Analysis on the Bonding Failure Mechanism of High Modulus Carbon Fiber Composites

In order to explore the bonding failure mechanism of high modulus carbon fiber composite materials, the tensile experiment and finite element numerical simulation for single-lap and bevel-lap joints of unidirectional laminates are carried out, and the stress distributions, the failure modes, and the damage contours are analyzed. The analysis shows that the main reason for the failure of the single-lap joint is that the stress concentration of the ply adjacent to the adhesive layer is serious owing to the modulus difference, and the stress cannot be effectively transmitted along the thickness direction of the laminate. When the tensile stress of the ply exceeds its ultimate strength in the loading process, the surface fiber will fail. Compared with the single-lap joint, the bevel-lap joint optimizes the stress transfer path along the thickness direction, allows each layer of the laminate to share the load, avoids the stress concentration of the surface layer, and improves the bearing capacity of the bevel-lap joint. The improved bearing capacity of the bevel-lap joint is twice as much as that of the single-lap joint. The research in this paper provides a new idea for the subsequent study of mechanical properties of adhesively bonded composite materials.     

Linear Shaped Charge Cutting Property and Charge Cutting Mechanism of Mg-Gd-Y-Zn Alloy

The linear shaped charge cutting technology is an effective technology for aircraft separation. It can separate invalid components from aircrafts timely to achieve light-weight. Magnesium alloy is the lightest metal material, and can be used to cast effective light-weight components of an aircraft construction. However, the application study of the linear shaped charge cutting technology on magnesium alloy components is basically blank. In response to the demand for the linear separation of magnesium alloys, the Mg-12Gd-0.5Y-0.4Zn alloy is selected to carry out the target shaped charge cutting test. The effects of the shaped charge line density, cutting thickness, and mechanical properties on the cutting performance of the alloy are studied. The shaped charge cutting mechanism is analyzed through the notch structure. The results show that the linear shaped charge cutting performance is significantly affected by the penetration and the collapse. The higher the linear density is, the stronger the ability of the linear shaped charge cutter is, and the greater the penetration depth is, which is advantageous. However, the target structure will be damaged when it is too large (e.g., 4.5 g?m-1). Within 12 mm, when the cutting thickness of the target increases, the penetration depth increases. The lower the tensile strength is, the greater the penetration depth is, and the more conducive the penetration depth to the shaped charge cutting is. When the elongation (EL) increases to 12%, the collapse of the target is incomplete and the target cannot be separated. When the tensile strength of the Mg-Gd-Y-Zn alloy is less than 350 MPa, the EL is less than 6.5%, the cutting thickness is less than 12 mm, and the linear shaped charge cutting of the magnesium alloy can be achieved stably.     

基于声波理论的氧输送系统低频脉动特性数值研究（英文）

Aiming at the low-frequency pressure fluctuation phenomena in certain liquid oxygen delivery systems during dual engine operation, a numerical study on the intrinsic frequency of the liquid oxygen delivery system was conducted by adopting an acoustic unit in Abaqus. Factors such as condensation characteristics of the oxygen-enriched gas gas in the liquid oxygen's pipeline between pumps, flexibility of the accumulator, and cavitation flexibility of the engine were considered in the simulation models. The simulation results show that the second order frequency of the liquid oxygen delivery system is 8.77 Hz, and the phase difference of the corresponding acoustic modal is 180°, which is the liquid circuit frequency of the small loop between the two branches of the tee. This is consistent with the low-frequency fluctuation phenomenon during flight. Moreover, the simulation results were consistent with the liquid circuit frequency solved via the transfer matrix, which also verified the effectiveness of the frequency analysis method based on acoustic theory.     

运载火箭自主动态轨迹优化控制的进展（英文）

This paper first introduces the technical requirements for autonomous flight, with a brief review of the International Academy of Astronautics(IAA) study group, “autonomous dynamic trajectory optimization control of launch vehicle”. Two research scenarios, ascent rescue and powered descent, are compared from the viewpoint of optimal control. On this basis, the technologies on the autonomous trajectory planning and control under the thrust-drop failures in the ascending phase, and the autonomous guidance method during the powered landing for the recovery of the rockets are discussed respectively. For the ascending problem, the characteristics of different solutions, including the iterative guidance method(IGM)-based residual carrying capacity evaluation, the state-triggered indices(STI), the joint planning with the payload's performance, and the multiple graded optimization(MGO), are analyzed for comparison. For the landing problem, the challenges such as the feasible region reduction caused by high thrust weight ratio(HTWR) and the disturbance adaptability brought by the limited feasible region, are studied in detail, as well as the onboard planning demonstration flight in China are introduced. Finally, the foundations supporting the above methods are summarized, which play an important role in promoting the flight autonomy.     

LM-7 Begins Integrated Modal Test

<正>Recently,the first booster of the LM-7 rehearsal rocket entered the vibration tower of the Beijing Institute of Structural and Environmental Engineering located in Tianjin,marking the beginning of the LM-7 integrated modal test,which is the last large test before its maiden flight.In July,the modal test of the LM-7core stage completed at the Beijing Institute of Structural and Environmental Engineering with the hoisting out of the vibration tower of the core stage.Dur-     

Development and Prospects of China's Space Technology——Will China's space technology be brilliant again at the turn of the century?

