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1Research Progress and Application Perspectives of 4D Printing
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2Progress on Self-Healing and Structure-Wave Absorbing Integration of Silicon Carbide Ceramic Matrix Composites
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3Research Progress of Laser Shock Treatment in the Field of Material Forming
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4Effect of Mo content on Microstructure and Mechanical Properties of IN718 Alloy
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5Effect of Rare Earth Y on Microstructure and Properties of Sn-58Bi Solder Alloy
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6Research Progress in Preparation and Crystallization Technologies of Amorphous ITO Film
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72018-04-Catalog
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8Research Progress in Cemented Carbide with Co-Ni-Al Composite Binder Phase
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9Research Process in Plasma Spray Physical Vapor Deposited Thermal Barrier Coatings
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10Novel Ceramic Materials for Thermal Barrier Coatings
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11Research Progress on Preforms of C/C Composites
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12Progress in Amorphous Transparent Conducting Oxide Thin Films
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13Research Progress of Metal-Intermetallic Laminated Composites
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14Thermodynamic Calculation and Analysis of Equilibrium Precipitated Phases in Mar-M247 Superalloy
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15Additive Manufacture of Metamaterials: a Review
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16Thermal post-buckling behavior of ceramic-based FGM circular plates with linear variable thickness
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1Effect of Filler Systems on Properties of Fluororubber Vulcanized by Peroxide
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2First-principle Calculations of Mechanical Properties of Al2Cu, Al2CuMg and MgZn2 Intermetallics in High Strength Aluminum Alloys
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3Research Process in Plasma Spray Physical Vapor Deposited Thermal Barrier Coatings
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4Effect of Rare Earth Y on Microstructure and Properties of Sn-58Bi Solder Alloy
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52018-02-Catalog
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6Current Study and Novel Ideas on Magnesium Matrix Composites
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7High Temperature Titanium Alloys：Status and Perspective
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8Progress in Amorphous Transparent Conducting Oxide Thin Films
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9Research Progress on Deployable Structures of Shape Memory Polymer Composites
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10Research and Application Progress of Silicone Rubber Materials in Aviation
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11Research Progress in Preparation and Crystallization Technologies of Amorphous ITO Film
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12Research Progress in Cemented Carbide with Co-Ni-Al Composite Binder Phase
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13Failure and Protection of Thermal Barrier Coating under CMAS Attack
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14Additive Manufacture of Metamaterials: a Review
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15Research Progress and Application Perspectives of 4D Printing
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16Progress on Self-Healing and Structure-Wave Absorbing Integration of Silicon Carbide Ceramic Matrix Composites
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, doi: 10.11868/j.issn.1005-5053.2014.3.002
Abstract:
The effect of micro phase morphology of bismaleimide (BMI)/polyethersulfone (PES) multi-phase systems on the thermal properties were studied by SEM、DMA and TGA. The SEM results suggest that the phase separation exists in the multi-phase BMI/PES resin. Phase inversion happens with the addition of PES up to 15 phr. SEM shows subtle micro structure with fine BMI-rich particulate phases surrounded by continuous PES-rich phase. The glass transition temperature (Tg) belonging to BMI-rich phase of BMI/PES resin is higher than neat BMI resin. BMI/PES-5 resin system exhibits only one Tg and the temperature corresponding to the decrease of initial modulus increased. Such will be reduced. The high-temperature plastic behavior of BMI/PES resin system is enhanced with the increase of PES. The peak thermal decomposition temperature and char yield of BMI/PES resin are enhanced owing to the excellent interface interaction between BMI and PES as well as the thermal protection effect of PES. The heat resistance of resin systems under N2 atmosphere are superior to systems under air atmosphere.
