Abstract:This paper introduces the research and application status of foreign new high performance aerospace materials in light metal alloy, composite, special functional material, graphene and metamaterials firstly. Then the research progress on China's new high performance materials in aerospace is highlighted. The trend of new high performance materials in aerospace is also pointed out.

Abstract:In this paper, properties of boron-rich ceramics are introduced first. Then the crystal structure, thermodynamic property, synthesis and sintering methods, high temperature oxidation resistance, mechanical properties, friction and wear properties and electrical properties of SiB₆ are reviewed. Finally, the applications and future directions of SiB₆ are highlighted.

Abstract:Based on the difficult machinability of Al/SiC_p composite materials, a two dimensional finite element cutting model was developed in this paper. By using ABAQUS, the dynamic simulation of the cutting model was performed. Comparison of the result of simulation and experiment, the accuracy of the cutting model was verified. And then, the distribution form of SiC particle, the diameter of particle and the edge radius of tool effect on the cutting force were analyzed based on the model. The results show that the distribution form of SiC affects the chip morphology and the cutting forces are obvious, and particle clusters is not helpful for composite materials machining. The cutting force decreases with the increase of particle diameter, while increases with edge radius of tool.

Abstract:In order to realize the near-net-shape forming of the polyimide molding powder, the cold isostatic pressing(CIP) of linear polyimide molding powder was simulated by ABAQUS.The Cam-Clay model was used to analyze the change of the size of two types of blanks after cold isostatic pressing,and then the simulation results was verified by the experimental results.It is shown that the simulation deviation of the columnar blank can be controlled within 2.5%,and the error of cuboids blank within 4%.So this simulation method could predict the measurement accurately.

Abstract:Stress and damage analyses are performed on a carbon fiber overwrapped aluminum-lined cylinder under internal pressure through finite element method(FEM) by ABAQUS software. The variational thickness and wound angle of the head is reflected in the finite element model in accordance with the actual structure. A progressive damage model considering four failure modes are adopted for the composite, i.e., the fiber tension and compression, the matrix tension and compression. The regularities of the initiation and distribution of autofrettage pressure are analyzed. The effects of the autofrettage pressure on the stress amplitude of the liner are also discussed.It is concluded that when the cylinder carrying pressure is greater than the autofrettage process pressure, the PEEQ value of the liner will continue to accumulate after the autofrettage process, and the autofrettage process of the cylinder starts to fail.

Abstract:Experimental method was used to investigate the tensile failure modes of two different C/C composites bolts in this paper.Test results indicated that the failure modes were determined by the type of the structure of the bolt head. For the shear failure of the bolt head caused by the tensile load,the comprehensive effect of both the interlaminar and intralaminar shear load is the main factor, but not a single shear load.As a result,improve the design of the structure of the bolt head can enhance the strength of the composites.

Abstract:The influence of welding parameters on porosity in the welding of TC4 titanium alloy in flat and horizontal positions was investigated. Results showed that parameters had different influences on porosity in different positions. In flat position, the amount of porosity decreased first and then increased with the increase of laser power and defocus, it increased first and then decreased with the increase of welding speed; in horizontal position, the amount of porosity decreased with the decrease of laser power and the increase of welding speed, and it decreased first and then increased with the increase of defocus. By optimization of parameters with the range analysis method, the amount of porosity is reduced significantly in weld beads, and welds with good inner quality could be produced under both flat and horizontal welding positions.

Abstract:The tensile and compressive properties of needled felt C/C composite material at the temperature range of 20℃ to 1800℃ have been studied by test system of ultra-high temperature material performance and strain measurement system under high temperature. The results show that needled felt C/C composite material has different elastic modulus for tension and compression obviously, and the tensile and compressive modulus decrease linearly with the rise of temperature, but the tensile modulus decreases more quickly. At the same time, the tensile and compressive strength increase first then decrease with the rise of temperature, and the tensile strength reach to the maximum value at the temperature of 1600℃, then the compressive strength reach to the maximum value at the temperature of 1200℃. Needled felt C/C composite material shows fiber tensile brittle damage and fracture angle of 45° by high temperature tensile. On the other hand, needled felt C/C composite material shows compression failure caused by typical shear stress and the oblique angle of fracture plane is 45° under high temperature compression conditions.

Abstract:According to the mechanism of defects in CFRP drilling process, the acoustic emission signal rms value during drilling is collected by acoustic emission sensor. The RMS under different drilling parameters are analyzed, and the RMS corresponding to the tear at the entrance and the exit of the hole are identified. The experimental results show that the tear at the entrance and the exit can cause the mutation of the RMS during the drilling process, and can be effectively identified. When the spindle speed is constant, the RMS increases with the increase of the feed rate. When the amount is constant, RMS increases with the increase of spindle speed.

