Showing papers in "Advanced Materials Research in 2008"

Diamond-Based Metal Matrix Composites for Thermal Management Made by Liquid Metal Infiltration — Potential and Limits

Abstract: Diamond-based metal matrix composites have been made based on pure Al and eutectic Ag-3Si alloy by gas pressure infiltration into diamond powder beds with the aim to maximize thermal conductivity and to explore the range of coefficient of thermal expansion (CTE) that can be covered. The resulting composites covered roughly the range between 60 and 75 vol-% of diamond content. For the Al-based composites a maximum thermal conductivity at room temperature of 7.6 W/cmK is found while for the Ag-3Si based composites an unprecedented value of 9.7 W/cmK was achieved. The CTE at room temperature varied as a function of the diamond volume fraction between 3.3 and 7.0 ppm/K and 3.1 and 5.7 ppm/K for the Al-based and the Ag-3Si-based composites, respectively. The CTE was further found to vary quite significantly with temperature for the Al-based composites while the variation with temperature was less pronounced for the Ag-3Si-based composites. The results are compared with prediction by analytical modeling using the differential effective medium scheme for thermal conductivity and the Schapery bounds for the CTE. For the thermal conductivity good agreement is found while for the CTE a transition of the experimental data from Schapery’s upper to Schapery’s lower bound is observed as volume fraction increases. While the thermophysical properties are quite satisfactory, there is a trade-off to be made in these materials between high thermal conductivity and low CTE on the one side and surface quality and machinability on the other.

Synthetic Biomimetic Carbonate-Hydroxyapatite Nanocrystals for Enamel Remineralization

Abstract: New biomimetic carbonate-hydroxyapatite nanocrystals (CHA) have been designed and synthesized in order to obtain a remineralization of the altered enamel surfaces. Synthesized CHA mimic for composition, structure, nano dimension and morphology bone apatite crystals and their chemical-physical properties resemble closely those exhibited by enamel natural apatite. CHA can chemically bound themselves on the surface of natural enamel apatite thanks to their tailored biomimetic characteristics. The remineralization effect induced by CHA represents a real new deposition of carbonate-hydroxyapatite into the eroded enamel surface scratches forming a persistent biomimetic mineral coating, which covers and safeguards the enamel structure. The experimental results point out the possibility to use materials alternative to fluoride compounds which is commonly utilized to contrast the mechanical abrasions and acid attacks. The apatitic synthetic coating is less crystalline than enamel natural apatite, but consists of a new biomimetic apatitic mineral deposition which progressively fills the surface scratches. Therefore the application of biomimetic CHA may be considered an innovative approach to contrast the acid and bacteria attacks.

Joining of Superalloys to Intermetallics Using Nanolayers

Abstract: Joining nickel based superalloys to gamma-TiAl intermetallic alloys will contribute to a more efficient application of these advanced materials, particularly in extreme environments. In this study, Inconel alloy and gamma-TiAl are joined using as filler alternated nanolayer thin films deposited onto each base material. The nanolayers consisted in Ni/Al exothermic reactive multilayer thin films with periods of 5 and 14 nm deposited by d.c. magnetron sputtering in order to improve the adhesion to the substrates and to avoid the reaction between Ni and Al. Diffusion bonding experiments with multilayer coated alloys were performed under vacuum at 800°C by applying 50 MPa during 1h. Bonding was achieved in large areas of the centre of the joints where regions without cracks or pores were produced, especially when using multilayer thin films with a 14 nm modulation period.