The effect of micro phase morphology of bismaleimide (BMI)/polyethersulfone (PES) multi-phase systems on the thermal properties were studied by SEM、DMA and TGA. The SEM results suggest that the phase separation exists in the multi-phase BMI/PES resin. Phase inversion happens with the addition of PES up to 15 phr. SEM shows subtle micro structure with fine BMI-rich particulate phases surrounded by continuous PES-rich phase. The glass transition temperature (Tg) belonging to BMI-rich phase of BMI/PES resin is higher than neat BMI resin. BMI/PES-5 resin system exhibits only one Tg and the temperature corresponding to the decrease of initial modulus increased. Such will be reduced. The high-temperature plastic behavior of BMI/PES resin system is enhanced with the increase of PES. The peak thermal decomposition temperature and char yield of BMI/PES resin are enhanced owing to the excellent interface interaction between BMI and PES as well as the thermal protection effect of PES. The heat resistance of resin systems under N2 atmosphere are superior to systems under air atmosphere.
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2019, 39(1): 1 -8
doi: 10.11868/j.issn.1005-5053.2018.001017
Abstract:
Research progress on corrosion behavior (localized corrosion, corrosion type and corrosion products) and the effects of processing methods and alloying on the corrosion resistance of hexagonal close packed (HCP) singular phase, body cubic centered (BCC) singular phase and (HCP+BCC) duplex structured Mg-Li alloys were summarized. The future research directions about how to improve the corrosion resistance of Mg-Li alloys were pointed out and the research on corrosion behavior of Mg-Li alloys should focus on the structure, main components and evolution of surface product layers. Meanwhile, it is necessary to consider the effect of alloying elements on the protective effect of surface film layers, and to study the influence of the crystallographic texture of Mg-Li alloys due to the severe plastic deformation on their corrosion behavior.
Research progress on corrosion behavior (localized corrosion, corrosion type and corrosion products) and the effects of processing methods and alloying on the corrosion resistance of hexagonal close packed (HCP) singular phase, body cubic centered (BCC) singular phase and (HCP+BCC) duplex structured Mg-Li alloys were summarized. The future research directions about how to improve the corrosion resistance of Mg-Li alloys were pointed out and the research on corrosion behavior of Mg-Li alloys should focus on the structure, main components and evolution of surface product layers. Meanwhile, it is necessary to consider the effect of alloying elements on the protective effect of surface film layers, and to study the influence of the crystallographic texture of Mg-Li alloys due to the severe plastic deformation on their corrosion behavior.
2019, 39(1): 9 -16
doi: 10.11868/j.issn.1005-5053.2018.001018
Abstract:
In order to obtain a large modified zone with uniform microstructure and good comprehensive properties, single-side and double-side friction stir processings of Mg-Zn-Y-Nd alloy thick plate were carried out, and the microstructure and properties of the processed plates were studied. The results show that the microstructure of the alloy is obviously refined after friction stir processing. The average grain sizes of the upper, mid and lower samples in the stirring zone after single-side and double-side friction stir processings are 4.45 μm, 5.08 μm,5.30 μm and 3.93 μm, 3.20 μm and 3.19 μm respectively. Compared with the homogenizing annealing alloy and single-side friction stir processed alloy, the microstructure of the double-side friction stir processed alloy is more uniform and fine, and the tensile strength and elongation of the lower stirring zone are the highest, 283.3 MPa and 23.9% respectively, and also the corrosion resistance is the best. The corrosion mode is changed from pitting corrosion to uniform corrosion.
In order to obtain a large modified zone with uniform microstructure and good comprehensive properties, single-side and double-side friction stir processings of Mg-Zn-Y-Nd alloy thick plate were carried out, and the microstructure and properties of the processed plates were studied. The results show that the microstructure of the alloy is obviously refined after friction stir processing. The average grain sizes of the upper, mid and lower samples in the stirring zone after single-side and double-side friction stir processings are 4.45 μm, 5.08 μm,5.30 μm and 3.93 μm, 3.20 μm and 3.19 μm respectively. Compared with the homogenizing annealing alloy and single-side friction stir processed alloy, the microstructure of the double-side friction stir processed alloy is more uniform and fine, and the tensile strength and elongation of the lower stirring zone are the highest, 283.3 MPa and 23.9% respectively, and also the corrosion resistance is the best. The corrosion mode is changed from pitting corrosion to uniform corrosion.
