Applied Mechanics and Materials Vols. 117-119

Abstract: The preform of Al2O3 fiber was obtained by wet method,and the result shows that the fiber distribution of preform is more uniform after the pretreatment, and the length - diameter ratio can fully meet the demand of qualified preform. The surface of preform prepared by this process is flat, and fiber is distributed evenly, with certain strength,so it can be used for pressure infiltration fabrication of alumina fiber reinforced metal matrix composites.

Abstract: The interfacial reinforcement with interlaminar chopped fibers of piezoelectric composite under impact electro-mechanical load was studied using nonlinear finite element method. A meso- mechanical model based on the main toughness reinforcement mechanism of single fiber bridging and pull out was adopted, and then a tri-linear bridging law was obtained, while the interface chopped fibers by defining nonlinear bidirectional spring elements between coincident nodes on the two crack surfaces within bridging zone and the energy release rate was calculated using the virtual crack closure technique. The numerical investigation indicates that the interlaminar chopped fiber can effectively reduce the crack tip energy release rate whether the applied voltage is positive or negative, which was an effective technique improve the interfacial toughness of the piezoelectric composite adhesive structure.

Abstract: With the features of high efficiency, low consumption and good mechanical characteristic, thin-walled composite box beams have been broadly adopted in structural engineering, and its mechanical behavior has became an active research area. As shear lag effect can bring an uneven normal stress distribution on the flanges, it would remarkably affect the strength design of thin-walled beams. This paper focuses on the experimental investigations of shear lag effects in [0^o ∕±45^o₂ ∕ 0^o]T laminated box beam under concentrated loads, and test results indicates that the shear lag effect in this composite box beam can be simulated by the two parabola.

Abstract: This paper dealt with how the aging time and temperature affected the hardness of beryllium bronze layer in the explosive welded beryllium-bronze/carbon-steel composite plate. The properties of shearing, bonding, cold bending and microhardness were studied in term of the composite plate, including the aging and nonaging. The optimum aging treatment process of the composite plate is aging temperature at 320°C for 3 hours. And the results show that: aging treatment has no obvious effects on the shear strength but sharply decreases bond strength of the composite plate. And aging treatment to a certain extent reduce the cold bending prroperty. After aging treatment, the microhardness value and distribution of carbon steel was no obvious change, and the microhardness of beryllium bronze sharply raised and smoothly distributed.

Abstract: The ablation properties of C/C-ZrC-SiC composites prepared by precursor infiltration and pyrolysis processes were studied by the H₂-O₂ ablation method. The results indicate that the C/C composite of 1.28 g•cm^-3 was densified to C/C-ZrC-SiC composite of 1.42 g•cm^-3 after infiltration and pyrolysis once, the density increased 10.94%. The linear ablation rate and mass ablation rate of the C/C-ZrC-SiC composites (ρ=1.42g•cm^-3) were 7.22μm•s^-1and 3.88mg•s^-1, which decreased 79.31% and 65.46% comparing with C/C composite of 1.28 g•cm^-3 respectively. The introduction of ZrC-SiC into the matrix greatly enhanced the anti-oxidative and ablation property of the C/C composite. The ablation mechanisms of the C/C-ZrC-SiC composites were supposed to be the synergistic effects of thermo-chemistry ablation (oxidation and sublimation) and mechanical erosion.

Abstract: Calcium silicate for filling material used in dissolved acetylene cylinders was prepared by adding alum as additive. Samples were characterized by X-ray powder diffraction (XRD) and scanning electron microscope (SEM). The effects of alum on the bleeding, shrinkage, strength, porosity, morphology and phase composition were studied. The experimental results show that the adding of alum can improve the comprehensive performance of samples. The mechanism was discussed in detail.

Abstract: Natural fibers are now becoming a subject of interest to replace synthetic fiber as reinforcement materials where the development of natural fiber composites has been conducted in the last few decades. The objective of this research is to investigate the energy absorption capacity of banana fiber polyester composite and its specific energy absorption capacity as well. Banana fibers are extracted and cut into 10mm, 20mm and 30mm fiber length. Fabrication of rectangular bar as composite samples with different banana fiber length and fiber volume fraction (1%, 2%, and 3%) were conducted and the results are studied and analyzed. The information on energy absorption and specific energy absorption capacity are useful for applications such as automotive structures where the ability to absorb impact may save life. The increase of banana fiber content and length shows an increase of maximum load and energy absorption values for all specimens.

Abstract: Carbon-Carbon composite materials are widely used as the surface thermal protection systems (TPS) of advanced high-speed air-craft and spacecraft. The thin-walled structures with this kind of materials would exhibit large displacement response under high-level acoustic loads and possibly display buckling at elevated temperatures. Reliable experimental data are difficult to acquire because of the high costs and difficulties with instrumentation at high acoustic intensity and elevated temperatures. Thus, in the design process greater emphasis will likely be placed on improved mathematical and computational prediction methods. Among these researches, the simulation methods for nonlinear response of thin-walled composite panels under thermo-acoustic loadings are being developed emphatically .This paper presents a nonlinear finite element model for analyzing nonlinear random dynamic behaviors of Carbon-Carbon composite panels under the combined effects of thermal and random acoustic loads. The acoustic excitation is assumed to be a band-limited Gaussian random noise and uniformly distributed over the structural surface and the thermal load is assumed to be a steady-state with different predefined temperature distribution. Three types of motion: 1) linear random vibration about one of the two buckled positions, 2) snap-through motion between the two buckled positions, and 3) nonlinear random vibration over the two thermally buckled positions can be predicted. And the dynamic response behaviors of the structures are discussed. Based on this, the influences of sound pressure level (SPL) and elevated temperatures on the dynamic responses are analyzed emphatically.

Abstract: Operation principle of high-pressure briquetter is introduced. According to the problems arised from real production in pilot named as comprehensive utilization of vanadium-titanium magnetite, countermeasures have been proposed to solve these problems. At the base of carrying out a series of reformations on the equipments and now the high-pressure briquetter can meet the requirements of industrial production.

Abstract: This document deals with the whole process compression model test on 12 short columns of separation concrete-filled steel tubes (CFST) which are subjected to eccentric compression on the non-separation side. The experimental parameters include the separation ratio and the eccentricity ratio. The results show that the separation ratio and the eccentricity ratio will influence CFST components’ mechanical properties which contain the relationship of load-strain amd load-deformation, that especially embodied in the nonlinear stage. When compressed on non-separation side, the confinement of steel tubes to core concrete will be continuously weakened and the ultimate load capacity of the components will be decreased obviously with both the separation ratio and the eccentricity ratio increasing gradually. But it less serious which compare with that compressed on separation side.