Abstract:Reusable thermal protection materials with lightweight， high temperature resistance， high damage resistance， reuse， easy maintenance and other properties are key materials for air space shuttle aircraft， which affect the progressiveness， reliability， maintainability and economy of aircraft. This paper reviews the development history，research status and applications of several typical thermal protection materials，such as rigid ceramic tile， flexible insulation blanket， anti-oxidation C/C，C/SiC， TUFROC and etc.，which are widely used on fuselage， nose cap， leading edge and control surfaces of various aerospace vehicles. The damage and performance degradation behavior of typical thermal protection materials during high-temperature service is summarized， and a method for studying the reusable performance and life prediction of materials based on material damage is proposed. Finally， it is proposed that the development of high-performance and reusable thermal protection materials， the development of theoretical methods and standards for the reuse of thermal protection materials， and the establishment of a database of reusable thermal protection materials are the key directions that need to be focused on in this field in the future.

Abstract:In response to the demand for future reusable spacecraft， this article first briefly analyzes the application progress and characteristics of heat-resistance composite structure design technology for typical reusable spacecraft abroad， including the American X series and the Dream Chaser spacecraft. Then， from the aspects of structural material selection， design and analysis， the current status and development direction of the main engineering technologies related to the large-scale application of advanced heat-resistant resin-based composite in the overall structure of reusable spacecraft is discussed， theoretical analysis for the future development of reusable spacecraft structures from an engineering application perspective is provided. Finally， the key research content of the heat-resistant composite structure design technology for future reusable spacecraft is introduced.

Abstract:High-temperature resin-based composites possess advantages such as low density， high specific strength， high specific modulus， fatigue resistance，corrosion resistance， and high design flexibility. Due to its significant potential for lightweight structural applications，a considerable attention in the aerospace field is received. This paper focuses on three high-temperature resins-bismaleimide， polyimide， and phthalonitrile， and their composite materials.A review of the historical development，processing techniques， mechanical properties， and aerospace applications of these resin matrices is provided. Finally，by comparing their processing characteristics， mechanical properties， and typical engineering applications，a insights for material selection in the aerospace industry is offered.

Abstract:The rocket storage tank is an important component of the launch vehicle， but the service environment is relatively harsh. The rocket storage tank not only store liquid propellants but also bear complex structural loads. Structural material is the foundation for the development of tank manufacture and the key to the revolution of space vehicles. This article mainly introduces the application and development status of structural materials for rocket storage tank at home and abroad. It reviews metal materials such as aluminum alloy， stainless steel， titanium alloy， and composite storage tanks， systematically summarizes the revolution process and application situation of storage tank materials， and puts forward new insights and prospects for the development direction of storage tank materials in the future.

Abstract:Reusable launch vehicle is one of the key goals for the development of space transportation systems. Mechanism technology is an important support for the multifunctional and reusable development of launch vehicles， and its damping and buffering functions have a wide demand for damping mechanisms.Eddy current damper is a non-contact damping generation method base on the eddy current principle， which has the advantage such as no wear， no leakage， stable performance， high reliability， good maintenance， and easy long-term storage. And it is a velocity type damping mechanism based on the principle of eddy current damping， which wildly used in vehicle breaking，building damping and other engineering fields. The basic principle of permanent magnet eddy current dampers is elaborated， which are classified into linear type， axial rotational type and radial rotational type， and the types of materials used are analyzed. The requirements of damping mechanisms for reusable launch vehicles in terms of deployment buffering， vibration suppression， impact buffering， and active control are elaborated.The application status and development prospect of eddy current damping technology in the field of launch vehicle mechanism design are analyzed.

Abstract:In response to the problem of difficult control of deformation during the curing process of typical composite material structures，the curing deformation of typical composite structures was simulated and predicted， and the curing deformation was controlled and verified from two aspects：curing process and die compensation.In terms of curing process， the optimal curing process curve was determined based on the deformation data of each design point. In terms of mold compensation， a method of adaptive adjustment of the finite element model of the component was proposed. A collaborative control method based on global compensation was adopted to comprehensively consider the curing process parameters and mold surface compensation.The results show that the solidification deformation error of L-shaped components through simulation is 12.4%. The optimal solidification process curve of L-shaped components obtained by response surface optimization algorithm has a deviation of no more than 3.3% between the predicted solidification deformation value and the minimum maximum deformation value at each experimental design point. After adaptive adjustment of the T-shaped reinforced wall panel finite element model， the maximum relative error between the numerical simulation value and the experimental measurement value for the deviation distance between the lower surface and the target profile is 17.20%.The mold of the semi cylindrical wall panel is compensated by the collaborative control method of global compensation， and the maximum curing deformation is reduced by nearly 90% compared with the traditional single mold surface compensation control method.