2019, 39(1): 17 -25
doi: 10.11868/j.issn.1005-5053.2018.001019
Abstract:
The titanium-containing oxide film has attracted attention due to the phenomenon of self-sealing pores. The influences of fluorotitanate (K2TiF6), phytic acid (H12Phy) and sodium fluoride(NaF) concentrations as well as final voltage on corrosion resistance of oxide film were investigated by an orthogonal experiment with four factors and three levels. The coating performances were characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electrochemical methods. The results show that the sequence of processing factors on the corrosion resistance of oxide film is H12Phy concentration > NaF concentration > final voltage > K 2TiF6 concentration. Anodic coatings are mainly composed of TiO2, MgF2, Mg2PO4F and Mg2TiO4. Micro-arc oxidation (MAO) coating can significantly improve the corrosion resistance of magnesium alloy. However, with the prolonging of immersion time, the coating corrosion resistance decreases.
The titanium-containing oxide film has attracted attention due to the phenomenon of self-sealing pores. The influences of fluorotitanate (K2TiF6), phytic acid (H12Phy) and sodium fluoride(NaF) concentrations as well as final voltage on corrosion resistance of oxide film were investigated by an orthogonal experiment with four factors and three levels. The coating performances were characterized by using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electrochemical methods. The results show that the sequence of processing factors on the corrosion resistance of oxide film is H12Phy concentration > NaF concentration > final voltage > K 2TiF6 concentration. Anodic coatings are mainly composed of TiO2, MgF2, Mg2PO4F and Mg2TiO4. Micro-arc oxidation (MAO) coating can significantly improve the corrosion resistance of magnesium alloy. However, with the prolonging of immersion time, the coating corrosion resistance decreases.
2019, 39(1): 26 -37
doi: 10.11868/j.issn.1005-5053.2018.001016
Abstract:
A composite coating of magnesium hydroxide/stearic acid on surface of Mg-1Li-1Ca alloy was prepared using vapor diffusion method to improve the corrosion resistance. The surface morphology and chemical composition of the films were characterized by high resolution scanning electron microscopy (HRSEM), Fourier transform infrared spectrometer (FTIR) and X-ray diffraction analysis (XRD). Electrochemical experiments and immersion test were conducted to study corrosion resistance of the obtained composite coating.The formation and degradation mechanisms of the composite coating were proposed.The results show that the magnesium hydroxide coating has a petal-like structure and is well-adhered to the surface of Mg-1Li-1Ca alloy.The stearic acid coating does not change the petal-like structure of the magnesium hydroxide coating. However, the stearic acid can effectively prevent the aggressive medium penetrating into the internal coating due to its low surface energy and good hydrophobicity.The corrosion current density of the magnesium hydroxide/stearic acid (Mg (OH) 2/SA) composite coating (1.45 × 10–7A/cm2) is decreased by two orders of magnitude compared to that of the Mg-1Li-1Ca alloy substrate (2.70 × 10–5 A/cm2), leading to the enhanced corrosion resistance of magnesium alloy.
A composite coating of magnesium hydroxide/stearic acid on surface of Mg-1Li-1Ca alloy was prepared using vapor diffusion method to improve the corrosion resistance. The surface morphology and chemical composition of the films were characterized by high resolution scanning electron microscopy (HRSEM), Fourier transform infrared spectrometer (FTIR) and X-ray diffraction analysis (XRD). Electrochemical experiments and immersion test were conducted to study corrosion resistance of the obtained composite coating.The formation and degradation mechanisms of the composite coating were proposed.The results show that the magnesium hydroxide coating has a petal-like structure and is well-adhered to the surface of Mg-1Li-1Ca alloy.The stearic acid coating does not change the petal-like structure of the magnesium hydroxide coating. However, the stearic acid can effectively prevent the aggressive medium penetrating into the internal coating due to its low surface energy and good hydrophobicity.The corrosion current density of the magnesium hydroxide/stearic acid (Mg (OH) 2/SA) composite coating (1.45 × 10–7A/cm2) is decreased by two orders of magnitude compared to that of the Mg-1Li-1Ca alloy substrate (2.70 × 10–5 A/cm2), leading to the enhanced corrosion resistance of magnesium alloy.
