Abstract:The aerodynamic heating environment for spacecrafts currently under development typically possesses the following characteristics:high enthalpy, high heat flux and long heating time. This in turn has lead to the shift of active research work of heat shield materials, e.g., phenolic-resin based composites, towards enhancing properties such as higher ablation resistance, good heat insulation and even lower densities. To overcome the limitation of materials’ intrinsic properties and to improve their performances, both ablative(resin based) and non-ablative(ceramic based) types of heat shield materials can be further optimized by applying functional coating materials on top of the ablation surface. This review has focused on the recent research effort on the coating material for different thermal protection systems and categorized them into two major types:ablative and non-ablative. Having obtained a comprehensive understanding about their pros and cons, a possible solution is proposed at the end of this article for resin-based ablative composites:coatings consist of silicon-based preceramic polymers that can be cured around the same temperature as phenolic resin but ceramized in-situ during flight.

Abstract:Due to its amazing properties, Ti alloys are widely used in aerospace and aerial industry. HIP powder metallurgy process, which is suspected to a proposal approach to solve Ti alloys’ fabrication problem, is investigated throughout the world. In this paper, it’s character, orgination and development is introduced. Meanwhile, the investigation, approvemnet and practical application of the process of Aerospace Research Institute of Materials & Processing Technology is also introduced.

Abstract:Friction stir welding technology has become the manufacturing trend of launch vehicle aluminum tank due to the characteristics of less weld defects, small welding deformation, high joint performance, and so on. This paper analyzes the rocket tank structure composition and the main weld structure characteristics, and systematically studied all the key technologies used to realize the all-friction-stir-welded tank manufacturing, including conventional friction stir welding technology, phased array ultrasonic inspection technology and repair welding technology. The results of this paper has been gradually applied to the longitudinal weld, the main weld of the dome, and the circumferential weld of the launch vehicle tank.

Abstract:In this paper, research progress of out of autoclave(OOA) composite technology for low porosity composite was reviewed. We presented the influence of OOA materials properties including prepreg, resin and reinforcements on porosity of OOA composite, then, phenomena that affect porosity during curing were analyzed.Afterward, the relationships between porosity of OOA composite and manufacturing process conditions and parameters were also described. Finally, some suggestions on reducing porosity of OOA composite were proposed.

Abstract:The mirrors play a key role in the space optical system, and it has been developed to the fourth generation of C/SiC composites. C/SiCcomposites have become very important materials for light-weight mirrors because of the advantage of low density, high stiffness and strength, considerable flexibility in structural design and so on.In this paper, the characteristics of four generation of mirror were contrast, the preparation process and the structure design of C/SiC composites were summarized, the development of the C/SiC mirror at home and abroad is reviewed.

Abstract:Mapping software Pro/E 5.0 was used to build structure models of 3D angle-interlock composite in warp and weft directions. Finite element analysis software ANSYS was used to simulate the lateral compressive properties of the 3D composite in warp and weft directions. The mechanical behavior of the composite was predicted by investigating the stress and strain distribution of fiber and resin under lateral compressive loads.In addition,the lateral compressive property between warp and weft directions was compared with each other. Results showed that the lateral compressive property of the 3D composite is obviously anisotropic, behaving as the lateral compressive property in weft direction better than that in warp direction.Fiber made the major contribution for subjecting the load,while the resin made the major contribution for deformation.Fibers parallel to the lateral direction are subjected to larger load,while fibers perpendicular to the lateral direction are subjected to smaller load.

Abstract:In this paper, the auto fiber placement machine was applied to process antenna plane, and the fiber placement experiment was conducted with robot. Due to the equation of the antenna, the fiber placement track was designed with the equidistant offset method. By analyzing the placement pressure and the full as time as the smooth during the fiber placement, which decides that placement pressure is 0.2 MPa,and the number of fiber tow is 4. In addition, the joint and the paramedic of the robot are analyzed, the placement tract is simulated by DMU module of CATIA. The fiber placement test is conducted with 16 mm/s speed at 26℃ in order to test and verify the process.

Abstract:Responding to the variability and irregularity of the size and shape, and the uncertainty spatial location of abrasive in diamond wheel, this paper proposes a better virtual model of diamond grain and a workpiece model containing typical cracks,based on the method of random planes to segment the solid and truncated polyhedron in spherical coordinates. The FEM simulation and experiments are carried out on silicon nitride cutting with single diamond grain. The results show that a good agreement trend between simulations and measured results of grinding force. The relative error is less than 8%. The cutting force decreases with the increases of the rotational speed of the grinding wheel, while increasing along with the increases of the workpiece velocity and the cutting depths. The effect of cutting depth on cutting force is maximum.

Abstract:Phenolic impregnated ceramic ablator (PICA-X) were prepared by impregnation of novolac phenolic resin solutions into mullite fiber mat, followed by so-gel reaction and ambient drying. The density of the PICA-X could be adjusted in a range of 0.45 to 0.50 g/cm³ by using different concentrations of novolac phenolic resin solutions. The microstructure, mechanical property, thermal insulation property and thermal stability of PICA-X before and after carbonization were systematically investigated. PICA-X, which are composed of phenolic aerogel reinforced by mullite fiber, exhibit excellent mechanical strength of 26.7 to 34.0 MPa and low thermal conductivity of 36 to 40 mW/(m·K). After carbonization at 1 000℃, the flexural strength and thermal conductivity of the resulting C-PICA-X are 13.9 to 14.5 MPa and 41 to 45 mW/(m·K), respectively. In addition, PICA-X exhibits good oxidation resistance before and after carbonization.

