Search results for: Magnesium matrix composite

Authors: M. E. Turan, H. Zengin, E. Cevik, Y. Sun, Y. Turen, H. Ahlatci

Abstract:

In this study, the effects of B₄C and SiC particle reinforcements on wear properties of magnesium matrix metal composites produced by pressure infiltration method were investigated. AZ91 (9%Al-1%Zn) magnesium alloy was used as a matrix. AZ91 magnesium alloy was melted under an argon atmosphere. The melt was infiltrated to the particles with an appropriate pressure. Wear tests, hardness tests were performed respectively. Microstructure characterizations were examined by light optical (LOM) and scanning electron microscope (SEM). The results showed that uniform particle distributions were achieved in both B₄C and SiC reinforced composites. Wear behaviors of magnesium matrix metal composites changed as a function of type of particles. SiC reinforced composite has better wear performance and higher hardness than B₄C reinforced composite.

Keywords: Magnesium matrix composite, pressure infiltration, SEM, wear.

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Authors: E. Karakulak, R. Yamanoğlu, M. Zeren

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In the current study, fly ash obtained from a thermal power plant was used as reinforcement in pure magnesium. The composite materials with different fly ash contents were produced with powder metallurgical methods. Powder mixtures were sintered at 540^oC under 30 MPa pressure for 15 minutes in a vacuum assisted hot press. Results showed that increasing ash content continuously increases hardness of the composite. On the other hand, minimum wear damage was obtained at 2 wt. % ash content. Addition of higher level of fly ash results with formation of cracks in the matrix and increases wear damage of the material.

Keywords: Mg composite, fly ash, wear, powder metallurgy.

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Authors: C. Photiphitak, P. Rakkwamsuk, P. Muthitamongkol, C. Thanachayanont

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TiO2/MgO composite films were prepared by coating the magnesium acetate solution in the pores of mesoporous TiO2 films using a dip coating method. Concentrations of magnesium acetate solution were varied in a range of 1x10-4 – 1x10-1 M. The TiO2/MgO composite films were characterized by scanning electron microscopy (SEM), transmission electron microscropy (TEM), electrochemical impedance spectroscopy(EIS) , transient voltage decay and I-V test. The TiO2 films and TiO2/MgO composite films were immersed in a 0.3 mM N719 dye solution. The Dye-sensitized solar cells with the TiO2/MgO/N719 structure showed an optimal concentration of magnesium acetate solution of 1x10-3 M resulting in the MgO film estimated thickness of 0.0963 nm and giving the maximum efficiency of 4.85%. The improved efficiency of dyesensitized solar cell was due to the magnesium oxide film as the wide band gap coating decays the electron back transfer to the triiodide electrolyte and reduce charge recombination.

Keywords: Magnesium oxide thin film, TiO2/MgO composite films, Electrochemical Impedance Spectrum, Transient voltage decay

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Authors: H. M. Nanjundaswamy, S. K. Nath, S. Ray

