Abstract:Three-dimensional textile composites are widely used in the aerospace field due to their excellent mechanical properties，strong designability and resistance to extreme environments.In order to deeply understand the structural system and mechanical behavior of three-dimensional textile composites applied in high temperature environments， this paper starts from the three-dimensional textile structurec and reviews the structural types of three-dimensional textile composites and their applications in the aerospace field.The molding process and structural characteristics of three-dimensional textile composites are summarized.The research progress of thermo-mechanical properties of three-dimensional textile composites is analyzed. Future research focus and key issues to be solved are proposed in order to provide a basis for the design，manufacturing and application of high temperature resistance/load bearing of a new generation of three-dimensional textile composites.

Abstract:The curing process and cure kinetics of a moderate-temperature-curing adhesive foam had been investigated by dynamic differential scanning calorimetry （DSC） experiments.To confirm a linear relationship between the peak temperatures （T_p） of DSC curves and the natural logarithm of heating rates（β）， in addition to the combination of heating rates β of 5，10，15 and 20 K/min in DSC tests，heating rates β of 1，2.718，7.389 and 20 K/min were designedly set， so that lnβ would be equal and approximate to 0，1，2 and 3 for easy calculation， thus curing parameters and the apparent activation energy （E_a） could be easily and quickly determined. Empirical linear relationships between T_p with lnβ had been sustained by a series of literature data about heating cure， thermal decomposition and crystallization of some polymers. Using the characteristic temperature parameters T₁ and ΔT obtained from the above linear relationship， the magnitude of the activation energy （E_a） could be explained and the kinetic data could be quickly solved. The results have established and proved a simple and reliable kinetic solution other than methods by Kissinger and Ozawa. The simple method for solving the kinetic parameters of thermal-induced reaction or crystallization change is reasonable and effective.

Abstract:In order to improve the quality of riveting，the finite element analysis of the press riveting process under different riveting process parameter was carried out by using ABAQUS software from the perspective of analyzing the hole edge stress distribution and the riveting process parameter rules.The specific influnce rules of process parameters such as prefabricated hole chamfer， press-down amount， riveting speed，etc. on the hole edge stress were deeply explored.Through data analysis method such as equivalent contour and small characteristic function， the optimal combination of riveting process parameters was successfully determined and verified by tensile test. The results show that the optimal process parameters with a chamfer depth of 0.3 mm， a riveting speed of 15 mm/s， and a downward pressure of 3.2 mm can significantly reduce the hole edge stress distribution in around the connecting domain and improve the riveting quality.

Abstract:Directional solidification （DS） was an important process for physical purification of photovoltaic polysilicon. In order to improve the defect of large thermal stress and strain caused by one-dimensional heat dissipation in directional solidification， a innovative unbalanced heat dissipation structure and process were proposed， which used specific thermal resistance designs and heat dissipation channels to reduce thermal stress and strain. Using ProCAST software， three-dimensional numerical modeling of one-dimensional heat dissipation and unbalanced heat dissipation was carried out. The comparison results shows that compared with one-dimensional heat dissipation， the unbalanced heat dissipation scheme can reduce the average thermal stress by 52.56%， increase the average solidification rate by 20.67%， reduce the solidification time by 17.10%， and maintain the stability of the phase change interface in the non-one-dimensional temperature field. Using the YITIPV type vacuum ingot furnace and 3303 industrial silicon raw materials， a large-size ingot （1 m×1 m×0.3 m） control experiment was carried out. The experiment proved that the unbalanced heat dissipation scheme can improve the solidification rate and product quality， the top of the prepared silicon ingot is flatter， the actual total solidification time is reduced by 15.75%， the energy consumption per unit weight of silicon is reduced by 17.86%， the ingot cracks are less， and the effective volume is larger.The sample analysis also shows that the average resistivity of the silicon wafer increase by 7.86%， and the impurity content of the three elements B， P， and Al decrease by 28.6%， 15.2%， and 83.3%， respectively. The experiment not only confirm the effectiveness of the unbalanced heat dissipation structure and process but also verify the adaptability of the numerical model. This new structure and process improve the quality and production efficiency of ingots， reduce the risk and cost of ingot cracking， and have promotion and application value.

Abstract:In order to study the effect of reinforced particle agglomeration distribution on the cutting process of SiCp/Al composites， three orthogonal cutting finite element models with different SiC particle agglomeration size ratios were established and verified. The results show that with the increase of particle agglomeration size ratio， the continuity of sawtooth chip decreases and the shape becomes more irregular， and correspondingly the fluctuation degree， average value and peak value of cutting force increase. The cutting stress in the agglomeration area increases with the agglomeration size ratio increasing. Larger particle agglomeration size ratio leads to an increase in subsurface damage depth and maximum contour peak and valley height.

