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1CHALLENGE AND DEVELOPEMENT TRENDS TO FUTURE AERO ENGINE MATERIALS
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2Development of advanced polymer composites
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3Progress on Electrically Conductive Silicone Rubber
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4Review and prospect on developments of cast superalloys
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5Damage characterization and failure analysis in fiber reinforced composites
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6Strengthening mechanisms of metal matrix composites
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7POLYMERS OBTAINED FROM BENZOCYCLOBUTENES
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8Study on In-Plane Anisotropy of 2524 Aluminum Alloy Sheet
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9Investigation on Indentation Creep by Depth Sensing Indentation
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10Control and relief of residual stresses in high-strength aluminum alloy parts for aerospace industry
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11Study on Fatigue Performance of 7075-T651 Aluminum Alloys
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12Development and Application of P/M Superalloy
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13Development of honeycomb cell structure and materials
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14High-temperature polyimide composites and its application in aeronautical engine
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15Progress on Self-Healing Silicon Carbide Ceramic Matrix Composites and Its Applications
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16Progress of Advanced Near Net-Shape Investment Casting Technology of Superalloys
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1Microstructure and mechanical properties of ultra-high strength TiCp/Mg-1.4Zn-2.6Ca-0.5Mn nanocomposite after hot extrusion
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2Resent development in high-entropy alloys and other high-entropy materials
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3Recent Process and Application of Electrochromism
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4Research Process in Plasma Spray Physical Vapor Deposited Thermal Barrier Coatings
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5First-principle Calculations of Mechanical Properties of Al2Cu, Al2CuMg and MgZn2 Intermetallics in High Strength Aluminum Alloys
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6Research Progress and Application Perspectives of 4D Printing
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7Research Progress in Preparation and Crystallization Technologies of Amorphous ITO Film
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8Application and Research Status of Alternative Materials for 3D-printing Technology
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9Effect of Rare Earth Y on Microstructure and Properties of Sn-58Bi Solder Alloy
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10Additive Manufacture of Metamaterials: a Review
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11Research Progress in Cemented Carbide with Co-Ni-Al Composite Binder Phase
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12Novel Ceramic Materials for Thermal Barrier Coatings
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13Effect of Filler Systems on Properties of Fluororubber Vulcanized by Peroxide
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14Research Progress of Metal-Intermetallic Laminated Composites
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15Effect of sintering temperature on microstructure and mechanical behavior of alumina-based ceramic shell by SLS
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162018-02-Catalog
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Available online
, doi: 10.11868/j.issn.1005-5053.2020.000081
Abstract:
SiCf/SiC composites with the polycarbosilane and silicon carbide fiber of different pyrolytic carbon (PyC) interphase thicknesses as the reinforcement phase were fabricated by a polymer impregnation and pyrolysis (PIP) method. And SiC whisker was introduced into the SiCf/SiC composites to further improve its performance. It is found that the mechanical properties of SiCf/SiC composites have outstanding tensile strength, fracture toughness and flexural strength of 192.3 MPa、446.9 MPa and 11.4 MPa·m1/2,, when the PyC interphase thickness is about 230 nm. After the introduction of SiC whisker, into the SiCf/SiC composite matrix, the toughening mechanisms such as whisker pull-out, whisker bridging and crack deflection increase the energy consumption when the crack is transferred in the matrix, and the fracture toughness and bending strength of the composite are increased by 22.9% and 9.1% respectively.
SiCf/SiC composites with the polycarbosilane and silicon carbide fiber of different pyrolytic carbon (PyC) interphase thicknesses as the reinforcement phase were fabricated by a polymer impregnation and pyrolysis (PIP) method. And SiC whisker was introduced into the SiCf/SiC composites to further improve its performance. It is found that the mechanical properties of SiCf/SiC composites have outstanding tensile strength, fracture toughness and flexural strength of 192.3 MPa、446.9 MPa and 11.4 MPa·m1/2,, when the PyC interphase thickness is about 230 nm. After the introduction of SiC whisker, into the SiCf/SiC composite matrix, the toughening mechanisms such as whisker pull-out, whisker bridging and crack deflection increase the energy consumption when the crack is transferred in the matrix, and the fracture toughness and bending strength of the composite are increased by 22.9% and 9.1% respectively.