Abstract:In order to develop high-performance quartz fiber felt with good thermal insulation and mechanical properties， the effects of the thickness of quartz fiber felt on its thermal insulation performance were predicted based on the mathematical equation of heat transfer.To improve the mechanical properties of fiber felt， the influence of adding different layers of quartz fiber cloth to the fiber felt on its mechanical properties was investigated Additionally， the influence of needle-punched density on the thermal insulation and mechanical properties of quartz fiber felt was also discussed. The results show that the simulation temperature of quartz fiber felt has a good agreement with the experiment， with the calculation accuracy is up to 94.8%.The thermal insulation performance improves by about 20℃ when the thickness of the quartz fiber felt is increased by 2 mm.Adding quartz fiber cloth significantly improves the breaking strength and tearing strength of fiber felt.However， excessive needle punched density reduces its mechanical properties and damage the structure of fiber felt .

Abstract:Tank is one of the key components of the reusable rocket， and the integrity evaluation of the weld is difficult for designing and manufacturing of the reusable rocket tank. According to the elastic-plastic principle of fracture mechanics and the two-parameter 2A failure evaluation method， the weld crack of reusable rocket tank is quantitatively evaluated. Based on the evaluation process of tank weld integrity， the method of solving residual strength and critical crack size of tank bottom weld is given. The results show that the critical crack size decreases with the increase of applied stress， and the residual strength decreases with the increasing of critical crack length. Under the same applied stress， the critical crack size decreases with the decrease of the external diameter of the structure. Under a certain critical crack size， the residual strength increases with the increase of the external diameter of the structure. In this study， the failure criteria of welded joints with welding defects for reusable storage tanks are established， which is of great significance to guide the analysis and determination of high-risk failure hazard areas for reusable storage tanks.

Abstract:TA17 titanium alloy was an important structural material in aerospace engineering， and its fatigue crack propagation behavior directly impacted the safety and integrity of the entire structure.Based on the fatigue crack growth tests of compact tension specimens of Cr2Ni2MoV steel with oblique initial crack， the XFEM module in ABAQUS software was verified in analyzing fatigue crack propagation performance under plane stress conditions， and then the XFEM module was applied to analyze the fatigue crack propagation properties of TA17 titanium alloy and connection.The research results indicate that reducing the maximum load， decreasing the loading ratio， and utilizing obround holes can effectively enhance the fatigue life of TA17 titanium alloy connection. The S-N curve used to predict the fatigue life of the connection is obtained by adopted of XFEM module. When the load of TA17 titanium alloy is increased by 33.3%， the predicted fatigue life is reduced to 1/4， which provides reference for the engineering fatigue design of the TA17 titanium alloy structure.

Abstract:A series of silica aerogel in-situ filled composite foams were prepared by sol-gel process using ultra-light open-cell flexible polyimide foam as matrix.The density of composite foam was adjustable from 10 kg/m³ to 100 kg/m³，the thickness was adjustable from 1 mm to 400 mm，and the maximum macro size could reach 1 m×1 m.The cell structure，thermal insulation performance and thermal performance were systematically characterized，and the thermal insulation mechanism of polyimide foam in-situ filled with silica aerogel was analyzed.The results show that the introduction of silica aerogel can effectively reduce the thermal conductivity of composite foams at room temperature and improve its thermal insulation performance.With the increase of silica aerogel content，the thermal conductivity of the composite foam decreases from 38.8 mW/（m·K） to 19.6 mW/（m·K）.When the hot end temperature is 300 °C，the thermal conductivity of the composite foam is only 61.1 mW/（m·K）.After filling the silica aerogel，the thermal stability of the composite foam is significantly improved， and the thermal weight loss residue is about 80% at 900 °C.

Abstract:The processing properties， rheological properties and heat resistance of a high-temperature resistant modified bismaleimide resin （805） were studied. On this basis， TG800/805 domestic high-strength medium modulus carbon fiber composite was prepared， and the mechanical properties and fracture microstructure at high temperature and room temperature were characterized. The results show that the lowest viscosity of 805 is 1.6 Pa·s， which has excellent processing properties. TG800/805 composite has excellent mechanical properties. After heat treatment at 280 ℃， the mechanical properties retention rates of flexural strength and inter-laminar shear strength at 280 ℃ are 68% and 52%， and the glass transition temperature（T_g） of 805 is 356 ℃，indicating that TG800/805 can be used at 280 ℃.

Abstract:The silazane compounds was synthesized through convenient and efficient method. Using it as a curing agent， lightweight components and ablative dimensional components were studied separately. Finally， a low-density heat-resistant coating for reusable aircraft with excellent thermal stability， high dimensional stability at high temperatures and good ablation resistance was obtained. The results indicates that the density and mass retention rate of the heat-resistant coating tend to stabilize after a finite number of static ablations， and the mechanical properties meet the usage requirements. The coating has undergone up to 10 times of quartz lamp ablation assessments， and its thermal insulation performance has remained unchanged. In addition， after 5 times wind tunnel ablation assessments， ablation resistance and thermal insulation performance of heat-resistanct coating has remained unchanged， which shows that heat-resistant coating can still provide good thermal protection for aircraft after a finite number of repeated use.

