2023 Vol. 40, No. 6
2023, 40(6): 3075-3089.
doi: 10.13801/j.cnki.fhclxb.20230227.004
Abstract:
Thermal structural components made of continuous fibre-reinforced silicon carbide ceramic matrix composites (CMC-SiC) have been widely employed in aerospace and aeronautical fields. Integrated manufacturing techniques have been also extensively utilized to assembly CMC-SiC parts together to form large and complex components. The development of novel high-performance CMC-SiC fasteners has become critical manufacturing technology. In this work, different types, preparation methods, and microstructural characteristics of CMC-SiC fasteners were reviewed based on unique demands in terms of component preparation. It is demonstrated that shear strength of fasteners was very similar to in-plane shear strength of composites. Tensile and shear behaviours, load distribution among fasteners, failure mechanisms, and oxidation damages of CMC-SiC bolted/pinned joints were summarized. Furthermore, vibration relaxation mechanism and related anti-loosening effect were discussed. Accordingly, an optimization of CMC-SiC fasteners was proposed based on fibre architecture design, preparation process, and fastener structure. In the last, the development of CMC fastener manufacturing and their joining perfor-mance was prospected.
Thermal structural components made of continuous fibre-reinforced silicon carbide ceramic matrix composites (CMC-SiC) have been widely employed in aerospace and aeronautical fields. Integrated manufacturing techniques have been also extensively utilized to assembly CMC-SiC parts together to form large and complex components. The development of novel high-performance CMC-SiC fasteners has become critical manufacturing technology. In this work, different types, preparation methods, and microstructural characteristics of CMC-SiC fasteners were reviewed based on unique demands in terms of component preparation. It is demonstrated that shear strength of fasteners was very similar to in-plane shear strength of composites. Tensile and shear behaviours, load distribution among fasteners, failure mechanisms, and oxidation damages of CMC-SiC bolted/pinned joints were summarized. Furthermore, vibration relaxation mechanism and related anti-loosening effect were discussed. Accordingly, an optimization of CMC-SiC fasteners was proposed based on fibre architecture design, preparation process, and fastener structure. In the last, the development of CMC fastener manufacturing and their joining perfor-mance was prospected.
2023, 40(6): 3090-3114.
doi: 10.13801/j.cnki.fhclxb.20230117.007
Abstract:
Whereas mechanics theories for isotropic materials have been nearly matured, essentially only the linear elasticity theories for anisotropic composite materials are well established. All of the other mechanical behaviors of the composites are not well understood. Specifically, the failure and strength analysis for the composites still remains to be one of the greatest challenges in solid mechanics. During the last 25 years, in order to advance the development in the mechanics of composite materials, this author has established a series of analytical theories. They include the constitutive and internal stress calculation theory, named Bridging Model, for composites reinforced with continuous or short fibers or particles, the true stress theory for converting a homogenized stress of the matrix in a composite into a true value, the failure criteria for matrix failures established on a physics based principle, the interlaminar matrix stress modification method for predicting interlaminar fracture or delamination of any laminated structure, and the incremental constitutive relation for hyperelastic materials. Based on these theories, almost all of the failure problems of two-phase composites can be efficiently resolved through analytical formulae, as long as void contents in the composites can be neglected. Amongst, Bridging Model has been known world-widely, and more than 250 publications have been made by people other than the author’s group using Bridging Model as a theoretical tool. Furthermore, the others’ publications based on the matrix true stress theory have reached a number of 20, although this theory has been established only recently by the author. A brief summary on the establishment of the author’s theories and how to apply them to resolve challenging problems in composites and their structures is presented in the paper.
Whereas mechanics theories for isotropic materials have been nearly matured, essentially only the linear elasticity theories for anisotropic composite materials are well established. All of the other mechanical behaviors of the composites are not well understood. Specifically, the failure and strength analysis for the composites still remains to be one of the greatest challenges in solid mechanics. During the last 25 years, in order to advance the development in the mechanics of composite materials, this author has established a series of analytical theories. They include the constitutive and internal stress calculation theory, named Bridging Model, for composites reinforced with continuous or short fibers or particles, the true stress theory for converting a homogenized stress of the matrix in a composite into a true value, the failure criteria for matrix failures established on a physics based principle, the interlaminar matrix stress modification method for predicting interlaminar fracture or delamination of any laminated structure, and the incremental constitutive relation for hyperelastic materials. Based on these theories, almost all of the failure problems of two-phase composites can be efficiently resolved through analytical formulae, as long as void contents in the composites can be neglected. Amongst, Bridging Model has been known world-widely, and more than 250 publications have been made by people other than the author’s group using Bridging Model as a theoretical tool. Furthermore, the others’ publications based on the matrix true stress theory have reached a number of 20, although this theory has been established only recently by the author. A brief summary on the establishment of the author’s theories and how to apply them to resolve challenging problems in composites and their structures is presented in the paper.
2023, 40(6): 3115-3124.
doi: 10.13801/j.cnki.fhclxb.20221020.001
Abstract:
The increasing scarcity of freshwater resources has become a serious global problem. In order to promote the development of interfacial photothermal steam generation systems and the application of carbon-based fibrous materials in the field of interfacial steam generation. This paper reviews the latest research progress on carbon-based fibrous materials for interfacial photothermal steam generation. Firstly, the design principle of the interfacial steam generation system is introduced, followed by the systematic analysis of the photothermal conversion mechanism and structural characteristics of different carbon-based materials, as well as the performance advantages of fibrous materials applied to steam generation. With different carbon-based fiber materials as the entry point, the preparation methods and performance advantages of carbon-based fiber materials are elaborated. Finally, the challenges faced by carbon-based fibrous materials in the field of interfacial photothermal steam generation are explored.
The increasing scarcity of freshwater resources has become a serious global problem. In order to promote the development of interfacial photothermal steam generation systems and the application of carbon-based fibrous materials in the field of interfacial steam generation. This paper reviews the latest research progress on carbon-based fibrous materials for interfacial photothermal steam generation. Firstly, the design principle of the interfacial steam generation system is introduced, followed by the systematic analysis of the photothermal conversion mechanism and structural characteristics of different carbon-based materials, as well as the performance advantages of fibrous materials applied to steam generation. With different carbon-based fiber materials as the entry point, the preparation methods and performance advantages of carbon-based fiber materials are elaborated. Finally, the challenges faced by carbon-based fibrous materials in the field of interfacial photothermal steam generation are explored.
2023, 40(6): 3125-3135.
doi: 10.13801/j.cnki.fhclxb.20230119.001
Abstract:
In recent years, with the vigorous development of new energy industry, the contradiction between the supply and demand of lithium materials has intensified, and the rational development and utilization of lithium resources are gradually becoming key factors in the development of new energy in China. Salt lake brine is gradually becoming the development direction of China's lithium extraction industry due to its low cost and abundant reserves. Two-dimensional (2D) materials refer to materials in which electrons can only move in two dimensions on a non-nanometer scale (1-100 nm). 2D nanomaterials have received extensive attention in the scientific community due to their special lamellar structure at the atomic scale, high specific surface area, good mechanical strength, rich active sites and good modifiability. This article summarizes the applications of 2D materials as adsorbents and membrane separation materials for lithium extraction in terms of their characteristics, and also points out the current problems and future development trends. This review provides references for the research and application of 2D materials in the field of lithium extraction from salt lake.
In recent years, with the vigorous development of new energy industry, the contradiction between the supply and demand of lithium materials has intensified, and the rational development and utilization of lithium resources are gradually becoming key factors in the development of new energy in China. Salt lake brine is gradually becoming the development direction of China's lithium extraction industry due to its low cost and abundant reserves. Two-dimensional (2D) materials refer to materials in which electrons can only move in two dimensions on a non-nanometer scale (1-100 nm). 2D nanomaterials have received extensive attention in the scientific community due to their special lamellar structure at the atomic scale, high specific surface area, good mechanical strength, rich active sites and good modifiability. This article summarizes the applications of 2D materials as adsorbents and membrane separation materials for lithium extraction in terms of their characteristics, and also points out the current problems and future development trends. This review provides references for the research and application of 2D materials in the field of lithium extraction from salt lake.
2023, 40(6): 3136-3152.
doi: 10.13801/j.cnki.fhclxb.20230119.004
Abstract:
Carbon fiber composites have good electrical conductivity, however, the electrical conductivity of the resin matrix composites is significantly related to reinforcement architectures. The structural deformation under external load triggers the modification in the conductive behavior of carbon fiber composites, which has an important application in smart sensors. Based on the utilization of electrical resistance method in structural health monitoring for composites, this paper focuses on the overview of electrical conductivity and predictive models, surface potential field distribution and main measurement technologies, as well as electromechanical coupling behavior and constitutive models of carbon fiber reinforced resin matrix composites with different dimensional architectures. It is expected to provide a new direction and path to design "material-structure-performance" integrated system in carbon fiber composites.
Carbon fiber composites have good electrical conductivity, however, the electrical conductivity of the resin matrix composites is significantly related to reinforcement architectures. The structural deformation under external load triggers the modification in the conductive behavior of carbon fiber composites, which has an important application in smart sensors. Based on the utilization of electrical resistance method in structural health monitoring for composites, this paper focuses on the overview of electrical conductivity and predictive models, surface potential field distribution and main measurement technologies, as well as electromechanical coupling behavior and constitutive models of carbon fiber reinforced resin matrix composites with different dimensional architectures. It is expected to provide a new direction and path to design "material-structure-performance" integrated system in carbon fiber composites.
2023, 40(6): 3153-3166.
doi: 10.13801/j.cnki.fhclxb.20230119.003
Abstract:
With the rapid development of electronic information technology, higher requirements for the flexibility and optical transparency of electromagnetic shielding materials are put forward in the fields of national defense and military industry, electronic communication, and wearable electronics. Developing high-performance electromagnetic shielding materials with high transparency and flexibility has become a hot research topic. This paper introduced the research progress of polymer-based flexible and transparent electromagnetic shielding composite materials in recent years. The types of polymer substrates and shielding materials, and preparation methods of composite materials were compared and summarized. The mutual restriction problems and solutions of different materials' flexibility, transparency, and electromagnetic shielding properties were expounded. The future development direction of polymer-based flexible and transparent electromagnetic shielding composite materials has prospected.
With the rapid development of electronic information technology, higher requirements for the flexibility and optical transparency of electromagnetic shielding materials are put forward in the fields of national defense and military industry, electronic communication, and wearable electronics. Developing high-performance electromagnetic shielding materials with high transparency and flexibility has become a hot research topic. This paper introduced the research progress of polymer-based flexible and transparent electromagnetic shielding composite materials in recent years. The types of polymer substrates and shielding materials, and preparation methods of composite materials were compared and summarized. The mutual restriction problems and solutions of different materials' flexibility, transparency, and electromagnetic shielding properties were expounded. The future development direction of polymer-based flexible and transparent electromagnetic shielding composite materials has prospected.
2023, 40(6): 3167-3186.
doi: 10.13801/j.cnki.fhclxb.20221014.002
Abstract:
The increasing popularity of electronic devices has aggravated the problem of electromagnetic wave pollution, and the development of electromagnetic wave absorbing materials can not only protect the human body and precision equipment from electromagnetic wave interference, but also reduce the secondary pollution of electromagnetic waves, which has great research significance in both civil and military applications. MXene is a novel two-dimensional nanosheet material with graphene-like structure, which has a large aspect ratio, adjustable conductivity and abundant functional groups, and can be used to study high-performance electromagnetic wave absorbing materials. This paper reviews the chemical composition of MXene and its research progress in the field of wave absorption, introduces the loss mechanism of absorbing materials in detail, and summarizes and analyzes MXene-based composite absorbing materials from microstructure and macroscopic morphology respectively, and finally gives an outlook on the future development direction of MXene and its composite absorbing materials in terms of loss mechanism, structure and multifunction.
The increasing popularity of electronic devices has aggravated the problem of electromagnetic wave pollution, and the development of electromagnetic wave absorbing materials can not only protect the human body and precision equipment from electromagnetic wave interference, but also reduce the secondary pollution of electromagnetic waves, which has great research significance in both civil and military applications. MXene is a novel two-dimensional nanosheet material with graphene-like structure, which has a large aspect ratio, adjustable conductivity and abundant functional groups, and can be used to study high-performance electromagnetic wave absorbing materials. This paper reviews the chemical composition of MXene and its research progress in the field of wave absorption, introduces the loss mechanism of absorbing materials in detail, and summarizes and analyzes MXene-based composite absorbing materials from microstructure and macroscopic morphology respectively, and finally gives an outlook on the future development direction of MXene and its composite absorbing materials in terms of loss mechanism, structure and multifunction.
2023, 40(6): 3187-3196.
doi: 10.13801/j.cnki.fhclxb.20221205.001
Abstract:
Manganese dioxide (MnO2) is a promising electrode material for supercapacitors with the advantages of high capacity, environmental protection and low cost. With the continuous development of smart wearable technology, fiber supercapacitors have attracted wide attention due to their flexibility and stitchability. The combination of MnO2 and fiber supercapacitors as an important part of wearable technology has also been constantly researched and expanded. According to the current development of MnO2 based fiber supercapacitor and the demand of wearable energy products, in this paper, the energy storage mechanism of MnO2 in neutral electrolyte is analyzed. In this paper, a series of solutions are proposed to solve the problems of MnO2 based fiber supercapacitors in practical wearable applications, such as the difficulty of continuous production and low practical utilization rate. At the same time, the advantages and disadvantages of various solutions and the synergistic effect of materials in the solutions are deeply analyzed, which provides new ideas for future research directions. Finally, the challenges and future development of MnO2 based fiber supercapacitor are summarized. MnO2 based fiber supercapacitor is expected to make great progress in the future and become a new generation of energy textiles supply system.
Manganese dioxide (MnO2) is a promising electrode material for supercapacitors with the advantages of high capacity, environmental protection and low cost. With the continuous development of smart wearable technology, fiber supercapacitors have attracted wide attention due to their flexibility and stitchability. The combination of MnO2 and fiber supercapacitors as an important part of wearable technology has also been constantly researched and expanded. According to the current development of MnO2 based fiber supercapacitor and the demand of wearable energy products, in this paper, the energy storage mechanism of MnO2 in neutral electrolyte is analyzed. In this paper, a series of solutions are proposed to solve the problems of MnO2 based fiber supercapacitors in practical wearable applications, such as the difficulty of continuous production and low practical utilization rate. At the same time, the advantages and disadvantages of various solutions and the synergistic effect of materials in the solutions are deeply analyzed, which provides new ideas for future research directions. Finally, the challenges and future development of MnO2 based fiber supercapacitor are summarized. MnO2 based fiber supercapacitor is expected to make great progress in the future and become a new generation of energy textiles supply system.
2023, 40(6): 3197-3217.
doi: 10.13801/j.cnki.fhclxb.20221104.002
Abstract:
Three-dimensional (3D) textile composites have the advantages of excellent mechanical properties, designability, and near-net shape, and are regarded as ideal candidates for key components of aviation and aerospace vehicles. The mechanical properties of machining connection of 3D textile composites are the key guarantee in the reliable service. However, the theoretical research in this area is still very weak. Based on the requirements of the major engineering applications such as aerospace and deep sea, this paper focuses on the overview of the connection methods and processes of 3D textile composite materials and structures. Also, the non-destructive testing technologies are presented. Then, the mapping relationships between processing connection and mechanical properties are clarified, and the key issues on processing connection and mechanical properties of 3D textile composites are proposed. It is expected to provide a basis to design and manufacture 3D textile composites with the high-load-bearing and high-reliability for a better applications.