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Available online
, doi: 10.11868/j.issn.1005-5053.2020.000058
Abstract:
The casting simulation software ProCAST was used to achieve the simulation of the filling and solidification process of the high Nb-TiAl alloy impeller investment casting. The influence of the casting and filling process on the filling and solidification characteristics of alloy melt filling, shrinkage cavity and porosity was studied, and the corresponding process was optimized. The casting test and the non-destructive testing analysis of the casting were carried out, and the anatomical analysis of the casting was performed to verify the distribution of the shrinkage cavity and porosity. The mechanical properties of the impeller at room temperature and high temperature were studied using attached test rods. The results show that ProCAST software is more accurate in predicting shrinkage cavity and porosity of the high Nb-TiAl casting, and the process scheme is optimized by simulation and prediction results to avoid the formation of large shrinkage cavity and porosity in casting, only micro shrinkage cavity less than 22 μm is existed in the final casting. All castings are fully filled, with the tensile strength about 580 MP at room temperature and about 450 MP at high temperature of 850 ℃.
The casting simulation software ProCAST was used to achieve the simulation of the filling and solidification process of the high Nb-TiAl alloy impeller investment casting. The influence of the casting and filling process on the filling and solidification characteristics of alloy melt filling, shrinkage cavity and porosity was studied, and the corresponding process was optimized. The casting test and the non-destructive testing analysis of the casting were carried out, and the anatomical analysis of the casting was performed to verify the distribution of the shrinkage cavity and porosity. The mechanical properties of the impeller at room temperature and high temperature were studied using attached test rods. The results show that ProCAST software is more accurate in predicting shrinkage cavity and porosity of the high Nb-TiAl casting, and the process scheme is optimized by simulation and prediction results to avoid the formation of large shrinkage cavity and porosity in casting, only micro shrinkage cavity less than 22 μm is existed in the final casting. All castings are fully filled, with the tensile strength about 580 MP at room temperature and about 450 MP at high temperature of 850 ℃.
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Available online
, doi: 10.11868/j.issn.1005-5053.2019.000129
Abstract:
In order to study the initiation, propagation and material failure behavior of T800 carbon fiber reinforced composite joint structure with countersunk bolt under load, the quasi-static tensile tests were carried out on the bolt joint structure. The three-dimensional finite element model of the structure was established by using the finite element software ABAQUS. The three-dimensional Hashin failure criterion was used to predict the initial failure of the composite. Based on the progressive damage theory, a new scheme of gradually reducing material stiffness after damage was proposed, and the definition of the material constitutive relation was realized by using the UMAT user subroutine. The numerical analysis of the joint structure of carbon fiber composite countersunk bolt was carried out, and the numerical calculation results were compared with the tensile test results. The results show that the prediction of failure process by the numerical analysis is in good agreement with the experimental results.
In order to study the initiation, propagation and material failure behavior of T800 carbon fiber reinforced composite joint structure with countersunk bolt under load, the quasi-static tensile tests were carried out on the bolt joint structure. The three-dimensional finite element model of the structure was established by using the finite element software ABAQUS. The three-dimensional Hashin failure criterion was used to predict the initial failure of the composite. Based on the progressive damage theory, a new scheme of gradually reducing material stiffness after damage was proposed, and the definition of the material constitutive relation was realized by using the UMAT user subroutine. The numerical analysis of the joint structure of carbon fiber composite countersunk bolt was carried out, and the numerical calculation results were compared with the tensile test results. The results show that the prediction of failure process by the numerical analysis is in good agreement with the experimental results.
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Available online
, doi: 10.11868/j.issn.1005-5053.2020.000124
Abstract:
The effect of stress concentration around the hole easily leads to fatigue failure of aircraft structures, and usually causes catastrophic accidents. In order to elucidate the influence of cold expansion on the fatigue life of AA2024-T351 specimens, fatigue tests of specimens before and after cold expansion were accomplished on high frequency fatigue test machine. Combining the finite element simulation with X-ray diffraction measurement, the evolution of residual stress around the hole was thus investigated. Meanwhile, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to observe the fatigue fracture morphology, fatigue striation and microstructure characteristics, and to explore the influence of microstructure features on fatigue life. Research results show that the cold expansion with 0.4 mm can significantly improve the fatigue resistance of AA2024-T351 specimens, and the fatigue limit can be increased by about 42%.
The effect of stress concentration around the hole easily leads to fatigue failure of aircraft structures, and usually causes catastrophic accidents. In order to elucidate the influence of cold expansion on the fatigue life of AA2024-T351 specimens, fatigue tests of specimens before and after cold expansion were accomplished on high frequency fatigue test machine. Combining the finite element simulation with X-ray diffraction measurement, the evolution of residual stress around the hole was thus investigated. Meanwhile, scanning electron microscope (SEM) and transmission electron microscope (TEM) were employed to observe the fatigue fracture morphology, fatigue striation and microstructure characteristics, and to explore the influence of microstructure features on fatigue life. Research results show that the cold expansion with 0.4 mm can significantly improve the fatigue resistance of AA2024-T351 specimens, and the fatigue limit can be increased by about 42%.
