Advanced Materials Research Vols. 194-196

Abstract: Reinforced phenol formaldehyde resin (PF) matrix nanocomposites with different nano-SiO₂ were fabricated with two-roll compounding and compression molding technology. The mechanical and tribological behaviors of the reinforced composites were studied. The friction and wear experiments were tested on a constant speed machine (D-SM). The impact and flexural strength of nanocomposites were increased by the addition of various types of SiO₂, but the flexural modulus was decreased. The effects of the addition of various types of SiO₂ on tribological properties of the composites were explored in this study. The results showed that the coefficient of friction of the composites increased, while the wear rate values decreased at various temperatures. Microstructure of worn surface of the tested composites was observed by scanning electronic microscope (SEM) and the wear mechanism of the reinforced composites was studied.

Abstract: In this paper, A 3-D numerical model of a circular tube is established, which is made of carbon fiber composite materials whose inner diameter is 43mm and outer diameter is 45mm. The behaviour of axial compression and bending load cases are analyzed under the theory of mechanics of materials and theory of classical laminate plate. Results of axial compressive stiffness and bending stiffness agree well with the experimental data,showing that the FEM simulation used in this paper is an efficient and reliable tool to calculate and predict the behaviour of carbon fiber tube.

Abstract: In order to clear the influence of carbon fiber reinforced polymer (CFRP) on the bearing capacity of reinforced concrete beams, tests of three reinforced concrete beams strengthened with CFRP are carried out. Experimental result shows that CFRP can effectively increase bearing capacity of flexural member, and can restrain the development of crack. Cracking load, yield load and ultimate load are significantly increased. At the same time numerical simulation is done; it is good agreement with experimental results.

Abstract: TiC-Mo-Ni and TiC-WC-Mo-Ni cermet blocks have been obtained in situ by reactive hot pressing sintering. The phase structure and microstructure of the two cermets were compared to investigate the effect of the addition of WC. The results show that the chemical reactions between Ti, Mo and C in TiC-Mo-Ni system are relatively complete. However, there is a small amount of unreacted C powder in TiC-WC-Mo-Ni system, which is associated with the reaction between Ti and WC. The in-situ carbide grains are very fine with the size range of 0.5-2µm. The boundary morphology between the carbide grains and the binder phase changes from an angular shape to an almost rounded shape with the addition of WC.

Abstract: Two composites of 2D C/SiC-C and 2D C/SiC were fabricated by isothermal-isobaric chemical vapor infiltration (ICVI). The microstructures and mechanical behaviors at room temperature were characterized and investigated, respectively. In the 2D C/SiC-C composite, the PyC matrix layers are homogeneous and continuous. Moreover, the matrix layers of SiC and PyC bond well and almost no microcracks are found in the multilayered matrix. Compared with the 2D C/SiC composite, the 2D C/SiC-C composite exihibits improved mechanical properties.The successive extraction of matrix layers and multiple deflections of cracks in the SiC/PyC multilayered matrix contribute to the improvement of mechanical properties.

Abstract: Elastic wave scattering of single spherical particle and the multiple scattering in particle-reinforced composite with imperfect interfaces are studied by the use of wave function expansion method. Four typical interfaces are obtained by appropriate selection of spring constants in the classical spring interface model, i.e. perfect interface, slide interface, rough interface and unbonded interface. The jump and continuous conditions of displacement vector and traction vector are used to derive the equation which the unknown expansion coefficients of the scattered wave field satisfy. Furthermore, the multiple scattering in composite reinforced by random distributed spherical particles is investigated. The effective velocity and attenuation of coherent waves and the dynamic effective moduli of composites are evaluated. The numerical simulation is performed for the SiC-Al composite. The influences of interface parameters on the scattering cross section, the effective velocity, the effective attenuation and the effective elastic moduli are discussed.

Abstract: A kind of centrifugal casting plus in situ techniques of fabricating iron-based composite coating reinforced by tungsten carbide (WC) particles was developed. The experimental results show that the reinforcing particles were generated by reaction between dissolved tungten wires and carbon from gray cast iron molten. The composite coating mainly consists of primary WC carbides, some fine secondly WC carbides as the reinforcing phase and pearlite accompanied by negligible graphite flakes as the matrix. Compared with the unreinforced gray cast iron, the in situ synthesized WC particles can enhance the ultimate tensile strength and decrease elongation rate of the composite coating. Fracture morphology reveals that fracture mode of composite coating is brittle and ductile mixed fractures, the fracture mechanism of the composite is not only related with the introduction of reinforcement but also with the reduction of graphite flakes in the matrix

Abstract: A surface TiO₂-supported of silica composite material was prepared by surface organometallic chemistry method and the structure was characterized by FTIR, EDAX and XRD. The results show the bonding interaction between TiO₂ and SiO₂, linking by Si-O-Ti bond. Furthermore, the anatase phase crystal structure is observed by XRD analysis.

Abstract: Wood-polymer composite was prepared by a novel combined two-step method with maleic anhydride (MAN) for the first treatment, and mixed monomers of glycidyl methacrylate (GMA)/ methyl methacrylate (MMA) (1:5 of molar ratio) for the second treatment. SEM and FTIR technologies were employed to characterize the interfacial compatibility between resultant polymer and wood matrix, and the dimensional stability of the resultant wood-polymer composite was also tested. The results indicated that polymers fully filled up wood cell lumina and chemically bonded to wood cell wall, resulting in the improvement of interfacial compatibility between polymer and wood matrix without obvious lacunae. The dimensional stability of poplar wood was significantly improved after the combined two-step treatment, and became more stable than that of PEG-1000 treated Poplar Wood.

Abstract: In this research, the chemical and multilayer hot-press drying was used to modify poplar wood. The timbers were compressed and dried in the multilayer hot-press drying kiln. The combination of chemical modification and hot-press drying can improve the mechanical properties. The influence of chemical and hot-press drying on the compressive strength parallel to grain, the bending strength, the density, the water absorbent and the crystallinity of poplar wood have been investigated in this study. The chemical treated conditions close to real technological regimes selected. The samples were impregnated with three conditions. The samples were dried in a hot-press drying kiln for 130hrs. It was showed that the urea carbamate and hot-press drying treatment increase the properties. The density and mechanical properties increased with increasing urea carbamate, while the water absorption decreased. The crystallinity is 37.03%, 37.11%, 37.78%, separately, compared with the natural wood of 35.09%. The TAG showed the thermal stability increased.