Abstract:A comprehensive review is presented to introduce the latest progress of mechanical,thermal and electrical properties of graphene/epoxy nano composites，and the application of graphene in carbon fiber/epoxy functional composites.The future perspectives of graphene / epoxy nanocomposites in aerospace filed were concluded.

Abstract:This paper introduces the developments of the two key technologies for in-situ consolidation process applied in thermoplastic composites manufacturing.Meanwhile,several typical astronautic products generated from aforementioned technologies are illustrated too.Finally,the indexes of the key technologies are proposed and the practical problems need to be solved for the in-situ consolidation technologies are summariged.

Abstract:Composite materials" grid structure without skin is the most efficient structure in composite materials grid structure.But compared with other composite materials grid structure,it is more difficult to design and shape. For the purpose of engineering application,this paper considers the problem of process forming,combining qualitative analysis with quantitative analysis.Optimized by five levels of grid form selection,typical structural engineering calculation,finite element optimization calculation, determination of engineering scheme and experimental verification.Finally comprehensive optimal effects is reached in various aspects such as structural form, design calculation,and process molding.It is verified that composite materials grid structure without skin can meet the requrements of engineering application.At the same time, the weak link of process molding is found,which created the conditions for the optimal structure.

Abstract:In order to improve the machined surface quality of CFRP parts and the tool life,the tool structure was optimized.The orthogonal experiment between the tool structure parameters and the machined surface roughness of CFRP parts and the wear of the tool flank were designed.The influence of the tool structure parameters on the surface roughness of CFRP and the tool flank wear were analyzed by the extreme difference analysis.The mathematical models between the tool structure parameters and the surface roughness of CFRP and the tool flank wear were established by the multiple linear regression method.Based on this model,the tool structure parameters were optimized by using firefly algorithm and the verification experiment was carried out.The results show that the influence sequence of the tool structure parameters on the surface roughness of the CFRP workpiece is as follow:the rear angle,the helix angle,the front angle.Within the range of the test parameters,when the rear angle,the helix angle and the front angle increase,the surface roughness decrease,but the degree of reduction are different.The influence sequence of the tool structure parameters on the tool flank wear is in turn:the rear angle,the helix angle,the front angle.When the rear angle of the tool increases,the tool flank wear increases rapidly,and when the helix angle increases,the tool flank wear decreases.When the front angle of the tool increases,the tool flank wear decreases firstly and then increases.The tool structure optimized by firefly algorithm is used to milling the CFRP.The error value between the experiment and the prediction is small.The error value of the surface roughness is only 3%,and the error value of tool flank wear is 7.6%.

Abstract:In order to investigate the fatigue fracture resistance of Si₃N₄ bonded SiC refractory ceramic under the oxidation conditions at high temperature, the relationship between the strength and the size and the strength and the density of the micro-cracks were simulated by the effective field-subdomain model and the thermal-damage breaking model.The results show that the feasible scope of the size between (0 mm, 0.5 mm] and the density of the micro-cracks between (0 m^-2,10⁴ m^-2] can keep the fatigue fracture resistance of these materials under the oxidation conditions at high temperature.The application is good to extend the service life of materials and ensure the safety and stability of equipment operation.

Abstract:For the full-height honeycomb sandwich airfoil of composite panel,the finite element model of the airfoil was created based on MSC.Patran/Nastran.The structure under uniform load was simulated and analyzed.The results show that maximum displacement of the structure is 2.79 mm,and the flexural load is 33.7 kN.At the same time,the structural flexural strain 1 308.6 με is calculated by engineering method.The maximum displacement of the measured airfoil in the static strength test is 2.81 mm. The theoretical and experimental methods are combined to analyze the airfoil of the sandwich structure.The maximum displacement value deviation is about 0.7%,which proves the rationality of the simulation analysis model and provides a reference for the engineering application of this type of structure.