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Available online
, doi: 10.11868/j.issn.1005-5053.2020.000074
Abstract:
In order to study the lightning damage characteristics of CFRP with fastener, this paper established a three-dimensional finite element model of CFRP with fastener and CFRP without fastener, and analyzed the lightning damage morphology of CFRP through electrothermal coupling simulation by finite element software. The lightning current damage test was carried out and the damage characteristics of two kinds of CFRP under different lightning current peaks were compared. The results show that when the peak value of lightning current is low, the surface damage degree of CFRP with fastener is lower than that of CFRP without fastener. As the peak value of the lightning current increases, the longitudinal damage of the CFRP with fasteners gradually increases along the carbon fiber, and eventually exceeds the CFRP without fasteners. The experimental results show that CFRP without fastener appears linear damage on the surface perpendicular to the direction of carbon fibers when lightning struck. The linear damage of CFRP with fastener on the surface perpendicular to the direction of carbon fibers is not obvious.
In order to study the lightning damage characteristics of CFRP with fastener, this paper established a three-dimensional finite element model of CFRP with fastener and CFRP without fastener, and analyzed the lightning damage morphology of CFRP through electrothermal coupling simulation by finite element software. The lightning current damage test was carried out and the damage characteristics of two kinds of CFRP under different lightning current peaks were compared. The results show that when the peak value of lightning current is low, the surface damage degree of CFRP with fastener is lower than that of CFRP without fastener. As the peak value of the lightning current increases, the longitudinal damage of the CFRP with fasteners gradually increases along the carbon fiber, and eventually exceeds the CFRP without fasteners. The experimental results show that CFRP without fastener appears linear damage on the surface perpendicular to the direction of carbon fibers when lightning struck. The linear damage of CFRP with fastener on the surface perpendicular to the direction of carbon fibers is not obvious.
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Available online
, doi: 10.11868/j.issn.1005-5053.2020.000032
Abstract:
The matrix of fiber bundle composite C/SiC was modified by the combination means of precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). The microstructure of SiC matrix fabricated by PIP (PIP-SiC), and the fracture morphologies of the unmodified and modified composites were observed. Meanwhile, the tensile properties of the unmodified and modified composites were tested. The results show that PIP-SiC matrix modification improves the modulus matching between the fiber and matrix of C/SiC composite, and effectively improves the strength, toughness and stability of C/SiC composite. The tensile strength of modified C/SiC composite is slightly higher than that of unmodified C/SiC composite. Furthermore, the Weibull modulus, elongation and fracture work of modified C/SiC composite are 22%, 28% and 20% higher than those of unmodified C/SiC composite, respectively. Meanwhile, the variation coefficient (C.V.) of tensile strength, elongation and fracture work of modified C/SiC composite is 15%, 12% and 5% lower than that of unmodified C/SiC composite.
The matrix of fiber bundle composite C/SiC was modified by the combination means of precursor infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). The microstructure of SiC matrix fabricated by PIP (PIP-SiC), and the fracture morphologies of the unmodified and modified composites were observed. Meanwhile, the tensile properties of the unmodified and modified composites were tested. The results show that PIP-SiC matrix modification improves the modulus matching between the fiber and matrix of C/SiC composite, and effectively improves the strength, toughness and stability of C/SiC composite. The tensile strength of modified C/SiC composite is slightly higher than that of unmodified C/SiC composite. Furthermore, the Weibull modulus, elongation and fracture work of modified C/SiC composite are 22%, 28% and 20% higher than those of unmodified C/SiC composite, respectively. Meanwhile, the variation coefficient (C.V.) of tensile strength, elongation and fracture work of modified C/SiC composite is 15%, 12% and 5% lower than that of unmodified C/SiC composite.
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Available online
, doi: 10.11868/j.issn.1005-5053.2019.000155
Abstract:
In order to analyze the ablation damage law of composite laminates with fasteners subjected to the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was constructed based on the principle of thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results compare the validity of the model. The ablation damage of fastener-containing laminates under different ratios of electrical conductivity, specific heat and thermal conductivity was analyzed. The variation of ablation damage area under different factors was summarized. The results show that the lightning ablation damage of the fastener-containing laminates compared with the fastener-free laminates is more threatening to the safety of civil aircraft. In addition, the electrical conductivity and specific heat of the laminate have a great influence on the ablation area of the laminate containing the fastener. When the two factors are reduced to 1/3, the ablation damage area increases by 211% and 229%, respectively, while the thermal conductivity of the laminate and the properties of the fastener have little effect on the ablation area.