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TiO₂ particles have been added in molten aluminium to result in aluminium based cast Al/Al₃Ti-Al₂O₃ composite, which has been added then to molten magnesium to synthesize magnesium based cast Mg-Al/Al₃Ti-Al₂O₃ composite. The nominal compositions in terms of Mg, Al, and TiO₂ contents in the magnesium based composites are Mg-9Al-0.6TiO₂, Mg-9Al-0.8TiO₂, Mg-9Al-1.0TiO₂ and Mg-9Al-1.2TiO₂ designated respectively as MA6T, MA8T, MA10T and MA12T. The microstructure of the cast magnesium based composite shows grayish rods of intermetallics Al₃Ti, inherited from aluminium based composite but these rods, on hot forging, breaks into smaller lengths decreasing the average aspect ratio (length to diameter) from 7.5 to 3.0. There are also cavities in between the broken segments of rods. β-phase in cast microstructure, Mg₁₇Al₁₂, dissolves during heating prior to forging and re-precipitates as relatively finer particles on cooling. The amount of β-phase also decreases on forging as segregation is removed. In both the cast and forged composite, the Brinell hardness increases rapidly with increasing addition of TiO₂ but the hardness is higher in forged composites by about 80 BHN. With addition of higher level of TiO₂ in magnesium based cast composite, yield strength decreases progressively but there is marginal increase in yield strength over that of the cast Mg-9 wt. pct. Al, designated as MA alloy. But the ultimate tensile strength (UTS) in the cast composites decreases with the increasing particle content indicating possibly an early initiation of crack in the brittle inter-dendritic region and their easy propagation through the interfaces of the particles. In forged composites, there is a significant improvement in both yield strength and UTS with increasing TiO₂ addition and also, over those observed in their cast counterpart, but at higher addition it decreases. It may also be noted that as in forged MA alloy, incomplete recovery of forging strain increases the strength of the matrix in the composites and the ductility decreases both in the forged alloy and the composites. Initiation fracture toughness, J_IC, decreases drastically in cast composites compared to that in MA alloy due to the presence of intermetallic Al₃Ti and Al₂O₃ particles in the composite. There is drastic reduction of J_IC on forging both in the alloy and the composites, possibly due to incomplete recovery of forging strain in both as well as breaking of Al₃Ti rods and the voids between the broken segments of Al₃Ti rods in composites. The ratio of tearing modulus to elastic modulus in cast composites show higher ratio, which increases with the increasing TiO₂ addition. The ratio decreases comparatively more on forging of cast MA alloy than those in forged composites.

Keywords: Composite, fracture toughness, forging, tensile properties.

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Authors: Rafayel K. Kostanyan

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The opportunities of use of metallic magnesium as a generator of hydrogen gas, as well as thermal and electric energy is presented in the paper. Various schemes of magnesium application are discussed and power characteristics of corresponding devices are presented. Economic estimation of hydrogen price obtained by different methods is made, including the use of magnesium as a source of hydrogen for transportation in comparison with gasoline. Details and prospects of our new inexpensive technology of magnesium production from magnesium hydroxide and magnesium bearing rocks (which are available worldwide and in Armenia) are analyzed. It is estimated the threshold cost of Mg production at which application of this metal in power engineering is economically justified.

Keywords: Magnesium, power generation, production, renewable energy.

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Authors: A. S. Kipcak, F. T. Senberber, E. Moroydor Derun, S. Piskin

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Magnesium wastes and scraps, one of the metal wastes, are produced by many industrial activities, all over the world. Their growing size is becoming a future problem for the world. In this study, the use of magnesium wastes as a raw material in the production of the magnesium borate hydrates are aimed. The method used in the experiments is hydrothermal synthesis. The conditions are set to, waste magnesium to B2O3, 1:3 as a molar ratio. Four different reaction times are studied which are 30, 60, 120 and 240 minutes. For the identification analyses X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FT-IR) and Raman spectroscopy techniques are used. As a result at all the reaction times magnesium borate hydrates are synthesized and the most crystalline forms are obtained at a reaction time of 120 minutes. The overall yields of the production are found between the values of 65-80 %.

Keywords: Hydrothermal synthesis, magnesium borates, magnesium wastes, boron oxide

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Authors: E. Moroydor Derun, A. S. Kipcak, A. Kaplan, S. Piskin

Abstract:

Waste problem is becoming a future problem all over the world. Magnesium wastes which can be used in recycling processes are produced by many industrial activities. Magnesium borates which have useful properties such as; high heat resistance, corrosion resistance, supermechanical strength, superinsulation, light weight, high coefficient of elasticity and so on. Addition, magnesium borates have great potential in the development of ceramic and detergents industry, whisker-reinforced composites, antiwear, and reducing friction additives.

