Abstract:In this papaer,the recent developments of organic-inorganic hybrid polyimides and their composites were reviewed. The preparation of organic-inorganic hybrid polyimides containing polyhedral oligomeric silsesquioxane and siloxane structures were introduced. Their heat resistance and thermal-oxidative stability correlated with chemical structures were analyzed and summarized. The application and future development of organic-inorganic hybrid polyimide resins and their composites are also prospected.

Abstract:The combustion degradation process of rigid polyurethane foam, the flame retardant mechanisms of flame retardant and the common flame retardants for rigid polyurethane foams were reviewed. The latest development of flame retardants in the rigid polyurethane foam was summarized. The synergistic effects of addition-type flame retardants and between addition-type and reactive-type flame retardants were also emphasized.The future development prospect of flame retardants in the rigid polyurethane foams was elaborated.

Abstract:The process characteristics of prepregs-based vacuum-bag-only consolidation are reviewed, including resin manufacturability, prepreg architecture and moulding process. Its application in aeronautics and astronautics areas has been briefly introduced, meanwhile its current state and trends are discussed at the end of this article.

Abstract:Factors affecting the thermal expansion coefficient of composite is of guiding significance for the design of thermal expansion coefficient of composite. The influence factors of thermal expansion coefficient of composite, such as fiber resin system, layer order, layer angle deviation and fiber volume content, are studied and the conclusions are given in this paper. The thermal expansion performance of the same matrix varies greatly, and the different matrix has a great influence on the thermal expansion coefficient of the same fiber. The outer layer of the 0° layer will help to reduce the axial thermal expansion coefficient, and will also contribute to the increase of the radial thermal expansion coefficient; the layer angle is from 30° to 60°, The deviation of thermal expansion coefficient caused by angle deviation is large. The axial thermal expansion coefficient of the composite tube and the volume content of the fiber showes a high nonlinear and non monotone, and the radial thermal expansion coefficient showes a monotonous decrease.

Abstract:In this paper, the welding residual stress of metal shell fillet welds which are fabricated by super strength steel is simulated during welding and heat treatment process. Finite element simulation is performed by ANSYS code. The results show that the residual stress is concentrated in heat affected zone of support fillet welds. The peak stress increases with the number of spport fillet welds increaseing. In order to improve the performance of these metal shells, heat treatments (annealing and tempering) are used. It is revealed that the welding residual stress in the fillet welds decreases and redistribs after heat treatments.

Abstract:Based on ABAQUS finite element analysis software, a two-dimensional axisymmetric model of TC4 titanium alloy inertial friction welding (IFW) process was established.The thermal coupling analysis of TC4 titanium alloy by inertial friction welding was carried out by establishing Johnson-Cook damage model and ALE technique.It was found that TC4 inertial friction welding increased to about 200℃ to 300℃ in 0.2 s, up to 1 100 to 1 200℃ in 0.5 s and then reached to a flatten.After reaching the peak, the temperature droped slowly and the welding were completed. The axial shortening is very small within 0.6 s, and it increases very fast and reaches a peak substantially at temperatures of 1 100 to 1 200℃ (0.6 to 1.2 s),from 1.2 to 1.4 s axial shortening increases slowly due to cementation.The temperature no longer increases after 1.4 s, and the welding is completed and the axial shortening is no longer increased. The initial stage of axial stress basically unchanged, with increasing temperature (0.2 to 0.5 s) compressive stress increases in the central region. The stress concentration in the center is more obvious, after 1.2 s tensile stress increases significantly. The radial stress increases with temperature,center stress was significantly higher than the outside and the metal flow to both sides. This leads to the result that the flash formation is mainly due to the complicated effect of high temperature, axial stress and radial stress. The simulation results are basically consistent with the actual results, which can provide an important reference for improving the welding quality of inertial friction welding.

Abstract:The setting of micro resistance spot welding parameters plays an important role in the shear force and peel force, through the range analysis of orthogonal test and the influence of process parameters on the shear force and peel force of thickness of 0.05 mm foil TC1 resistance spot welding was investigetal. By giving the corresponding values of shear force and peeling force, the bi-objective optimization is transformed into a single hybrid objective optimization, BP neural network and genetic algorithm are combined to optimize the process parameters. A prediction model of the mechanical properties of solder joints based on BP neural network is established.The prediction results show that the error is less than 4%, indicating that the network model has higher prediction accuracy and ability.It can predict the mechanical properties of solder joints accurately. At the same time, with the global optimization ability of genetic algorithm, the parameters of spot welding are optimized, and the optimum combination of welding parameters is obtained:welding current 800 A, electrode pressure 8.89 N, ramping time 1.608 ms, welding time 8 ms, hybrid target force value 55.73 N. By comparing the results of orthogonal test, genetic algorithm optimization can get better comprehensive mechanical performance.

