Abstract:High-entropy ceramics are a novel class of ceramic materials， which have attracted extensive attention in recent years because of their unique structure and properties. In this review， the definition of high-entropy ceramics has been introduced and the preparation methods of high-entropy ceramics，such as solid-state reaction， precursor pyrolysis and spark plasma sintering， are summarized. The research progress of high-entropy ceramics， such as high-entropy oxides， high-entropy carbides and high-entropy diborides， are discussed in detail. Finally， the characteristics and application prospects of the high-entropy ceramics are summarized.

Abstract:Silicon aluminum alloy is an important material that is widely used in electronic packaging and automotive fields.But it has problems such as poor surface quality and severe tool wear during cutting. Studying the surface defects and cutting tool adaptability of silicon aluminum alloy in the cutting process is the key technology to improve the machining quality of silicon aluminum alloy.This article systematically reviews the formation mechanism and control method of surface defects of silicon-aluminum alloy in cutting，as well as the selection of tool materials and wear mechanism.The future development trend of this field is also prospected.

Abstract:The relationship between the characteristic structure and thermal stability of phenolic resin is of great significance for the selection of resin matrix for ablative materials. In this paper， the typical structure of phenolic resin was quantitatively described by ¹H nuclear magnetic resonance spectroscopy. The activation energy， reaction mechanism function， and thermal stability of different typical structured phenolic resins were studied. The results show that the activation energy of phenolic resin with different structures is 162 to 240 kJ/mol. The activation energy of the pyrolysis reaction is the highest and the thermal stability of the resin is optimum when the F/P value is 1.2 to 1.5. The most probable mechanism function of pyrolysis at 570 ℃ is g（a）=（1-α）^-b-1（b=5.2~6.7）， which is the chemical reaction mechanism. The results of pyrolysis kinetics are verified by qualitative and quantitative analysis of pyrolysis gas products using Py-GC/MS.

Abstract:In order to improve the efficiency and accuracy of fixture design and to promote the standardization of design， this paper summarizes the design and manufacture of compression test fixture for composite bypass compression test in ASTM standard. The CATIA secondary development method including Model Based Definition （MBD） information is employed. A parametric design method of composite by-pass compression test fixture is proposed. This realizes the rapid and accurate establishment of assembly model of test fixture with design and manufacturing information. The results show that the key dimension chain parameters of the test fixture assembly with design and manufacturing information are the diameter D and width W of the test piece. The test fixture designed by this study meets the requirements of accuracy and standardization of fixture design related to allowable value test standard for composite materials specified in ASTM and it shortens the design cycle.

Abstract:The milling force and temperature were relatively large in the milling process of super alloy and had a great influence on the surface quality and tool life. The milling process of GH536 was modeled and simulated by using finite element analysis method. The milling force prediction model of GH536 was established and the regression analysis of the model was carried out. The milling experiment scheme was designed and the simulation results were verified and analyzed. The simulation results show that milling depth， milling width and feed per tooth are positively correlated with F_x， F_y and F_z， while milling speed is positively correlated with F_z and negatively correlated with F_x and F_y. The milling depth has the greatest impact on the milling force， while the milling speed has the least impact； the milling force experimental results show that the established milling force prediction model can predict the milling force more accurately than the theoretical model in GH536 cutting process.

Abstract:In aerospace structures，honeycomb panels were often connected with other components by clustered inserts.In order to analyze the reason for the failure of CFRP honeycomb sandwich panel under the effect of temperature stress， the theoretical calculation and finite element analysis of the failure stress were carried out.It was found that the instability of the panel caused the structural damage.To solve this problem，the feasibility and efficiency of two improvement measures of increasing the thickness of face sheet and local strengthening are analyzed.Through comparison experiment，it is found that the local reinforcement method is more feasible and efficient. Finally，through the thermal vacuum test，it is verified that the local reinforcement method can improve the stability of the panel and prevent the instability damage.