Abstract:With the rapid development of advanced equipements， it is of great significance to improve the heat resistance for polymer to expand its application in aerospace field. In this paper， 4，4''-（1， 3-phenoxy） phthalonitrile resin （APN） was modified with SiBCN ceramic precursor to produce high heat resistant material （CPN） and the heat resistance property and mechanism of the modified resin were studied.The results show that when SiBCN mass fraction is 20%， the T_d¹⁰ of the CPN is 608.07 ℃ （N₂）. According to the dynamic mechanical analysis （DMA） results， the glass transition temperature of CPN carbon fiber composites is higher than 500 ℃， which is 100 ℃ higher than that of APN-NH₂carbon fiber composites. When SiBCN mass fraction is 40%， the CPN can maintain the integrity of appearance morphology after 30 min treatment at 900 ℃ under aerobic environment. The ceramic precursors can form Si-O and B-O bonds in the modified resin under high temperature conditions， which significantly improves the heat resistance.

Abstract:Aiming at the flame retardant modification of epoxy resin by liquid winding process， the effect of flame retardant addition amount on the properties of resin and composite material was studied. The results show that the viscosity of the resin decreases slightly with the addition of flame retardant， and the curing reactivity does not change significantly. With the increase of flame retardant content， the tensile strength of epoxy resin is basically stable but the impact strength is decreases. The impact strength of epoxy resin added with 30 phr flame retardant is decreased by 44.1% compared with 0 phr. In addition， with the increase of flame retardant content， the thermal decomposition stability of resin is improved， but excessive addition of flame retardant components is not conducive to the stable formation of carbonized layer. According to the above research， the resin system with 20 phr flame retardant additive has the best flame retardant effect， the 50 W vertical combustion test results reach V-0 level， and the mechanical properties have a good retention rate. The tensile strength of NOL ring prepared by modified resin on T700SC reached 2 790 MPa， and the interlayer shear strength is 50.7 MPa. The modified resin and fiber have good interfacial bonding.

Abstract:In order to achieve lightweight absorbing materials， this paper designs the microstructure and synthesis method of the material to combine the dielectric properties of carbon materials with the low characteristics of hollow structures， and prepared carbon hollow sphere （C@air） material has execellent wave absoroption properties with ultra-lightweight. Based on this material， absorbing plates and absorbing honeycomb cores that can be used for the leading edge of stealth aircraft wings are prepared， and electromagnetic simulation and radar reflection cross-section （RCS） testing are conducted on them， the horizontal polarization in the same direction reaches -32.3 dB， and the vertical polarization in the same direction reaches -27.2 dB. It is verified that the material has excellent absorbing performance and application effect， and provides ideas for the design and application of absorbing materials.

Abstract:Reduced graphene oxide/phenolic resin （RGO/PR） hybrid aerogel was prepared by physical blending and ambient drying method based on sol-gel technology. The changes in the microstructure， thermal stability and dielectric properties of RGO/PR hybrid aerogel were investigated with the RGO content， and the application performance of RGO/PR hybrid aerogel as a thermal insulation/microwave absorption composite matrix was explored. The results show that the RGO lamellar structure is uniformly dispersed in the phenolic aerogel skeleton， and the addition of RGO can effectively improve the thermal stability of the aerogel. When RGO with a mass fraction of 4% is added， the T_max of the hybrid aerogel is increased by 17.28℃. RGO has a significant effect on the dielectric properties of RGO/PR， and the real part of the 2 GHz dielectric constant increases from 2.6 to 4.7， which can realize flexible regulation of the electric properties of PR aerogel. When the aerogel thickness is 20 mm， the minimum reflection loss is less than -10 dB. After the quartz fiber reinforced RGO/PR hybrid aerogel is ablated for 500 s at a surface temperature of 1 200 ℃， the maximum back temperature is only 186.31 ℃， showing good thermal insulation performance.

Abstract:Using polysilazane as the curing agent and curing with four kinds of silicone rubber with different phenyl content， the effect of phenyl content on the performance of silicone rubber cured with polysilazane was investigated. The results show that as the phenyl content increases， the glass transition temperature of the silicone rubber at low temperatures increases， the low-temperature crystallization performance of the silicone rubber decreases， and the damping performance of the silicone rubber is significantly improved. At room temperature， the tensile strength and elongation at break of silicone rubber are improved， but the hardness and deformation resistance of the material are reduced.

