Investigation of erosive wear behavior and physical properties of SGF and/or calcite reinforced ABS/PA6 composites

The aim of this study was to investigate the erosive wear behavior of glass fiber, CaCO₃ particle and glass fiber/CaCO₃ hybrid reinforced ABS/PA6 blend based composites. The samples were prepared by using melt mixing and injection molding techniques. The mechanical, thermal, morphological properties and erosive wear behavior were investigated in terms of reinforcing agent type and composition. It was observed that the tensile strength and modulus values of hybrid composites gave a value between tensile strength and modulus values of only fiber reinforced composites and only particle reinforced composites. From DSC analysis it was revealed that T_g and T_m of composites were not significantly affected by reinforcement; however, degree of crystallinity was found to be sensitive to reinforcement type and composition. The impingement angle was found to have a significant effect on the erosive wear behavior. The results indicated that composite materials exhibited maximum erosion rate at impact angle of 30° conforming their ductile erosion behavior. In order to investigate wear mechanisms, eroded surface analysis was done by scanning electron microscopy. Surface analysis showed that repeated impact of hard silica sand particles caused a local removal of the matrix from the fiber surface and led to form craters on the surface of the composite material.     

Influence of annealing duration on the erosive wear behavior of polyphenylenesulphide composites

The influence of annealing duration on the erosive wear behavior of short glass fiber (40% w/w) and CaCO₃ mineral particulate (25% w/w)–short glass fiber (40% w/w) (total: 65% w/w) reinforced PPS composites has been characterized under various experimental conditions by differential scanning calorimetry (DSC) and erosion measurements. The erosive wear of the composites have been evaluated at different impingement angles (30, 45, 60, and 90°) and at four different annealing periods (30, 60, 90, and 120 min). Increase in the total crystallization causes an improvement in the erosive wear properties of the samples. Annealing time controls the morphology by influencing the degree of crystallinity in the matrix and in the fiber–matrix interface. This formation restricts fiber–matrix debonding. There is no linear proportionality between annealing time and relative degree of crystallization. The results indicate that PPS composites show maximum in wear versus impact angle relation at 60° confirming their semi-ductile failure behavior. The morphologies of eroded surface are examined by the scanning electron microscope.     

超高分子量聚乙烯的冲蚀磨损

用气流喷砂到冲依试验装置测试了超高分子量聚乙烯（UltraHighMolecularWeightPolyethylen）的冲蚀磨损佳能．考察了冲蚀粒子的入射角、速度、粒子的硬度对冲蚀磨损的影响．用扫描电子显微镜观察冲蚀后报表面形统指出：在高角冲蚀时，摩根机理主要为塑性变形和显微裂纹；在低角冲蚀时，磨损机理主要为显微切削和显微犁耕．冲蚀磨损机理与冲蚀粒子有关．     

ZrO_2－Al_2O_3－SiC系复相陶瓷材料的冲蚀磨损

本文对ＺｒＯ２增韧１０％ＳｉＣ／Ａｌ２Ｏ３基复合材料和ＳｉＣ颗粒弥散强化５％Ａｌ２Ｏ３／ＺｒＯ２基复合材料的冲蚀磨损的研究，实验表明：相交增初有助于断裂韧性的改善，从而缓和了材料的高角冲蚀率；高弹模量的ＳｉＣ二相粒子引入后基体材料的硬度增加，提高了材料的抗低角磨损能力．显微结构（ＳＥＭ）分析表明，不同的冲蚀角度条件下材料表面的损伤行为和磨损微观机制也不相同，通过ＰＵＤ计算，定量表征材料的抗切向磨损能力．     

Effect of CNTs addition on the erosive wear response of epoxy resin and carbon fibre composites

In the current study we investigated the effect of carbon nanotubes (CNTs) addition on the erosive wear response of epoxy resin and carbon fibre reinforced laminates (CFRPs) and demonstrated the positive synergy of CNTs and carbon fibres, which resulted in almost 50% decrease of the erosion rate (ER) of the CFRPs at high impact angles (90°). Incorporation of CNTs led in slight increase of the ER of the epoxy systems, especially at low impact angles. The relative fibre orientation in the CFRPs had a negligible effect on the erosive wear response mainly due to the quasi isotropic nature of the tested CFRPs. Based on the erosion efficiency parameter the response of the epoxy systems was characterised as semi-brittle, while CFRPs behaved in a brittle manner. Scanning electron micrograph provided evidence that the presence of CNTs reduced the amount of broken and/or detached fibres in the case of CFRPs.     