Abstract:Carbon fiber reinforced ZrB₂-SiC composite ceramic and TC4 alloy were connected by using Ag-28Cu filler in the vacuum brazing furnace. Scanning electron microscope，energy dispersion spectrometer and mechanical universal testing machine were used to study the effect of brazing holding time on the microstructure and shear strength of the brazed joint interface. The results show that the carbon fiber reinforced ZrB₂-SiC composite ceramic / Ag-28Cu / TC4 alloy joints are well bonded. The typical joints are composed as following： TC4/TiC+TiCu/Ti₂Cu/TiCu/Cu_（s，s）/Ag_（s，s）/Ti₅Si₃/TiC/ZrB₂-SiC-C. Different holding times have not changed the phase composition of the brazed joints. However， it has an influence on the microstructure of the joints interface， the thickness of the weld and the number of constituent phases. With the increase of brazing holding time， the Ag （s， s） and Cu （s， s） areas in the center of the weld gradually decrease，the thickness of the Ti-Cu reaction layer gradually increased in the TC4 side reaction.The maximum thickness of the weld is 70 μm and the thickness of the central area of the weld is 45 μm when holding for 30 min. The average shear strength at room temperature increased first and then decreased with the increase of holding time and the maximum shear strength is 34 MPa at 810 ℃ with 20 min holding time.

Abstract:The performance of T700/3228 prepreg was studied by differential scanning calorimetry（DSC）， infrared spectroscopic，rheometer and mechanical properties testing.The result shows that the initial curing temperature and peak curing temperature are 67.9 ℃ and 89.5 ℃，respectively. The viscosity for 3228 resin at 60 ℃ is between 20 to 30 Pa·s and maintains more than 2 h.When temperature is above 65 ℃，the rapid curing characteristics is showed. The composite with low porosity and good mechanical properties have been prepared by adopt 60 ℃ procuring 1 h，80 ℃ curing 3 h as molding process plan.

Abstract:The coating material feasibility and reliability in the prevention and control of remnant material in microwave circuits was studied. The vacuum chemical vapor deposition method to deposit Parylene C film on the product surface was proposed. The experimental results show that the film can effectively control the remnant material with a diameter of less than 1 mm， and improve the pass rate of particle impact noise detection test. In the meantime， the film has good compatibility with assembly processes such as welding， gluing， interconnecting， and cleaning and meets the reliability requirements. The film has high insulation strength and excellent insulation protection for microwave circuit. Consequently， the arylene C film has application feasibility and potential value in microwave products.

Abstract:In order to study the axial force and delamination characteristics of glass fiber composite materials， electroplated diamond drills and carbide twist drills are used as drilling tools to carry out the orthogonal drilling experiments. The effects of the geometry and materials of drilling tools and drilling process parameters on the drilling axial force and the drilling quality are researched. It is concluded that the drilling process parameters have a direct impact on the drilling axial force and the drilling quality. High speed， low feed and suitable geometry， material of drilling tools can reduce the drilling axial force and improve the drilling quality. The axial force and exit delamination damage of electroplated diamond drills are greater than those of carbide twist drill. The optimization of the geometry of electroplated diamond drills is an effective way to improve the drilling quality.

Abstract:To solve the problem of poor performance of electrochromic films，which is the critical problem of electrochromic devices adapting to the current demand，the indium-tin oxide （ITO）/tungsten oxide （WO₃） films were prepared at room temperature by DC reactive magnetron sputtering on the polyethylene terephthalate （PET）/silver nanowire （AgNWs）.The photoelectric properties of AgNWs/ITO composite electrodes and the electrochromic properties of PET/AgNWs/ITO/WO₃ films were investigated. The results show that the sheet resistance of the ITO-compositing electrode is significantly lower than that of AgNWs electrode，and the surface is more uniform and smoother.Thereby it overcomes the uneven coloring and rapid performance degradation after a single cycle of the WO₃ film.The transmittance modulation of the flexible electrochromic film is 57.4% （at 550 nm） and 69.6% （at 1 000 nm），the colored and bleached response time is 10.4 s and 9.9 s，while the corresponding colored and bleached efficiency is 27.79 cm²/C and 40.45 cm²/C，respectively.In addition，the film can still maintain high transmittance modulation after more than 500 cycle stability tests and 2 000 bending tests，showing great application potential in the field of flexible electrochromic.

Abstract:The effects of holding time and pre-alloyed powder manufacturing methods on microstructure， tensile properties and tensile fracture morphology was investigated for powder metallurgy （PM） TA15 alloys. In this work， hot isostatic pressing （HIPing） technique was used to densify the TA15 pre-alloyed powder. The results show that the microstructure of PM TA15 alloys is composed of equiaxed α grains， lamellas α grains and a little β grains. When the holding time is 20 min during HIPping， the PM TA15 alloys have gotten full densification. As the holding time extends to 2 h， the microstructure became coarser. The tensile properties of PM TA15 alloys with plasma rotating electrode process powder are better than those of PM TA15 alloys with gas atomization powder. The tensile fracture mode is ductile fracture， and fracture morphology appearance is the dimple.

