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Chinese Society of Aeronautics and Astronautics
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, doi: 10.11868/j.issn.1005-5053.2022.000059
Abstract:
The two-dimensional finite element microscopic model of NiCoCrAlY/YSZ gradient thermal barrier coating was established by using the representative volume element method to calculate the thermophysical properties of the gradient layer under different composition ratios. The parameter results were extended to the three-dimensional multi-layer solid model to study the thermodynamic properties of the double-layer coating and gradient structured coating under thermal cycling condition. The results show that the elastic modulus, Poisson's ratio, coefficient of thermal expansion and thermal conductivity of the gradient layer are approximately linear with the component proportion of each phase, and the thermal conductivity is also affected by the distribution pattern of each phase. The thermal conductivity is low and the highest value is 2.91 W·m−1·K−1 when the proportion of NiCoCrAlY phase in the gradient layer is below 0.7 at room temperature. Compared with the double-layer coating, the proportion of YSZ in gradient coatings is reduced by 20%, the insulation temperature is reduced by 14%, the radial tensile stress, axial tensile stress, and shear stress of the ceramic surface layer at high temperature are reduced respectively by 47 %, 32 % and 37 %, and the residual stress after cooling is reduced by 50 %. The results are attributed that the gradient of the coating structure can effectively reduce the thermal mismatch stress caused by the difference in the thermal expansion coefficient between coating and substrate. According to the results of coating stress distribution, the coating is inclined to form vertical cracks in the centre region and horizontal cracks near the outer edge of the TC/BC interface.
The two-dimensional finite element microscopic model of NiCoCrAlY/YSZ gradient thermal barrier coating was established by using the representative volume element method to calculate the thermophysical properties of the gradient layer under different composition ratios. The parameter results were extended to the three-dimensional multi-layer solid model to study the thermodynamic properties of the double-layer coating and gradient structured coating under thermal cycling condition. The results show that the elastic modulus, Poisson's ratio, coefficient of thermal expansion and thermal conductivity of the gradient layer are approximately linear with the component proportion of each phase, and the thermal conductivity is also affected by the distribution pattern of each phase. The thermal conductivity is low and the highest value is 2.91 W·m−1·K−1 when the proportion of NiCoCrAlY phase in the gradient layer is below 0.7 at room temperature. Compared with the double-layer coating, the proportion of YSZ in gradient coatings is reduced by 20%, the insulation temperature is reduced by 14%, the radial tensile stress, axial tensile stress, and shear stress of the ceramic surface layer at high temperature are reduced respectively by 47 %, 32 % and 37 %, and the residual stress after cooling is reduced by 50 %. The results are attributed that the gradient of the coating structure can effectively reduce the thermal mismatch stress caused by the difference in the thermal expansion coefficient between coating and substrate. According to the results of coating stress distribution, the coating is inclined to form vertical cracks in the centre region and horizontal cracks near the outer edge of the TC/BC interface.
2022, 42(6): 1 -8
doi: 10.11868/j.issn.1005-5053.2022.000080
Abstract:
As a new high-temperature structural material, Ti2AlNb-based alloy originated from titanium alloy has excellent room temperature toughness, crack resistance, high temperature strength, oxidation resistance and other advantages, showing a broad application prospect in the aerospace field. To study the microstructure transformation mechanism and related kinetics of Ti2AlNb alloy is of great significance to the alloy composition design and process optimization to obtain the required properties. This paper summarizes the research progress and deficiency of the structure transformation and the dynamic mechanism in Ti2AlNb-based alloy, focuses on the research status of the growth kinetics of B2 phase and O phase at home and abroad in recent years, and points out that there is lack of research on the order disorder transformation kinetics, defect density related dynamics of Ti2AlNb-based alloy. In the future, Ti2AlNb-based alloy needs to be combined with gradually comprehensive dynamics research results to establish a theoretical model of microstructure evolution, so as to optimize alloy composition and process to meet more complex and severe service environment.
