Abstract:The research progress of graphene in the field of anti-atomic-oxygen erosion, solar cells, and space lubrication was reviewed based on describing the microstructure and property of graphene. The application prospect of graphene was discussed for thermoelectric materials, gas sensors, space suit, water treatment of space station, electric storage device, and thermal control materials etc.

Abstract:The theoretical model, design principle and optimization design methods of multilayer structured absorbing material is described in this paper.Characteristics of multilayer structured absorbing material from the electromagnetic properties of absorbing materials point of view, and the multilayer structure design on the performance of the absorbing material is also discussed in detail.The technical difficulties of multilayer absorbing material, and the development trend of the multilayer structure absorbing material are put forward.

Abstract:The 3D braiding composites is widely used in the field of aviation,aerospace and other high technology because of excellent properties. The resistance of 3D braiding composites to high-temperature is an important application. In this paper, the heat conduction characteristics of a revolving thin wall under high-temperature are obtained through the heat conduction analysis of a 2.5D braiding CFRP engine structure. Then, through the test under the ground state of oxygen enrichment, it is proved that the structure can be used under high-temperature of 950℃ for long time. The consistency of finite element analysis and test results verifies the calculation correctness and the rationality of compensation parameters selection in test. The study has a good guiding significance to the application of 3D braiding composites in engineering.

Abstract:In order to reduce development cycle and test costs of high quality powder metallurgy new products, hip near net-shape forming process of bushing bearing was simulated by Marc. The results show that product geometric dimensions change greatly and the relative density reached 0.98,the local tip position relative density is only 0.85 by the process of forming. In order to improve the local position density and ensure the overall quality of the product, an improvement program by improving the capsule and mold structure, the local increasing in the amount of powder is proposed. The result has provided theoretical guidance for the actual production by numerical simulation.

Abstract:To solve the metal fasteners and composite materials for thermal expansion mismatch mechanical connection process, this paper carried out the development of composite materials threaded fasteners. Through analysis and comparison, appropriate resin system was choosen, and molding methods were studied.We developed a M5 composite threaded fasteners and created a numerical simulation model.The mechanical properties of the fastener simulation was expended, test results show that the composite fastener material properties meet the design requirements. Composite threaded fasteners were succefully and the applications range of resin matrix composite structures was further expanded.

Abstract:This paper investigates effect of different types of surfactant (Tween80 and SDBS) and SDBS concentration on closed-cell melamine foam. Melamine-formaldehyde (MF) resin was synthesized then the foam samples were prepared based on the MF resin. The surface tension test result showed that the surface tension of resin by addition of SDBS was lower than that of Tween80. The surface tension decreased at first and then unchanged afterwards with SDBS concentration increasing. The SEM photos and mechanical test results showed that when surfactant concentration was 3%, cell diameter of the foam with SDBS was smaller and more uniform than that of foam with Tween80. With the SDBS concentration increasing, cell diameter decreased, the uniformity of the size distribution increased initially and decreased afterwards and tear damage of cell wall was serious. By the impact of the foam structure, the compression property of the foam was optimal with the SDBS concentration of 3%.

Abstract:In this paper, polyetheretherketone is modified by graphite and polytetrafluoroethylene. The PEEK composite coatings with different graphite mass fraction are prepared on the surface of stainless steel by cold pressing sintering method controling the mass ratio of polytetrafluoroethylene and polyether ether ketone unchanged. The results show that the crystallinity of the PEEK composite coating decreases gradually, the hardness of the coating firstly increases and then decreases, the friction coefficient of the composite coating decreases, the wear rate decreases first and then increases with the increase of the graphite mass fraction. When the mass fraction of graphite is 4%, the hardness is the highest (21.78HV), the friction coefficient is 0.0461, the lowest wear rate is 2.06×10^-6 mm³/(N·m). The wear resistance of the coatings significantly increase compared to the previous study. However, the high graphite mass fraction will decrease the flexibility of molecular chain. The segment movement is declined. The wear resistance of the coating is greatly reduced.