Temperature Effect on Chicken Egg Shell Investigated by XRD, TGA and FTIR

Abstract: The main purpose of this work is to study the structure of Anadara granosa shell sample and its structural transformation upon heat treatments. The sample was ground and characterized as powder throughout this work. Structural identifications of all samples were characterized, and determined qualitatively by using X-ray diffraction, IR spectroscopy and thermogravimetry measurement (TGA). It was found that the specimen is made of aragonite, a common phase of CaCO3 mineral. The powder sample was annealed at specific temperatures over the range of 200°C - 900°C and the effects of heat treatment on the structure of Anadara granosa shell samples were studied. The results show that aragonite transforms to calcite at the temperatures between 200°C and 400°C and completely becomes calcite between 400-500°C. Then, the calcite transforms to calcium oxide at the temperatures between 500°C - 900°C. The exact structures and quantities of phase at different annealing temperatures were studied by Rietveld refinement. In our study, we also used IR spectroscopy and TGA to study the effect of water absorption of the samples on the phase transformation.

Flexural Failure of Unidirectional Hybrid Fibre-Reinforced Polymer (FRP) Composites Containing Different Grades of Glass Fibre

Abstract: The flexural behaviour of 6-ply unidirectional hybrid fibre-reinforced polymer (FRP) matrix composites containing a mixture of E-glass and S2-glass fibres was investigated. A high performance epoxy system comprising of Kinetix® R240 epoxy resin (combined with Kinetix® H160 epoxy hardener) was utilised for the composite matrix. Flexural testing was conducted in accordance with Procedure A of the ASTM D790-03 test standard on a universal testing machine equipped with a three-point bend test rig. In addition to varying the stacking configurations of the composite prepregs, the influence of span-to-depth ratio on the flexural properties and failure mechanisms was also studied. The failure mechanisms of the resulting fractured specimens were characterised using optical microscopy and compared with those noted by the authors in previous work.

In Vitro Biocompatibility Study of Nano TiO2 Materials

Abstract: Nano TiO2 material is an extensively used and adequately studied material and has a close contact with human in various fields, such as dope, dye, ceramic, cosmetic and medicine. Therefore, it’s very important to study the biocompatibility and biosafety of nano TiO2 materials. In the present study, various nano TiO2 materials with different dimension and crystal structures were confected to suspensions with varied concentrations and evaluated in cell model (mouse fibrocyte) after autoclaving sterilization. After 24h, 48h and 72h of cell culture experiments, MTT assay was used to examine the cell proliferation behavior and the flow cytometry was used to examine the cell apoptosis behavior. The present results of cell experiment showed that nano TiO2 materials had no effect on cell proliferation and apoptosis in a certain range of time and concentration. MTT assay indicated the relative cell proliferation rate in all nano TiO2 material groups were above 92% and the toxicity grade were 0 or 1 class.

Study on Rules in Material Removal Rate and Surface Quality of Short Electric Arc Machining Process

Abstract: Short electric arc machining (SEAM) is a non-conventional machining process that utilizes an arc to melt and vaporize workpiece material. A low voltage, high current supply is employed to produce a continuous arc in either a water-air mixed medium or in air. This paper describes an investigation into the optimization of the SEAM machining efficiency based on experimental design which considers both electrical parameters and machine parameters. The work uses the orthogonal experiment processes to research the influence of the process indicators on machining efficiency.

Nano-Cellulose as Promising Biocarrier

Abstract: Main purpose of this paper is to describe the method for preparation of the reactive nanocellulose biocarrier and to discuss some its biomedical and cosmetic applications. The method for preparation of the biocarrier was proposed that includes steps of controlled depolymerization of initial cellulose; structural and chemical modification in order to graft various biologically active substances to cellulose particles and high-power mechanical disintegration of the modified cellulose particles in liquid media. As a result, the dispersion of the bioactive nano-cellulose was obtained. Due to nano-size, particles of bioactive nano-cellulose capable clean skin's pores, open them and penetrate through the lipid layer and epidermis within the skin strata. This effect of the biocarrier can be employed at the development of advanced types of biomedical and cosmetics remedies used for gentle care and effective treatment of the skin.

