Abstract:

In order to draw upon and refer to the experience in the development of composite fan blades abroad，the application progress of composite fan blades in commercial aviation engines is deeply studied，and the three development stages of composite fan blades from early exploration to mature application，and then to future prospects are discussed in detail.By introducing three core manufacturing technologies adopted by three overseas original equipment manufacturers （OEMs） of aviation engines—namely，the process of manual placement of prepregs combined with autoclave curing and molding，the 3D-woven structure with resin transfer molding （RTM）， and the process of automated fiber placement of prepregs combined with autoclave curing and molding—this paper compares and analyzes the characteristics of these three preform manufacturing technologies.This paper comprehensively presents the production processes，manufacturing key points，and future development directions of composite fan blades.Facts show that composite fan blades have become a prominent feature of modern commercial aviation engines and are essential for the development of advanced aviation engines.Therefore，domestic research and development units should actively absorb the accumulated foreign experience in research and development，fully utilize the favorable opportunities provided by national development，and deeply explore and practice more material systems and process engineering details，aiming to achieve the early expansion of domestic applications of composite fan blades，thereby further enhancing the performance level of China''s aviation engines.

Abstract:

This article reviews the development history of 7000-series ultra-high strength aluminum alloys both domestically and internationally，and briefly outlines several application examples of typical aluminum alloys in China''s carrier rockets.Based on the current status of engineering applications of 7000-series aluminum alloys in China''s aerospace structural systems，this article analyzes the existing problems and accordingly proposes research directions and relevant suggestions that are worth paying attention to.

Abstract:

The preparation methods of nlyon thermoplastic composite mainly include hot-melt prepreg method and in-situ polymerization method.Compared to the in-situ polymerization method， the hot-melt prepreg method always has higher cost and lower efficiency in producing composites.In reponse to the urgent demand for efficient and low-cost manufacturing of nlyon thermoplastic composite，this article takes fiber reinforced nylon 6 composites as the research object，summarizes the research progress of in-situ polymerization methods for preparing nylon 6 thermoplastic composites，including casting，centrifugation and rotation，pultrusion，and liquid molding.It focuses on the liquid molding process of this thermoplastic composite and briefly describes its development direction.

Abstract:

Based on the curing mechanism of bismaleimide resin，dynamic in-situ curing programs were developed to simulate the pre-polymerization and crosslinking of bismaleimide，a two steps method was used to construct a molecular dynamic （MD） model of high temperature resistant bismaleimide resin，and predictions were made regarding its model structure，thermomechanical properties，and resin stiffness.The curing reaction conversion rate and the density of the curing model during the pre-polymerization and crosslinking process of bismaleimide resin are consistent with the actual values，proving that the dynamic in-situ curing program achieves the curing program achieved the curing reaction of the experimental process.Meanwhile，during the simulated curing process from resin precursor to per-polymer to crosslinked model，the resin model gradually transitions from a high-viscosity liquid state to a high-density network structure solid polymer state，verifying the rationality of the curing program.The predicted glass transition temperature and Yong’s modulus based on the density，volume change rate，and elastic stiffness matrix of the bismaleimide resin curing model are close to the experimental results，confirming the reliability of the this bismaleimide resin model and its suitability for the bismaleimide resin system.

Abstract:

ZN-37 special damping silicone rubber is a viscous damping material capable of dissipating and storing vibrational energy，and is widely used in high-precsion vibration damping structures in aerospace and other fields.When analyzing and designing vibration reduction structures based on ZN-37 special damping silicone rubber，it is particularly crucial to fully characterize the viscoelastic mechanical behavior of the material and accurately describe its constitutive relationship.Based on the Zener modified model， the visco-hyperelastic constitutive model of ZN-37 special damping silicone rubber is decomposed into a parallel coupling system of the hyperelastic constitutive model and the viscoelastic constitutive model.Material parameters for the constitutive model are obtained through quasi-static tensile tests and stress relaxation tests on standard specimens.The reliability of the constitutive model is verified using quasi-static tensile tests conducted at different loading rates.The established visco-hyperelastic constitutive model can effectively reflect the mechanical properties of ZN-37 special damping silicone rubber at low loading rates.