As a new high-temperature structural material, Ti2AlNb-based alloy originated from titanium alloy has excellent room temperature toughness, crack resistance, high temperature strength, oxidation resistance and other advantages, showing a broad application prospect in the aerospace field. To study the microstructure transformation mechanism and related kinetics of Ti2AlNb alloy is of great significance to the alloy composition design and process optimization to obtain the required properties. This paper summarizes the research progress and deficiency of the structure transformation and the dynamic mechanism in Ti2AlNb-based alloy, focuses on the research status of the growth kinetics of B2 phase and O phase at home and abroad in recent years, and points out that there is lack of research on the order disorder transformation kinetics, defect density related dynamics of Ti2AlNb-based alloy. In the future, Ti2AlNb-based alloy needs to be combined with gradually comprehensive dynamics research results to establish a theoretical model of microstructure evolution, so as to optimize alloy composition and process to meet more complex and severe service environment.
2022, 42(6): 9 -21
doi: 10.11868/j.issn.1005-5053.2022.000074
Abstract:
Under the high-energy particle impingement and cascade effect, different types of radiation damage defects occur in metals. The aggregation and evolution of radiation damage defects can lead to the destruction of the internal structural stability and the deterioration of their properties of metals. Titanium alloy is a promising radiation resistant alloy due to its advantages of light weight, high strength, high temperature resistance and low radiation activity. Aiming at the improvement of the radiation damage resistance, this work summarizes the research progress on the radiation damage defects, the microstructural features and mechanical properties of titanium alloys. In addition, the formation and evolution of radiation damage defects and the influence mechanism of radiation dose, temperature and element species on defect migration and aggregation are analyzed. The microstructure evolution of titanium alloys induced by irradiation and the radiation damage effects such as radiation hardening, radiation embrittlement and radiation creep are discussed. The radiation damage resistance properties of titanium alloys are summarized and evaluated. The existing researches are lack effective methods to inhibit the radiation damage. Finally, the effective strategies to improve the radiation resistance of titanium alloys through composition regulation and interface microstructure design are prospected.
Under the high-energy particle impingement and cascade effect, different types of radiation damage defects occur in metals. The aggregation and evolution of radiation damage defects can lead to the destruction of the internal structural stability and the deterioration of their properties of metals. Titanium alloy is a promising radiation resistant alloy due to its advantages of light weight, high strength, high temperature resistance and low radiation activity. Aiming at the improvement of the radiation damage resistance, this work summarizes the research progress on the radiation damage defects, the microstructural features and mechanical properties of titanium alloys. In addition, the formation and evolution of radiation damage defects and the influence mechanism of radiation dose, temperature and element species on defect migration and aggregation are analyzed. The microstructure evolution of titanium alloys induced by irradiation and the radiation damage effects such as radiation hardening, radiation embrittlement and radiation creep are discussed. The radiation damage resistance properties of titanium alloys are summarized and evaluated. The existing researches are lack effective methods to inhibit the radiation damage. Finally, the effective strategies to improve the radiation resistance of titanium alloys through composition regulation and interface microstructure design are prospected.
2022, 42(6): 22 -32
doi: 10.11868/j.issn.1005-5053.2022.000064
Abstract:
Ti-6Al-4V(TC4) titanium alloy is a kind of α+β type two-phase titanium alloy widely used. However, due to the microscopic defects in additive manufacturing titanium alloy, its mechanical properties are lower than the forging level, and post-treatment is usually required. Therefore, it is necessary to further study the additive manufacturing process and post-treatment of TC4 titanium alloy. In this paper, the microstructure and comprehensive properties of titanium alloy were analyzed by the changes of common process parameters such as energy input power and scanning strategy in the additive manufacturing process, and the influence of other process parameters such as protective gas type, substrate thickness, powder size and other factors in the additive manufacturing process was introduced. The influence of common heat treatment methods after additive manufacturing on its microstructure and mechanical properties was also comprehensively analyzed, and the influence of new post-heat treatment methods, such as vacuum heat treatment and cyclic heat treatment, as well as the influence of multiple post-treatment and comprehensive use of heat treatment were summarized. Generally speaking that the reasonable selection of additive manufacturing process parameters and the application of post-heat treatment method are the basis for obtaining titanium alloy components with excellent performance. The comprehensive use of various heat treatment methods or other post-treatment methods and heat treatment are the effective ways to further improve the performance of titanium alloy components in additive manufacturing. To establish a uniform selection standard for additive manufacturing process parameters and post-processing process is the key to the future development of additive manufacturing.