In this study, using the starting materials of waste magnesium and H₃BO₃ the hydrothermal method was applied at a moderate temperature of 70^oC with different reaction times. Several reaction times of waste magnesium to H₃BO₃ were selected as; 30, 60, 120, 240 minutes. After the synthesis, X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques were applied to products. As a result, the forms of Admontite [MgO(B₂O₃)₃.7(H₂O)] and Mcallisterite [Mg₂(B₆O₇(OH)₆)₂.9(H₂O)] were synthesized.

Keywords: Hydrothermal synthesis, magnesium borates, waste magnesium.

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Authors: Yu T. Tsai, Jin H. Huang

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In this paper, the specific sound Transmission Loss (TL) of the Laminated Composite Plate (LCP) with different material properties in each layer is investigated. The numerical method to obtain the TL of the LCP is proposed by using elastic plate theory. The transfer matrix approach is novelty presented for computational efficiency in solving the numerous layers of dynamic stiffness matrix (D-matrix) of the LCP. Besides the numerical simulations for calculating the TL of the LCP, the material properties inverse method is presented for the design of a laminated composite plate analogous to a metallic plate with a specified TL. As a result, it demonstrates that the proposed computational algorithm exhibits high efficiency with a small number of iterations for achieving the goal. This method can be effectively employed to design and develop tailor-made materials for various applications.

Keywords: Sound transmission loss, laminated composite plate, transfer matrix approach, inverse problem, elastic plate theory, material properties.

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Authors: Oluwagbenga B. Fatile, Felix U. Idu, Olajide T. Sanya

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This paper reports the viability of developing Zn-27Al alloy matrix hybrid composites reinforced with alumina, graphite and fly ash (solid waste bye product of coal in thermal power plants). This research work was aimed at developing low cost-high performance Zn-27Al matrix composite with low density. Alumina particulates (Al2O3), graphite added with 0, 2, 3, 4 and 5 wt% fly ash were utilized to prepare 10wt% reinforcing phase with Zn-27Al alloy as matrix using two-step stir casting method. Density measurement, estimated percentage porosity, tensile testing, micro hardness measurement and optical microscopy were used to assess the performance of the composites produced. The results show that the hardness, ultimate tensile strength, and percent elongation of the hybrid composites decrease with increase in fly ash content. The maximum decrease in hardness and ultimate tensile strength of 13.72% and 15.25% respectively were observed for composite grade containing 5wt% fly ash. The percentage elongation of composite sample without fly ash is 8.9% which is comparable with that of the sample containing 2wt% fly ash with percentage elongation of 8.8%. The fracture toughness of the fly ash containing composites was however superior to those of composites without fly ash with 5wt% fly ash containing composite exhibiting the highest fracture toughness. The results show that fly ash can be utilized as complementary reinforcement in ZA-27 alloy matrix composite to reduce cost.

Keywords: Fly ash, hybrid composite, mechanical behaviour, stir-cast.

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Authors: N. Tugrul, F. T. Senberber, A. S. Kipcak E. Moroydor Derun, S. Piskin

Abstract:

In this research, it is aimed not only microwave synthesis of magnesium borates but also evaluation of magnesium wastes. Synthesis process can be described with the reaction of Mg wastes and boric acid using microwave energy. X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) were applied to synthesized minerals. According to XRD results, magnesium borate hydrate mixtures were obtained as mcallisterite (pdf# = 01-070-1902, Mg₂(B₆O₇(OH)₆)₂.9(H₂O)) at higher crystallinity properties was achieved at the mole ratio raw material 1:1. Also, other kinds of magnesium borate hydrates were obtained at lower crystallinity such as admontite (pdf # = 01-076-0540, MgO(B₂O₃)₃.7(H₂O)), inderite (pdf # = 01-072-2308, 2MgO.3B₂O₃.15(H₂O)) and magnesium borate hydrates (pdf # = 01-076-0539, MgO(B₂O₃)₃.6(H₂O)). FT-IR spectrums indicated that minor changes were seen at the band values of characteristic stretching in each experiment. At the end of experiments it is seen that using microwave energy may contribute positive effects to design of synthesis process such as reducing reaction time and products at higher crystallinity.