In order to analyze the ablation damage law of composite laminates with fasteners subjected to the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was constructed based on the principle of thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results compare the validity of the model. The ablation damage of fastener-containing laminates under different ratios of electrical conductivity, specific heat and thermal conductivity was analyzed. The variation of ablation damage area under different factors was summarized. The results show that the lightning ablation damage of the fastener-containing laminates compared with the fastener-free laminates is more threatening to the safety of civil aircraft. In addition, the electrical conductivity and specific heat of the laminate have a great influence on the ablation area of the laminate containing the fastener. When the two factors are reduced to 1/3, the ablation damage area increases by 211% and 229%, respectively, while the thermal conductivity of the laminate and the properties of the fastener have little effect on the ablation area.
2021, 41(1): 1 -18
doi: 10.11868/j.issn.1005-5053.2020.000108
Abstract:
As the development of society, the specific energy density of the commercial lithium-ion battery still cannot meet the requirements for practical applications, such as electric vehicles, 3C(computer, communication and consumer electronics) products and energy storage devices. The Li- and Mn-rich cathode materials are expected to be the key electrode materials for high energy density lithium-ion battery due to their high electrochemical capacity (≈250 mAh/g), high operating voltage(≈3.6 V) and low cost. However, several issues and challenges limit their widespread applications for commercial lithium-ion battery, including high irreversible capacity, poor cycle life and fast voltage/capacity fading. In this paper, the latest research progress of Li- and Mn-rich cathode materials is reviewed, with emphasis on material structure, electrochemical reaction mechanism, failure mechanism and modification technology. The results show that ion doping, surface coating, crystal structure regulation and other techniques can significantly improve the electrochemical performance of Li and Mn-rich cathode materials. Finally, the development direction of Li- and Mn-rich cathode materials is prospected.
As the development of society, the specific energy density of the commercial lithium-ion battery still cannot meet the requirements for practical applications, such as electric vehicles, 3C(computer, communication and consumer electronics) products and energy storage devices. The Li- and Mn-rich cathode materials are expected to be the key electrode materials for high energy density lithium-ion battery due to their high electrochemical capacity (≈250 mAh/g), high operating voltage(≈3.6 V) and low cost. However, several issues and challenges limit their widespread applications for commercial lithium-ion battery, including high irreversible capacity, poor cycle life and fast voltage/capacity fading. In this paper, the latest research progress of Li- and Mn-rich cathode materials is reviewed, with emphasis on material structure, electrochemical reaction mechanism, failure mechanism and modification technology. The results show that ion doping, surface coating, crystal structure regulation and other techniques can significantly improve the electrochemical performance of Li and Mn-rich cathode materials. Finally, the development direction of Li- and Mn-rich cathode materials is prospected.
2021, 41(1): 19 -34
doi: 10.11868/j.issn.1005-5053.2020.000067
Abstract:
Carbon fiber reinforced silicon carbide ceramic based (C/SiC) composites are widely used in industrial, aerospace and other fields due to their high strength, hardness and wear resistance. However, C/SiC composites are difficult to be removed and processed. In this paper the common preparation methods of C/SiC composites and the performance characteristics of their materials are reviewed. The traditional machining methods, ultrasonic assisted machining, laser processing and other processing methods of C/SiC composites are summarized. The material removal mechanism, processing precision, common defects and problems in the processing are analyzed. Traditional machining needs further optimization cutting tool materials. Ultrasonic assisted machining needs to explore the coupling mechanism of ultrasonic vibration between the tool and the material, and the mechanism of material removal under vibration. The removal mechanism of 2.5-dimensional and 3-dimensional C/SiC composites by laser processing also needs to be studied. On the basis of these studies, the possibility of high efficiency, precision, stability and non-destructive processing of C/SiC composite materials is explored by further adopting the composite machining method.
Carbon fiber reinforced silicon carbide ceramic based (C/SiC) composites are widely used in industrial, aerospace and other fields due to their high strength, hardness and wear resistance. However, C/SiC composites are difficult to be removed and processed. In this paper the common preparation methods of C/SiC composites and the performance characteristics of their materials are reviewed. The traditional machining methods, ultrasonic assisted machining, laser processing and other processing methods of C/SiC composites are summarized. The material removal mechanism, processing precision, common defects and problems in the processing are analyzed. Traditional machining needs further optimization cutting tool materials. Ultrasonic assisted machining needs to explore the coupling mechanism of ultrasonic vibration between the tool and the material, and the mechanism of material removal under vibration. The removal mechanism of 2.5-dimensional and 3-dimensional C/SiC composites by laser processing also needs to be studied. On the basis of these studies, the possibility of high efficiency, precision, stability and non-destructive processing of C/SiC composite materials is explored by further adopting the composite machining method.