Abstract:To improve the processing properties of benzoxazine for resin transfer moulding(RTM) and high temperature resistance of benzoxazine based composites,acetylene group was used to modify benzoxazine resin.With the participate of acetylene group,the cured benzoxazine resin could have a higher crosslink density ,and the resin would exhibits a lower viscosity.The results shows that the acetylene-functional benzoxazine(AFBA)exhibits a viscosity of 805 mPa·s at 81.5 ℃,and it is suitable for RTM at 110 ℃ with 310 min.According to the DSC results,the curing of AFBA started from 130 ℃ and ended at 208 ℃.The DMA and TGA curves of AFBA/CF composites exhibit a glass transition temperature peak at 411 ℃ and a char yield of 88.6% at 800 ℃.Moreover,the composites retained more than 99% of tensile properties,more than 70% of flexural and interlaminar shear properties and 60.9% of compressive strength at 350 ℃.

Abstract:In order to provide accurate information for the composite material molding process,DMTA was used to investigate the isothermal curing kinetics of domestic TG800 carbon fiber/802 bismaleimide resin prepreg.The gelpoint could be confirmed by apperance of the inflection point of loss modulus "E" under constant temperature scanning.Using the curing reaction rate to define the increasing in storage modulus E′,the growth mode of reaction degree α in different isothermal stage was investigated and the curing kinetics model was established.Hsich’s non-equilibrium thermodynamic fluctuation theory and Avrami equation were used to analysis the activation energy.The results of Hsich’s theory indicated that the activation energy of TG800/802 prepreg is 49.5 kJ/mol.The results of Avrami equation shows that the activation energy at early stage of the isothermal stage is smaller than that in later stage,Besides,the higher isothermal temperature is,the lower activation energy will be.At early stage of 200 ℃ the activation energy of TG800/802 is 78.8 kJ/mol,which is less than 109 kJ/mol in later stage,and it decreases to 32.4 kJ/mol when temperature rises to 240 ℃.According to the calculated results of curing degree in different isothermal stages,the cure cycle “150 ℃/1 h+180 ℃/2 h+200 ℃/4 h” is proved to be feasible,which provides technical support for engineering application of TG800/802 prepreg.

Abstract:Epoxy resin was modified by MWNTs and hot-melt prepreg reinforced by carbon fiber was manufactured.The effects of the modification methods，specifications and contents of MWNTs on rheology characteristic of resin matrix and the mechanical properties of carbon fiber composites were investigated.The results show that the viscosity of modified resin increases more evidently when the diameter of MWNTs is smaller,the difficulties of fabricating process reduce as compatibilizer is put in.The toughening effect of high ratio of MWNTs is better than that of low ratio NWNTs.As the content of MWNT-NH₂(b) increases,the 0°,90° compressive strength,interlaminar shear strength and CAI of carbon fiber/epoxy composites improve primarily and reduce subsequently.When the content of MWNT-NH₂(b) is 2wt%,the above mechanical properties are optimal,and the 0°,90°compressive moduli-enhance gradually.Pull-out and fracture,bridging and crack deflexion are the main action mechanisms of carbon nanotubes in the carbon fiber/epoxy composites.

Abstract:Polyvinylsilsesquioxane(PVSQ) was synthesized with hydrolysis-polycondensation method from vinyltrimethoxysiloxane (VTMS),and the curing mechanism, curing temperature and thermal stability of PVSQ were studied.The results show that PVSQ,which use ethanol as solvent and be curable at 150 ℃,can be used as the matrix of silicone-based ceramifiable composites for thermal protection applications.Combined with ceramifiable fillers (e.g.,TiB₂,mica,etc.),the in-situ ceramization process of PVSQ ceramifiable composites was studied by SEM, EDS and XRD.The results indicate that the weight loss of PVSQ composites is only 0.29wt% to 4.15wt% and the volumetric shrinkage is 5.20vol% to 15.08vol% when annealed at 800 to 1 200 ℃ for 30 min.The in-situ ceramization reaction take place between the ceramifiable fillers and the pyrolytic products of PVSQ at high temperatures,and generate a large amount of glassy phase for matrix bridging, which further leads to the formation of dimensionally-stable ceramic product.

