Latest Issue
2024, Volume 41, Issue 7
2024,
41(7):
3301-3321.
doi: 10.13801/j.cnki.fhclxb.20231208.001
Abstract:
Polymer materials find wide applications in various fields such as superconducting technology, aerospace, electronic circuits, power batteries, heat exchangers, among others. With the increasing demands for miniaturization, densification, and high power of devices, the overall heat dissipation requirements have escalated. However, polymers, serving as crucial materials in device encapsulation and bonding processes, exhibit a low thermal conductivity of only 0.2 W/(m∙K), which falls significantly short of current heat dissipation needs. Therefore, there is an urgent need to enhance the thermal conductivity of polymers. Constructing continuous thermal pathways within the polymer matrix has been shown to significantly improve the thermal conductivity, often increasing it several times or even tens of times. Hence, utilizing three-dimensional network fillers to reinforce the thermal conductivity of polymers stands out as one of the most commonly employed methods. Accordingly, this paper organizes relevant studies on enhancing the thermal conductivity of polymeric materials through the construction of three-dimensional network fillers. Based on different preparation methods, these are categorized into self-assembly, phase-separation, template-methods, oriented-distribution methods, among others. Finally, a summary analysis is provided from aspects such as the increase in thermal conductivity values due to preparation methods, feasibility, stability, and prospects for the future development of polymer-based thermally conductive composites reinforced by three-dimensional network fillers.
Polymer materials find wide applications in various fields such as superconducting technology, aerospace, electronic circuits, power batteries, heat exchangers, among others. With the increasing demands for miniaturization, densification, and high power of devices, the overall heat dissipation requirements have escalated. However, polymers, serving as crucial materials in device encapsulation and bonding processes, exhibit a low thermal conductivity of only 0.2 W/(m∙K), which falls significantly short of current heat dissipation needs. Therefore, there is an urgent need to enhance the thermal conductivity of polymers. Constructing continuous thermal pathways within the polymer matrix has been shown to significantly improve the thermal conductivity, often increasing it several times or even tens of times. Hence, utilizing three-dimensional network fillers to reinforce the thermal conductivity of polymers stands out as one of the most commonly employed methods. Accordingly, this paper organizes relevant studies on enhancing the thermal conductivity of polymeric materials through the construction of three-dimensional network fillers. Based on different preparation methods, these are categorized into self-assembly, phase-separation, template-methods, oriented-distribution methods, among others. Finally, a summary analysis is provided from aspects such as the increase in thermal conductivity values due to preparation methods, feasibility, stability, and prospects for the future development of polymer-based thermally conductive composites reinforced by three-dimensional network fillers.
2024,
41(7):
3322-3334.
doi: 10.13801/j.cnki.fhclxb.20231213.002
Abstract:
With the rapid development of economy, the pollution of heavy metal ions in water poses a threat to human health and ecosystem. Hydrogels have great potential in the treatment of heavy metal ions because of their good adsorption properties, renewability and low toxicity. This paper discusses the research progress in recent years on the preparation of hydrogels (cellulose-based hydrogels, hemicellulose-based hydrogels, lignin-based hydrogels, etc.) for the adsorption of heavy metals from agricultural solid wastes at home and abroad. The synthesis of agricultural solid waste based hydrogels, the adsorption effect, adsorption mechanism, and analytical methods for the removal of heavy metals are also discussed, and the effects of heavy metal adsorption by industrial solid waste based and other solid waste based hydrogels are enumerated. In order to help the researchers to have a deeper understanding of the investigation of heavy metal adsorption by agricultural solid waste based hydrogels.
With the rapid development of economy, the pollution of heavy metal ions in water poses a threat to human health and ecosystem. Hydrogels have great potential in the treatment of heavy metal ions because of their good adsorption properties, renewability and low toxicity. This paper discusses the research progress in recent years on the preparation of hydrogels (cellulose-based hydrogels, hemicellulose-based hydrogels, lignin-based hydrogels, etc.) for the adsorption of heavy metals from agricultural solid wastes at home and abroad. The synthesis of agricultural solid waste based hydrogels, the adsorption effect, adsorption mechanism, and analytical methods for the removal of heavy metals are also discussed, and the effects of heavy metal adsorption by industrial solid waste based and other solid waste based hydrogels are enumerated. In order to help the researchers to have a deeper understanding of the investigation of heavy metal adsorption by agricultural solid waste based hydrogels.