Ti-6Al-4V(TC4) titanium alloy is a kind of α+β type two-phase titanium alloy widely used. However, due to the microscopic defects in additive manufacturing titanium alloy, its mechanical properties are lower than the forging level, and post-treatment is usually required. Therefore, it is necessary to further study the additive manufacturing process and post-treatment of TC4 titanium alloy. In this paper, the microstructure and comprehensive properties of titanium alloy were analyzed by the changes of common process parameters such as energy input power and scanning strategy in the additive manufacturing process, and the influence of other process parameters such as protective gas type, substrate thickness, powder size and other factors in the additive manufacturing process was introduced. The influence of common heat treatment methods after additive manufacturing on its microstructure and mechanical properties was also comprehensively analyzed, and the influence of new post-heat treatment methods, such as vacuum heat treatment and cyclic heat treatment, as well as the influence of multiple post-treatment and comprehensive use of heat treatment were summarized. Generally speaking that the reasonable selection of additive manufacturing process parameters and the application of post-heat treatment method are the basis for obtaining titanium alloy components with excellent performance. The comprehensive use of various heat treatment methods or other post-treatment methods and heat treatment are the effective ways to further improve the performance of titanium alloy components in additive manufacturing. To establish a uniform selection standard for additive manufacturing process parameters and post-processing process is the key to the future development of additive manufacturing.
2022, 42(6): 33 -47
doi: 10.11868/j.issn.1005-5053.2021.000205
Abstract:
High entropy alloy is defined as an alloy containing four or more main elements. The atomic fraction of the main elements is greater than 5% and not more than 35%, which has excellent properties such as high strength, high wear resistance and high corrosion resistance. Refractory high-entropy alloy is a new type of superalloy designed and developed based on high-entropy alloy of refractory elements, which has broad application prospects in aerospace, petrochemical and other fields, and is expected to replace traditional superalloys. This paper reviews the composition design of refractory high-entropy alloys from the aspects of element selection and addition of trace elements, and its phase composition has single-phase structure and duplex structure, and the preparation method and performance characteristics of refractory high-entropy alloys are studied, and finally gives the problems and challenges faced by refractory high entropy alloys. This review provides a valuable reference for researchers in the component design, microstructure regulation and performance development of refractory high entropy alloys.
High entropy alloy is defined as an alloy containing four or more main elements. The atomic fraction of the main elements is greater than 5% and not more than 35%, which has excellent properties such as high strength, high wear resistance and high corrosion resistance. Refractory high-entropy alloy is a new type of superalloy designed and developed based on high-entropy alloy of refractory elements, which has broad application prospects in aerospace, petrochemical and other fields, and is expected to replace traditional superalloys. This paper reviews the composition design of refractory high-entropy alloys from the aspects of element selection and addition of trace elements, and its phase composition has single-phase structure and duplex structure, and the preparation method and performance characteristics of refractory high-entropy alloys are studied, and finally gives the problems and challenges faced by refractory high entropy alloys. This review provides a valuable reference for researchers in the component design, microstructure regulation and performance development of refractory high entropy alloys.
2022, 42(6): 48 -56
doi: 10.11868/j.issn.1005-5053.2022.000035
Abstract:
Nickel-based superalloy (GH4169) and Si3N4 ceramics were connected by AgCuTi composite active filler and high purity W foil which acts as interlayer. The effects of temperature on the microstructure evolution and mechanical properties of GH4169/ Si3N4 brazed joint were systematically studied. The results show that the effective connection of GH4169/Si3N4 brazed joint can be realized by using AgCuTi+W composite filler. The microstructure of the joint is GH4169/TiNi3+TiCu+TiCu2+Ag(s, s)+Cu(s, s)+W+TiN+Ti5Si3/Si3N4. When the brazing temperature is low, the Ti element in liquid filler diffuses to less of the ceramic interface with the filler, and no obvious reaction layer is formed; when the brazed temperature increases to 880 ℃, Ti is enriched on the ceramic side, forming a thickness of 2 μm TiN and Ti5Si3 reaction layer. At this time, the shear strength of the joint is the highest, reaching 190.9 MPa. With the increase in brazing temperature, the content of Ti-Cu compound, which is a brittle compound, increases and the mechanical properties of the joint are greatly reduced. The fracture results show that during the shear process, the crack initiates in the interlayer, and then diffuses into the Si3N4 ceramic matrix, and finally breaks on the side of Si3N4 ceramic.
