Abstract:For the liquid bipropellant rocket engine,the research progress of three major thruster material systems,including refractory metal,precious metal and composite material,have been summarized.The preparation technologies,application,limitations and development of advanced material are presented in this paper.

Abstract:The microwave absorbing mechanism of ferrite materials was briefly introduced,and the latest research achievements of pure ferrites,carbon-based ferrite composites,ferrite/polymer composites and biology-based ferrite composites were introduced in detail.The developmental directions of ferrite microwave absorbing composites should be focused on the diversity of microstructures,composition of multi-components,synergization of different mechanisms among all composites,adjustable absorption bandwidth of self-driven and the environment friendly in future for the aim of thinner,lighter,wider absorption bandwidth and stronger absorption intensity.

Abstract:In order to study the springback characteristics of braided spring in high temperature baseline seal,a parametric model of braided spring tube was established by Pierce coil model.The static simulation of braided spring tube was carried out by using finite element software.Compared with the experimental data,the simulation results are in good agreement with the experimental results when the friction coefficient of the contact surface is 0.1.Spring stiffness is very sensitive to line diameter,and the relationship between spring resilience and line diameter is non-linear and high-order.Increasing the number of strands of braided yarn will multiply the spring stiffness.The influence of temperature on spring stiffness is small when it is lower than 600 ℃.When it is higher than 600 ℃,spring stiffness decreases rapidly with the increase of temperature.The minimum fatigue life of braided spring tube calculated by S-N curve is higher than that of sealing design at 650 ℃.According to the design requirement of baseline seal,it is recommended to use the parameters of ring density LD=0.05,line diameter 0.32 mm and double-wire braiding to make braided spring tube.

Abstract:A three-dimensional finite element model with different stitching densities was established,which was based on the stitched carbon fabric satin reinforced composites,and the elastic modulus of the composites was predicted.The stitched composite specimens prepared by RTM process were used to test and verify the validity of the finite element method.The result shows that the in-plane elastic modulus of the composites decrease with the increase of the density,with the maximum magnitude of the reduction of about 44%,The Poisson"s ratio of the composites has no significant change.The experimental result is consistent with the regularity of finite element prediction.

Abstract:Composite bonding repair was one of the important processes for aircraft structural repair and the scientific bonding process design was an important factor to ensure the repair effect of aircraft damage structure.In order to study the influence of adhesive technology on repair and explore the best bonding process parameters,the finite element model was established to analyze the load transfer behavior of composite bonding repair interface by ANSYS workbench.The material and thickness of the patch,shear modulus and thickness of adhesive layer were taken to discuss the effect on bonding repair.The simulation results show that when the patch material is boron epoxy resin,the risk of adhesive failure is the smallest.When the patch is thicker,the effect of bonding repair is good,but too thick patch will weaken the effect of bonding repair.The larger shear modulus of the adhesive,the better the repairing of the damaged area.It is suggested to choose adhesive with high shear modulus in engineering application.The thicker layer will increase the probability of defects in the layer so as to weaken the repair effect.Therefore it is suggested to select the layer with minimum thickness reasonably.At last, the surface treatment of the repair interface,the glue overflow at the end of the composite material and the chamfering treatment are all beneficial to the load transfer of the repaired structure,to ease the stress of the adhesive interface and to reduce the risk of layer failure.

Abstract:The effects of two typical spinning techniques,i.e.the horizontal and diagonal feeding paths of the spinning roller,on the inner surface defects of its spun dome of TA1 seamless liner of composite overwrapped pressure vessels,are investigated by utilizing the neck-spinning experiments and finite element analysis, respectively.The experimental results indicate that a significant improvement in the inner surface finishing has been obtained by the horizontal paths,which is an effective way to reduce the inner surface defects for the seamless titanium liner.The finite element analysis reveals that the horizontal path is provided more homogeneous deformation with significantly less variation in strain gradient on the dome inner surface than the diagonal path,which is the critical factor for the horizontal path with an improved inner surface quality.

