Advanced Materials Research Vols. 341-342

Abstract: Rapid tooling technology is regarded as an important method of reducing the cost and time to market in a new product development process. Epoxy-based composites mold is frequently employed in the intermediate tooling. Based on green manufacturing, an environment friendly process for making epoxy-based composites mold is developed and implemented in this work. This method provided a new, simple, and green manufacturing to produce green rapid tooling without loss of dimension accuracy and surface roughness. The advantages of this method include high yields of the mold fabrication, reducing the cost in the mold fabrication, and environmentally conscious manufacturing. The saving in the cost of the rapid tooling is up to 52.5%.

Abstract: The aim of this study is to produce MWCNT/PMMA nanocomposite with enhanced properties through a modified coagulation method. Samples were prepared in respect to various high filler loadings (1%, 3%, 5%, 7% and 10% wt.). Standard ASTM D790 flexural test was used to evaluate the mechanical properties of the composites. The morphology and surface fracture was observed via Scanning Electron Microscopy (SEM). Thermal stability and electrical conductivity of the composites as a function of MWCNT concentration were measured using Thermo Gravimetric Analyzer (TGA) and UHT Meter, respectively. Flexural strength and flexural modulus of MWCNT/PMMA nanocomposite showed an improvement up to 24.1% and 107.7% compared to the neat PMMA. It was found that the thermal stability and electrical conductivity of the MWCNT/PMMA nanocomposite improved as the concentration of the MWCNT filler increased. These studies therefore demonstrated that MWCNT/PMMA nanocomposite prepared via a modified coagulation method able to successfully improve thermal stability, electrical conductivity and mechanical properties of PMMA.

Abstract: Pure MoSi₂ and MoSi₂ composites with different volume fraction of SiC particles were prepared by the technology of in situ reaction and hot pressing the pure powder of Mo, Si and C after alcohol mixing. The effects of in situ formed SiC particles on the microstructure, the flexural strength and fracture toughness of SiC_P/MoSi₂ composites were studied. The research shows the relative density, flexural strength and fracture toughness of the composites are increased compared with those of the pure MoSi₂ material. It is found that the in–situ formed SiC particles refine the MoSi₂ grains and eliminate the brittle SiO₂ glass phase. The strengthening mechanism of the composites is of the refinement of MoSi₂ grains,dispersion strengthening of the in–situ formed SiC particles and elimination of the brittle SiO₂ glass phase.

Abstract: This paper presents the results of experimental determinations concerning electromagnetic field attenuation in materials containing micro-particles of ashes pyrite in their structure. To know the effect of shielding effectiveness of electromagnetic field electromagnetic absorbents were performed by transmission measurements of attenuation in the frequency range 1-18 GHz. The goal of present paper consits in the realization a composit material with polymeric matrix. The synthetic polymeric matrix used at the obtaining composite is represented by a bicomponent silicone elastomer that strengthens itself at the room temperature by means of a poly condensation reaction. The materials obtained in laboratory contain plated nettling like reinforcement material and ashes pyrite as filling agent. The materials were characterized by X-ray diffraction, transmision diminishing carried out and relative permittivity.

Abstract: Fe₂O₃/Al₂O₃ composite at the mass ratio of 3:2 was prepared by sol-gel combustion synthesis using urea as fuel. The optimized preparation parameters were determined by the robust orthogonal experimental design (OED) method. Standard L₉(3⁴) orthogonal array was adopted, and the four factors were determined as the molar ratio of oxidizer nitrates to fuel urea Ф, relative amount of the deionized water added R_w, ignition temperature and sintering temperature. Range analysis of the relative importance of those four factors on the mean weight loss rate for the reduction of synthesized Fe₂O₃/Al₂O₃ with 50 vol% H₂ indicated that the most influential factor was Ф, sintering temperature, R_w and ignition temperature in the descending order. And the optimized preparation parameters for Fe₂O₃/Al₂O₃ composite were Ф=1, R_w=7.5, ignition and sintering temperatures stabilized as 600°C and 950°C,respectively. Finally, the reaction characteristics of Fe₂O₃/Al₂O₃ prepared by SGCS and the other two reference methods (including sol-gel method and mechanical mixing method) were compared and the results verified that the optimized SGCS was the best option to synthesize Fe₂O₃/Al₂O₃ composite with good reaction performance.

Abstract: Microbial degradation of crop stalk is essentially biochemical processes that microbe and cellulose produced by microbe degrade crop stalk, the reaction has the characteristics of mild reaction conditions, little or no by-product. The degradation transformation process of crop stalk involves many complex chemical and biochemical processes, these bacteria play a key role in transformation process. This paper studied the ferment conditions and process of corn stalk, determined chemical composition before and after degradation and analyzed changes condition. Both degradation rate and the high and low enzyme show the best strain to degrade is Viride 9782, followed by Aspergillum Niger 9532.

Abstract: The main developing trend of automobile industry is promoting performance, lowering fuel consumption, reducing hazard gas emission and promising safety of driving. The automobile lightweight technology has attracted more and more attention recently. Furthermore, auto-body lightweight is very important to automobile lightweight, and new material has become an important technical support for auto-body lightweight. In this paper, the currently used materials in automotive industry were reviewed, and the focus has been put on the application of new lightweight materials in auto-body and the trend of development.

Abstract: High strength concrete (HSC) farther than high compressive strength, possesses uniform high density and very low impermeability, endowing itself with excellent resistance to aggressive environments and disintegrating agencies. But HSC has low flextural strength. Studies have shown that the lack of enough flextural strength of high strength concrete can be compensated by adding steel fibers to the concrete mixture. On the other hand one of the most important environmental problems is the majority of waste spiral steel chips, collected in industrial poles. In this study waste spiral steel chips have been used as steel fibers to reinforced high strength concrete. Also the properties of mixture have been studied. The main properties in this study are including slump of fresh concrete, density, compressive and bending strength of 28-days old specimens. The chips are classified into three different groups according to their shapes and three different categories of test are performed according to percentage of fibers in the mixture. The test results show that any increase in percentage of fibers, will increase the density of specimens and will decreases the slump of mixtures but it will result different behavior of their compressive and bending strength.

Abstract: A simplified efficient finite element method called the inverse approach (IA) has been developed to estimate initial blank and strain distribution in sheet metal forming. This algorithm is an inverse method since the position of points in final shape is known and their corresponding position in the initial blank should be determined. This approach deals with the geometric compatibility of finite elements, plastic deformation theory, and virtual work principle. This method often based on implicit static algorithms, sometimes causes convergence problems because of strong nonlinearities. This paper introduces an initial guess to speed up the convergence of Newton-Raphson solution. The application to a sheet forming example shows good agreement between forward incremental and IFEM results.

Abstract: This paper demonstrates that silica nanoparticles were modified by the four silane coupling agents (KH-151, KH-550, KH-560, KH-570) firstly, then polystyrene/silica (PS/SiO₂) composite microsphere with PS core and silica nanoparticles shell were prepared by Pickering emulsion polymerization. The characterization of optical microscope (OM), scanning electron microscope (SEM), and thermogravimetic analysis ( TGA) illustrates that these microsphere are composed of PS and silica nanoparticles. Silica nanoparticles modified by the different silane coupling agents could form the stable PS/SiO₂ microsphere over 70 °C, while the unmodified silica nanoparticles are difficult to form stable PS/SiO₂ microspheres at the same temperature. The PS/KH-151-SiO₂ microsphere exhibits the least average particle size, while the PS/KH-570-SiO₂ microsphere produces the largest. Both SEM and TGA confirm that microsphere surface exists solid nanoparticles.