Advanced Materials Research Vols. 476-478

Abstract: The tensile properties of polyetheretherketone (PEEK) composites, which were reinforced with short fibers, such as short carbon fiber (SCF), short glass fiber (SGF), or filled with polytetrafluoroethylene (PTEF), expanded graphite and nano material TiO2 were examined and studied. The weight content of short fibers, PTFE and expanded graphite was varied from 0-15%, and of TiO2 was varied from 0-8%. The results showed, with increasing of the weight content of short fibers, the tensile performance (tensile strength and modulus) of PEEK composites was increased rapidly. If the weight percent of short fibers was more than 10%, this increasing tendency became slowly. With the increasing of PTFE content, the tensile strength was increased at first and then decreased rapidly. However, the tensile modulus kept constant during the change of PTFE content. The influence of expanded graphite and nano particles TiO2 on mechanical properties of PEEK composites was also be studied here. Meanwhile, the reasons of different influence of these fillers were analyzed during microstructure changes of PEEK composites with SEM photographs.

Abstract: How to design the interface is a fundamental issue for the composite materials. Although a little work was concerned with the mechanical design of the interface, the effect of the initial thermal stresses has not been taken into account in those studies. While the thermal stresses due to the manufacturing process and the difference in coefficient of thermal expansion between matrix and reinforcing phase, do play an important role in the properties of the composites. In terms of a concept of the neutral inclusions that do not disturb the prescribed uniform stress field in the surrounding elastic body, the interface parameters are studied with consideration of the effect of an initial thermal stress field in this paper, indicating that the effect of thermal stresses may be eliminated by the design of interface parameters.

Abstract: An element powder-Al plate sandwich rolling processing is proposed for preparation of aluminum alloy foam sandwich with a metallurgy bonding interface. By comparing the deformation characteristic and it’s effect on foaming processing by using Al, Si elements and AlSi alloy powder, and to explore the effect of different powder as raw material on preparing foam aluminum sandwich. It was found that the densification of precursor using element powder is higher than using alloy powder, and rolling deformation resistance is smaller. And it was more suitable to manufacture different types of foam core material by using element powder as raw material.

Abstract: By establishing an option contract model under disruptions in chronological order, we analysis the optimum decision variables and application of option contract to manage the changes in the supply chain benefits which result from the changes of market demand distribution under disruptions, and get optimal strategies. The conclusion is the option contract to supply chain members to achieve shared interests and risks, effective response the changes in market demand with B2B E-markets under disruptions. Finally the conclusion is verified by numerical example.

Abstract: Al2O3/Al-4%Cu alloy composites were manufactured by squeeze casting. Segregation at the interface between fiber and matrix in the composites was researched. The results indicated that at the end of solidification of the composites, the change of the solute in the surplus liquid phase resulted in the type of matrix alloy being changed because of the selecting crystallization, and the segregation at the interface was finally formed. There might be the dual effect of the segregation on structures and property of the composites.

Abstract: In this paper, we present an advanced way to control the DC/DC converter by using predictive control. As the current state of the circuit must be known while using the predictive control, state observer is applied to solve the problem that some variables of DC/DC converter can not be observed. Neural network optimization is used to solve the QP problems in single sample step of predictive control. Simulation results show that this approach can utilize fast converge property of neural network and the new control strategy turns out to be very efficiency.

Abstract: Using the Wilson equation and an extended Miedema model, the thermodynamic effect of silver on the stability of reinforced particles in the Al and Al-Cu matrix were evaluated. The formation of Al₃Ti, AlB₂, and TiB₂ phases are promoted with the addition of silver atoms in Al matrix. Minimum values of excess free energy of reinforced particles were found in the Al-Cu-Ti-B-Ag system. Evidently, Low content of silver atoms actually has the profound effect in promoting the reinforced particles in Al-Cu matrix.

Abstract: Nano-sized Al2O3/polyimide composite films based on Pyromellitic dianhydride(PMDA) and 4,4’-Oxydianiline(ODA) were synthesized by addition with different contents of nano-sized Al2O3 via in situ polymerization. Before addition, nano-Al2O3 particles were firstly modified by coupling agent DB550. The morphology, structure and properties including the mechanical and electrical properties were investigated. SEM microstructures analysis result indicated that the inorganic particles were homogenously dispersed in the polyimide matrix by means of the ultrasonic-mechanical method and the treatment of coupling agent DB550. XRD analysis showed that the addition of nano Al2O3 particles destroyed the molecular order of the PI matrix. Moreover, with the increased in Al2O3 content, the weaken effect on the molecular order also increased. The mechanical property decreased with the increase of Al2O3 content. Better electric breakdown strength could be achieved if the pure polyimide films were incorporated with nano-Al2O3 particles.

Abstract: In this paper, WC particles and NH4HCO3 powders were mixed evenly, and then pressed under 150MPa. The WC porous preforms were obtained after the compacts being heat treated to eliminate NH4HCO3. The volume ratios of WC in the preforms were 30%, 40% and 50% respectively. WC/Fe composites were fabricated by infiltrating liquid cast iron into the WC porous preforms. Optic microscope and scanning electron microscope were employed to observe the microstructure of the matrix alloy and the composites. The results showed that matrix alloy without WC addition had pores in the surface. The microstructure of the composites with WC volume fractions of 30%, and 40% were denser than that of 50%. Hardness and wet sliding wear behaviors of the composites were investigated at room temperature. The addition of WC particles could effectively improve the hardness and the wear resistance of the composites. The influence of volume fractions on hardness of the composites was similar to that on wear resistance. The hardness and the wear resistance of the 40vol.%WC/Fe composite was better than those of the 30vol.%WC/Fe composite. And the properties of the 50vol.%WC/Fe composite were the worst.

Abstract: Made a harmonic response analysis of cast iron bed and precision grinding machine bed made by artificial granitic composite, Compared the amplitude of the guide rail made by the two materials, According to results of the comparison, Optimized the bed of precision grinding machine bed made by artificial granitic composite. The cast iron bed with the optimal results were compared again. The results show that, Under the same conditions, After optimization of the bed rail, the harmonic response amplitude can be reduced about one order of magnitude.