in all strength and modulus properties of PEI except elongation to break (e). Twill weave proved to be the most effective followed by satin and plain weave in almost all the properties. The LAOW mode evaluation under various loads revealed that the wear performance order was exactly opposite to the above trend. Overall, plain weave composite was the best performer followed by twill and satin. Various wear mechanisms, such as fiber-matrix debonding due to repetitive reciprocating shearing stresses, micro-cracking, micro-cutting and pulverization of fibers followed by removal of debris from the contact zone were operative during such wear situation. Amongst these processes, generation of fiber debris, their temporary retention in fabric weaves and subsequent removal from the crater played a key role in overall wear performance. The ability of plain weave to hold back the debris was maximum that resulted in lowest wear while satin weave had the minimum retention ability that led to the highest wear. The proposed wear mechanisms were supported by SEM studies.     

Friction and dry sliding wear behavior of carbon and glass fabric reinforced vinyl ester composites

Friction and dry sliding wear behavior of glass and carbon fabric reinforced vinyl ester composites have been presented. The results show that the coefficient of friction and wear rate increased with increase in load/sliding velocity and depends on type of fabric reinforcement and temperature at the interphase. The excellent tribological characteristics were obtained with carbon fiber in vinyl ester. It is believed that a thin film formed on counterface was seems to be effective in improving the tribological characteristics. The worn surfaces examined through SEM, showed higher levels of broken glass fiber in vinyl ester compared to carbon-vinyl ester composites.     

Influence of weave structures on the tribological properties of hybrid Kevlar/PTFE fabric composites

The existing research of the woven fabric self-lubricating liner mainly focus on the tribological performance improvements and the service life raised by changing different fiber type combinations, adding additive modification, and performing fiber surface modification. As fabric composites, the weave structures play an important role in the mechanical and tribological performances of the liners. However, hardly any literature is available on the friction and wear behavior of such composites with different weave structures. In this paper, three weave structures (plain, twill 1/3 and satin 8/5) of hybrid Kevlar/PTFE fabric composites are selected and pin-on-flat linear reciprocating wear studies are done on a CETR tester under different pressures and different frequencies. The relationship between the tensile strength and the wear performance are studied. The morphologies of the worn surfaces under the typical test conditions are analyzed by means of scanning electron microscopy (SEM). The analysis results show that at 10 MPa, satin 8/5 performs the best in friction-reduction and antiwear performance, and plain is the worst. At 30 MPa, however, the antiwear performance is reversed and satin 8/5 does not even complete the 2 h wear test at 16 Hz. There is no clear evidence proving that the tensile strength has an influence on the wear performance. So the different tribological performance of the three weave structures of fabric composites may be attributed to the different PTFE proportions in the fabric surface and the different wear mechanisms. The fabric composites are divided into three regions: the lubrication region, the reinforced region and the bonding region. The major mechanisms are fatigue wear and the shear effects of the friction force in the lubrication region. In the reinforced region fiber-matrix de-bonding and fiber breakage are involved. The proposed research proposes a regional wear model and further indicates the wear process and the wear mechanism of fabric composites.     

Abrasive wear studies on composites of PEEK and PES with modified surface of carbon fabric

Carbon fabric (CF) being inert towards the matrix, the quality of its adhesion with the matrix is poor and hence, needs treatment to enhance fiber-matrix bonding. In this paper, cold remote nitrogen oxygen plasma (CRNOP) treatment to CF was employed to improve fiber-matrix adhesion. Composites were developed using CF with polyethersulphone (PES) and polyetheretherketone (PEEK) matrices. Performance enhancement due to CF treatment was quantified by improvement in mechanical and wear resistance (W_R) properties. A fairly good linearity was observed for specific wear rate (K₀×ILSS) as a function of a factor (μP/E).     

