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To realize the potential of bioinspired fibrillar adhesive applications ranging from biomedical devices to robotic grippers, there has been a significant effort to improve their adhesive strength and understanding of the underlying adhesion and detachment mechanisms. These efforts include changes to the backing layer, which connects the roots of all of the pillars in the fibrillar adhesive. However, previous approaches such as thickness or elastic modulus changes are selectively advantageous to the adhesive strength depending on the substrate condition because of the trade-off between conformity to misaligned/rough surfaces and increased interfacial stress concentrations. In this work, we explore mechanical divisions (cuts) in the backing layer as a new approach to improve the adhesive strength without this trade-off. We combine experiments and finite element analysis (FEA) to study the effect of the divisions, which decouples the mechanical interaction between the pillars on the divided layers, and show that the adhesive strength can be improved regardless of the substrate condition. Tensile adhesion experiments show increased adhesive strength with cuts to a micropost array (150 μm diameter posts) by approximately 25% for 4 divisions. In situ imaging of pillar detachment shows a transition of the detachment process from a peel-like detachment to a random detachment sequence. FEA simulations of the detachment process suggest that the increased strength may originate from a simultaneous enhancement of the load distribution between the pillars and the compliance of the backing layer.

Cyclic loading leads to interfacial fatigue of a graphene/polymer contact and multimode fracture of the graphene., Graphene is often in contact with other materials through weak van der Waals (vdW) interactions. Of particular interest is the graphene-polymer interface, which is constantly subjected to dynamic loading in applications, including flexible electronics and multifunctional coatings. Through in situ cyclic loading, we directly observed interfacial fatigue propagation at the graphene-polymer interface, which was revealed to satisfy a modified Paris’ law. Furthermore, cyclic loading through vdW contact was able to cause fatigue fracture of even pristine graphene through a combined in-plane shear and out-of-plane tear mechanism. Shear fracture was found to mainly initiate at the fold junctions induced by cyclic loading and propagate parallel to the loading direction. Fracture mechanics analysis was conducted to explain the kinetics of an exotic self-tearing behavior of graphene during cyclic loading. This work offers mechanistic insights into the dynamic reliability of graphene and graphene-polymer interface, which could facilitate the durable design of graphene-based structures.

Despite decades of research, metallic corrosion remains a long-standing challenge in many engineering applications. Specifically, designing a material that can resist corrosion both in abiotic as well as biotic environments remains elusive. Here a lightweight sulfur-selenium (S-Se) alloy is designed with high stiffness and ductility that can serve as an excellent corrosion-resistant coating with protection efficiency of ≈99.9% for steel in a wide range of diverse environments. S-Se coated mild steel shows a corrosion rate that is 6-7 orders of magnitude lower than bare metal in abiotic (simulated seawater and sodium sulfate solution) and biotic (sulfate-reducing bacterial medium) environments. The coating is strongly adhesive, mechanically robust, and demonstrates excellent damage/deformation recovery properties, which provide the added advantage of significantly reducing the probability of a defect being generated and sustained in the coating, thus improving its longevity. The high corrosion resistance of the alloy is attributed in diverse environments to its semicrystalline, nonporous, antimicrobial, and viscoelastic nature with superior mechanical performance, enabling it to successfully block a variety of diffusing species.

Metal-organic frameworks (MOFs) are the coordination polymers of particular interest for targeted drug delivery in a controlled manner. MOFs have several interesting properties in terms of high porosity, large surface area, biodegradable and biocompatible nature for efficient encapsulation of active molecules. We have addressed here the challenge to load the active molecules of benzimidazole group during the synthesis of Cu-MOF. This one-pot approach is advantageous over existing approaches that require multistep post-functionalization for encapsulation of drug-molecules. The prepared MOFs are characterized using FT-IR, UV-Vis spectroscopy, XRD, and SEM analysis. The Cu-MOF are found incipient stable for delivery of active molecules along with high encapsulation efficiency (∼96%).