2024,
41(7):
3335-3354.
doi: 10.13801/j.cnki.fhclxb.20240229.002
Abstract:
Plant fibers have the advantages of eco-friendliness, lightweight, high strength, sound and heat insulating, and low carbon footprint, etc. These attributes make them highly sought-after for applications in sectors such as automotive, aerospace, construction, packaging, and transportation, particularly when plant fibers are processed into composites with polymers. This paper briefly describes the effects of the types of plant long fibers and extraction methods on their physical properties, and at the same time outlines the effects of plant long fibers on the physical properties of composites when they are used as reinforcement in combination with the fiber orientation distribution, fiber surface modification, composite molding process, and failure modes under tensile loading, as well as summarizes and looks forward to the application of plant long fiber-reinforced biodegradable composites.
Plant fibers have the advantages of eco-friendliness, lightweight, high strength, sound and heat insulating, and low carbon footprint, etc. These attributes make them highly sought-after for applications in sectors such as automotive, aerospace, construction, packaging, and transportation, particularly when plant fibers are processed into composites with polymers. This paper briefly describes the effects of the types of plant long fibers and extraction methods on their physical properties, and at the same time outlines the effects of plant long fibers on the physical properties of composites when they are used as reinforcement in combination with the fiber orientation distribution, fiber surface modification, composite molding process, and failure modes under tensile loading, as well as summarizes and looks forward to the application of plant long fiber-reinforced biodegradable composites.
2024,
41(7):
3359-3375.
doi: 10.13801/j.cnki.fhclxb.20240221.001
Abstract:
As the most cutting-edge, basic and influential science and technology research field, the level of scientific research development is an important symbol to measure the innovation of national science and technology. However, aerospace thermal insulation materials are the most important technical support for the development of aerospace technology, and how to prepare materials with good thermal insulation properties and mechanical strength is of great significance for the development of aerospace technology. Silicon dioxide aerogel with ultra-low thermal conductivity, high porosity, high specific surface area and ultra-low density and other excellent properties, in the deep space probe, solar panels, space shuttle engines, solid rocket boosters and return capsule base and other special engineering equipment materials have a better application prospects. In recent years, with the continuous development of silica aerogel research methods and preparation technology, by compounding it with functional materials with high strength and high temperature resistance, it can synergistically enhance its properties such as thermal insulation and mechanical strength, which is crucial for the development of aerospace special engineering materials. In view of this, this paper briefly describes the development history of silica aerogel, analyzes and summarizes in detail the research progress of aerogel composites formed by compositing silica aerogel with common oxides, fiber-reinforced and organic polymers and other reinforcing materials in the field of aerospace, and mainly comments on the preparation method, structural characteristics, heat insulation, mechanical properties, etc., and looks ahead to the problems, challenges, and future directions of the research and application of silica aerogel composites in this field.
As the most cutting-edge, basic and influential science and technology research field, the level of scientific research development is an important symbol to measure the innovation of national science and technology. However, aerospace thermal insulation materials are the most important technical support for the development of aerospace technology, and how to prepare materials with good thermal insulation properties and mechanical strength is of great significance for the development of aerospace technology. Silicon dioxide aerogel with ultra-low thermal conductivity, high porosity, high specific surface area and ultra-low density and other excellent properties, in the deep space probe, solar panels, space shuttle engines, solid rocket boosters and return capsule base and other special engineering equipment materials have a better application prospects. In recent years, with the continuous development of silica aerogel research methods and preparation technology, by compounding it with functional materials with high strength and high temperature resistance, it can synergistically enhance its properties such as thermal insulation and mechanical strength, which is crucial for the development of aerospace special engineering materials. In view of this, this paper briefly describes the development history of silica aerogel, analyzes and summarizes in detail the research progress of aerogel composites formed by compositing silica aerogel with common oxides, fiber-reinforced and organic polymers and other reinforcing materials in the field of aerospace, and mainly comments on the preparation method, structural characteristics, heat insulation, mechanical properties, etc., and looks ahead to the problems, challenges, and future directions of the research and application of silica aerogel composites in this field.