Influence of Concentration of Aramid Fabric on Abrasive Wear Performance of Polyethersulfone Composites

In this work, three composites of polyethersulfone (PES) containing Aramid (Kevlar 29) fabric with concentration 64, 72 and 83% (by weight) were developed by the compression molding technique. These composites were characterized for their mechanical and physical properties. The abrasive-wear performance of the composites was evaluated by abrading 1 × 1 × 1 cm³ samples against silicon carbide paper under various loads. The fabric reinforcement enhanced the abrasive-wear resistance of PES significantly (approximately 3–8 times depending on the operating conditions). It was observed that the 80% fabric composite showed the highest resistance to wear and impact along with the best tensile strength and elongation properties. Its flexural strength and ILSS value, however, were lowest. The 64% fabric composite, on the other hand, showed an exactly reverse trend among the three composites. Considering all the properties simultaneously, it was concluded that in the selected range of composites 72% fabric inclusion was the optimum for the best combination of tribological and mechanical properties. Ratner–Lancaster plots showed good linearity indicating that ultimate tensile strength and elongation to break were the prominent factors controlling the abrasive-wear behavior of the composites.     

Influence of reinforcement and lubrication on abrasive wear performance of polyamide

This paper presents the results of studies on the wear performance of various composites of polyamide (nylon 6,6) reinforced with short carbon fibres and lubricated with a solid lubricant, PTFE, under adverse sliding conditions (abrasive wear). The effects of increasing amounts of fillers, fibre orientation, and experimental parameters such as load, and abrading particle size were investigated. The studies revealed that fillers that are very much suitable for adhesive wear applications are detrimental for the abrasive wear mode. Moreover, wear performance showed deterioration with increasing amount of filler concentration. The combination of heterogeneous fillers proved to be detrimental for wear performance. Efforts were made to correlate these investigations with appropriate mechanical properties. It was found that wear performance was greatly influenced by selected experimental parameters. Worn surfaces were examined with SEM to have better insight of the wear mechanism.     

Modelling the effect of artificial weathering on abrasive wear behaviour of glass-polyester composites

Moisture absorption degrades interfacial strength and induces expansional strains in fibre-polymer composites. These strains subsequently affect the abrasive wear behaviour of composites subjected to boiling water treatment. A wear model is suggested, which quantitatively estimates the wear performance of boiling-water-treated glass-polyester composites. The theoretical model is in concurrence with experimental results.     

Influence of orientation and volume fraction of Aramid fabric on abrasive wear performance of polyethersulfone composites

In case of fabric reinforced composites of specialty polymers influence of orientation of fabric and its volume fraction on tribo-behaviour is sparingly studied. In our earlier work, we have reported on the influence of amount of Aramid fabric (AF) in polyethersulfone (PES) on abrasive wear performance. However, orientation effect of fabric with respect to abrading plane was not investigated. In this work three orientations of composites of PES containing Aramid (Kevlar 29) fabric with three concentrations 64, 72 and 83 wt.% were selected to study the influence on abrasive wear performance. Composites developed by compression molding technique were characterized for their mechanical and physical properties. The abrasive wear performance of the composites was evaluated by abrading 10 mm × 10 mm × 10 mm sample against silicon carbide (SiC) paper under various loads and two grades of abrasive papers. The fabric reinforcement enhanced the abrasive wear resistance of PES significantly (approximately 1.35–9.46 times depending on the operating conditions). It was observed that 83% fabric composite showed the highest resistance to abrasive wear and impact along with the best tensile strength and elongation properties. Its flexural strength and ILSS values, however, were the lowest. Sixty-four percent fabric composite, on the other hand, showed an exactly reverse trend among the three composites. Among the three orientations, fibres in normal and parallel (N–P) and normal and anti-parallel (N–AP) direction with respect to sliding plane proved to impart maximum wear resistance. N–P was best for light loads while N–AP was best for high loading conditions. Orientation parallel and anti-parallel (P–AP) was least beneficial in this respect. Moreover, the extent of improvement very much depended on the operating parameters such as grit size and load. Benefits endowed due to reinforcement were higher at less coarse grade paper. With increase in load, however, wear rate of composites with N–P orientation increased and for other two orientations it decreased. Thus, for severe operating conditions, N–AP orientation proved to be most beneficial. SEM studies proved supporting for understanding the influence of orientation on wear performance.     