Microbial Contamination and Associated Corrosion in Fuels, during Storage, Distribution and Use

Abstract: Microbial contamination and growth in distillate fuels has been described for seventy years. The consequences have ranged from fouling of filters and injectors, to engine malfunction and damage, fuel gauge malfunctions and aggravated corrosion of engines, fuel tanks, equipment and facilities. The types of microbes present vary with the differences in fuel composition and differences in storage and use conditions. Anti-microbial strategies have traditionally included prevention by ‘good housekeeping’ and ‘fire-brigade’ applications of biocides when there are operational problems. Since 2002, first the aviation industry and later fuel suppliers and some militaries, have used simple on-site microbiological tests to monitor fuel and fuel systems and use the results to take remedial actions before operational problems occur. This paper will review our latest knowledge of microbially influenced corrosion and of the new anti-microbial strategies which are being successfully implemented to prevent it.

Ultrastructural Characterization of Liposomes Using Transmission Electron Microscope

Abstract: A liposome is a spherical vesicle composed of phospholipids and cholesterol bilayer membrane and contains a core of aqueous solution. Liposomes are polymeric nanoparticles used for drug delivery due to their unique properties. It can carry both hydrophobic and hydrophilic molecules. In this study, we showed the benefit of using transmission electron microscope (TEM) with negative staining technique to investigate the morphology of liposomes produced by thin film method. At the same magnification of micrograph results, we could see the multilamellar vesicles of liposomes in various figures and different sizes.

Application of Lubrication Theory to Near-Dry Green Grinding – Feasibility Analysis

Abstract: This paper describes an investigation about the grinding fluid optimization supply based on lubrication theory. The models for three-dimensional hydrodynamic flow pressure in contact zone between wheel and work are presented based on Navier-Stokes equation and continuous formulae. It is well known that hydrodynamic fluid pressure generates due to this fluid flux, and that it affects overall grinding resistance and machining accuracy. Moreover, conventional methods of delivering grinding fluid, i.e. flood delivery via a shoe or jet delivery tangential to the wheel via a nozzle, have been proved that they can not fully penetrate this boundary layer and thus, the majority of the cutting fluid is deflected away from the grinding zone. Therefore, in this paper, a new delivery method of grinding fluid, the minimum quantity lubricant (MQL)-near-dry green grinding is presented and analyzed for it not only reduces hydrodynamic lift force but also reduces grinding fluid cost to achieve green manufacturing. Experiments have been carried out to validate the performance of the MQL supply compared with conventional flood cooling. The experimental results have shown that the theoretical model is in agreement with experimental results and the model can well forecast hydrodynamic pressure distribution at contact zone between and workpiece and the MQL supply in grinding is feasible. Experiments have also been carried out to evaluate the performance of the MQL technology compared with conventional flood cooling. Experimental data indicate that the proposed method does not negatively affect to the surface integrity and the process validity has been verified.

LBW of Similar and Dissimilar Skin-Stringer Joints Part I: Process Optimization and Mechanical Characterization

Abstract: Laser beam welding of light alloys has always represented a big challenge for both designers and technologists due to the large number of process parameters to take into account and the variable responses of the different materials to be welded. In this paper the results of experimental research on laser beam welds of innovative heat treatable aluminum alloys is reported. The well known T geometry (a stringer welded to a skin) has been considered. Two different skins have been analyzed: AA 2139 and AA 6156, both in form of rolled sheets. Two different stringer have been analyzed: AA 2139 and PA 765, both in form of extruded parts. AA 4047 has been used as filler wire. In the first part of the paper, all the steps leading to the realization of sound welds will be described. The criteria used in order to assess the soundness of a weld was the absence of defects, such as cracks or large pores, verified by means of NDE. In the second part of study, both micro structural analysis and mechanical characterization of welds will be described and discussed. Conclusions will demonstrate the importance of the influence of chemical composition of the parts, above all stringer. The performance of the best welds, however, were very close to those of parent materials.