Erosive and abrasive wear resistance of overlay coatings

In the paper, the erosion and abrasion resistance of PTA, TIG and flame deposited coatings was investigated. Hardness of coatings has almost no effect on erosion resistance and incubation period. Microstructure of coatings has significant effect on erosive wear of coatings. No significant correlation was found between results of abrasive and erosive tests. Statistically significant correlation was found between erosive wear intensities determined in tests carried out at similar angles, the total content of B and C correlates with mass loss in abrasion test and erosive wear intensity at normal incidence. Laboratory tests with model abrasives cannot be used as a guide for material selection in industry.     

Erosion wear response of ramie-epoxy composites using artificial neural network integrated with Taguchi technique

This paper aims on evaluating the erosion wear behavior of epoxy composites reinforced with ramie fibers. The possibility of reinforcing ramie fiber to improvise the wear resistance of epoxy is investigated in this study. Composites are fabricated by reinforcing multiple layers of woven ramie fiber mats into epoxy resin using conventional wet lay-up technique and erosion wear trials are conducted using solid particle erosion test setup. Taguchi analysis is done to assess the relative significance of each of the factors influencing the erosion rate using L₁₆ orthogonal array. The analysis reveals that the impact velocity followed by impingement angle are the most significant control factors affecting the erosion wear rate of ramie-epoxy composites. Steady state erosion analysis is done to ascertain the effect of each of the significant factors while keeping other factors fixed. Further, an analytical and predictive model based on the principle of neural computation is used to predict the rate of erosion wear of the composites and the obtained results are compared with the experimental outcomes. The worn morphologies of the eroded surfaces of the composites are studied and analyzed to identify possible mechanisms causing wear.     

Erosion mechanisms of aluminium nitride ceramics at different impact angles

In this paper, erosion wear behaviour of aluminium nitride (AlN) ceramics is studied. The influence of particle hardness and shape on erosion of the AlN surface is examined. The effect of varying the impingement angle on the weight loss and the roughness parameters of AlN ceramics testing sample is also determined. Therefore, erosive wear behaviour of AlN ceramics was investigated using SiC and SiO₂ particles as erodents, at following impact angles: 30°, 45°, 60°, 75° and 90°. Scanning electron microscopy (SEM) was used to analyze the eroded surfaces in order to determine erosion mechanisms. The roughness parameters (R_a, R_z and R_max), before and after erosion with SiO₂ and SiC particles at 30° and 90° angles of impingement, respectively, were determined using a profilometer. It was found that the impact angle is influencing the erosion wear of the AlN ceramics and maximum erosion takes place at impact angle of 90°. The results indicate that hard, angular SiC particles cause more damage than softer, more rounded SiO₂ particles.     

考虑孔隙缺陷的CFRP微观切削仿真与实验研究

碳纤维增强树脂基复合材料(CFRP)在航空航天等领域应用广泛。在CFRP制造过程中难以避免会产生孔隙等缺陷,对后续的切削加工造成一定影响。在考虑了CFRP成型过程形成的孔隙缺陷基础上,运用有限元仿真模拟方法,从纤维-树脂-界面尺度建立了含孔隙缺陷的CFRP微观切削仿真模型,研究了不同孔隙率条件下不同纤维排布方向的CFRP微观切削行为,并通过实验验证了仿真模型的正确性。研究结果表明:孔隙的存在会增加刀具的“空切”现象,从而对CFRP切削过程的切削力、材料破坏及亚表面损伤、材料能量等产生影响。随孔隙率的增加,切削力呈下降趋势,孔隙边缘的纤维产生整体断裂的倾向增加;孔隙对0°、45°和135°纤维排布方向的CFRP切削加工的面下损伤影响不大,在纤维排布方向为90°条件下,孔隙率高于3vol%时对加工表面的面下损伤具有较大影响;在材料内部能量耗散方面,“顺切”(纤维方向角小于90°)时的总耗散能低于“逆切”,随孔隙率增加,总耗散能降低。      