2024,
41(7):
3372-3388.
doi: 10.13801/j.cnki.fhclxb.20240002.002
Abstract:
Liquid crystal elastomers (LCEs) containing dynamic cross-linking bonds are capable of undergoing macroscopic motion through alterations in volume or shape in response to external stimuli, including light, electricity, or heat. These materials demonstrate remarkable molecular cooperative effects and adaptive properties, offering considerable potential in the fields of soft robotics, artificial muscles, and microfluidics. Effective control of the internal liquid crystal orientation in LCEs is essential for achieving reversible deformation. The breakage and reformation of dynamic bonds not only decouples the construction of cross-linked networks and orientation control, but also enhances the reprocessing properties of materials, enabling new functionalities like remodeling deformation, self-healing, and shape memory. Therefore, the deliberate design and construction of cross-linked network structures, including the selection of cross-linking agents, their structures, and cooperative effects of various networks, are crucial for producing LCEs with exceptional performance and multifunctional integration. This review comprehensively discusses advancements in the preparation and application of LCEs, encompassing liquid crystal orientation control and single/double dynamic cross-linking networks (involving dynamic non-covalent and covalent bonds), and delineates future prospects for development in this field.
Liquid crystal elastomers (LCEs) containing dynamic cross-linking bonds are capable of undergoing macroscopic motion through alterations in volume or shape in response to external stimuli, including light, electricity, or heat. These materials demonstrate remarkable molecular cooperative effects and adaptive properties, offering considerable potential in the fields of soft robotics, artificial muscles, and microfluidics. Effective control of the internal liquid crystal orientation in LCEs is essential for achieving reversible deformation. The breakage and reformation of dynamic bonds not only decouples the construction of cross-linked networks and orientation control, but also enhances the reprocessing properties of materials, enabling new functionalities like remodeling deformation, self-healing, and shape memory. Therefore, the deliberate design and construction of cross-linked network structures, including the selection of cross-linking agents, their structures, and cooperative effects of various networks, are crucial for producing LCEs with exceptional performance and multifunctional integration. This review comprehensively discusses advancements in the preparation and application of LCEs, encompassing liquid crystal orientation control and single/double dynamic cross-linking networks (involving dynamic non-covalent and covalent bonds), and delineates future prospects for development in this field.
Research progress on the regulation of filler particle alignment during physics-assisted 3D printing
2024,
41(7):
3389-3403.
doi: 10.13801/j.cnki.fhclxb.20240030.001
Abstract:
3D printing is a bottom-up, layer-by-layer material additive manufacturing technique. Currently, 3D printing is evolving from prototype manufacturing towards high-performance and functionalization, placing higher demands on the control of printing materials and processes. The orderly arrangement of nanoparticles in 3D printing materials is crucial for enhancing the performance of printed components, yet effectively controlling the orientation of nanoparticles remains challenging. Incorporating physical fields (magnetic, electric, and ultrasonic fields) into the 3D printing process emerges as one of the effective strategies for precise microstructure manipulation of printed items. This approach not only endows the printed components with specific functions but also provides new insights for fabricating multi-scale and multi-responsive structured components. Therefore, physical field-assisted 3D printing has become a research hotspot in recent years. This article begins by briefly describing the types and characteristics of 3D printing technology, emphasizing the importance of physical field assistance in controlling the orientation of nanoparticles. Subsequently, it reviews and summarizes the fundamental principles, material requirements, applications, and performance of physical field-assisted 3D printing in controlling nanoparticle orientation. Finally, the problems and challenges existing in controlling the orientation of filler particles in physical field-assisted 3D printing are summarized, and its future development direction is prospected.
3D printing is a bottom-up, layer-by-layer material additive manufacturing technique. Currently, 3D printing is evolving from prototype manufacturing towards high-performance and functionalization, placing higher demands on the control of printing materials and processes. The orderly arrangement of nanoparticles in 3D printing materials is crucial for enhancing the performance of printed components, yet effectively controlling the orientation of nanoparticles remains challenging. Incorporating physical fields (magnetic, electric, and ultrasonic fields) into the 3D printing process emerges as one of the effective strategies for precise microstructure manipulation of printed items. This approach not only endows the printed components with specific functions but also provides new insights for fabricating multi-scale and multi-responsive structured components. Therefore, physical field-assisted 3D printing has become a research hotspot in recent years. This article begins by briefly describing the types and characteristics of 3D printing technology, emphasizing the importance of physical field assistance in controlling the orientation of nanoparticles. Subsequently, it reviews and summarizes the fundamental principles, material requirements, applications, and performance of physical field-assisted 3D printing in controlling nanoparticle orientation. Finally, the problems and challenges existing in controlling the orientation of filler particles in physical field-assisted 3D printing are summarized, and its future development direction is prospected.