Keywords: Magnesium wastes, boric acid, magnesium borate, microwave energy.

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Authors: D. Sujan, Z. Oo, M. E. Rahman, M. A. Maleque, C. K. Tan

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Particulate reinforced metal matrix composites (MMCs) are potential materials for various applications due to their advantageous of physical and mechanical properties. This paper presents a study on the performance of stir cast Al2O3 SiC reinforced metal matrix composite materials. The results indicate that the composite materials exhibit improved physical and mechanical properties, such as, low coefficient of thermal expansion, high ultimate tensile strength, high impact strength, and hardness. It has been found that with the increase of weight percentage of reinforcement particles in the aluminium metal matrix, the new material exhibits lower wear rate against abrasive wearing. Being extremely lighter than the conventional gray cast iron material, the Al-Al2O3 and Al-SiC composites could be potential green materials for applications in the automobile industry, for instance, in making car disc brake rotors.

Keywords: Metal Matrix Composite, Strength to Weight Ratio, Wear Rate

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Authors: C. H. S. Vidyasagar, D. B. Karunakar

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In this present work, five different composite samples with AA2024 as matrix and varying amounts of yttrium (0.1-0.5 wt.%) as reinforcement are developed through cold compaction. The microstructures of the developed composite samples revealed that the yttrium reinforcement caused grain refinement up to 0.3 wt.% and beyond which the refinement is not effective. The microstructure revealed Al2Cu precipitation which strengthened the composite up to 0.3 wt.% yttrium reinforcement. Upon further increase in yttrium reinforcement, the intermetallics and the precipitation coarsen and their corresponding strengthening effect decreases. The mechanical characterization revealed that the composite sample reinforced with 0.3 wt.% yttrium showed highest mechanical properties like 82 HV of hardness, 276 MPa Ultimate Tensile Strength (UTS), 229 MPa Yield Strength (YS) and an elongation (EL) of 18.9% respectively. However, the relative density of the developed composites decreased with the increase in yttrium reinforcement.

Keywords: Mechanical properties, AA 2024 matrix, yttrium reinforcement, cold compaction, precipitation.

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Authors: M.Puviyarasan, C.Praveen

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In this study, Friction Stir Processing (FSP) a recent grain refinement technique was employed to disperse micron-sized (2 *m) SiCp particles into aluminum alloy AA6063. The feasibility to fabricate bulk composites through FSP was analyzed and experiments were conducted at different traverse speeds and wider volumes of the specimens. Micro structural observation were carried out by employing optical microscopy test of the cross sections in both parallel and perpendicular to the tool traverse direction. Mechanical property including micro hardness was evaluated in detail at various regions on the specimen. The composites had an excellent bonding with aluminum alloy substrate and a significant increase of 30% in the micro hardness value of metal matrix composite (MMC) as to that of the base metal has observed. The observations clearly indicate that SiC particles were uniformly distributed within the aluminum matrix.

Keywords: Friction Stir Processing, Metal matrix composite, Bulk composite.

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Authors: E. Moroydor Derun, A. S. Kipcak, A. Kaplan, S. Piskin

Abstract:

Magnesium wastes are produced by many industrial activities. This waste problem is becoming a future problem for the world. Magnesium borates have many advantages such as; high corrosion resistance, heat resistance, high coefficient of elasticity and can also be used in the production of material against radiation. Addition, magnesium borates have great potential in sectors including ceramic and detergents industry and superconducting materials. In this study, using the starting materials of waste magnesium and H3BO3 the hydrothermal method was applied at a moderate temperature of 70oC. Several mole ratios of waste magnesium to H3BO3 are selected as; 1:2, 1:4, 1:6, 1:8, 1:10. Reaction time was determined as 1 hour. After the synthesis, X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques are applied to products. As a result the forms of mcallisterite “Mg2(B6O7(OH)6)2.9(H2O)”, admontite “MgO(B2O3)3.7(H2O)” and magnesium boron hydrate (MgO(B2O3)3.6(H2O)” are obtained. 