Effect of Non-Metallic Inclusion Size and Residual Stresses on Gigacycle Fatigue Properties in High Strength Steel

Abstract: Fatigue fracture of some high-strength steels occurs at small defect in the subsurface zone of a material at low stress amplitude level and in a high-cycle region of more than 106 cycles (gigacycle fatigue life), whereas surface fatigue crack initiation occurs at high-stress amplitude and low cycles. There is a definite stress range where the crack initiation site changes from a surface to a subsurface defect, giving a step-wise S-N curve or a duplex S-N curve. From the experimental results, fatigue fracture mode was classified into three types, such as, surface inclusion induced fracture mode, subsurface inclusion induced fracture mode without granular bright facet (GBF) area and that with the GBF, depending on stress amplitude level and stress ratio. The GBF area was observed in the vicinity of a non-metallic inclusion at the fracture origin inside the fish-eye in gigacycle fatigue regime. It was made clear from the discussion with fracture mechanics that the transition of fracture mode was affected by compressive residual stresses on the specimen surface. Fracture-mode transition diagram was proposed through the experimental and theoretical investigation. Also, from the evaluation of the fatigue life based on the estimated subsurface crack growth rate from the S-N data, effect of inclusion size on the dispersion of fatigue life was explained, and S-N curve for subsurface inclusion-induced fracture depended on the inclusion size was provided.

Nonlinear Stability of Fixed-Fixed FGM Arches Subjected to Mechanical and Thermal Loads

Abstract: Based on Kirchhoff’s assumption of straight normal line of beams and considering the effects of the axial elongation, the initial curvature and the stretching-bending coupling on the arch deformation, geometrically nonlinear governing equations of functionally graded arch subjected to mechanical and thermal loads are derived. In the analysis, it is assumed that the material properties of the arch vary through the thickness as a power function. As a numerical example, the critical buckling load and the corresponding mode shapes of a semicircle arch, with both of the ends fixed, subjected to normally uniform distributed follower force is obtained by the shooting method. The effects of the parameters of material gradient on the critical loads and the deformation of the structure are examined in detail. Equilibrium configurations for different values of the load or temperature rise are plotted. Analysis and numerical results show that the behavior of buckling of the arch is of bifurcation and the buckling modes corresponding to minimum buckling load is asymmetric. In other words, bifurcation buckling occurs prior to the snap-through buckling.

Luminescent ZnO-Al 2 O 3 -SiO 2 Glasses and Glass Ceramics

Abstract: Glasses in the composition range in mol% 35-50 ZnO – 10-15 Al2O3 – 40-55 SiO2 were prepared, undoped and doped with 1 x 1019 and 1 x 1020 Sm3+ per cm3 glass as luminescent species for the visible region, especially for blue and red emission. Phase separation occurs in glass samples with high SiO2 content. SiO2-rich droplets in a Zn2+- Al3+- enriched matrix were formed. Sm3+ ions prefer the Zn2+-Al3+-rich glass matrix. By thermal treatment glass samples were transformed into glass ceramics with the main crystal phases: Zn2SiO4 (willemite), ZnAl2O4 (gahnite) and SiO2-mixed crystals. XRD, SEM and TEM measurements were carried out. The luminescent Sm3+ ions are concentrated in the glass matrix. Photoluminescence excitation and emission spectra were recorded in the UV-VIS-region and the time resolved emission behavior was measured by excitation with a N2-laser at 337 nm. The glasses and glass ceramics have interesting chemical and physical properties, high Tg around 700°C, low coefficient of thermal expansion ~ 4 ppm/K, and high chemical stability.

