Abstract:In order to meet the requirements of maneuverability and protection performance of light armored vehicles under modern warfare conditions, the current status of application of armored protective materials and the testing methods for mechanical properties under different strain rates were reviewed. Experimental tests, numerical simulations and theories of armored protective performance evaluation was discussed. The influence of materials, structural forms, layer thickness, restraint effects and the interface between layers on the protective performance of light multi-layer composite armor was introduced.The trends of future development was proposed.

Abstract:The recent advances of holes-making technology for CFRP/Ti laminated composite were reviewed, including the method of measurement and the change rule for both thrust force, torque and temperature during conditional drilling, and the relationships between cutting-tool wear, machining damage and drilling technique.The implementation,motion feature and processing quality of helical milling,low-frequency drilling and ultrasonic assisted drilling is summarized and analyzed.The applications and research tendency for hybrid CFRP/Ti composite holes-making are also discussed.

Abstract:In order to meet the higher requirement of reusable rocket in the future, a light, high-pressure resistance and reusable astronautic composite vessels was designed. The pressure vessel used metal inner liner/composite layer structure form.The composite layer is made of T700 carbon fiber and resin, and the material of liner is aluminum alloy.Based on the finite element simulation and experiment, the strength and fatigue life of the pressure vessels were verified.The blasting strength of the composite pressure vessels, in simulation and experiment, is 81 MPa and 84 MPa respectively. The cyclic fatigue life is over 1 200 times. Under the working pressure of 23 MPa, the pressure vessels could meet requirements for 300 cycles.

Abstract:Gap,misalignment and non-centering of probe (NCOP for abbreviation) are three important elements of the assembly quality of friction stir welding joints.Actually, these three elements have combining effects on the joint performance. In this paper, aiming at AA221 that is commonly used material in aerospace welding structures, the mathematic model between these three elements and the weld joint performances is established by the response surface methodology.The influence of each element on the weld joint is analyzed.Through experiments, the gap is found to be the key element on the weld joint performance, and the amount of misalignment and NCOP will cause the weld joint performance to show asymmetry.This method provides a mathematical model for the quantitative description of weld assembly quality.And, the mathematic model is used to provide reasonable instruction for these three elements of assemble quality of weld joints. This method avoids the disadvantages of traditional way on individual assembly elements and has good engineering application prospects.

Abstract:In order to explore the influence of grinding parameters and electrolysis parameters on surface roughness in ELID grinding process, the surface roughness prediction model of ELID grinding was established based on the undeformed chip thickness model by taking into account the randomness of the grit height at the grinding wheel and the influence of the oxide layer in the ELID grinding. Single factor experiments were carried out to study the influence of the parameters of ELID grinding on the surface roughness, and the relationship between the electrolytic current and the thickness of the oxide layer was discussed. In the full factor experiment, the influence of the grinding parameters on the surface roughness was studied by taking the workpiece speed, the grinding wheel speed and the feed depth as the influencing factors, and the prediction model was verified. The results show that in the grinding parameters, when the other conditions are fixed, the surface roughness decreases with the increase of the wheel speed, and increases with the increase of the workpiece speed and the depth of the cutting.At the same time, the prediction error of the roughness is 8.75%, the prediction model is valid and reliable.

Abstract:To meet the lightweighting tendency of novel aerocrafts, ceramic insulating tiles with lower-density (0.25 to 0.30 g/cm³)were fabricated by adjusting densification degree, without changing the composition and primary processing parameters.The tiles' microstructure, thermal conductivity, mechanical properties and high-temperature insulation performance were analyzed.In addition, the effects of sintering temperature and the ratio of long fibers to short fibers on the tiles' thermal and mechanical properties were studied. The results show that the thermal conductivity decreases with decreasing density, while the mechanical properties and high-temperature insulation performance also decrease; increasing sintering temperature is an effective approach to improve the tiles' mechanical properties for lower-density tiles, while the different ratios of long fibers to short fibers do not affect the tiles' properties obviously.

Abstract:The even and compact Ir coating was deposited on Ta-10W alloy substrate by arc ion plating.The oxidation resistance and thermal shock resistance of Ir coating at high temperture was studied.Results show that the Ir coating can keep protecting Ta-10W alloy substrateat at 800℃ and 1 100℃.The light oxidation occurs and bowrn oxides appear on surface after 20 h.At 1 900℃, the oxidation resistance of life reachs 10 hours and above.Under temperature change from room temperature to(1 900±50)℃, the times of the thermal shock is 1 000 over cycles.