Keywords: Hydrothermal synthesis, magnesium borates, waste magnesium.

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Authors: E. Moroydor Derun, P. Gurses, M. Yildirim, A. S. Kipcak, T. Ibroska, S. Piskin

Abstract:

Due to their strong mechanical and thermal properties magnesium borates have a wide usage area such as ceramic industry, detergent production, friction reducing additive and grease production. In this study, microwave synthesis of magnesium borates from MgCl₂.6H₂O (Magnesium chloride hexahydrate), MgO (Magnesium oxide) and H₃BO₃ (Boric acid) for different reaction times is researched. X-ray Diffraction (XRD) and Fourier Transform Infrared (FT-IR) Spectroscopy are used to find out how the reaction time sways on the products. The superficial properties are investigated with Scanning Electron Microscopy (SEM). According to XRD analysis, the synthesized compounds are 00-041-1407 pdf coded Shabinite (Mg₅(BO₃)₄Cl₂(OH)₅.4(H₂O)) and 01-073-2158 pdf coded Karlite (Mg₇(BO₃)₃(OH,Cl)₅).

Keywords: Magnesium borate, microwave synthesis, XRD, SEM.

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Authors: Mohd Yussni Hashim, Mohd Nazrul Roslan, Azriszul Mohd Amin, Ahmad Mujahid Ahmad Zaidi, Saparudin Ariffin

Abstract:

Environmental awareness and depletion of the petroleum resources are among vital factors that motivate a number of researchers to explore the potential of reusing natural fiber as an alternative composite material in industries such as packaging, automotive and building constructions. Natural fibers are available in abundance, low cost, lightweight polymer composite and most importance its biodegradability features, which often called “ecofriendly" materials. However, their applications are still limited due to several factors like moisture absorption, poor wettability and large scattering in mechanical properties. Among the main challenges on natural fibers reinforced matrices composite is their inclination to entangle and form fibers agglomerates during processing due to fiber-fiber interaction. This tends to prevent better dispersion of the fibers into the matrix, resulting in poor interfacial adhesion between the hydrophobic matrix and the hydrophilic reinforced natural fiber. Therefore, to overcome this challenge, fiber treatment process is one common alternative that can be use to modify the fiber surface topology by chemically, physically or mechanically technique. Nevertheless, this paper attempt to focus on the effect of mercerization treatment on mechanical properties enhancement of natural fiber reinforced composite or so-called bio composite. It specifically discussed on mercerization parameters, and natural fiber reinforced composite mechanical properties enhancement.

Keywords: Mercerization treatment, mechanical properties, natural fiber and bio composite

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Authors: Anna Girchenko, Victor A. Eremeyev, Holm Altenbach

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In the present work we investigate both the elastic and electric properties of a chiral material. We consider a composite structure made from a polymer matrix and anisotropic inclusions of GaAs taking into account piezoelectric and dielectric properties of the composite material. The principal task of the work is the estimation of the functional properties of the composite material.

Keywords: Coupled electromechanical behavior, Composite structure, Chiral metamaterial.

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Authors: Nripjit, Anand K Tyagi, Nirmal Singh

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The present work consecutively on synthesis and characterization of composites, Al/Al alloy A 384.1 as matrix in which the main ingredient as Al/Al-5% MgO alloy based metal matrix composite. As practical implications the low cost processing route for the fabrication of Al alloy A 384.1 and operational difficulties of presently available manufacturing processes based in liquid manipulation methods. As all new developments, complete understanding of the influence of processing variables upon the final quality of the product. And the composite is applied comprehensively to the acquaintance for achieving superiority of information concerning the specific heat measurement of a material through the aid of thermographs. Products are evaluated concerning relative particle size and mechanical behavior under tensile strength. Furthermore, Taguchi technique was employed to examine the experimental optimum results are achieved, owing to effectiveness of this approach.