Three-dimensional (3D) textile composites have the advantages of excellent mechanical properties, designability, and near-net shape, and are regarded as ideal candidates for key components of aviation and aerospace vehicles. The mechanical properties of machining connection of 3D textile composites are the key guarantee in the reliable service. However, the theoretical research in this area is still very weak. Based on the requirements of the major engineering applications such as aerospace and deep sea, this paper focuses on the overview of the connection methods and processes of 3D textile composite materials and structures. Also, the non-destructive testing technologies are presented. Then, the mapping relationships between processing connection and mechanical properties are clarified, and the key issues on processing connection and mechanical properties of 3D textile composites are proposed. It is expected to provide a basis to design and manufacture 3D textile composites with the high-load-bearing and high-reliability for a better applications.
2023, 40(6): 3218-3234.
doi: 10.13801/j.cnki.fhclxb.20230103.002
Abstract:
Thermal energy plays an indispensable role in social activities and can be transformed among various energy sources. Transition metal compound (TMC) enables the efficient conversion of light, electrical and magnetic energy into thermal energy due to the competition and coexistence between its strongly correlated electronic systems and inherent charge, spin, orbital and other degree of freedom and ordered phase. However, used in the form of powder and crystal, TMC owns the problems of oxidation polymerization, volume change, high heat dissipation and collection difficulties, which limits its heat conversion efficiency. Wood has natural hierarchical pore structure and could supply stable mechanical support for TMC. TMC can be uniformly loaded into wood micro-nano surfaces or porous structures by forming covalent bond, ionic bond, hydrogen bond, van der Waals forces with the chemical components of the wood to form TMC@wood composite materials. In addition, wood's excellent thermal management ability can regulate thermal energy to improve heat conversion efficiency. Based on the lign-cellulosic macromolecular network configuration of wood, we discussed the combination method and interfacial binding mechanism of TMC with raw wood, delignification wood and carbonized wood. We further discussed the thermal transformation mechanisms of non-radiative relaxation, relaxation loss and metal-insulator transition of TMC, the functional applications of TMC@wood composite materials in the fields of desalination, oil-water separation, building energy conservation and fire warning are presented. Finally, in view of providing ideas for advanced functionalization and energy conversion of wood, the current advantages and challenges of thermal conversion of TMC@wood are summarized.
Thermal energy plays an indispensable role in social activities and can be transformed among various energy sources. Transition metal compound (TMC) enables the efficient conversion of light, electrical and magnetic energy into thermal energy due to the competition and coexistence between its strongly correlated electronic systems and inherent charge, spin, orbital and other degree of freedom and ordered phase. However, used in the form of powder and crystal, TMC owns the problems of oxidation polymerization, volume change, high heat dissipation and collection difficulties, which limits its heat conversion efficiency. Wood has natural hierarchical pore structure and could supply stable mechanical support for TMC. TMC can be uniformly loaded into wood micro-nano surfaces or porous structures by forming covalent bond, ionic bond, hydrogen bond, van der Waals forces with the chemical components of the wood to form TMC@wood composite materials. In addition, wood's excellent thermal management ability can regulate thermal energy to improve heat conversion efficiency. Based on the lign-cellulosic macromolecular network configuration of wood, we discussed the combination method and interfacial binding mechanism of TMC with raw wood, delignification wood and carbonized wood. We further discussed the thermal transformation mechanisms of non-radiative relaxation, relaxation loss and metal-insulator transition of TMC, the functional applications of TMC@wood composite materials in the fields of desalination, oil-water separation, building energy conservation and fire warning are presented. Finally, in view of providing ideas for advanced functionalization and energy conversion of wood, the current advantages and challenges of thermal conversion of TMC@wood are summarized.
2023, 40(6): 3235-3254.
doi: 10.13801/j.cnki.fhclxb.20220915.002
Abstract:
Fibre-reinforced resin matrix composites are widely used in military/civilian aircraft due to their high specific strength/modulus and good fatigue/corrosion resistance. To avoid damage such as fibre breakage, matrix cracking and delamination caused by riveting/bolting, gluing is often used. Contamination of the adhesive interface, unevenness/ageing of the adhesive can lead to "kissing" and "weak bonding" problems, which cannot be detected and assessed by existing non-destructive testing techniques such as ultrasonic and infrared, and have become a safety hazard for composite structures. Laser bond inspection (LBI) is a new type of inspection technology that uses the mechanical effect of laser shock waves to reflect tensile waves for quantitative assessment of interface bond strength. It can effectively solve the problem of "kissing" and "weak bonding". This paper introduces the technical principles, characteristics and applications of laser shock wave interface bond strength testing; Summarises the progress of domestic and international research and the key issues to be solved from four aspects: Pulsed laser induced shock wave characteristics, shock wave propagation law and dynamic response of materials, laser shock layer cracking and damage characteristics, and interface bond strength testing methods. The outlook is from the development of nanosecond lasers with large pulse width/even energy/high power, the establishment of multivariable laser shock wave spatio-temporal pressure models, the construction of high strain rate mechanical models for composite materials, the invention of fast/accurate/intelligent detection methods and the establishment of a standardized and unified research system. A comprehensive analysis of domestic research deficiencies and technology gaps, suggested solutions and solutions, and hoped to promote the rapid development and engineering applications of laser shock wave interface bond strength testing technology by strengthening basic research and key technology breakthroughs.
Fibre-reinforced resin matrix composites are widely used in military/civilian aircraft due to their high specific strength/modulus and good fatigue/corrosion resistance. To avoid damage such as fibre breakage, matrix cracking and delamination caused by riveting/bolting, gluing is often used. Contamination of the adhesive interface, unevenness/ageing of the adhesive can lead to "kissing" and "weak bonding" problems, which cannot be detected and assessed by existing non-destructive testing techniques such as ultrasonic and infrared, and have become a safety hazard for composite structures. Laser bond inspection (LBI) is a new type of inspection technology that uses the mechanical effect of laser shock waves to reflect tensile waves for quantitative assessment of interface bond strength. It can effectively solve the problem of "kissing" and "weak bonding". This paper introduces the technical principles, characteristics and applications of laser shock wave interface bond strength testing; Summarises the progress of domestic and international research and the key issues to be solved from four aspects: Pulsed laser induced shock wave characteristics, shock wave propagation law and dynamic response of materials, laser shock layer cracking and damage characteristics, and interface bond strength testing methods. The outlook is from the development of nanosecond lasers with large pulse width/even energy/high power, the establishment of multivariable laser shock wave spatio-temporal pressure models, the construction of high strain rate mechanical models for composite materials, the invention of fast/accurate/intelligent detection methods and the establishment of a standardized and unified research system. A comprehensive analysis of domestic research deficiencies and technology gaps, suggested solutions and solutions, and hoped to promote the rapid development and engineering applications of laser shock wave interface bond strength testing technology by strengthening basic research and key technology breakthroughs.
2023, 40(6): 3255-3269.
doi: 10.13801/j.cnki.fhclxb.20221005.001
Abstract:
Mixed metal oxides (MMO) containing more than one type of metal, have shown great application potential to be adsorbents and catalysts due to their unique structural changes in water. Therefore, they have great potential in wastewater treatment. In this paper, the preparation methods of MMO are described, including solid-phase sintering, polymeric precursor calcination, layered double hydroxides precursor calcination, chemical coprecipitation and hydrothermal methods, and control methods of the element composition, element proportion, and structure of MMO to regulate their properties by changing these synthesis methods and conditions are introduced in detail. The main mechanisms of MMO in the removal of heavy metals, metalloids, organic pollutants and anionic are comprehensively analyzed which can be summarized as: in the process of structural reorganization of MMO, adsorption, catalysis and their synergy are accompanied. MMO can not only remove single pollutants efficiently, but also remove multiple pollutants simultaneously due to these three effects, so MMO have significant effects in effluent treatment, but at present most of the research is still at the experimental stage, and there are few studies on effluent treatment and engineering applications.
Mixed metal oxides (MMO) containing more than one type of metal, have shown great application potential to be adsorbents and catalysts due to their unique structural changes in water. Therefore, they have great potential in wastewater treatment. In this paper, the preparation methods of MMO are described, including solid-phase sintering, polymeric precursor calcination, layered double hydroxides precursor calcination, chemical coprecipitation and hydrothermal methods, and control methods of the element composition, element proportion, and structure of MMO to regulate their properties by changing these synthesis methods and conditions are introduced in detail. The main mechanisms of MMO in the removal of heavy metals, metalloids, organic pollutants and anionic are comprehensively analyzed which can be summarized as: in the process of structural reorganization of MMO, adsorption, catalysis and their synergy are accompanied. MMO can not only remove single pollutants efficiently, but also remove multiple pollutants simultaneously due to these three effects, so MMO have significant effects in effluent treatment, but at present most of the research is still at the experimental stage, and there are few studies on effluent treatment and engineering applications.
2023, 40(6): 3270-3278.
doi: 10.13801/j.cnki.fhclxb.20220907.003
Abstract:
Carbon fiber triaxial woven fabric/epoxy resin (TWF/EP) composite was prepared by vacuum assisted resin transfer molding (VARTM) method, in which carbon fiber TWF was reinforced material, and epoxy resin was matrix. Referring to the metallic materials-sheet and strip-test method for bending and folding properties, the bending experiment of TWF/EP was carried out to explore its bending performance, and the damage morphology and damage mechanism were analyzed. The results show that the folding strength and modulus of TWF/EP composites have a significant positive correlation with the fiber bundle specification and a negative correlation with the angle. In the range of 0°-30°, the folding properties of TWF/EP composites change slightly and show quasi-isotropy. The mechanical response of TWF/EP composites is brittle fracture, and the failure mode can be divided into complete fracture and incomplete fracture. The folding fracture mechanisms are mainly pure shear failure, compression-shear coupling failure and tenso-shear coupling failure.
Carbon fiber triaxial woven fabric/epoxy resin (TWF/EP) composite was prepared by vacuum assisted resin transfer molding (VARTM) method, in which carbon fiber TWF was reinforced material, and epoxy resin was matrix. Referring to the metallic materials-sheet and strip-test method for bending and folding properties, the bending experiment of TWF/EP was carried out to explore its bending performance, and the damage morphology and damage mechanism were analyzed. The results show that the folding strength and modulus of TWF/EP composites have a significant positive correlation with the fiber bundle specification and a negative correlation with the angle. In the range of 0°-30°, the folding properties of TWF/EP composites change slightly and show quasi-isotropy. The mechanical response of TWF/EP composites is brittle fracture, and the failure mode can be divided into complete fracture and incomplete fracture. The folding fracture mechanisms are mainly pure shear failure, compression-shear coupling failure and tenso-shear coupling failure.
2023, 40(6): 3279-3290.
doi: 10.13801/j.cnki.fhclxb.20220819.005
Abstract:
Carbon fiber reinforced vinylester resin composites (CFRP) are widely used as structural materials in ocean and ship engineering. In an unpredictable ocean environment and service condition, materials are subjected to hygroscopic environment and extreme temperatures. In this paper, the weight change and morphology changes of resin matrix and CFRP after immersion into water as well as the development of mechanical properties for CFRP during immersion duration at three temperatures (−30℃, room temperature and 70℃) were studied. The results from FTIR and liquid chromatography-mass spectrometry showed that the vinylester resin was hydrolyzed during immersion, and observations on the microscopic morphology revealed that the formation of fiber-matrix interface changed the moisture absorption behavior of resin matrix. The compressive strength of CFRP at cryogenic temperature and elevated temperature as well as at room temperature after 120 days’ immersion decreased by 27.4%, 36.2% and 32.8% as compared to the unaged strength at room temperature, respectively. And the in-plane shear strength increased by 35% at low temperature, decreased by 27% at elevated temperature, and increased by 7% after 120 days’ immersion, showing that the influence of temperature on the in-plane shear strength of CFRP was greater than that of hygroscopic aging. Meanwhile, the results from dynamic thermomechanical analysis displayed that the storage modulus and glass transition temperature (Tg) declined due to the moisture absorption, but later recovered partially.
Carbon fiber reinforced vinylester resin composites (CFRP) are widely used as structural materials in ocean and ship engineering. In an unpredictable ocean environment and service condition, materials are subjected to hygroscopic environment and extreme temperatures. In this paper, the weight change and morphology changes of resin matrix and CFRP after immersion into water as well as the development of mechanical properties for CFRP during immersion duration at three temperatures (−30℃, room temperature and 70℃) were studied. The results from FTIR and liquid chromatography-mass spectrometry showed that the vinylester resin was hydrolyzed during immersion, and observations on the microscopic morphology revealed that the formation of fiber-matrix interface changed the moisture absorption behavior of resin matrix. The compressive strength of CFRP at cryogenic temperature and elevated temperature as well as at room temperature after 120 days’ immersion decreased by 27.4%, 36.2% and 32.8% as compared to the unaged strength at room temperature, respectively. And the in-plane shear strength increased by 35% at low temperature, decreased by 27% at elevated temperature, and increased by 7% after 120 days’ immersion, showing that the influence of temperature on the in-plane shear strength of CFRP was greater than that of hygroscopic aging. Meanwhile, the results from dynamic thermomechanical analysis displayed that the storage modulus and glass transition temperature (Tg) declined due to the moisture absorption, but later recovered partially.
2023, 40(6): 3291-3301.
doi: 10.13801/j.cnki.fhclxb.20220811.005
Abstract:
3D woven reinforced composites have good structural integrity and mechanical properties. In order to explore the influence of warp insertion on mechanical properties of three-dimensional angle interlocking woven reinforced composites (3DAWCs), 3DAWCs with different proportions of warp insertion were designed and prepared in this paper. The bending properties of 3DAWCs with different proportions of warp insertion were studied in different temperature fields. The ratios of warp insertion to warp are 0∶1, 1∶1 and 2∶1. The testing temperatures include 20°C, 80°C and 150°C. The results show that the warp insertion have a significant effect on 3DAWC’s thickness, shape of yarn, shape of load-deflection curve, bending strength and damage distribution. The thickness and maximum bending load of 3DAWCs increase with the increase of the proportion of warp insertion, but the difference of bending strength between 1∶1 and 2∶1 is minor. The bending properties of the specimen decrease with the increase of temperature. In different temperature fields, the warp and weft bending properties of samples with different warp insertion ratios have different sensitivities to temperature.
3D woven reinforced composites have good structural integrity and mechanical properties. In order to explore the influence of warp insertion on mechanical properties of three-dimensional angle interlocking woven reinforced composites (3DAWCs), 3DAWCs with different proportions of warp insertion were designed and prepared in this paper. The bending properties of 3DAWCs with different proportions of warp insertion were studied in different temperature fields. The ratios of warp insertion to warp are 0∶1, 1∶1 and 2∶1. The testing temperatures include 20°C, 80°C and 150°C. The results show that the warp insertion have a significant effect on 3DAWC’s thickness, shape of yarn, shape of load-deflection curve, bending strength and damage distribution. The thickness and maximum bending load of 3DAWCs increase with the increase of the proportion of warp insertion, but the difference of bending strength between 1∶1 and 2∶1 is minor. The bending properties of the specimen decrease with the increase of temperature. In different temperature fields, the warp and weft bending properties of samples with different warp insertion ratios have different sensitivities to temperature.
