Abstract:Preparation technology of zirconium diboride powders, such as solid method, liquid method, gas method and so on, is reviewed in detail. The characteristics of a variety of the preparation routes are detailedly analyzed, and the further trend of preparation technology of zirconium diboride powders is forecasted.

Abstract:Firstly, biaxial strength theories of fiber reinforced composite materials are briefly reviewed. The failure criteria proposed to predict composite failure can be divided into two main groups according whether to distinguishing failure modes or not. Merits and defects of different failure criteria are discussed and analyzed. Secondly, the development of biaxial testing equipments for the composites is summarized in a nutshell. Different types of specimen for biaxial loading with their characteristic problems are shown adequately. Finally, a concise assessment of biaxial strength of fiber reinforced composite materials is provided, and the future development trend is also predicted.

Abstract:Through the mathematical modeling of the variable-stiffness tow path, the topological structure of the variable-stiffness laminate is modeled. The fiber-angle and the layer-thickness of each lamina on each discrete unit can be designed independently. Then the topological structure is translated into GENESIS, in which the internal structure of the laminate is visualized, and the tensile properties of each lamina are analyzed. By comparing of the simulated results and the experimental data, the accuracy of the variable stiffness laminate tensile model is 95%. This method visibly reveals the location of the overlapped units, the distribution of the thickness and the distribution of fiber angle on each ply. It also accurately simulates the tensile properties of the laminate within the plastic range.

Abstract:Mechanical property of ellipsoid pressure vessels with unequal polar openings is studied in this paper. The steady formulas for filament on a surface of revolution are derived from differential geometry. Based on the membrane theory, laminate theory and Tsai-Wu failure criterion, the thickness of the equator is 1. 281 7 mm, the stress value of the fiber direction is less than the fiber strength 3. 92 GPa. The stress state of the filament wound ellipsoidal vessel is that the damage happens first in equator, and local failure phenomenon is happened. To minimum winding layers weight M as the objective function, Tsai-Wu failure criterion as the constraint condition, under the condition of 5 MPa internal pressure, we achieve the optimized weight is 34. 072 kg. Compared to ellipsoid pressure vessels with equal polar openings, it has highly non-linear, instability and high precision.

Abstract:Based on electrolytic principle and the kinematics analysis for single abrasive grit with ultrasonic vibration, the mathematical model of grinding force for ultrasonic ELID composite grinding is proposed. The analysis and simulation are conducted to the model. The analysis of the model shows that:ultrasonic vibration changes the motion trajectory of the abrasive grains, and the undeformed chip thickness is reduced under the same conditions. The inprocess dressing of grinding wheel maintains the abrasive grits in the fengrui state, but also affects the actual depth of cut of the grinding wheel. All that will impact on the grinding force. The grinding force decreases with the increase of ultrasonic vibration frequency and amplitude, the electrolysis voltage, the pulse ratio, the electrolyte resistivity, and increases as the depth of cut, the workpiece speed increases.

Abstract:The Ex-situ elasticizer polyethersulphone(PES) was adhered homogeneously on carbon fabric according to Ex-situ toughened technology. Carbon fiber reinforced BMI composites U3160/6421 was prepared by RTM process. The effect of PES on the properties of U3160/6421 composites was investigated through low-velocity, DMA, SEM and mechanical properties tests. The results showed that composites prepared by ES-Fabrics adhering PES had a good toughening effect. The CAI value of U3160/6421 composites toughened by PES increased by 85%. Because of the added PES, the phase version of PES and BMI6421 resin appeared in the interplay of composites. This structure improved the damage resistance and damage tolerance of composites, and Ex-situ interlaminar-toughening had a little impact on mechanical properties.

Abstract:The kinetic parameters of polytriazole resin were determined and the kinetic model was built. Results revealed that the cure of the resin fits well with the autocatalytic model at the prior stage of the curing, while with the n-order model at the latter stage. Finally, the curing processing of polytriazole resin is studied.

Abstract:A new catalyst (POSS) was used to lower the curing temperature of Cyanate ester (CE). The prepreg was prepared by hot-melt method. And the characters of CE are investigated. The results show that the modified CE composite has lower curing temperature, good storage and mechanical properties.

Abstract:A series of epoxy resin matrix for shape memory composites were prepared by introducing an epoxy containing flexible chains into a aliphatic amine cured bi-phenol a type epoxy resin. The shape memory properties, processing properties and mechanical properties of the resin were studied. Both the shape retention rate and the shape recovery rate of the resin are above 98%. Rheological tests show that the resin is suitable for liquid composite molding. The tensile strength and flexural strength of a cured shape memory resin are comparable with commercial epoxy resins for structural use. The impact strength of the cured resins are all above 89 kJ/ m2 at room temperature and above 30 kJ/ m2 at -80℃.

Abstract:Cf/ ZrB2 -SiC composites were prepared using precursor in filtration and pyrolysis(PIP) technology. The thermal conductivity, coefficient of thermal expansion( CTE) and thermal shock resistance were investigated. SEM and XRD were used to analysis microstructure and phase. The result show that the composites exhibits excellent thermal shock resistance from 1 700℃ to RT. The change of thermal shock resistance is discussed.