Keywords: MMC, Thermographs, Tensile strength, Taguchi technique, Optimal parameters

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Authors: N. Tugrul, E. Sariburun, F. T. Senberber, A. S. Kipcak, E. Moroydor Derun, S. Piskin

Abstract:

Boron-gypsum is a waste which occurs in the boric acid production process. In this study, the boron content of this waste is evaluated for the use in synthesis of magnesium borates and such evaluation of this kind of waste is useful more than storage or disposal. Magnesium borates, which are a sub-class of boron minerals, are useful additive materials for the industries due to their remarkable thermal and mechanical properties. Magnesium borates were obtained hydrothermally at different temperatures. Novelty of this study is the search of the solution density effects to magnesium borate synthesis process for the increasing the possibility of borongypsum usage as a raw material. After the synthesis process, products are subjected to XRD and FT-IR to identify and characterize their crystal structure, respectively.

Keywords: Boron-gypsum, hydrothermal synthesis, magnesium borate, solution density.

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Authors: Kowit Suwannahong, Wipada Sanongra, Jittiporn Kruenate, Sarun Phibanchon, Siriuma Jawjit, Wipawee Khamwichit

Abstract:

The photocatalytic activity efficiency of TiO2 for the degradation of Toluene in photoreactor can be enhanced by nano- TiO2/LDPE composite film. Since the amount of TiO2 affected the efficiency of the photocatalytic activity, this work was mainly concentrated on the effort to embed the high amount of TiO2 in the Polyethylene matrix. The developed photocatalyst was characterized by XRD, UV-Vis spectrophotometer and SEM. The SEM images revealed the high homogeneity of the deposition of TiO2 on the polyethylene matrix. The XRD patterns interpreted that TiO2 embedded in the PE matrix exhibited mainly in anatase form. In addition, the photocatalytic results show that the toluene removal efficiencies of 30±5%, 49±4%, 68±5%, 42±6% and 33±5% were obtained when using the catalyst loading at 0%, 10%, 15%, 25% and 50% (wt. cat./wt. film), respectively.

Keywords: Photocatalytic oxidation, Toluene, nano-TiO2/LDPE composite film.

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Authors: M. Palizvan, M. T. Abadi, M. H. Sadr

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Due to variations in damage mechanisms in the microscale, the behavior of fiber-reinforced composites is nonlinear and difficult to model. To make use of computational advantages, homogenization method is applied to the micro-scale model in order to minimize the cost at the expense of detail of local microscale phenomena. In this paper, the effective stiffness is calculated using the homogenization of nonlinear behavior of a composite representative volume element (RVE) containing fiber-matrix debonding. The damage modes for the RVE are considered by using cohesive elements and contacts for the cohesive behavior of the interface between fiber and matrix. To predict more realistic responses of composite materials, different random distributions of fibers are proposed besides square and hexagonal arrays. It was shown that in some cases, there is quite different damage behavior in different fiber distributions. A comprehensive comparison has been made between different graphs.

Keywords: Homogenization, cohesive zone model, fiber-matrix debonding, RVE.

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Authors: Ahmad R. Zamani, Luigi Sanguigno, Angelo R. Maligno

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A 3D woven composite, designed for automotive applications, is studied using Abaqus Finite Element (FE) software suite. Python scripts were developed to build FE models of the woven composite in Complete Abaqus Environment (CAE). They can read TexGen or WiseTex files and automatically generate consistent meshes of the fabric and the matrix. A user menu is provided to help define parameters for the FE models, such as type and size of the elements in fabric and matrix as well as the type of matrix-fabric interaction. Node-to-node constraints were imposed to guarantee periodicity of the deformed shapes at the boundaries of the representative volume element of the composite. Tensile loads in three axes and biaxial loads in x-y directions have been applied at different Fibre Volume Fractions (FVFs). A simple damage model was implemented via an Abaqus user material (UMAT) subroutine. Existing tools for homogenization were also used, including voxel mesh generation from TexGen as well as Abaqus Micromechanics plugin. Linear relations between homogenised elastic properties and the FVFs are given. The FE models of composite exhibited balanced behaviour with respect to warp and weft directions in terms of both stiffness and strength.