2019, 39(1): 38 -47
doi: 10.11868/j.issn.1005-5053.2017.000186
Abstract:
The development of 3D printing technology, basic principles and technical features are introduced. Several major 3D printing technologies of titanium alloy both at home and abroad are reviewed: selective laser sintering technology (SLS), selective laser melting technology (SLM), laser solid forming technology (LSF), electron beam selective melting technology (EBSM) and electron beam fuse deposition forming technology (EBF3). By comparison, EBSM technology is the most promising 3D printing technology for titanium alloy in the future because of its high efficiency, high accuracy, low cost and no pollution. The cause and detection of defects in the process of forming is an important research focus in the field of 3D printing, and it is also the basis of the realization of the application of 3D printing parts. The classification, harm and cause of the main defects (including spheroidization, cracks, porosity and warpage) in the process of 3D printing for titanium alloy, as well as the nondestructive testing technology commonly used in 3D printing are introduced. And combined with domestic and foreign research situation, the methods to restrain or improve the above defects are discussed. Finally, the prospect of the future development of 3D printing technology for titanium alloy is prospected from the aspects of materials, equipment and testing technology.
The development of 3D printing technology, basic principles and technical features are introduced. Several major 3D printing technologies of titanium alloy both at home and abroad are reviewed: selective laser sintering technology (SLS), selective laser melting technology (SLM), laser solid forming technology (LSF), electron beam selective melting technology (EBSM) and electron beam fuse deposition forming technology (EBF3). By comparison, EBSM technology is the most promising 3D printing technology for titanium alloy in the future because of its high efficiency, high accuracy, low cost and no pollution. The cause and detection of defects in the process of forming is an important research focus in the field of 3D printing, and it is also the basis of the realization of the application of 3D printing parts. The classification, harm and cause of the main defects (including spheroidization, cracks, porosity and warpage) in the process of 3D printing for titanium alloy, as well as the nondestructive testing technology commonly used in 3D printing are introduced. And combined with domestic and foreign research situation, the methods to restrain or improve the above defects are discussed. Finally, the prospect of the future development of 3D printing technology for titanium alloy is prospected from the aspects of materials, equipment and testing technology.
2019, 39(1): 48 -54
doi: 10.11868/j.issn.1005-5053.2018.000098
Abstract:
To analyze the relationship between composition, microstructure and mechanical properties of TA15 titanium alloys, the quasi-static tensile properties and dynamic properties at room temperature of four kinds of TA15 titanium alloys were studied by the electronic universal tensile testing machine and split hopkinson pressure bar (SHPB). The results reveal that the Zr content has little effect on the tensile strength at room temperature, moreover, with the increase of content of main alloy elements Al, V and Mo, the content of primary α phase decreases and the lamella width of secondary α phase is thinner which provide higher strength and lower plasticity. Slight changes in alloy composition have little effect on dynamic mechanical properties within the critical strain rate range. Increasing the content of main alloy elements Al, Zr, V and Mo is beneficial to improve the critical strain rate, at which the alloy has excellent dynamic mechanical properties. For equiaxed TA15 titanium alloys obtained under air cooling condition, the smaller volume fraction of primary α phase and thinner lamella of secondary α phase can improve the tensile strength, critical strain rate and dynamic mechanical properties at room temperature.