Over the past few decades, enormous development has been reported in nanosensor technology mainly because of our ever-increasing understanding of nanoscale phenomenon and growth of innovative nanofabrication techniques. Among the different nanomaterials, carbon-based nanomaterials (such as buckminsterfullerene, nanodiamonds, carbon nanotubes/nanofibers, carbon nanodots, graphene) have gained considerable research interest owing to their novel chemical and physical properties. Many of the extraordinary properties of carbon nanomaterials make them ideal transducers in the fabrication of nanosensors for environmental monitoring, healthcare, food safety control, and so forth for the detection of different analytes, e.g., heavy metal ions, food additives, gas molecules, antibodies, and toxic pesticides. This chapter discusses the application of carbon nanomaterials in the development of nanosensors for different analytes. In particular, we describe the significant potential of carbon nanomaterials as highly sensitive platforms and also articulate the research challenges and perspectives confronting this emerging field.

In this study, the feasibility of using carbonaceous nanomaterials was explored for adsorptive removal of methylene blue (MB) and methyl orange (MO) dyes from contaminated water under dark conditions. The morphology and crystalline nature of synthesized carbonaceous nanomaterials (e.g., multi-walled carbon nanotubes [MWCNTs], activated carbon [AC], and their nanocomposite) were characterized by different microscopic and spectroscopic techniques. Furthermore, adsorption experiments were carried out by controlling several key parameters including solution pH, adsorbent dosage, dye concentration, contact time, and temperature. First, the adsorptive behavior of MWCNTs was explained with the aid of adsorption isotherms and kinetics. Thereafter, the adsorptive performance of MWCNTs was compared with those of AC and MWCNTs/AC, and the maximum adsorption capacity (mg/g) of MB/MO was in the order of MWCNTs/AC nanocomposite (232.5/196.1) > MWCNTs (185.1/106.3) > AC (161.3/78.7). The improved adsorption performance (e.g., in terms of adsorption capacity and partition coefficient) of the MWCNTs/AC nanocomposite could be attributed to the presence of more active sites on its surface. Furthermore, their reusable efficiency was in the order of MWCNTs/AC nanocomposite (90.2%), MWCNTs (81%), and AC (67%) after the first step of recovery. The performance of these adsorbents was also evaluated for real field samples. In comparison to MWCNTs and AC, the MWCNTs/AC sorbents offered excellent performance in both single and binary systems, i.e., ~99.8% and 98.7% average removal of MB and MO, respectively.

The excessive discharge of phosphate in water bodies is one of the primary factors causing eutrophication. Therefore, its removal is of significant research interest. The present study deals with the development and performance of highly effective phosphate-adsorbent. Here, we have synthesized MIL-100(Fe) metal-organic frameworks as a facile strategy to effectively remove phosphate from eutropic water samples. The adsorbent was characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM), and wavelength dispersive X-ray fluorescence (WDXRF). The phosphate adsorption performance of MIL-100(Fe) was evaluated with the help of different batch experiments relating to the effect of adsorbent/adsorbate concentrations and the solution pH. The MOF offered a maximum adsorption capacity of 93.6 mg g−1 for phosphate from aqueous solutions with Langmuir isotherm model (R2 = 0.99). MIL-100(Fe) offered an absolute phosphate adsorption performance with a partition co-efficient of 15.98 mg g−1 µM−1 at pH 4 and room temperature conditions. Final experiments with real water samples were also performed to examine the effectiveness of MIL-100(Fe) for phosphate adsorption even in the presence of other ions. These findings support the potential utility of MIL-100(Fe) as nanoadsorbent in phosphate removal for water management.

This article characterizes, experimentally and theoretically, the transport and retention of engineered nanoparticles (NP) through sand filters at drinking water treatment plants (DWTPs) under realistic conditions. The transport of four commonly used NPs (ZnO, CeO2, TiO2, and Ag, with bare surfaces and coating agents) through filter beds filled with sands from either acid washed and calcined, freshly acquired filter media, and used filter media from active filter media, were investigated. The study was conducted using water obtained upstream of the sand filter at DWTP. The results have shown that capping agents have a determinant importance in the colloidal stability and transport of NPs through the different filter media. The presence of the biofilm in used filter media increased adsorption of NPs but its effects in retaining capped NPs was less significant. The data was used to build a mathematical model based on the advection-dispersion equation. The model was used to simulate the performance of a scale-up sand filter and the effects on filtration cycle of traditional sand filtration system used in DWTPs.