2023, 40(6): 3302-3311.
doi: 10.13801/j.cnki.fhclxb.20220831.002
Abstract:
Composite structures have been widely used in the design of absorbing materials. However, the development of structural materials is challenged by the demand of broadband and efficient absorption performance. Herein, an impedance gradient microwave absorbing metastructure was designed and fabricated by fused deposition modeling of 3D printing technology. High dielectric loss composites were prepared by a mechanical blending of thermoplastic polyurethane and carbon black. Based on the reflectance formula of multilayer structure, the theoretical analysis model of impedance gradient structure was established. Calculation method of equivalent electromagnetic parameters, input impedance and reflectance of structure was derived. The designed impedance gradient structure can achieve −10 dB absorption bandwidth in the range of 2-18 GHz, and strong reflection loss of −20 dB can be achieved in the range of 2.68-18 GHz. The absorbing mechanism of the structure was further revealed by studying the distribution of electric field, magnetic field and power loss. The experimental results agree well with the simulation results. The impedance gradient structure designed in this paper provides a simple and promising route for broadband and wide-angle microwave strong absorption in practical application.
Composite structures have been widely used in the design of absorbing materials. However, the development of structural materials is challenged by the demand of broadband and efficient absorption performance. Herein, an impedance gradient microwave absorbing metastructure was designed and fabricated by fused deposition modeling of 3D printing technology. High dielectric loss composites were prepared by a mechanical blending of thermoplastic polyurethane and carbon black. Based on the reflectance formula of multilayer structure, the theoretical analysis model of impedance gradient structure was established. Calculation method of equivalent electromagnetic parameters, input impedance and reflectance of structure was derived. The designed impedance gradient structure can achieve −10 dB absorption bandwidth in the range of 2-18 GHz, and strong reflection loss of −20 dB can be achieved in the range of 2.68-18 GHz. The absorbing mechanism of the structure was further revealed by studying the distribution of electric field, magnetic field and power loss. The experimental results agree well with the simulation results. The impedance gradient structure designed in this paper provides a simple and promising route for broadband and wide-angle microwave strong absorption in practical application.
2023, 40(6): 3312-3321.
doi: 10.13801/j.cnki.fhclxb.20220824.002
Abstract:
The research on dielectric energy storage materials with high dielectric constant, breakdown strength and thermal conductivity has attracted much attention. In this paper, the hydroxylated boron nitride nanosheets (BN) prepared by high-temperature calcination and the barium titanate fibers loading alumina particles (Al2O3@BaTiO3) prepared by electrospinning were used to fill polyvinylidene fluoride (PVDF), and the composites were obtained by casting and hot-pressing. The synergistic effect of BN and Al2O3@BaTiO3 on the structure and properties of PVDF matrix composites was investigated. The results show that the Al2O3@BaTiO3 fibers can bridge the BN nanosheets, making the BN-Al2O3@BaTiO3/PVDF composites exhibit improved mechanical, dielectric properties and thermal conductivity in comparison with pure PVDF and BN/PVDF composites. With the increase of Al2O3@BaTiO3 fibers content, the dielectric constant and thermal conductivity of BN-Al2O3@BaTiO3/PVDF material increase, while the tensile strength and breakdown strength increase first and then decrease. When the content of Al2O3@BaTiO3 is 5wt%, the breakdown strength of BN-Al2O3@BaTiO3/PVDF composites reaches the highest value of 253.9 kV/mm, which is 2.43 times that of pure PVDF. Meanwhile, the tensile strength, dielectric constant and thermal conductivity are raised to 41.23 MPa, 12.1@1 kHz and 0.508 W/(m·K), also 10.8%, 44.0% and 185.4% higher than those of pure PVDF, respectively.
The research on dielectric energy storage materials with high dielectric constant, breakdown strength and thermal conductivity has attracted much attention. In this paper, the hydroxylated boron nitride nanosheets (BN) prepared by high-temperature calcination and the barium titanate fibers loading alumina particles (Al2O3@BaTiO3) prepared by electrospinning were used to fill polyvinylidene fluoride (PVDF), and the composites were obtained by casting and hot-pressing. The synergistic effect of BN and Al2O3@BaTiO3 on the structure and properties of PVDF matrix composites was investigated. The results show that the Al2O3@BaTiO3 fibers can bridge the BN nanosheets, making the BN-Al2O3@BaTiO3/PVDF composites exhibit improved mechanical, dielectric properties and thermal conductivity in comparison with pure PVDF and BN/PVDF composites. With the increase of Al2O3@BaTiO3 fibers content, the dielectric constant and thermal conductivity of BN-Al2O3@BaTiO3/PVDF material increase, while the tensile strength and breakdown strength increase first and then decrease. When the content of Al2O3@BaTiO3 is 5wt%, the breakdown strength of BN-Al2O3@BaTiO3/PVDF composites reaches the highest value of 253.9 kV/mm, which is 2.43 times that of pure PVDF. Meanwhile, the tensile strength, dielectric constant and thermal conductivity are raised to 41.23 MPa, 12.1@1 kHz and 0.508 W/(m·K), also 10.8%, 44.0% and 185.4% higher than those of pure PVDF, respectively.
2023, 40(6): 3322-3330.
doi: 10.13801/j.cnki.fhclxb.20220907.001
Abstract:
Carbon fiber reinforced polyether-ether-ketone composites (CF/PEEK) are increasingly used in aerospace and other fields. In this study, the influence of laminated structures on mechanical properties and thermo-formability of CF/PEEK sheets were investigated, and the associated mechanisms were discussed. Six different laminated structures of CF/PEEK sheets were designed, and the sheets were fabricated under the same process parameters. The mechanical properties and thermo-formability were characterized by tensile tests at 0° and 90° directions and Erichsen tests at 320℃, respectively. The results show that the tensile strength and thermo-formability of orthogonal structure [0/90/0/0/90/0] is the best. However, the thermo-formability of the structure added woven laminates or non-orthogonal structure are decreased. This is because the added woven laminate is observed to be a weak part in the structure, and the non-orthogonal structure has distinct mechanical properties in 0° and 90° directions and is prone to fiber-matrix failure.
Carbon fiber reinforced polyether-ether-ketone composites (CF/PEEK) are increasingly used in aerospace and other fields. In this study, the influence of laminated structures on mechanical properties and thermo-formability of CF/PEEK sheets were investigated, and the associated mechanisms were discussed. Six different laminated structures of CF/PEEK sheets were designed, and the sheets were fabricated under the same process parameters. The mechanical properties and thermo-formability were characterized by tensile tests at 0° and 90° directions and Erichsen tests at 320℃, respectively. The results show that the tensile strength and thermo-formability of orthogonal structure [0/90/0/0/90/0] is the best. However, the thermo-formability of the structure added woven laminates or non-orthogonal structure are decreased. This is because the added woven laminate is observed to be a weak part in the structure, and the non-orthogonal structure has distinct mechanical properties in 0° and 90° directions and is prone to fiber-matrix failure.
2023, 40(6): 3331-3340.
doi: 10.13801/j.cnki.fhclxb.20221012.001
Abstract:
In order to study the effect of antioxidant on the growth of water trees in crosslinked polyethylene (XLPE), antioxidant/metallocene polyethylene-crosslinked polyethylene (MPE-XLPE) blend insulation materials were obtained. A water blade electrode method was used to accelerate water tree aging, and it was found that both antioxidant 300 and 1035 can inhibit the growth of water trees in MPE-XLPE blends. The effect of antioxidant on the microstructure of MPE-XLPE blends was studied by thermal elongation, polarized optical microscopic observation, differential scanning calorimetric (DSC) curve and static contact angle, and the mechanism of improving the water tree resistance of the blends was discussed. The addition of antioxidant can reduce the crosslinking degree and spherulite size of MPE-XLPE blends, increase the crystallinity and slightly enhance the hydrophilic properties. It can reduce the area of amorphous region, and make the convergence of materials more compact, reducing the structural defects as well as the water penetration and water droplet formation. And the water in the materials can be evenly adsorbed on the polar groups of antioxidant in the form of molecules. So, the water was not easy to aggre-gate into water droplets, thereby improving the water tree resistance. In addition, through the measurement of mechanical and dielectric properties, it was found that the addition of antioxidant can reduce the mechanical pro-perties of MPE-XLPE blends, slightly increase the relative permittivity, and dielectric loss at higher frequencies, but they still met the requirements on the performance for water tree retardant XLPE cable insulation materials. The conductivity and dielectric strength of antioxidant/MPE-XLPE blends met the electrical performance requirements of XLPE insulation materials for wires and cables.
In order to study the effect of antioxidant on the growth of water trees in crosslinked polyethylene (XLPE), antioxidant/metallocene polyethylene-crosslinked polyethylene (MPE-XLPE) blend insulation materials were obtained. A water blade electrode method was used to accelerate water tree aging, and it was found that both antioxidant 300 and 1035 can inhibit the growth of water trees in MPE-XLPE blends. The effect of antioxidant on the microstructure of MPE-XLPE blends was studied by thermal elongation, polarized optical microscopic observation, differential scanning calorimetric (DSC) curve and static contact angle, and the mechanism of improving the water tree resistance of the blends was discussed. The addition of antioxidant can reduce the crosslinking degree and spherulite size of MPE-XLPE blends, increase the crystallinity and slightly enhance the hydrophilic properties. It can reduce the area of amorphous region, and make the convergence of materials more compact, reducing the structural defects as well as the water penetration and water droplet formation. And the water in the materials can be evenly adsorbed on the polar groups of antioxidant in the form of molecules. So, the water was not easy to aggre-gate into water droplets, thereby improving the water tree resistance. In addition, through the measurement of mechanical and dielectric properties, it was found that the addition of antioxidant can reduce the mechanical pro-perties of MPE-XLPE blends, slightly increase the relative permittivity, and dielectric loss at higher frequencies, but they still met the requirements on the performance for water tree retardant XLPE cable insulation materials. The conductivity and dielectric strength of antioxidant/MPE-XLPE blends met the electrical performance requirements of XLPE insulation materials for wires and cables.
2023, 40(6): 3341-3349.
doi: 10.13801/j.cnki.fhclxb.20220905.002
Abstract:
Epoxy resin (EP) is a typical insulating material for electronic packaging, but its thermal conductivity (less than 0.2 W/(m·K)) is low, and improving its thermal conductivity is an effective way to solve the heat dissipation problem of electronic devices. In this paper, 3D-AlN/EP composites were prepared by constructing a three-dimensional porous aluminum nitride skeleton (3D-AlN). The SEM morphology and XRD phase characterization results confirmed the successful preparation of 3D-AlN skeleton and 3D-AlN/EP composites. The mass fraction of the composite accounted for by the 3D-AlN skeleton was precisely measured using TGA, and by comparing with different contents of random distribution AlN/EP (Random AlN/EP) composites, it was found that the thermal conductivity of 3D-AlN/EP composites was higher than that of Random AlN/EP composites, the thermal conductivity of the 45.48wt%3D-AlN/EP composite at room temperature (25℃) was 1.00 W/(m·K), which was 5.6 times higher than that of pure EP (0.18 W/(m·K)). The interfacial thermal resistance of the composites was calculated using the theoretical model (Fogyel, Agari), and it was found that the 3D-AlN/EP composites had lower filler-to-filler interfacial thermal resistance compared to Random AlN/EP, with 2.704×105 K·W−1 and 4.019×105 K·W−1, respectively. The electrical properties showed that the 45.48wt%3D-AlN/EP composite had good dielectric and insulating properties (volume resistivity is 4.16×1011 Ω·cm). This study provides an effective solution to the heat dissipation problem of electronic devices from the perspective of package insulation material modification.
Epoxy resin (EP) is a typical insulating material for electronic packaging, but its thermal conductivity (less than 0.2 W/(m·K)) is low, and improving its thermal conductivity is an effective way to solve the heat dissipation problem of electronic devices. In this paper, 3D-AlN/EP composites were prepared by constructing a three-dimensional porous aluminum nitride skeleton (3D-AlN). The SEM morphology and XRD phase characterization results confirmed the successful preparation of 3D-AlN skeleton and 3D-AlN/EP composites. The mass fraction of the composite accounted for by the 3D-AlN skeleton was precisely measured using TGA, and by comparing with different contents of random distribution AlN/EP (Random AlN/EP) composites, it was found that the thermal conductivity of 3D-AlN/EP composites was higher than that of Random AlN/EP composites, the thermal conductivity of the 45.48wt%3D-AlN/EP composite at room temperature (25℃) was 1.00 W/(m·K), which was 5.6 times higher than that of pure EP (0.18 W/(m·K)). The interfacial thermal resistance of the composites was calculated using the theoretical model (Fogyel, Agari), and it was found that the 3D-AlN/EP composites had lower filler-to-filler interfacial thermal resistance compared to Random AlN/EP, with 2.704×105 K·W−1 and 4.019×105 K·W−1, respectively. The electrical properties showed that the 45.48wt%3D-AlN/EP composite had good dielectric and insulating properties (volume resistivity is 4.16×1011 Ω·cm). This study provides an effective solution to the heat dissipation problem of electronic devices from the perspective of package insulation material modification.
2023, 40(6): 3350-3365.
doi: 10.13801/j.cnki.fhclxb.20220905.001
Abstract:
In order to solve the indefects that magnetic nano-Fe3O4 particles were corroded and agglomerated easily, functional modification was carried out. FeCl3 and FeSO4 were used as raw materials and ammonia as preci-pitant in the presence of ultrasonic irradiation, then functionalized by ethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APTMS) to prepare SiO2-coated amino-functional nanocomposites Fe3O4@SiO2-APTMS. The magnetic nanocomposites were characterized by TEM, FTIR, VSM, TGA, low temperature nitrogen adsorption and XRD, etc. The characterized results show that the magnetic nanocomposites prepared by ultrasonic strengthening method have the characteristics of strong magnetic response, strong acid and alkali resistance, high dispersion, large specific surface area and small particle size.Meanwhile, the adsorption effects of magnetic nanocomposites for Pb(Ⅱ) were investigated. The results show that the initial pH value of the solution and the dosage of adsorbent have greatest effects on the adsorption effect of Pb(Ⅱ) with the initial pH value of the solution 5.86 and the dosage of adsorbent 1.0-1.5 g·L−1. The Langmuir model is suitable for simulating the isothermal adsorption process, and the adsorption process is a spontaneous process when Gibbs free energy change ∆G0<0. The adsorption behavior of Pb(Ⅱ) can be well described by quasi-second-order kinetics on the composites, Quasi-second-order kinetic constant k2=0.0401 g·mg−1·min−1, equilibrium adsorption capacity qe=80.041 mg·g−1; it is speculated that the adsorption mechanism is mainly complex adsorption and ion exchange.
In order to solve the indefects that magnetic nano-Fe3O4 particles were corroded and agglomerated easily, functional modification was carried out. FeCl3 and FeSO4 were used as raw materials and ammonia as preci-pitant in the presence of ultrasonic irradiation, then functionalized by ethyl orthosilicate (TEOS) and 3-aminopropyltrimethoxysilane (APTMS) to prepare SiO2-coated amino-functional nanocomposites Fe3O4@SiO2-APTMS. The magnetic nanocomposites were characterized by TEM, FTIR, VSM, TGA, low temperature nitrogen adsorption and XRD, etc. The characterized results show that the magnetic nanocomposites prepared by ultrasonic strengthening method have the characteristics of strong magnetic response, strong acid and alkali resistance, high dispersion, large specific surface area and small particle size.Meanwhile, the adsorption effects of magnetic nanocomposites for Pb(Ⅱ) were investigated. The results show that the initial pH value of the solution and the dosage of adsorbent have greatest effects on the adsorption effect of Pb(Ⅱ) with the initial pH value of the solution 5.86 and the dosage of adsorbent 1.0-1.5 g·L−1. The Langmuir model is suitable for simulating the isothermal adsorption process, and the adsorption process is a spontaneous process when Gibbs free energy change ∆G0<0. The adsorption behavior of Pb(Ⅱ) can be well described by quasi-second-order kinetics on the composites, Quasi-second-order kinetic constant k2=0.0401 g·mg−1·min−1, equilibrium adsorption capacity qe=80.041 mg·g−1; it is speculated that the adsorption mechanism is mainly complex adsorption and ion exchange.