Influence of abrading particle size on the wear performance of various polyamides

Various polyamides (PAs) containing different CONH₂/CH₂ ratios were selected for abrasive wear studies. Eleven types of silicon carbide (SiC) papers varying in particle size (10–175 μm) were selected as abrading counterfaces. The wear performance under single‐pass conditions indicated that the selected PAs did not show a size effect, in contrast to the case of metals and some other polymers. Wear rates were of the order of 2–17 × 10⁻¹¹ m³/Nm. Scanning electron micrographs of some of the worn papers indicated correlations between wear and the size and number of wear debris particles and the amount of material transferred to the papers.     

Influence of the normal force,abrasive slurry concentration and abrasive wear modes on the coefficient of friction in ball-cratering wear tests

The purpose of this work is to study the influence of the normal force (N), abrasive slurry concentration (C) and abrasive wear modes on the coefficient of friction in ball-cratering wear tests. Experiments were conducted with balls of AISI 52100 steel, an AISI H10 tool-steel specimen and abrasive slurries prepared with black silicon carbide (SiC) particles+distilled water. The tangential (T) and normal loads were monitored throughout the tests and the results have shown that: (i) the coefficient of friction behavior was independent of the normal force and (ii) both the concentrations of abrasive slurries and the subsequent action of the abrasive wear modes, generally, did not affect the behavior or magnitude of the coefficient of friction.     

Effect of working gap and circumferential speed on the performance of magnetic abrasive finishing process

Magnetic abrasive finishing (MAF) is one of the advanced finishing processes in which workpiece is kept between two magnets, and cutting force is controlled by working gap and magnetic field between the two magnets. MAF setup is designed for finishing cylindrical workpieces and it is mounted on lathe machine. The loosely bounded powder is prepared for experimentation by homogeneous mixing of magnetic powder (Fe powder of 300 mesh size (51.4 μm)), abrasive powder (Al₂O₃ of 600 mesh size (25.7 μm), and lubricant called servospin-12 oil. To investigate the effects of working gap and circumferential speed on material removal, change in surface finish and percent improvement in surface finish, a series of experiments have been conducted using in-house fabricated setup. Based upon the results, in general, material removal decreases by increasing working gap or decreasing circumferential speed of the workpiece. Change in surface finish increases by increasing circumferential speed of the workpiece.     

Influence of SiC, SiO2 and graphite on corrosive wear of bronze composites subjected to acid rain

Sintered aluminum bronze friction materials have been successfully used in clutches and breaks for heavy-duty applications, due to their good wear resistance, cold workability, fatigue resistance and corrosion resistance. The aim of the present work is the preparation and investigation of bronze-based composites for components subjected to motion in aqueous environments. Three of bronze-based composites with different amounts of slide additive (graphite) and friction additives (SiC, SiO₂) were prepared by powder metallurgy. The microstructure profiles of the obtained composite materials were characterized by uniform distribution of SiC, SiO₂ and graphite particles within the bronze matrix. The porosity decreased with increase in the number of pressing and sintering processes. High Vickers hardness values were registered for samples with higher reinforcement contents.A combination of electrochemical and gravimetric techniques was used in this study to assess corrosive wear rates of these materials under neutralized as well as acid rain conditions. Increasing both slide and friction additives improved the corrosion resistance of these bronze composites. Samples with 1.5% graphite, 3% SiO₂ and 3% SiC had the highest corrosive wear resistance in neutralized as well as in acid rain due to the high amount of anti-friction and slide additives, in addition to low porosity.     