Abstract:The physical simulation of 2219 Al-alloy was carried out by the Gleeble-3500 thermal simulation tester.Through stress-strain curves and microstructure observement,the heat plastic rheological behavior of 2219 Alalloy and its effect on spinning forming was studied. The results show that the rheological stress of 2219 Al-alloy during heat plastic deforming is mainly influenced by deforming temperature and strain rate,the effect of deformation rate is not obvious.The peak stress and steady state flow stress both reduces with improving temperature and dropping strain rate. It helps to achieve controlling shape during large scale 2219 Al-alloy component spinning forming by combining Gleeble physical simulation and process test. According to thermal simulation test result,spinning deformation is carried on 2219 Al alloy shell with spinning temperature from 300 to 350℃,feed rate from 0.6 to 1.5 mm/r and 30% deformation rate. Al alloy shell with good surface quality can be obtained with wall thickness under 0.2 mm and the unlaterial gap between inner profile and theoretical model under 0.1 mm.

Abstract:A 12mm thickness 2A14M high-strengh aluminum alloy welding joint with improved mechanical performance was achieved by using the "friction stir welding + solidification + artificial aging heat treatment" procedure. The result show that tensile fracture occurs in the weld nugget zone of the welded joint without heat treatment.The average tensile strength is 192.3 MPa.The micro hardness distribution of the joint shows a π like shape with the peak area in the weld zone.The gap of hardness between different characteristic areas reach up to 60HRC.The presented post-weld heat treatment has refined the grains, improved the uniformity of the microstructure, optimized the distribution of the strengthening phase and weakened the tearing effects by the the sharp grain boundaries during tensile cracking process,thus significantly improved themechanical performances of the joint. As a result,the maximum hardness gap has been reduced to below 20HRC in the joint after the post-weld heat treatment.Moreover, tensile fracture may takes place in the base metal area or the weld seam with the tensile strength of up to 440 MPa which is 2.29 times of that of the joint without post-weld heat treatment. After post-welding heat treatment, probabilities of fracture appearance in base metal and weld nugget zone are same, both are 50%,and thus the goal of improving the performance of friction stir welded joints is achieved.

Abstract:In order to investigate the influence of environmental temperature and humidity on operation period of low density ablator, the low density prefabrication has been perfused, cured and manufactured after placing in different times under the indoor situation, and further discussed the influences of viscosity on micro and macro appearances of ablator and process technologies.The results show that the viscosity is increasing with the temperature and humidity, and there is an inflexion point in this process. The humidity and temperature have more impact on viscosity after the inflexion point.The higher temperature and humidity are, the higher rising rate will be.The densities and macro appearance around inflexion point has no clear distinction. The fillers are uniform distributed and fully infiltrated by the resin before the inflexion point.Conversely, the fillers are uneven distributed and partly infiltrated, and the resin remains in micro-pores after the inflexion point. Therefore, the prefabrication must be perfused into honeycomb before the viscosity of resin reached its inflexion. The higher temperature and humidity are, the shorter operation period is.And the reverse is also true.

Abstract:Curing experiment was carried out on NOL rings of carbon fiber/epoxy composites by using the microwave curing technology. The mechanical properties and micro morphology of specimens with different curing methods, were analyzed.The results show that the curing mechanism of microwave curing method is different from that of thermal curing method.Microwave curing increases the curing reaction rate and shortens the curing cycle by 57%. The mechanical tensile strength and interlaminar shear strength of microwave curing specimens are similar to those of thermal cured specimens.Due to the selective heating of microwave curing, there is more resin matrix adhesion on the surface of the carbon fiber of the microwave-cured sample, which is confirmed by SEM micrographs.CT scan analysis indicates that the void content of the microwave-cured sample is 0.78% to 1.05%, which is slightly lower than the thermal-cured sample.

Abstract:In this paper, the two-edged double point angle drill, three-edged double point angle drill and arcshaped drill were used to drill CFRP.The characteristics of drilling thrust force versus time curve are studied.And the model of predicting the time varying curve of thrust force is constructed by using the method of predicting the critical inflection point of the time varying curve.The results show that the thrust force curve of the three-edged double point angle drill is the most stable, it means that the drilling process is the most stable.The maximum thrust force is the three-edged double point angle drill, followed by the arc-shaped drill, and the minimum is the two-edged double point angle drill.So, the two-edged double point angle drill is suitable for drilling CFRP.The thrust force versus time curve constructed by the method of predicting the critical inflection point on the time varying curve of thrust force can predict the thrust force versus time curve of double point angle drill.