2023, 40(6): 3366-3374.
doi: 10.13801/j.cnki.fhclxb.20220909.003
Abstract:
To get lightweight, highly hygroscopic materials, Schiff base composite coating was prepared to hydrophilically modify the matrix material to improve the hygroscopic performance. Glutaraldehyde (GA) as an intermediate was used to covalently link aminated nano-silica (SiO2) and the hydrophilic substance 2-[(2-aminoethyl)amino] ethanesulfonate sodium (AAS) to prepare Schiff base composite material (SiO2-NH2-GA-AAS), and then the SiO2-NH2-GA-AAS / CS composite coating was prepared by dispersing it in chitosan (CS) solution. The polymer polyethylene terephthalate alcohol (PET) was used as the base material, and the composite coating was coated on its surface by dipping to modify it. FTIR, field emission scanning electron microscope equipped with energy dispersive spectrometer (FESEM-EDS) and contact angle measuring instrument were used to test the microscopic morphology, element distribution and surface wettability of the PET substrate coated with composite coating. The adsorption process was fitted with Pseudo-first-order and Pseudo-second-order kinetic models. The results show the modified PET substrate has the best hygroscopic performance when mass ratio of SiO2-NH2/AAS is 1∶2 and the amount of SiO2-NH2-GA-AAS is 10wt%. From the FESEM-EDS analysis, it can be seen that the surface of the modified PET substrate is coated with a uniform composite material, and the contact angle changes from the original 135° to 0°, achieving the super-hydrophilic effect. In the environment of 25℃, 97% relative humidity (RH), the PET substrate coated with the optimum composite coating reaches moisture saturation after 45 h of moisture absorption which reaches 36.94% moisture content. The moisture absorption performance has been extremely improved. The whole adsorption process conforms to the Pseudo-second-order kinetic model.
To get lightweight, highly hygroscopic materials, Schiff base composite coating was prepared to hydrophilically modify the matrix material to improve the hygroscopic performance. Glutaraldehyde (GA) as an intermediate was used to covalently link aminated nano-silica (SiO2) and the hydrophilic substance 2-[(2-aminoethyl)amino] ethanesulfonate sodium (AAS) to prepare Schiff base composite material (SiO2-NH2-GA-AAS), and then the SiO2-NH2-GA-AAS / CS composite coating was prepared by dispersing it in chitosan (CS) solution. The polymer polyethylene terephthalate alcohol (PET) was used as the base material, and the composite coating was coated on its surface by dipping to modify it. FTIR, field emission scanning electron microscope equipped with energy dispersive spectrometer (FESEM-EDS) and contact angle measuring instrument were used to test the microscopic morphology, element distribution and surface wettability of the PET substrate coated with composite coating. The adsorption process was fitted with Pseudo-first-order and Pseudo-second-order kinetic models. The results show the modified PET substrate has the best hygroscopic performance when mass ratio of SiO2-NH2/AAS is 1∶2 and the amount of SiO2-NH2-GA-AAS is 10wt%. From the FESEM-EDS analysis, it can be seen that the surface of the modified PET substrate is coated with a uniform composite material, and the contact angle changes from the original 135° to 0°, achieving the super-hydrophilic effect. In the environment of 25℃, 97% relative humidity (RH), the PET substrate coated with the optimum composite coating reaches moisture saturation after 45 h of moisture absorption which reaches 36.94% moisture content. The moisture absorption performance has been extremely improved. The whole adsorption process conforms to the Pseudo-second-order kinetic model.
2023, 40(6): 3375-3384.
doi: 10.13801/j.cnki.fhclxb.20220809.007
Abstract:
High-performance coating polyether-ether-ketone (PEEK) has been widely used in fields such as aerospace, mechanical and chemical industry, but industrial development has put forward higher requirements for PEEK's self-lubricating performance. In this work, an emerging two-dimensional black phosphorus (BP) modified PEEK self-lubricating composite coating was prepared by slurry printing techniques, and the microstructure, microhardness and tribological properties of coatings with different BP content were investigated. The results show that the introduction of BP results in the roughening of the coating surface and the reduction of the compactness. The microhardness was first improved, reaching a maximum value of 27.2 HV at 1wt% BP, but subsequently decreased. BP exhibited excellent anti-friction ability, which reduced the friction coefficient of the coating from 0.21 to the lowest value of 0.06. The wear rate was strongly dependent on the microhardness and reached the lowest value of 5.35×10−6 mm3·N−1·m−1 at 1wt% BP, which was 17.1% lower than that of pure PEEK. Pure PEEK suffered primarily from abrasive wear. BP weakened the grooves on the worn surface and transformed the friction mechanism into fatigue wear. The lubricating effect was attributed to the synergistic promotion of the tribo-transfer film formation by phosphorus oxides and BP.
High-performance coating polyether-ether-ketone (PEEK) has been widely used in fields such as aerospace, mechanical and chemical industry, but industrial development has put forward higher requirements for PEEK's self-lubricating performance. In this work, an emerging two-dimensional black phosphorus (BP) modified PEEK self-lubricating composite coating was prepared by slurry printing techniques, and the microstructure, microhardness and tribological properties of coatings with different BP content were investigated. The results show that the introduction of BP results in the roughening of the coating surface and the reduction of the compactness. The microhardness was first improved, reaching a maximum value of 27.2 HV at 1wt% BP, but subsequently decreased. BP exhibited excellent anti-friction ability, which reduced the friction coefficient of the coating from 0.21 to the lowest value of 0.06. The wear rate was strongly dependent on the microhardness and reached the lowest value of 5.35×10−6 mm3·N−1·m−1 at 1wt% BP, which was 17.1% lower than that of pure PEEK. Pure PEEK suffered primarily from abrasive wear. BP weakened the grooves on the worn surface and transformed the friction mechanism into fatigue wear. The lubricating effect was attributed to the synergistic promotion of the tribo-transfer film formation by phosphorus oxides and BP.
2023, 40(6): 3385-3395.
doi: 10.13801/j.cnki.fhclxb.20220809.006
Abstract:
Nano bimetallic oxides have broad application prospects as fluoride removal agents. La2O3-CeO2 nanofibers were fabricated via electrospinning-calcination method using Ce(NO3)3·6H2O and La(NO3)3·6H2O as raw materials and polyacrylonitrile (PAN) as template. TEM, SEM-EDS, BET, FTIR and XRD were employed to verify the morphology and structure of La2O3-CeO2 nanofibers. The defluoridation properties of La2O3-CeO2 nanofibers were discussed under batch mode, and the effects of adsorbate (F−) initial concentration, pH, contact time, La2O3-CeO2 nanofibers dose and coexisting anions on the defluoridation were explored. The results illustrate that the specific surface area of La2O3-CeO2 adsorbent is 31.04 m2·g−1. The La2O3-CeO2 nanofibers exhibit the best defluoridation performance at pH of 3, and the adsorption capacity of La2O3-CeO2 nanofibers climbs up with rise of the initial concentration of F−. The pseudo-second-order kinetic and Langmuir isotherm model (R2>0.99) simulate the defluoridation process of La2O3-CeO2 nanofibers better, and the maximum uptake of F− by La2O3-CeO2 nanofibers is 111.98 mg·g−1 at 45℃. Thermodynamic studies suggest that the defluoridation process of La2O3-CeO2 nanofibers is a spontaneous (ΔG0<0), entropy increase (ΔS0=56.63 J·mol−1·K−1) and endothermic (ΔH0=9.90 kJ·mol−1) process.
Nano bimetallic oxides have broad application prospects as fluoride removal agents. La2O3-CeO2 nanofibers were fabricated via electrospinning-calcination method using Ce(NO3)3·6H2O and La(NO3)3·6H2O as raw materials and polyacrylonitrile (PAN) as template. TEM, SEM-EDS, BET, FTIR and XRD were employed to verify the morphology and structure of La2O3-CeO2 nanofibers. The defluoridation properties of La2O3-CeO2 nanofibers were discussed under batch mode, and the effects of adsorbate (F−) initial concentration, pH, contact time, La2O3-CeO2 nanofibers dose and coexisting anions on the defluoridation were explored. The results illustrate that the specific surface area of La2O3-CeO2 adsorbent is 31.04 m2·g−1. The La2O3-CeO2 nanofibers exhibit the best defluoridation performance at pH of 3, and the adsorption capacity of La2O3-CeO2 nanofibers climbs up with rise of the initial concentration of F−. The pseudo-second-order kinetic and Langmuir isotherm model (R2>0.99) simulate the defluoridation process of La2O3-CeO2 nanofibers better, and the maximum uptake of F− by La2O3-CeO2 nanofibers is 111.98 mg·g−1 at 45℃. Thermodynamic studies suggest that the defluoridation process of La2O3-CeO2 nanofibers is a spontaneous (ΔG0<0), entropy increase (ΔS0=56.63 J·mol−1·K−1) and endothermic (ΔH0=9.90 kJ·mol−1) process.
2023, 40(6): 3396-3404.
doi: 10.13801/j.cnki.fhclxb.20220811.003
Abstract:
During the forming process of composite components with complex-shaped geometries, the fiber preform would deform significantly in macro-scale. The bending performance of the preform has a decisive impact on the formation and evolution of wrinkle defects. The three-point bending method was employed to test the carbon fiber 3D woven preforms. Micro-scale deformation mechanisms of the preform were researched using the Micro-CT technology. Effects of structural parameters such as warp density and weft density on the bending property of the preforms were analyzed. It is shown that the critical bending energy of the preforms increases linearly with the increase of weaving point density. The macro-scale bending deformation of the preform is mainly composed of micro-scale deformations such as changing of warp yarn buckling degree, local compression buckling of warp yarns and slippage between warp and weft yarn layers.
During the forming process of composite components with complex-shaped geometries, the fiber preform would deform significantly in macro-scale. The bending performance of the preform has a decisive impact on the formation and evolution of wrinkle defects. The three-point bending method was employed to test the carbon fiber 3D woven preforms. Micro-scale deformation mechanisms of the preform were researched using the Micro-CT technology. Effects of structural parameters such as warp density and weft density on the bending property of the preforms were analyzed. It is shown that the critical bending energy of the preforms increases linearly with the increase of weaving point density. The macro-scale bending deformation of the preform is mainly composed of micro-scale deformations such as changing of warp yarn buckling degree, local compression buckling of warp yarns and slippage between warp and weft yarn layers.
2023, 40(6): 3405-3416.
doi: 10.13801/j.cnki.fhclxb.20220822.003
Abstract:
In this paper, based on the two-layer design, a photothermal self-healing superhydrophobic coating graphene oxide-shape memory epoxy resin (GO-SMEP)/perfluorodecyltrimethoxysilane-polydimethylsiloxane (PFDT-PDMS)@SiO2 (GO-SMEP/PPS) that could quickly repair physical damages was prepared. Aiming to solve the practical problems of the physical damage repair time is long, the repair rate is low, and stainless steel is susceptible to corrosion under extreme conditions for a long time. The double-layer coating was designed by combination of self-healing coating with photothermal effect GO-SMEP and the superhydrophobic coating with multi-level rough micro-nano structure PPS. Furthermore, the preparation optimization of the coating and its wettability, photothermal effect, corrosion resistance, self-healing and other properties were studied.The results show that when mass ratio of PDMS∶μ-SiO2∶n-SiO2=1.5∶1∶1 and the PFDT content is 30wt%, the superhydrophobicity of the GO-SMEP/PPS coating on the 304 stainless steel substrate is the best, and exhibits apparent specularity and high repulsion to droplets. The photothermal effect of the GO-SMEP/PPS coating is enhanced with the increase of the photothermal conversion agent GO content, and the GO-SMEP/PPS coating with a GO content of 0.5wt% is subjected to 3 cycles of near-infrared light cycling radiation, its photothermal effect remains highly stable.The damaged GO-SMEP/PPS coating was placed under 808 nm near-infrared light, and the physical scratches were repaired from 40 μm to about 1 μm after a short period of irradiation for 3 min. Based on the low-frequency impedance modulus of the coating before and after repair (|Z|0.01 Hz) further calculates the restoration rate as high as 97.5%. The AC impedance spectroscopy (EIS) analysis shows that the corrosion resistance of the GO-SMEP/PPS (0.5wt% GO) coating is jointly determined by the GO-SMEP bottom layer and the PPS surface layer, with the largest capacitive arc radius and the low-frequency impedance modulus |Z|0.01 Hz is as high as 3.2×105 Ω·cm2, which has the strongest barrier to corrosive media and shows good corrosion resistance. After applying the coating on 304 stainless steel substrate, the measured pitting corrosion potential (Eb=0.263 V) and passive current density (Ip=4.80×10−8 A/cm2) shows good corrosion resistance to stainless steel.
Vanadium dioxide-polydiacetylene thermochromic composite films and their solar regulation properties
2023, 40(6): 3417-3427.
doi: 10.13801/j.cnki.fhclxb.20221028.002
Abstract:
Vanadium dioxide (VO2) with thermally induced phase transition has demonstrated a good regulation ability in the range of near-infrared light, and widely used in smart windows. However, the VO2-based smart windows still face critical challenges in practical use, such as the unfavorable brown-yellow color of the VO2 thin film, and lack of indicative color-changing for the phase transition process, which are key factors limiting its applications in smart glass. Combining VO2 with other chromogenic materials could effectively improve the appearance color of smart window coatings and endow it indicative color-changing function. In this study, it is successful to obtain VO2 multifunctional composite film with reversible thermochromic polydiacetylene (PDA-1, from blue to red) through a bilayer structure strategy. The composite film not only shows favorable grayish-blue color, but also exhibits good solar light regulation ability and luminescence transmittance (solar light regulation ability ΔTsol=7.64%, luminescence transmittance at low temperature Tl, lum=56.23%, luminescence transmittance at high temperature Th, lum=62.37%). In addition, the thermochromic temperature of the PDA-1 is close to the phase transition temperature of monoclinic VO2 (~68℃). With the temperature increases, the appearance color of the composite film can change from grayish-blue to red color, and also regulating the near-infrared transmittance, which is conducive to the visual display and further promotion for the thermochromic smart windows.
Vanadium dioxide (VO2) with thermally induced phase transition has demonstrated a good regulation ability in the range of near-infrared light, and widely used in smart windows. However, the VO2-based smart windows still face critical challenges in practical use, such as the unfavorable brown-yellow color of the VO2 thin film, and lack of indicative color-changing for the phase transition process, which are key factors limiting its applications in smart glass. Combining VO2 with other chromogenic materials could effectively improve the appearance color of smart window coatings and endow it indicative color-changing function. In this study, it is successful to obtain VO2 multifunctional composite film with reversible thermochromic polydiacetylene (PDA-1, from blue to red) through a bilayer structure strategy. The composite film not only shows favorable grayish-blue color, but also exhibits good solar light regulation ability and luminescence transmittance (solar light regulation ability ΔTsol=7.64%, luminescence transmittance at low temperature Tl, lum=56.23%, luminescence transmittance at high temperature Th, lum=62.37%). In addition, the thermochromic temperature of the PDA-1 is close to the phase transition temperature of monoclinic VO2 (~68℃). With the temperature increases, the appearance color of the composite film can change from grayish-blue to red color, and also regulating the near-infrared transmittance, which is conducive to the visual display and further promotion for the thermochromic smart windows.
