Solid particle erosion of unidirectional fibre reinforced thermoplastic composites

In the present study, the solid particle erosion behaviour of neat PEEK matrix and unidirectional glass fibre (GF) and carbon fibre (CF) reinforced polyetheretherketone (PEEK) and polyetherketoneketone (PEKK) composites has been studied. The erosion experiments have been carried out by using silica sand particles (200 ± 50 μm) as an erodent. Steady state erosion rates of these composites have been evaluated at different impact angles and impact velocities. The neat PEEK exhibited peak erosion rate at 30° impingement angle whereas the composites exhibited a semi-ductile behaviour with peak erosion rate at 60° impact angle. The erosion rate of the glass fibre reinforced composites was higher than that of the carbon fibre reinforced composites. The results show that the fibre orientation has a significant influence on erosion rate only at lower impact angles. The erosion rate of the composites was higher when the particles impact perpendicular to the fibre direction than parallel to the fibres. The morphology of eroded surfaces was observed under scanning electron microscope and damage mechanisms were discussed.     

Investigation on solid particle erosion behaviour of polyetherimide and its composites

The present investigation reports about, the solid particle erosion behaviour of randomly oriented short E-glass, carbon fibre and solid lubricants (PTFE, graphite, MoS₂) filled polyetherimide (PEI) composites. The erosion rates (ERs) of these composites have been evaluated at different impingement angles (15–90°) and impact velocities (30–88 m/s). Mechanical properties such as tensile strength (S), ultimate elongation to fracture (e), hardness (H_V), Izod impact strength (I) and shear strength (S_s) seems to be controlling the erosion rate of PEI and its composites. Polyetherimide and its glass, carbon fibre reinforced composites showed semi-ductile erosion behaviour with peak erosion rate at 60° impingement angle. However, glass fibre reinforced PEI composite filled with solid lubricants showed peak erosion rate at 60° impingement angle for impact velocities of 30 and 88 m/s, whereas for intermediate velocities (52 and 60 m/s) peak erosion rate observed at 30° impingement angle. It is observed that 20% (w/w) glass fibre reinforcement helps in improving erosive wear resistance of neat PEI matrix. Erosion efficiency (η) values (0.23–8.2%) indicate micro-ploughing and micro-cutting dominant wear mechanisms. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms are discussed.     

Solid particle erosion of unidirectional carbon fibre reinforced polyetheretherketone composites

The solid particle erosion behaviour of unidirectional carbon fibre (CF) reinforced polyetheretherketone (PEEK) composites has been characterised. The erosion rates of these composites have been evaluated at different impingement angles (15–90°) and at three different fibre orientations (0, 45, and 90°). The particles used for the erosion measurements were steel balls with diameter of 300–500 μm and impact velocities of 45 and 85 m/s. The unidirectional CF reinforced PEEK composites showed semi-ductile erosion behaviour, with maximum erosion rate at 60° impingement angle. The fibre orientations had a significant influence on erosion rate. The morphology of eroded surfaces was examined by using scanning electron microscopy (SEM). Possible erosion mechanisms are discussed.     

Effect of Resin-Derived Carbon on the Friction Behavior of Carbon/Carbon Composites

Three different C/C composites with rough laminar (RL) pyrocarbon, RL pyrocarbon with added resin-derived carbon, and pure resin-derived carbon have been evaluated and tested for friction performance. A laboratory dynamometer was used to simulate different braking speeds utilizing a single stator and rotor pair. The morphologies and microstructures of the raw materials, wear surfaces, and wear debris at different braking levels were observed by polarized light microscopy, scanning electron microscopy, and transmission electron microscopy. The results have shown that the friction coefficients of the three C/C composites display the same characteristics with increasing braking speed. They increased to a maximum value at medium braking speed and thereafter decreased with increasing braking speed, and their mean values under the same braking conditions were similar. The C/C composite with pure resin-derived carbon showed the highest loss due to wear under all conditions, while the C/C composite with the RL pyrocarbon showed the lowest loss. Resin-derived carbon in C/C composites does not have a significant effect on the friction coefficient, but the wear rate increases greatly with increasing resin-derived carbon content. Wear debris is composed of flocculent particles with polycrystalline structure, along with the matrix carbon, which is worn off directly from the composites.     