Abstract:The influence law of forming parameters on the spinning of Ti55531 titanium alloy cylinder was analyed.The results showed that using solid solution heat treatment system(880℃+insulation 30min/air cooling) Ti55531 titanium alloy can achieve better matching between the strength and plasticity.When the spinning temperature is 750 to 800℃,the metal fluidity is good,the apparent quality of spinning cylinder is good.And with the increase of spinning passes,spinning temperature can reduced appropriately,but the final spinning temperature is not lower than 650℃,spinning limit thinning rate achieves about 80%.The selecting of feed ratio is between 0.45 to 0.78 mm/r,the using of large feed ratio in the beginning pass can make the workpiece better fit the mould.The relative small feed ratio make the workpiece strip mould easily in the final pass,the pass thinning rate between 30% to 45% is more appropriate,which benefit spinning.

Abstract:CFCC prepared by chemical vapor infiltration (CVI) has the difficulty in quality control. It is very important to study the quality of the material, and it has important significance for the material usage and performance characterization. In this paper, the density uniformity and quality of CFCC are evaluated by ultrasonic method. According to the serious attenuation, the penetration method is used to measure the acoustic parameters:sound velocity and attenuation,and nonlinear parameter evaluation material uniformity,and compared the test by the metallographic method.The results show that,attenuation and nonlinear parameter can accurately evaluate material uniformity,the sound velocity is the most mature uniformity characterization methods among them.

Abstract:Two kinds of FGH4169 alloys with different carbon contents(0.022%、0.078%) were analysed by structure observation and image measurement or statistical calculation. The effect of carbon content on structures of FGH4169 alloy were investigated. The results showed that the average grain size of FGH4169 alloy with high carbon content decreased while the grain size had obvious differences. The type and morphology of carbides did not depend on carbon content.But the carbide size was affected strongly and the FGH4169 alloy with high carbon content formed PPB easily. In FGH4169 alloy with low carbon content, the increased number of strengthen phase, the large average size of strengthen phase grew and the reduce average gap of strengthen phase are beneficial to the improvement of strength.

Abstract:The quality of spot weld bonding in titanium alloy sheet metal was tested by using ultrasonic C-scan method. The specifics of the A-scan signals and the C-scan images were researched under different welding current. The tensile-shear tests were carried out to test the mechanical behavior of spot weld bonding.Results show that the characteristics of C-scan image and the change A-scan signal can divide adhesive, heat effected zone, melting area, nugget zone and weld defects. The nugget diameters of sport weld bonding increase with the increase of welding current, and the failure load average increase from 7 231.5 N to 10 939.0 N. When the current is 7 kA, it can get the information which includes splash and other weld defects from the ultrasonic C-scan image. The failure strength is less than the normal joints. The splash reduces the tensile shear load of the spot weld bonding joints.

Abstract:The pyrolytic process and volatiles of PICA porous phenolics at different stages were investigated by TG-FTIR and PyGC-MS.The results demonstrated that PICA porous phenolics presented two evident weight loss processes.The desorption of small molecules of PICA porous phenolics took place during the first process and H₂O,CO₂,HOCH₂CH₂OH are the main volatiles.The molecular chain of porous phenolics broke up and phenols,benzene series,fused ring aromatics evolved during the second process and it is the main stage of thermal degradation. After high-temperature pyrolysis loose and porous char with a certain strength is formed by the combination of porous phenolics matrix with high porosity carbon fiber reinforcement.

Abstract:The WC/C composite coating was deposited on the 304L stainless steel and silicon wafers by unbalanced magnetron sputtering technology. The microstructures of WC/C coating were analyzed by scanning electron microscope, Raman spectrometer and X-ray diffractometer. Mechanical properties were tested by nanoidenter and scratch tester.Electrochemical workstation and friction tester were used to investigate the corrosion resistance and tribological properties of WC/C coating in artificial seawater. The results indicate that plentiful graphite-like sp² bonds are formed in the coating. It has the composite structure in which WC1-x phase is embedded in the amorphous carbon matrix. Compared to the 304L stainless steel,WC/C composite coating has better corrosion resistance and tribological adaptability in artificial seawater.

Abstract:The processability of prepregs lacks quantitative characterization methods. By studying the rheological properties and the glass transition temperatures of 4 typical epoxy resins and their C/E prepregs’ processability, it proved that the subjective notion of the tack property of prepregs can be characterized objectively by two physical properties:the η* and the T_g. It is shown that epoxy resins with T_g=0℃ or η*=35 kPa瘙
簚s yield optimum tack properties for prepregs.

Abstract:The three-dimensional finite element model of foam core sandwich panel with penetrating defects is established.Finite element analysis is carried out on this model under the uniaxial and twin-axial tensile loading.According to the stress distributions of material principle direction of the scarf-patch repaired panel,the uniaxial and twin-axial tensile strength of the intact and scarf-patch repaired panels are calculated based on the strength criterion of maximum stress.It is shown that under the uniaxial tensile loading,the strength recovery coefficient of the repaired panel is 88.1%,and the initial damage mode is matrix shear failure.Under the twin-axial tensile loading,the strength recovery coefficient of the repaired panel is 97.6%,and the initial damage mode is the fracture of the reinforcing fiber.The optimum number of surface patch is one or two.More surface patches cause local stress concentration and thus strength reduction of the panel occurs.

Abstract:Through drilling on carbon fiber reinforced polymer(CFRP)/titanium alloy(Ti6Al4V) stacks with the carbide twist drill, this paper studied tool wear mechanisms, the influence of titanium layer processing parameters for tool wear and effects of cutting tool wear on the largest tear length of hole entrance.The results showed that the main area of wear is the horizontal and the flank,and the wear of the rake face is not obvious. When drilling the titanium alloy layer,low speed and low feed rate can be used to reduced tool wear.With the increase of the number of holes,the hole entrance of the titanium alloy layer is more stable.