Abstract:

Existing image quality evaluation methods mainly focused on noise， clarity and other indicators，and lacked the comprehensive evaluation of the quality of the areas of concern in the weld region，defect region and image quality indicators region in the digitised image of the radiographic negative.To address the above problems，a comprehensive radiographic image quality evaluation technique that integrated multi-region quality features was proposed.Firstly， a set of evaluation index system covering multiple regions such as image quality indicators，weld seam and defects was constructed by combining the quality evaluation needs in the field of non-destructive testing；then，a comprehensive radiographic image quality evaluation method including the number of image quality indicators，clarity，contrast，information entropy and average greyness was proposed on the basis of hierarchical analysis method.The experimental results show that the proposed method can achieve the comprehensive evaluation of the digital image quality of the X-ray negative，which can quantitatively evaluate the overall image quality and also ensure the good quality of the image in the concerned area.

Abstract:

The construction of a lunar base faces harsh environmental conditions such as high vacuum，strong radiation， and extreme temperatures，as well as resource constraints，which holds significant scientific research value.In response to the construction requirements of future lunar research stations，this paper adopts a construction approach that combines upstream resources brought from the earth and in-situ resources available on the moon.And the lunar base configuration，architectural components，equipments，energy sources，and construction methods are investigated，the preliminary validation of the formability and fundamental performance are conducted.For the construction of the buildings and their outer enclosure structures， a novel technical method is proposed by utilizing inflatable membranes， 3D printed lunar regolith bricks and lunar regolith bags，corresponding lunar regolith bricks with mortice and tenon structure as well as sandwich structure lunar regolith bags with arch axis are designed.The results indicate that the lunar regolith bags produced through internal tension and external constraint can withstand a load of 1 000 N，with a component size error of approximately 9.5%.The average compressive strength of 3D printed lunar regolith concrete is 31.6 MPa， and the average tensile strength is 2.0 MPa， reaching the strength level of C20 concrete. This lunar regolith 3D printing technology offers a potential pathway for the construction of lunar bases.

Abstract:

In order to improve the processing and mechanical properties of bismaleimide resin，eight novel types of bismaleimide monomers（hereinafter referred to as “bismaleimide monomers”） with structures containing rigid bisphenol fluorene（FDABMI），side group（PIDABMI），ether bond（34ODABMI），amide bond（34DABABMI and 33DABABMI），sulfone group（44DDSBMI and 33DDSBMI）and chain extension（BAPSBMI） were prepared，aiming to explore the structure-performance relationship of bismaleimide monomners with different structures.At the same time，diallyl bisphenol A（DABPA）was used as modifier to prepare bismaleimide resin by melting copolymeriazation with new type of bismaleimide monomers.The results show that the melting points of BAPSBMI and PIDABMI with extended chain structure and side methyl structure decreases significantly to 74 ℃ and 70 ℃，respectively.The glass transition temperature of the resin prepared by 33ODABMI and BDM is similar，about 250 ℃，while the bismaleimide resin prepared with the chain extension monomer BAPSBMI has the lowest T_g of 230°C. .The flexural modulus of 34ODABMI and 33DDSBMI are 4.1 MPa and 4.5 MPa，respectively，which are 14% and 25% higher than that of BDM.The results show that molecular structure design is closely related to performance， and the glass transition temperature of the resin is mainly related to the length of the bridging group in the bismaleimide monomer. The bismaleimide monomers with meta-substitution have higher flexural modulus.

Abstract:

In order to investigate the barrier properties of multi-layer moisture-proof composite plastic films against water vapor molecules， the diffusion and adsorption behavior of water vapor molecules in the composite films were studied by molecular dynamics simulation. And the permeability coefficient （the product of diffusion coefficient and solubility coefficient） of water vapor molecules in the composite films were obtained by using the parallel model. The results show that the diffusion coefficient of water vapor molecules in the composite films increase with the increase of temperature， while the solubility coefficient gradually decreases with the increase of temperature， and the permeability coefficient gradually increase with the increase of temperature. At the same time， polyvinylidene chloride（PVDC）exhibits the best water vapor barrier performance in the moisture-proof membranes， followed by polyethylene（PE）， and finally nylon 6（PA6）. Additionally， to study the aging resistance of the composite films， the chemical structure and thermal stability of the composite films under different aging times and relative humidities were studied by Fourier infrared spectroscopy， thermogravimetric analysis and differential scanning calorimetry. The results show that composite films exhibit excellent stability， with no significant changes in material properties.