Solid particle erosion of CFRP composite with different laminate orientations

The solid particle erosion behavior of epoxy base unidirectional and multidirectional carbon fiber reinforced plastic composites was investigated. The erosion rates of these composites were evaluated at various impingement angles (15–90°) with a particle velocity of 70 m/s. Irregular SiC particles with an average diameter of 80 μm was used. The dependence of impingement angle on the erosive wear resembled the conventional ductile behavior with maximum erosion rate at 15–30° impingement angle. The erosion rate of unidirectional composites at acute impingement angle was higher for [90] than for [45] and [0] while the difference disappeared at normal impingement angle (90°). On the other hand, the erosion rates of multidirectional laminated composites ([0/90], [45/−45], [90/30/−30] and [0/60/−60]) were not much influenced by the fiber orientation except for 15° impingement angle.     

聚焦光束堆焊生成陶瓷颗粒增强的复合材料表层

研究了在碳钢表面光束堆焊生成陶瓷颗粒增强复合材料表层的可行性，考察了陶瓷颗粒物理性能及其加入量等对复合材料表层质量的影响规律。试验结果表明：陶瓷颗粒的密度及其与基体NiCrBSi合金间的润湿性对复合材料表层的成形有重要影响，与普通TiC及WC相比，由于WC/Ni及NiCrBSi合金的润湿性好，因此更适合用作以镍基合金为基的复合材料表层的颗粒增强相，在复合材料表层成形良好的前提下，增加陶瓷颗粒的加入量有利于复合材料表层宏观硬度的提高。     

Impact Abrasive Wear Response of Carbon/Carbon Composites at Elevated Temperatures

Three types of carbon/carbon composites were fabricated using pitch as matrix material. Performance of these composites was evaluated under continuous impact abrasion tests (CIAT). Towards this purpose, a novel testing equipment was designed and developed at AC²T. Tests were carried out at room temperature and 500 °C. The angle of impact was chosen to be 45° and 90°. Analysis of tribological performance was carried out by mass loss. Characterization of the worn surface was done by means of scanning electron microscopy (SEM) and optical 3D profilometry. In this work, it was shown that wear rates are higher for 45° impact angle compared to 90° for all composites investigated. Fibre debonding and fibre pull out was observed to be the dominating wear mechanisms for these composites during CIAT procedure under normal impact abrasion. Removal of chunk of material contributes to wear under oblique impact abrasion.     

Wear Performance Forecasting of Chopped Fiber–Reinforced Polymer Composites: A New Approach Using Dimensional Analysis

Solid particle erosion of polymer matrix composites is a complex process in which wear occurs from the target surface by impingement of rigid sand particles in an air medium. The rate of material removal (RMR), also referred to as the erosion rate, mainly depends on target material parameters and the erosion conditions such as impact angle, impact velocity, and erodent size. A new semi-empirical model for prediction of the erosion rate of polymer matrix composites has been developed using a dimensional analysis technique based on Buckingham's π theorem. The predictive model analytically rests upon parameters related to chopped glass fiber composites, erodent (target material properties), and operating variables that mainly affect the erosion process of chopped glass fiber–vinyl ester resin composites. The forecasting ability of the predictive model has been assessed and verified by experimental investigations for chopped glass fiber–reinforced vinyl ester resin (VGF) composites. Validation of the theoretical erosion rates obtained from the predictive model showed that they were in good agreement with the experimentally determined erosion rates, where the average error range was estimated to be ～10 to ～20%.     

Solid particle erosion studies on polyphenylene sulfide composites and prediction on erosion data using artificial neural networks

Solid particle erosion behavior of polyphenylene sulfide, reinforced by short glass fibers with varying fiber content (0–40 wt%) has been studied. Steady-state erosion rates have been evaluated at different impact angles (15–90°) and impact velocities (25–66 m/s) using silica sand particles (200 ± 50 μm) as an erodent. PPS and its composites exhibited maximum erosion rate at 30° impact angle indicating ductile erosion behavior. Though PPS is a brittle thermoplastic, incubation period was found for neat resin and its composites at normal impact (α = 90°). The erosion rates of PPS composites increased with increasing amount of glass fiber. Morphology of eroded surfaces was examined using scanning electron microscopy (SEM) and possible wear mechanisms were discussed. Also, artificial neural networks (ANNs) technique has been used to predict the erosion rate based on the experimentally measured database of PPS composites. The results show that the predicted data are well acceptable when comparing them to measured values. A well-trained ANN is expected to be very helpful for prediction of wear data for systematic parameter studies.     

