Advanced Materials Research Vol. 702

Abstract: In this study, we evaluated water absorption and tensile properties of coconut filter fiber reinforced polypropylene composites. The fibers were subjected to various immersion times for 0.5, 1, and 3 h in 0.5 % acrylic acid solution at room temperature and 0.5 h at 70 oC. The treated fibers were used as reinforcement of polypropylene composites. Water absorption of treated fiber composites was lower than those of untreated fiber composite. Boiling in water significantly affect water absorption rate of the composites. The tensile strength and elastic modulus of treated fiber are higher than untreated fiber. They show a decrease in tendency when the immersion time increased. Tensile strength and elastic modulus of composites with AA-treated at 70 oC fiber are the highest.

Abstract: 2D C/SiC ceramic matrix composite (CMC) displays significant damage characteristic coupled with inelastic strain under tension and shear loads, which should be considered in the constitutive model. In this study, a continuum damage mechanics (CDM) model was proposed for this material, in which the process degradation of the material property was described by introducing a set of scalar damage variables, and the damage-coupling effect was also considered. Meanwhile, isotropic hardening theory was applied to form the evolution rule of inelastic strains. The model was then implemented into the UMAT in ABAQUS software and validated by comparison between the simulation and experiment results.

Abstract: As lack of organic carbon source is a key problem for biological denitrification, hemp fiber, PBS, PLA and PE were selected as raw materials, then four kinds of slow-release carbon source composite materials were prepared by 35A-double-screw extruder and used for biological denitrification. Their performan- ces were detected through static and continuous experiments. The results showed that in the static experiments, release carbon abilities of HB20 and HB40 were both not good, their COD_Mn were 5.42 and 12.83mg/L respectively; In the continuous experiments, NO₃-N removal rate of HLE decreased from 57.9% to 13.1% within 30 days. HBE could cause a continuous release of dissolved organic compound. In the operation of 66 days, above 96.0% NO₃-N was removed and NO₂-N level was below 0.02mg/L when influent NO₃-N =30.0mg/L and HRT=24h. HBE was the most suitable carbon source carrier material for biological denitrification.

Abstract: The cathode material La_0.7Sr_0.3CuO_3-δ was synthesized by a sol-gel method. X-ray diffraction revealed it to be form a single phase of perovskite. The SDC（Sm_0.15Ce_0.85O_1.925）was synthesized by glycine-nitrate processes. The 90%SDC and 10%YSZ powders are mixed to prepare as SDC-YSZ composite electrolyte. The high temperature electrical conductivity of La_0.7Sr_0.3CuO_3-δ was measured by using the four-point dc technique, and cathodic overpotential with SDC-YSZ composite electrolyte support was measured by using a current-interruption technique. Using La_0.7Sr_0.3CuO_3-δ as cathode and 65%NiO/SDC as anode based on SDC-YSZ composite electrolyte one can obtain high current density and power density at intermediate temperatures.

Abstract: We investigated two formula-units of Li_1.5Mn_0.5As alloys, such as Li₃MnAs₂, in the Cu₂Sb crystal structure using an ab-initio algorithm. By interchanging Mn with each Li located at different positions of the Li₄As₂ unit cell, four separate alloys are formed. At the optimized lattice constant, two of these alloys are predicted to be ferromagnetic metals and the other two are half metals. The possibility of half metallicity in the first two is also explored. Both the modified Slater-Pauling-Kübler rule and the ionic model can characterize the magnetic moments of the half metals.

Abstract: p-CdTe film has been deposited on n-Si(111) substrate by thermal evaporation technique. The prepared CdTe/Si heterojunction diodes have been annealed at 573K. The capacitance-voltage measurements have studied for the prepared heterojunctions under 2 KHz frequencies. The capacitance-voltage measurement indicated that these diodes are abrupt. The capacitance at zero bias, the built in voltage and the doping concentration increased after annealing process while the zero bias depletion region width is decreased. The carrier transport mechanism for CdTe/Si diodes in dark is tunneling-recombination. From current-voltage measurement at dark, the values of ideality factor are 2.9 and 3.8. The values of reverse saturation current are 3.77×10^-7 and 9.36×10^-8 Amperes.

Abstract: Al honeycomb core sandwich composite panels have different core and plate materials. The core is the Al honeycomb core, and the thin plate is GFRP sheets with fibers laminated in the 0°/90° symmetric structure. The Al honeycomb core sandwich composite panel is used for structures, which involve relatively high bending load. Before designing the structures, their stability is evaluated via the finite element analysis. In this study, an analysis method that is closest to the reality was proposed for designing the structures with Al honeycomb core sandwich composite panels. For that purpose, the modulus was reviewed. In the finite element analysis, the tensile modulus is generally used. In the results of this study, however, the tensile modulus led to significant deviations from the test results, whereas the bending modulus led to a closer value to the test results.

Abstract: The purpose of the paper is modeling of nonlinear vibrations and stability of movement of boring columns at finite deformations. Movement of boring columns for shallow drilling (up to 500 m) applied in oil-gas extractive industry is considered. Nonlinear models of movement of acompressed-torsioned drill rod within the nonlinear theory of finite deformations of V.V. Novozhilov are constructed. A method for its analysis and criterion of dynamic stability are offered. The numerical analysis of its elastic dislocations and instability zones of the basic resonance is carried out, which confirm the efficiency of the offered nonlinear dynamic model of rod elements and techniques for their calculation.

Abstract: Currently industrial needs exceed traditional design approach solutions. To satisfy that need designer have to deal with mutually exclusive restrictions. The solution to this problemis to maintain these restrictions with proper methodthat guarantees right result. The concrete casting matrixes are not only transits beauty and art but they have also important technical sense in final product. The master model represents the final product a concrete sidewalk brick which have specified form of the top surface. This special structure of the top surface helps drain water off the brick in order to maintain proper griping properties of it after it rains. As soon as the master model wasscannedit was necessary to change outer border line of 3D model because themaster model appeared to be a little bit bigger than the original one. Finally the 3D model it is the outer border line and its geometry were modified in order to keep the original model functionality. All modifications were done with application of reverse engineering and CAD/CAM software.

Abstract: The article deals with surface roughness characteristics of polyamide APA after the turning by tool with linear cutting edge. The experiment was centred on the obtaining of Ra and Rz dependences on both cutting speed and feed per revolution concurrently. Polyamide APA allows the production of very large structural and semi-structural parts for automotive and non-automotive applications including interior, exterior and under-the-hood applications. It also allows reducing the total cost of production, especially for lower volume parts. Therefore, the authors deals with the possibility to work this material. The special cutting tool was selected in regard to the author´s previous experiments. The surfaces of investigated metal samples, which were machined by the tool with linear cutting edge, achieved very good properties, so it was the reason for the using of this tool at the experiments presented in the article. Obtained values of surface roughness characteristics were worked up by means of regression analysis and according to the rules for statistical data processing. The results are arranged into the table and consequently into the graphical presentations. The shapes of chips at the machining within various working conditions are shown at the end of the article. Next experiments will be focused on the machining of other types materials with the same unconventional cutting tool and for the obtaining new data that characterize the machined surface.