Advanced Materials Research Vols. 690-693

Abstract: Through the analysis and research on images of microstructure of the copper matrix composites, we calculated the fractal dimension of images of microstructure on cross section and parallel pressed power side under different experimental conditions. Meanwhile analyzed some statistics characteristics of fractal dimension. The results show that fractal dimension of graphite reflects the distribution, the dimension is more larger, the organization chart is more complex, the distribution of graphite is more irregular, so the irregular distribution of free graphite can be described by fractal dimension, fractal dimension can be used as a material characterization parameters of organizational form. Through analyses we can get that the fractal dimension of the materials on cross section and parallel pressed power side combining to normal distribution, and it changed with graphite content doesnt affect each other.

Abstract: This paper presents a theoretical study of the dynamic characteristics of rotating composite cantilever beams. Considering shear deformation and cross section warping, the equations of motion of the rotating cantilever beams are derived using Hamilton’s principle. The Galerkin’s method is used in order to analysis the free vibration behaviors of the model. Comparison of the theoretical solutions has been made with the results obtained from the finite element method, which prove the validity of the model presented in this paper. Natural frequencies are obtained for circular tubular composite beams. The effects of fiber orientation, rotating speed and structure parameters on modal frequencies are investigated.

Abstract: The parameterizationmodeling of typical composite flexible pipe is studied by ANSYS two-developmentlanguage APDL, which established the model building of the spiral self-lockinglayer and scanning division meshes. The stress response of the typicalfive-layer composite flexible pipe was calculated under bending load byadopting the no slip assumptions. It is easy to modify the parameters offlexible pipe structure by using the parameterization modeling. Theparameterization modeling can be used for the optimal design of flexible pipe.

Abstract: The influence of temperature on the dry sliding wear behavior of as-cast SiCp/A356 composite under 150r/min, 6N and 30 min has been illustrated in this paper. The results reveal that the wear rate is very sensitive to the change of temperature and it exhibits lower wear rate at the range from 100°C to 200°C. However, the wear rate increases linearly due to adhesive wear operating a long duration at 250°C. The friction stability decreases sharply with the temperature raising. Formation of continuous grooves and some damaged regions are presented on the worn surfaces of the samples at lower and intermediate temperature. Parallel lips (wave like material flow) along the sliding direction are observed at higher temperature of the sample. The wear mechanisms involve an initial oxidative wear regime and spalling wear regime for a long duration and followed by an adhesive wear regime as the temperature raising.

Abstract: In order to investigate the influence of carbon fiber’s surface state on the mechanical properties and the fiber-matrix interaction of CFRP, the change of surface state was achieved by thermal treatment of carbon fibers at elevated temperatures, and the surface state was characterized by XPS. The mechanical properties were measured from the flexural test. The CFRP reinforced with 600 °C treated fabrics containing the highest reactive functional groups, showed the highest flexural strength and modulus. But in the case of CFRP reinforced with 1500 °C treated fabrics containing the lowest reactive functional groups, exhibited the lowest flexural strength and modulus. Combining the mechanical properties with the microstructure analysis, the results indicated that the fiber-matrix interaction (strong or weak) depends on the relative percentage of reactive functional groups present on the carbon fiber surface.

Abstract: Cu-11Cr alloy was prepared by casting and processed into an in situ composite by cold deformation and heat treatment. The microstructure, strength and conductivity were investigated by scanning electronic microscope, tensile-testing machine and micro-ohmmeter. The results suggested that the initially randomly distributed Cr dendrites in the as-cast Cu-11Cr alloy were transformed into Cr fibres aligned parallel to the drawing axis in the deformation-processed in situ composite; the tensile strength and the resistivity increased with increasing cold deformation strain. The good combination of strength and conductivity of the deformation-processed Cu-11Cr in situ composite was achieved by using the proper cold deformation and heat treatment. At η = 8, the tensile strength and conductivity reached 823 MPa and 71.9 %IACS, respectively.

Abstract: SHS (Self-propagating High-temperature Synthesis) process is a new method to synthesis materials. The preparation of high temperature and resisting material with Al-CrO3 system was shown in this paper. According to the orthogonal test, a best sample was obtained with high refractoriness reaching 1800 °C and cold crushing strength 20MPa. The SEM analysis was used to analyze the microstructure of the product. The XRD was used to make sure the components of the product. The product has the characteristics of heat insulation, heat insulation and crush resistance, etc.

Abstract: On the condition of some milling depth and feed rate, By means of high-speed milling force measurement of SiCp/Al matrix composite, the rule for impact of milling speed on milling force is revealed successfully. In some range of milling speed, when SiCp/Al is high-speed milled, the milling force is lowered with increase of milling speed. Furthermore, the experiment also show that the optimal milling speed should be adjusted between 200 and 260 m/min for the SiCp/Al matrix composite with 56% volume fraction and particle size of 60μm.

Abstract: MgFe_2O4/MgO composite films have been successfully fabricated by a facile route using magnesium iron layered double hydroxide (MgFe-LDH) as a single-source precursor. This strategy mainly involves the formation of MgFe-LDH film by casting the slurry of MgFe-LDH precursor on the α-Al₂O₃ substrate, followed by calcination at 900°C. The structure, morphology and magnetic properties of the resulting films were characterized by means of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), laser particle size analysis, scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and vibrating sample magnetometer (VSM). The results show that the composite films are composed of spherical or elliptical grains with diameters of less than 150nm and their thickness range was 2~3 μm. EDX mapping analysis reveals that the composite films have uniform distribution of MgFe₂O₄ particles in MgO matrix. Further investigation indicates that the magnetic properties of the composite films can be tailored by altering the Mg/Fe molar ratio of LDH precursors.

Abstract: Hydrotalcite-like compounds are a class of anionic lays or layed double hydroxiods (LDHs) which consists of alkalescence, anion-exchanges and memory effect. The synthetic methods of LDHs include coprecipitation, hydrothermal synthesis, mirowave radiation, ion exchange, sol-gel method, roasting reduction method, instant synthesis, etc.The molar ratio of raw materials, pH value,reaction temperature,reaction time and so on have a greater impact on the purity and crystallinity of the LDHs.