Erosive Wear Mechanism of New SiC/SiC Composites by Solid Particles

A solid-particle erosive wear test by impinging silicon carbide (SiC) powders was carried out at room temperature over a range of median particle sizes of 425–600 μm, speed of 100 m/s and impact angle of 90° and assessed by wear measurements and scanning electron microscopy. Erosive wear behaviour was examined on newly fabricated nano-powder infiltration and transient eutectoid (NITE) SiC/SiC composites and two commercial composites by the chemical vapour infiltration (CVI) and NITE fabrication route. Microstructural observation was performed to examine the correlation between erosive wear behaviours and fabrication impurities. Conspicuous defects were observed in the prototype materials as the forms of porosity, fibre deformation, residual oxide, pyrolytic carbon (PyC) deformation, PyC cleavage, among others. Erosive wear behaviour was rather serious in the prototype of fabricated composites, which employ pre-SiC fibre and phenolic resin. Two dominant erosive wear mechanisms were observed: delamination of constituents, mainly caused by erosive crack propagation, and fragmentation and detachment of constituents, which usually resulted from erosive impact. A unit size of delamination was the most decisive factor affecting wear volume. The bonding strength of each constituent was mostly affected by various forms of porosities. Therefore, the fundamental cause and subsequent results must be carefully elucidated. The correlation of microstructural defect and wear behaviour was investigated with the aim of reducing dominant wear by improving fabrication conditions. The final product of the cost-effective composite had a 2.5-fold higher resistance than the commercial CVI composite. Consequently, by controlling fabrication impurities, we have been successful in developing and improving a new fabrication technique; consequently, the known defects are rarely observed in final product. A schematic wear model of erosive wear mechanisms is proposed for the newly fabricated SiC/SiC composites under particle erosion.     

溶胶-凝胶法制备碳纳米管/SiO_2复合材料过程的TG-DSC-MS研究

利用热重 -差示扫描量热 -质谱 ( TG-DSC-MS)联用技术对溶胶 -凝胶 ( Sol-Gel)法热压烧结制备碳纳米管 ( CNT) /Si O2 复合材料过程中的热分解行为特性进行了表征研究。采用多离子检测模式预定测量热分解生成的 C+ ( m/z1 2 )、OH+ ( m/z1 7)、H2 O+ ( m/z1 8)、CO2 + ( m/z2 8)等 9种正离子。实验发现 :用溶胶 -凝胶法制备 CNT/Si O2 复合材料过程中 ,在 5 0 0℃以下生成 Si O2 ,CNT在 5 0 0～ 73 0℃左右氧化燃烧。在 5 0 0℃条件下煅烧 1 h,凝胶 Si O2 完全转变成玻璃粉。选择在 5 0 0℃条件下煅烧 CNT/Si O2 复合粉体 1 h可作为CNT/Si O2 复合材料的煅烧工艺     

预制体添加BN对炭/炭复合材料性能的影响

在炭纤维预制体中添加六方氮化硼(h-BN),采用等温化学气相渗透(CVI)和超高压沥青浸渍/碳化混合工艺制备了炭/炭(C/C)复合材料。研究了材料的组织结构和力学性能,采用XD-MSM定转速摩擦试验机对材料的摩擦磨损性能进行了测试;分析了h-BN含量对摩擦磨损性能的影响。实验表明:预制体添加h-BN可以明显降低材料的摩擦系数,稳定材料的摩擦磨损性能。其中以9wt%时,材料的摩擦磨损性能最佳。     

Solid particle erosion studies on biomorphic Si/SiC ceramic composites

Solid particle erosion tests were conducted on four different types of silicon carbide ceramic composites. The composites are cotton fabric based Si/SiC with and without chemical vapour infiltration, fine teak wood powder based Si/SiC and coarse teak wood powder based Si/SiC. The erodents used are angular SiC particles of average size 80, 250 and 450 μm. The velocities with which particles impacted on the target materials were varied from 20 to 50 m/s. Similarly the angle of impact was varied from 20° to 90°. Scanning electron microscopic observations on the eroded surface show brittle and cleavage like fracture. Fine teak wood powder based Si/SiC ceramic shows better erosion resistance than the other ceramics. Homogenous distribution of SiC grains with the presence of very fine grains of silicon and carbon is responsible for the improved erosion resistance. The higher erosion rate in cotton fabric based SiC arises from its microstructure. Here, the free carbon and free silicon grains are large in size and the SiC phase has very low hardness as compared to the erodent.     