For China,at the turn of the century,how to keep the position of the space power,how to stimulate the enthusiasm of the space technicians and how to keep pace with the world space technology,all of these questions lie ahead of the Chinese people.So we may say China's space industry now is in the key stage.If the space industry draws great attention from the central government and the people of the country,it will have a brilliant future in the 21st century.We should put our eyes on the 21st century and prepare to explore space resources.It is difficult for us to keep pace with the times if we do not explore space resources and try to earn "the money in space".     

The Description of the Open Model in College English Teaching

In order to solve the current problems in the college English teaching and meet the demands of the ＂College English Curriculum Requirements＂, the Open Model in College English teaching is proposed in the thesis. The thesis describes the model from the five components,     

Technological Level of the LM-3A Series Launch Vehicle Storage Tank Advanced

Through the support of the major technological project of CASC,the Aerospace Research Institute of Materials&Processing Technology shortened the construction period of storage tank thermal insulation structure by more than 30 days through improving the technological level of the thermal insulation structure of the third stage storage tanks of LM-3A series launch vehicle,which has largely improved the production capability,satisfying the needs for high-density launch missions.At the same time,the technological level for manufacturing the cryogenic thermal insulation has significantly im-     

The In-orbit Application of 25Nms Gyroscope Fills the Gap in Domestic Market

After the successful launch of Yaogan 14, the 25Nms control moment gyroscope onboard the Yaogan 14 satellite successfully finished the attitude maneuver commands to the satellite and operates in a normal state. The successful maiden use of the 25Nms gyroscope fills the gap in the field of small control moment gyroscopes in the     

FY-1 Satellite Monitoring Flood in Huaihe River

While the flood in the Huaihe River in July worried the whole nation, two FY-1 satellites hadbeen monitoring this area. With the help of FY-1 satellites, the policy-making body had obtained the information about the area and the flood process, getting ready for     

Lightweight Design of Spaceborne CFRP Rigid Antenna Reflector

In order to overcome the shortcoming of space-borne rigid antenna reflector made of carbon fiber reinforced plastic (CFRP) skins with aluminum honeycomb sandwich (SAHS) structure, a new type of full CFRP skin plus rib (SPR) structure ring-focused parabolic surface antenna reflector with the size of 2.5 m 1.9 m is designed. Under the condition that the original caliber, surface type, and interface remain unchanged, the main influence factors are designed and controlled. First, from the perspective of high stiffness, lightweight, and easy to form, a finite element simulation software is used to analyze and optimize the layout of the rib, the cross-sectional shape of the rib, the size of the rib, and the matching of the size and the coefficients of thermal expansion (CTEs) of the rib and the skin. Second, two structures are prepared by the autoclave molding process. Third, the weight and the surface precision root mean square (RMS) value are measured. The results show that the fundamental frequency of the SPR structure is 142.2 Hz, which is 3.5 Hz higher;the number of the new structural parts is reduced by 40%, and the forming process is greatly simplified. The total weight of the new structure is 11.9 kg, lighter 42.5%, indicating that the weight loss is obvious. The RMS value is 0.15 mm, which is slightly lower 0.01 mm but satisfies the accuracy requirement not greater than 0.3 mm. It is proved that the SPR structure reflector is a superior structure of the lightweight spaceborne antenna reflector.     

Technical Measures Preventingthe Disintegration of the LM-4'sUpper Stage in Orbit

Having successfully launched the FY-1 meteorological satellite, the upper stage of the 2nd LM-4 (A) launched vehicle disintegrated in its orbit on Oct. 4. 1990, and generated 81 fragments.After the analysis, we believed that the immediate cause of the disintegration of the LM-4 (A) 's upper stage is a slow leakage in the propulsion system , that leads to the damage of the common-bulkhead structure. This paper discusses the technical measures to preclude in-orbit fragmentation of the spent upper stage and introduces the design improvement measures of the LM-4's upper stage which are already in progress.     

LM-7 Prepares for Its Maiden Flight in 2016

<正>The LM-7 launch vehicle passed the joint review organized by CASC and CALT in June.Experts in the review team concluded that the LM-7 launch vehicle had completed the RD of the prototype phase and is able to enter flight test phase since the technical state of LM-7 for the flight test has been determined.The emphasis of the RD for the flight test phase will be put on the production,general assemble and test of the launch vehicle.     