To analyze the relationship between composition, microstructure and mechanical properties of TA15 titanium alloys, the quasi-static tensile properties and dynamic properties at room temperature of four kinds of TA15 titanium alloys were studied by the electronic universal tensile testing machine and split hopkinson pressure bar (SHPB). The results reveal that the Zr content has little effect on the tensile strength at room temperature, moreover, with the increase of content of main alloy elements Al, V and Mo, the content of primary α phase decreases and the lamella width of secondary α phase is thinner which provide higher strength and lower plasticity. Slight changes in alloy composition have little effect on dynamic mechanical properties within the critical strain rate range. Increasing the content of main alloy elements Al, Zr, V and Mo is beneficial to improve the critical strain rate, at which the alloy has excellent dynamic mechanical properties. For equiaxed TA15 titanium alloys obtained under air cooling condition, the smaller volume fraction of primary α phase and thinner lamella of secondary α phase can improve the tensile strength, critical strain rate and dynamic mechanical properties at room temperature.
2019, 39(1): 55 -61
doi: 10.11868/j.issn.1005-5053.2018.000085
Abstract:
As one kind of near alpha titanium alloys with excellent mechanical properties, Ti6242 alloy always shows the" dwell fatigue”characteristic, which is similar to other near α or α+β titanium alloys, especially at near room temperature. In this study, the low cycle fatigue and dwell fatigue tests under high load were designed according to the law of dwell fatigue sensitivity rising with the increase of test load. Combining with microstructure observation, mechanical property characterization and failure fracture analysis, the relationship between the microstructure and fracture behavior under high load low cycle fatigue and dwell fatigue tests was analyzed systematically. By summarizing the characteristics of failure fracture under room temperature tensile, high load low cycle fatigue test and high load dwell fatigue test, also comparing the dwell fatigue sensitivity of the Ti6242 alloy in this study with other Ti6242 alloys and other titanium alloys under different loading conditions, it is proved that increasing the fatigue load is a feasible way to characterize the dwell fatigue sensitivity of Ti6242 alloy.
As one kind of near alpha titanium alloys with excellent mechanical properties, Ti6242 alloy always shows the" dwell fatigue”characteristic, which is similar to other near α or α+β titanium alloys, especially at near room temperature. In this study, the low cycle fatigue and dwell fatigue tests under high load were designed according to the law of dwell fatigue sensitivity rising with the increase of test load. Combining with microstructure observation, mechanical property characterization and failure fracture analysis, the relationship between the microstructure and fracture behavior under high load low cycle fatigue and dwell fatigue tests was analyzed systematically. By summarizing the characteristics of failure fracture under room temperature tensile, high load low cycle fatigue test and high load dwell fatigue test, also comparing the dwell fatigue sensitivity of the Ti6242 alloy in this study with other Ti6242 alloys and other titanium alloys under different loading conditions, it is proved that increasing the fatigue load is a feasible way to characterize the dwell fatigue sensitivity of Ti6242 alloy.
2019, 39(1): 62 -69
doi: 10.11868/j.issn.1005-5053.2018.000101
Abstract:
In situ synchrotron radiation was conducted to characterize the aging process of two kinds of WE54 alloys which were subjected to solid solution treatment (T4) and T4 with a subsequent cold rolling deformation (T4-D) respectively. Results of the in situ aging at 300 ℃ show that the strengthening precipitate phase Mg3(Nd, Y) (β1) in T4-D alloy nucleates after aging for 3 min. After aging for 9 min, the intensity of β1 is reduced, and Mg14Nd2Y (β) diffraction peaks are observed, which indicates that β1 is transferred to β. After aging for 36 min, this phase transformation reaches a stable state, and β phase dominates the aging process. For T4 alloy, the nucleation of β1 begins at 6 min, and the transformation from β1 to β begins at 18 min. After the phase transformation, β phase begins to dominate the aging process at 78 min. Ex situ transmission electron microscopy (TEM) is also carried out to observe the detailed distribution of β1 and β. Combining the synchrotron radiation and TEM results, it is found that the pre-deformation promotes the aging process and the formation of netlike precipitations, which enhances the aging strengthening effect.