Impact of stacking sequence on tribological wear performance of woven jute-glass hybrid epoxy composites

Natural fibre-reinforced plastic (FRP) composites have gained much interest because of their environment friendliness and cost-effectiveness compared to synthetic fibre-reinforced composites. The availability of natural fibre and ease of manufacturing have tempted researchers worldwide to develop a locally available low-cost fibre and study their feasibility for reinforcement purposes and to what extent they can satisfy the required specifications of well-reinforced polymer composite for tribological application. FRP composites have various applications in the automobile, aerospace and marine fields. They are applied to inlet cone, fan exit guide vanes and other parts of structures in a turbofan engine for lightening an engine. The erosion characteristics of the FRP composites are of vital importance due to the operational requirements in dusty environments. In this present work, the impact of stacking sequence on erosion wear behaviour of untreated woven jute and glass fabric-reinforced epoxy hybrid composites has been investigated experimentally. The orientation of glass and jute fabric was kept at (0°–90°) and (45°–45°) for all stacking sequences. All the laminates were prepared using four plies, and, the number and position of glass layers were varied so as to obtain four different stacking sequences. The erosion rate of these composites were evaluated at different impingement angles (30°–90°) at three different impact velocities (V = 48, 70, 82 m/s). Silica sand was used as the erodent. Our results showed that the impingement angle had a significant influence on the erosion rate. The composite materials showed semi-ductile behaviour with the maximum erosion at an impingement angle of 60°. The morphologies of the eroded surface were observed by a scanning electron microscope, and the possible erosion mechanisms were discussed.     

Effect of reinforcement coatings on the dry sliding wear behaviour of aluminium/SiC particles/carbon fibres hybrid composites

Dry sliding wear of an AA 6061 alloy reinforced with both modified SiC particles and metal coated carbon fibres has been studied. SiC particles were used to increase the hardness of the composite while short carbon fibres are supposed to act as a solid lubricant. SiC particles were coated with a silica layer deposited through a sol–gel procedure to increase the processability of the composite and to enhance the particle–matrix interfacial resistance. The metallic coatings on carbon fibres were made of copper or nickel phosphorus which was deposited through an electroless process. The metallic coatings favoured the wetting of the fibres during processing and then dissolved in the aluminium matrix forming intermetallic compounds that increased its hardness. Wear behaviour of AA 6061–20%SiC and AA 6061–20%SiC–2%C was compared with that of the composites with the same reinforcement content but using coated particles and fibres. The influence that the modification of the matrix because of the incorporation of coatings on the reinforcements had on the mild wear behaviour was investigated. The wear resistance of the composites increased when carbon fibres were added as secondary reinforcement and when coated reinforcements were used.     

Role of Nano-YbF3-Treated Carbon Fabric on Improving Abrasive Wear Performance of Polyetherimide Composites

A method for surface treatment of carbon fabric with nano-particles of rare earth salt (ytterbium fluoride–YbF₃) was tried first time in the authors’ laboratory to enhance the fiber–matrix interface, and has been reported here. In this article authors have reported on the performance evaluation of composites developed from the four fabrics treated with various doses viz. 0, 0.1, 0.3, and 0.5 wt% of YbF₃. The abrasive wear performance of these composites was evaluated by abrading the composites against silicon carbide abrasive paper under varying loads. The treated fabric composites exhibited lower coefficient of friction and higher wear resistance as compared with untreated fabric composite. A linear correlation between ILSS (interlaminar shear strength) and wear resistance was observed. Both were the highest for 0.3% dosing of fabric. Since it was also desirable to compare the efficiency of this novel method of treatment of carbon fibers with conventional one, a few results of composites with plasma-treated carbon fabric were compared with the nano-particle-treated fabric composites. It was concluded that the latest method improved the abrasive wear resistance of composites almost two times more than the plasma-treated composites. Fiber–matrix interface was strengthened because of the treatment as observed from SEM studies, ILSS, and matrix pick-up studies. Increased roughness of fiber surface was observed in topographical analysis by SEM. Effect of treatment on fiber was also observed by adhesion test and fiber tow tension test. SEM studies of worn surfaces were performed to understand wear mechanisms.     