Abstract:The reusable storage tank is a key component of reusable launch vehicles. Long service life， complex stress， and unique configuration are the difficulties in the development of reusable launch vehicles. In order to find a scientific and reasonable development method， the design， manufacturing， and testing of reusable liquid oxygen storage tanks are studied. On the basis of the development of traditional rocket storage tanks， innovative research is carried out， the design idea， design concept and material selection of the tanks is expounded. The front support of the liquid oxygen storage tank， the connection structure between the energy dissipator and the accessories inside the tank are invented. Research on the forming process of the bottom of the tank and the welding method of the tank has shown that the integral spinning forming process is superior to the traditional melon petal welding process， and vacuum electron beam welding can ensure the quality and dimensional accuracy of the box. Innovation in the experiment includes replacing full-scale real environment testing with specimen level front support structure selection testing and ultimate strength testing， conducting out of external energy dissipator testing instead of internal testing， and incorporating fiber optic detection technology into traditional static tank testing.

Abstract:The longitudinal unlocking mechanism was a set of mechanism products for connecting and separating the two halves of the launch vehicle fairing. Its core component， the locking hook， need to be unlocked and assembled repeatedly during acceptance and assembly. The spring was the driving element used for the sparation of the locking hook. In order to improve the reliability of springs， this paper studied the use of aluminum electroplating in ionic liquid to replace the electrogalvanizing with hydrogen embrittlement. The process method was first formed through the typical product trial plating， and then the spring trial production was carried out， and finally the heat environment and the hook lock mechanism test were used to verify the reliability of the springs. The results show that shot peening in the process will cause the spring force to decrease slightly，where as the spring in this state also can meet the environmental adaptability requirements. Repeated unlocking can cause the spring plating layer to wear， and the force will decrease by about 5%， but still meet the design requirements.Spring using aluminum electroplating in ionic liquid can replace electro -galvanizing. The post-treatment of shot peening in process implementation needs to be strictly controlled， and the effect of repeated use on spring coating and force value needs to be concerned.

Abstract:In-situ nanoparticles reinforced Al matrix composites had low density，high modulus and high strength，making them one of the key materials for achieving lightweight equipment structure.The amount of plastic deformation during processing is an important factor determinging the microstructure and properties of aluminum matrix composites. Scanning electron microscopy and backscattered electron diffraction techniques were used to analyze the particle distribution and three-dimensional grain structure in composites， as well as the evolution law with extrusion deformation.The room temperature tensile performance and fatigue resistance of composite materials under different organizational structures were discussed. The results show that TiB2/7050Al composite have high elastic modulus （78-84 GPa）， high plastic yield （6588 MPa ·%）， and high fatigue limit （289 MPa）， and will have broad application prospects in aerospace and other fields.

Abstract:In response to the high sensitivity of joint cracks and poor mechanical properties of T8 2195 Al-Li alloy during argon arc welding， the development of 2195 Al-Li alloy welding wire was carried out， and the microstructure， crack resistance， and comprehensive mechanical properties of the joint were studied. The results indicate that the 2195 Al-Li alloy fusion welding joint is mainly composed of α-Al， Al₂Cu and Al₃（Ti，Zr） phases， it has excellent crack resistance and mechanical properties.Its crack sensitivity K₁ is less than 1%， K₂ is 0%， and the tensile strength of the joint at room temperature is about 390 MPa，and elongation is 6.3%. The development of BJ-4505 welding wire provides technical support for the engineering application of 2195 Al-Li alloy.

Abstract:The heat-humidity aging process of phenyl silicone rubber is studied， focusing on its tensile， damping， and compression rebound properties. For tensile properties， experimental studies have shown that the material tensile modulus and 100% fixed elongation stress gradually increases with the rise of temperature or humidity.For the damping property， the loss factor gradually decline with the increase of the temperature or the humidity.For the compression rebound property， the compression compression permanent deformation gradually increases with the increase of the temperature or humidity. Moreover， the effect of the temperature on the properties of phenyl silicone rubber is more significant than that of the relative humidity. This is mainly due to the simultaneous occurrence of side group oxidation and hydrolysis during the aging process， which leads to the simultaneous occurrence of molecular chain crosslinking and breaking. Compared with molecular chain breaking， molecular chain crosslinking plays a dominant role. Finally， the storage life of phenyl silicone rubber under different temperature and humidity environments is predicted using the Peck model.Since the damping performance determines the vibration reduction performance of phenyl silicone rubber， the loss coefficient is used as an evaluation characteristic parameter. The results show that at 25 ℃， when the relative humidity changes between 80% and 40%， the life of phenyl silicone rubber changes between 18 and 39 a. This study helps to further understand the aging process of phenyl silicone rubber and provides a method for predicting the life of phenyl damping silicone rubber under different humid and hot environments.