2021, 41(1): 35 -44
doi: 10.11868/j.issn.1005-5053.2020.000089
Abstract:
Gleeble physical simulation technique was employed to investigate the high-temperature flow stress characteristics of the studied spray forming 7055 aluminum alloy. Simultaneously, the Arrhenius constitutive model which couples the parameter of true strain and the BP artificial neural network constitutive model were contrastingly utilized to predict the flow stress behavior of the experimental alloy. The result shows that the flow stress of spray forming 7075 aluminum alloy is significantly affected by deformation parameter, which is negative correlated with deformation temperature and positively correlated with strain rate. Through the comparison of the two models, the average relative error of the Arrhenius constitutive model lies over 2%. And the error of the model tends to increase with the rising temperature. Moreover, the average absolute error and the average relative error reach the maximum at hot processing temperature (around 450 ℃). It is difficult to precisely predict the flow stress characteristics of the alloy. However, BP artificial neural network constitutive model has higher prediction accuracy, the average relative error δ value is only 0.813% and has higher temperature stability.
Gleeble physical simulation technique was employed to investigate the high-temperature flow stress characteristics of the studied spray forming 7055 aluminum alloy. Simultaneously, the Arrhenius constitutive model which couples the parameter of true strain and the BP artificial neural network constitutive model were contrastingly utilized to predict the flow stress behavior of the experimental alloy. The result shows that the flow stress of spray forming 7075 aluminum alloy is significantly affected by deformation parameter, which is negative correlated with deformation temperature and positively correlated with strain rate. Through the comparison of the two models, the average relative error of the Arrhenius constitutive model lies over 2%. And the error of the model tends to increase with the rising temperature. Moreover, the average absolute error and the average relative error reach the maximum at hot processing temperature (around 450 ℃). It is difficult to precisely predict the flow stress characteristics of the alloy. However, BP artificial neural network constitutive model has higher prediction accuracy, the average relative error δ value is only 0.813% and has higher temperature stability.
2021, 41(1): 45 -52
doi: 10.11868/j.issn.1005-5053.2019.000136
Abstract:
The relationship between γ′ phase morphology and γ/γ′ lattice misfit degree in Co-Ti-V superalloy with different Hf and Re contents was studied by observation of microstructure and X-ray diffraction analysis. The EDS is used to analyze the relationship between the distribution behavior of each element and lattice misfit between γ/γ′ of Co-based superalloys. The effect of Hf and Re content on the high temperature compression properties of Co-based superalloys was studied by 1000 ℃ high temperature compression test. The results show that the morphology of γ′ phase shifts from square to spherical, and the lattice misfit between γ/γ′ phase decreases with the increment of Hf content.The morphology of γ′ phase changes from square to long strip, the γ′ phase turns coarse, and the lattice misfit between γ/γ′ phase decreases with the increment of Re content. According to the EDS analysis, Co, Hf and Re are enriched in the γ phase, while the Ti and V are enriched in the γ′ phase. With the increase of Re content, the yield strength and ultimate strength of the alloy are increased. The yield strength and ultimate strength of the alloy are decreased firstly and then increased with the increase of Hf content.
The relationship between γ′ phase morphology and γ/γ′ lattice misfit degree in Co-Ti-V superalloy with different Hf and Re contents was studied by observation of microstructure and X-ray diffraction analysis. The EDS is used to analyze the relationship between the distribution behavior of each element and lattice misfit between γ/γ′ of Co-based superalloys. The effect of Hf and Re content on the high temperature compression properties of Co-based superalloys was studied by 1000 ℃ high temperature compression test. The results show that the morphology of γ′ phase shifts from square to spherical, and the lattice misfit between γ/γ′ phase decreases with the increment of Hf content.The morphology of γ′ phase changes from square to long strip, the γ′ phase turns coarse, and the lattice misfit between γ/γ′ phase decreases with the increment of Re content. According to the EDS analysis, Co, Hf and Re are enriched in the γ phase, while the Ti and V are enriched in the γ′ phase. With the increase of Re content, the yield strength and ultimate strength of the alloy are increased. The yield strength and ultimate strength of the alloy are decreased firstly and then increased with the increase of Hf content.