Step-by-step tensile tests were applied to flat-braided carbon-fiber-reinforced polymers with and without added dispersions of carbon nanofibers (CNFs) and with and without sample sides cut off to study their mechanical properties and destructive mechanisms by means of in situ observation and stress–strain measurements. An ex situ nondestructive evaluation technique, using a high-temperature superconductor superconducting quantum interference device gradiometer, was also applied to the samples to study their electrical properties; the relationships between the mechanical and electrical properties by visualizing current maps in the samples during ac current injection was also studied. Clear differences were observed in the mechanical and electrical properties and the destructive mechanisms between the samples with and without CNFs and with and without cut off sides. These differences were mainly attributed to the addition of CNFs, which enhanced the mechanical and electrical connections between the carbon fiber bundles.

Experimental and computational investigation of the transport parameters of nanoparticles (NPs) flowing through porous media has been made. This work intends to develop a simulation applicable to the transport and retention of NPs in saturated porous media for investigating the effect of process conditions and operating parameters such, as ion strength, and filtration efficiency. Experimental data obtained from tracer and nano-ceria, CeO(2), breakthrough studies were used to characterize dispersion of nanoparticle with the flow and their interaction with sand packed columns with different heights. Nanoparticle transport and concentration dynamics were solved using the Eulerian computational fluid dynamics (CFD) solver ANSYS/FLUENT(®) based on a scaled down flow model. A numerical study using the Navier-Stokes equation with second order interaction terms was used to simulate the process. Parameters were estimated by fitting tracer, experimental NP transport data, and interaction of NP with the sand media. The model considers different concentrations of steady state inflow of NPs and different amounts of spike concentrations. Results suggest that steady state flow of dispersant-coated NPs would not be retained by a sand filter, while spike concentrations could be dampened effectively. Unlike analytical solutions, the CFD allows estimating flow profiles for structures with complex irregular geometry and uneven packing.

Controlled titanium dioxide (TiO2) thin films were deposited on stainless steel surfaces using the flame-aerosol synthetic technique, which is a one-step coating process that does not require further calcination. Solid state characterization of the coatings was conducted by different techniques, including X-ray diffraction (XRD) spectrum, scanning electron microscope, and atomic force microscope. The coated thin films were used in a gas phase photoreactor for the partial oxidation of hydrocarbons to alcohols and ketones as an alternative production method for the highly sought oxygenates. For this purpose, the oxidation reaction of cyclohexane to form cyclohexanol and cyclohexanone was chosen as a model reaction. The effects of the film thickness, anatase-to-rutile ratio, and particle morphology on the reactivity of the catalyst were studied. Experimental results revealed that there is an optimal film thickness (between 400 and 700 nm) for the photooxidation process that gave a maximum rate of rea...

Braided carbon fiber reinforced plastics (CFRPs) are one of multifunctional materials with superior properties such as mechanical strength to normal CFRPs since the braided CFRPs have continuous fiber bundles. In this paper, we applied the current-injection-based nondestructive evaluation (NDE) method using a HTS-SQUID gradiometer to the braided CFRP for the detection of the breakage of the bundles. We prepared planar braided CFRP samples with and without artificial cracks of 1 and 2 mm lengths, and measured the current density distribution above the samples using the NDE method. In the measurement results, not only a few completely-cut bundles but also the additional partially-cut bundles were detected from decrease in the measured current density along the cut bundle around the cracks. From these results, we showed that it is possible to inspect a few partially-cut bundles in the braided CFRPs by the NDE method.

Processing, mechanical properties, and ablation behavior of SiC fiber/carbon matrix composites for a thermal protection system material of a re-entry vehicle were examined. Orthogonal 3-D woven fabrics ( V f = 0.21, 0.21 and 0.02 for x , y , z directions) made of SiC fibers (Tyranno ZMI) were applied for reinforcement with a carbon matrix formed by polymer impregnation and pyrolysis (PIP) and/or chemical vapor infiltration (CVI). This SiC/CVI-C composite has high ultimate tensile strength of 415 MPa at 25 °C. Air plasma exposure in a plasma wind tunnel revealed no surface recession. The mass loss rate decreased over time. The SiC/C composites exhibit excellent oxidation resistance in high enthalpy plasma air for short durations.