In situ synchrotron radiation was conducted to characterize the aging process of two kinds of WE54 alloys which were subjected to solid solution treatment (T4) and T4 with a subsequent cold rolling deformation (T4-D) respectively. Results of the in situ aging at 300 ℃ show that the strengthening precipitate phase Mg3(Nd, Y) (β1) in T4-D alloy nucleates after aging for 3 min. After aging for 9 min, the intensity of β1 is reduced, and Mg14Nd2Y (β) diffraction peaks are observed, which indicates that β1 is transferred to β. After aging for 36 min, this phase transformation reaches a stable state, and β phase dominates the aging process. For T4 alloy, the nucleation of β1 begins at 6 min, and the transformation from β1 to β begins at 18 min. After the phase transformation, β phase begins to dominate the aging process at 78 min. Ex situ transmission electron microscopy (TEM) is also carried out to observe the detailed distribution of β1 and β. Combining the synchrotron radiation and TEM results, it is found that the pre-deformation promotes the aging process and the formation of netlike precipitations, which enhances the aging strengthening effect.
2019, 39(1): 70 -78
doi: 10.11868/j.issn.1005-5053.2018.000107
Abstract:
The simple solution and aging treatment processes were adopted to rejuvenate the microstructure of creep damaged DZ411 superalloy. The microstructure evolution of superalloy during rejuvenation process was investigated by OM and SEM, and then the mechanical properties were evaluated by tensile and creep rupture tests. The results show that creep damaged superalloy obtained from interrupted test at the end of secondary stage of creep suffers from the spheroidization and rafting of the prime γ′ phase and vanishing of the secondary γ′ phase, but no creep cavities. It is also found that the solution treatment plays a prime role in dissolution of deformed γ′ phase, and then re-precipitation of fine γ′ phase. The proper solution temperature can effectively avoid incipient melting and recrystallization. The two stages of aging are the dominant procedures of optimizing the size, shape and volume ratio of bimodal size γ′ phase. By the appropriate rejuvenation schedule, the bimodal size γ′ particles with coarse secondary γ′ particles and fine tertiary γ′ particles can be obtained. The average diameters of bimodal size γ′ particles are about 0.38 μm and 0.07 μm, and the volume fraction are 47.5% and 6.5% respectively. Rejuvenation heat treatment can successfully recover the room temperature strength close to that of the original alloy. The creep rupture life and elongation of rejuvenated DZ411 superalloy under condition of 980 ℃/220 MPa are 121 h and 13%, these values are slightly lower than that of the original alloy.
The simple solution and aging treatment processes were adopted to rejuvenate the microstructure of creep damaged DZ411 superalloy. The microstructure evolution of superalloy during rejuvenation process was investigated by OM and SEM, and then the mechanical properties were evaluated by tensile and creep rupture tests. The results show that creep damaged superalloy obtained from interrupted test at the end of secondary stage of creep suffers from the spheroidization and rafting of the prime γ′ phase and vanishing of the secondary γ′ phase, but no creep cavities. It is also found that the solution treatment plays a prime role in dissolution of deformed γ′ phase, and then re-precipitation of fine γ′ phase. The proper solution temperature can effectively avoid incipient melting and recrystallization. The two stages of aging are the dominant procedures of optimizing the size, shape and volume ratio of bimodal size γ′ phase. By the appropriate rejuvenation schedule, the bimodal size γ′ particles with coarse secondary γ′ particles and fine tertiary γ′ particles can be obtained. The average diameters of bimodal size γ′ particles are about 0.38 μm and 0.07 μm, and the volume fraction are 47.5% and 6.5% respectively. Rejuvenation heat treatment can successfully recover the room temperature strength close to that of the original alloy. The creep rupture life and elongation of rejuvenated DZ411 superalloy under condition of 980 ℃/220 MPa are 121 h and 13%, these values are slightly lower than that of the original alloy.