2021, 41(1): 53 -59
doi: 10.11868/j.issn.1005-5053.2020.000055
Abstract:
The microstructures and mechanical properties of Inconel 718 alloy were analyzed by using 982 ℃ water cooled solid solution bar after repeated solution and re-aging treatment, and compared with direct aging treatment.The effects of repeated solution treatment temperatures ranging from 941 to 1010 ℃ on microstructures and mechanical properties of the alloy were systematically studied. The results show that with the increase of repeated solution temperature, the content of γ′′ phase / δ phase gradually increases / decreases with no obvious change in grain size, leading to an evident improvement on room-temperature hardness, high-temperature tensile strength and stress-rupture life of the alloy. The maximum values of the tensile elongation and the stress rupture ductility are reached at the repeated solution temperature of 982 ℃. As compared to the direct aging treatment condition, there is no apparent change in microstructure and mechanical properties of the alloy aged after the repeated solution treatment at 982℃. On the contrary to the higher repeated solution temperature, the lower repeated temperature produces unfavorable effect on the mechanical properties.
The microstructures and mechanical properties of Inconel 718 alloy were analyzed by using 982 ℃ water cooled solid solution bar after repeated solution and re-aging treatment, and compared with direct aging treatment.The effects of repeated solution treatment temperatures ranging from 941 to 1010 ℃ on microstructures and mechanical properties of the alloy were systematically studied. The results show that with the increase of repeated solution temperature, the content of γ′′ phase / δ phase gradually increases / decreases with no obvious change in grain size, leading to an evident improvement on room-temperature hardness, high-temperature tensile strength and stress-rupture life of the alloy. The maximum values of the tensile elongation and the stress rupture ductility are reached at the repeated solution temperature of 982 ℃. As compared to the direct aging treatment condition, there is no apparent change in microstructure and mechanical properties of the alloy aged after the repeated solution treatment at 982℃. On the contrary to the higher repeated solution temperature, the lower repeated temperature produces unfavorable effect on the mechanical properties.
2021, 41(1): 60 -66
doi: 10.11868/j.issn.1005-5053.2020.000005
Abstract:
In this paper, organosilicone-modified polyurethane was synthesized by the prepolymerization method by using polypropylene glycol and isophorone diisocyanate as the synthetic monomers, and γ-aminopropyltriethoxysilane (KH550) as the silicone source. The modified polyurethane was used as the interlayer to prepare the organic-inorganic glass laminates. The effects of silicone contents on the optical properties, thermomechanical properties, and interfacial adhesion property of the glass laminates were investigated. With the KH550 content increasing, the polymerization degree of polyurethane is decreased, resulting in lower transparency, higher haze and lower surface hardness. The storage modulus of the modified polyurethane is increased at first and then decreased, and the glass transition temperature of hard segments is firstly increased and then decreased. Both reached the maximum value when the additive amount of KH550 is 1%. Using polyurethane adhesive layer as the interlayer of glass laminates, the interfacial shear strength of the unmodified glass laminates is 6.7 MPa, while the interfacial shear strength of glass laminates containing 0.5% KH550 is 7.7 MPa.
In this paper, organosilicone-modified polyurethane was synthesized by the prepolymerization method by using polypropylene glycol and isophorone diisocyanate as the synthetic monomers, and γ-aminopropyltriethoxysilane (KH550) as the silicone source. The modified polyurethane was used as the interlayer to prepare the organic-inorganic glass laminates. The effects of silicone contents on the optical properties, thermomechanical properties, and interfacial adhesion property of the glass laminates were investigated. With the KH550 content increasing, the polymerization degree of polyurethane is decreased, resulting in lower transparency, higher haze and lower surface hardness. The storage modulus of the modified polyurethane is increased at first and then decreased, and the glass transition temperature of hard segments is firstly increased and then decreased. Both reached the maximum value when the additive amount of KH550 is 1%. Using polyurethane adhesive layer as the interlayer of glass laminates, the interfacial shear strength of the unmodified glass laminates is 6.7 MPa, while the interfacial shear strength of glass laminates containing 0.5% KH550 is 7.7 MPa.