Abstract:In order to reduce antenna reflector weight, the aluminum alloy is replaced by resin composite. The 3D model of antenna reflector was designed. The model of antenna reflector with two kinds of material were simulated by finite element software. The results show that the composite antenna reflector fundamental frequency is 35.23% higher than that of aluminum alloy at the same volume and the weight reduces 41.2%. The thermal deformation of antenna reflector with two kinds of material were simulated at the temperature between -180℃ and +80℃, the composite reflector thermal deformation is 94.25% less than aluminum alloy while the plies are[0/45/-45/90]_2s to the composite reflector root mean square (RMS) is 0.027 mm, the RMS stabilization of composite reflector is superior to aluminum alloy in deep space.

Abstract:The characteristics and mechanism of the oxide layer in ELID groove profile grinding process were investigated. The non-uniform contact during ELID groove grinding and the effect of oxide layer on the grinding force and the surface roughness were studied. As the current increases from 1 A to 4 A, the thickness of oxide layer decreases from 35.33 μm to 11.07 μm. Meanwhile, the normal grinding force increases from 7.06 N to 36.12 N, and the tangential grinding force increases from 1.62 N to 4.47 N. R_av increases from 0.256 μm to 0.355 μm, and R_ap increases from 8 nm to 13 nm. The result indicates that as the thickness of oxide layer decreases, the grinding force and surface roughness increase, while as the thickness of oxide layer increases, the grinding force and surface roughness decrease.

Abstract:SiO_2f/SiO₂ composites were prepared through repeated infiltration and solidification process, using quartz fabric. Quartz fiber waviness was generated by molding. The tensile strength of SiO_2f/SiO₂ composites with bending fibers were tested. The fracture process was studied. The results showed that bending fiber will lead to the decrease of tensile strength. The minimum tensile strength was 5.5 MPa. The composites with curved fibers fractured layer by layer. The bending fiber will lead to the increase of fracture strain, the maximum fracture strain was 1.19%.

Abstract:We try to fabricate an ultra-thin beryllium bronze curved tapes for space elastic self-expanding boom (lenticular boom). The welding process is one of the difficult problems in development of lenticular boom. In this paper, the welding forming of ultra-thin beryllium bronze curved tapes is studied and technique parameters are optimized. Test results show that optimized technique parameters are welding voltage 180 V, pressure holding time 7 s. Also, after 340℃, 2 h heat treatment, nominal shear strength of welding joint increases from 52 MPa to 68 MPa. Finally, fracture mechanism of welding joint is related to welding energy closely, with increasing welding voltage, nominal shear fracture transfers from welding joints zone to heat affect zone.

Abstract:Optimum process parameters of laser beam welded T joints for 2524 and 7150 aluminum alloys are investigated in this paper. The microscopic structure and mechanical properties for T joints are studied by metallographic analysis, microhardness and tensile test. Test results show the grain in welding seam is fine and dense.The microhardness is lowest in welding seam. The tensile properties for joints in x direction is 384 MPa, while in z direction is 236 MPa.

Abstract:In order to study the welding mechanical properties of titanium alloy TA15 fabricated by laser melting deposition manufacturing, the specimen of welding joints were welded using electron beam and laser beam to obtain the welding mechanical properties, microstructure and microhardness by metallographic test, hardness test etc.. The results show that the highest tensile strength of two different welding ways can reach 953 MPa and the welding coefficient is greater than 0.9. Furthermore, the microstructure is mainly α' basket-weave martensite structures; and the heat affected zone is consisted of α phase and an acicular structure. Finally, titanium alloy TC4 fabricated by laser melting deposition manufacturing performs similar welding characteristics with that by traditional manufacturing.

