Abstract:Composites have been widely used among the developing process of spacecraft structures due to their outstanding performance. Based on the characteristic of spacecraft structures, the initial application, quick development, widely using and expanding applications have been reviewed in this paper. According to the future launching programing, the application trend of composites among spacecraft has also been illustrated.

Abstract:The process of solder joints on the gold-plated surface of Sn-Pb solder was widely used in aerospace electronics. The requirements of gold content in solder joints after welding in industrial documents and domestic and foreign standards were analyzed. The influences of solder gold content, aging and different packaging forms on reliability of solder joints were analyzed and the metallographic structure of solder joints was discussed. Finally, the requirements of de-golding and failure case of inadequate de-golding were introduced.

Abstract:In this paper, a double-pulse DC spot welding waveform was designed for DP590 high-strength steel, and the weld bonding process test was carried out. The mechanical properties of single-pulse and double-pulse weld bonding joints were compared and analyzed. In order to investigate the evolution of temperature field for double-pulse weld bonding joint, the weld bonding simulation models were established. The results show that the use of double pulse current can effectively reduce the generation of spatter and improve the stability of joints quality, and the mechanical properties of double-pulse weld bonding joints are better than that of single-pulse weld bonding. Furthermore, there are two growth processes in the nugget area of double-pulse weld bonding process. The thermal cycle curve exhibits “double peak” characteristics, and the thermal input of double-pulse weld bonding is higher than that of single-pulse weld bonding. The diameters of the double-pulse weld bonding joint from simulation and test are larger than that of the single-pulse weld bonding joint, and the nugget diameter of simulation is 6.42 mm and 5.97 mm, and the actual welding nugget diameter is 6.61 mm and 5.77 mm.

Abstract:Based on the secondary development of ABAQUS, the buckling properties of variable angle composite laminates with periodic function curves were explored. Firstly, taking the sinusoidal curve as the basic reference path the change law of the fiber angle was obtained; Secondly, the finite element analysis pre-processing program of variable angle composite laminates was written by Python and developed ABAQUS interactive interface.Finally, the buckling analysis of the classical fixed angle and variable angle laminates was carried out with using the GUI plug-in. The results show that that the buckling load of the variable angle laminates is obviously improved, and the first order linearity buckling is first increased and then decreased with the increases of amplitude parameter A and period parameter T, so considering the stability of the ply, the parameters should be controlled in the corresponding range. The secondary development of ABAQUS by Python is used to realize the automatic modeling and computational analysis, which provides research ideas and processes for practical engineering research, and has certain practical significance.

Abstract:In the process of purifying polysilicon by metallurgical method,the temperature control function and curve of annealing theory are explored by mathematical modeling of different annealing temperature schemes. The mathematical model shows that the silicon ingot is directly insulated, depending on the natural thermal equilibrium annealing, the internal stress is greater than the critical stress of generating dislocation. The top heater is used to heat the top of the silicon ingot to reduce the cooling rate. By comparison, a lower annealing temperature of 1236℃ and a shorter annealing time 8.52 ks is chosen as a reasonable theoretical annealing control scheme.The experimental results show that the annealing scheme has the advantages of less visual crack and a few carrier lifetime and resistivity.

Abstract:To explore the fabrication methods of high-performance thermoplastic composites, carbon fiber braided polyphenylene sulfide (CFF/PPS) thermoplastic composite laminates were fabricated by thin film lamination method. The effects of different forming pressure and temperature on the forming quality of CFF/PPS composite laminates were investigated by controlling variable method. The mechanical properties of CFF/PPS composite laminates with different processing parameters were characterized by bending test and interlaminar shear test, and the optimum range of two key parameters, forming pressure and preparation temperature, was determined without considering coupling effect. The results show that CFF/PPS composite laminates have the best properties when the forming pressure and temperature are 5 MPa and 340℃,respectively.

