Abstract:In order to overcome the space service environments, a lot of work in material design, material processing, material evaluation and material usage had been carried out by the institute of development, guarantee and use of aerospace materials. Based on this, the selection demand of aerospace materials in China was analyzed firstly, and then some discrimination was given on the concept among aerospace materials, flight test of aerospace materials, space materials science, and space environmental adaptability of aerospace materials and so on. Furthermore,the concept of aerospace material engineering was put forward, and the correlation of related parts composition of aerospace material engineering is described. Finally, to meet the needs of the future development of space technology, based on the domestic and abroad development of aerospace material engineering experience, the aerospace material engineering system is constructed from planning, development, test (experiment), evaluation, data base, data service, standard and other aspects.

Abstract:The paper studied the effects of pin velocity,pin diameter,distance of forming trajectory and the width of peening strip corresponding to UPF on the formed arc height of stiffened plate by the orthogonal test.The optimal combination of UPF technological parameters can be obtained. Based on above-mentioned data as the sample data,the multiple regression analysis mathematical model was established.The accuracy of the mathematical model was proved by the sample.The experimental results agree well with the regression analysis data.The multiple regression analysis mathematical model can efficiently predict formed arc height in order to improve the efficiency of the process design.

Abstract:The surface modification of silver coated silica microsphere (SiO₂/Ag) was carried out by using excellent bonding properties of polydopamine (PDA) to improve the mechanical properties of conductive silicone rubber without affecting the conductivity of conductive silicone rubber. The results show that PDA surface modification can improve the dispersion of SiO₂/Ag in silicone rubber. By controlling the reaction time, controllable thickness of PDA layer can be achieved so that controlling the conductive silicon rubber conductivity can be achieved. The Payne's effect, loss angle of tangent (tanδ), optimum curing time (T₉₀), contact angle and tensile strength of conductive silicone rubber filled with modified SiO₂/Ag reach the optimum state when the PDA coating time is 8 h and electrical performance meets application standards.

Abstract:Taking the paving defects such as fiber wrinkling as the studying targets, the evolution of paving defects of composites during prepreg-autoclave process was studied, and the forming quality and mechanical properties after curing were compared and analyzed. The results showed that using a shorter prepreg during paving and a moderate curing pressure during curing was advantageous to improve the compliance of fibers and the smoothness of specimen, and the paving defects of fiber wrinkling can be effectively reduced. Under the conditions of this experiment, with the composite specimen length of 70mm and the curing pressure of 0.4MPa, the improvement effect of fiber wrinkling was relatively remarkable. In addition, the relatively high mechanical properties can be obtained after curing.

Abstract:Using PAN-based pre-oxidized fiber integral felt as reinforcement, the porous C/C preforms were fabricated by carbonization and isothermal CVI, and then C/C-Cu composites were manufactured by gas pressure infiltration technique which introduced copper into the porosity of C/C preforms. The ablative properties of C/C-Cu composites were tested by H₂-O₂ ablation method. The micro-morphology and constitutions in different ablative regions were analyzed by SEM and EDS. The results indicate that the ablative performance of C/C-Cu composites with 0.96g/cm³ density is excellent due to low linear and mass ablation rate. The ablative macro-morphology is composed of significant pit as central region in which the ablative mechanisms are oxidation of C/C preform and mechanical erosion of copper. Thermal oxidation and mechanical erosion of copper result in copper concentration in transition region, and black color surface in marginal region is due to oxidation of C/C preform. In order to improve the ablative performance of C/C-Cu, "pinning" effect of C/C preform should play an important role which can prevent copper from flowing by flame at high temperature.

Abstract:The aramid fiber(AF)and aramid pulp(AP) were incorporated into the rigid polyurethane foam(RPUF) and the influence of AF and AP dosage on the cell structure, compressive strength, thermal properties of the RPUF was investigated. The results show that compressive strength of the foams increased and then decreased with the contents of AF and AP. The compressive strength at the bottom of the foam reached the maximum value of 0.394 and 0.353MPa respectively when the adding contents of AF and AP was 6wt%,whose microstructure revealed finer and more homogeneous cell size distribution.The AF and AP dispersed and situated within the cellular skeleton of the foams,and it contributed to the property enhancement through forming a good adhesion with the resin. The addition of AF and AP was helpful for improving the thermal stability of the foam.AF reinforced foams showed superior thermal stability compared with AP.