Abstract:The aging property of the rubber compound of insulation layer determined the storage time before the use of the insulation layer. In order to grasp the influence of the storage time of the rubber compound of insulation layer on the subsequent performance of the insulation layer， the storage time of the rubber compound of insulation layer was controlled.The thermal oxygen aging test was used to study the change of properties of the rubber compound of insulation layer after different aging time. The results show that， with the extension of the aging time， the DCP decomposes and the molecular chain of EPDM breaks at high temperature， the mechanical properties， vulcanization properties， adhesive properties and gel content of the rubber compound of insulation layer decreases， while other physicochemical properties do not change significantly. Therefore， in order to effectively improve the storage period of the insulation layer at high temperature and extend the service life， the strict attention should be paid to storage temperature and keeping away from light and ultraviolet radiation.

Abstract:In order to further understand the microstructure and high temperature mechanical behavior of SiC/SiBCN-Si₃N₄ composite， and establish a scientific and reliable quantitative characterization methodology， this paper uses a variety of characterization methods to quantitatively observe SiC/SiBCN-Si₃N₄ material. Firstly， the porosity and density of the material are tested. Then the in-situ mechanical properties of the material at high temperatures were tested and the damage mechanism of the material was analyzed. Finally， an interpretable deep learning model was constructed based on the test data to realize the prediction of the nonlinear constitutive relationship of the material at high temperature. The results show that the average stress prediction error ranges from 0.27% to 0.59%， and the average strain prediction error ranges from 1.96% to 3.41%. Through quantitative analysis， it is also clear that the factors successively affecting the mechanical properties are temperature， off-axis Angle， porosity and density. In this paper， the macroscopic mechanical properties of SiC/SiBCN-Si₃N₄ under different ambient temperature， off-axis angles and external loads are predicted， which provides a new idea for the establishment of high temperature constitutive model of ceramic matrix composites.

Abstract:SiC_f/TC17 composites were prepared by magnetron sputtering and hot isostatic pressing.The off-axial tensile properties and fracture mechanism of SiC_f/TC17 composites at room temperature were studied by observing the fracture morphology of samples by SEM.The results show that the axial properties of the composites change little when the axial deflection Angle of the fibers is between 0° and 2°，and the tensile strength is stable in the range of 1 960 to 1 987 MPa. When the off-axis Angle of the fiber is increased （>2°），the tensile strength of the material is approximately monotonically linear， decreasing from 1 870 MPa to 1 797 MPa.When the fiber off-axis Angle is small （≤2°），the matrix and the fiber fracture plane in the flat region are flat，and the fracture plane of them is parallel.There is no obvious sign of desticking and breaking at the fiber/matrix interface.When the fiber off-axis Angle is larger （>2°），some fibers have "oblique fracture"，the fiber pulling distance becomes longer，and the fiber is no longer in the same plane as the fracture plane of the matrix，and the matrix is seriously torn and damaged.Based on fracture morphology and local load model，two kinds of tensile failure fracture processes of SiC_f/TC17 composites were discussed in detail.When the fiber off-axis Angle is small （≤2°），the crack initiation occurs in the reaction layer with small fiber spacing， and then passivates or deflections at the interface to form a flat area with different cross sections.When the fiber exceeds the limit of bearing capacity， the sample breaks as a whole. When the fiber off-axis Angle is large （>2°），the "tension-shear" coupling effect leads to the interfacial debonding break between the C coating and the reaction layer to form a crack source，and the crack accelerates the reaction layer to be damaged or leads to interfacial debonding resulting in fiber fracture.When the matrix and the remaining fiber exceed the limit of bearing capacity，the specimen breaks as a whole.

Abstract:Lightweight thermal protection materials and strain isolation pad were used as the thermal protection system of reusable launch vehicle.The lightweight thermal protection component was bonded to the surface of the carbon fiber composite skin by the silicone rubber adhesive.In order to improve the bonding quality of lightweight thermal protection system for reusable aircraft，influnence of pressure，pressurizing time and surface treatment on the bonding strength of lightweight thermal protection components and carbon fiber composites were investigated experimentally.The results show that the bonding strength of lightweight thermal protection components and carbon fiber composites increase with the increase of pressure. The bonding strength increases rapidly with the increase of pressurizing time，but the increase rate slow down when the pressurizing time exceeds 7 h.The bonding strength is improved by grinding rough bonding surface or applying treatment agent.The bonding strength is increased by more than 52%， when the two processing methods are applied at the same time.