Abstract:Advanced materials and processing technology are the key foundation of the aerospace vehicle structure. With a brief discussion of the classification and development trends of the aerospace vehicle structure of China， this paper summarizes the application and development requirements of the main body structure of space vehicles， including metal materials， composite materials and intelligent materials. Meanwhile the future development trend of advanced processing technology of aerospace structure is summarized from five aspects， including ultra-large-sized structure manufacturing， integral high performance manufacturing， composite structure manufacturing， additive manufacturing and green manufacturing， and the interested process technologies are proposed.

Abstract:Lightweight multifunctional structure is an important technical route towards lightweight spacecraft equipment. This paper reviews the design and manufacture techniques for lightweight multifunctional spacecraft structures， focusing on the status and development trends in the following aspects： three-dimensional lattice structures with high load-bearing capacity， stable structures under thermal deformation， smart deployable structures， separation and unlocking structures， electromagnetic stealth structure， and novel connection techniques for composites. Critical technical issues faced by the development of novel spacecraft structures are briefly analyzed at the same time.

Abstract:The properties and applications of composite materials are key features to evaluate the advancement and reliability of aerospace vehicles. Composite materials are fundamental to support the development of various aerospace vehicles and decisive to success or failure of the flight mission. This paper reviews the recent progress of thermal structural materials， thermal protection materials， high-temperature wave-transparent materials， thermal insulator and structural composite materials. Finally， the authors believe that novel materials for extreme environment， reusable thermal protection materials， the 3rd generation advance structural composite material and the cost-effective manufacture technology are future directions of composite materials for aerospace applications.

Abstract:With the development of aerospace vehicles， new requirements have been put forwards for the polymer matrix composites， which promote the development of polymer matrix composites and their manufacture technologies. A comprehensive review is presented to introduce the latest progress of polymer matrix composites， manufacture methods and applications in the aerospace filed. The future perspectives of polymer matrix composites in aerospace field were concluded.

Abstract:The basic research on the correlation between composition， microstructure and properties of Al-Li alloy is reviewed， including the alloying effect and mechanism of main alloying elements Cu and Li， and micro-alloying elements of Mg， Ag， Zn and rare earth （RE）. In the research of main alloying elements， it is described emphatically that the strength is enhanced with Cu+Li total atomic fraction and Cu/（Cu+Li） atomic faction ratio， but the IGC resistance is deteriorated with Cu/Li ratio， the corresponding mechanism is explained. In the research of micro-alloying elements， it is expounded that the samll addition of Mg+X （X=Ag/Zn） increases T₁（Al₂CuLi） precipitation rates and improves the strength， and the effect displays as Mg+Ag+Zn>Mg+Ag>Mg+Zn>Mg. Meanwhile， it is described that Zn addition increases IGC resistance but Ag addition decreases IGC resistance. Furthermore， the adverse and beneficial effects and related mechanism of RE elements in Al-Li alloy with higher Cu/Li ratio and low Cu/Li ratio are summarized， respectively. In addition， the application technology development of spinning， friction stir welding （FSW）， argon arc welding， chemical milling of Al-Li alloy is briefely described.

Abstract:It is an important method to improve the comprehensive properties of metal matrix composites by introducing nano-ceramic particles into the alloys. In the present work， the research status of in-situ TiB₂/Al composites was summarized from three aspects： the preparation methods， the microstructures of the composites under different processing techniques， the mechanical properties of the composites. TiB₂ particle reinforced aluminum matrix composites prepared by in-situ methods have the advantages of small particle size and good interface bonding with matrix. The dispersion of nano-TiB₂ particles can be modified through alloying design， hot working and rapid solidification. Compared with metal matrix composites prepared by external method， in-situ TiB₂/Al matrix composites have excellent mechanical properties， such as elastic modulus， strength， fatigue resistance， creep resistance and so on.