Abstract:In order to prepare the composites with excellent electromagnetic shielding performance and mechanical properties, the carbon fiber modified phenolic carbon foam was prepared by high temperature carbonization with phenolic resin as matrix and carbon fiber as filler. The effects of carbon fiber content on the composite cell structure, electromagnetic shielding effectiveness and mechanical properties were investigated. The results show that the carbon fiber can improve the carbon foam cell structure effectively, when the content of carbon fiber is 3wt%, the phenolic foam matrix show smallest cell size and most uniform cells distribution, the average cell diameter is 150μm. Carbon fiber can effectively improve the carbon foam electromagnetic and mechanical properties.The compressive strength and flexural strength of the composites reach 4.41 and 3.85MPa, which has increased by 60.3% and 71.8%, respectively, compared with pure carbon foam.When the carbon fiber content is 5wt%, the average electromagnetic shielding effect of the carbon foam on the frequency of 8~12GHz is 35dB. When the carbon fiber content is 3wt%, the carbon foam composites show the best mchanical properties.

Abstract:In order to reduce the damage of the shock to the human body, a kind of shear thickening gel (STG) with buffering effect was prepared. The infrared and rheological properties of the shear thickening gel (STG) were studied. Foam (PU) was used to improve the impact resistance of foam, and the microstructure of polyurethane foam was observed by scanning electron microscopy. The results show that B atoms are successfully introduced into the siloxane chain and have obvious creep and shear thickening properties. STG has been uniformly attached to the bubble wall and significantly improved the impact resistance of the polyurethane foam. When the speed reaches 9m/s, the residual load of pure PU is about 3.6kN, the residual load of STG-PU is only about 1.7kN, and the reduction of residual load reaches 53%.

Abstract:Stable ZrC sol was prepared by sol-gel method using zirconium n-propoxide as zirconium source and sucrose as carbon source. Additionally, the effects of water content on micellar size, gelation time, phase composition and size of xerogel carbothermal reduction powder were also discussed in this paper. Meanwhile the carbothermal reduction process of xerogel with water content and C/Zr mole ratio were also studied. The results show that when C/Zr mole ratio is 7 and the volume ratio between acetic acid and water is 5, stable ZrC precursor can be prepared at room temperature, and the Zeta potential is about 18.7mV. The ZrC powder obtained by carbothermal reduction at 1700℃ has an average size of 240nm.

Abstract:Edge chipping of wave-transmitting ceramics in milling is prone to be presented, so the type, location of edge chipping has been investigated with different cutting depth experiments. The effect of cutting depth on edge chipping and the mechanism have also been analyzed. Finally, edge chipping control methods have been proposed. The results show that the edge chipping is mainly concentrated at the exit seamed edge and the entrance side edge of the milling tool when the depth is from 0.4mm to 0.8mm. With the increasing of cutting depth in brittle domain machining, the edge chipping is added. One way of controlling edge chipping is to reduce the cutting depth to no more than 0.3mm, another way is to using the tool path planning method of follow periphery, and ensure that the angle between speed direction and the feed direction is not less than 90°.The investigation provides technical support to improve the surface of the wave-transmitting Si₃N₄ ceramics in milling.

Abstract:Dissimilar joint between 2219-T87 and 2219-T852 alloys were produced by VPTIG. The weakened zone of the joint was determined by tensile test, and the weakening mechanism and fracture behavior of joints were discussed after observing of the grain size, element segregation and precipitates distribution. The results showed that the average ultimate tensile strength and elongation of VPTIG joints at -196℃reached up to 314 MPa and 5.68%, respectively. All joints were broken from the heat affected zone of 2219-T852 side, where showed the worst segregation of the Cu element, dissolving and coarsening of precipitates, non-uniform grain sizes, and the strain localization caused by the joint deformation. The fracture originated at the edge of the weld seam from the joint bottom surface, and propagated along the heat affected zone to the top surface, showed a mixed fracture mode.

