Abstract: Titanium carbide particulate reinforced composites were fabricated by vibrational moulding sand casting technique. Titanium carbide particulate added as a reinforcement phase in the LM6 alloy matrix and the percentage of addition varied from 0.2, 0.6, 1 and 2% on weight fraction basis. The thermal conductivity and diffusivity of TiC composites were determined. Increasing frequency of vibration and TiC content helps to improve density, thermal conductivity, thermal diffusivity and purification of the grain boundaries. The dispersed particles increased the thermal conductivity and diffusivity according to an effective media theory.
Abstract: Carbon aerogels were modified by ammonia solution assisted by microwave radiation in order to obtain materials with good dispersion stability in water and satisfactory electrical conductivity simultaneously. Several techniques were used to characterize the materials including FTIR, Raman spectroscopy, Zeta potential, Four-Point Probe and nitrogen adsorption. The results revealed that the dispersion stability of carbon aerogels in water got better and electrical conductivity of carbon aerogels increased at first and then decreased with the increase of microwave heating time, which were closely associated with oxygen surface groups and degree of graphitization and pore structure. As a good template, the modified carbon aerogels with good dispersion stability and electrical conductivity were used to synthesize LiFePO4 composites, and the improved electrochemical properties of these composites were characterized by means of Four-Point Probe and galvanostatic charging/discharging.
Abstract: This work evaluated a new ultra-light photovoltaic embedded structure for solar-powered aircrafts, in which the mono-crystalline silicon (m-Si) solar cells encapsulated by epoxy were adhesively bonded to the upper wing skin made of rigid polyurethane foam (RPUF). To evaluate the effect on the cell encapsulation, static tests were carried out. The results showed that the encapsulated cells had better flexibility. The bonded-point and multi-cell models for the embedded structure were analyzed by FEA software. As the number of the bonded points increasing, the stress and deformation of the embedded structure decreased; once exceeded 16 points, the stress and deformation changed little. The deformation of the non-reinforced multi-cell model was very large; the stiffness improved greatly after reinforced by the glass fiber ribbons.
Abstract: The composites composed of polyamide66（PA66）, polypropylene（PP）, and magnesium oxysulfate whisker(MOS) were prepared by means of melt blending through co-rotation twin screw extruder. The standard samples were prepared by injection machine. The effect of coupling agents on the whisker surface, and the influence of MOS content on mechanical properties, heat properties, flame-retardant properties and the microstructure of the composites were investigated by scanning electron microscopy(SEM), thermogravimetry(TG) and differential scanning calorimetry(DSC) techniques, respectively. The results showed that the MOS whisker modified with coupling agents KH570 possesses better activation exponential and dispersity, and the tensile strength, flexural strength and toughness of PA66/PP/MOS composite were firstly increased and then decreased with the MOS content increasing, the optimum adding amount of MOS was 25phr. The flame retardant property was improved remarkable by adding of MOS.
Abstract: Combined SHS with casting, in-situ Al2O3 particle-reinforced copper matrix composite was fabricated. The effects of the load and Al2O3 particle on the friction coefficient and wear volume were investigated. And the wear resistance of composite was compared with that of pure copper. The results show that with the increase of load, the coefficient of the copper increases, while it decreases slightly as to composite. The wear volume of the composite is always lower than that of copper. The highest relative wear ability is 4.5, which indicates a better wear resistance..
Abstract: The genetic algorithm and the adaptive mechanism are adopted to tackle the inefficiency of optimization and the convergence difficulty of collaborative optimization (CO). Based on the further analysis of collaborative optimization process, the constraint conditions are converged into part of the optimization function. The system optimization model of CO has been reconstructed according to the adaptive penalty function which is based on the information of different disciplines and the transformation of system-level constraints. Therefore, the global and local search capabilities of optimization algorithm and searching efficiency of CO have been improved. Meanwhile, the difficulty of convergence caused by the internal definition of CO has been resolved. Finally, an example of speed reducer is demonstrated to verify the proposed method, showing that the convergence rate and search efficiency have been improved.
Abstract: composite laminates, metal ion implantation, low-velocity impact damage, BVID Abstract. Metal ion implantation was carried out on composite laminates to modify the surface properties, so that after low-velocity impact barely visible impact damage (BVID) was easy to realize. Surface topography of laminates was observed by SEM. Microhardness and drop-weight impact was tested on composite laminates. The results showed that after metal ion implantation microhardness of laminates increased obviously and resin was easy to generate plastic deforming. Dent depth had been improved so as to realize visible impact damage more easily. And compression-after-impact (CAI) had not decreased. Comparison with Ti ion implantation, Cu ion implantation had better influence on realizing visible impact damage (VID).
Abstract: Ti-6Al-2.5Sn-4Zr-0.7Mo-0.3Si-0.3Y alloy matrix composite reinforced with 7%vol TiB whiskers was fabricated by Induction Skull Melting (ISM) technique and one-direction forged technology utilizing the reaction between titanium and TiB2. The microstructure, room temperature and high temperature mechanical properties have been presented and discussed. Microstructural analysis of the composites revealed that the microstructure was significantly refined and TiB whiskers were made to align the longitudinal direction after forging. It shows that the tensile strength and ductility of the composites has a significant improvement, especially at room temperature.
Abstract: Two kinds of gradient composites, whose compositions were Al-20%Mg2Si-5%Si (sample-1) and Al-14.9%Mg2Si-10.3%Si-11.8% MgAl2O4 (sample-2), were fabricated based on the electromagnetic separation under the high frequency magnetic field. The microcosmic structures of two composites were analyzed and the effect of the addition of SiO2 on the microcosmic structure and the mechanical property were discussed. It is found that the particles MgAl2O4 accumulated in periphery of specimen of sample-2, which come from the diffusion reaction between SiO2 and aluminum and magnesium in the melt and was proved by the result of X-ray analysis. Besides the MgAl2O4, the primary phases of Mg2Si, Si also emerged in periphery of specimens. At last, the hardness was given along the radial direction. The result shows that the hardness of the two materials exhibit graded distribution in radial direction and the hardness of sample-2 is higher than that of sample-1 due to the formation of MgAl2O4 particles. Both the two materials meet the requirements of gradient composite material whose outer area is in high intensity and center area is in flexile.