Advanced Materials Research Vols. 311-313

Abstract: Reinforced polyimide composite with of carbon fiber and carbon nanotube were prepared by hot molding technology. The mechanical and friction and wear behaviors of the reinforced composites were studied. Tensile tests showed that SCF and CNT exhibit a beneficial effect for restoring the stiffness of the CF/PI composite. The carbon fiber reinforcement was found effective in reducing the coefficient of friction and the wear rate. This implied that the CNT improves the adhesion between SCF and PI.

Abstract: Carbon fiber reinforced composites have all the ideal properties, leading to their rapid development and successful use for many applications over the last decade. In this paper, short carbon fiber reinforced Polytetrafluoroethylene (SCF/PTFE) composite were prepared with melt blending and hot-pressing techniques. The mechanical properties of this composite were investigated taking into account the combined effect of mean fiber length. Finally it can be shown that an increase in fiber length can enhance the mechanical properties of CF/PTFE composites. The fracture surface of PTFE composite was examined by SEM, to identify the topography of outside force.

Abstract: The microstructure and wear resistance of in-situ Mg₂Si/Al-Si were studied in the different content of Sb. The result shows that when the content of Sb is 0.4%, the refining effect of primary Mg₂Si granules in Mg2Si/Al-Si composite is best. The shape of Mg₂Si turned into fine and even granules compared to the shape of Chinese character or treelike crystal before modification. At the same, the composite shows the best wear resistance and the loss of wear quality was reduced by 19%～37%. The improvement of the wear resistance by alloy elements is related to the modification of the Mg₂Si granules and enhancement of the matrix. The main wear mechanism of in-situ Mg₂Si/Al-Si composite is grain-abrasion.

Abstract: Electrical conductive carbon black-filled cement-based composites are significant as multifunctional structural materials. Double percolation in carbon black-filled cement-based composites involves both carbon black particle percolation and cement paste percolation, which has great effect on the resistivity of composites. Based on double percolation theory, the influences of sand-binder ratio and carbon black volume fraction on the resistivity of carbon black-filled cement-based composites are investigated. The results show that besides carbon black volume fraction, sand-binder ratio is a key factor affecting double percolation behavior in carbon black-filled cement-based composites. At a fixed carbon black content in overall mortar, with increasing sand-binder ratio, the cement paste percolation though aggregate phase increases due to high obstruction of aggregate but the carbon black particle percolation in cement paste decreases. This is because that the microstructure of aggregate is impenetrable so that the carbon black particles are limited in cement paste, that is, the carbon black content in paste is compacted and large amount of conductive paths are generated by lapped adjacent carbon black particles in paste. The double percolation in the electrical conduction in carbon black-filled cement-based composites is observed when the carbon black volume fraction is 7.5% and sand-binder ratio is 1.4, and its resistivity is only 3200 Ωcm, so that a sand-binder ratio of 1.4 and 7.5% carbon black volume fraction or more are recommended for attaining high conductivity with a compromise between workability and conductivity.

Abstract: For industrial applications, many of the damage of textile reinforced flexible composites are due to growth of the defects coming from manufacturing process or generation by static or dynamic load prior to failure. Hence, this work attempt to investigate on tensile behavior and damage initiation mechanisms in woven fabric reinforced flexible composite with single edge notch (SEN) subjected to mono-axial loading. Tensile tests were conducted with a notch depth of 0, 5, 10, 15 and 20mm, respectively. Damage mechanisms have been described and tensile strength, energy absorption was also expressed. Experimental results indicate that the failure progressive in the textile reinforced flexible composite was quite complex and tested material demonstrated significant notch sensitivity.

Abstract: Thermal barrier coatings are used as thermal insulation and thermal protection for high-temperature components of aircraft engines. Service failure of the components is often caused by premature breaking of the coatings. The distributions of residual stress in a ZrO₂/NiCoCrAlY thermal barrier coating during thermal cycling was here simulated using finite element method. Four kinds of models involving planar and curved interfaces between the bond and the ceramic top coat layers were established. The simulated results showed that the high residual stress which is about 100-300MPa is present at the interface between bond layer and ceramic layer. The residual stress in curved interface is larger than that in planar one, and concentrates mainly at the troughs. Structure for planar interface exhibits better than curved interface. The residual stress would increase obviously with the presence of thermally grown oxide layer.

Abstract: Processes of the Liquid Composite Molding (LCM) are widely used in composites produced by impregnation of a dry preform with liquid resin. The resin flow through the preform is usually described by Darcy’s law and the permeability tensor must be obtained for filling process analysis and characterizing the ability of a porous material to be impregnated by a resin fluid. In generally, resin flow in the thickness direction can be neglected for thin parts, but the resin flow in the transverse direction is important for thicker parts. In this study, the transverse permeability measurement device using ultrasound method was developed, the transverse flowfront could be calculated, and global effective permeability and transverse were studied.

Abstract: This article use the Sulphide Isobutene, Five Sulfides Dialkyl, and Star of Phosphorus as the additives, Neopentyl Polyol Ester (NPE) as base oil for screening lubricant formulation. The purpose of this article is screening the lubricant additives formula. Apply the BP neural network method in optimization design. Through the optimization of lubricant additive formula select the best formula for experiment. The selected best formula is Sulphide Isobutene 0.8%(mass percent), Five Sulfides Dialkyl 1.2%(mass percent) , Star of Phosphorus 1.6%(mass percent), relative error is 0.089.After validation experiment，it is conclusion that S-type blends with P-type additive use will acquire good result, and the method of optimal convergence faster, the forecast precision test is satisfied.

Abstract: Ti/Pb-WC-PANI inert electrodes was prepared by pulse electroplating. The effects of process conditions and concentration of solid particles on kinetic parameters of oxygen evolution, appearance of coating and deposition rate was studied and the process of electroplating was optimized. The optimal process conditions were as follows: PANI 30 g/L, WC 40 g/L, pulse on-time 0.5 ms, pulse period 1.5 ms, average current density 2 A•dm^-2, bath temperature 25 °C.

Abstract: In order to compensate the unbalanced moment introduced by POS into an aerial 3-axis ISP system, a balance weight unit is put forward. Based on the structure characteristics of ISP, an initial sample of balance weight unit is first designed. To minimize the mass and maximize the compensating moment meanwhile, the topological optimization on the connecting frame is followed via FEM that leads to the mass reduced as much as 60%. Then, the design optimization on size parameters about whole unit is carried out further until a satisfied structure gotten. The results show that the mass of the optimized structure is decreased more than 5.5% than before under the condition of compensating moment keeping unchanged.