2024,
41(7):
3404-3426.
doi: 10.13801/j.cnki.fhclxb.20231220.004
Abstract:
With the popularity of 5G network and the miniaturization of electromagnetic equipment, electromagnetic radiation has brought certain harm to the surrounding environment and human body. Therefore, it is of great significance to develop new electromagnetic interference shielding materials with excellent comprehensive performance. Ti3C2Tx MXene is a new type of two-dimensional material with unique layered structure, adjustable active surface, ultra-high conductivity and other characteristics. Thus, it exhibits an excellent electromagnetic shielding performance. In recent years, many researches on its preparation method and filler selection have been reported. However, there is little work to summarize Ti3C2Tx matrix composites from the structural design level. High-efficiency structural design can not only reduce the amount of filler, but also improve shielding effectiveness. This article takes the structure as the main thread and summarizes the development trend of Ti3C2Tx based electromagnetic shielding materials in recent years. By analyzing the shielding effectiveness and mechanism, the article focuses on summarizing the influence and role of different structures such as porous structure, layered structure, core-shell structure, other special structures, and their composite structures on the electromagnetic shielding performance of Ti3C2Tx based materials. And key scientific and technical issues that urgently need to be addressed when Ti3C2Tx and its composite materials are used as electromagnetic shielding materials were proposed. Finally, the development prospect of Ti3C2Tx MXene is prospected.
With the popularity of 5G network and the miniaturization of electromagnetic equipment, electromagnetic radiation has brought certain harm to the surrounding environment and human body. Therefore, it is of great significance to develop new electromagnetic interference shielding materials with excellent comprehensive performance. Ti3C2Tx MXene is a new type of two-dimensional material with unique layered structure, adjustable active surface, ultra-high conductivity and other characteristics. Thus, it exhibits an excellent electromagnetic shielding performance. In recent years, many researches on its preparation method and filler selection have been reported. However, there is little work to summarize Ti3C2Tx matrix composites from the structural design level. High-efficiency structural design can not only reduce the amount of filler, but also improve shielding effectiveness. This article takes the structure as the main thread and summarizes the development trend of Ti3C2Tx based electromagnetic shielding materials in recent years. By analyzing the shielding effectiveness and mechanism, the article focuses on summarizing the influence and role of different structures such as porous structure, layered structure, core-shell structure, other special structures, and their composite structures on the electromagnetic shielding performance of Ti3C2Tx based materials. And key scientific and technical issues that urgently need to be addressed when Ti3C2Tx and its composite materials are used as electromagnetic shielding materials were proposed. Finally, the development prospect of Ti3C2Tx MXene is prospected.
2024,
41(7):
3431-3445.
doi: 10.13801/j.cnki.fhclxb.20231214.001
Abstract:
Infected wounds seriously endanger the quality of life and even life and health of human beings, so the development of antimicrobial biomaterials with high efficiency and few side effects for the repair of infected wounds has broad market prospects. Two-dimensional transition metal carbide (MXene) is a new type of two-dimensional sheet material with excellent antibacterial properties, and its antibacterial mechanism mainly includes physical capture theory, infrared thermal effect, reactive oxygen species (ROS) generation theory, intercellular molecular leakage theory, etc., so MXene is expected to become a safer, effective and broad-spectrum antibacterial method. Compared with simple hydrogels, MXene composite hydrogels made of hydrogels encapsulated with MXene have better antibacterial, antioxidant properties and photothermal effects. In this paper, the antimicrobial mechanism of MXene was reviewed, and the researches on the repair of infected wounds by MXene composite hydrogels were comprehensively reviewed and summarized in recent years.
Infected wounds seriously endanger the quality of life and even life and health of human beings, so the development of antimicrobial biomaterials with high efficiency and few side effects for the repair of infected wounds has broad market prospects. Two-dimensional transition metal carbide (MXene) is a new type of two-dimensional sheet material with excellent antibacterial properties, and its antibacterial mechanism mainly includes physical capture theory, infrared thermal effect, reactive oxygen species (ROS) generation theory, intercellular molecular leakage theory, etc., so MXene is expected to become a safer, effective and broad-spectrum antibacterial method. Compared with simple hydrogels, MXene composite hydrogels made of hydrogels encapsulated with MXene have better antibacterial, antioxidant properties and photothermal effects. In this paper, the antimicrobial mechanism of MXene was reviewed, and the researches on the repair of infected wounds by MXene composite hydrogels were comprehensively reviewed and summarized in recent years.