Abstract:The mechanism of micro-structure and coating performance of tungsten coating were discussed.The influence of spraying parameters on the properties of plasma spraying tungsten coating includ the spraying power, spraying distance and pulerized gas delivery. The results indicate tungsten molten drop spread to form the pancake morphology or flower morphology owing to singel layer overlying, which is the columnar crystal microstructure. The particle molting state, the deposition velocity and the spraying environment determine the morphology of tungsten coating.And the pancake morphology with a thickness of about 10 μm and a diameter of about 50 μm is the better coating structure. Compared with atmospheric plasma spraying tungsten coating, vacuum plasma spraying tungsten coating has lower porosity,better heat transfer capability, better bonding strength and less oxygen content.Therefore, tungsten coating used as plasma facing material is feasible.

Abstract:The chemical structure change and curing behavior of the same thermosetting phenolic resin sample during continuous heating process were studied by in-situ infrared spectroscopy. The results show that there are mainly two reactions during the curing process of the resin,substitution reactions of hydroxymethyl and active hydrogen on benzene ring, condensation reactions between hydroxyl methyl groups, and hydroxyl methyl preferentially reacts with ortho hydrogen on benzene ring. From the continuous changes of infrared spectroscopy curves, condensation reactions between hydroxyl methyl groups build ether bonds, while the occurrence of carbonyl is related to the disappearance of ether bonds.Through continuous real-time monitoring of phenolic group changes during curing process by in-situ infrared spectroscopy, a scientific basis can be provided for the curing procedures of thermosetting phenolic resin.

Abstract:In order to explore the formation mechanism of surface defects such as delamination and chipping in milling of CFRP,the milling experiment of CFRP was carried out. Based on the single factor method,the influence of the fiber angle on the milling forces of CFRP was obtained. Using the central composite response surface method,the influence of milling speed,feed per tooth and milling width on the milling forces was analyzed,and the prediction models of the milling forces during the milling of CFRP were established. The experimental results show that the milling forces decrease with the increase of the fiber angle from 0° to 90°,while the milling force increase with the increase of the fiber angle from 90° to 180°. f_z and a_e have a significant influence on the three-direction milling forces. v_c has a significant influence on the y-direction and z-direction milling forces,while the influence on the x-direction milling force is not significant;the milling forces increase with the three milling parameters,and the feed per tooth has the greatest influence on the milling forces.

Abstract:The porosity had a great influence on the properties of the composites. To solve the problem that ultrasound could not well characterize high porosity composite materials,the characteristics and nonlinear characteristics of ultrasonic power spectrum were applied to characterize porosity of high porosity quartz phenolic composites, which is the effect of pores on the attenuation of fundamental amplitude and the breeding of harmonic amplitude in frequency domain. The results show that both methods can effectively characterize the pore content of high porosity composites. It is easy to measure the ultrasonic power spectral characteristic parameters based on the fundamental analysis in frequency domain, and it decreases with the increase of pore, which has some advantages when the porosity is low. The second order nonlinear characteristic parameters of the ultrasonic wave based on harmonic analysis are increasing with the increase of porosity, which is more advantageous to the high porosity characterization.

Abstract:The mechanical properties of monofilament of imports and domestic poly-phenylene benzodiazole (PBO)fiber,and aramid fiber were measured by constant velocity tensile tester. The effects of different preparation conditions and test conditions on the tensile properties of organic filaments were investigated. The main factors included loading rate,gauge length,fiber moisture absorption and thermal aging temperature. The results show that the tensile strengths of the four fibers calculated by Weibull statistical method decrease gradually with the gauge length increasing from 5 mm to 60 mm. With the loading rate increasing from 5 mm/min to 200 mm/min,the tensile strengths of the four kinds of fibers show first increase and then decrease trend of changes. With the increase in moisture absorption,the strengths of imported PBO fiber and aramid fiber both decrease gradually. As the accelerated aging temperature increases,the imported PBO fiber and aramid fiber show reduced tensile strength,which decrease by 39.1% and 51.6% respectively after heat treatment at 300℃ for 40 h.