Study on Ramie Fiber Reinforced Polypropylene Composites (RF-PP) and its Mechanical Properties

Abstract: Natural fiber reinforced polypropylene composites (NF/PP) have attracted a lot of attention because of their light weight, good mechanical properties, recyclable and environmental friendly features. This work has successfully fabricated ramie fiber reinforced polypropylene composites (RF/PP) with a hybrid method of melt-blending and injection molding. Different RF/PP eco-materials have been fabricated by varying the fiber length, fiber content and way of fiber pre-treatment. This paper studied the mechanical properties of the fabricated RF/PP composites in depth by investigating the mechanical behaviors of RF/PP and microstructures of the ruptured surfaces. The results show that the increases of fiber length and fiber content can improve the tensile strength, flexural strength and compression strength apparently, but result in negative influences on the impact strength and elongation behaviors of RF/PP composites. The optimal addition amount of ramie fiber is around 20 wt%. The pre-treatment of ramie fiber in 10%~15% NaOH is good to the mechanical properties of RF/PP. The fiber length can be varied in the range of 3-8 mm. It is expected that the fabricated RF/PP composites can be applied to automobile industry as environmental friendly eco-materials.

Imaging laminar damage in plates using lamb wave beamforming

Abstract: This paper presents the application of Lamb waves to detect and locate laminar damages using a beam forming imaging methodology. Beam forming is using a network of transducers that are used to sequentially scan the structure before and after the presence of damage by transmitting and receiving guided wave pulses. An image of the damage is reconstructed by analysing the cross correlation of the scatter signal with the excitation pulse and enables the detection and location of potential damage areas. The results of simulation and experimental studies show that the method enables the reliable detection of structural damages with locating inaccuracies in the order of a few millimeters within inspection areas of 300 x 300 mm2 using a transducer network of only four transducer elements.

Mechanical Properties of Single-Walled Carbon Nanotubes - A Finite Element Approach

Abstract: In this paper, the mechanical properties, such as the axial and radial Young’s moduli, shear moduli, buckling loads and natural frequencies, of single-walled carbon nanotubes, are estimated by a finite element approach. Each carbon nanotube is simulated as a frame-like structure and the primary bonds between two nearest-neighboring atoms are treated as isotropic beam members with a uniform circular cross-section. In the modeling work, the BEAM4 element in commercial code ANSYS is selected to simulate the carbon bonds and the atoms are nodes. As to the input parameters of the BEAM4 element, they are determined via the concept of energy equivalence between molecular dynamics and structural mechanics, and represented in terms of the force constants of the carbon bonds found in molecular mechanics. Based on this modeling concept, finite element models of both armchair and zigzag types of carbon nanotubes with different sizes are established and the mechanical properties of these tubes are then effectively predicted. Most of the computed results which can be compared with existing results show good agreement. Moreover, the effects of tube diameter, length etc., on the mechanical properties are also investigated.

A study on the nanoindentation behaviour of single crystal silicon using hybrid MD-FE method

Abstract: Developing new techniques for the prediction of materials behaviors in nano-scales has been an attractive and challenging area for many researches. Molecular Dynamics (MD) is the popular method that is usually used to simulate the behavior of nano-scale material. Considering high computational costs of MD, however, has made this technique inapplicable as well as inflexible in various situations. To overcome these difficulties, alternative procedures are thought. Considering its capabilities, Finite Element Analysis (FEA) seems to be the most appropriate substitute for MD simulations in most cases. But since the material properties in nano, micro, and macro scales are different, therefore to use FEA methods in nano-scale modeling one must use material properties appropriate to that scale. To this end, a previously developed Hybrid Molecular Dynamics-Finite Element (HMDFE) approach was used to investigate the nanoindentation behavior of single crystal silicon with Berkovich indenter. In this study, a FEA model was developed based on the material properties extracted from molecular dynamics simulation of uniaxial tension test on single crystal Silicon. Eventually, by comparison of FEA results with experimental data, the validity of this new technique for the prediction of nanoindentation behavior of Silicon was concluded.