Abstract:Bismaleimide resin composites service as primary high temperature resistance load-carrying structure in aerospace crafts. Dynamic cure kinetics of highly reactived 802 bismaleimide resin was analyzed by differential scanning calorimetry, meanwhile its cure cycle was established as “150℃/1 h+180℃/2 h+200℃/4 h”. The T _g of 802 resin is up to 325℃ cured at 200℃, significantly superior to XU292 resin (234℃) with the same curing temperature. Furthermore, MT300/802 composite mechanical properties were investigated at room temperature, 230, 280 and 300℃, respectively. Its flexural strength retention capacity is 57% at 280℃, and the 300℃ flexural strength is as high as 1 094 MPa. Meanwhile, its interlaminar and in-plane shear strength also exhibits high properties level at both room temperature and high temperature. The results indicate that MT300/802 composite has the feature of “low temperature curing and high temperature usage”, which is suitable for aerospace primary structures.

Abstract:In order to improve the mechanical properties and ablation resistance of ultra-high temperature ceramic matrix composites, C/ZrC-SiC composites were fabricated by precursor infiltration and pyrolysis (PIP) process. Effects of the pyrolyzing process of zirconium silicon precursor resin on the properties of C/ZrC-SiC composites were investigated. The results showed that the pyrolyzing temperature of ZS precursor resin had great effects on the properties of composites. The mechanical properties decreased at high pyrolyzing temperature due to the damaging of carbon fiber while it also decreased at low pyrolyzing temperature due to high oxygen content. The prepared C/ZrC-SiC composites were tested by 2850 K arc wind tunnel test and the ablation rate was 8.75 ×10^-4 mm/s,which showed excellent ablation resistance.

Abstract:The excimer laser surface treatment technology was applied to the pretreatment of the carbon fiber composite bonding interface. The effects of surface treatment and post-treatment cleaning methods on the bonding strength and dispersion coefficient were studied by contrast test and microscope observation. The results show that the excimer laser surface pretreatment technology can significantly improve the bonding strength of the carbon fiber composite bonding interface, and there is not much difference in the bonding strength between the sandpaper grinding test piece and the excimer laser surface pretreatment piece.However, the adhesion strength of the test piece treated with the excimer laser showed relatively smaller coefficient of variation.

Abstract:Based on performance requirements, the wing of a light fixed-wing UAV(unmanned aerial vehicle)constructed by full carbon fiber reinforced epoxy is designed with features of light weight, high strength,high stiffness and maximum take-off structural mass of 10 kg. The three dimensional structure model of the wing is created based on aero-dynamic performance analysis and geometry design. The "closed rectangular cross-section caps" is adopted in the box-type wing spar, which increases the anti-twisting ability of the wing structure. The finite element model of the wing structure is established. Based on the strength criterion of maximum stress, the strength of the wing structure is checked. The stiffness and stability of the wing structure is also checked. It is show that stress concentration occurs in the wing root area of bolt holes, and the initial strength of the wing is determined by the stress state of this area. Buckling may occur on the spar cap section at the wing root and the skin around under bending load. The laminate structure of the skin is optimized. The weight of the wing skin decreases by 121.6 gram after optimization, about 11.94% of initial structural mass of the wing.

Abstract:The processing property and casting performance of the phenolic resin which can be used in RTM are studied. The rheological properties test, thermogravimetric analysis, oxyacetylene ablation test and other methods were used for characterization. The results show that the resin low viscosity platform (≤800 mPa·s) is long, and the applicable periods are more than 2 hours at 65~80℃.The char yield at 800℃ under N₂,line ablation rate and mass ablation rate of phenolic casting are 61.38%, 0.167 mm/s and 0.0654 g/s. The RTM phenolic resin is suitable for RTM technology and as matrix of ablative composites.

Abstract:In order to investigate the oxidation mechanism of solid propellant projectile on GH3044 alloy, the aperture in the GH3044 alloy lid was measured and analyzed by means of optical microscope, scanning electron microscope (SEM) and micro-hardness testing. The analysis results indicate that GH3044 alloy has endured a selective oxidation process along the grain boundaries at an oxidizing atmosphere, forming wedge-shaped inter-granular cracks. Therefore, an aperture in the lid was formed by the thermal stress as well as the metal oxide expansion stress. Moreover, the metal oxide (PbO) in the projectile reacted with the Ni-matrix, forming low-melting-point Pb-Ni eutectic, which is also supposed to be responsible to have accelerated the oxidation process.