Abstract:Research background， progress and current research status of composites for cryotanks are reviewed systematically. The molding process of composite cryotanks， the safety between composites and cryogenic propellants and the low-temperature mechanical properties of composites are highlighted. Studies have shown that the automatic fiber placement promotes the development of non-lined composite cryotanks. A large number of microcracks are formed in weak areas such as interfaces under cryo-thermal cycling， and the leakage path of low-temperature propellant can be formed under mechanical load. Epoxy resin system with excellent liquid oxygen compatibility， mechanical properties and suitable processing performance is the key to develop composites for liquid oxygen storage tanks. Revealing the effects of cryo-thermal cycling and modification methods on mechanical properties of composites is of great significance to the application of reusable spacecraft composite cryotanks.

Abstract:Shape memory polymer and its composites are a type of intelligent materials that can convert between the temporary shape and original shape under corresponding external stimuli. Shape memory polymer and its composites have many advantages， such as low density， low cost， large recoverable deformation and controllable stimulus mode， etc.， and have shown great application potential in the aerospace field， including space deployable structure， releasing mechanism， morphing aircraft， etc. Most of these applications are in the development stage， some of which has already completed the functional verification on the ground， and a few of which have been tested in space. This work first summarized the classification of SMP and SMPC， as well as the performance change of SMP under adverse spatial environment factors. Subsequently， space deployable structure of SMPC are summarized， including hinge， truss， solar array， SMPC releasing device， morphing structures and 4D printed deployable structures. Finally， the article looks forward to the development trend of materials and structures.

Abstract:In recent years， with the continuous development of aerospace technology， aerospace materials will face more complex and harsh environment in the use process. Research on coating materials with different protective functions such as high hardness， high wear resistance and high corrosion resistance has become a current research hotspot. The research progress of lubrication coating， wear-resistant coating and corrosion-resistant coating is reviewed， including diamond-like carbon film， molybdenum disulfide film， nitride coating， graphene based coating， etc. On this basis， the design methods and technologies of composite， gradient multilayer and nano multilayer structures are introduced， and the enhancement mechanism of coating performance is discussed. It is pointed out that the future development direction of space functional protective coatings is to prepare ultra long life space functional protective coatings through cross scale structure design and comprehensive protection mechanism.

Abstract:As a new type of high safety and high reliability pyrotechnic device， the exploding foil initiator can be widely used in many technical fields such as the ignition and detonation of weapon systems， the actuation separation of aircraft and spacecraft. Starting from the development trend of pyrotechnics integration， miniaturization and low cost， the research status of MEMS explosive foil initiator chip and high voltage switch is introduced based on thin film integration process， low temperature co-fired ceramic process and printed circuit board process. The respective characteristics are analyzed and compared from the aspects of design， preparation， firing performance， and cost. Finally， the research progress of exploding foil initiator chips in new fields such as overpressure initiation， electric explosion and plasma discharge coupling are introduced.

Abstract:Deformation mechanism in flow forming of thin-walled tube with helical grid-stiffened ribs was studied based on the combination of numerical simulation and experimental method. The finite element（FE） model for flow forming of thin-walled tube with helical grid-stiffened ribs was first established and verified by flow forming experiment. Then， the stress distribution when the roller rotates at different regions and strain distribution of formed tube were analyzed based on the developed FE model. The results show that the material in cylinder wall region is under three-dimensional compressive stress state. The material in outer surface of rib region is also under three-dimensional compressive stress state， while the material in inner surface of rib region is under compressive stress in the radial direction and tensile stress in the tangential and axial directions. The spun tube is characterized by non-uniform deformation. The plastic strain in outer surface is larger than that in inner surface， and plastic strain in cylinder wall region is larger than that in rib region. Moreover， the strain characteristics in cylinder wall region are compression in the radial direction and tension in the tangential and axial directions. While， the strain characteristics in rib region are radial compression in the outer surface and radial tension in the inner surface.