Impact wear resistance of WC/Hadfield steel composite and its interfacial characteristics

A composite coating of WC/Hadfield steel was fabricated through centrifugal casting process to improve the impact wear resistance of Hadfield steel under the conditions of low or medium impact energy. The interfacial structure between WC ceramic particle and the steel matrix was analyzed with scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The impact wear tests at different impact energy were carried out on a MLD-10 type impact wear rig to investigate the wear-resistant properties of three kinds of composites with different WC particle sizes. For comparison, the wear tests of Hadfield steel were also carried out under the same conditions. The results show that WC particles are partially dissolved in the steel during centrifugal casting. The elements W, C and Fe in steel react to form new carbides such as Fe₃W₃C or M₂₃C₆, which precipitate around former WC particles forming fine particles during subsequent solidification. So the interface between WC particles and Hadfield steel matrix is a strong metallurgical bonding. The composite reinforced with smaller WC particles has better impact wear resistance than that of Hadfield steel regardless of impact energy level. Whereas, the composite reinforced with larger WC particles has better impact wear resistance property than that of Hadfield steel when the impact energy is small but an opposite result is gained when the impact energy is higher. So, it is very essential to choose suitable size of WC particles as reinforcement in Hadfield steel to make the composite material more durable in the service conditions.     

碳纳米管直径对丁腈橡胶复合材料性能影响的分子模拟

利用分子动力学模拟研究碳纳米管(CNTs)直径改变时对丁腈橡胶(NBR)基体力学及摩擦学性能的影响。采用恒应变法考察不同复合材料模型的力学性能，结果表明复合材料力学性能随着NBR基体中CNTs直径增大呈现先增加后减小的趋势。剪切模拟结果表明，剪切后复合材料基体中分子链发生了不同程度的断裂，出现了聚合物分子链向摩擦界面聚集的现象，其中较大直径CNTs增强NBR复合材料中分子链相对完整连续，摩擦学性能改善效果更好。较大直径CNTs对NBR基体具有显著的增强效果，限制了NBR分子链的活动能力，更多的分子链聚集在CNTs周围，复合材料体系致密性及稳定性提高，从而改善了CNTs/NBR复合材料力学及摩擦学性能。其中直径(6,6)CNTs增强NBR复合材料具有更高的剪切模量，力学性能优异，表现出了更好的摩擦磨损性能。     

A review of the performance of engineering materials under prevalent tribological and wear situations in South African industries

The wear of materials used on machinery operating in a wide range of industrial situations such as mining, energy production and agriculture can cause serious inefficiencies, sudden breakdowns and consequential financial losses. Our work over two decades has concerned industrial problems encountered in South African industry, and laboratory simulations of abrasion, abrasion plus corrosion, adhesive wear, impact wear, cavitation, solid particle erosion and erosion plus corrosion situations have been successfully undertaken. Materials investigated include plain carbon and alloy steel, stainless steels, aluminium alloys, cast irons, tungsten carbide cermets, ceramics, polymers, composites and various surface treated and coated materials. The paper reviews the investigations carried out in our laboratories and conclusions we have made.     

Abrasive wear behaviour of B4C particle reinforced Al2024 MMCs

In this study, the effects of volume fraction and particle size of boron carbide on the abrasive wear properties of B₄C particle reinforced aluminium alloy composites have been studied. For this purpose, a block-on-disc abrasion test apparatus was utilized where the samples slid against the abrasive suspension mixture at room conditions. The volume loss, specific wear rate and roughness of the samples have been evaluated. The effects of sliding time, particle content and particle size of B₄C particles on the abrasive wear properties of the composites have been investigated. The dominant wear mechanisms were identified using scanning electron microscopy. The results showed that the specific wear rate of composites decreased with increasing particle volume fraction. Furthermore, the specific wear rate decreased with increasing the size of particle for the composites containing the same amount of B₄C. Hence, it is deduced that aluminium alloy composites reinforced with larger B₄C particles are more effective against the abrasive suspension mixture than those reinforced with smaller B₄C particles.