Erosion of polymers and polymer composites surfaces by particles

Surface erosion due to solid particle impact is a major concern in engineering applications of handling solid-particulate flow. A semi-empirical model is developed for numerical erosion simulation of polymers and polymer composites. The novelty of the developed model is the correct capturing of the angle of maximum erosion for different erosion modes of polymeric materials and relating it to measurable mechanical properties of the target materials. The model incorporates both the material removal due to elastic–plastic collision of the particles at oblique and normal impact angles. The oblique impact model is derived for ploughing and fracture governed mechanisms of material removal. A simplified correlation is used to consider the relative effect of each mechanism on the total erosion at oblique impact angles. The model indicates the variation in velocity exponent to the mechanism of material removal. The theoretically derived model for single-particle impact is correlated to the available experimental results of multi-particle impacts through the empirical coefficients. The predictions are in good agreement with the extensive literature data for polymers and polymer composites. Further, to propose a single model of erosion for polymer and its composite, the relationship between the empirical coefficients in the developed model and the target material properties is established.     

Multiscale finite element modeling of failure process of composite laminates

A multiscale nonlinear finite element modeling technique is developed in this paper to predict the progressive failure process for composite laminates. A micromechanical elastic–plastic bridging constitutive model, which considers the nonlinear material properties of the constituent fiber and matrix materials and their interaction and the damage and failure in fibrous composites at the fiber and matrix level, is proposed to represent the material behavior of fiber-reinforced composite laminates. The micromechanics constitutive model is employed in the macroscale finite element analysis of structural behavior especially progressive failure process of the fiber-reinforced composites based on a 4-node 24-DOF shear-locking free rectangular composite plate element.     

Prediction of tensile strength of discontinuous carbon fiber/polypropylene composite with fiber orientation distribution

This study proposes the layer-wise method (LWM) as a new approach for predicting the tensile strength of discontinuous fiber-reinforced composites that have arbitrary fiber orientation angles. The LWM assumes the discontinuous fiber-reinforced composites are identical to laminates that are composed of unidirectional fiber-reinforced plies and have the same distribution of fiber angles over the entire laminate. We applied the LWM to discontinuous carbon fiber polypropylene composites and evaluated the effect of fiber length on tensile strength and fracture mode. Simulated results agreed well with those of experiments. In addition, we proposed a simple analytical model based on micromechanics. This analytical model can correctly evaluate the strength and the fracture mode as effectively as the LWM. We also compared these models with a rule of mixture considering the failure criterion of fiber breakage and examined the limitation of the rule of mixture in predicting composite strength.     

Effect of post-sintering heat-treatments on the erosive wear behaviour of liquid-phase-sintered aluminas

The influence of microstructure on the indentation-strength and solidparticle erosive wear behaviour of a liquid-phase-sintered (LPS)alumina subjected to coarsening, quenching and crystallisationheat-treatments were investigated. Strength as a function of cracksize using Vickers indentations of varying loads was assessed. Theshort-crack toughness curves (T-curves) of the materials wereevaluated from indentation-strength data which is pertinent to wearproperties, since wear is governed by fracture characteristics atsmall flaw sizes. The effects of impact angle and particle velocityon erosive wear rates were also analysed. The relationship betweenshort-crack toughness behaviour and erosion resistance are discussedwith reference to the material microstructures and phase composition.     

Fiber-reinforced composites with polymer-derived matrix: processing,matrix formation and properties

Carbon and SiC fiber-reinforced ceramic matrix composites were prepared via infiltration of fiber preforms using the polymer infiltration technique and polymer pyrolysis. Suitable silazane (SiCN) precursors with appropriate thermosetting behavior, viscosity and ceramic yield were synthesized, starting from functionalized chlorosilanes. Microstructural development and fracture behavior was studied after various infiltration and pyrolysis cycles. Residual stresses induced during processing were evaluated. Mechanical and thermo-physical properties of the composites with polymer-derived matrix, i.e. 3-pt bending strength and thermal expansion coefficients (CTE), were measured dependent on reinfiltration cycles and fiber orientation. The oxidation resistance was investigated. Specific pyrolyzed samples were infiltrated via silicon melts in order to enhance corrosion and wear resistance.     

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.     

