Advanced Materials Research Vols. 194-196

Abstract: The composite components with irregular shape are often used in many application areas. Normally the formation of the composite components with irregular shape is by laminated technology. However the main problem of laminated composites is that there is a pure resin area between two lays which will degrade the mechanical properties of composite components. Three dimensional (3D) integrated braided composite can overcome this problem. In this paper, the design and manufacture technology of 3D integrated braided composite support with irregular shape were researched, including: braiding technology of 3D braided preform of composite support, the determination of process parameters of resin transfer molding(RTM) for 3D braided composite support, and the design of mold for consolidation of composite support. The compress property and shear property of this composite were investigated. The maximum compress force borne by this composite support is 2.31 kN, which is more than the design value of 1.90 kN and the maximum shear force borne by this composite support is 4.48 kN, which is more than the design value of 4.10 kN. The weight of 3D braided composite support is only 60.27% of the weight of titanium support.

Abstract: One new kind of epoxy resin toughening agent defined as liquid crystalline polyurethane elastomers (LCPUE) containing mesogenic ester groups and trithylene glycol flexible chain was synthesized and its nematic structure was observed by POM and XRD. The LCPUE was to modify the epoxy resin (E-51). The mechanical properties, fracture surface morphology, and thermal properties of the E-51/LCPUE curing system were systematically investigated. Experimental results revealed that the impact strength of the epoxy resin modified with LCPU is 1.9 times higher than that of the unmodified system, enhanced the thermal decomposition temperature by about 12 °C, and the fracture surfaces all modified systems display tough fracture feature.

Abstract: Being inherently safe and chemically compatible with the electrolyte, lithium titanate is considered alternatives to carbonaceous anodes in Li-ion batteries. Given the commercial success of the spinel lithium titanate, carbon coated lithium titanate, particularly in nano structured forms, have been fabricated and investigated for the applications. Nano structuring leads to increased reaction areas, shortened Li+ diffusion and potentially enhanced solubility/capacity. This paper reviews structural characteristics and electrochemical reactivity, along with synthetic approaches of carbon coated nanostructures and nano-composites based on lithium titanate, recently.

Abstract: A novel nanocomposite films was prepared by dispersing SiO₂ nanoparticles in aqueous konjac glucomanan (KGM) solution. The structure and miscibility of the nanocomposite materials were determined finely by viscosimetry, Fourier transformed infrared spectra (FTIR), micropolariscope (POM), scanning electron microscopy (SEM) and ultraviolet-visible spectrophotometer (UV-Vis). The results indicated that there was a strong interaction between KGM and SiO₂ in ethanolamine. The miscibility and ultraviolet-absorption properties of KGM/SiO₂ nanoparticles blend film were improved by ball milling treatment. Moreover, the ultraviolet absorption and tensile strength of the nanocomposite films rapidly increase with the increase of SiO₂, while breaking elongation of the nanocomposite films slightly decreased.

Abstract: The texture development was investigated in the extruded Al and Al metal matrix composites (MMCs) reinforced with SiC particles of different sizes and volume fractions. During extrusion, both the unreinforced Al and the MMCs develop a strong fiber texture with two components: <111> and <100>. When SiC is introduced into aluminum, the main component of texture is not modified, but the intensity of the component evolves with the volume fraction and average size of SiC particles. For the MMCs reinforced with 3.5μm SiC particles, the texture intensity of the Al matrix tends to decrease as the SiC volume fraction increases, and it is lower than that in the unreinforced Al. However, for the MMCs reinforced with 25 nm and 150 nm SiC particles, the texture intensity of the Al matrix is higher than that in the unreinforced matrix, and it increases with increasing the SiC volume fraction. It is found that superfine particles may introduce some new component into the deformation texture, and the texture intensity increases as the SiC particle size decreases.

Abstract: The constant temperature drying experiment on wheat straw at different initial moisture content and drying temperature were made with comprehensive thermal analyzer. The impact of initial moisture content, drying temperature and drying time on wheat straw procedure were reviewed, and the optimum drying result of wheat straw were gotten when initial moisture content was 32.5% and drying temperature was 100°C .The process of wheat straw drying was divided into three sections about preheating, constant temperature and falling rate drying. Regression equations on different sections were established by regression analysis, the result show that parabolic equation in preheating section, linear equation in constant rate drying section and power curve in falling rate drying section. Experiment data and reference frame from conclusion above were useful to crop straw drying technology.

Abstract: Many flexural or tensile reinforced concrete members must be crack-free or the crack widths must be within specified limit value at service load levels. Presently, there are a number of structure members cannot satisfy its designed serviceability, due to the degradation of structural materials (due to durability problems) or by an increase in design loads. The use of bonding CFRP sheets on the side surfaces for strengthening or repair existing RC beamsis proposed to investigate the first crack strength and the cracking characteristics of RC beams. In order to verify the effectiveness of this application, experimental tests on six strengthened beams and one control beamhad been carried out. Experimental results demonstrated that this appears a promising technique both on improving the first crackstrength and on suppressing the crack width.

Abstract: In order to study the stability of Montmorillonite / Octadecyl trimethyl ammonium complexes in engineering application, the influences of the organic modifier dosage, oscillation intensity, oscillation time, temperature, pH, sodium salt concentration, calcium salt concentration on the stability of Montmorillonite / Octadecyl trimethyl ammonium complexes were systematically investigated. Research results show that the stability of Montmorillonite / Octadecyl trimethyl ammonium complexes slightly reduces with the increases of oscillation intensity, oscillation time and temperature, but the impact isn’t obvious. The more the organic modifier dosage is, the more unstable the Montmorillonite / Octadecyl trimethyl ammonium complexes are. The stability of the Montmorillonite / Octadecyl trimethyl ammonium complexes decreases significantly under the medium conditions of lower or higher pH. The higher the concentration of sodium salts is, the more stable the Montmorillonite / Octadecyl trimethyl ammonium complexes are, but calcium salts are on the contrary.

Abstract: In this study, the intercalated hydrotalcite (HT)/epoxy (EP) nanocomposites containing red phosphorous (RP) (HT-RP/EP) were prepared by in-situ polymerization. Firstly, low-molecular-weight polyamide 6 (PA6)/HT nanocomposite was prepared in the presence of organ-hydrotalcite with alanine as an initiator at 150°C. And then, PA6/HT composite and a certain amount of RP incorporated into epoxy resin in the presence of curing agent (polyamide 650) and HT-RP/EP nanocomposite was prepared successfully. Finally, the micro-structure and flame resistance were characterized by scan electron microscope (SEM) and vertical burning method, respectively. The results showed that HT was dispersed in the epoxy matrix evenly. HT-RP/EP nanocomposites showed significant flame resistance. When the content of both of HT and RP was 5%, the flame resistance achieved FV-0 level.

Abstract: Different grain size of starting powder was choosed and different sintering additives were used to fabricate Si3N4 ceramics by pressureless sintering. Samples’ relative density and mechanical properties including Vickers hardness, bending strength and fracture toughness were tested. Then XRD, SEM and EDS were carried out to identify phase and observe microstructure and fracture morphology. The result shows that high purity α phase Si3N4 powder of 5 μm is suitable for sintering and combination of 5 wt.% MgO +5 wt.% Y2O3 is most effective within six kinds of sintering aids.