2024,
41(7):
3446-3456.
doi: 10.13801/j.cnki.fhclxb.20240003.005
Abstract:
In recent years, the development of antibacterial materials has received great attention in various fields. The application of antibacterial technology is closely related to human health and has a great development prospect. Ag nanoparticles (Ag NPs) antibacterial agent is one of the most widely used antibacterial agents at present. In this paper, the antibacterial mechanism of Ag NPs antibacterial agent is discussed. Besides, the research progress of composite antibacterial agent composed of Ag NPs and natural antibacterial agent, organic antibacterial agent and inorganic antibacterial agent respectively is introduced. At the same time, the carrier of Ag NPs antibacterial agent was introduced from three aspects: Inorganic carrier, organic carrier and new carrier, which can provide reference for further research and application of Ag NPs antibacterial agent.
In recent years, the development of antibacterial materials has received great attention in various fields. The application of antibacterial technology is closely related to human health and has a great development prospect. Ag nanoparticles (Ag NPs) antibacterial agent is one of the most widely used antibacterial agents at present. In this paper, the antibacterial mechanism of Ag NPs antibacterial agent is discussed. Besides, the research progress of composite antibacterial agent composed of Ag NPs and natural antibacterial agent, organic antibacterial agent and inorganic antibacterial agent respectively is introduced. At the same time, the carrier of Ag NPs antibacterial agent was introduced from three aspects: Inorganic carrier, organic carrier and new carrier, which can provide reference for further research and application of Ag NPs antibacterial agent.
2024,
41(7):
3453-3466.
doi: 10.13801/j.cnki.fhclxb.20231207.001
Abstract:
The high temperature baseline seal with hybrid structure of multiple materials is a novel porous composite, which is composed of thermal insulation core material, metal braided spring tube and ceramic fiber braided tube. It has excellent multi-functional performances, including flexibility, high temperature resistance, abrasion resistance and sealing. It is vital for improving the comprehensive performance of the hot end components, especially for the new generation of high-speed aircraft. Hybrid structure of multiple materials can take advantage of specific attributes of each material to enhance the performance of a product or introduce new functionalities. For the proposed high-temperature baseline, the inner core material plays a role on thermal insulation, and the intermediate superalloy braided spring tube play a dominative effect on the elastic deformation recovery during the dynamic seal condition, and the outer ceramic fiber tube makes a function on heat and wear resistance. The major problem of hybrid structure is emanated from the different property of each component material, the internal relationship between hybrid structure and performance regulation is still unclear. To end this, the characteristics of each component material and fabrication technology of high temperature baseline seal with hybrid structure of multiple materials are firstly introduced. Then, the current research on the theory and numerical model of high temperature baseline are sorted out and summarized. Once more, the main challenges for the key fabrication technology of high-temperature baseline seal and its service ability in the high-temperature and dynamic loading are expounded. Finally, the research development trend and engineering application potentials of novel high-temperature baseline seal with hybrid structure of multiple materials are prospected.
The high temperature baseline seal with hybrid structure of multiple materials is a novel porous composite, which is composed of thermal insulation core material, metal braided spring tube and ceramic fiber braided tube. It has excellent multi-functional performances, including flexibility, high temperature resistance, abrasion resistance and sealing. It is vital for improving the comprehensive performance of the hot end components, especially for the new generation of high-speed aircraft. Hybrid structure of multiple materials can take advantage of specific attributes of each material to enhance the performance of a product or introduce new functionalities. For the proposed high-temperature baseline, the inner core material plays a role on thermal insulation, and the intermediate superalloy braided spring tube play a dominative effect on the elastic deformation recovery during the dynamic seal condition, and the outer ceramic fiber tube makes a function on heat and wear resistance. The major problem of hybrid structure is emanated from the different property of each component material, the internal relationship between hybrid structure and performance regulation is still unclear. To end this, the characteristics of each component material and fabrication technology of high temperature baseline seal with hybrid structure of multiple materials are firstly introduced. Then, the current research on the theory and numerical model of high temperature baseline are sorted out and summarized. Once more, the main challenges for the key fabrication technology of high-temperature baseline seal and its service ability in the high-temperature and dynamic loading are expounded. Finally, the research development trend and engineering application potentials of novel high-temperature baseline seal with hybrid structure of multiple materials are prospected.