Nickel-based superalloy (GH4169) and Si3N4 ceramics were connected by AgCuTi composite active filler and high purity W foil which acts as interlayer. The effects of temperature on the microstructure evolution and mechanical properties of GH4169/ Si3N4 brazed joint were systematically studied. The results show that the effective connection of GH4169/Si3N4 brazed joint can be realized by using AgCuTi+W composite filler. The microstructure of the joint is GH4169/TiNi3+TiCu+TiCu2+Ag(s, s)+Cu(s, s)+W+TiN+Ti5Si3/Si3N4. When the brazing temperature is low, the Ti element in liquid filler diffuses to less of the ceramic interface with the filler, and no obvious reaction layer is formed; when the brazed temperature increases to 880 ℃, Ti is enriched on the ceramic side, forming a thickness of 2 μm TiN and Ti5Si3 reaction layer. At this time, the shear strength of the joint is the highest, reaching 190.9 MPa. With the increase in brazing temperature, the content of Ti-Cu compound, which is a brittle compound, increases and the mechanical properties of the joint are greatly reduced. The fracture results show that during the shear process, the crack initiates in the interlayer, and then diffuses into the Si3N4 ceramic matrix, and finally breaks on the side of Si3N4 ceramic.
2022, 42(6): 57 -64
doi: 10.11868/j.issn.1005-5053.2022.000057
Abstract:
Creep characterization of different diameter silica bar core during directional solidification of the single crystal superalloy was investigated by suspension method. The scanning electron microscope (SEM) was employed to observe the microstructure of the surface and transversal section of crept silica bar. The energy dispersive spectroscopy (EDS) and X-ray diffraction technology were used to analyse and determine the composition of the reaction product. The experimental results show that the crept deformation amount increases with prolonging of creep time and decreasing of the diameter of the silica bar. When the creep time is 60 min, the diameter 0.5 mm silica bar has the largest creep deformation, and the average deformation is 30 mm, while the 2 mm silica bar is 24 mm. The interfacial reaction of SiO2 with C and Al, which are deposited on the silica bar surface due to the elevated temperature and low vacuum, induces the formation of porous layer. The volume fraction of the porous reaction products leads to the different crept deformation amount of different diameter silica bars. The creep deformation amount of silica bars has a linear relationship with the volume fraction of surface reaction products.
Creep characterization of different diameter silica bar core during directional solidification of the single crystal superalloy was investigated by suspension method. The scanning electron microscope (SEM) was employed to observe the microstructure of the surface and transversal section of crept silica bar. The energy dispersive spectroscopy (EDS) and X-ray diffraction technology were used to analyse and determine the composition of the reaction product. The experimental results show that the crept deformation amount increases with prolonging of creep time and decreasing of the diameter of the silica bar. When the creep time is 60 min, the diameter 0.5 mm silica bar has the largest creep deformation, and the average deformation is 30 mm, while the 2 mm silica bar is 24 mm. The interfacial reaction of SiO2 with C and Al, which are deposited on the silica bar surface due to the elevated temperature and low vacuum, induces the formation of porous layer. The volume fraction of the porous reaction products leads to the different crept deformation amount of different diameter silica bars. The creep deformation amount of silica bars has a linear relationship with the volume fraction of surface reaction products.