Abstract:In order to study the mechanical properties of single crystal germanium at micro-nano scale, nanoindentation experiment was conducted on the Ge (100) (110) and (111) by using nanoindenter. Atomic force microscopy was applied to observe the surface of the material. Furthermore, the relationships between the elastic recovery rate, hardness, elastic modulus and indentation depth of germanium was analyzed according to the displacement-load curves of Ge(100) (110) and (111). Results show that elastic deformation, plastic deformation and brittle fracture occur in the loading process of single crystal germanium. When the indentation depth reaches 500 nm, there are pop-in points on the loading curve, while the pop-out points show up on the unloading curve when the indentation depth reaches 100 nm. Also, the pile-up behavior occurs in the residual indentation morphology of single crystal germanium, which demonstrate that single crystal germanium has a low tendency to work hardening. When the indentation depth reaches 100 nm, single crystal germanium shows an obvious size effect, and Ge(111)has the lowest hardness and elastic modulus, which shows that Ge (111) has the best plastic deformation ability relative to the other two crystal planes.

Abstract:The properties and characterization methods of silicon nitride fibers were investigated, including basic physical properties, diameter, tensile strength and dielectric property. The results indicated that the tensile strength of silicon nitride fibers after treating at 1500℃ was remained above 50% of the original fibers, and the dielectric constant was about 6.0. The results showed that silicon nitride fibers could be used for long time and elevated temperature application.

Abstract:RF thermal plasma(RFTP) had been utilized for synthetizing ultra-fine ZrC powders with different carbon sources, such as carbon black and methane. The products of the experiment were characterized by XRD, IR absorption, SEM, and chemical analysis. The results demonstrated that the ZrC powders which were less than 100 nm in the average diameter could be obtained with both carbon sources. However, methane played a better role than carbon black in the purity, the oxygen content and the productivity of ZrC powders. So, as a carbon source, methane was more applicable for batch preparation of ultra-fine ZrC powders.

Abstract:This paper introduces the homogeneity measurement method of dielectric material’s permittivity. According to the resonant perturbation and field analysis theory, a measurement model of double sections in a cylindrical cavity is established. A cylindrical cavity is designed at TM_0n0 to verify the feasibility of the measurement method and the measurement resolution. The measurement system that consists of vector network analyzer, computer, cylindrical cavity, and movement device is designed to realize the online and automatic measurement using the measurement software. Three typical samples are measured by using this system, whose measurement differences compared with the data from the manufacturer are less than 0.02, 0.04, and 0.15, respectively. These results are analyzed to prove the feasibility and effectiveness of the measurement system.

Abstract:This paper developed a novel method which involved binocular stereo vision to measure the model ablative pattern directly regarding the ablative pattern which was under testing in the arc heated wind tunnel. This method used the speckle correlation to process the data, combined sub-pixel correlation can make the results achieve very high precision. The real planar measuring results was obtained after the test was done on a flat model.The calibrate precision of the measure system is 0.02 mm. The results verified that this method can be useful for the analysis of the model characterize related with ablative time.

Abstract:To investigate the grinding removal mechanism of multispectral CVD zinc sulfide which is widely used in manufacturing infrared optical component, microscopic indentation and diamond single scratching experiment were carried out on polishing surface of zinc sulfide, and zinc sulfide was ground by diamond wheel. The elastic and plastic deformation were found in mechanical removal process of zinc sulfide. Crack and fracture were extended along the grain boundary, scratching direction, and grinding marks direction. And, crack initiation and propagation could be suppressed with lower press, lower crack and fracture would be obtained by cuspidal diamond abrasive. Besides, periodic and scattered grinding marks were found from center to edge by cross grinding. This work provides references and ideas for ultra-precision grinding aspheric lens of multi-spectral CVD zinc sulfide.