Abstract:

A kind of anti-oxidation coating suitable for honeycomb-enhanced low-density thermal protection material was studied.The processing property，microstructure of surface，heat resistance of the anti-oxidation coating were investigated，and the ablative property was assessed by muffle furnace ablation test，plasma ablation test and radiation heating test.The results indicates that the solvent content of anti-oxidation coating should be in range from 25% to 75%，its pot-life is greater than 165 min and its thickness is less than 300 μm.The thermal stability of the phenolic resin STN-1 coating is better than that of the methylphenyl silicon rubber 218-1.After being exposed to 800 ℃/10 min，a relatively obvious ceramicization phenomenon occurs in the coating.Under the conditions of 1 MW/30 s and 1.5 MW/30 s，a hard and dense carbon layer is formed.Under the radiation heating environment of 2 000 ℃ for 300 s，the back surface temperature of the honeycomb-reinforced low-density heat resistance material with coating is reduced by 10 ℃，and the strength of the carbon layer is higher.

Abstract:

The perfluoroether rubber had excellent properties of resistance of high and low temperature as well as special medium.The 7804 grease was used as lubricant of perfluoroether rubber sealing material when applied in radial sealing.In this paper，the sealing performance of perfluoroether rubber sealing material in radial sealing was studied.The results show that perfluoroether rubber seal has low gas leakage rate.After 7804 grease coated on perfluoroether rubber sealing material for a period of time，some small particles from grease is generated，which can form micro-channel on the surface of rubber，results an increase on the leakage rate when tested by helium mass spectrometer leak detector.The use of liquid fluoroether raw rubber as lubricant can reduce the leakage rate effectively.The gas leakage rate of perfluoroether rubber sealing material coated with 7804 grease in oxidant and combustion agent medium is much lower than that in helium environment，which means that 7804 grease can be used as the lubricant of perfluoroether rubber sealing material in special medium environment.

Abstract:

The 3D packaged BGA devices used in aerospace had temperature limitations during the soldering process of printed circuit board assemblies，which were incompatible with the soldering temperature of other large-sized surface array devices （such as BGA， CCGA， LGA）.Therefore，temperature controlled soldering was required for the 3D BGA devices during the reflow soldering process.This article designed a reflow soldering temperature controlled soldering fixture for 3D packaged BGA devices，established a thermal simulation model，simulated the soldering process of the device during reflow soldering.Additionally，experiments were conducted on the reflow soldering process using the temperature controlled fixture to verify the accuracy of the simulation data.The results show that temperature control fixtures can effectively reduce device temperature，and the top of the fixture blocks the upper jet in the welding environment，which has the greatest impact on device temperature.The experimental results are consistent with the simulation results，proving that the simulation results are accurate and effective，and simulation methods can be used to reduce the experimental period.Microstructure analysis is conducted on the device after reflow soldering using fixtures.The solder joints of the device are intact，without obvious defects，and the internal state is good.The solder joints form a continuous scallop shaped interface layer，and the thickness of the IMC layer meet the requirements of aerospace standards.

Abstract:

The Mg-6Gd-3Y-0.5Zr magnesium alloy had been used in aerospace structural products，its internal damping performance was directly related to the dynamic characteristics and response of structures，the internal damping performance of Mg-6Gd-3Y-0.5Zr magnesium alloy was studied using DMA tester and the mechanism was analyzed.The results show that the damping of Mg-6Gd-3Y-0.5Zr alloy gradually increases with the increase of strain amplitude and the mechanism at temperature conforms to the G-L dislocation damping theory.The damping performance of alloy gradually increases with the increase of temperature.Within the tested frequency range of 1~80 Hz，the lower the frequency is， the more sensitive the damping is to the change of temperature，and the influence of temperature on damping performance conforms to the Schoeck theory.