2021, 41(1): 67 -73
doi: 10.11868/j.issn.1005-5053.2020.000072
Abstract:
C/C-SiC composites were prepared by precursor transformation method. The microstructure and properties of the samples were analyzed. The effects of silicon infiltration temperature, holding time, vacuum degree and cracking cycle on the density of C/C-SiC composite were studied. The results show that with the increase of siliconizing temperature, the density of the material increases at first, and then decreases rapidly. With the increase of heat preservation time, the density of the material increases rapidly at first, keeps stable for a period of time and then decreases slowly. With the increase of sintering vacuum, degree, the density of the material increases rapidly. With the increase of cracking cycle, the density of the material increases continuously, but the growth rate decreases gradually. After 11 cycles of “impregnation curing cracking” process, the C/C-SiC composite prepared obtained a maximum density of 2.09 g/cm3 and a minimum porosity of 7.6%. At this time, it also has the most excellent comprehensive mechanical properties: bending strength of 468 MPa, tensile strength of 242 MPa, fracture toughness of 19.6 MPa·m1/2 and Vickers hardness of 17.2 GPa.
C/C-SiC composites were prepared by precursor transformation method. The microstructure and properties of the samples were analyzed. The effects of silicon infiltration temperature, holding time, vacuum degree and cracking cycle on the density of C/C-SiC composite were studied. The results show that with the increase of siliconizing temperature, the density of the material increases at first, and then decreases rapidly. With the increase of heat preservation time, the density of the material increases rapidly at first, keeps stable for a period of time and then decreases slowly. With the increase of sintering vacuum, degree, the density of the material increases rapidly. With the increase of cracking cycle, the density of the material increases continuously, but the growth rate decreases gradually. After 11 cycles of “impregnation curing cracking” process, the C/C-SiC composite prepared obtained a maximum density of 2.09 g/cm3 and a minimum porosity of 7.6%. At this time, it also has the most excellent comprehensive mechanical properties: bending strength of 468 MPa, tensile strength of 242 MPa, fracture toughness of 19.6 MPa·m1/2 and Vickers hardness of 17.2 GPa.
2021, 41(1): 74 -82
doi: 10.11868/j.issn.1005-5053.2020.000022
Abstract:
The resin matrix of traditional carbon fiber composite (CFRP) has a high resistivity, which produces a lot of resistance heat and causes damage under the strong current. Strengthening its conductivity can effectively improve the lightning protection performance of CFRP. The particles of the silver powder were added to the resin matrix for conductivity modification, and the influence of silver powder content on lightning protection performance was analyzed by finite element simulation. The optimum content of silver powder in CFRP matrix was determined to be 38%. The conductivity modification effect along the thickness direction was the best, which was improved by 217.3 times. Simulated lightning strikes test was carried out on the modified CFRP laminates with different peak lightning currents of D waveform, and unmodified laminates and the laminates with copper wire mesh on the surface were compared at the same energy level. The damage characteristics and damage area were compared by visual damage observation and perspective ultrasonic scanning to evaluate the lightning resistance of the matrix modified CFRP. The results show that the matrix modification can prevent the surface layer from breakdown and reduce the fiber fracture warping and lamination damage. Under the peak current of 20 kA, 40 kA and 60 kA, the copper wire mesh protection can reduce the lightning damage area by 100%, 86.61% and 37.46%, and the matrix modified overall protection can reduce the lightning damage area by 84.02%, 81.03% and 40.91% respectively.
The resin matrix of traditional carbon fiber composite (CFRP) has a high resistivity, which produces a lot of resistance heat and causes damage under the strong current. Strengthening its conductivity can effectively improve the lightning protection performance of CFRP. The particles of the silver powder were added to the resin matrix for conductivity modification, and the influence of silver powder content on lightning protection performance was analyzed by finite element simulation. The optimum content of silver powder in CFRP matrix was determined to be 38%. The conductivity modification effect along the thickness direction was the best, which was improved by 217.3 times. Simulated lightning strikes test was carried out on the modified CFRP laminates with different peak lightning currents of D waveform, and unmodified laminates and the laminates with copper wire mesh on the surface were compared at the same energy level. The damage characteristics and damage area were compared by visual damage observation and perspective ultrasonic scanning to evaluate the lightning resistance of the matrix modified CFRP. The results show that the matrix modification can prevent the surface layer from breakdown and reduce the fiber fracture warping and lamination damage. Under the peak current of 20 kA, 40 kA and 60 kA, the copper wire mesh protection can reduce the lightning damage area by 100%, 86.61% and 37.46%, and the matrix modified overall protection can reduce the lightning damage area by 84.02%, 81.03% and 40.91% respectively.