Abstract:In order to meet the requirements of new thermal insulation materials for the steam pipeline of nuclear submarine， a new kind of thermal insulation structure based on polyimide foam was designed and manufactured for the surface of submarine steam pipeline. The thermal insulation performance and structural stability of the thermal insulation structure during use were studied according to the application requirements of submarine steam pipeline. The thermal insulation mechanism was also investigated. The results indicate that the external surface temperature of the insulation structure is 45.2 to 46.5 ℃ during the continuous heating at 280 ℃ for 480 hours. Furthermore， it is also found that the structural and dimensional deformation is almost 0 during the continuous heating test and the subsequent static test for 720 hours. It is noteworthy that the multi-layer polyimide foams applied as insulation structure of steam pipeline can solve the processing and environmental problems related to the inorganic rock cotton system. The data in this paper will provide technical and practical support for the practical application of polyimide foams on steam pipeline surface.

Abstract:The ablation morphology and insulation properties of the low density thermal protection material on different combination of thermal protection structure were investigated by quartz lamp ablation experiments. It is shown that the morphology is different with thermal protection structure. The morphology is effected by the temperature gradient for longitudinal direction and in-plane direction of the thermal protection structure. The less temperature gradient， the more heat accumulated on the ablation surface， and the more obvious of the carbonization characteristic. The ablation matching is realized between the low density ablation material and higher density material for the combination of in-plane direction. It is revealed that the ablation efficiency and the thermal protection efficiency is higher. The areal density and ablation morphology can be considered for the design of the thermal protection structure. The high efficiency thermal protection and insulation and lightweight design can be achieved by rational utilization of thermal protection structure.

Abstract:C/SiC-HfC composites were prepared by PIP process with carbon fiber as reinforcement and polycarbosilane and polyalkyl hafnium as precursors. It was found that the C/SiC-HfC composites had lower density， and much better mechanical properties at high temperatures compared with C/SiC composites，and matrix with HfC had a better protection to the carbon fiber in the static oxidation test under 1 650 ℃. The density of C/SiC-HfC composites is about 1.92 g/cm³，the bending strength at room temperature is 245 MPa，and the high temperature bending strength is 424 MPa at 1 800 ℃. The better mechanical properties of C/SiC-HfC composites at high temperatures are due to the fact that the addition of HfC can inhibit the growth of silicon carbide and reduce the probability of large cracks in the matrix. The addition of HfC on the surface made the SiC oxidized to SiO₂ in time under 1 650 ℃ in air， SiO₂ coating was formed on the surface of the fiber and the matrix，which prevented the further oxidation inside the material.

Abstract:To solve the problems of poor formability at room temperature and weakening property at elevated temperature， a new process of cryogenic forming was proposed to form Al-Li alloy curved-shaped compoent， based on the double increase of elongation and work hardening at cryogenic temperature. The deformation behavior of 2195 Al Li alloy sheet at different cryogenic temperatures and heat treatment states was studied. The critical temperature of double hardening was determined to be lower than -140 ℃. The elongation could be increased to more than 40% and the hardening index could reach 0.44. The cryo-forming device was established. The 2195 aluminum lithium alloy spherical bottom with a diameter of 200 mm was formed for the first time. The ratio of depth to diameter reached 0.55， the forming limit was increased by 104%. Finally， the corresponding thickness and springback distributions were clarified， the maximum thinning rate is 10.3%.

Abstract:The BJ-4210 wire was prepared by adjusting the chemical composition and adding micron in-situ TiB₂ particles to solve the problems of high crack sensitivity and softening of welding joint during welding of 2195 aluminum-lithium alloy. In this paper， the crack sensitivity， mechanical properties and microstructure of joint were investigated. The results show that the TiB₂ particles， as the nucleation point， can reduce the size of weld grain and changes the morphology of the grain， which can effectively reduce crack sensitivity of the joint and improve its mechanical properties. The tensile strength of joint is 370 MPa， while the elongation of joint is 3.1%. The research of BJ-4210 wire provids technical support for the engineering application of 2195 aluminum-lithium alloy.