2022, 42(6): 65 -71
doi: 10.11868/j.issn.1005-5053.2020.000172
Abstract:
The present research investigated the creep properties of the Mg-8Gd-2Y-0.5Zr alloys with different microstructures (as-cast, as-solution, T6 and as-extruded) after creeping at 200 ℃/70 MPa for 100 hours. Effects of the microstructures, including grain size, Mg5(Gd, Y) phase in cast alloy, β′ phase on creep properties were studied. The as-extruded alloy shows the worst creep resistance due to the refined grains caused by dynamic recrystallization resulting from the extrusion process. Although the Mg5(Gd, Y) phase located at the grain boundary can improve the creep properties of the cast alloy in the early stage creep, the precipitates of β′ phase in T6 alloy and those formed during the creep process in as-solution alloy, which can effectively inhibit the dislocation gliding, can be attributed as an important factor in improving the high temperature creep performance of the alloys. Consequently, the alloy after T6 treatment exhibited the lowest creep rate and the as-solution alloy possessed a better creep resistance than that of the cast alloy during the steady-state creep.
The present research investigated the creep properties of the Mg-8Gd-2Y-0.5Zr alloys with different microstructures (as-cast, as-solution, T6 and as-extruded) after creeping at 200 ℃/70 MPa for 100 hours. Effects of the microstructures, including grain size, Mg5(Gd, Y) phase in cast alloy, β′ phase on creep properties were studied. The as-extruded alloy shows the worst creep resistance due to the refined grains caused by dynamic recrystallization resulting from the extrusion process. Although the Mg5(Gd, Y) phase located at the grain boundary can improve the creep properties of the cast alloy in the early stage creep, the precipitates of β′ phase in T6 alloy and those formed during the creep process in as-solution alloy, which can effectively inhibit the dislocation gliding, can be attributed as an important factor in improving the high temperature creep performance of the alloys. Consequently, the alloy after T6 treatment exhibited the lowest creep rate and the as-solution alloy possessed a better creep resistance than that of the cast alloy during the steady-state creep.
2022, 42(6): 72 -80
doi: 10.11868/j.issn.1005-5053.2021.000049
Abstract:
A micro-diffusion phase-field model based on the atom occupancy probability of single lattice point was presented to describe the phase transition process, the heterogeneous interface structure and composition evolution of Ni59Al22V19 medium entropy alloy during phase transformation at atomic scale. It is found that in the early stage of Ni59Al22V19 medium entropy alloy precipitation, L12 and a small amount of ordered phase of DO22 and L10 are precipitated. As the aging process goes on, the coexistence of L12 and DO22 is formed in the aging process and four kinds of heterogeneous interfacial structures are found. At the initial phase of phase transformation, interfacial structures of A play a dominant role. With the growth and decomposition of the ordered phase, the number of interfacial structures of A decreases while the number of interfacial structures of D increases; in the Ni59Al22V19 medium entropy alloy the ordered domain boundaries provide Al atoms for the growth of L12 during the precipitation process until the alloy reaches equilibrium. During the precipitation process, the precipitation mechanism of γ′ phase is compositional ordering and instable decomposition mechanism, and the precipitaion mechanism of phase θ is instable; the interaction potential between Ni-Al first neighbor atoms increases with the increase of the long program parameters and is proportional to the temperature, the incubation period of medium entropy alloy in Ni59Al22V19 becomes longer with the increase of temperature.
A micro-diffusion phase-field model based on the atom occupancy probability of single lattice point was presented to describe the phase transition process, the heterogeneous interface structure and composition evolution of Ni59Al22V19 medium entropy alloy during phase transformation at atomic scale. It is found that in the early stage of Ni59Al22V19 medium entropy alloy precipitation, L12 and a small amount of ordered phase of DO22 and L10 are precipitated. As the aging process goes on, the coexistence of L12 and DO22 is formed in the aging process and four kinds of heterogeneous interfacial structures are found. At the initial phase of phase transformation, interfacial structures of A play a dominant role. With the growth and decomposition of the ordered phase, the number of interfacial structures of A decreases while the number of interfacial structures of D increases; in the Ni59Al22V19 medium entropy alloy the ordered domain boundaries provide Al atoms for the growth of L12 during the precipitation process until the alloy reaches equilibrium. During the precipitation process, the precipitation mechanism of γ′ phase is compositional ordering and instable decomposition mechanism, and the precipitaion mechanism of phase θ is instable; the interaction potential between Ni-Al first neighbor atoms increases with the increase of the long program parameters and is proportional to the temperature, the incubation period of medium entropy alloy in Ni59Al22V19 becomes longer with the increase of temperature.