2019, 39(1): 79 -88
doi: 10.11868/j.issn.1005-5053.2018.000045
Abstract:
To study the aeroengine containment capability in high temperature, experiments and numerical simulations of the spherical nosed projectile impacting thin plate under 25 ℃ and 600 ℃ were performed. Experiments were conducted by using a gas gun. Target plates were impacted by bullets with different initial velocities. The effect of temperature and initial velocity on the deformation, failure pattern and energy absorption of the plate were analyzed. The results show that at higher temperature, the deformation of the target plates is greater, the energy absorbed by the target plates is smaller and the critical ballistic velocities are smaller . The petal deformation of the target plate caused by bending is more obvious under 600 ℃. Numerical simulations of the impact were conducted by using an explicit dynamics FE code (LS-DYNA). The Johnson-Cook material model was used to carry out the analysis. The Johnson-Cook material model parameters were obtained by the separated Hopkinson pressure bar (SHPB) experiment at high temperature. The results obtained from the numerical simulations were compared with those from the experiments. Good correlation is found between experiments and numerical simulations.
To study the aeroengine containment capability in high temperature, experiments and numerical simulations of the spherical nosed projectile impacting thin plate under 25 ℃ and 600 ℃ were performed. Experiments were conducted by using a gas gun. Target plates were impacted by bullets with different initial velocities. The effect of temperature and initial velocity on the deformation, failure pattern and energy absorption of the plate were analyzed. The results show that at higher temperature, the deformation of the target plates is greater, the energy absorbed by the target plates is smaller and the critical ballistic velocities are smaller . The petal deformation of the target plate caused by bending is more obvious under 600 ℃. Numerical simulations of the impact were conducted by using an explicit dynamics FE code (LS-DYNA). The Johnson-Cook material model was used to carry out the analysis. The Johnson-Cook material model parameters were obtained by the separated Hopkinson pressure bar (SHPB) experiment at high temperature. The results obtained from the numerical simulations were compared with those from the experiments. Good correlation is found between experiments and numerical simulations.
2019, 39(1): 89 -95
doi: 10.11868/j.issn.1005-5053.2017.000211
Abstract:
Polyacrylonitrile (PAN) precursors with different orientation behaviors were prepared by changing the coagulation bath conditions such as concentration and temperature. The orientation structure of the PAN precursor was determined by the method of sound velocity. X-ray diffraction and optical microscopy were used to investigate the crystalline structure and morphological characterization of nascent fiber, and the correlation between orientation of precursor and structure of nascent fiber was established. The molecular chain orientation ability " a” was defined as the slope of the logarithmic fitting curve of the degree of orientation varying with the drafting ratio, and the relationship between " a” and the crystallinity of nascent fiber was studied. The results show that the higher crystallinity nascent fiber has, the lower drawing ability PAN precursor has, and the higher degree of orientation has under the same drafting ratios. The maximum drafting factor of polyacrylonitrile precursor is significantly affected by radial structure of nascent fiber, it reaches the local maximum when the coagulation bath concentration is 74%. The fiber with high solvent content has higher molecular chain orientation ability than the fiber with low solvent content. The molecular chain orientation ability of precursor increases with the crystallinity of nascent fiber.
Polyacrylonitrile (PAN) precursors with different orientation behaviors were prepared by changing the coagulation bath conditions such as concentration and temperature. The orientation structure of the PAN precursor was determined by the method of sound velocity. X-ray diffraction and optical microscopy were used to investigate the crystalline structure and morphological characterization of nascent fiber, and the correlation between orientation of precursor and structure of nascent fiber was established. The molecular chain orientation ability " a” was defined as the slope of the logarithmic fitting curve of the degree of orientation varying with the drafting ratio, and the relationship between " a” and the crystallinity of nascent fiber was studied. The results show that the higher crystallinity nascent fiber has, the lower drawing ability PAN precursor has, and the higher degree of orientation has under the same drafting ratios. The maximum drafting factor of polyacrylonitrile precursor is significantly affected by radial structure of nascent fiber, it reaches the local maximum when the coagulation bath concentration is 74%. The fiber with high solvent content has higher molecular chain orientation ability than the fiber with low solvent content. The molecular chain orientation ability of precursor increases with the crystallinity of nascent fiber.