Abstract:High purity tungsten target was prepared by hot isostatic pressing technique and annealed at different temperatures. The microstructure and internal stress of high purity tungsten target were characterized by metallographic microscope, TEM, XRD and hardness tester. The results show that high purity tungsten target after vacuum annealing at 1 200℃ retains the fine grain structure obtained by hot isostatic pressing treatment, grain size does not grow but the dislocation density, lattice distortion and hardness are reduced greatly. This is due to the high purity tungsten target by hot isostatic pressing generates recovery after annealing treatment and the internal stress is released. When the annealing temperature is below 1 200℃, the internal stress of tungsten target cannot be removed completely. When annealing temperature is above 1 200℃, the grain size of the tungsten target begins to grow. So the optimum annealing temperature of high purity tungsten target prepared by hot isostatic pressing is 1 200℃.

Abstract:To maximize using the excellent material performance of titanium alloy, the high speed cylindrical grinding experiment was studied to the influences of cylindrical grinding parameters on surface quality of TC4. The results show that there is no metamorphic layer on the sub-surface of the workpiece. As the grinding wheel speed increases, the surface quality increases. As the workpiece speed increases, the surface scratches are obvious. As the grinding depth increases, some surface burns exist, and the grinding depth has the greatest impact on the surface integrity. The grinding force and grinding temperature have positive influence on the surface hardness, and the grinding force has a greater impact on the surface hardness. Therefore, reasonable cylindrical grinding parameters can be chosen to ensure greater material removal rate and good surface quality. It will provide guidance for the high speed cylindrical grinding of titanium alloy TC4, to promote its application in industry areas.

Abstract:The relationship between the forming process of serrated chip and the cutting force in the cutting process of titanium alloy TC4 was studied, and the micro plastic deformation zone in the formation of serrated chip was analyzed.The experimental results indicate that the chip is changed from strip chip to serrated chip while the cutting speed is more than 48.75 m/min. The serrated chip formation process leads to the fluctuation of cutting force in the cutting process. The variation of cutting force is consistent with the variation of serrated chip. The width of the plastic deformation zone decreases with the increase of the cutting speed.

Abstract:Using the repair system that consists of 5-ethylidene-2-norbornene (ENB) and Grubbs catalyst as repair agent,and the hollow glass tube with the outer diameter 0.9 mm as the carrier of the repair agent,the bending performance and self-healing efficiency of the composite material contains hollow glass tube were examined by indentation test and three point bending experiments. As a result, the indentation test brings damage to the specimens up to a maximum of 14.67%.Meanwhile, the strength of the damaged specimens under the effect of repair system can restore to the original strength 99.15%.

Abstract:The elastic modulus and hardness of T800SC carbon fiber with different orientation respect to its axis direction were tested by nanoindentation, and the scatter in the data was treated in terms of the two-parameter Weibull statistical analysis. It is shown that with the increase of the intersection angle between the test plane and the axis direction, the elastic modulus and hardness of T800SC increase. When the intersection angle increases from 0° to 90°, the elastic modulus of T800SC rises to (50.96±5.73) GPa from (5.84±2.00) GPa, and the hardness increases from (2.71±0.51) GPa to (5.24±0.91) GPa. For the elastic modulus and hardness of T800SC carbon fiber with different orientation, the modulus of Weibull distribution ranges from 9.0 to 10.5 and from 6.0 to 8.0, respectively.

Abstract:This paper presents a new digital X-ray testing technology for welding joint defects based on half wave height method (HWH) in order to ensure the measurement accuracy of the size of the defects. First, the MTF of the digital X-ray testing system is analyzed and the spatial resolution of the system is confirmed. Furthermore, the typical defects of welding joints are simulated, and the size of these defects is measured using HWH. The results are as follows:(1)based on Rayleigh criterion, the spatial resolution of the X-ray testing system is 4.5 Lp/mm determined by the double wire image quality indicator; (2)the measured sizes of the welding joint defects agree with the actual sizes, and the measuring errors are within 6.3%, thus, the influence of human factor can be avoided using the HWH method, and the accuracy can satisfy the testing requirements of conventional products.