2024,
41(7):
3467-3478.
doi: 10.13801/j.cnki.fhclxb.20231106.002
Abstract:
Layered double hydroxide-biochar (LDH-BC) composites, novel biochar-based composite nanomaterials that have been shown to be highly effective in adsorbing pollutants and catalyzing degradation in wastewater treatment. This review provides a thorough and organized overview of the current research on LDH-BC composites, which can be used to inform future studies. The research content provides a summary of the synthesis method of LDH-BC composites, the modification strategy, and the application and mechanism of the composites in wastewater treatment. It is suggested in the outlook section that LDH-BC composites have problems inadequate research such as unclear degradation paths of specific components, less application of composite pollutant systems, and lack of field scale tests. The next step is to explore the above shortages of research further in order to promote the research and application of LDH-BC composites.
Layered double hydroxide-biochar (LDH-BC) composites, novel biochar-based composite nanomaterials that have been shown to be highly effective in adsorbing pollutants and catalyzing degradation in wastewater treatment. This review provides a thorough and organized overview of the current research on LDH-BC composites, which can be used to inform future studies. The research content provides a summary of the synthesis method of LDH-BC composites, the modification strategy, and the application and mechanism of the composites in wastewater treatment. It is suggested in the outlook section that LDH-BC composites have problems inadequate research such as unclear degradation paths of specific components, less application of composite pollutant systems, and lack of field scale tests. The next step is to explore the above shortages of research further in order to promote the research and application of LDH-BC composites.
2024,
41(7):
3483-3493.
doi: 10.13801/j.cnki.fhclxb.20231215.001
Abstract:
Cellulose nanocrystals (CNC) are nanomaterials with excellent mechanical properties, optical properties and surface chemical properties, which have attracted wide attention from researchers in recent years. CNC-based sensors have a single, double and multiple response to external environmental stimuli, such as humidity, gas, pH, solvent, temperature, light and other drive sensing, which makes it in the information encryption, health detection, food, environmental monitoring, energy storage, wearable and other fields show great application potential. In this paper, the key characteristics of CNC are briefly introduced, and the important application development and research mechanism of multi-functional sensors based on CNC are analyzed. Finally, the main problems and challenges in the preparation process of CNC-based sensor materials are summarized, and the reference is provided for improving their performance and functional innovative applications.
Cellulose nanocrystals (CNC) are nanomaterials with excellent mechanical properties, optical properties and surface chemical properties, which have attracted wide attention from researchers in recent years. CNC-based sensors have a single, double and multiple response to external environmental stimuli, such as humidity, gas, pH, solvent, temperature, light and other drive sensing, which makes it in the information encryption, health detection, food, environmental monitoring, energy storage, wearable and other fields show great application potential. In this paper, the key characteristics of CNC are briefly introduced, and the important application development and research mechanism of multi-functional sensors based on CNC are analyzed. Finally, the main problems and challenges in the preparation process of CNC-based sensor materials are summarized, and the reference is provided for improving their performance and functional innovative applications.
2024,
41(7):
3494-3506.
doi: 10.13801/j.cnki.fhclxb.20240011.001
Abstract:
Promoting the use of recycled aggregate concrete is an important way to recycle the building solid waste and promote the sustainable development of ecological environment. Fiber reinforced polymer (FRP) is an effective way to improve the mechanical properties of recycled concrete. Domestic and overseas researchers have carried out experimental research on and theoretical analysis of the characteristic of compressive strength, stress-strain curve, mechanical properties and seismic performance of the FRP wrapped recycled concrete materials and structural member with the different design parameters, such as the replacement rate of recycled aggregate, FRP type, lateral confinement stiffness (number of FRP layers), FRP fully wrapped or strip wrapped, etc. The applicability of the ultimate strength and ultimate strain model of FRP confined ordinary concrete to the test results of FRP confined recycled concrete is also compared. This paper analyzes the research status and shortcomings of FRP confined recycled concrete materials and components, and summarizes the problems that need to be further researched, so as to provide references for the subsequent research and engineering application of FRP confined recycled concrete structures.
Promoting the use of recycled aggregate concrete is an important way to recycle the building solid waste and promote the sustainable development of ecological environment. Fiber reinforced polymer (FRP) is an effective way to improve the mechanical properties of recycled concrete. Domestic and overseas researchers have carried out experimental research on and theoretical analysis of the characteristic of compressive strength, stress-strain curve, mechanical properties and seismic performance of the FRP wrapped recycled concrete materials and structural member with the different design parameters, such as the replacement rate of recycled aggregate, FRP type, lateral confinement stiffness (number of FRP layers), FRP fully wrapped or strip wrapped, etc. The applicability of the ultimate strength and ultimate strain model of FRP confined ordinary concrete to the test results of FRP confined recycled concrete is also compared. This paper analyzes the research status and shortcomings of FRP confined recycled concrete materials and components, and summarizes the problems that need to be further researched, so as to provide references for the subsequent research and engineering application of FRP confined recycled concrete structures.
