Abstract:This paper reviews the property of the CFRP firstly,then summaries the defect of drilling fiber laminated material and the available solutions.In the second part,the characteristics of vibrating assisted machining(VAM)and vibrating assisted drilling(VAD)mechanism of decreasing defect during processing are introduced.In the last part,the paper reviews the development of vibrating assisted drilling CFRP.

Abstract:The aging of non-metallic materials and products was one of the determining factors of the weapons' lifetime.The existing accelerated aging test standards of non-metallic materials are introduced in this article,and the similarities and differences between these test standards are analyzed.The conceptions of the development trends of accelerated aging tests are also proposed.

Abstract:TiAl-based alloys with high specific strength and excellent mechanical properties at elevated temperatures have been regarded as candidates for high-temperature structural applications in the aircraft and aerospace.However, low plasticity and oxidation resistance at temperatures above 800℃ are main obstacles for their practical applications. In this paper, oxidation behavior, oxygen diffusion and their effect on mechanical properties of TiAl-based alloys have been summarized. Considering oxygen diffusion behavior and its determining factors in the environment of practical applications, recent progress of surface treatment and alloying technique to improve the oxidation resistance of TiAl alloys has been also reviewed. Meanwhile, the possible near future developing directions of the oxidation resistance and its controlling techniques for TiAl-based alloys are forecasted.

Abstract:The finite element model is developed by Abaqus for analyzing the fracture problem of cracked metallic plate repaired with the double-side adhesively bonded composite patches, in which the thermal residual stresses is also contained, and the stress intensify factor(SIF) is used to evaluate the repair effect.Meanwhile, with the help of orthogonal table L₉(3⁴), the parameter of the patches,which influence the repair effect,has also been evaluated. The orthogonal analysis result shows that,in confidence level of 99%, the contribution ratio of lay-up direction and patch thickness are 68.77% and 29.59% respectively.Meanwhile, the influence of patch length is rarely.Moreover,connect the orthogonal analysis result with the applied condition,the patch parameter is elected to repair the cracked metallic plate for the uniaxial tension test.And the test result indicates that the tension intensity of the repaired plate is 1.32 times than cracked plate,and 97.2% of the uncracked one. Meanwhile, the elongation of the repaired plate is 2.24 times than the unrepaired one,and 50.7% of the uncracked one.The repair effect is best when the square patch length is 40 mm, thickness is 1.2 mm and lay-up direction is [0°/90°]_s.

Abstract:DSC was used to study the non-isothermal curing kinetics of an 80℃ curing epoxy resin system(LTCEP),and the sum model coupling the Gaussian distribution and the Lorentzian distribution was used to simulate the DSC peaks. Afterwards the variation of activation energy versus conversion and the non-isothermal curing kinetics for each stage of the curing reaction were studied by the Flynn-Wall-Ozawa method and a model-fitting Málek approach, respectively.The overall reaction rate was obtained according to the peak fit results and then the isothermal curing behaviors at different temperatures were predicted.Finally, tensile experiment is performed to investigate the tensile properties of LTCEP.The peak fit analysis indicated that each DSC curve could be well simulated by using three Gaussian-Lorentzian components.Afterwards the non-isothermal kinetics investigation revealed that the variation of activation energy versus conversion for each stage of the curing reaction changed insignificantly and the curing rates of each stage could be well described by the Šesták-Berggren model. Moreover,it is predicted from the overall reaction rate that the conversion of LTCEP would be up to 90% when this resin system was cured at 150℃ for 3 min or 140℃ for 5.5 min.The tensile test at room temperature showed that the tensile strength and the elongation at break of LCTEP cured at 80℃ for 8 h are respectively 51.34±11.78 MPa and 1.23%±0.34%,and the tensile properties did not change significantly after the post treatment on the samples at 125℃.

Abstract:Based on the balanced stable network as constraint conditions, with equal strength designing and improving the critical buckling load as the design goals, wound surface of sandwich composite cylinder was optimized. Firstly, based on equal strength design method, the optimal winding pattern and winding angles of spiral winding were obtained.The winding angle should satisfy α≤54.7°.Secondly, in order to meet the need of structural strength and stability, stability models with different aspect ratio are established using ABAQUS finite element software to obtain the α_opt.The study has found that when the aspect ratio 0.5≤ η≤ 3, with the increase of η, the best way transited from a single wound spiral wound ring plus hoop wound to the longitudinal placement plus hoop wound, while the maximum critical buckling load is approximately decreasing in quadratic relationship. The optimization method can not only achieve weight reduction requirements, but also meet the dual indicators of structural strength and stability.

Abstract:A 3D hollow composite with "X" core structure was designed and composited. Compression characteristic and property of 3D hollow composite were tested by Instron 3385H, and the stress-strain curve was obtained. According to structure parameter of the composite, the structural model was established. Static properties of the composite are simulated by ANSYS Workbench. Simulated result is compared to the testing result. The result showed that the main loads were supported by core structure of composite and the main failure occurred there. Simulated results approximately agree with the experimental, the models have certain veracity.