2023, 40(6): 3428-3440.
doi: 10.13801/j.cnki.fhclxb.20220906.003
Abstract:
Effective monitoring of toxic and harmful gases and rapid degradation of organic pollutants are essential to reduce the hazards of air and water pollution. In this study, the MoS2 nanosheets prepared by hydrothermal method were coupled into the ZnO nanoparticles prepared by sol-gel method to form ZnO-MoS2 nano-composites via a facile ultrasonic chemical route. The structure, morphology and surface chemical component of synthesized materials were characterized by XRD, SEM, TEM and XPS. The characterizations show that multilayer MoS2 nanosheets are well dispersed among ZnO nanoparticles, and ZnO-MoS2 composites have good crystallinity and abundant surface defects. The photoelectric properties were explored by UV-vis diffuse reflectance spectrum, photoluminescence spectra (PL) and surface photovoltage spectra (SPV). The results reveal that the formation of ZnO-MoS2 heterostructure improves the utilization of light and promotes the effective separation of photo-carriers. The UV light-activated gas sensitivity test using NO2 as the target gas preformed at room temperature saw that the prepared ZnO-MoS2 gas sensor exhibited excellent gas sensing properties with good sensitivity, recoverability, stability and selectivity, which could effectively respond to low concentration NO2. The response of the optimized ZnO-MoS2 sensor with 5wt%MoS2 to 0.47 mg/m3 NO2 reached 19.6%. Meanwhile, the gas sensing performance was found to be greatly influenced by the adsorption of O2 molecule on the surface of the materials, and ZnO-MoS2 gas sensor possessed much higher gas sensitivity to NO2 under oxygen free conditions. In addition, the photocatalytic degradation of methylene blue (MB) under simulated sunlight reveal that the ZnO-MoS2 composites can rapidly remove the high concentration of MB (15 mg/L) in aqueous solution within 40 min by combined action of adsorption and photocatalysis, thereinto, the ZnO-MoS2 sample with 10wt%MoS2 shows a reaction rate constant as high as 0.032 min−1. Mechanism analysis shows that the improvement of gas sensing and photocatalytic performance of ZnO-MoS2 composites mainly attribute to the better absorbability of MoS2 and the promotion of photocarrier separation rate caused by combination.
Effective monitoring of toxic and harmful gases and rapid degradation of organic pollutants are essential to reduce the hazards of air and water pollution. In this study, the MoS2 nanosheets prepared by hydrothermal method were coupled into the ZnO nanoparticles prepared by sol-gel method to form ZnO-MoS2 nano-composites via a facile ultrasonic chemical route. The structure, morphology and surface chemical component of synthesized materials were characterized by XRD, SEM, TEM and XPS. The characterizations show that multilayer MoS2 nanosheets are well dispersed among ZnO nanoparticles, and ZnO-MoS2 composites have good crystallinity and abundant surface defects. The photoelectric properties were explored by UV-vis diffuse reflectance spectrum, photoluminescence spectra (PL) and surface photovoltage spectra (SPV). The results reveal that the formation of ZnO-MoS2 heterostructure improves the utilization of light and promotes the effective separation of photo-carriers. The UV light-activated gas sensitivity test using NO2 as the target gas preformed at room temperature saw that the prepared ZnO-MoS2 gas sensor exhibited excellent gas sensing properties with good sensitivity, recoverability, stability and selectivity, which could effectively respond to low concentration NO2. The response of the optimized ZnO-MoS2 sensor with 5wt%MoS2 to 0.47 mg/m3 NO2 reached 19.6%. Meanwhile, the gas sensing performance was found to be greatly influenced by the adsorption of O2 molecule on the surface of the materials, and ZnO-MoS2 gas sensor possessed much higher gas sensitivity to NO2 under oxygen free conditions. In addition, the photocatalytic degradation of methylene blue (MB) under simulated sunlight reveal that the ZnO-MoS2 composites can rapidly remove the high concentration of MB (15 mg/L) in aqueous solution within 40 min by combined action of adsorption and photocatalysis, thereinto, the ZnO-MoS2 sample with 10wt%MoS2 shows a reaction rate constant as high as 0.032 min−1. Mechanism analysis shows that the improvement of gas sensing and photocatalytic performance of ZnO-MoS2 composites mainly attribute to the better absorbability of MoS2 and the promotion of photocarrier separation rate caused by combination.
2023, 40(6): 3441-3448.
doi: 10.13801/j.cnki.fhclxb.20220825.001
Abstract:
Poly(N-isopropylacrylamide) (PNIPAM), which contains both hydrophilic amide and hydrophobic isopropyl groups, is one of the most widely used temperature-sensitive polymers, and its related products have promising applications in the fields of tissue engineering, medical care and smart fabrics. In this study, PNIPAM was successfully synthesized by free radical polymerization, and PNIPAM was prepared into temperature-sensitive nano-membranes by electrospinning technology innovatively. Then, we tried to copolymerize polyethylene glycol methyl ether (mPEG) and PNIPAM in different proportions to investigate the performance of PNIPAM-co-mPEG. The results showed that the temperature-sensitive nano-membranes exhibited significant hydrophilic and hydrophobic transitions with temperature changes. Compared with the pure PNIPAM temperature-sensitive nano-membranes, the mechanical properties of the PNIPAM-co-mPEG were significantly improved, and it could maintain the inherent fiber morphology under the condition of large water absorption and swelling. The residual weight rate and the initial decomposition temperature of PNIPAM-co-mPEG are increased by 321% and 240%, respectively. The water contact angle of PNIPAM-co-mPEG at room temperature decreases by more than 16°, which improves the hydrophilicity to a certain extent. Moreover, the low critical solution temperature of PNIPAM-co-mPEG is increased from 31.7℃ to 43.6℃, the temperature-sensitive range is expanded.
Poly(N-isopropylacrylamide) (PNIPAM), which contains both hydrophilic amide and hydrophobic isopropyl groups, is one of the most widely used temperature-sensitive polymers, and its related products have promising applications in the fields of tissue engineering, medical care and smart fabrics. In this study, PNIPAM was successfully synthesized by free radical polymerization, and PNIPAM was prepared into temperature-sensitive nano-membranes by electrospinning technology innovatively. Then, we tried to copolymerize polyethylene glycol methyl ether (mPEG) and PNIPAM in different proportions to investigate the performance of PNIPAM-co-mPEG. The results showed that the temperature-sensitive nano-membranes exhibited significant hydrophilic and hydrophobic transitions with temperature changes. Compared with the pure PNIPAM temperature-sensitive nano-membranes, the mechanical properties of the PNIPAM-co-mPEG were significantly improved, and it could maintain the inherent fiber morphology under the condition of large water absorption and swelling. The residual weight rate and the initial decomposition temperature of PNIPAM-co-mPEG are increased by 321% and 240%, respectively. The water contact angle of PNIPAM-co-mPEG at room temperature decreases by more than 16°, which improves the hydrophilicity to a certain extent. Moreover, the low critical solution temperature of PNIPAM-co-mPEG is increased from 31.7℃ to 43.6℃, the temperature-sensitive range is expanded.
2023, 40(6): 3449-3458.
doi: 10.13801/j.cnki.fhclxb.20220728.001
Abstract:
In order to optimize the properties of ceramic shell for superalloy investment casting, the 0.75wt% hybrid fibers were uniformly mixed in to the corundum sands via solvent method. Then, the short nylon fiber (Nsf) and short alumina fiber (Asf) modified silica sol shell were prepared with different fiber mass ratios. The microstructure of ceramic fracture was observed based on SEM, and the distribution patterns and crack growth characteristics of fibers were analyzed, which revealed the sintering behavior of fibers and matrix and further indicated the reinforcement mechanism. The results present that the properties of ceramic shell are significantly improved by a higher volume proportion of fibers in shell due to the stuccoing layer fiber addition. The flexible Nsf is wound on the surface of corundum sands, which dissipates the load energy by friction during the fiber pull-out process. Meanwhile, the Nsf is burned out and then form the in-situ holes in the matrix, which is beneficial to enhancing the permeability of shell. And the Nsf∶Asf=4∶1 sample shows the highest green strength, permeability and open porosity at 5.08 MPa, 4.4, 20.82%, systematically. In addition, the microcracks are easy to formed in the sintered ceramic shell because of the dehydration and drying However, the crack will be bifurcated, proliferated and deflected when it extends to the surface of Asf. The phenomena indicates that the interlock Asf network can effectively decrease the formation of continuous cracks, and further inhibits the ceramic particles striping and the intergranular fracture tendency for shell. Therefore, the Asf can effectively compensate the strength weaken caused by burned out Nsf. At last, the highest sintering strength of 10.51 MPa is obtained in the Nsf∶Asf=4∶1 sample, simultaneously, the high temperature self-loaded deformation rate of ceramic shell is only 0.82%.
In order to optimize the properties of ceramic shell for superalloy investment casting, the 0.75wt% hybrid fibers were uniformly mixed in to the corundum sands via solvent method. Then, the short nylon fiber (Nsf) and short alumina fiber (Asf) modified silica sol shell were prepared with different fiber mass ratios. The microstructure of ceramic fracture was observed based on SEM, and the distribution patterns and crack growth characteristics of fibers were analyzed, which revealed the sintering behavior of fibers and matrix and further indicated the reinforcement mechanism. The results present that the properties of ceramic shell are significantly improved by a higher volume proportion of fibers in shell due to the stuccoing layer fiber addition. The flexible Nsf is wound on the surface of corundum sands, which dissipates the load energy by friction during the fiber pull-out process. Meanwhile, the Nsf is burned out and then form the in-situ holes in the matrix, which is beneficial to enhancing the permeability of shell. And the Nsf∶Asf=4∶1 sample shows the highest green strength, permeability and open porosity at 5.08 MPa, 4.4, 20.82%, systematically. In addition, the microcracks are easy to formed in the sintered ceramic shell because of the dehydration and drying However, the crack will be bifurcated, proliferated and deflected when it extends to the surface of Asf. The phenomena indicates that the interlock Asf network can effectively decrease the formation of continuous cracks, and further inhibits the ceramic particles striping and the intergranular fracture tendency for shell. Therefore, the Asf can effectively compensate the strength weaken caused by burned out Nsf. At last, the highest sintering strength of 10.51 MPa is obtained in the Nsf∶Asf=4∶1 sample, simultaneously, the high temperature self-loaded deformation rate of ceramic shell is only 0.82%.
2023, 40(6): 3459-3472.
doi: 10.13801/j.cnki.fhclxb.20220929.001
Abstract:
In order to study the triaxial compressive mechanical properties of glass fiber coral seawater concrete, 36 glass fiber coral seawater concrete cylindrical specimens were subjected to conventional triaxial loading tests. The damage morphology of the specimens was observed, and the stress-strain curves were obtained. Based on the test data, the influence of the surrounding pressure value and glass fiber admixture on the mechanical properties was analyzed. The results show that the damage pattern changes from vertical splitting to oblique shear and central extrusion flow damage as the surrounding pressure increases. The slope of the rising section of the stress-strain curve increases, the peak section increases, and the falling section after the peak point gradually disappears, and the corresponding initial elastic modulus, peak strain, peak stress and energy dissipation increase, while the ductility coefficient shows a trend of first increasing and then decreasing, when the confining pressure value is 6 MPa, the ductility coefficients are 3.64 times, 3.32 times and 2.86 times respectively in the uniaxial pressure state. The average values of modulus of elasticity, ductility coefficient, peak stress and energy dissipation all show a trend of increasing and then decreasing, while the average peak strain shows a trend of decreasing and then increasing, when the glass fiber dosage is 4 kg·m−3, the average modulus of elasticity reaches 5.83 GPa, which increases the average ductility coefficient by 3.0% and 16.7% and the average peak stress by 9.6% compared with the other two dosages. The lateral surrounding pressure and external glass fiber doping can reduce the development speed and degree of damage, and the lateral surrounding pressure can also delay the appearance of initial damage.
In order to study the triaxial compressive mechanical properties of glass fiber coral seawater concrete, 36 glass fiber coral seawater concrete cylindrical specimens were subjected to conventional triaxial loading tests. The damage morphology of the specimens was observed, and the stress-strain curves were obtained. Based on the test data, the influence of the surrounding pressure value and glass fiber admixture on the mechanical properties was analyzed. The results show that the damage pattern changes from vertical splitting to oblique shear and central extrusion flow damage as the surrounding pressure increases. The slope of the rising section of the stress-strain curve increases, the peak section increases, and the falling section after the peak point gradually disappears, and the corresponding initial elastic modulus, peak strain, peak stress and energy dissipation increase, while the ductility coefficient shows a trend of first increasing and then decreasing, when the confining pressure value is 6 MPa, the ductility coefficients are 3.64 times, 3.32 times and 2.86 times respectively in the uniaxial pressure state. The average values of modulus of elasticity, ductility coefficient, peak stress and energy dissipation all show a trend of increasing and then decreasing, while the average peak strain shows a trend of decreasing and then increasing, when the glass fiber dosage is 4 kg·m−3, the average modulus of elasticity reaches 5.83 GPa, which increases the average ductility coefficient by 3.0% and 16.7% and the average peak stress by 9.6% compared with the other two dosages. The lateral surrounding pressure and external glass fiber doping can reduce the development speed and degree of damage, and the lateral surrounding pressure can also delay the appearance of initial damage.
2023, 40(6): 3473-3485.
doi: 10.13801/j.cnki.fhclxb.20220819.002
Abstract:
In order to analyze the influence of basalt fiber reinforced polymer (BFRP) mesh on the bonding performance of ultra-high performance concrete (UHPC), the BFRP-UHPC interface pull-out bonding test (48 pieces) and shear test (21 pieces) were carried out respectively with three parameters of dry/wet bonding type, BFRP mesh anchorage depth and mesh thickness. The effects of BFRP mesh on the failure mode, bonding performance, shear stress slip curve, tensile ratio and toughness were studied. At the same time, the failure mechanism of BFRP-UHPC interface was revealed by SEM. The results show that the anchoring depth directly determines the failure mode of BFRP-UHPC interface. There is a positive correlation between tangential bonding stress and normal bonding stress. The wet bonding strength of BFRP-UHPC interface is higher than that of dry bonding process. With the increase of BFRP thickness and anchorage depth, the interfacial bonding stress between BFRP and UHPC shows a decreasing trend. Steel fiber has remarkable toughening effect on BFRP-UHPC interface, its end hook structure makes UHPC still have residual stiffness and strength after damage. When the anchoring depth of BFRP is 5 mm, the interface bonding stress reaches the maximum, the maximum increase of interface in the pull out bonding stress reaches 74%, and the tensile strength ratio is 1.74.
In order to analyze the influence of basalt fiber reinforced polymer (BFRP) mesh on the bonding performance of ultra-high performance concrete (UHPC), the BFRP-UHPC interface pull-out bonding test (48 pieces) and shear test (21 pieces) were carried out respectively with three parameters of dry/wet bonding type, BFRP mesh anchorage depth and mesh thickness. The effects of BFRP mesh on the failure mode, bonding performance, shear stress slip curve, tensile ratio and toughness were studied. At the same time, the failure mechanism of BFRP-UHPC interface was revealed by SEM. The results show that the anchoring depth directly determines the failure mode of BFRP-UHPC interface. There is a positive correlation between tangential bonding stress and normal bonding stress. The wet bonding strength of BFRP-UHPC interface is higher than that of dry bonding process. With the increase of BFRP thickness and anchorage depth, the interfacial bonding stress between BFRP and UHPC shows a decreasing trend. Steel fiber has remarkable toughening effect on BFRP-UHPC interface, its end hook structure makes UHPC still have residual stiffness and strength after damage. When the anchoring depth of BFRP is 5 mm, the interface bonding stress reaches the maximum, the maximum increase of interface in the pull out bonding stress reaches 74%, and the tensile strength ratio is 1.74.