Modelling of chip separation in machining unidirectional FRP composites by stiffness degradation concept

Progressive failure of unidirectional glass fiber-reinforced polymer composites (FRP) was studied using finite element analysis in orthogonal machining. Chip formation process and damage modes such as matrix cracking, fiber–matrix debonding and fiber breaking were modelled by degrading the material properties. Damage analysis was carried out using Hashin, Maximum stress and Hoffman failure criteria. After damage was detected, selective stiffness degradation was applied to the workpiece material. The objective of this study is to better understand the chip formation process and to analyse the cutting-induced damage from initiation stage until complete chip formation. The effect of the fiber orientation on cutting forces and sub-surface damage was investigated with different failure criteria. The results were addressed in terms of cutting forces evolution and damage progression in the composite structure during machining. It was demonstrated that the use of the stiffness degradation concept with the appropriate failure criterion responds potentially in a predictable fashion to changes in chip formation process for machining of FRPs.     

Erosion–corrosion behavior of plastic mold steel in solid/aqueous slurry

Erosion–corrosion behavior of a precipitation hardenable plastic mold steel (NAK80) has been investigated by using a rotated slurry erosion rig containing a slurry comprising 20 wt% Al₂O₃ particle and 3.5% NaCl solution. The erosion–corrosion rate and the synergism between erosion and corrosion have been determined under various conditions. The major environmental parameters considered are impact angle, impact velocity, and particle size. Post-test examination was conducted to identify the material degradation mechanism involved. The erosion–corrosion mechanisms of NAK80 mold steel at high-impact angles are dominated by the formation of impact pits, dissolution of metallic matrix, and plastic deformation fatigue spalling, whereas at low-impact angles, the mechanisms are dominated by the formation of impact pits, dissolution of metallic matrix, fatigue cracks, and cutting. The observed synergism between these mechanisms is much more accentuated at an oblique impact angle than that at a normal impact angle. At a given impact angle, the erosion–corrosion rate is found to increase with the impact velocity and the size of solid particles. The maximum peak of the erosion rates lies at oblique angles between 30° and 45°, whereas the maximum peak of the erosion–corrosion rates appears at 45°, and the erosion–corrosion rate is higher than the erosion rate alone at all angles examined. There is a positive synergism between erosion and corrosion for NAK80 mold steel in solid/aqueous slurry. The synergistic effect is 40–60% of the total weight loss. The contribution of synergism to the total weight loss depends upon the impact velocity; however, it is almost independent of the impact angle and particle size.     

Effect of water absorption on erosive wear behaviour of polyamides

Two polyamides (PAs) viz. PA 6 and PA 12 were selected for investigating the influence of water absorption on some physical, mechanical and tribological properties. Erosive wear studies on water treated and untreated samples were carried out at two impact angles viz. 30° and 90°. Tests on tensile strength of untreated and treated polyamides revealed that the water treatment resulted in enhancement for PA12 and reduction for PA 6. Exactly similar trends were reflected in their erosive wear performance also. The water absorption deteriorated the wear performance of PA 6 at both the angles, whereas the erosion wear behaviour of PA 12 improved at both the angles due to water absorption. The improvement was more significant at the angle of 30° rather than 90°. Scanning electron microscopic (SEM) investigations were done to study the topography of worn surfaces and to understand the wear mechanisms.     

Thermomechanical behavior of PA6.6 composites subjected to low cycle fatigue

In this study, manifold experiments were conducted to investigate the thermomechanical behavior of short E-glass fiber-reinforced polyamide 6.6 composites subjected to low cycle fatigue loadings. Different hygrometric states, fiber configurations and loading rates were considered. Mechanical, thermal and energy responses of composite specimens were recorded using photomechanic techniques. The influence of water content, fiber orientation and loading rate on these thermomechanical responses was systematically analysed.The mechanical findings indicated that the ratcheting phenomenon was more pronounced for humid composites reinforced with fibers oriented transversely and subjected to a low loading rate. Moreover, the order of magnitude in self-heating was greater for transversal fiber composites conditioned at high relative humidity and subjected to a 10 Hz loading rate. From a thermodynamic standpoint, we also noticed that high proportions of the mean stored energy rate were obtained at a high loading rate, with values exceeded 64%. These values were noticeably altered by the water content and fiber angles, i.e. lower as the relative humidity increased and higher as the fiber angles increased.