2022, 42(6): 81 -87
doi: 10.11868/j.issn.1005-5053.2021.000153
Abstract:
Li1.3+xAl0.3-xCoxTi1.7(PO4)3 (x=0, 0.04, 0.08, 0.12) ceramics were prepared by high temperature solid-state method. The effects of Co2+ ion doping content on the morphology, phase, ion conductivity, dielectric property and microwave absorption property were studied. Results show that Li1.3+xAl0.3-xCoxTi1.7(PO4)3 ceramics had cubic grains with relative densities of 90%, and they are single rhombohedral LiTi2(PO4)3 phase without any impurity. Li1.34Al0.26Co0.04Ti1.7(PO4)3 ceramic has the highest ionic conductivity of 1.14×10−3 S·cm−1. A lower valent cation occupying the Ti(Al) site can reduce the coulombic repulsion between Li+ ions and skeleton ions, and appropriate doping content can obtain suitable size of Li+ ions channel. Then, Li+ ion has a minimum activation energy of 0.29 eV, which is easy to generate thermal ion relaxation polarization. Therefore, Li1.34Al0.26Co0.04Ti1.7(PO4)3 ceramic also has the highest complex permittivity, ε' is 12.9-13.7 and ε" is 3.1-3.8. In addition, due to the combined effect of polarization loss and conductance loss, it has the optimum microwave absorption property of an absorption bandwidth covering the whole X-band and a minimum reflection loss of −17.3 dB at 9.67 GHz, which is a potential candidate of high-temperature lightweight microwave absorption material.
Li1.3+xAl0.3-xCoxTi1.7(PO4)3 (x=0, 0.04, 0.08, 0.12) ceramics were prepared by high temperature solid-state method. The effects of Co2+ ion doping content on the morphology, phase, ion conductivity, dielectric property and microwave absorption property were studied. Results show that Li1.3+xAl0.3-xCoxTi1.7(PO4)3 ceramics had cubic grains with relative densities of 90%, and they are single rhombohedral LiTi2(PO4)3 phase without any impurity. Li1.34Al0.26Co0.04Ti1.7(PO4)3 ceramic has the highest ionic conductivity of 1.14×10−3 S·cm−1. A lower valent cation occupying the Ti(Al) site can reduce the coulombic repulsion between Li+ ions and skeleton ions, and appropriate doping content can obtain suitable size of Li+ ions channel. Then, Li+ ion has a minimum activation energy of 0.29 eV, which is easy to generate thermal ion relaxation polarization. Therefore, Li1.34Al0.26Co0.04Ti1.7(PO4)3 ceramic also has the highest complex permittivity, ε' is 12.9-13.7 and ε" is 3.1-3.8. In addition, due to the combined effect of polarization loss and conductance loss, it has the optimum microwave absorption property of an absorption bandwidth covering the whole X-band and a minimum reflection loss of −17.3 dB at 9.67 GHz, which is a potential candidate of high-temperature lightweight microwave absorption material.
2022, 42(6): 88 -96
doi: 10.11868/j.issn.1005-5053.2020.000002
Abstract:
In order to study the effect of opening size and layering ratio on the compression performance, the compression experiments of composite laminates with three opening sizes and ply were carried out. The strains near the opening area were measured by resistance strain gauges. The experimental results show that the larger the opening size, the lower the 0° layer ratio, the higher the strain level at the hole edge, and the smaller the strain distribution gradient, thus the lower the compressive strength of composite laminates with large openings. Then, based on the Puck failure criterion, a progressive damage analysis model of large-opening composite laminates was established to simulate the compression failure process of laminates. The compressive strength and the strain distribution of the hole edge obtained by numerical simulations are in good agreement with the experimental results. The numerical analysis model can effectively predict the compression performance of composite laminates with large openings.