2023, 40(6): 3486-3498.
doi: 10.13801/j.cnki.fhclxb.20220907.004
Abstract:
The exploitation of resources in polar regions and marine environment leads to the joint action of low temperature, carbonation and chloride ion penetration on concrete structures, which aggravates the deterioration of concrete materials and structures. As a new type of composite material, the durability of ultra-high toughness cementitious composite (UHTCC) is an important index to evaluate its working performance. Through the rapid carbonization test of UHTCC material under ultra-low temperature and chloride ion erosion, the change law of carbonization resistance of UHTCC with different fiber volume contents under complex environment was studied. The results show that with the decrease of temperature, the carbonation resistance of UHTCC material is significantly reduced. When the temperature reaches −160℃, the carbonation depth of UHTCC material increases by about 58.76%. The appropriate amount of fiber has a significant effect on the carbonation resistance of UHTCC material. However, the carbonation resistance of UHTCC material decreases when the content exceeds the optimal content. At the same time, SEM shows that chloride ions can refine the internal pores of concrete and hinder the further diffusion of CO2 inside the material. The regression model of UHTCC carbonation depth in extremely complex environment is proposed, and the research conclusion provides reference for the engineering application of UHTCC in complex environment.
The exploitation of resources in polar regions and marine environment leads to the joint action of low temperature, carbonation and chloride ion penetration on concrete structures, which aggravates the deterioration of concrete materials and structures. As a new type of composite material, the durability of ultra-high toughness cementitious composite (UHTCC) is an important index to evaluate its working performance. Through the rapid carbonization test of UHTCC material under ultra-low temperature and chloride ion erosion, the change law of carbonization resistance of UHTCC with different fiber volume contents under complex environment was studied. The results show that with the decrease of temperature, the carbonation resistance of UHTCC material is significantly reduced. When the temperature reaches −160℃, the carbonation depth of UHTCC material increases by about 58.76%. The appropriate amount of fiber has a significant effect on the carbonation resistance of UHTCC material. However, the carbonation resistance of UHTCC material decreases when the content exceeds the optimal content. At the same time, SEM shows that chloride ions can refine the internal pores of concrete and hinder the further diffusion of CO2 inside the material. The regression model of UHTCC carbonation depth in extremely complex environment is proposed, and the research conclusion provides reference for the engineering application of UHTCC in complex environment.
2023, 40(6): 3499-3512.
doi: 10.13801/j.cnki.fhclxb.20220819.004
Abstract:
In order to study the adhesion properties of basalt fiber reinforced composites (BFRP) ribs and steel-polyvinyl alcohol hybrid fiber reinforced cement matrix composites (steel-PVA mixed ECC), a series of experimental studies and analysis were carried out. The results show that in the range of test steel fiber doping, the mechanical properties and interfacial adhesion properties of the steel fiber doping have a positive effect on the mechanical properties and interfacial adhesion properties of the specimen, and the cubic compressive strength of the steel-PVA hybrid ECC specimen increases with the increase of the amount of steel fiber, and the increase of the steel fiber doping can significantly improve the bonding strength of the BFRP rib and the steel-PVA hybrid ECC; In the test BFRP rib diameter and anchor length range, the diameter of the BFRP rib and the anchoring length have a negative impact on the interfacial bonding performance of the specimen, which increases the diameter of the BFRP rib and the anchoring length. The bond strength of BFRP ribs and steel-PVA hybrid ECC specimens has been reduced to varying degrees. The bond strength of the central pull specimen is basically between 5 and 12 MPa. Among them, the specimen with 0.9vol% steel fiber doping, BFRP rib diameter of 8 mm and anchor length of 5d has the largest bonding strength of 16.82 MPa, while the specimen with unaddressed steel fiber, BFRP rib diameter of 12 mm and anchor length of 5d has the smallest bonding strength, which is 5.46 MPa. The central pull specimen failure mode is divided into BFRP rib extraction failure and BFRP tendon extraction-steel-PVA mixed ECC cleavage failure (pulling-splitting failure), all specimens are basically BFRP rib extraction failure, only a small number of specimens are pulled out-cleavage failure, and only the surface of the specimen with the pull-split failure is broken in contact with the BFRP tendon. The bond-slip model established by using four-stage expressions (micro-slip section, slip section, descending section and residual section) expression can accurately reflect the bonding slip process of BFRP rib and steel-PVA mixed ECC. Based on the measured bond strength and compressive strength values of the test, an expression is established to calculate the basic anchor length of the BFRP rib.
In order to study the adhesion properties of basalt fiber reinforced composites (BFRP) ribs and steel-polyvinyl alcohol hybrid fiber reinforced cement matrix composites (steel-PVA mixed ECC), a series of experimental studies and analysis were carried out. The results show that in the range of test steel fiber doping, the mechanical properties and interfacial adhesion properties of the steel fiber doping have a positive effect on the mechanical properties and interfacial adhesion properties of the specimen, and the cubic compressive strength of the steel-PVA hybrid ECC specimen increases with the increase of the amount of steel fiber, and the increase of the steel fiber doping can significantly improve the bonding strength of the BFRP rib and the steel-PVA hybrid ECC; In the test BFRP rib diameter and anchor length range, the diameter of the BFRP rib and the anchoring length have a negative impact on the interfacial bonding performance of the specimen, which increases the diameter of the BFRP rib and the anchoring length. The bond strength of BFRP ribs and steel-PVA hybrid ECC specimens has been reduced to varying degrees. The bond strength of the central pull specimen is basically between 5 and 12 MPa. Among them, the specimen with 0.9vol% steel fiber doping, BFRP rib diameter of 8 mm and anchor length of 5d has the largest bonding strength of 16.82 MPa, while the specimen with unaddressed steel fiber, BFRP rib diameter of 12 mm and anchor length of 5d has the smallest bonding strength, which is 5.46 MPa. The central pull specimen failure mode is divided into BFRP rib extraction failure and BFRP tendon extraction-steel-PVA mixed ECC cleavage failure (pulling-splitting failure), all specimens are basically BFRP rib extraction failure, only a small number of specimens are pulled out-cleavage failure, and only the surface of the specimen with the pull-split failure is broken in contact with the BFRP tendon. The bond-slip model established by using four-stage expressions (micro-slip section, slip section, descending section and residual section) expression can accurately reflect the bonding slip process of BFRP rib and steel-PVA mixed ECC. Based on the measured bond strength and compressive strength values of the test, an expression is established to calculate the basic anchor length of the BFRP rib.
2023, 40(6): 3513-3528.
doi: 10.13801/j.cnki.fhclxb.20220906.001
Abstract:
In order to study the bonding performance between basalt fiber reinforced polymer (BFRP) bars and low alkalinity sulphoaluminate cement concrete, a total of 90 bonding specimens were tested by central pullout test. The effects of surface morphology of BFRP bars and concrete strength grade on the bonding performance were studied. The experimental results show that sand blasting, fiber winding and ribbed treatments on the surface of BFRP bars can significantly improve the bonding performance, the bond strength between deep ribbed epoxy resin BFRP bar and low alkalinity sulphoaluminate cement concrete with strength grade of 65 MPa is as high as 39.09 MPa, which is much higher than 13.32 MPa of smooth BFRP bar. The effect of strength grade on bond strength of BFRP bar/low alkalinity sulphoaluminate cement concrete is more obvious. In addition, the bonding performance between BFRP bars and low alkalinity sulphoaluminate concrete is higher than that of ordinary portland concrete. Finally, the CMR and mBPE models were used to fit the bond-slip (τ-s) curve of BFRP bar-concrete bond specimens. It is found that the fitting result of CMR model for the ascending segment of the bond-slip curve is better, which clearly and accurately reflects the bond-slip constitutive relationship between BFRP bar and concrete, and provides a key theoretical basis for investigating performance of BFRP-reinforced sulphoaluminate cement concrete structures.
In order to study the bonding performance between basalt fiber reinforced polymer (BFRP) bars and low alkalinity sulphoaluminate cement concrete, a total of 90 bonding specimens were tested by central pullout test. The effects of surface morphology of BFRP bars and concrete strength grade on the bonding performance were studied. The experimental results show that sand blasting, fiber winding and ribbed treatments on the surface of BFRP bars can significantly improve the bonding performance, the bond strength between deep ribbed epoxy resin BFRP bar and low alkalinity sulphoaluminate cement concrete with strength grade of 65 MPa is as high as 39.09 MPa, which is much higher than 13.32 MPa of smooth BFRP bar. The effect of strength grade on bond strength of BFRP bar/low alkalinity sulphoaluminate cement concrete is more obvious. In addition, the bonding performance between BFRP bars and low alkalinity sulphoaluminate concrete is higher than that of ordinary portland concrete. Finally, the CMR and mBPE models were used to fit the bond-slip (τ-s) curve of BFRP bar-concrete bond specimens. It is found that the fitting result of CMR model for the ascending segment of the bond-slip curve is better, which clearly and accurately reflects the bond-slip constitutive relationship between BFRP bar and concrete, and provides a key theoretical basis for investigating performance of BFRP-reinforced sulphoaluminate cement concrete structures.
2023, 40(6): 3529-3538.
doi: 10.13801/j.cnki.fhclxb.20220802.002
Abstract:
To reduce the need to add metal chelators to lipid-based foods to prevent their oxidation, antioxidant packaging is receiving increasing attention. In this study, acrylic acid (AA) was used as the metal chelating ligand and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was used as the substrate. AA was covalently immobi-lised onto the surface of PHBV films by UV grafting to produce the non-releasing PHBV-g-PAA anti-oxidant film with metal chelating ability. The results show that the successful grafting of polyacrylic acid (PAA) onto the surface of PHBV films was demonstrated by structural tests on the composite films. Observation of the composite film morphology and structure by SEM revealed that the density of graft products gradually increased as the grafting time increased. When the grafting time was 20 minutes, the dense uniformity of the PAA grafted layer on the film surface was the best. The crystalline properties of the composite film were tested by DSC and XRD. It showed that the crystallinity decreased from 63.97% to 56.23%, which was conducive to improving the toughness of the film, and the best toughness of the film was achieved at 20 minutes of grafting. Toluidine blue (TBO) staining and flame atomic absorption spectrometry were used to determine the carboxyl density and Cu2+ chelation on the surface of the composite membrane. When the carboxyl density was 392.65 nmol/cm2, the corresponding Cu2+ chelating amount was 115.09 nmol/cm2. The ratio of the two was close to 4, indicating that a stable five-membered ring chelating structure could be generated, thus acting as an antioxidant. Through the mechanical properties test, it was found that the tensile strength and elongation at break of the grafted films both increased first and then decreased. Tensile strength and elongation at break increased by 27.51% and 99.02% respectively at 20 minutes of grafting. The Cu2+ chelating ability and mechanical properties of the prepared non-release antioxidant film are better than those of the PHBV film, which has promising applications in the food packaging field.
To reduce the need to add metal chelators to lipid-based foods to prevent their oxidation, antioxidant packaging is receiving increasing attention. In this study, acrylic acid (AA) was used as the metal chelating ligand and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was used as the substrate. AA was covalently immobi-lised onto the surface of PHBV films by UV grafting to produce the non-releasing PHBV-g-PAA anti-oxidant film with metal chelating ability. The results show that the successful grafting of polyacrylic acid (PAA) onto the surface of PHBV films was demonstrated by structural tests on the composite films. Observation of the composite film morphology and structure by SEM revealed that the density of graft products gradually increased as the grafting time increased. When the grafting time was 20 minutes, the dense uniformity of the PAA grafted layer on the film surface was the best. The crystalline properties of the composite film were tested by DSC and XRD. It showed that the crystallinity decreased from 63.97% to 56.23%, which was conducive to improving the toughness of the film, and the best toughness of the film was achieved at 20 minutes of grafting. Toluidine blue (TBO) staining and flame atomic absorption spectrometry were used to determine the carboxyl density and Cu2+ chelation on the surface of the composite membrane. When the carboxyl density was 392.65 nmol/cm2, the corresponding Cu2+ chelating amount was 115.09 nmol/cm2. The ratio of the two was close to 4, indicating that a stable five-membered ring chelating structure could be generated, thus acting as an antioxidant. Through the mechanical properties test, it was found that the tensile strength and elongation at break of the grafted films both increased first and then decreased. Tensile strength and elongation at break increased by 27.51% and 99.02% respectively at 20 minutes of grafting. The Cu2+ chelating ability and mechanical properties of the prepared non-release antioxidant film are better than those of the PHBV film, which has promising applications in the food packaging field.
2023, 40(6): 3539-3552.
doi: 10.13801/j.cnki.fhclxb.20220817.001
Abstract:
The degree of crystallinity of WO3 has a great influence on its electrochromic properties. In this study, crystalline WO3 vertical nanowire arrays were first prepared by solvothermal method, and then a layer of Ti doped tungsten oxide (WO3-Ti) amorphous film was wrapped on the surface by magnetron sputtering technology to obtain crystalline WO3@ amorphous WO3-Ti core-shell composite array structure. It can be observed by SEM and TEM that the thickness of the amorphous film is about 3-7 nm, and the deposition of the amorphous layer does not destroy the nanowire array structure. Compared with pure WO3 nanowires, the absorption peaks of core-shell nanowires have a slight red shift, and XPS detected that the characteristic peaks of W4f and Ti2p before and after recombination have shifted significantly, confirming an interfacial interaction between the shell and the core. The switching speed and coloring efficiency of the optimized WO3@WO3-Ti core-shell nanowires are 2 times and 1.8 times that of the pure WO3 nanowires and the heterostructures exhibit good optical contrast in both visible and near-infrared regions, and have excellent cycling stability, with a contrast retention rate of 95.8% after 3000 cycles.
The degree of crystallinity of WO3 has a great influence on its electrochromic properties. In this study, crystalline WO3 vertical nanowire arrays were first prepared by solvothermal method, and then a layer of Ti doped tungsten oxide (WO3-Ti) amorphous film was wrapped on the surface by magnetron sputtering technology to obtain crystalline WO3@ amorphous WO3-Ti core-shell composite array structure. It can be observed by SEM and TEM that the thickness of the amorphous film is about 3-7 nm, and the deposition of the amorphous layer does not destroy the nanowire array structure. Compared with pure WO3 nanowires, the absorption peaks of core-shell nanowires have a slight red shift, and XPS detected that the characteristic peaks of W4f and Ti2p before and after recombination have shifted significantly, confirming an interfacial interaction between the shell and the core. The switching speed and coloring efficiency of the optimized WO3@WO3-Ti core-shell nanowires are 2 times and 1.8 times that of the pure WO3 nanowires and the heterostructures exhibit good optical contrast in both visible and near-infrared regions, and have excellent cycling stability, with a contrast retention rate of 95.8% after 3000 cycles.