2024,
41(7):
3507-3518.
doi: 10.13801/j.cnki.fhclxb.20240015.001
Abstract:
With the rapid development of new energy vehicles, the traditional graphite carbon-based anodes can no longer meet the increasing demand for high performance lithium-ion battery, especially in terms of capacity. Silicon, boasting an exceptionally high theoretical capacity, serves as a promising anode material capable of significantly enhancing battery performance, showcasing tremendous development potential, where the silicon source materials, the morphology and size of the silicon particles, and the fabrication process play dominant roles on the performance of silicon-based anodes. The present review provides a comprehensive overview of the recent research progresses on the silicon-based anode materials, with a specific emphasis on the selection of silicon source materials, silicon nanostructuring technologies, and the preparation processes. Moreover, it accentuates the challenges and existing problems associated with the different silicon sources as well as the related preparation processes for the silicon-based anode materials, which will eventually provide deep insights for the advancement of silicon-based anodes in lithium-ion battery.
With the rapid development of new energy vehicles, the traditional graphite carbon-based anodes can no longer meet the increasing demand for high performance lithium-ion battery, especially in terms of capacity. Silicon, boasting an exceptionally high theoretical capacity, serves as a promising anode material capable of significantly enhancing battery performance, showcasing tremendous development potential, where the silicon source materials, the morphology and size of the silicon particles, and the fabrication process play dominant roles on the performance of silicon-based anodes. The present review provides a comprehensive overview of the recent research progresses on the silicon-based anode materials, with a specific emphasis on the selection of silicon source materials, silicon nanostructuring technologies, and the preparation processes. Moreover, it accentuates the challenges and existing problems associated with the different silicon sources as well as the related preparation processes for the silicon-based anode materials, which will eventually provide deep insights for the advancement of silicon-based anodes in lithium-ion battery.
2024,
41(7):
3519-3528.
doi: 10.13801/j.cnki.fhclxb.20240008.006
Abstract:
As the global energy consumption increasing rapidly, development and application of thermoelectric devices have become one of the effective ways to solve the problem. Among them, bismuth telluride (Bi2Te3)-based flexible devices attract widespread attention because they have been applied in the wearable sector gradually. However, due to the limitations of high material cost, rigid structure, and other factors, it is difficult for Bi2Te3-based flexible thermoelectric devices to achieve flexible wearable applications while maintaining efficient thermoelectric properties. This paper systematically reviews the current research progress of Bi2Te3-based flexible thermoelectric devices in terms of material composites and flexible structure design, especially in terms of flexible structure design, which covers three types of structures: Ingot-, film- and yarn- shaped. Finally, it summarizes and analyzes the possible future challenges and development trends of Bi2Te3-based flexible thermoelectric devices, to facilitate the realization of a wide range of applications for thermoelectric devices in the wearable field.
As the global energy consumption increasing rapidly, development and application of thermoelectric devices have become one of the effective ways to solve the problem. Among them, bismuth telluride (Bi2Te3)-based flexible devices attract widespread attention because they have been applied in the wearable sector gradually. However, due to the limitations of high material cost, rigid structure, and other factors, it is difficult for Bi2Te3-based flexible thermoelectric devices to achieve flexible wearable applications while maintaining efficient thermoelectric properties. This paper systematically reviews the current research progress of Bi2Te3-based flexible thermoelectric devices in terms of material composites and flexible structure design, especially in terms of flexible structure design, which covers three types of structures: Ingot-, film- and yarn- shaped. Finally, it summarizes and analyzes the possible future challenges and development trends of Bi2Te3-based flexible thermoelectric devices, to facilitate the realization of a wide range of applications for thermoelectric devices in the wearable field.
