Advanced Materials Research Vols. 79-82

Abstract: The flight mechanics of dragonflies including hovering and taking off backwards, flight sideways and vertical directions has been attentions in Bionics. The dragonfly wing consists of the networks of various veins and membranes to make the structural properties complicated. In the past investigations, surface characteristics of dragonfly wing were measured by nanoindentation test. Thus the aim of this study will comprehensively concern the nanomechanical properties of veins, membrane and pterostigma of the wing of the dragonfly with nanoindentation. In the mean time, the modulus and hardness of the wing of the dragonfly’s composites including lengthwise vein, transverse vein, membrane and pterostigma are measured. The value of modulus of lengthwise vein is greater than the other structures. The value of modulus of transverse vein is the smallest due to its soft behavior. Its hardness is also smaller than others.

Abstract: As a new type of protection design, composite armor structures have good performance in impact resistance, and have been widely used in ship structure protection. Due to its academic value and potential applicability, the dynamic characteristics of ship composite armor structures were studied in this paper. The whole process of the shaped charge’s explosion and penetration, and the ship composite armor structures’ damage response were described. According to the numerical simulation with Ansys-Autodyn, it was found that the ship composite armor structures were damaged not only by the explosively formed projectile but also by the detached shock wave in the conditions of contact underwater explosion and the thickness of composite armor structures was the main factor effecting the impact resistance properties.

Abstract: Theoretical study on the electronic structure of small FemAln(m+n=6) clusters has been carried out at the BPW91 level, and the electronic structures, binding energy and vertical ionization potential of clusters were evaluated. For the stable clusters, the iron atoms gather together and form a maximum of Fe-Fe bonds, and the aluminum atoms locate around Fe core with a maximum of Fe-Al bonds. The binding energy and vertical ionization potential show that the Fe5Al, Fe4Al2 and Fe3Al3 clusters have higher stability, which results provide insight into the properties of iron-aluminides can be obtained from a finite size cluster model.

Abstract: The lattice parameters, five independent elastic constants and the bulk modulus B on the applied pressure of hexagonal boron nitride (h-BN) are calculated by using a first-principles pseudopotential method. The calculation results are in good agreement with the experimental and theoretical values. It is found that the most stable structure of h-BN corresponds to the axial ratio c/a of about 2.652.

Abstract: Without the protection of inert gases or vacuum environment, rod-like Bi2S3 and cubic-shaped PbS microcrystals were synthesized directly via pyrolyzing corresponding metal diethyldithiocarbamates in air at 300 °C for 3 h. The products have been characterized by X-ray diffraction and scanning electron microscope, and their possible formation mechanisms were also tentatively proposed. Furthermore, control experiments with multiple-source precursors revealed that our single-source precursors played an important role in preparing phase-pure Bi2S3 and PbS.

Abstract: In this article a methodology based upon micromechanical analysis of multiple damage events is developed to predict stress-strain response and failure behavior of fiber-reinforced polymers composites under tensile loading, by considering the effect of variations in fiber strength and local shear failure of the matrix. A simulation scheme coupled with Monte-Carlo method including these failure mechanisms is proposed to investigate failure process and determine ultimate strength of the composites. It is shown that the size dependence of composite ultimate strength is dominated by fiber strength statistics and stress distribution due to progressive microdamage.

Abstract: Multi-walled carbon nanotubes (MWNTs)-Fe3Al was prepared by spark plasma sintering. Microstructural investigations show that MWNT remains in the composites. The magnetic properties were investigated with alternating gradient force magnetometer, which shows that the composites still display good soft magnetic property. The MWNTs-Fe3Al composites have a similar magnetic hysteresis loops to that of Fe3Al, indicating the good soft magnetic properties of the composite. Excellent magnetic property implies that MWNT-Fe3Al composites may also have significant potential for applications in electronic-magnetic nanodevice fields.

Abstract: A novel synthesis method on solvent-free reaction using improved jet milling was described. Synthesis of a schiff base derived from p-hydroxybenzaldehyde and p-aminobenzoic acid had been achieved by solvent-free reaction using improved jet milling, and the structure of the compound have been characterized by Fourier transform infrared spectrometer, 1H nuclear magnetic resonance techniques and mass spectrometry. Differential thermal analysis of reaction process shown that the reaction was complete within 6 min. The scanning electron microscopy shown that the particles of the schiff base were regular and the size of the most particles was 0.5~1 μm. At the same time, the theoretical analysis about reaction process of solvent-free reaction using improved jet milling was preliminary studied. This solvent-free reaction using improved jet milling not only involves mild conditions, a simple operation and short reaction time, but also gives quantitative yield without waste producing work-up procedures. Simultaneously, the investigation also showed this reaction method was feasible, and of benefit to environment.

Abstract: Ion exchange resin (IER) mixed polyethersulfone (PES) hybrid membranes were prepared by a phase inversion method, using polyethyleneglycol-400 (PEG-400) and polyvinyl pyrrolidone (PVP) as additives. Two different types of resin, D201 and D061, were incorporated into polyethersulfone dope solution separately with intention of producing highly permeable and hydrophilic membranes. The effect of filler on morphology, pure water permeation, and rejection of bovine serum albumin (BSA) was investigated. It was found that the morphology of hybrid membranes showed a typical asymmetry structure. The amount of IER, the concentration of additives and the temperature of coagulation bath showed to be powerful factors to influence the pore size and pure water flux. Membranes prepared from a solution containing PES concentrations from 13wt% to 15wt%, the pure water flux decreased from 244.6 to 97.5 L/(m2•h). And PVP could serve as an additive to render the hybrid membrane hydrophilic. High values of BSA rejection capacity were performed by the resin mixed polyethersulfone hybrid membranes.

Abstract: A NFE model is constructed to analyze the convective heat transfer steady thermal stress in a ceramic/FGM/metal composite EFBC plate with temperature-dependent material properties. Based on thermoelasticity theory, we derive the NFE basic equation of heat conduction of the plate. We present a Sinpson method for the solution of steady thermal stress formulas of the composite plate. Using FORTRAN language we design the calculation software. From numerical calculation, when , T0=300K, Ta=500K and Tb=1 650K, the stress distributions in the plate were obtained. The results are as follows. With the increase of the FGM gradient layer thickness, the stress distribution is more reasonable, and the largest tensile stress of the EFBC composite plate reduces by 59.6%. With the increase of M, the stress change increases obviously in metal and ceramic layers, and the thermal compressive stress on the ceramic surface reduces by 78.1%. With the increase of porosity, the change of stress at the bonding interfaces increases, and the thermal compressive stress on the surface of ceramics reaches the maximum, and the thermal tensile stress on the surface of metal reaches the maximum too. Compared with , when , the tensile stress on the metal surface reduces by 91.3%, and the maximum compressive stress on the surface of ceramics increases 4.55 times. Compared with the nongraded two-layered ceramic/metal composite plate, the thermal stress of ceramic/FGM/metal composite EFBC plate is very gentle, and the maximum tensile stress reduces by 62.94%. When we consider the temperature-dependent material properties, the stress in graded three-layered composite plate becomes small obviously, and the maximum tensile stress in the plate reduces by 36.74%, and the maximum compressive stress on the ceramic surface reduces by 31.4%. The model can effectively analyze the thermal stresses and effect factors in a ZrO2/FGM/Ti-6Al-4V composite plate. The results provide the foundations of theoretical calculation for the design and application of the composite plate.