Abstract:Using ceramic fibrous insulating tiles as skeleton, the alumina sols via sol-gel process were infiltrated into the tiles via vacuum infiltration, followed by gelation, aging and supercirtical drying to fabricate the aerogels impregnated high-temperature insulating tiles. The aerogel/tile composites' microstructure, thermal and mechanical properties at high-temperatures (up to 1400℃) were investigated. The results showed the composites exhibited a small linear shrinkage of 2% after hating at 1400℃ for 30 min.With increasing heating temperature, the aerogels' particles grew and condensed; the aerogels changed from filling the fibers' pores to being condensed, and to being mainly attached to the fibers' surface, but such evolution did not obviously affect the fibrous skeleton. After the aerogel impregnation, the specimen's room-temperature and high-temperature thermal conductivities decreased significantly, and the cold-face temperature dropped from 945℃ to 870℃ in the back-temperature tests. In addition, although the composites' room-temperature mechanical properties increased slightly, the high-temperature compressive strength drastically degraded at 1200℃ and 1400℃.

Abstract:TaSi₂ was added into ZrB₂-20%SiC to get ZrB₂-10%SiC-10%TaSi₂. Then composites were oxidized in stagnant air at 1000℃,1200℃,1500℃ and 1650℃ for 5 min,15 min,30 min.The composites were prepared by hot pressed sintering (1950℃/30 MPa/30 min) and analyzed by X-ray diffraction and SEM.The weight change due to oxidation and microstructure were recorded. The results show the density and mechanical properties are increased by adding TaSi₂ into ZrB₂-20%SiC,but the oxidation resistance of ZrB₂-10%SiC-10%TaSi₂ is decreased above 1200℃.

Abstract:A novel SiBCN hybrid resin was prepared from 1,7-bis(dimethylsilyl)-m-carborane and viny-containing polysilazane. Composition, curing behavior, thermal stability,thermal pyrolysis reaction and process were studied by FT-IR, DSC, TGA and PyGC-MS. The curing and pyrolysis reaction activation energy were calculated by Kissinger equation and Flynn-Wall-Ozawa(FWO) methods. The pyrolysis mechanism of cured SiBCN was also analyzed.The results showed that there is one exothermic peak during the curing reaction, and its curing reaction activation energy is 113.55 kJ/mol. SiBCN possessed an excellent thermal stability with the T_d⁵ and the residue weight of 73.1% at 900℃ in N₂.The decomposition reaction activation energy of the resin and the thermal stability increased following by the reaction conversion. When the pyrolysis temperature reached 300℃,NH₃ apperad resulting from the transamination reaction, whereas CH₄,CH₂ CH₂ and alkene produced at 500℃ and further species of the pyrolysis gas such as alkanes and alkenes occured at 650℃.

Abstract:This paper clarified the key problems in the application of the friction stir welding technology to the lock circumferential weld of the tank. Firstly, the conventional structure of the lock joint used to fusion welding must be redesigned, and the back welding groove and the front welding groove were eliminated. The results showed that the mechanical properties of the lock joint presented the best performance when the length of the pin was equal to the thickness of the short shell, and the fork ring was located on the advancing side of the weld. The results of ultrasonic phased array analysis showed that the signal display existing at the interface of assembly interface and welding nugget can not be interpreted as the defect signal. The vertical assembly welding scheme is used to assemble and weld the lock circumferential weld, and a set of tooling is developed to assure the assembly clearance, the wrong side, the flatness of the weld, and so on. The friction stir welding technology has been applied to the lock joint of the Φ3350 mm tank has been realised, and its nondestructive test results and geometrical dimension met the design requirements.

Abstract:A great temperature gradient easily occurred in the curing process of the thick wall carbon fibers/phenolic composite, usually caused an uneven curing.This paper focused on the research of temperature change inside this kind of product during curing through a temperature monitoring experiment by immersion a thermocouple inside of the product. Meanwhile, the curing reaction behavior of phenolic was studied by DSC technique and gel test. Experimental results showed that internal temperature of product was much belower than inside of autoclave during the early stage of raising temperature.The resin flew better with increase of temperature, and exothermic polymerization began when the resin gel at 95℃ to 100℃.Then the curing system is optimized according to the experiment results,including extend holding time of each temperature,delay the heating rate at early time,adjust the time of total pressure and increase preservation at gel.In the end,the verification is conducted.The results show that optimized curing system is reasonable,a great decrease of defect is confirmed by ultrasonic detector and the quality uniformity of product is improved effectively.

Abstract:The cure kinetics of the epoxy resin 607 for an out-of-autoclave(OoA) composite was investigated by differential scanning calorimetry(DSC),and the cure kinetic formula of the resin was established. The prepreg with dry fiber regions remaining and the OoA composites were prepared. The quality and properties of the T800/607 composite were studied. The results indicated that the T800/607 prepreg owed a tack life at room temperature over 30 days and the void content of the OoA composite is far below 1%. The short beam shear strength and flexural strength of the OoA composite are 96.7 and 1480 MPa,respectively, which can be compared with the autoclave cured ones.