Selective photocatalytic oxidation of 1-phenyl ethanol to acetophenone using titanium dioxide (TiO2) raw and doped with Fe or V, prepared by flame aerosol deposition method, was investigated. The effects of metal doping on crystal phase and morphology of the synthesized nanostructured TiO2were analyzed using XRD, TEM, Raman spectroscopy, and BET nitrogen adsorbed surface area measurement. The increase in the concentration of V and Fe reduced the crystalline structure and the anatase-to-rutile ratios of the synthesized TiO2. Synthesized TiO2became fine amorphous powder as the Fe and V concentrations were increased to 3 and 5%, respectively. Doping V and Fe to TiO2synthesized by the flame aerosol increased photocatalytic activity by 6 folds and 2.5 folds, respectively, compared to that of pure TiO2. It was found that an optimal doping concentration for Fe and V were 0.5% and 3%, respectively. The type and concentration of the metal dopants and the method used to add the dopant to the TiO2are critical parameters for enhancing the activity of the resulting photocatalyst. The effects of solvents on the photocatalytic reaction were also investigated by using both water and acetonitrile as the reaction medium.

Braided carbon fiber reinforced plastics (CFRP) is one of the multifunctional materials for applications to industrial products. We applied the superconducting quantum interference devise (SQUID) nondestructive evaluation (NDE) technique with high magnetic sensitivity and spatial resolution to inspect the state of the fabric in the braided CFRP. We prepared flat braided CFRP samples with nonuniform, uniform and cut-out bundles, which were fabricated with fold biaxial (±45º) tubular fabric and epoxy resin. While injecting ac current into each sample, the diagonal magnetic field gradients dBz/dx and dBz/dy above each sample were measured by the NDE system employing a SQUID gradiometer and xy-scanning stage, and then, the current flow in each sample was visualized by the field-gradient-to-current conversion method. In the measurements, it was shown that the current flowed along the continuous bundles in the cases of nonuniform and uniform samples, and it transmitted between bundles in the case of the sample with cut-out bundles. From these results, we showed the possibility that the NDE method can be applied to the nondestructive inspection of the integrity of the textile of braided CFRP.

The dust of cement furnace is the actual secondary result of cement industry. That, there’s more than three million tons annually aggregated in Egypt, as it representing great danger whether to man and the surrounded environment. This because such dust has harmful effect on environment and beings, especially the close areas from cement factories. That, using of any cement dust quantity considers good solution of environment pollution, which resulted from the recent industry, especially cement. In this research, it uses cement dust to glass mixtures with increased rates may reach 70% of glass composition mixture’s weight, where such rate doesn’t affect the chemical or physical properties of obtained glass, so it shall be suitable to be used in many applicable purpose in this industry.

In this chapter, two examples of our innovative multifunctional composites will be briefly introduced. These innovative composites can contribute toward advancing some new applications of composites through saving energy, efficient management of the thermal energy, and the mitigation of CO2 emissions due to the multifunctionality. The first example is by adding a novel property to composites for developing advanced energy composite materials entitled “Innovative Multifunctional Carbon/Carbon Composites.” This new generation of materials has a unique ability to direct or guide most of the transferred heat by conduction to the desired direction or area of the thermal structure via changing the in-plane thermal conductivity of the material functionally. The second example of our innovative multifunctional composites is for developing smart sandwich composite structures entitled “Innovative Multifunctional Sandwich Composite Structure as Roofs in Snowfall Regions.” These smart lightweight roofs will be able to remove automatically the dropped snow/rain on the roof. Those two innovative multifunctional composites are expected to have a serious impact on the development of new applications of composites where low weight, small size, and high performance are required.