Abstract:The ablation and thermal insulation performance of ZrO₂ thermal barrier coating with several different process under combustion conditions of the hydroxyl-terminated polybutadiene propellant was studied. By the orthogonal experiment, the primary and secondary relations between the influence factors (matrix-thickness, adhesive-layer type, surface-layer type and surface-layer thickness)with the ablation and thermal insulation performance of ZrO₂ thermal barrier coating were revealed. And the result of this work would provide a design basis for the application of ZrO₂ thermal barrier coatings to the field of solid rocket motors.

Abstract:The effects of moist heat environment, salt spray and mycete on nano Al₂O₃ thermal insulating materials were studied. The results showed that the thermal conductivity of materials with density of 0.45g/cm³ increased from 0.031 W/(m·K) to 0.047 W/(m·K) at 25℃ after moist heat test. The thermal conductivity of materials rapidly increased from 0.031 W/(m·K) to 0.136 W/(m·K) after salt spray test. The thermal conductivity of materials was kept constant after mycete test. The interaction between the material surface and the test environments was analyzed, and the technology of surface moisture resistence was developed at the material surface. After moisture resistence treatment, the hydrophobicity of the nano-alumina insulating material was significantly increased, the contact angle was more than 90°, and the properties of materials were not affected by moist heat environment, salt spray and mycete.

Abstract:The stiffness of the large composite beam is studied for the manipulator dynamic simulation. The 1st modal frequency and bending stiffness and turning stiffness are got by analysis and test. The test result does not coincide with analysis result. Reasons are put forwarded about the reduce of stiffness. Undesirable molding process and broken carbon fiber are the major factors to the stiffness reduce of composite beam.

Abstract:A measurement system of air coupled ultrasonic field is set up, and the field of 4 types of air coupled ultrasonic probe is detected. Composite specimens with embedded delamination are detected, effect of acoustic field on the detection results is analyzed. The results show that the low frequency and flat probe have high acoustic field energy and poor directivity, while the high frequency and focusing probe has low acoustic field energy, good directivity and high lateral resolution. The latter should be chosen as long as the penetration capability is guaranteed. Detection distance should be determined according to the acoustic field distribution. The detection sensitivity can be improved when the detected material is located in the focal region of the probe.

Abstract:The drilling process of CFRP and CFRP/Titanium stacks under various processing parmeters with twist drill was studied. And the process of drilling was simulated by using the finite element software Abaqus of 3d simulation module.Comparing critical thrust force and drilling hole quality of the simulation and test result, it shows that choose reasonable processing parameters under the premise of ensuring the quality of the hole, the optimum conclusions about processing parameters of drilling stacks materials can be obtained.

Abstract:Tool wear was studied using orthogonal experiment method while milling titanium alloy TB6 in different milling parameters. The flank face wear was measured by the photomicrograph after a certain period of milling during the milling process. The regression equation of TB6 tool wear was established by the experimental data. The experimental data indicated that the tool wear mainly occurred on the flank face and mostly showing a banded wear. The length of the band increases with the cutting speed increases. The brittle failure was occrured and the adhension of titanium was found on the tool face. The parameters effect on the tool life were cutting speed, feed speed, cutting width and cutting depth in turn. The regression equation has good regression variance and can predict the tool life well.

Abstract:The wear drilling experiment of the CFRP/TC4 was carried out by using the self-grinding tool and compared with the ordinary twist drill. The wear process of stepped drill was analyzed. The experimental results show that the main wear area of the stepped drill is chisel edge, the first flank face and the second flank face, and the second flank wear is the most serious. The drilling force of the stepped drill is smaller than that of ordinary twist drill.The tool life of step drill is much higher than ordinary twist drill.

Abstract:Based on the traditional VARI technology, a new generation of low cost liquid molding technology has been developed to satisfy the mass production demands of aeronautical composite structure. The proposed multiple approaches are applied to control the resin pressure difference between the injection and vent location and the flow control of the resin during the molding process.The results of the comparative experiment show that the thickness uniformity of the composite laminates molded by the new liquid molding technology are comparable with those of the laminates molded by prepreg/autoclave process. Applying the new liquid molding technology, the molded civil flap has good appearance and internal quality satisfying the application requirements of aeronautical composite.