Abstract:The microstructure,tensile strength,bonding properties,high temperature resistance of strain isolation pad,which was prepared by needle process with aramid fibers as material are investigated.The results show that strain isolation pad has good coordinate deformation capacity and tensile strength when the punch density is 35 punches/cm² and the material density is 0.18 g/cm³.When the heating temperature is lower than 200℃, there is no significant change of structures and intensity. At the wind tunnel environment, maximum surface temperature is 1500℃, the apparece of the thermal protection system is complete with no cracks and no looseness after the wind tunnel test, the test results validate the reliability of strain isoation pad.

Abstract:During in-orbit operation, the optical and thermal control performances of satellite thermal control coating will degrade due to integrated space environment effects and hence has a great impact on reliability and lifetime of satellites.In this paper, an in-orbit experiment of thermal control coatings is carried out for 5 years to investigate the influence of multi-factors environment. And the sensitive factor of coating performance is achieved and then the in-orbit property evolution law and life prediction model are built.Meanwhile, a ground simulation experiment with proton, electron and ultraviolet irradiation factors is carried out to study the influence of those factors on thermal control coatings.The results demonstrate that the absorptance of thermal coatings increase from 0.12 to 0.23 after 5-years' in-orbit operation while this value increases to 0.22 after the ground simulation test with the equivalent radiation dose.The thermal control performance degradation and test time or irradiation dose are linear related and positive correlated both in orbit and on ground, which has also verified the effectiveness of ground test.

Abstract:When the missile launcher was carried out during the third test procedure, fracture occurred to the 40CrMo bolt. In this paper, investigations were performed by macroscopic examination, electron microscope observation, metallographic examination and chemical composition analysis in order to get the fracture property and the reason of the fracture. The results suggest that the property of fracture is stress corrosion, as well as the original micro-cracks in the bolt before galvanizing and lead to stress concentration. During the test, the existence of bending stress and atmospheric oxygen, such as sulfur, chlorine, sodium and other interaction, which result in fracture of the bolt. Furthermore, high hardness values and a slight temper brittleness can also have a certain effect on the bolt fracture.

Abstract:Compression resistance experiment was carried out with water on tank bulkhead which was welded by friction stir welding(FSW) on longitudinal weld and by variable polarity tungsten inert gas welding(VP-TIG) on orbicular weld, and the strain brought by press was measured on typical weld position. The result shows that the intersection of FSW and VP-TIG weld has lower yield strength, which enters into the plastic deformation state at first, is the weak position of the tank bulkhead.

Abstract:Using the portable ultrasonic feature imaging testing system of full wave acquisition of test signal,can be realize through the extraction and reconstruction of defect feature signal, automatic identification of defects,which can be applied to the surface and irregular surface detection with quantitative accuracy of 0.1 mm. The experimental results show that the low-frequency narrowband ultrasonic transducer can reduce the copper net on the acoustic attenuation and distortion, ultrasonic feature imaging tomography method can identify layered surface copper net structure of CFRP foam sandwich defects effectively,accurate recognige the location of impact of defects and debonding defects and quantification. The detection method is fast, accurate, reproducible and reliable

Abstract:Using carbide twist drills,the influence of machining parameters on cutting force, cutting temperature and hole quality of titanium alloy have been analyzed. The results show that with the increase of speed, axial force of the titanium alloy layer decreases gradually, and with the increase of feed,the specific value axial force of CFRP/titanium alloy layer ratio increase gradually.The exponential formula models of drilling force were obtained through regression analysis method and the regulation of the drilling force influenced by the feed and cutting speed was obtained respectively,F_z=2 088n^-0.1222·f_r^0.2016. The error of the two equations have been tested both less than 10%. When the feed is constant on titanium alloy layer, with the increase of speed on titanium alloy layer, the maximum discoloration ring diameter and the highest interpass temperature of CFRP increased gradually.

Abstract:Ceramic insulation tiles with defects were repaired by introducing high-temperature ceramic powders, such as MgO, YSZ, Al₂O₃ and tile matrix powders. The microstructure, mechanical property and thermal insulation properties of tile before and after repair were systematically investigated. The results show that the powder containing tile matrix powders is the best method to repair the ceramic insulation tile. The part of the complement has good compatibility with the body, and the micro morphology is similar to remain porous network structure. After repairing, the density, thermal conductivity at room temperature and compressive strength of the samples are 0.24 g/cm³, 0.044 W/(m·K) and 0.58 MPa, respectively. After 1 200℃ and 30 min heat treatment, the complement and the tile body have good bonding,cracks,depressions and other defects free.

Abstract:The carbon fiber-reinforced plastics composite components were taken as research object, the experiments of the centring-slots in a hole were carried out by the forming cutters with reduced chisel edge.The effects of the chisel edge size and of the moving route of the cutter on the cutting forces were investigated.The results show that when the chisel edge of the cutters reduces, the cutting forces tends to decrease,but the trend of the degression of the cutting forces become slow when the chisel edge is reduced to 0.5 mm.The processing scheme is of short single tooth processing time,low cutting forces, and excellent processing quality,which is one time feeding to finish a slot using the forming cutters with 0.5 mm chisel edge. It is a reasonable processing scheme.