Abstract:In order to explore the mapping relations between cutting force and process parameters during milling process of carbon fiber reinforced composite (CFRP),the finite element model of CFRP milling process and simulation analysis of cutting force were carried out. Based on ABAQUS software,the CFRP milling finite element model was established by defining material properties,material failure models,fiber layup and fiber orientation,and the model was verified by cutting experiments.Based on the model,the influence of process parameters such as fiber orientation angle,milling speed,feed per tooth and rake angle on cutting force is analyzed. The simulation results show that the cutting forces decrease with the increase of the fiber angle from 0° to 90°,while the cutting force increase with the increase of the fiber angle from 90° to 180°.The cutting force increases with increasing milling speed and feed per tooth,and decreases as the tool rake angle increases.

Abstract:According to the requirement of resin for ablated heat-resistant composites by RTM process,a solvent-free high residual carbon ablative resin for RTM process and its normal reinforced composites were studied.The viscosity-temperature characteristics,heat resistance,ablative properties,mechanical properties and thermal-physical properties of composites were discussed in detail,and the thermal test of solid rocket egine was carried out for the components of ablative material by RTM.Experimential results show that RTM process applicable period of this ablative resin is as long as 120 mins,its carbon residue rate is 67.1%,interlayer shear strength of the normal reinforced composites is 39.3 MPa.It shows good characteristics of solid rocket egine exiting section materials.

Abstract:Automated fibre placement (AFP) enables the trajectory of unidirectional composite tape to be optimized,but laying down complex shapes with this technology can result in the introduction of defects.In order to solve this problem,the specimens are manufactured by an automated fiber machine which enables 2 prepreg fiber tows to be draped simultaneously,gap and overlap embedded defects are introduced on two cross-ply layups of [(90°/0°)5/90°] and [(0°/90°)5/0°].Autoclave cure without a caul plate results in local thickness variation and microstructural changes which depend on the defect type.This has a strong influence on mechanical performance. Use of a caul plate improves these variations.In the case of gap defects with fiber angle 0°,the tensile strength of the plate with a caul plate increased by 218.5%. In the case of overlap defects with fiber angle 0°,the tensile property of the plate with a caul plate is 69% higher than the plate without it. The direction of 90°fiber is not the main bearing layer,the caul plate is less effective in the defects with it.But the tensile property of the gap and overlap specimens with a caul plate is improved by 3.2% and 15.6% respectively.

Abstract:In order to solve the mechanical instability of the initial state of soft polyimide foam, the Solimide^® AC-550 polyimide foam was used for different pressure and pressure pretreatment respectively, and the tensile and compressive properties of the pretreated samples were tested.The results show that the negative pressure pretreatment damages the mechanical properties caused by the foam,and the pre-treatment at +4 kPa can make the foam obtain relatively stable mechanical properties and meet the needs of engineering applications.

Abstract:In the process of the deep space explorations,the application of multilayer insulation materials has been extensively recognized as the most common method of realizing heat insulation in propellant tanks.Compared to other materials,however,the structure in which multilayer insulation materials are made is relatively complex. Additionally,there are also a set of specialized criteria to which its processing,installation,and application are constrained.This paper explored the assembly process in the practical processing of multilayer insulation materials by developing a new and standardized mode of using Velcro straps and glue guns.Next,the performance of this process was recorded and compared with the conventional winding coating process.Subsequently,the multilayer insulation coating process was tested and the influence of adiabatic effect was analyzed.Through the high vacuum test platform,the equivalent thermal conductivity of the multilayer insulation components formed by this process could reach 1.1 mW/(m·K) with smaller heat leakage and system stability.

Abstract:A processing method for composite laminates with intersection ply mode was putted out in this paper based on automated fiber placement (AFP) technology.The samples of the composite laminates were prepared,including crossing,crossing intersection ply laminates and traditional,two-direction intersection,four-direction intersection ply quasi-isotropic laminates.Then,the laminate mode and mechanical properties of the composites were studied by mechanical properties testing,microscopy and ultrasonic testing (UT).The results show that the tensile, compressive,and flexural properties of crossing intersection ply laminates are lower than traditional,but the interlaminar shear strength is increased by 16%.With the deepening of intersection,the tensile properties are weaker.The open hole tension,compression and compressive residual strength after impact(CAI) residual ratio of quasi-isotropic intersection ply laminates is higher than traditional.Intersection ply laminates have higher damage tolerance than normal ply laminates.