Accepted: 2004-11-23, 資料番号: SA1003438000

Accepted: 2004-02-08, 資料番号: SA1003860000

Accepted: 2004-01-26, 資料番号: SA1003816000

Current detection method was developed to detect damaged area and damage degree of complex defect in electrically conductive composite materials by using superconducting quantum interference device (SQUID) gradiometer. The method was applied to a carbon fiber-reinforced carbon matrix composites (C/Cs) specimen in various damage conditions to investigate the effectiveness of the method. The area and amount of detoured current due to damage in the specimen were successfully detected corresponding to the damage condition. The possibility of the method for classification of the damage condition was discussed.

Accepted: 2002-12-19, 資料番号: SA1003424000

Accepted: 2002-12-16, 資料番号: SA1003310000

In this research, the flexible interphase concept was introduced to enhance the poor mechanical properties of jute fiber reinforced unsaturated polyester matrix composites. The jute cloth reinforcement was obtained from recycled coffee bags. These jute cloths after washing by water and drying were soaked in mixture of Polybutadiene Epoxydied as flexible resin and acetone for 10 seconds. Several mixtures consist of 0, 2, 3.5, 5 and 8 wt% of Polybutadiene Epoxydied and 100, 98, 96.5, 95 and 92 wt% of acetone, respectively, to form flexible interface around the jute fibers. Jute cloth reinforced unsaturated polyester matrix composites with different flexible interphase incremental weight ((Wa-Wb)/Wb) ratios were fabricated by hand lay-up method and examined by a series of mechanical tests. The mechanical testing including tensile, bending, Izod strength impact and drop impact was carried out for these composites to evaluate the effect of the flexible interphase and acetone on the jute cloth composites. The flexible interphase succeed to control the mechanical properties of jute fiber reinforced unsaturated polyester matrix composites. Inserting flexible interphase between unsaturated polyester matrix and jute fibers leads to smooth fluctuation, less matrix cracking, in the second part after the knee point of each stress-strain curve as exhibited in composites with higher flexible interphase incremental weight ratio. This means not only the brittle matrix but also interface/interphase dominates the multiple matrix cracking behavior in jute cloth reinforced unsaturated polyester matrix composites. Inserting flexible interphase between unsaturated polyester matrix and jute fibers leads to less number of multiple cracking as shown in the second portion of flexural stress-displacement curve. This means the number of multiple cracking are dominated by flexible interphase. The impact strength of jute cloth reinforced unsaturated polyester matrix composites with flexible interphase incremental weight ratio of 1.2% is higher than that of jute cloth reinforced unsaturated polyester matrix composites without flexible interphase by about 45%. The impact energy after maximum load has increased significantly with all flexible interphase incremental weight ratios.Copyright © 2012 by ASME

Recycled needle punched jute fiber mats as a first natural fiber reinforcement system and these jute mats used as a core needle punched with recycled jute fabric cloths as skin layers as a second natural fiber reinforcement system were used for unsaturated polyester matrix composites via modifying the hand lay-up technique with resin preimpregnation into the jute fiber in vacuum. The effect of skin jute fabric on the tensile and bending properties of jute mat composites was investigated for different fiber weight contents. Moreover, the notch sensitivity of these composites was also compared by using the characteristic distance d o calculated by Finite Element Method (FEM). The results showed that the tensile and flexural properties of jute mat composites increased by increasing the fiber weight content and by adding the jute fabric as skin layers. On the other hand, by adding the skins, the characteristic distance decreased and, therefore, the notch sensitivity of the composites increased. The fracture behavior investigated by SEM showed that extensive fiber pull-out mechanism was revealed at the tension side of jute mat composites under the bending load and by adding the jute cloth, the failure mode of jute mat was changed to fiber bridge mechanism.