Abstract:In order to research the influence of lattice structure parameters on electromagnetic spectrum characteristics of wave transmission plate， the simulated models are built based on the model of body centered cube（BCC）， and the lattice structure parameters such as porosity， skin thickness， cell size and incidence angle are analyzed on the influence of band-pass resonance frequency and transmittance using CST software. Besides， a wave transmission plate structure with lattice structure is fabricated by the technology of selective laser sintering （SLS）， and its electromagnetic transmittance is measured at the frequency from 2 GHz to 18 GHz. The results show that the simulation results are in good agreement with the test results. With the increase of porosity， the first frequency point shifts to low frequency， and the second frequency point shifts to high frequency. With the increase of skin thickness， the transmission decreases. The cell size and skin thickness determine the passband resonance frequency of transmission spectrum， and the effect of porosity is small. When the incident angle increases， the horizontal polarization incident wave transmittance is greater than 75%， while the vertical polarization incident wave transmission rate decreases gradually at high frequency.

Abstract:To overcome the difficulty in measurement of the acoustic emission（AE） propagation and attenuation characteristics of aerospace composite cylinders， the theoretical formula for the amplitude attenuation coefficient of hybrid wave was obtained by studying theoretical calculation method of AE wave amplitude attenuation coefficient.The experiments on the composite cylinder were carried out by using two specifications of the AE simulators. The results demonstrate that the actual attenuation curves match well with the theoretical attenuation curves. The signal frequency and strength are different by using different AE simulators. The AE simulator of Φ0.5mm/2H pencil is more suitable for AE detection of composite cylinder.

Abstract:Since the solid rocket motor interface bonding is prone to debonding during its storage， ultrasonic longitudinal wave is used to detect the bonding quality of the first and second interfaces， the second interface debonding defect signals are usually mixed with multiple reflection and transmission signals of the first interface， resulting in that it cannot be distinguished from the bonding signal of the interface. To distinguish the echo signals of different interfaces， EMD （Empirical Mode Decomposition） is first used to decompose the echo signal and get the dominant modal component of the signal according to the correlation coefficient， then the interface bonding situation is obtained by extracting amplitude characteristics of the detected signal， finally， whether the bonding position is the first interface or the second interface can be determined according to the time. The results show that the features of ultrasonic echo signals extracted by EMD can realize the detection of debonding defects with a minimum diameter of 4mm in the solid rocket motor interface， besides， EMD can reduce the data quantity of analysis and calculation effectively， providing a certain basis for solid rocket motor bonding detection.

Abstract:To solve the problems such as big alignment deviation， inconsistency between the entity and the digital model and high processing cost in the processing of the positioning pin hole on the melon petal male mold， the alignment method was improved. By combining coarse alignment and fine alignment， as well as using the 3D edge finder to perform the program verification， the goal of accurate alignment between the theoretical digital model and the entity was achieved. On this basis， through the coordinate transformation of the ellipsoid parameter equation， the processing of the normal and axial positioning pin holes on the ellipsoid surface on the 3-axis machine tool is accomplished. Consequently， with the help of the improved processing method， the hole position accuracy reaches Φ0.1 mm and the processing cost is reduced by 75%. This improved method should be promoted and utilized in engineering applications.

Abstract:6A02 aluminum alloy sheet was widely used in helicopter， sometimes milling need to be carried out. By means of dimension measurement， tensile property detection and metallographic analysis， the influence of chemical milling on the thickness， surface quality， mechanical properties and microstructure of 6A02 aluminum alloy sheet was studied. The results show that chemical milling can thin the thickness of aluminum sheet. The combined effect of Na₂S and triethanolamine in the solution can reduce the galvanic corrosion effect of alloy elements and Al， and the surface quality of the thin plate is improved. The electrochemical properties of the precipitated phase of the alloy are not significantly different from the matrix， and will not cause intergranular corrosion defects of the alloy， and have no obvious effect on the mechanical properties and microstructure of the sheet. 6A02 thin aluminum sheet can be processed by chemical milling.