2023, 40(6): 3553-3561.
doi: 10.13801/j.cnki.fhclxb.20220901.003
Abstract:
In order to improve the degradability of polylactic acid (PLA), bamboo fiber (BF) and sodium alginate (SA) were blended with PLA to prepare composite materials. And then the PLA composites were buried in soil for degradation test. The mass loss, morphological properties, FTIR, thermal properties and crystallinity of the PLA composites were measured after degradation. The results shown that both SA and BF can improve the mass loss of PLA composites during degradation. After 21 days of degradation, the mass loss rates of BF/PLA and SA-BF/PLA composites were 0.83% and 2.54%, which were 7.55 and 23.09 times higher than that of pure PLA (0.11%), respectively. A large number of cracks and depressions appeared on the surface of SA-BF/PLA composites after degradation, which increased the contact area between the PLA composites and the soil, and thus accelerated the degradation of the PLA composites. The mass loss rate of PLA materials was very low after degradation, but the carbanyl group of PLA materials increased significantly, this indicated that soil degradation could lead to the fracture of some PLA long-chain polymers into small molecules. Compared with pure PLA, the crystallinity of BF/PLA and SA-BF/PLA composites was significantly reduced, this meant that SA and BF could reduce the crystallinity of the PLA composites and enhance their degradability. The results indicated that SA and BF can improve the degradability of PLA composites. The results would provide theoretical reference for the preparation of highly degradable PLA composites.
In order to improve the degradability of polylactic acid (PLA), bamboo fiber (BF) and sodium alginate (SA) were blended with PLA to prepare composite materials. And then the PLA composites were buried in soil for degradation test. The mass loss, morphological properties, FTIR, thermal properties and crystallinity of the PLA composites were measured after degradation. The results shown that both SA and BF can improve the mass loss of PLA composites during degradation. After 21 days of degradation, the mass loss rates of BF/PLA and SA-BF/PLA composites were 0.83% and 2.54%, which were 7.55 and 23.09 times higher than that of pure PLA (0.11%), respectively. A large number of cracks and depressions appeared on the surface of SA-BF/PLA composites after degradation, which increased the contact area between the PLA composites and the soil, and thus accelerated the degradation of the PLA composites. The mass loss rate of PLA materials was very low after degradation, but the carbanyl group of PLA materials increased significantly, this indicated that soil degradation could lead to the fracture of some PLA long-chain polymers into small molecules. Compared with pure PLA, the crystallinity of BF/PLA and SA-BF/PLA composites was significantly reduced, this meant that SA and BF could reduce the crystallinity of the PLA composites and enhance their degradability. The results indicated that SA and BF can improve the degradability of PLA composites. The results would provide theoretical reference for the preparation of highly degradable PLA composites.
2023, 40(6): 3562-3570.
doi: 10.13801/j.cnki.fhclxb.20220915.004
Abstract:
Organic dye-sensitized upconversion nanomaterials can expand the absorption of near-infrared light, but dye-aggregation on the surface of nanoparticles limits the improvement of upconversion luminescence. In this paper, sodium 4-(2-((E)-2-((E)-3-((E)-2-(3,3-dimethyl-1-(4-sulfonatobutyl)-1,3-dihydro-2H-benzo[f]indol-2-ylidene)ethylidene)-2-(4-(1,2,2-triphenylvinyl)phenoxy)cyclohex-1-en-1-yl)vinyl)-3,3-dimethyl-3H-benzo[f]indol-1-ium-1-yl)butane-1-sulfonate (CyBTSO) containing tetrastyrene group was synthesized from cyanine IR820 in the presence of strong alkali. IR820 and CyBTSO sensitized upconversion nanocomposites were prepared by a self-assembly method, and their structures and morphologies were characterized. The photophysical properties of dyes in solution and condensed state, as well as the upconversion luminescence of dye-sensitized nanocomposites were investigated. The relationship between molecular structure and upconversion luminescence was systematically studied. It is found that the introduction of tetrastyrene group is not only beneficial to improve the fluorescence quantum yield and lifetime of CyBTSO, but also to enhance its stability and inhibit its aggregation on the nanoparticle surface. Compared with IR820, the stability and the loading amount of CyBTSO on the nanoparticle surface are increased by 1.7 and 3 times, respectively. As a result, a 69-fold enhancement of upconversion luminescence in CyBTSO-sensitized nanocompo-sites excited at 808 nm is achieved compared to that in β-NaYF4:Yb20%, Er2% excited at 980 nm. This work provides a theoretical reference for the development of upconversion materials with high upconversion efficiency and stability.
Organic dye-sensitized upconversion nanomaterials can expand the absorption of near-infrared light, but dye-aggregation on the surface of nanoparticles limits the improvement of upconversion luminescence. In this paper, sodium 4-(2-((E)-2-((E)-3-((E)-2-(3,3-dimethyl-1-(4-sulfonatobutyl)-1,3-dihydro-2H-benzo[f]indol-2-ylidene)ethylidene)-2-(4-(1,2,2-triphenylvinyl)phenoxy)cyclohex-1-en-1-yl)vinyl)-3,3-dimethyl-3H-benzo[f]indol-1-ium-1-yl)butane-1-sulfonate (CyBTSO) containing tetrastyrene group was synthesized from cyanine IR820 in the presence of strong alkali. IR820 and CyBTSO sensitized upconversion nanocomposites were prepared by a self-assembly method, and their structures and morphologies were characterized. The photophysical properties of dyes in solution and condensed state, as well as the upconversion luminescence of dye-sensitized nanocomposites were investigated. The relationship between molecular structure and upconversion luminescence was systematically studied. It is found that the introduction of tetrastyrene group is not only beneficial to improve the fluorescence quantum yield and lifetime of CyBTSO, but also to enhance its stability and inhibit its aggregation on the nanoparticle surface. Compared with IR820, the stability and the loading amount of CyBTSO on the nanoparticle surface are increased by 1.7 and 3 times, respectively. As a result, a 69-fold enhancement of upconversion luminescence in CyBTSO-sensitized nanocompo-sites excited at 808 nm is achieved compared to that in β-NaYF4:Yb20%, Er2% excited at 980 nm. This work provides a theoretical reference for the development of upconversion materials with high upconversion efficiency and stability.
2023, 40(6): 3571-3582.
doi: 10.13801/j.cnki.fhclxb.20220905.003
Abstract:
The ceramic/ultra-high molecular weight polyethylene (UHMWPE) composite armor plate is widely used in the ballistic protection field because of its excellent performance of light weight and high strength. It dissipates the kinetic energy of the projectile through the breaking of the ceramic and the deformation of the back plate. The energy absorption of ceramic fragmentation is the main mode of dissipating kinetic energy of armor piercing projectile. Therefore, it is important to analyze the fracture process and damage evolution characteristics of ceramic to optimize the protective performance of ceramic composite armor. The B4C was used as panel material, and UHMWPE laminate was used as back plate material. B4C/UHMWPE composite armor plate was prepared by resin film infusion. The composite armor plate was impacted by 54-types 12.7 mm armor piercing projectile at the velocity of (488±10) m/s to study the anti-penetration performance. Based on X-ray computed tomography (CT) technology and fracture morphology observation, the ballistic response mechanism of composite armor plate was analyzed. Further, the fragmentation behavior and characteristic parameters of B4C ceramics were explored. The results show that the damage region of B4C ceramics presents a double cone shape. The response region of the ceramic includes the advanced fragmentation zone on the back face of the ceramic plate, the remaining ceramic plate after ballistic penetration, and the fragment-complete pulverization zone directly below the projectile. There is an obvious positive correlation between the free surface cone angle of B4C ceramics and the anti-penetration performance of composite armor plate. The response process of B4C/UHMWPE composite armor plate includes shock wave propagation process and the generation of free surface formation in ceramics, B4C ceramic fragmentation process, and the coupling process of compression, shear, and tension of UHMWPE laminate.
The ceramic/ultra-high molecular weight polyethylene (UHMWPE) composite armor plate is widely used in the ballistic protection field because of its excellent performance of light weight and high strength. It dissipates the kinetic energy of the projectile through the breaking of the ceramic and the deformation of the back plate. The energy absorption of ceramic fragmentation is the main mode of dissipating kinetic energy of armor piercing projectile. Therefore, it is important to analyze the fracture process and damage evolution characteristics of ceramic to optimize the protective performance of ceramic composite armor. The B4C was used as panel material, and UHMWPE laminate was used as back plate material. B4C/UHMWPE composite armor plate was prepared by resin film infusion. The composite armor plate was impacted by 54-types 12.7 mm armor piercing projectile at the velocity of (488±10) m/s to study the anti-penetration performance. Based on X-ray computed tomography (CT) technology and fracture morphology observation, the ballistic response mechanism of composite armor plate was analyzed. Further, the fragmentation behavior and characteristic parameters of B4C ceramics were explored. The results show that the damage region of B4C ceramics presents a double cone shape. The response region of the ceramic includes the advanced fragmentation zone on the back face of the ceramic plate, the remaining ceramic plate after ballistic penetration, and the fragment-complete pulverization zone directly below the projectile. There is an obvious positive correlation between the free surface cone angle of B4C ceramics and the anti-penetration performance of composite armor plate. The response process of B4C/UHMWPE composite armor plate includes shock wave propagation process and the generation of free surface formation in ceramics, B4C ceramic fragmentation process, and the coupling process of compression, shear, and tension of UHMWPE laminate.
2023, 40(6): 3583-3593.
doi: 10.13801/j.cnki.fhclxb.20220803.001
Abstract:
In order to obtain stable superhydrophobic properties on Al alloy surface and further expand the industrial application of Al alloy material, a simple, flexible and reliable preparation method of superhydrophobic surface was studied. Firstly, based on the structural characteristics of superhydrophobic surface, single factor control variable method and response surface method were used to select and optimize the laser machining parameters. The (super) hydrophobic surface was obtained by picosecond laser etching and stearic acid treatment. The influence of micro-nano structure on surface wettability was studied by controlling laser scanning distance to indirectly control surface topography. The surface wettability, morphology and chemical composition of the samples were analyzed by contact angle measuring instrument, SEM, confocal microscope and FTIR. The results show that the optimal laser etching parameters are as follows: Number of scanning is 2 times, scanning speed is 460 mm/s, frequency is 835 kHz, average power is 21 W; The surface with scanning interval of 20-80 μm exists superhydrophobicity, and the surface with scanning interval of 100-160 μm exists hydrophobicity. The maximum contact angle is 154° when the scanning interval is 20 μm and 80 μm, and the surface has low adhesion. This paper has guiding significance for obtaining stable superhydrophobicity on metal surface quickly.
In order to obtain stable superhydrophobic properties on Al alloy surface and further expand the industrial application of Al alloy material, a simple, flexible and reliable preparation method of superhydrophobic surface was studied. Firstly, based on the structural characteristics of superhydrophobic surface, single factor control variable method and response surface method were used to select and optimize the laser machining parameters. The (super) hydrophobic surface was obtained by picosecond laser etching and stearic acid treatment. The influence of micro-nano structure on surface wettability was studied by controlling laser scanning distance to indirectly control surface topography. The surface wettability, morphology and chemical composition of the samples were analyzed by contact angle measuring instrument, SEM, confocal microscope and FTIR. The results show that the optimal laser etching parameters are as follows: Number of scanning is 2 times, scanning speed is 460 mm/s, frequency is 835 kHz, average power is 21 W; The surface with scanning interval of 20-80 μm exists superhydrophobicity, and the surface with scanning interval of 100-160 μm exists hydrophobicity. The maximum contact angle is 154° when the scanning interval is 20 μm and 80 μm, and the surface has low adhesion. This paper has guiding significance for obtaining stable superhydrophobicity on metal surface quickly.
2023, 40(6): 3594-3600.
doi: 10.13801/j.cnki.fhclxb.20220831.001
Abstract:
8mol%Y2O3-stabilized ZrO2 (8mol% Yttria-stabilized zirconia, 8YSZ) is widely used as thermal barrier coatings (TBCs) to reduce heat transfer between hot gases and metallic components in gas-turbine engines. However, with the increase of service temperature, it’s difficult to study the thermal performance of 8YSZ. The influence of the model size effects on thermal conductivity and ion diffusion of 8YSZ were investigated through non-equilibrium molecular dynamics simulations (NEMD). Besides, the ion diffusion and thermal transport behavior of YSZ were explored under service conditions. Using cubic 8YSZ(c-8YSZ) as the study object, the thermal conductivity was calculated for model cross-sectional areas of 4a×4a, 5a×5a and 6a×6a (Lattice constant a) at simulated service temperatures of 1273-1473 K. It was found that the cross-sectional area had a small effect on the calculated results. When the cross-sectional area of 5a×5a was selected, the thermal conductivity calculations of the models with different structure lengths of 5a, 15a, 25a, 35a, 45a, 50a, 55a, 60a and 65a were compared, and the size effect was studied to determine 5a×5a×60a as the best size of the model. The thermal transport mechanism of c-8YSZ at 1273-1473 K was also revealed, and the different phonon scattering between c-8YSZ and tetragonal 8YSZ(t-8YSZ) was also found. It was found that enhanced phonon scattering can effectively suppress the thermal transport capacity of YSZ in service, which provides a theoretical basis for improving the thermal insulation performance of thermal barrier coatings in high temperature service.
8mol%Y2O3-stabilized ZrO2 (8mol% Yttria-stabilized zirconia, 8YSZ) is widely used as thermal barrier coatings (TBCs) to reduce heat transfer between hot gases and metallic components in gas-turbine engines. However, with the increase of service temperature, it’s difficult to study the thermal performance of 8YSZ. The influence of the model size effects on thermal conductivity and ion diffusion of 8YSZ were investigated through non-equilibrium molecular dynamics simulations (NEMD). Besides, the ion diffusion and thermal transport behavior of YSZ were explored under service conditions. Using cubic 8YSZ(c-8YSZ) as the study object, the thermal conductivity was calculated for model cross-sectional areas of 4a×4a, 5a×5a and 6a×6a (Lattice constant a) at simulated service temperatures of 1273-1473 K. It was found that the cross-sectional area had a small effect on the calculated results. When the cross-sectional area of 5a×5a was selected, the thermal conductivity calculations of the models with different structure lengths of 5a, 15a, 25a, 35a, 45a, 50a, 55a, 60a and 65a were compared, and the size effect was studied to determine 5a×5a×60a as the best size of the model. The thermal transport mechanism of c-8YSZ at 1273-1473 K was also revealed, and the different phonon scattering between c-8YSZ and tetragonal 8YSZ(t-8YSZ) was also found. It was found that enhanced phonon scattering can effectively suppress the thermal transport capacity of YSZ in service, which provides a theoretical basis for improving the thermal insulation performance of thermal barrier coatings in high temperature service.
2023, 40(6): 3601-3612.
doi: 10.13801/j.cnki.fhclxb.20220809.002
Abstract:
The mechanical properties and load distribution of single-lap composite hybrid bonded/bolted joints under tensile loading were investigated experimentally and numerically. The damage loads, failure modes, and load distribution of the multi-bolt mechanical joints and the hybrid bonded/bolted joints were tested. The results show that the failure modes of the laminates are a mixture of tensile and extrusion damage for both joints, and the failure mode of the adhesive layer is adhesive peeling in the hybrid bonded/bolted joints. The presence of the adhesive layer makes the load distribution of the hybrid joints more uneven, so the overall structural damage load of the mechanical joints is as slightly greater than that of the hybrid bonded/bolted joints. ABAQUS display solver was used to establish the progressive damage model for multi-bolt mechanical and hybrid bonded/bolted joints. The VUMAT subroutine was used to compile the damage criterion of the composite material and to simulate the failure of the adhesive layer using the cohesive element. The model can effectively predict the damage load, failure mode and load distribution of the structure. The hybrid joint's adhesive layer damage evolution mechanism was described, and the influence of the adhesive layer on the load distribution during the loading process was analyzed. The results of the load distribution indicate that the load distribution of the mechanical joints shows a "basin" distribution with high sides and low middle. The hybrid joints' adhesive layer delays the bolt loading and changes the ratio of load distribution, which makes the outermost bolt take more load and accelerates the damage to the structure.