Abstract:

In order to explore the effect of cryogenic treatment on the microstructure of different titanium alloys， three titanium alloys，TA7，TA6 and TC4，were immersed in liquid nitrogen tank （-196℃） for cryogenic treatment （DCT）.Electron microscopy （SEM） and X-ray diffractometry （XRD） were used to analyze the microstructure changes of titanium alloys before and after cryogenic treatment.XRD analysis results show that the intensity of the diffraction peak lines of TA7 and TC4 is significantly increased after cryogenic treatment，while the intensity of the diffraction peak lines of TB6 before and after the experiment is different，indicating that obvious lattice distortion occurs in the samples of TA7 and TC4.The lattice spacing of the three materials changes after the experiment， indicating a change in grain size.The SEM analysis results show that the cryogenic treatment can refine the microstructure of all three materials and enhance their density.Additionally， the number of precipitates in the TA7 and TC4 titanium alloys increases.Therefore，cryogenic treatment can effectively optimize the microstructure of titanium alloy.

Abstract:

In view of the unclear influence law of the curing temperature of phenolic resin on the mechanical properties of ablation-resistant thermal protection composites and the unclear strength variation law of resin carbon with temperature，the effects of curing temperature on the tensile modulus and tensile strength of phenolic resin were studied.The influence law of heat treatment temperature on the mechanical properties of resin carbon was investigated by Vickers microhardness.The results show that the tensile modulus of phenolic resin increases with the increase of curing temperature，and the tensile strength tends to increase with the increase of curing temperature.The maximum tensile modulus is 5.04 GPa，and the maximum tensile strength is 89.8 MPa.The highest curing temperature of the resin should not be lower than 140 ℃.The strength of resin carbon increases with the increase of heat treatment temperature， and the strength of resin carbon layer is the highest at 1 100 ℃.This provides beneficial guidance and assistance for the design and preparation of phenolic resin-based ablation-resistant composites.

Abstract:

The aging failure mechanism of isotropic conductive adhesive under high temperature and humidity was studied. The microstructure of the material before and after aging was characterized by scanning electron microscope （SEM）， electrochemical impedance spectroscopy（EIS） and X-ray photoelectron spectroscopy（XPS）. The results show that under high temperature and high humidity， due to the post-curing shrinkage of the adhesive， the decrease in the bonding interface strength， and the difference in the thermal expansion coefficient with the bonded material， microcracks are generated at the bonding interface and expand with time. Under the same aging temperature and aging time， the presence of humidity promotes the formation and expansion of microcracks at the bonding interface. XPS results show that after aging under high temperature and high humidity， the proportion of "inorganic silicon" on the surface of the sample significantly increases.

Abstract:

For the two types of domestic T800-grade carbon fibers，which T800 made by wet spinning and SYT55 made by dry-jet wet spinning，the microstructure of the carbon fibers was characterized by using a scanning electron microscope.Both types of carbon fibers were combined with bismaleimide resin 802 to prepare hot-melt prepreg and carbon fiber/bismaleimide composites.The tensile，compressive，and shear mechanical properties，as well as the microscopic failure morphology，were tested and analyzed.The results show that the surface of SYT55 fiber is smooth， and its carbon fiber/bismaleimide resin composite has higher tensile strength and good high-temperature mechanical properties.The TG800 fiber composite has higher interfacial strength.

Abstract:

The finite element analysis of GH4169 alloy O-ring for a tank container of spacecraft was carried out by ABAQUS software， and the effects of different compression ratios， sizes， coating factors on the resilience and sealing performance of O-ring were discussed. The results show that the compression ratio is an important factor affecting the resilience characteristics， and the resilience amounts and resilience rates of the O-ring are quite different under different compression ratios. The contact performance such as contact stress is greatly influenced by the O-ring structure sizes （outer diameter， wall thickness）. The coating helps to increase the width of the contact surface， but the contact stress will decrease. Therefore， the selection of the sealing ring needs to comprehensively take the compression， the structure size， the coating and other factors into consideration in the flange sealing design.