Abstract:The Al-doped ZnO（AZO） antistatic thermal control filler was prepared by co-precipitation method with potassium silicate used as the binder. The influence of doping ratio， pigment-to-fill ratio and other factors on the resistivity and thermal control performance of the coating was studied， and the inorganic antistatic thermal control coating was prepared. The microstructure and phase composition of fillers and coatings were characterized by SEM， XRD， and 3D measurement laser microscope， and the resistivity and thermal control properties of coatings were evaluated by contact resistance tester and spectrophotometer. The results show that the coating has a dense surface， uniform thickness， good film-forming properties， good adhesion to the substrate （level 1），and excellent thermal control performance （α_s=0.19±0.02；ε_H=0.92±0.02），low resistivity ［（3.0-18.0）×10⁵ Ω•m］，and excellent space environment adaptability，which has great application prospects in the field of spacecraft anti-static thermal control.

Abstract:The deposition of copper layers on polyimide films by magnetron sputtering is widely used in the preparation of flexible copper-clad laminates. At present， low bonding strength between the surface copper film and the polyimide substrate is one of the main problems faced by the magnetron sputtering method in the preparation of flexible copper-clad laminates. This paper proposes to improve the adhesion of copper film on the surface by plasma etching treatment of polyimide substrate and introducing a metal Cr bonding layer. It also compares and studies the effects of different plasma etching and metal Cr layers on the microstructure， density， resistivity， and adhesion of the surface copper film. The results show that plasma etching increases the surface roughness and surface energy of polyimide， which is beneficial for copper film deposition and forms mechanical interlocking and chemical bonds at the interface to improve adhesion. The Cr metal intermediate layer can form a solid solution at the film interface to strengthen the adhesion， reaching the optimal 5B level. This study is of great significance in solving the problem of poor adhesion between copper film and polyimide substrate in the preparation of flexible copper-clad laminates by magnetron sputtering.

Abstract:The flow rate of N₂ had a significant impact on the structure and performance of CrAlYN coatings， so this study systematically investigated the influence of N₂ flow rate on the structure， mechanical properties， and thermal stability of CrAlYN coatings. The results show that as the N₂ flow rate increases from 23 mL/min to 38 mL/min， the nitrogen content in the coating increases from 26.45 at.% to 52.20 at.%. When the N₂ flow rate is 33 mL/min， the nitrogen content in the coating is 49.00 at.%， and the elemental composition conforms to the stoichiometric ratio. The coating has the highest hardness and resistance to plastic deformation. XRD and TEM analyses show that coatings with low N₂ flow rate has a nanocrystalline structure and lower hardness. The coatings with high N₂ flow rate has a columnar crystal structure， and the injection of nitrogen atoms increases the compressive stress of the coating and reduces its hardness. The coating with a N₂ flow rate of 33 mL/min has smaller grains and a dense structure， with a hardness of 24.6 GPa. After annealing at 1 000 °C， the coating shows slight oxidation and a hardness of 18.4 GPa， which is higher than that of coatings with other N₂ flow rates， indicating that this CrAlYN coating has the best overall performance.

Abstract:In the actual processing procedure， multi-step processing was commonly used to optimize the hole-making quality of carbon fiber-reinforced plastic （CFRP）. However， there was still a lack of detailed analysis on the formation mechanism of the cutting surface in multi-step processing. To address this issue， this paper constructed a secondary cutting simulation model for four typical fiber orientations （θ = 0°， 45°， 90°， 135°）， and explored the formation mechanism of the cutting surface and the evolution pattern of cutting damage during the secondary cutting process. The results show that with the increase of the spindle speed n， the secondary cutting force exhibits a significant downward trend； while an increase in the feed rate V_f leads to a significant rise in the secondary cutting force. Further analysis reveals that when the fiber orientation θ is 0°， the influence of the cutting surface damage from the first cutting on the second cutting is relatively small. However， when the fiber orientation θ is 45°， 90°or 135°， under the condition that the second cutting thickness is less than the depth of the fiber damage layer caused by the first cutting， the second cutting can effectively remove the damage layer generated by the first cutting without causing new fiber damage， thus significantly improving the quality of the cutting surface.