2019, 39(1): 96 -101
doi: 10.11868/j.issn.1005-5053.2018.000055
Abstract:
The laminate is essentially bonded together to form the individual laminate by the matrix, any delamination of the laminate must be initiated from a matrix failure. Based on this viewpoint, the initiation of laminate delamination was predicted through analyzing the stresses of the matrix. A three-dimensional finite element method is used to calculate the stress field of a symmetrically laminated plate under an axial load. A convergence study was performed and an average stress method was proposed to solve the singularity problem. Then the internal stresses in the fiber and matrix were determined in terms of the bridging micromechanics model. Finally, a Mohr criterion was used to detect the failure of matrix. T800/914 angle-plied laminates were considered. The results show that this approach is able to correlate reasonably with the available experimental data.
The laminate is essentially bonded together to form the individual laminate by the matrix, any delamination of the laminate must be initiated from a matrix failure. Based on this viewpoint, the initiation of laminate delamination was predicted through analyzing the stresses of the matrix. A three-dimensional finite element method is used to calculate the stress field of a symmetrically laminated plate under an axial load. A convergence study was performed and an average stress method was proposed to solve the singularity problem. Then the internal stresses in the fiber and matrix were determined in terms of the bridging micromechanics model. Finally, a Mohr criterion was used to detect the failure of matrix. T800/914 angle-plied laminates were considered. The results show that this approach is able to correlate reasonably with the available experimental data.
2019, 39(1): 102 -107
doi: 10.11868/j.issn.1005-5053.2017.000035
Abstract:
The governing differential equations of ceramic-based functionally graded material (FGM) circular plate with linear variable thickness along the radius in thermal environment were established. The thermal post-buckling behaviors of variable thickness FGM circular plate made of ceramic and metal in thermal environment were proposed by the method of shooting technique. The characteristic curves of the thermal post-buckling equilibrium paths of the FGM variable thickness circular plate in uniform and non-uniform heating fields are given. The influence of ceramic gradient index and thickness variation coefficient on post buckling behavior is discussed. The numerical results show that the thermal critical load of non-uniform heating field is less than the one under uniform load. The change of radial thickness does not affect the thermal critical load value, but affects the post-buckling equilibrium path. The center deflection increases with the increase of variable thickness coefficient.
The governing differential equations of ceramic-based functionally graded material (FGM) circular plate with linear variable thickness along the radius in thermal environment were established. The thermal post-buckling behaviors of variable thickness FGM circular plate made of ceramic and metal in thermal environment were proposed by the method of shooting technique. The characteristic curves of the thermal post-buckling equilibrium paths of the FGM variable thickness circular plate in uniform and non-uniform heating fields are given. The influence of ceramic gradient index and thickness variation coefficient on post buckling behavior is discussed. The numerical results show that the thermal critical load of non-uniform heating field is less than the one under uniform load. The change of radial thickness does not affect the thermal critical load value, but affects the post-buckling equilibrium path. The center deflection increases with the increase of variable thickness coefficient.
2018, 38(2): 70-76
doi: 10.11868/j.issn.1005-5053.2018.001005
2018, 38(6): 1-10
doi: 10.11868/j.issn.1005-5053.2018.000081
2018, 38(4): 64-74
doi: 10.11868/j.issn.1005-5053.2018.000025
2018, 38(4): 101-108
doi: 10.11868/j.issn.1005-5053.2018.000007
2018, 38(5): 24-35
doi: 10.11868/j.issn.1005-5053.2018.000035
2018, 38(5): 47-58
doi: 10.11868/j.issn.1005-5053.2018.000022
2018, 38(2): 1-9
doi: 10.11868/j.issn.1005-5053.2018.001008
2018, 38(2): 10-20
doi: 10.11868/j.issn.1005-5053.2018.001001
2018, 38(2): 86-95
doi: 10.11868/j.issn.1005-5053.2017.000010
2018, 38(1): 1-16
doi: 10.11868/j.issn.1005-5053.2017.000042
2018, 38(4): 37-46
doi: 10.11868/j.issn.1005-5053.2017.000204
2018, 38(3): 10-19
doi: 10.11868/j.issn.1005-5053.2018.001009
2019, 39(1): 102-107
doi: 10.11868/j.issn.1005-5053.2017.000035
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