In order to study the effect of opening size and layering ratio on the compression performance, the compression experiments of composite laminates with three opening sizes and ply were carried out. The strains near the opening area were measured by resistance strain gauges. The experimental results show that the larger the opening size, the lower the 0° layer ratio, the higher the strain level at the hole edge, and the smaller the strain distribution gradient, thus the lower the compressive strength of composite laminates with large openings. Then, based on the Puck failure criterion, a progressive damage analysis model of large-opening composite laminates was established to simulate the compression failure process of laminates. The compressive strength and the strain distribution of the hole edge obtained by numerical simulations are in good agreement with the experimental results. The numerical analysis model can effectively predict the compression performance of composite laminates with large openings.
2022, 42(6): 97 -106
doi: 10.11868/j.issn.1005-5053.2021.000193
Abstract:
This paper studies the durability of epoxy resin-based-carbon fiber reinforced polymer (EP-CFRP) under the combined action of aggressive environmental conditions and load. Environmental conditions such as high and low temperature cycles of −40-40 ℃ / −40-25 ℃ and humidity (water immersion and no water) are investigated in an unstressed state or loaded in about 30% or 60% of the initial ultimate load. The results indicate that both of the dual-factor coupling of “high and low temperature cycle-humidity” and the three-factor coupling of “high and low temperature cycle-humidity-load” have a greater impact on the durability of EP-CFRP. The tensile strength varies with the cycle of high and low temperature. The overall increase shows a simulated trend of first decreasing, then increasing, and then decreasing; however, the appearance of the peak and valley values are quite different. Humidity and load level have little effect on the tensile modulus of EP-CFRP The microcracks generated at the interface between the resin matrix and the fiber have been proved to be the main reason for the strength reduction at later stage. The coupling effect of humidity and load promotes the expansion of cracks and exacerbates the damage to EP-CFRP. According to the damage analysis, a non-linear fitting method is used to give the residual strength damage model of EP-CFRP after the coupling action of the three factors “high and low temperature cycle-humidity-load”.
This paper studies the durability of epoxy resin-based-carbon fiber reinforced polymer (EP-CFRP) under the combined action of aggressive environmental conditions and load. Environmental conditions such as high and low temperature cycles of −40-40 ℃ / −40-25 ℃ and humidity (water immersion and no water) are investigated in an unstressed state or loaded in about 30% or 60% of the initial ultimate load. The results indicate that both of the dual-factor coupling of “high and low temperature cycle-humidity” and the three-factor coupling of “high and low temperature cycle-humidity-load” have a greater impact on the durability of EP-CFRP. The tensile strength varies with the cycle of high and low temperature. The overall increase shows a simulated trend of first decreasing, then increasing, and then decreasing; however, the appearance of the peak and valley values are quite different. Humidity and load level have little effect on the tensile modulus of EP-CFRP The microcracks generated at the interface between the resin matrix and the fiber have been proved to be the main reason for the strength reduction at later stage. The coupling effect of humidity and load promotes the expansion of cracks and exacerbates the damage to EP-CFRP. According to the damage analysis, a non-linear fitting method is used to give the residual strength damage model of EP-CFRP after the coupling action of the three factors “high and low temperature cycle-humidity-load”.
2016, 36(4): 89-98
doi: 10.11868/j.issn.1005-5053.2016.4.013
2020, 40(3): 77-94
doi: 10.11868/j.issn.1005-5053.2020.000061
2016, 36(3): 13-19
doi: 10.11868/j.issn.1005-5053.2016.3.003
2015, 35(4): 63-82
doi: 10.11868/j.issn.1005-5053.2015.4.010
2016, 36(3): 79-91
doi: 10.11868/j.issn.1005-5053.2016.3.009
1998, 18(4): 52-61
2006, 26(3): 283-288
2000, 20(1): 55-61
2000, 20(2): 55-63
2002, 22(2): 49-53
2019, 39(6): 1-19
doi: 10.11868/j.issn.1005-5053.2019.000170
2010, 30(4): 92-96
2006, 26(3): 148-151
2009, 29(1): 1-6
2006, 26(3): 244-250
2000, 20(3): 172-177
2001, 21(1): 55-62
2006, 26(3): 226-232