Abstract:Silicon nitride short fibers porous materials were fabricated by using boron nitride as sintering assistant with extraction and filtration method.The optimum sintering system was determined by analyzing the oxidation process of boron nitride and silicon nitride fibers.The microstructure, dielectric properties and compressive properties of different boron nitride content materials were investigated and analyzed. The results show that the oxidation weight of boron nitride increases 20%,the oxidation is obvious on the surface of silicon nitride fiber at 1 200 ℃.Silicon nitride short fibers are adhesived markedly along with increasing of the content of the boron nitride,the test result show the main components of bonding points are silicon dioxide and borosilicate.And with the increase of the density, the dielectric constant of silicon nitride short fibers porous materials increases from 1.36 to 1.62,tanδ increases from 7.8×10^-4 to 9.5×10^-4,the compressive strength of materials under 10% compressive strain improves from 0.58 MPa to 2.03 MPa.

Abstract:In order to find out the strain change law of the composite component under different surface conditions of the tools and their influence on the curing deformation, thermocouple and FBG sensors were used to monitor the temperature and strain of composite components, and the change law of component strain under different tool surface conditions could be obtained.The results show that the use of demoulding cloth can effectively weaken the interface interaction between tool and component, so that the strain of component is very small in the heating stage.And the strain of component with the tool surface condition of three-layer demoulding agent is obviously less than that of one-layer demoulding agent.In the cooling stage,large compressive strain of composites is detected in all three surface conditions.The tool-part interaction force is the largest when there is one layer of releases agent,and the main warping deformation are along the fiber direction after the curing process.

Abstract:In this paper,the two-edged double point angle drill,three-edged double point angle drill and arc-shaped drill were used to drill UD-CFRP under different cutting parameters.The hole entry and exit quality (entrance damage,burr and exit delamination) were analyzed.And the burrs exist angle (α) was used to measure the number of burrs.The experimental results show that the angle α decreases first and then increases with the increase of the feed rate.Taking into account the quality of the entry and exit (burr and delamination factor), the three-edged double point angle drill is most suitable for drilling CFRP.

Abstract:The tests of nuclear magnetic resonance(NMR) and tensile mechanical properties were undertaken, aiming to analyze the correlation between the transverse relaxation time and tensile properties of hydroxyl-terminated polybutadiene(HTPB) inhibitor at different temperature.One-way analysis of variance shows that temperature has a significant influence on transverse relaxation time.Transverse relaxation time increases linearly while the test temperature rises from 30 ℃ to 90 ℃.From 90 ℃ to 130 ℃,transverse relaxation time decreases,then follows by an increase.Within the range from 30 ℃ to 90 ℃,the rise of temperature brings down tensile strength, and makes elongation at break increase.The strength of the material at 100 ℃ is higher than that at 90 ℃, but the elongation is a slight lower.However, raising the temperature from 100 ℃ to 130 ℃,the elongation at break increases drastically while the material loses its strength,due to the influence of complicated chemical reaction and molecular thermal motion.Moreover,both the elongation at break and the tensile strength have the good correlations with transverse relaxation time.Based on that raltionship,the tensile mechanical properties of HTPB inhibitor can be predicted at different transverse relaxation time.

Abstract:According to helium-arc welding characteristics of 2219 aluminum alloy，a real-time visual sensingsystem for welding process was constructed，a clear image of the molten pool was obtained. In order to obtain the sizeparameters of 2219 aluminum alloy helium arc welding pool and to analyze the characteristics of the molten pool，morphological algorithm was adopted. The edge shape of typical molten pool image was extracted and the characteristic dimension of width of molten pool was obtained. The results show that the width feature of the extracted image can reflect the weld size information accurately. The morphological algorithm has high accuracy and fast calculation speed，which can meet the real-time image processing requirements of 2219 aluminum alloy helium arc welding pool.However，different thresholds and structural elements have great influence on image feature extraction.The threshold adaptive algorithm can meet the complex requirements of real-time visual monitoring of weld pool characteristics in engineering.system for welding process was constructed，a clear image of the molten pool was obtained. In order to obtain the sizeparameters of 2219 aluminum alloy helium arc welding pool and to analyze the characteristics of the molten pool，morphological algorithm was adopted. The edge shape of typical molten pool image was extracted and the characteristic dimension of width of molten pool was obtained. The results show that the width feature of the extracted image can reflect the weld size information accurately. The morphological algorithm has high accuracy and fast calculation speed，which can meet the real-time image processing requirements of 2219 aluminum alloy helium arc welding pool.However，different thresholds and structural elements have great influence on image feature extraction.The threshold adaptive algorithm can meet the complex requirements of real-time visual monitoring of weld pool characteristics in engineering.