2021, 41(1): 83 -90
doi: 10.11868/j.issn.1005-5053.2019.000176
Abstract:
In order to study the ablation damage law of composite laminates with fasteners under the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was established based on thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results were compared with the validity of the model. The ablation damages of fastener-containing laminates under different peak currents, fastener sizes and laminate width ratios were analyzed, and the variations of ablation damage area under different factors were summarized. The results show that the peak current of the lightning strike, the size of the fastener, and the width of the laminate have great influences on the ablation damage areas of the fastener-containing laminates. The same lightning strike current waveform, the ablation damage area caused by lightning current with a peak value of 150 kA is 15.39 times that of 50 kA The smaller the fastener is, the larger the area of ablation damage is, and the larger the area of delamination damage is. Among them, when the diameter of the fastener is reduced by 2 times, the ablation damage area can be increased by 4.97 times, and the delamination damage area can be increased by 1.91 times. The damage area increases first and then decreases with the increase of the width, and finally tends to be stable. The ratio of the largest damage area to the minimum damage area can reach 1.81 times, and the ratio increases with the increase of the fastener diameter.
In order to study the ablation damage law of composite laminates with fasteners under the action of lightning current, the lightning finite element analysis model of fastener-containing laminates was established based on thermoelectric coupling, and the results of lightning ablation damage were analyzed and tested. The results were compared with the validity of the model. The ablation damages of fastener-containing laminates under different peak currents, fastener sizes and laminate width ratios were analyzed, and the variations of ablation damage area under different factors were summarized. The results show that the peak current of the lightning strike, the size of the fastener, and the width of the laminate have great influences on the ablation damage areas of the fastener-containing laminates. The same lightning strike current waveform, the ablation damage area caused by lightning current with a peak value of 150 kA is 15.39 times that of 50 kA The smaller the fastener is, the larger the area of ablation damage is, and the larger the area of delamination damage is. Among them, when the diameter of the fastener is reduced by 2 times, the ablation damage area can be increased by 4.97 times, and the delamination damage area can be increased by 1.91 times. The damage area increases first and then decreases with the increase of the width, and finally tends to be stable. The ratio of the largest damage area to the minimum damage area can reach 1.81 times, and the ratio increases with the increase of the fastener diameter.
2021, 41(1): 91 -100
doi: 10.11868/j.issn.1005-5053.2020.000024
Abstract:
Fatigue and crack growth tests were performed on two categories of the common aeronautic aluminum- alloys 2524-T3 and 7050-T7451 at ambient temperature of 25 ℃ and cryogenic temperature of –70 ℃, in order to investigate the fatigue and crack propagation properties and micro mechanism. The test results show that the cryogenic fatigue life under the same amplitude loading rises and cryogenic crack growth rate decreases, which demonstrates the beneficial effect of cryogenic temperature on fatigue and crack growth properties. Furthermore, the fractographic micro mechanism reveals significant cleavage facets appeared during fatigue crack initiation at the cryogenic temperature of –70 ℃, leading to a concavo-convex morphology on fracture surfaces, and the fatigue crack initiation becomes difficult. On crack growth zones, the fatigue striations and dimples become unobvious, while evident intergranulars are occurred. As a result, the local fatigue crack tends to propagate zigzag and intergranularly, and fatigue and crack growth lives are increased. With the increasing loading stress level, the concavo-convex morphology and ductile transgranulars are reduced, while the fatigue striations and dimples are increased on fatigue surfaces, which demonstrates the cryogenic effect on fatigue crack initiation and propagation becomes weaker. This results have important theoretical and practical value.
Fatigue and crack growth tests were performed on two categories of the common aeronautic aluminum- alloys 2524-T3 and 7050-T7451 at ambient temperature of 25 ℃ and cryogenic temperature of –70 ℃, in order to investigate the fatigue and crack propagation properties and micro mechanism. The test results show that the cryogenic fatigue life under the same amplitude loading rises and cryogenic crack growth rate decreases, which demonstrates the beneficial effect of cryogenic temperature on fatigue and crack growth properties. Furthermore, the fractographic micro mechanism reveals significant cleavage facets appeared during fatigue crack initiation at the cryogenic temperature of –70 ℃, leading to a concavo-convex morphology on fracture surfaces, and the fatigue crack initiation becomes difficult. On crack growth zones, the fatigue striations and dimples become unobvious, while evident intergranulars are occurred. As a result, the local fatigue crack tends to propagate zigzag and intergranularly, and fatigue and crack growth lives are increased. With the increasing loading stress level, the concavo-convex morphology and ductile transgranulars are reduced, while the fatigue striations and dimples are increased on fatigue surfaces, which demonstrates the cryogenic effect on fatigue crack initiation and propagation becomes weaker. This results have important theoretical and practical value.
1998, 18(4): 52-61
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Supported by Beijing Renhe Information Technology Co. LtdTechnical support：info@rhhz.net