Keywords: 3D woven composite, meso-scale finite element modelling, homogenisation of elastic material properties, Abaqus Python scripting.

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Authors: A. S. Kipcak, P. Gurses, K. Kunt, E. Moroydor Derun, S. Piskin

Abstract:

There are many kinds of metal borates found not only in nature but also synthesized in the laboratory such as magnesium borates. Due to its excellent properties, as remarkable ceramic materials, they have also application areas in anti-wear and friction reducing additives as well as electro-conductive treating agents. The synthesis of magnesium borate powders can be fulfilled simply with two different methods, hydrothermal and thermal synthesis. Microwave assisted method, also another way of producing magnesium borate, can be classified into thermal synthesis because of using the principles of solid state synthesis. It also contributes producing particles with small size and high purity in nano-size material synthesize. In this study the production of magnesium borates, are aimed using MgCl2.6H2O and H3BO3. The identification of both starting materials and products were made by the equipments of, X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR). After several synthesis steps magnesium borates were synthesized and characterized by XRD and FT-IR, as well.

Keywords: FT-IR, magnesium borates, microwave method, XRD.

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Authors: Li Yongfeng, Liu Yixing, Li Jian, Li Jun

Abstract:

A novel biomass composite inspired from wood porous structure was manufactured by impregnating vinyl monomer into wood cellular structure under vacuum conditions, and initiating the monomer for in situ polymerization through a thermal treatment. The vacuum condition was studied, and the mechanical properties of the composite were also tested. SEM observation shows that polymer generated in the wood porous structure, and strongly interacted with wood matrix; and the polymer content increased with vacuum value increasing. FTIR indicates that polymer grafted onto wood matrix, resulting chemical complex between them. The rate of monomer loading increased with increasing vacuum value and time, accordance with rate of polymer loading. The compression strength and modulus of elasticity linearly increased with the increasing rate of polymer loading. Results indicate that the novel biomass composite possesses good mechanical properties capable of applying in the fields of construction, traffic and so forth.

Keywords: Biomass composite, manufacture, vinyl monomer, wood cellular structure.

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Authors: Li Hong Chen, Wei Zhou, Chu Sing Lim, Eng Kiong Teo, Ngai Moh Law

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Magnesium alloy has been widely investigated as biodegradable cardiovascular stent and bone implant. Its application for biodegradable esophageal stenting remains unexplored. This paper reports the biodegradation behaviors of AZ31 magnesium alloy in artificial saliva and various types of beverage in vitro. Results show that the magnesium ion release rate of AZ31 in artificial saliva for a stent (2cm diameter, 10cm length at 50% stent surface coverage) is 43 times lower than the daily allowance of human body magnesium intakes. The degradation rates of AZ31 in different beverages could also be significantly different. These results suggest that the esophagus in nature is a less aggressive chemical environment for degradation of magnesium alloys. The significant difference in degradation rates of AZ31 in different beverages opens new opportunities for development of degradation controllable esophageal stent through customizing ingested beverages.

Keywords: Biodegradable esophageal stent, beverages, magnesium alloy, saliva.

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Authors: Mohammad Tahaye Abadi

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The present paper concerns with the influence of fiber packing on the transverse plastic properties of metal matrix composites. A micromechanical modeling procedure is used to predict the effective mechanical properties of composite materials at large tensile and compressive deformations. Microstructure is represented by a repeating unit cell (RUC). Two fiber arrays are considered including ideal square fiber packing and random fiber packing defined by random sequential algorithm. The micromechanical modeling procedure is implemented for graphite/aluminum metal matrix composite in which the reinforcement behaves as elastic, isotropic solids and the matrix is modeled as an isotropic elastic-plastic solid following the von Mises criterion with isotropic hardening and the Ramberg-Osgood relationship between equivalent true stress and logarithmic strain. The deformation is increased to a considerable value to evaluate both elastic and plastic behaviors of metal matrix composites. The yields strength and true elastic-plastic stress are determined for graphite/aluminum composites.