Abstract:According to the requirements of oxidation resistance of new low-density Nb-Ti alloy， Si-Cr-Ti oxidation resistant coating was studied， focusing on the changes of oxidation resistance and microstructure of the prepared coating before and after oxidation. The results show that coating life is more than 10 hours at 1 200 ℃， and the thermal shock resistance of coating is good； A diffusion layer is formed between coating and substrate to ensure bonding strength of coating； In high temperature atmospheric environment， a glassy SiO₂ layer which can isolate oxygen and fill the gap is formed on surface layer of coating， so it has good oxidation resistance.

Abstract:The effect of pre-stretching on microstructure， mechanical properties and strength contribution of 2195-T8 Al-Li alloy with 21 mm plate thickness was investigated. The results show that， the diameter of T1 precipitates decrease and their number density increase with increasing the pre-stretching； while the diameter and the number density of θ′ precipitates decrease. The yield strength increases from 596 MPa to 638 MPa with increasing pre-stretch from 3% to 15%， but the elongation decreases from 13.8% to 10.7% when aged at 148 ℃ for 38 h. With increasing the pre-stretch， the contribution of precipitation strengthening to yield decreases， and the contribution of work hardening increases. The yield strength depends on the combined effect of work hardening and precipitation strengthening.

Abstract:The galvanic corrosion behavior of Ti-15-3 titanium alloys and MT700/603B carbon fiber reinforced resin composites in alternate salt spray environment was studied. The effects of carbon fiber surface state， gap width and corrosion time on corrosion sensitivity and corrosion characteristics were analyzed. The results show that titanium alloy suffers the most serious degradation when the gap width is 0.06 mm. Compared with crevice corrosion， the corrosion weight loss rate and corrosion oxide area of galvanic corrosion are significantly larger under the same corrosion conditions， which indicates that the corrosion degree of galvanic corrosion is more destructive than crevice corrosion. The corrosion damage is more drastic in Cr region with nonuniform distribution.

Abstract:The skin looseness of large-scale integral carbon/silicon carbide composite skeleton and skin structure in 165 dB thermal noise test was analyzed. The mechanism of skin looseness in noise and vibration environment was proposed， which was caused by the increase of breathing vibration amplitude of skin due to the large free hanging area of skin and skeleton assmbly.The simulation results show that the displacement response increase about 1.72 times with the increase of local free hanging area of the skin and skeleton under the same acceleration excitation. Three groups of flat plate test pieces with assembly clearance of 0.2， 0.6 and 1 mm are used to verify that the skin looseness problem is repeated. When the gap between the skin and the skeleton is large， the thickness of the adhesive layer is also larger. After several times of thermal loading， the adhesive performance of the adhesive layer decreases， and the air suspension phenomenon between the skin and the skeleton appears， which leads to the skin loosening under the vibration excitation. Finally， the improvement measures are put forward to ensure that the maximum gap between the large-scale skin and the skeleton is not more than 0.3 mm.

Abstract:The micro-defects on the surface of VW63Z rare earth magnesium alloy castings were shown as "stripe fluorescence" as a result of fluorescence detection. The micro-defects which cannot be removed by mechanical processing would directly scrap the castings if it appeared on the non-machined surface of the casting. The microstructure of the surface defects of castings and their formation mechanism were investigated in this paper. Results showed that the main component of the micro defects was the double-layer oxide film of rare earth oxide， some of which contained inclusions； the confluence of the molten metal made the surface micro defects to form more easily.The laser melting technology was used to treat the surface micro-defects of the casting. When the output power of the flat-top laser beam was 800 W， the microstructure of the melted layer presented the dendrite characteristic， had finer grains and good combination with the matrix. The depth of the remelted layer was about 915 μm， which could basically repair the surface defects of the casting while controlling the heat-affected range of the casting. The fluorescence detection of the original defect position showed no streak defects.