The mechanical properties and load distribution of single-lap composite hybrid bonded/bolted joints under tensile loading were investigated experimentally and numerically. The damage loads, failure modes, and load distribution of the multi-bolt mechanical joints and the hybrid bonded/bolted joints were tested. The results show that the failure modes of the laminates are a mixture of tensile and extrusion damage for both joints, and the failure mode of the adhesive layer is adhesive peeling in the hybrid bonded/bolted joints. The presence of the adhesive layer makes the load distribution of the hybrid joints more uneven, so the overall structural damage load of the mechanical joints is as slightly greater than that of the hybrid bonded/bolted joints. ABAQUS display solver was used to establish the progressive damage model for multi-bolt mechanical and hybrid bonded/bolted joints. The VUMAT subroutine was used to compile the damage criterion of the composite material and to simulate the failure of the adhesive layer using the cohesive element. The model can effectively predict the damage load, failure mode and load distribution of the structure. The hybrid joint's adhesive layer damage evolution mechanism was described, and the influence of the adhesive layer on the load distribution during the loading process was analyzed. The results of the load distribution indicate that the load distribution of the mechanical joints shows a "basin" distribution with high sides and low middle. The hybrid joints' adhesive layer delays the bolt loading and changes the ratio of load distribution, which makes the outermost bolt take more load and accelerates the damage to the structure.
2023, 40(6): 3613-3625.
doi: 10.13801/j.cnki.fhclxb.20220901.002
Abstract:
With the continuous exploitation of marine resources, the preparation of in-situ all-coral concrete on islands and reefs has become a key technology for the construction and protection of island projects. In order to investigate the effect of different organic non-metallic fiber admixture on the mechanical properties of all-coral concrete, the dynamic mechanical properties were investigated by using the Split Hopkinson Pressure bar (SHPB) test and the impact process was numerically simulated by LS-DYNA. The results show that the static compressive strength of all-coral concrete can reach 113 MPa when the organic fiber mass percent is 1.2wt%, which is an increase of about 7.5% compared with the coral concrete without fiber dosing. Under the dynamic test, the dynamic compressive strength can reach 247 MPa at a strain rate of 120 s−1, which is about 32.6% higher than that of the specimens without fiber admixture. The toughness index of all-coral concrete also increases with the increase of organic fiber admixture. In addition, the integrity of coral concrete specimens increases under the same impact conditions with the increase of organic fiber admixture. The error between dynamic strength test values and simulated values is 7% to be within the allowable error.
With the continuous exploitation of marine resources, the preparation of in-situ all-coral concrete on islands and reefs has become a key technology for the construction and protection of island projects. In order to investigate the effect of different organic non-metallic fiber admixture on the mechanical properties of all-coral concrete, the dynamic mechanical properties were investigated by using the Split Hopkinson Pressure bar (SHPB) test and the impact process was numerically simulated by LS-DYNA. The results show that the static compressive strength of all-coral concrete can reach 113 MPa when the organic fiber mass percent is 1.2wt%, which is an increase of about 7.5% compared with the coral concrete without fiber dosing. Under the dynamic test, the dynamic compressive strength can reach 247 MPa at a strain rate of 120 s−1, which is about 32.6% higher than that of the specimens without fiber admixture. The toughness index of all-coral concrete also increases with the increase of organic fiber admixture. In addition, the integrity of coral concrete specimens increases under the same impact conditions with the increase of organic fiber admixture. The error between dynamic strength test values and simulated values is 7% to be within the allowable error.
2023, 40(6): 3626-3639.
doi: 10.13801/j.cnki.fhclxb.20220720.002
Abstract:
Carbon fiber reinforced plastics (CFRP) are of high specific strength, specific stiffness and significant lightweight effect. Therefore, CFRP thin-walled structures are widely used as energy-absorbing devices in engineering fields. This paper took unidirectional CFRP as research object. The micro-scale structural parameters and fiber volume fraction were obtained by using scanning electron microscope. Then, a representative volume element (RVE) was established, which was capable to accurately reflect its micro morphology. By applying periodic boundary conditions and unit load, the macro equivalent elastic parameters were acquired and then verified by experimental tests. Subsequently, the failure criterion and damage evolution equation based on micromechanics were developed. Combined with the mechanical characteristics of unidirectional CFRP, the macro damage model was developed, and finally forming a set of multi-scale damage model based on micro failure. On this basis, the crashworthiness performance of CFRP thin-walled circular tube under axial quasi-static load was numerically explored, and the numerical results were verified through the crushing test. Based on the verified multi-scale finite element model, the effects of carbon fiber ply angle and carbon fiber volume fraction on the crashworthiness were investi-gated. The results show that the ply angle and carbon fiber volume fraction have great impact on the crashworthiness characteristics of CFRP thin-walled structures.
Carbon fiber reinforced plastics (CFRP) are of high specific strength, specific stiffness and significant lightweight effect. Therefore, CFRP thin-walled structures are widely used as energy-absorbing devices in engineering fields. This paper took unidirectional CFRP as research object. The micro-scale structural parameters and fiber volume fraction were obtained by using scanning electron microscope. Then, a representative volume element (RVE) was established, which was capable to accurately reflect its micro morphology. By applying periodic boundary conditions and unit load, the macro equivalent elastic parameters were acquired and then verified by experimental tests. Subsequently, the failure criterion and damage evolution equation based on micromechanics were developed. Combined with the mechanical characteristics of unidirectional CFRP, the macro damage model was developed, and finally forming a set of multi-scale damage model based on micro failure. On this basis, the crashworthiness performance of CFRP thin-walled circular tube under axial quasi-static load was numerically explored, and the numerical results were verified through the crushing test. Based on the verified multi-scale finite element model, the effects of carbon fiber ply angle and carbon fiber volume fraction on the crashworthiness were investi-gated. The results show that the ply angle and carbon fiber volume fraction have great impact on the crashworthiness characteristics of CFRP thin-walled structures.
2023, 40(6): 3640-3650.
doi: 10.13801/j.cnki.fhclxb.20220811.006
Abstract:
The current study is an experimental and numerical investigation of the buckling of steel-carbon fiber reinforced polymer (CFRP) hybrid cylinders. Two groups of steel-CFRP hybrid and steel-only cylinders were manufactured. Geometric measurements and hydrostatic experiments were performed to determine the geometric and buckling properties of the cylinders. Linear eigenvalue and nonlinear analyses were performed to examine the buckling properties of the samples. The finite element model of each sample was established in accordance with the sample’s real geometric shape. The experimental and numerical data agree favorably. Furthermore, the effect of wrapped angle and layers in the hybrid cylinders on the cylinders’ critical buckling load was investigated. The results indicate that the experimental results obtained for the four cylinders are repeatable. The maximum difference between the experimental collapse loads is 8.29% and 6.77% for the hybrid and steel-only cylinders, respectively. The stiffness provided by CFRP approximately is 1.7 times the loading capacity of the steel-only cylinders. The damage of steel layer of hybrid cylinders is smaller than steel-only cylinders. As the wrapped layers increase, the wrapped angle of CFRP layers of hybrid decreases. The optimal range of wrapped angle is 65°-85°. Wrapped layers have less effect on critical buckling load of hybrid cylinders with the wrapped angle of 65°-85°. The maximum and minimum difference errors are 7.56% and 0.57%, respectively.
The current study is an experimental and numerical investigation of the buckling of steel-carbon fiber reinforced polymer (CFRP) hybrid cylinders. Two groups of steel-CFRP hybrid and steel-only cylinders were manufactured. Geometric measurements and hydrostatic experiments were performed to determine the geometric and buckling properties of the cylinders. Linear eigenvalue and nonlinear analyses were performed to examine the buckling properties of the samples. The finite element model of each sample was established in accordance with the sample’s real geometric shape. The experimental and numerical data agree favorably. Furthermore, the effect of wrapped angle and layers in the hybrid cylinders on the cylinders’ critical buckling load was investigated. The results indicate that the experimental results obtained for the four cylinders are repeatable. The maximum difference between the experimental collapse loads is 8.29% and 6.77% for the hybrid and steel-only cylinders, respectively. The stiffness provided by CFRP approximately is 1.7 times the loading capacity of the steel-only cylinders. The damage of steel layer of hybrid cylinders is smaller than steel-only cylinders. As the wrapped layers increase, the wrapped angle of CFRP layers of hybrid decreases. The optimal range of wrapped angle is 65°-85°. Wrapped layers have less effect on critical buckling load of hybrid cylinders with the wrapped angle of 65°-85°. The maximum and minimum difference errors are 7.56% and 0.57%, respectively.
2023, 40(6): 3651-3661.
doi: 10.13801/j.cnki.fhclxb.20220825.003
Abstract:
The bending and vibration characteristics of the curved carbon fiber reinforced polymer pyramidal sandwich structure were studied. The hot pressing one-time molding process was used to prepare the curved carbon fiber reinforced polymer pyramidal sandwich structure. A three-point bending test was conducted to explore the bending damage load and damage mode of the structure. The results show that the load-displacement curve of the structure can be divided into 4 stages: Linear stage, damage initiation stage, damage evolution stage and failure stage. The main failure modes are panel collapse and node failure. The ABAQUS display solver was used to establish the effective bending and vibration model. The failure modes and load-displacement curves of the bending damage process, the structural vibration modes and natural frequencies were obtained. The effects of different parameters (geometric parameters, material properties) on the bending and vibration performance were discussed, and the natural frequencies were compared to the impact of various boundary conditions. The results show that an increase in relative density (panel thickness, core diameter) increases the bending failure load and natural frequency of the structure. But increasing the core angle ω leads to a decrease in the bending failure load and natural frequency. The greater the specific stiffness of the material is, the higher the natural frequency will be.
The bending and vibration characteristics of the curved carbon fiber reinforced polymer pyramidal sandwich structure were studied. The hot pressing one-time molding process was used to prepare the curved carbon fiber reinforced polymer pyramidal sandwich structure. A three-point bending test was conducted to explore the bending damage load and damage mode of the structure. The results show that the load-displacement curve of the structure can be divided into 4 stages: Linear stage, damage initiation stage, damage evolution stage and failure stage. The main failure modes are panel collapse and node failure. The ABAQUS display solver was used to establish the effective bending and vibration model. The failure modes and load-displacement curves of the bending damage process, the structural vibration modes and natural frequencies were obtained. The effects of different parameters (geometric parameters, material properties) on the bending and vibration performance were discussed, and the natural frequencies were compared to the impact of various boundary conditions. The results show that an increase in relative density (panel thickness, core diameter) increases the bending failure load and natural frequency of the structure. But increasing the core angle ω leads to a decrease in the bending failure load and natural frequency. The greater the specific stiffness of the material is, the higher the natural frequency will be.
2023, 40(6): 3662-3672.
doi: 10.13801/j.cnki.fhclxb.20220913.002
Abstract:
Molecular dynamics (MD) method was used to investigate the effect of the number of graphene nanosheets (GNs) layers and the number of sheets in each layer on the mechanical reinforcement of GNs/Al composite at different compression stages. The results show that the increase of GNs layers and the number of GNs sheets increases the enhancement effect of elastic modulus, yield strength and maximum stress strength of the composite. When the reinforcement layer is composed of 3 or more GNs sheets, double maximum stress peaks appear in the compression curve. At the late compression stage, the fracture of GNs results in the anisotropy of the composite, and the transverse deformation of the composite in the zigzag direction of GNs is larger than that in the armchair direction. When the thickness of metal layer is less than 3 nm, the confined layer slip model is not applicable.
Molecular dynamics (MD) method was used to investigate the effect of the number of graphene nanosheets (GNs) layers and the number of sheets in each layer on the mechanical reinforcement of GNs/Al composite at different compression stages. The results show that the increase of GNs layers and the number of GNs sheets increases the enhancement effect of elastic modulus, yield strength and maximum stress strength of the composite. When the reinforcement layer is composed of 3 or more GNs sheets, double maximum stress peaks appear in the compression curve. At the late compression stage, the fracture of GNs results in the anisotropy of the composite, and the transverse deformation of the composite in the zigzag direction of GNs is larger than that in the armchair direction. When the thickness of metal layer is less than 3 nm, the confined layer slip model is not applicable.
2023, 40(6): 3673-3682.
doi: 10.13801/j.cnki.fhclxb.20220907.006
Abstract:
In order to solve the problem of weak interlaminar shear resistance of T-shaped laminate composites, the weaving process of composite preform was reasonably designed, and the T-shaped fabric was woven by SGA598 small sample loom. The T-shaped fabric was prepared by vacuum assisted resin transfer molding (VARTM) process, and its impact resistance under low velocity impact was studied. The geometric and material models were established by using the finite element software ABAQUS to simulate the impact response process under different impact energies. The results show that the T-shaped stiffened plate has high impact resistance, and the simulation results are in good agreement with the experimental results. The finite element model has good reliability.
In order to solve the problem of weak interlaminar shear resistance of T-shaped laminate composites, the weaving process of composite preform was reasonably designed, and the T-shaped fabric was woven by SGA598 small sample loom. The T-shaped fabric was prepared by vacuum assisted resin transfer molding (VARTM) process, and its impact resistance under low velocity impact was studied. The geometric and material models were established by using the finite element software ABAQUS to simulate the impact response process under different impact energies. The results show that the T-shaped stiffened plate has high impact resistance, and the simulation results are in good agreement with the experimental results. The finite element model has good reliability.
2023, 40(6): 3683-3694.
doi: 10.13801/j.cnki.fhclxb.20220913.003
Abstract:
Poisson's ratio is one of the important parameters in the analysis of mechanical properties of materials and structures. In this paper, the nonlinear evolution behavior of major Poisson's ratio of 2D-C/SiC composites was studied. Firstly, based on Mini composite model and cross-ply laminate model, the thermal residual stress calculation model of 2D-C/SiC composites was established considering the transverse isotropic property of fiber. Secondly, the major Poisson's ratio calculation model of 2D-C/SiC composites was established by using shear-lag theory and classical laminate theory while considering the damage and thermal residual stress release mechanisms of the material. Finally, the strain response and Poisson's ratio evolution of the material were characterized by experiments, and the theoretical model was analyzed and verified. The results show that the internal thermal residual stress of 2D-C/SiC composites is large, and the release of thermal residual stress during tensile damage is responsible for the negative Poisson's ratio. The model prediction results of stress-strain curve and Poisson's ratio evolution curve are in good agreement with the tested curves, which indicates the accuracy and reasonability of the theoretical analysis model.
Poisson's ratio is one of the important parameters in the analysis of mechanical properties of materials and structures. In this paper, the nonlinear evolution behavior of major Poisson's ratio of 2D-C/SiC composites was studied. Firstly, based on Mini composite model and cross-ply laminate model, the thermal residual stress calculation model of 2D-C/SiC composites was established considering the transverse isotropic property of fiber. Secondly, the major Poisson's ratio calculation model of 2D-C/SiC composites was established by using shear-lag theory and classical laminate theory while considering the damage and thermal residual stress release mechanisms of the material. Finally, the strain response and Poisson's ratio evolution of the material were characterized by experiments, and the theoretical model was analyzed and verified. The results show that the internal thermal residual stress of 2D-C/SiC composites is large, and the release of thermal residual stress during tensile damage is responsible for the negative Poisson's ratio. The model prediction results of stress-strain curve and Poisson's ratio evolution curve are in good agreement with the tested curves, which indicates the accuracy and reasonability of the theoretical analysis model.