Abstract:In this paper, surface morphologies of Ti-6Al-4V forging and powder metallurgy workpieces were characterized, surface roughness mathematical models of the two machined workpieces were developed using orthogonal regression test,and the significances of the mathematical models were verified, the surface roughness mathematical models could predict the surface roughness changing trends. The experimental results showed that feed scratch, chip fragment and surface tearing defects appeared in the machined Ti-6Al-4V forging surface, while micro-void defect was formed in the machined powder metallurgy material surface apart from the feed scratch, chip fragment and surface tearing defects.The influence of feed rate on the surface roughness of both workpieces is greatest, and the existence of internal micro-void of Ti-6Al-4V powder metallurgy material led influence of cutting speed greater.

Abstract:In this study, electroless plating and pulsed electroplating were combined to prepare composite nano crystalline coating on the surface of CFRP composites. By the microstructure and X-ray diffraction analysis of the coating,the primary crystalline size is determine 50.6nm,and the crystalline grain size of the coating surface increases slowly with the increasing of the plating time, and the average increasing rate is 1μm per hour. By the measurement of the surface roughness, the value of Ra showes a 36% decreasing trend from initial machine coarsening to final pulsed electroplating. After chemical plating, the value of Ra is reduced from 1.55μm to 1.34μm, and after the pulse electroplating, the value of Ra is reduced from 1.34μm to 0.96μm.

Abstract:The process parameters on cutting force, surface roughness, surface profile and morphology, the corrosion and current density were studied. The results show that the milling force and surface roughness increase first then decrease and then increase with the increase of milling speed, and the milling force and surface roughness increase with the cutting depth increasing. The corrosion resistance of machined surface is improved by the extrusion strengthening of milling flank face. When the cutting speed is 4000r/min and the axial depth is 0.25mm, the corrosion resistance of the machining surface is the best. The micro-cracks are prone to produce under relatively larger cutting depth,so the corrosion of machined surface becomes more intense.

Abstract:There are serious problems in surface quality of the mided SiC_p/Al composites. The milling tests on SiC_p/Al composites were conducted with cemented carbide coating tools. Through single factor experiment, the article investigated the influence of cutting parameters on surface roughness.The results suggest that the surface roughness increases at first, then decreases with the increase of cutting speed, and increases with the increase of feed, radial cutting depth and axial cutting depth. The machined surface quality could be improved by using high cutting speed, low feed and the radial cutting depth equal or less than 4mm.

Abstract:The thermal conductivity of microporous nano plate and fiber board was measured by non steady hot-wire method at RT to 1000℃ temperature range,and the results were analyzed and explained by SEM micro morphology analysis and fluorescence spectrum composition analysis, combined with micro thermal conductivity mechanism.The results show that the thermal conductivity of the nano plate is in the range of 0.03 to 0.1W/(m·K), and the fiber board is 0.055 to 0.25W/(m·K),the thermal conductivity of the two materials both have an upward trend with increasing temperature,the difference is that the thermal conductivity of fiber board began to increase sharply after 300℃, while the nano plate started after 550℃.However,the overall trend of the nano plate was obviously slower than that of the fiber board,and the higher the temperature,the greater the difference.Analysis suggests that the nano-sized particles and internal pores are the key factors that lead to low thermal conductivity of nano plates.

Abstract:The influences of two classical defects on the compressive mechanical properties of honeycombs are investigated in this paper. The numerical results show that the bigger concentrated hole has more significant effects on the mechanical behavior of honeycombs than the smaller scattered holes. The bigger concentrated hole even can change the deformation mechanism of honeycombs. Furthermore, we find that a honeycomb with some filled cells has a higher Young's modulus. At the same time, the buckling stress of a filled elastic honeycomb can be enhanced. But, the plastic collapse stress of a filled elastic-plastic honeycomb may keep unchanged or drop a little.

Abstract:The pipe flange is made of nickel-plated stainless steel tube and aluminum pipe welded by brazing. In the mechanical test process, the weld seam cracks and leads to leakage. Through morphological observation,energy spectrum analysis and metallographic analysis it is considered that 10 to 20 μm Al-Fe intermetallic layer is found in weld interface,flange welds cracking reason should be the weld interface in the welding process of over reaction,which generates brittle metal thick intermetallic layer, and brittle fracture occurred in the welding joint during the mechanical test.

Abstract:The axial electrical resistivity of individual pitch-based carbon fiber of six kinds carbon fibers was measured by a four-probe method.The thermal conductivity values were calculated by different empirical formulas,respectively and the calculated values were compared with the published values.The results show that the thermal conductivity values calculated from the formula λ=1261/ρ are consistent with these pitch-based carbon fibers with thermal conductivity over 600 or less than 300 W/(m·K).For the pitch-based carbon fiber that thermal conductivity is between 300 and 600 W/(m·K),its calculated thermal conductivity based on the formula λ=440000/(100ρ+258)-295 is more accurate.Based on this test, the relationship between the electrical resistivity of individual pitch-based carbon fiber and its thermal conductivity is established as λ=152740/(100ρ+22)-26,which has stronger universality.

Abstract:The main failure types of 1420 Al-Li alloy forgings are component segregation, oxide inclusion and delaying structure failure. Based on the failure analysis results and the research of the whole process of forging production, detecting, storage, and final processing, this article presents nine quality control measures to prevent the failures of the forging, and improve the quality reliability of 1420 Al-Li alloy forgings effectively.