Ceria nanoparticles are used for fuel cell, metal polishing and automobile exhaust catalyst; however, little is known about the impact of their release to the environment. The stability, transport and deposition of engineered CeO2 nanoparticles through water-saturated column packed with sand were studied by monitoring effluent CeO2 concentration. The influence of solution chemistry such as ionic strength (1–10 mM) and pH (3–9) on the mobility and deposition of CeO2 nanoparticles was investigated by using a three-phase (deposition-rinse-reentrainment) procedure in packed bed columns. The results show that water chemistry governs the transport and deposition of CeO2 nanoparticles. Transport is significantly hindered at acidic conditions (pH 3) and high ionic strengths (10 mM and above), and the deposited CeO2 particles may not be re-entrained by increasing the pH or lowering the ionic strength of water. At neutral and alkaline conditions (pH6 and 9), and lower ionic strengths (below 10 mM), partial breakthrough of CeO2 nanoparticles was observed and particles can be partially detached and re-entrained from porous media by changing the solution chemistry. A mathematical model was developed based on advection-dispersion-adsorption equations and it successfully predicts the transport, deposition and re-entrainment of CeO2 nanoparticles through a packed bed. There is strong agreement between the deposition rate coefficients calculated from experimental data and predicted by the model. The successful prediction for attachment and detachment of nanoparticles during the deposition and re-entrainment phases is unique addition in this study. This work can be applied to access the risk of CeO2 nanoparticles transport in contaminated ground water.

Jute fiber mat reinforced unsaturated polyester matrix composites having different fiber weight contents (11, 22, 32 wt%) were fabricated by modifying the hand lay-up technique with resin pre-impregnation into the jute mats in the vacuum. Tension and three-point bending tests were carried out to evaluate the effect of fiber contents on these mechanical properties of above-mentioned composites. The results showed that as the fiber weight content increases, tensile strength and modulus increase and the improvement had occurred at 22 wt% of fiber weight content with respect to that of neat resin. As the fiber weight content increases, flexural strength and modulus increase and the improvement had occurred at 11 and 32 wt% fiber contents for the flexural modulus and strength respectively compared to those of neat resin. Fiber pull out mechanism is the failure mode revealed at the fracture surfaces under tensile loading as well as at tension side of composites under bending loading.Copyright © 2011 by ASME

The goal of this research is to provide a sufficient understanding for the damage mechanism of ±45° flat braided CFRP composites under tensile loading based on in-situ macroscopic observations of surface cracking and off-line measurements for the state-of-fibers by Superconducting Quantum Interference Device (SQUID) technique to analyze the effect of the continuously oriented of all braided fiber bundles on the tensile and in-plane shear properties. SQUID technique displays an effective capability in inspection the state-of-fiber failure, whereas the in-situ surface macroscopic observation technique is very useful in observing the surface matrix cracking at different stages of damage. The damage mechanism of uncut-edges and cut-edges of ±45° flat braided CFRP composites are identified adequately by the above-mentioned experimental procedure. The cut-edges ±45° flat braided CFRP composites exhibit a pure shear damage mechanism associated with large shear deformation and no significant fiber failure, while the uncut-edges ±45° flat braided CFRP composites exhibit a slight fiber scissoring mechanism followed by a partially fiber failure. The enhancement of the tensile and in-plane strengths of the uncut-edges ±45° flat braided CFRP composites by about 60% higher than those of the cut-edges ±45° flat braided CFRP composites achieves not only by the effect of the continuously oriented carbon fibers at the edges but also by the effect of re-orientation of braiding fiber bundles with smaller angle than the original ±45° braiding angle of the fabricated composites, or so called fiber scissoring mechanism in composites.Copyright © 2011 by ASME

Fracture toughness tests for cross-ply laminated carbon-carbon composites (0/90 C/Cs) with various ply ratios of 0:90 fiber orientations were carried out to compare the fracture behavior. These experiments aimed not only to evaluate the formation of shear bands that might be extended from the notch tips by different extension lengths when change the stacking sequence but also to elucidate the interaction between 0 and 90 layers in case of stacking sequence 1:1. The fracture pattern for notched C/Cs (compact tension specimens) was found to transfer from the macro-mode I to macro-mode II when 0 plies fraction increased and transition occurred at ratio equal to 0.53. Thus, shear bands were not observed in the 2D C/Cs with the ratio less than 0.53 even in microscopic level but clearly observed zigzag cracking in 0 layers, splitting in 90. This zigzag crack was yielded due to the interaction between 0 and 90 layers in these materials. The zigzag crack with partial delaminations releases a large amount of energy, which gives rise to high fracture toughness in cross-ply C/C composites.