Preparation of Polymer-Nanodiamond Composites with Improved Properties

Abstract: An efficient method is developed to achieve improved dispersion of detonation nanodiamond particles in amorphous thermoplastic matrices. For an estimation of the nanodiamond distribution in slices, a method of optical and transmission electron microscopy is used. The complex set of mechanical properties of polymer-nanodiamond composites is considered: tensile properties, Izod impact strength and Brinell hardness. It is found that the reinforcing and toughening effects of uniformly-dispersed nanoparticles on polymer matrices is pronounced at lower loading compared with traditional mixing procedure.

Solution-Responsive Shape-Memory Polymer Driven by Forming Hydrogen Bonding

Abstract: Recently, there is interest in triggering shape recovery of shape-memory polymers(SMPs) by novel non-external heating. In this paper, many hard works have been carried out to make SMP induced by solution. The main challenge in the development of such polymer systems is the conversion of solution-induced effects at the molecular level to macroscopic movement of working pieces. This paper presents a systematic study on the effects of solution on the glass transition temperature (Tg). The results reveal that the hydrogen bonding of shape memory polymer (SMP) was aroused by the absorbed solution that significantly reduces Tg of polymer. The mechanism behind it is solution firstly intenerates polymeric materials till the Tg of polymer lowered down to the temperature of ambient, then hydrogen bonding interaction improves the flexibility of polymeric macro-molecular chains. Thus, the shape memory effect (SME) can undergo solution-driven shape recovery. In addition, it provides a new approach that the SMP can be induced by applying non-energy stimulus. The Dynamic Mechanical Analyzer (DMA) results reveal that the modulus of polymer was softened gradually with immersion time increasing. The experimental result is approximate to the theory.

Sound Transmission through Lightweight All-Metallic Sandwich Panels with Corrugated Cores

Abstract: The transmission of sound through all-metallic sandwich panels with corrugated cores is investigated using the space-harmonic method. The sandwich panel is modeled as two parallel panels connected by uniformly distributed translational springs and rotational springs, with the mass of the core sheets taken as lumped mass. Based on the periodicity of the panel structure, a unit cell model is developed to provide the effective translational and rotational stiffness of the core. The model is used to investigate the influence of sound incidence angle and the inclination angle between facesheet and core sheet on the sound transmission loss (STL) of the sandwich structure. The results show that the inclination angle has a significant effect on STL, and sandwich panels with corrugated cores are more suitable for the insulation of sound having small incidence angle.

Seamless Morphing Wing with SMP Skin

Abstract: Morphing aircraft wings require flexible skins that can undergo large strains, have low in-plane stiffness. In this paper, the sandwiched structure is designed to maintain airfoil shape throughout transition and not to suffer from large out-of-plane deformation under aerodynamic pressure loads. It consists of honeycomb and flexible skin. Honeycomb which is high-strain capable in one direction without dimensional change in the perpendicular in-plane axis provides distributed support to the honeycomb. Flexible skin is used to create the smooth aerodynamic surface. The morphing wing structure is developed together with the sandwiched skin technology. It is capable of changing in chordwise and increasing chord by 20%. Elastomeric and SMP skins are selected for use. Embedded heating wire springs act as the activation system for the SMP. Experiment results show the morphing wing model with elastomeric or SMP skins can be driven successfully by DC motor.

Nanoindentation and micromechanical testing of iron-chromium alloys implanted with iron ions

Abstract: The mechanical properties of Fe-Cr alloys were investigated in as-grown and in post-ion-implanted conditions. Sets of specimens were produced using dual implantations of Fe+ ions to give 1µm deep damaged layers with average damage levels of 0.35 displacements per atom and 5.33 displacements per atom. Nanoindentation was used to measure hardness as a function of depth and showed that implanted material had a higher hardness than unimplanted material. Additionally, micron-scale cantilevers were fabricated from the ion-damaged surface of the material and were tested using a nanoindenter for AFM-imaging and loading. The mechanical properties deduced from the controlled loading of these cantilevers pertain only to radiation-damaged material, and for the high-dose material show significant changes in Young’s modulus, yield stress and work-hardening.