Abstract:The assembly mode of composite case is hand crossed positioning method. It's low precision, poor repeatability, high level requirements for the operators and using the metal marking needle can cause surface damage of the composite shell. In order to change the status of hand crossed positioning, the method of NC equipment combined with the spraying equipment for the parts positioning was proposed. For making sure the accuracy of parts contour and position, equidistant spraying was researched. NC positioning trajectory equating was built. Through connecting spraying equipment with CNC system to build up NC positioning system for parts. The contour and position of parts on composite case was marked. The positioning accuracy of parts can reach ±0.1mm, NC positioning replacing handicraft method was realized. The technology improves the positioning accuracy and consistency of parts in composite case.

Abstract:A coating constituted of MoSi₂ and melted glass with the high emittance was prepared. The effects of the coating on the microstructure and performances of the rigid tiles were investigated. The results indicated that thewaterproof coating was dense with an emittance of about 0.85. After coating process, the flexural strength and shore hardness of the rigid tiles increased. The tensile strength in transverse orientation was about 50% of that without coating. The back side temperature of rigid tiles with coating was higer than that without coating, when rigid tile was exposed to the radiation heat. However, the back side temperature of rigid tiles with coating was lower than that without coating, when rigid tile was exposed to the simulative heat of re-entry. The rigid tiles with coating created a little hole after the chip attack.

Abstract:The effects of selection of mold materials, processing of assembly and machining on the manufacturing of high precision CFC-made secondary reflector antenna were analyzed through researching the key assembly techniques, compared mold material, optimized assembly process and machining verification experiment.The results show that invar is an ideal mold material for the manufacturing of high precision CFC-made secondary reflector antenna. When the sandwich structure is assembled, adopting the in situ assembly technique for the external covering and individual adoption of the cellular around transitional region of the antenna covering can effectively avoid the poor surface accuracy of the antenna. A comprehensive application of an auxiliary mould for the machining and the 3D image measurement system can effectively ensure the high positional accuracy of the assembly reference point and significantly shorten the manufacturing period of the antenna.

Abstract:Composite case made of brittle T800HB carbon fiber is sensitive to stress concentration, and easily cause case dome failure at low pressure. In order to overcome redundant mass of longitudinal layer of cylinder section induced by traditional carbon cloth and UD cloth reinforcement,isostrength reinforcement method is used. Φ150 mm pressure case is treated as study object, stress equilibrium factor in processing design of composite case is referred, and composite thickness in quantitative isostrength reinforcement is concluded by comparison about strain result and experiment result. As a result, quantitative isostrength reinforcement is practicable and reliable.Burst pressure of T800HB carbon fiber case using isostrength reinforcement method totally achieves design value, and longitudinal layer strength in cylinder is not redundant. The method can increase PV/W of case,especially high length-to-diameter ratio case.

Abstract:2219C10S aluminum alloy welded joints were obtained by stationary shoulder friction stir welding (SSFSW). The paper presented the typical macroscopic and microstructural characteristics of welded joints, the influences of welding parameters on the forming characteristics and the mechanical properties of welded joints. The results showed that as compared with the traditional friction stir welding (C-FSW), flash and the defects of the weld could be effectively avoided during welding due to the structural characteristics of the stationary shoulder mixing head. With the increase of welding speed, the joint nuclear changed from "bowl" to "waist drum", and the volume decreased, and the welded joint was also specially characterized with the shoulder-affected zone. The microhardness distribution of the welded joints presented a unique "∪" shape, and the nuclear was the lowest. With the increase of welding speed which was under 250 mm/min, structure property increased; when welding speed reached to 300 mm/min, the structure property fell sharply.