In laminated flat braided composites there are no fibers through the thickness direction except at the edges due to the fiber continuity of the braiding technique. A delamination along the interlaminar planes can be propagated because of the lack of fibers in the Z- or third-direction to the composite. The delamination initiates essentially as a result of arising the stresses concentrations around the transverse or matrix cracks that appear due to the mismatch of the thermal expansion coefficients of the fibers and matrix during the fabrication process. The delamination renders low interlaminar composite properties and represents a fundamental weakness of laminated flat braided composites especially with increasing the braiding angle, and thus minimizes the shear stress transfer. In this research, laminated flat braided carbon fabrics were performed via flattening tubular braided fabrics with braiding angle of ±45° by applying carefully compressive loads laterally on the tubular fabrics. Then, carbon fiber reinforced epoxy matrix composites were fabricated from the above-mentioned biaxial fabrics with and without uniformly dispersed carbon nanofibers throughout the epoxy matrix. Three loading percentages of carbon nanofibers (specifically, 0.5, 1, and 2 wt%) were dispersed in the matrix of the composites to enhance the matrix and interlaminar/inter-ply properties. The influence of matrix and interlaminar properties improvements on the in-plane tensile and shear response of the laminated flat braided composites was clarified via conducting of ±45° laminates tensile tests. The experimental results of tensile tests revealed that the tensile and in-plane shear properties as well as the fracture behavior of the composites are substantially influenced by the incorporation of the dispersed carbon nanofibers in the matrix of the composites. A pulsed thermography technique was used to inspect the occurrence of the delamination after the fracture under tensile loadings. The thermal wave image and logarithmic temperature-time curves of the pulsed thermography inspection illustrated that the composites with dispersed carbon nanofibers rendered higher interlaminar properties than that of composites without nanofibers. The main conclusion of this research can be summarized that dispersion of carbon nanofibers through the epoxy matrix of laminated flat braided composites is not only enhanced the matrix properties but also improved the interphase morphology between the composite plies that maximized the stress transfer of the composites. In other words, the fabricated braided composites with braiding angle of ±45° are predominantly by both of matrix and interlaminar properties.Copyright © 2008 by ASME

Recently, increasing demands for smarter and smaller products calls for the development of multifunctional composites. These materials are used not only as structural materials but also satisfy the needs for additional functionalities such as thermal, electrical, magnetic, optical, chemical, biological, etc. In this research, a novel carbon nanotubes dispersion approach leads to a new generation of multifunctional composites with additionally novel thermal functionality, we called it heat-directed functionality. These distinctive composites have unique capability which can conduct the majority of the transferred heat by conduction to the preferred area or direction of the thermal structure. This unique heat-directed property can be attained by varying the in-plane thermal conductivity. Varying the in-plane thermal conductivity of the composites functionally is achieved by dispersing highly heat-conductive materials such as carbon nanotubes throughout the matrix functionally, not uniformly. Therefore, in this research three phase carbon/carbon composites have been fabricated with functionally dispersed carbon nanotubes throughout the carbon matrix of continuously plain woven carbon fiber fabrics in order to attain this useful property. The fabricated heat-directed carbon/carbon composites have been examined experimentally and numerically. The in-situ full-field infrared measurements and finite element analysis of the designed composites showed that the heat transfer direction can be substantially controlled by just functionally dispersed a few percentages of carbon nanotubes through the matrix of traditional long carbon fiber-reinforced carbon matrix composites. This exceptional property can play a significant performance improvement in heat transfer process along the in-plane of the materials as well as helping to decrease the heating up of the Earth, global warming, due to the escaped heat of many engineering applications. In other words, the efficient heat energy management or heat energy saving via using the introduced multifunctional carbon/carbon composites with heat-directed functionality can significantly help with both sides of the equation of efficient energy consumption and friendly-environment applications.Copyright © 2008 by ASME