Influence of solid lubricants and fibre reinforcement on wear behaviour of polyethersulphone

Polyethersulphone (PES), is an amorphous, brittle and high temperature engineering thermoplastic. Two composites of PES containing short glass fibres (GF) and solid lubricants viz. PTFE and MoS₂; and two composites containing short carbon fibre (CF) [30% and 40%] were selected for the present studies. Compositional analysis of selected materials was done with various techniques such as gravimetry, solvent extraction and thermal analysis viz. thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). These materials were studied for adhesive and abrasive wear performance by sliding against a mild steel disc and silicon carbide abrasive paper respectively, under different loads. It was observed that GF reinforcement along with incorporation of solid lubricants (PTFE and MoS₂) enhanced the wear performance of PES by an order of two. In the case of solid lubricants, PTFE proved to be more beneficial than MoS₂. CF reinforcement, however, proved to be the most effective in enhancing wear performance of PES. PES reinforced with 40% CF exhibited a specific wear rate in the order of 10⁻¹⁶m³/Nm which is considered to be very good for the thermoplastic composite. In the case of abrasive wear behaviour, however, incorporation of fibres or solid lubricants deteriorated the performance of the neat matrix. SEM was employed to investigate the wear mechanisms.     

Micro-scale abrasive wear testing of duplex and non-duplex (single-layered) PVD (Ti,Al)N, TiN and Cr–N coatings

A micro-scale abrasive wear test, based on ball-cratering, has been used to evaluate the wear resistance of duplex and non-duplex (Ti,Al)N, TiN and Cr–N coatings. The term duplex is used here when plasma nitriding is followed by PVD coating. Coatings without the plasma nitriding stage are termed single-layered. Coating properties were evaluated by surface profilometry, hardness and scratch testing. All duplex coatings showed higher micro-abrasive wear resistance than their single-layered counterparts, with the duplex (Ti,Al)N coating achieving the best performance. After a certain number of ball revolutions, the coating material became worn through, exposing the substrate material. After this point, the presence of a hard nitrided case diminished the scratching action of the SiC abrasive particles. The experimental results also indicate that the choice of the PVD coating plays an important role in improving the micro-abrasive wear resistance. Apart from single-layered and duplex Cr–N coatings, all the other coating systems provided a higher micro-abrasive wear resistance than the uncoated substrate (hardened AISI H13 steel). The poor abrasive wear resistance recorded for the single-layered and duplex Cr–N coatings could be attributed to the hardness of the Cr–N being much lower than that of the SiC abrasive particles, which caused tearing of the coating with subsequent delamination. The wear pattern observed was found to change from surfaces characterised by grooves (uncoated substrate, single-layered TiN and Cr–N systems and duplex Cr–N system) to surfaces which exhibited multiply indented surfaces (single-layered and duplex (Ti,Al)N systems), indicating a transition between wear mechanisms. This transition was found to be dependent on the ratio between the hardness of the SiC abrasive particles and surface (coating) or subsurface hardness. By decreasing this ratio, the ability of the SiC abrasive particles to scratch the composite surface was reduced and the resistance to micro-scale abrasion was improved.     

PCD刀具超声振动切削金属基复合材料SiCp/Al的特性研究

试验研究了普通和超声切削新型颗粒增强金属基复合材料SiCp/Al的切削特性 ,得到超声振动切削该材料的切屑形态、切削力变化规律     

Study on the tribological behavior of hybrid PTFE/cotton fabric composites filled with Sb2O3 and melamine cyanurate

The tribological behavior of the hybrid PTFE/cotton fabric composites filled with microsize Sb₂O₃ and melamine cyanurate (MCA) was investigated. It was found that the wear rate of the hybrid PTFE/cotton fabric composites decreased when Sb₂O₃ was used as the filler but increased with MCA filler. It was also observed that hybrid fillers (consists of Sb₂O₃ and MCA) had a wear reduction effect on the hybrid PTFE/cotton fabric composites at lower loads but increased the wear rate at higher loads. The wear behavior of the composites was explained in terms of the topography of worn surfaces and transfer film formed on the counterpart pin.