Abstract:In order to investigate the ballistic impact resistance of hybrid composite laminates,hybrid fiber composite laminates with different areal densities and different layup structures were prepared by autoclave co-cured process by using carbon fiber fabric composite layer or glass fiber fabric composite layer combined with aramid fiber fabric composite layer.Through the ballistic impact performance test,the ballistic limit speed v₅₀ and the ballistic performance indicator(BPI,specific energy absorption of penetration) of the hybrid composite laminates were obtained. The morphology and non-destructive testing results indicate that the failure mode of pure aramid composite laminates and hybrid composite laminates after impact are the same.The surface layer of the laminates is shear failure, the intermediate layer is delamination failure,and the back layer is tensile fracture failure.The interlaminar layer sequence has a great influence on the delamination defect area of the hybrid composite laminate.When the carbon fiber layer is used as the back layer, the defect area of hybrid laminate is 12 863.6 mm ² smaller than that of the glass fiber layer as the back layer which is 17 400.5 mm²;when the aramid layer is used as the back layer, the area of defect of the hybrid composite layer after impact is equivalent to the defect area of the pure aramid composite laminate in the range of 14 151.0 to 14 927.0 mm².The test results show that the hybrid composite material has a great influence on the ballistic impact resistance of the composite laminates. The v50 of the hybrid composite laminates has a certain degree of improvement.The v50 of the glass fiber/aramid composite laminate has an increment from 193.88 to 204.33 m/s compared to the v50 of pure aramid composite laminate.The hybrid fiber composite laminate with carbon fiber layer or glass fiber layer as the surface layer has better ballistic impact resistance, and their BPI is superior to pure aramid composite laminate.The test results have certain guiding significance for the design and application of hybrid fiber composites in ballistic impact.

Abstract:Carbon nanotube film (CNTF) was used as an electric heating element to study the deicing and electrothermal properties of carbon nanotubes(CNTF) on the surface of glass fiber resin matrix composites.SEM result showed that the samples were intertwined by carbon nanotubes with large porosity.The thickness of CNTF was about 14 µm.The XDR results showed that the samples were microcrystalline,poor crystallinity and small amount of impurity.CNTF was electried in air,the rate of heating and the maximum constant temperature increase rapidly with the increase of input voltage.When the input voltage is 5 V,the heating rate of the first 100 s is 0.91 ℃/s and reaches the maximum constant temperature 95 ℃ at 180 s.After four cycles of electrothermal cycling, the surface resistance increased slightly,the mean value was from 2.795 Ω to 3.870 Ω.The CNTF was rapidly burned off at 9 V input voltage.The current carrying limit of CNTF sample is 1.8 A. Deicing is carried out by using its Joule thermal property. The time of 20 g ice falling off the surface of resin matrix glass fiber composite is 240 s.It is proved that it is feasible to deicing by using the electrothermal characteristics of CNTF.

Abstract:Antibacterial and mildew-proof prepregs were prepared by hot melt impregnation.Their mechanical properties,production of combustion,flame retardment,antibacterial and mildew-proof properties were systematicly studied.The results show that the concentration of composite faceplates’ production of combustion(CO,HF,HCl,NO_x,SO₂,HCN) is far below the standard value. It has the outstanding flame retardment property without flame penetration and drippage of melt,since their self-extinguishment time are all 0 s.The mildew-proof level of all the samples is 0 level.Along with the concentration of additives increasing, antibacterial property became stronger while mechanical properties were weaker.When the concentration was higher than 2%,it can meet the standard requirement.To solve the contradiction between mechanical and antibacterial property,faceplates with the same average content of additives while different distributions are designed.Those whose additives distributed on the surface exbihit the best anti-bacterial property.The structural biosafety integration of materials has been successfully achieved.