Three braided carbon fiber reinforced polymer (CFRP) samples with different middle-end fibers were fabricated. Damage mechanisms of the samples under step-by-step tensile loading were investigated using a nondestructive evaluation (NDE) method utilizing a high-temperature superconducting SQUID gradiometer. Commercial carbon fibers UTS50 were used for base braided fabrics, while UTS50, XN05 with higher electric resistivity, and XN60 with lower resistivity were used for the middle-end fibers. In the step-by-step tensile tests, observation of surfaces and measurements of stress-strain curves of the samples were carried out. At certain damage stages, the SQUID NDE method, which visualizes flowing currents in the samples, were applied to detect damage and assess the integrity of the carbon fiber yarns in the samples after removal of the loading. As a result, different damage mechanisms and stress-strain curves were observed and measured. From the results using the SQUID NDE method, it was shown that the current distributions in the samples were determined by the middle-end fibers at respective virgin stages, and the middle-end fibers XN60 were broken in some parts of the sample at its final fracture.

In this paper, visualization of flowing current in various braided carbon fiber reinforced plastics (CFRPs) was demonstrated using high-temperature superconductor (HTS) superconducting quantum interference device (SQUID) gradiometer, in order to study electrical properties and integrity of the braided CFRP samples. Step-by-step tensile loading was also applied to the samples, in order to study their mechanical properties and destructive mechanism. Experimental results indicated that the addition of carbon nano fibers and middle-end carbon fiber bundles attributed to modify not only the mechanical properties, but also the electrical properties of the samples. Combining the results by the both methods, a scenario of the destructive mechanism of one sample was estimated.

Carbon fiber reinforced polymers (CFRPs) are composite materials with lightweight and high specific strength. As the braided CFRPs have continuous carbon-fiber bundles in their longitudinal direction, they are stronger than conventional CFRPs. In this study, we applied a current-injection-based NDE method using a HTS-SQUID gradiometer to the flat braided CFRPs with and without carbon nanotubes (CNTs), and estimated conditions of the carbon fibers while applying a step-by-step tensile load to the CFRPs. From the results, a possibility to predict an initiation site of the destruction in the braided CFRPs was demonstrated.

Exhaust gas recirculation (EGR) strategy has been recently employed in natural gas SI engines as an alternative to lean burn technique in order to satisfy the increasingly stringent emission standards. However, the effect of EGR on some of engine performance parameters compared to lean burn is not yet quite certain. In the current study, the effect of both EGR and lean burn on natural gas SI engine performance was compared at similar operating conditions. This was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. The combustion model was validated using experimental data and a good agreement between the results was found. It was demonstrated that adding EGR to the stoichiometric inlet charge at constant inlet pressure of 130 kPa decreased power more rapidly than excess air; however, the power loss was recovered by increasing the inlet pressure from 130 kPa at zero dilution to 150 kPa at 20% EGR dilution. The engine fuel consumption increased by 10% when 20% EGR dilution was added at inlet pressure of 150 kPa compared to using 20% air dilution at 130 kPa. However, it was found that EGR dilution strategy is capable of producing extremely lower NO emission than lean burn technique. NO emission was reduced by about 70% when the inlet charge was diluted at a rate of 20% using EGR instead of excess air.

Natural gas has been recently used as an alternative to conventional fuels in order to satisfy some environmental and economical concerns. In this study, a natural gas spark-ignition engine employing cooled exhaust gas recirculation (EGR) strategy in a high pressure inlet condition was optimized. Both engine compression ratio and start of combustion timing were optimized in order to obtain the lowest fuel consumption accompanied with high power and low emissions. That was achieved numerically by developing a computer simulation of the four-stroke spark-ignition natural gas engine. A two-zone combustion model was developed to simulate the in-cylinder conditions during combustion. A kinetic model based on the extended Zeldovich mechanism was also developed in order to predict NO emission. In addition, a knocking model was incorporated with the two-zone combustion model in order to predict any auto-ignition that might occur. It was found that the value of the compression ratio at which the minimum fuel consumption occurs varies with the engine speed. A minimum fuel consumption of about 200 g/kW h was achieved at an engine speed of 1500 rpm, inlet conditions of 200 kPa and 333 K, and a compression ratio of about 12. Also, it was found that cooled EGR can significantly reduce NO emission at high compression ratio conditions. NO emission decreased by about 28% when EGR was increased from 20% at compression ratio of 10 to 27% at compression of 12 at the same engine speed of 3000 rpm.