Poisson's Ratio and the Glass Network Topology - Relevance to High Pressure Densification and Indentation Behavior

Abstract: Although Poisson's ratio (ν) is a macroscopic elastic parameter it depends much on the fine details of the atomic packing. Glasses exhibit a wide range of values for  from 0.1 to 0.4 which correlate to the glass network polymerisation degree, hence reproducing at the atomic scale what is observed in cellular materials at the macroscopic scale[1]. As for pure oxide glasses, we found in various multi-component glasses built on ionic-, covalent- or Van der Waals bonds that an increase of Poisson’s ratio corresponds to a decrease of the atomic network crosslink degree[2]. Noteworthy, an extension of this analysis to the case of metallic glasses correlate the recently proposed cluster-like network structure for these glasses[3,4]. A general feature is that a highly cross-linked atomic network results in a glass with a low atomic packing density (large free volume fraction), as exemplified with the case of amorphous silica. The lower the atomic packing density is and the larger the volume change the glass experiences under high pressure (1 to 25 GPa). Indentation experiments with sharp indenters (such as the Vickers one) give birth to hydrostatic stresses of the same order of magnitude and thus induce glass densification. There is hence a direct correlation between ν (reflecting the packing density) and the indentation behavior[5].

Magnesium and magnesium alloys as degradable metallic biomaterials

Abstract: Drawbacks associated with permanent metallic implants lead to the search for degradable metallic biomaterials. Magnesium alloys have been highly considered as Mg has a high biocorrosion potential and is essential to bodies. In this study, corrosion behaviour of pure magnesium and magnesium alloy AZ31 in both static and dynamic physiological conditions (Hank’s solution) has been investigated. It is found that the materials degrade fast at beginning, then stabilize after 5 days of immersion. High purity in the materials reduces the corrosion rate while the dynamic condition accelerates the degradation process. In order to slow down the degradation process to meet the requirement for their bio-applications, an anodized coating is applied and is proved as effective in controlling the biodegradation rate.

Toxicology Studies of a Superparamagnetic Iron Oxide Nanoparticle In Vivo

Abstract: Objectives: This report presents toxicological profile available on a superparamagnetic iron oxide (SPIO) nanoparticle in vivo.

Rapid Prototyping of Constraint-Based Production Flows in Outsourcing

Abstract: In this publication a problem of production order planning is considered. The concept of a critical resource and a critical process, a constraint-based approach has been proposed. The question considered regards of an admissible production flow organization-guaranteeing completion of the production order under assumed limits, while taking into account the logistics constraints imposed. In that context the approach proposed can be seen as one following the Goldratt’s Theory of Constraints (TOC).

Improvement of Fatigue Strength and Impact Properties of Plain-Woven CFRP Modified with Micro Fibrillated Cellulose

Abstract: This study investigated the effect of the enhancement by addition of Micro Fibrillated Cellulose (MFC) on the static, fatigue and impact properties of plain-woven CFRP. Test results showed that the addition of MFC little contributed to the improvement of static properties. However, the initiation of matrix cracks between woven carbon fiber cloths was prevented under cyclic loading so that the fatigue life of the CFRP was improved by the modification with MFC. The ductility of plain-woven CFRP was also acquired under impact load by the addition of the MFC to the matrix.

Microstructure and Characterizations of Portland-Carbon Nanotubes Pastes

Abstract: This research studied microstructure and characterizations of Portland cement with carbon nanotubes (CNTs) which were used as an additive material at 0 %, 0.5 % and 1 % by weight of cement. The compressive and flexural strength tests of mixes were conducted using water/cement ratios (w/c) of 0.5. Samples of mixes were selected for SEM analysis and then ground for TGA analysis. The results show that the compressive strength and flexural strength at all aging time of Portland-CNTs cement composites was higher than that of control mix. Microstructure results show that CNTs was filled in pores between matrix phases to show denser phase and TGA graphs show similar phases to PC mix.