Abstract:2196-T8511 Al-Li alloy extrusions. Each material involved four kinds of cross-section extrusions. The true stress-strain curves and mechanical properties of different cross-sections, the different sidewall and different thickness were determined. Irregular tear zone and dimples are distributed everywhere by observing the fracture surface of Al-Li alloy. Dimples in 2196-T8511 are smaller and shallower than the 2099-T83 Al-Li alloy, indicating that the plasticity of 2099-T83 Al-Li alloy is better, which is consistent with the mechanical properties.

Abstract:PA/ VMPET/ Al/ PE film of vaccum insulation panel is a kind of multilayer laminate envelope, which is one of the most candidates evelope materials. In this paper, the effect of heat-sealing temperature, heat-sealing time and heat-sealing pressure on the heat-sealing strength were investigated. Simultaneously, the process parameters of heat-sealing film was optimized using m-atlab software. Thermal analysis of PA/ VMPET/ Al/ PE was carried out by using differential scanning calorimeter etry (DSC). The results showed that the effect of heat-sealing temperature on heat-sealing strength was the most significant in the three parameters. The heat-sealing strength presented good at heat sealing temperature, heat sealing time and heat sealing pressure of 160 to 170℃, 1. 0 to 2. 0 s, 0. 2 to 0. 4 MPa, respectively. The optimal process parameters were simulated by Matlab software, heat-sealing temperature, heat-sealing time and heat-sealing pressure were 167℃, 1. 80 s and 0. 34 MPa, respectively. The result shows that the optimal process parameters were consistent with experimental values.

Abstract:Under simulated conditions hot hydraulic liquid accelerated aging testing of nitrile-butadiene rubber seal was carried out. By the FT – IR,DSC,TGA and scanning electron microscopy methods; the variation of chemical structure, thermal property and fracture morphography of rubber seal was analyzed in hydraulic fluids. The results show that after aging testing, the compression property of the rubber seal decreased gredually, both thermal decomposition temperature and glass transition temperatures increase. On the one hand, under the effect of stress, molecular chain segments have been orientated in some directions, restricting the relaxation of molecular chains, which resulted in the compression property decreased and the thermal property increased. On the other hand, the tensile fracture surface tends to be smooth and have holes, and the content of additive decreases, which means embrittlement has occurred to rubber seal and there have been mass exchange between rubber seal and hydraulic fluid, this is the other factors of compression property decreased.

Abstract:The visible difference of stitch-bonding process between China-made carbon fiber and TORAY carbon fiber has been made clear by way of fabricating its stitching fabric. Some parameters and measure methods has been chose to analysis quantitatively the influence on the hairness index of carbon fiber, including carbon fiber, yarn-guiding material, yarn-guiding structure and yarn-delivering mode. The results shows that hairness of carbon fiber is pivotal to stitch-bonding process. The paper attempts to give some references to evaluate and analysis quantitatively difference of carbon fiber stitch-bonding process, and to modify china-made carbon fiber.

Abstract:Three typical acoustic emission signals for carbon fiber epoxy laminate in tensile damage are investigated by approximate entropy theory. The computed results show matrix cracking, debonding and fiber breaking own some different characteristics of approximate entropy spectrum which is construed by empirical mode decomposition (EMD) method. In addition, spectral distribution of intrinsic mode functions for the three kinds of acoustic emission signals is analyzed which further illustrate approximate entropy in essence is measuring the probability of new vibration mode in signal, and demonstrate the effectiveness of using approximate entropy spectrum analysis in acoustic emission detection for composite material.

Abstract:Conductivity of insulating materials is a key parameter to determine how accumulated charge will distribute across the spacecraft and how rapidly charge imbalance will dissipate. However, methods are often not applicable to situations encountered in spacecraft charging, conductivity is more appropriately measured for spacecraft charging applications as the decay of charge deposited on the surface of an insulator. These parameters determined from classical methods were used in design techniques to mitigating spacecraft charging effects may produce remarkable error. In this paper instrumentation for both classical and charge storage decay methods has been developed. Experiments were conducted by both methods on R4 Printed Circuit Board. The experiments are similar to results from Jet Propulsion Laboratory and Utah State University.

Abstract:In this study, in order to explore the ability and experimental parameters to detect the internal defects of radar absorbing coating using the lock-in thermography technology, the method, which combined the finite element (FE) simulation and experimental research, is used to study for the square and circular simulated defects testing of the coating specimens. The analysis results show that the finite element simulation provides theoretical support for experiment and the defect of the equivalent area which is 3 mm×3 mm can be detected when the range of modulation frequency is 5 to 10 mHz. In addition,the phases of defects are lagged compared to defects cerea, and phase delay get bigger with the area of the defects increasing.

Abstract:In order to get radiographic equivalent factor for different materials under different transillumination voltage, the essay used two testing methods of simultaneous transillumination and exposure curve graphic in the environment of 50 kV transillumination voltage,using titanium as standard material. Through the analysis of the steps and problems of simultaneous transillumination method, the essay took in two means of ladder extension and thickness verification as the settlement of the problem. Though the analysis of exposure curve graphic method, the essay affirmed the rules on choosing exposure curve and blackness, explained the relationship between the exposure curve and graphic method. Combined with mathematical tools,the essay obtain the conclusion that the equivalent factor is associated with transillumination voltage, but will not change with the exposure quantity.