Abstract:The 2219C10S aluminium alloy is first subjected to self-reacting friction stir welding, followed by TIG welding in the direction perpendicular to the friction stir welding, and then the cross-weld joint is made. In this paper the microstructure and mechanical properties of the cross-welded joint and TIG joint are comparatively analyzed. The microstructural characteristics of the two kinds of joints present similarities and differences. The similarities are that the weld zone of the two kinds of joints are all composed of the column section by the direct helium arc welding and the bowl area by AC pulse argon arc welding. The differences are that both the parent metal zones respectively are the small isometric grains and rolling plate strip grains, and the heat affected zones are coarsening on the basis of the parent metal zone. Microhardness test results show that the micohardness distribution trend of the two kinds of joints is "W" type, and the microhardness distribution gradient of the TIG joints is greater than that of the cross joint which has a relatively narrower softened area. Tensile test results reveal that two types of joints are broken in the heat affected zone. The tensile strength factor of the cross joint in the SR-FSW direction is 66.14% which is slightly lower than the TIG joints, while the elongation rate of the former is about 30% higher than that of the latter. The fracture surface of the cross joint is typically ductile fracture, and the TIG joint has some brittle fracture characteristics besides the ductile fracture characteristics.

Abstract:T-joints of TC4 and TA15 titanium alloys have been welded by continuous wave laser beam.The effect of weld parameters on weld appearance and shearing resistance of the joints have been analyzed using metalloscope and tensile testing machine. The experimental results showed that when other parameters were fixed, the weld width and depth of skeleton was improved with the increase of laser beam power and decrease of weld speed. The weld width of skeleton was the determining parameter of shearing resistance of laser welding T-joints. With the laser beam power over 4.1 kW, weld speed less than 80 mm/s and defocusing amount between -5 and +10 mm, the weld depth of skeleton reached 0.51 mm, the shearing resistance of the joints reached 14 kN.

Abstract:Delamination and fuzzing defects during drilling of KFRP composites are too severe to meet the requirements in assembling process. Therefore, orbital drilling is proposed to drill KFRP composites in this study. Single factor experiments are conducted to investigate the hole quality and inhabitation mechanisms in different working conditions. Delamination factor, fuzzing area and diameter deviation are presented to characterize the hole quality. The experimental results indicate that there are close influences of eccentricity, spindle speed and cutter geometry on hole quality. When four-flute end mill with waved edges is used, hole quality is the best in working condition of e=0.5 mm and N=4 000 r/min. The delamination factor and diameter deviation are 1.27 and 1.2% respectively, and reduction of fuzzing area from drilling with two-flute end mill is 13.7%.

Abstract:Through analyzing material removal mechanism of rotary ultrasonic machining, a model of machining efficiency is established and the processing parameters in the model are discussed in this article. By comparing four different materials inclding PZT piezoelectric ceramics, organic glass, glass steel and red cooper on single ultrasonic and rotary ultrasonic machining testing, the machining stabilization and efficiency of rotary ultrasonic are studied.The tests prove that rotation can significantly improve ultrasonic machining efficiency and keep the original precision.

Abstract:For the PGA package device leads in the assembly process is too short, the short-lead PGA is tested by selective wave soldering after analyzing the three main welding methods to optimize the welding process parameters, and the welding quality is discussed by looking at the appearance, X-ray and metallographic. The conclusion can be made that after visual inspection and X-rays inspection, no obvious solder joints defects are found in the short-lead PGA solder joints by selective wave soldering.The metallographic map of the solder joints show good welding at the joint,and meet the requirements of qualified intermetallic compound thickness. The selective wave soldering process method can realize short-lead PGA welding and has certain application value.

Abstract:When coin-tap method is applied to test honeycomb bonding structure, the detection sensitivity is reduced due to the increase of the skin thickness. To overcome this shortcoming, this paper designs a set of detection system consisting of computer, scanning mechanism and percussion hammer. The work improves the detection sensitivity and reliability of the product by combining the automatic control technology and C-scanning display technology. To verify system testing effects, artificial defects were designed. Experimental results are then presented which show good quantitative agreement with the artificial defects. As a result, the system is suitable for the product testing and beneficial to the objective evaluation of product quality.

Abstract:In this paper, aramid paper honeycomb preparation process is briefly introduced.Combining with aramid paper honeycomb preparation process,the causes of common appearance defects such as Doublewall thickness, Nested cells, S-sells and Herringbone patterns are analyzed, and some concrete measures to reduce honeycomb defects were proposed. It is recommended that researchers evaluate the effect of aramid paper honeycomb appearance defects on their performance and determine the acceptable range of defects.