Keywords: Fiber packing, metal matrix composites, micromechanics, plastic deformation, random

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Authors: B. A. Berns, V. Romanovicz, M. M. de Camargo Forte, D. E. O. S. Carpenter

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The Proton Exchange Membranes (PEM) are largely studied because they operate at low temperatures and they are suitable for mobile applications. However, there are some deficiencies in their operation, mainly those that use ethanol as a hydrogen source, that require a certain attention. Therefore, this research aimed to develop Nafion® composite membranes, mixing clay minerals, kaolin and halloysite to the polymer matrix in order to improve the ethanol molecule retentions and, at the same time, to keep the system’s protonic conductivity. The modified Nafion/Kaolin, Nafion/Halloysite composite membranes were prepared in weight proportion of 0.5, 1.0 and 1.5. The membranes obtained were characterized as to their ethanol permeability, protonic conductivity and water absorption. The composite morphology and structure are characterized by SEM and EDX and the thermal behavior is determined by TGA and DSC. The analysis of the results shows ethanol permeability reduction from 48% to 63%. However, the protonic conductivity results are lower in relation to pure Nafion®. As to the thermal behavior, the Nafion® composite membranes were stable up to a temperature of 325ºC.

Keywords: Polymer-matrix composites (PMCs), Thermal properties, Nanoclay, Differential scanning calorimetry.

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Authors: Mohammed T. Hayajneh, Adel Mahmood Hassan, Moath AL-Qudah

Abstract:

Burnishing is increasingly used as a finishing operation to improve surface roughness and surface hardness. This can be achieved by applying a hard ball or roller onto metallic surfaces under pressure, in order to achieve many advantages in the metallic surface. In the present work, the feed rate, speed and force have been considered as the basic burnishing parameters to study the surface roughness and surface hardness of metallic matrix composites. The considered metal matrix composites were made from Aluminum-Magnesium-Graphite with five different weight percentage of graphite. Both effects of burnishing parameters mentioned above and the graphite percentage on the surface hardness and surface roughness of the metallic matrix composites were studied. The results of this investigation showed that the surface hardness of the metallic composites increases with the increase of the burnishing force and decreases with the increase in the burnishing feed rate and burnishing speed. The surface roughness of the metallic composites decreases with the increasing of the burnishing force, feed rate, and speed to certain values, then it starts to increase. On the other hand, the increase in the weight percentage of the graphite in the considered composites causes a decrease in the surface hardness and an increase in the surface roughness.

Keywords: Burnishing process, Al-Mg-Graphite composites, Surface hardness, Surface roughness.

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Authors: Ghazi S. Kahmmash

Abstract:

New generalization of the new class matrix polynomial set have been obtained. An explicit representation and an expansion of the matrix exponential in a series of these matrix are given for these matrix polynomials.

Keywords: Generating functions, Recurrences relation and Generalization of the new class matrix polynomial set.

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Authors: C. N. Okafor, M. Maaza, T. A. E. Mokrani

Abstract:

A proton exchange membrane has been developed for direct methanol fuel cell (DMFC). The nanofiber network composite membranes were prepared by interconnected network of Nafion (perfuorosulfonic acid) nanofibers that have been embedded in an uncharged and inert polymer matrix, by electro-spinning. The spinning solution of Nafion with a low concentration (1 wt% compared to Nafion) of high molecular weight poly(ethylene oxide), as a carrier polymer. The interconnected network of Nafion nanofibers with average fiber diameter in the range of 160-700nm, were used to make the membranes, with the nanofiber occupying up to 85% of the membrane volume. The matrix polymer was crosslinked with Norland Optical Adhesive 63 under UV. The resulting membranes showed proton conductivity of 0.10 S/cm at 25°C and 80% RH; and methanol permeability of 3.6 x 10-6 cm2/s.

Keywords: Composite membrane, electrospinning, fuel cell, nanofibers.

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