Investigation on Thermal and Dimensional Stability of Epoxy Resin In-Situ Modified by Cyanate Ester Resin and Polydimethylsiloxane

The thermal and dimensional stability of epoxy resin (EP) in-situ modified by cyanate ester (CE) and polydimethylsiloxane (PDMS) are investigated by means of experiments and numerical simulation. Thermal gravimetric analysis (TGA) and differential scanning calorimeter (DSC) are used to analyze the heat resistance of the modified EP. The dimensional stability is characterized by the volume shrinkage of the series PDMS/CE/EP obtained by the density method. The chemical structure of the PDMS/CE/EP is analyzed by Fourier transform infrared spectroscopy (FTIR). The results of TGA and DSC indicate that the thermal stability of PDMS/CE/EP decreases firstly and then increases with the increase in the amount of CE. The addition of PDMS shows a slight effect on the thermal stability. The 40% CE makes the blending system exhibit the lowest initial decomposition temperature, which reduces by 15.5% and 40.8% compared with pure EP and CE, respectively. The FTIR results suggested that the influence of CE on the thermal stability of the modified EP is mainly ascribed to the generation of oxazolidinone ring with low thermal stability and the increase in the triazine ring with high thermal stability. The volume shrinkage measurement results show that the introduction of CE and PDMS are both beneficial to the improvement of the dimensional stability of the blending systems. The in-situ addition of 80% CE shows the lowest volume shrinkage of 6.11%. The thermal stress distribution of PDMS/CE/EP generated during the solidification process is simulated by the finite element analysis. The results suggested that the introduction of 80% CE into EP results in the lowest thermal stress in the blending system, which indicates that the system has the lowest volume shrinkage, which agrees well with the experimental results.     

Hydrogen Tank of LM-5 First Stage Passed Helium Mass Spectrum Leak Test

The hydrogen tank of LM-5 first stage passed the helium mass spectrum leak test recently, completing all the tests in the manufacturing phase and that the quality of products met the design requirement. The first-stage hydrogen tank is the largest one among all the tanks of LM-5, as well as the largest     

The New Pressurization System for the Upper Stage

The paper describes the new pressurization system for the upper stage of launch vehicles and spacecraft and the flight test results of the vehicle which conform to the design of the system.     

TaiYuan Satellite Launch Center

There are three major space launch bases in China, the Jiuquan Satellite Launch Center, the Taiyuan Satellite Launch Center and the Xichang Satellite Launch Center. All the three launch centers are located in sparsely populated areas where the terrain is even and the field of vision is broad. Security, transport conditions and the influence of the axial rotation of the Earth are all     

Study on the Deformation Behavior of Mg-Gd-Y-Zn-Mn Wrought Magnesium Alloys by Visco-plastic Self-consistent Modeling

The plastic deformation behavior of new Mg-Gd-Y-Zn-Mn magnesium alloys gains great necessity to clarify and understand the mechanism deeply. In the present work， the tensile mechanical property test and visco-plastic self-consistent (VPSC) model are used to investigate the activities of deformation modes of VW84M and VW94M magnesium alloys during the tensile deformation. The results show that the mechanical properties of the above extruded alloys are similar but VW94M has higher strength than VW84M after the same aging process. Compared with the extruded alloys， the as-aged alloys have significantly higher activation of pyramidal slip at the later stage of plastic deformation. In addition， the as-aged VW94M alloy with higher strength has the largest activity of pyramidal slip. In summary， the addition of Gd increases the critical resolved shear stress (CRSS) in each slip system of VW94M， while the increase in the strength and the decrease in the elongation of as-aged alloys are associated with the significant activation of pyramidal slip.     

An Improved Simplified Method of Amplifier Modeling Based on Compressed Sensing

An improved algorithm is proposed,which combines the advantages of Regularized Sparse Adaptive Matching Pursuit （RAMP） algorithm and Orthogonal Matching Pursuit （OMP） algorithm.By processing the two sets of atomic index from two algorithms,the intersection and complement sets are obtained,and the correct atom index in the intersection is contained with great probability.Optimizing the complement set by selecting the most correct atomic index from the complement set,we combine the most correct atomic index with the intersection to get the final index set.This method can reduce the probability of missing the correct atomic index greatly to get a more accurate reconstructed signal.Simulation results show that under the premise of high sparse level,the proposed algorithm can obtain high precision reconstructed signal,and the running time can also be reduced to a suitable level.     

Microstructure and Properties of Low-pressure Cold Sprayed Al-based Composite Coatings on Magnesium Alloy Surface

Pure Al and Al-30% Al2O3 composite coatings are prepared on the surface of AZ31B magnesium alloy by low-pressure cold spraying. The morphology and structure of the coatings are analyzed by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD), and the effects of the addition of Al2O3 on the microstructure of the Al-based coatings are discussed. The mechanical properties and corrosion resistance of the coatings are fully evaluated by the micro-hardness tester, electronic tensile machine, and electrochemical workstation. The results show that the coating structure is more uniform and denser, and the porosity is significantly reduced after the addition of Al2O3. The interfaces between the coatings and the magnesium alloy substrate are distinct, and the coatings and the substrate are mechanically combined. Compared with the pure Al coating, the microhardness of the Al-Al2O3 composite coating is increased to 61.1 HV0.2, and the bonding strength reaches above 53.1 MPa. The self-corrosion potential of the two coatings is higher than that of the magnesium alloy, and the self-corrosion current density is significantly lower than that of the magnesium alloy substrate. The Al-based coatings prepared by low-pressure cold spraying have high hardness, good bonding strength, and good corrosion resistance, which can be used for the repair and protection of magnesium alloy structural parts.