Abstract:Cutting tools of titanium alloys are subject to severe wear due to its chemical activity and high cutting temperatures. Applying coatings to the tool surface is an effective way to extend tool service time. Using PVD cathodic arc evaporation technology， the TiAlSiN/CrAlSiN nano-multilayer coating tool was made by alternately superposing TiAlSi target and CrAlSi target， which are used to cut conventional titanium alloy and 3D printed titanium alloy， respectively. The obtained TiAlSiN/CrAlSiN nanomultilayer coatings exhibit high hardness. When cutting titanium alloys， the tool wear is characterized by coating delamination， craters on the rake face， uniform wear on flank face， and chipping on tool nose. The main cause of tool wear is adhesion， followed by high temperature oxidation. Among the three cutting parameters， the effect of cutting speed on cutting force and cutting temperature is much greater than that of depth of cut and feed. Compared with conventional TC4， the cutting temperature and cutting force of 3D printed TC4 are lower than those of conventional TC4 due to the decrease of elongation and hardness and the increase of elastic modulus， and the tool life is correspondingly prolonged.

Abstract:To explore the material removal characteristics of 2.5D C/SiC composite miling， end mills and fish-scale mills were used to perform conventional milling（CM） and ultrasonic vibration-assisted milling（UAM） on 2.5D C/SiC composites. The changing laws of cutting force and cutting temperature under four milling conditions were analyzed， and the removal characteristics of 0°， 90° and z-direction needle punched fibers were studied. The results show that， compared with traditional end mill and CM， fish-scale mills and UAM can significantly reduce cutting force and cutting temperature， respectively. UAM can change the overall removal of fibers into broken removal and reduce surface defects. The combined process of fish-scale mills and UAM can greatly reduce surface defects， cutting force and cutting temperature， improve the surface quality of the workpiece， and provide feasibility for low-damage milling of 2.5D C/SiC composites.

Abstract:The epoxy-polysiloxane copolymer （ES） was synthesized by condensation reaction of hydroxy-terminated polydimethylsiloxane （HTPDMS） and bisphenol A epoxy resin （CYD-128），and then blended with phenolic resin to modify and obtain polysiloxane modified epoxy/phenolic blend （ES/PF）.Thermal properties of ES/PF blend and the chemical structure and composition of pyrolysis residues at different temperatures were investigated by thermogravimetry-differential scanning calorimetry （TGA-DSC）， fourier transform infrared spectroscopy （FTIR）， scanning electron microscopy with energy dispersive spectrometer （SEM-EDS），and X-ray photoelectron spectroscopy （XPS）.The results show that， compared with pure phenolic resin， the residual yield of ES/PF blend increases by 438% at 800 ℃ in air atmosphere， and the maximum heat release rate decreases from 21.98 W/g to 14.93 W/g. However， under N₂ atmosphere， the residual yield decreases slightly by 14.3%.In addition， the hybrid structure rich in Si-O_x in the pyrolysis condensed phase of ES/PF blend system within 430-600 ℃ plays a key role in the stable formation of carbon layer， effectively delaying and inhibiting the further degradation of resin， and thus improving the carbon residue rate.When the temperature exceeds 430 ℃， the existing form of silicon element in the residue changes significantly，from SiO₂ （accounting for more than 80%） at 430 ℃ to hydrated silica （SiO₂·nH₂O） at 600 ℃. These results fully indicate that the silicon element can significantly improve the carbon residue and thermal stability of phenolic resin under thermal oxygen condition， but its influence is suppressed to a certain extent under N₂ conditions， which may be attributed to the oxygen absorption mechanism of siloxane groups during pyrolysis process. In addition， the structure and composition of pyrolysis residues of ES/PF blend system have a positive effect on improving the thermal residual strength and ablation resistance of the material.

Abstract:The silicon carbide ceramics were processed by pulsed laser.The influence of laser process parameters such as laser power， scanning times and spot overlap rate on the modified surface characteristics of the workpiece was investigated by single factor experiment.The experimental results show that when the laser power is small， the workpiece surface forms periodic undulation groove and broken pits are randomly distributed. When the laser power gradually increases， the workpiece surface gradually appears thermal cracks. The surface roughness first decreases and then increases with the increase of laser power.When the scanning times are low， the structure formed on the workpiece surface is shallow and loose.With the increase of laser scanning times， the structure formed on the workpiece surface is uneven.The surface roughness first decreases and then increases with the increase of scanning times. At low spot overlap rate，the workpiece surface groove is shallow and the overall surface undulation is weak. When the spot overlap rate increases，the surface grooves become deeper and the holes appear. The surface roughness increases with the increase of spot overlap rate.

Abstract:This paper summarizes the development process， latest progress and research status of long-term storage technology forfilled liquid submarine-launched ballistic missiles. The structural design， material selection and manufacturing technology of Russian liquid submarine-launched ballistic missile， as well as the ex-factory fueling， packaging and sealing test methods are emphatically introduced. Finally， the technical path to achieve long-term filling and storage is pointed out.