Abstract:This paper was motivated by designing three-dimensional five-directional structure with the non-periodic characteristics by the process of the yarn reduction.Then carbon/epoxy three-dimensional five-directional braided composites were prepared.The universal material testing machine and the high speed camera were employed to the tensile mechanical behaviors and damage process.Furthermore,the progressive damage and final failure images were observed by using Micro-CT and scanning electron microscope (SEM).The failure mechanism of non-periodic braided composites were analyzed and compared with that of the periodic samples.The results show that the tensile strength of non-periodic 3D braided composites is 16.84% lower than that of periodic materials with the same structural parameters.The damage of non-periodic three-dimensional braided composite material is derived from the yarn reduction,and the stress concentration is formed,and the ultimate failure mode is based on the fiber bundle pulling fracture.The results of this study can provide a basis for structural design and strength analysis of special-shaped braided composites.

Abstract:To ensure polycarbosilane work safely,according to relevant national testing standards and instruments,three fire and explosion characteristic parameters of polycarbosilane dust were tested,including minimum ignition energy,minimum ignition temperature and minimum explosion concentration using the standard instrument.The results show that minimum ignition temperature is 320 ℃,the minimum ignition energy is 1.5 mJmin<2 mJ,minimum explosion concentration is 12 g/m³＜C_min＜13 g/m³.Combined with the fire and explosion characteristics of common explosive dust,the minimum ignition energy is low and the minimum explosion concentration is small, indicating that the polycarbosilane dust is easy to be detonated.

Abstract:The 45 steel rolled plate with 120 mm thickness was roughly-treated and tempered.After heat treatment,the defects in the middle part of the thickness direction of the steel plate were found by ultrasonic inspection.The results of failure analysis show that the defects in the steel plate are banded structure and distributed along the deformation direction,and some of the banded structures have intergranular cracks.The mechanism of appearance of banded structure and crack is as follows:the central part of the ingot casting process appear dendritic segregation,and the segregation zone is lengthened during the rolling process to form the segregation zone.Because of the high hardness of martensite structure forms in the strip zone,the microstructure of martensite strip is cracked along the intergranular brittleness under the action of microstructural stress and thermal stress during the tempering treatment.

Abstract:For the technical problems in eddy current testing of stainless steel thin-walled flat tube,the equivalent filling coefficient calculation method of eddy current testing coil was adopted by analyzing the characteristics of flat pipe forming process.According to the sensitivity difference of the profile,a reasonable testing process was developed, and the eddy current testing of the stainless steel thin-walled flat pipe was effectively realized.Destructive tests and flight tests verify the reliability of the inspection process.The eddy current testing technology has been applied to several types of thin-walled flat tubes.

Abstract:The surface of the anodized film had uneven color(blacking).In order to find out the reason，macroscopic analysis, fracture observation and other physical and chemical analysies were carried out.It is determined that the reason for the blackening of the anodized film is due to the existence of composition segregation (high alloy content),resulting in a relatively smaller grain size,worse corrosion resistance and difference of microstructure of film.There are more alloying compounds inside the film, therefore the film exhibits a black color.

Abstract:The low-temperature rapid recoating process of the ablative anti-heat coating was investigated.Several approaches for improving the adhesion of the coating,rapidly solidifying,and controlling the excess substance were proposed according to the pre-flight state of the aircraft.The wind tunnel test shows that the ablation coating has a small amount of ablation and good heat resistance,with a maximum surface and back temperature of 580 ℃ and 64 ℃,respectively.The coating deposited with this technology is tested successfully in the aerodynamic environment for many times,demonstrating that this recoating process has good process stability.

Abstract:In order to study the influence of the tool wear on the surface quality of the TC11 in the milling process,the experiment between the tool wear and the milling surface roughness and the surface residual stress was designed.The results show that the tool wear in the milling process of the TC11 can be divided into three stages: the initial wear,the normal wear and the severe wear.When the tool is in “the initial wear”,the surface roughness of the TC11 decreases gradually with the cutting time,and the residual stress of the milling surface also decreases.When the tool is in“the normal wear”,both the milling surface roughness and the surface residual stress increase,but the increasing rate is stable.When the tool is in “the severe wear”,the surface roughness increases rapidly,and the surface residual stress increases significantly compared with the previous two stages.In addition,the surface residual stress of the TC11 during the test process are all in compressive stress.