2024,
41(7):
3529-3539.
doi: 10.13801/j.cnki.fhclxb.20231130.001
Abstract:
Recycled carbon fibers (RCF) are mostly fluffy and disorganized short fiber bundles, which can be reoriented based on wet fiber orientation technology. Conventional fiber-reinforced composites are usually layered with fibers in a unidirectional direction, which makes it difficult to fully utilize the gain effect of the fibers on open-hole parts, but the structural properties of the composites can be improved by curved layups of the fibers. The optimal configuration parameters of certain RCF content with different concentrations of hydroxyethyl cellulose (HEC) were investigated by designing fiber dispersion experiments. Using the self-constructed fiber orientation path control device, the prepared dispersion was spread to obtain fiber mats with different trajectories and shapes, and the orientation effect of RCF was evaluated based on a two-dimensional fast Fourier transform (2D FFT). The open-hole specimens of RCF/epoxy resin (EP) composites were prepared by molding, and the effects of different layup paths on the load-bearing capacity of the open-hole specimens were analyzed. The results show that the optimal HEC concentration is 14 g/L when the 6 mm RCF content is 6 g/L. The open-hole specimens prepared according to the curved path effectively reduce the stress concentration at the open hole, and the ultimate load is increased by 69.5% and 35.9% compared with the open-hole specimens prepared according to the unordered path and the horizontal path, respectively. The study broadens the design freedom of RCF/EP composite structures and provides a reference for realizing high-performance reuse of RCF.
Recycled carbon fibers (RCF) are mostly fluffy and disorganized short fiber bundles, which can be reoriented based on wet fiber orientation technology. Conventional fiber-reinforced composites are usually layered with fibers in a unidirectional direction, which makes it difficult to fully utilize the gain effect of the fibers on open-hole parts, but the structural properties of the composites can be improved by curved layups of the fibers. The optimal configuration parameters of certain RCF content with different concentrations of hydroxyethyl cellulose (HEC) were investigated by designing fiber dispersion experiments. Using the self-constructed fiber orientation path control device, the prepared dispersion was spread to obtain fiber mats with different trajectories and shapes, and the orientation effect of RCF was evaluated based on a two-dimensional fast Fourier transform (2D FFT). The open-hole specimens of RCF/epoxy resin (EP) composites were prepared by molding, and the effects of different layup paths on the load-bearing capacity of the open-hole specimens were analyzed. The results show that the optimal HEC concentration is 14 g/L when the 6 mm RCF content is 6 g/L. The open-hole specimens prepared according to the curved path effectively reduce the stress concentration at the open hole, and the ultimate load is increased by 69.5% and 35.9% compared with the open-hole specimens prepared according to the unordered path and the horizontal path, respectively. The study broadens the design freedom of RCF/EP composite structures and provides a reference for realizing high-performance reuse of RCF.
2024,
41(7):
3540-3547.
doi: 10.13801/j.cnki.fhclxb.20231101.001
Abstract:
Four 20 mm cubic 3D braided carbon/carbon (C/C) composite specimens were scanned by micro X-ray computed tomography (XCT) to obtain internal microstructure images with a voxel resolution of 18.27 μm. A deep learning based semantic segmentation algorithm was then used to train a large number of 2D XCT images to achieve intelligent identification and segmentation of rods, fiber bundles, matrix, pores, delamination and cracks of these specimens. The results show that: (1) The XCT scanning can characterize the distribution and morphology of the above components and defects with high resolutions, and the dominant defect is delamination between adjacent fiber bundle layers; (2) Since the grey values in the CT images of all micro components of C/C composites are very close, it is impossible for the traditional threshold segmentation method to segment the different components, whereas the deep learning based algorithm is able to effectively filter noise and artifacts and segment all the components and defects with high accuracy and at a prediction speed of about two orders faster than manual image labelling. This deep learning algorithm thus provides a promising tool to construct high-resolution numerical models for further studies such as performance optimization of C/C composites.
Four 20 mm cubic 3D braided carbon/carbon (C/C) composite specimens were scanned by micro X-ray computed tomography (XCT) to obtain internal microstructure images with a voxel resolution of 18.27 μm. A deep learning based semantic segmentation algorithm was then used to train a large number of 2D XCT images to achieve intelligent identification and segmentation of rods, fiber bundles, matrix, pores, delamination and cracks of these specimens. The results show that: (1) The XCT scanning can characterize the distribution and morphology of the above components and defects with high resolutions, and the dominant defect is delamination between adjacent fiber bundle layers; (2) Since the grey values in the CT images of all micro components of C/C composites are very close, it is impossible for the traditional threshold segmentation method to segment the different components, whereas the deep learning based algorithm is able to effectively filter noise and artifacts and segment all the components and defects with high accuracy and at a prediction speed of about two orders faster than manual image labelling. This deep learning algorithm thus provides a promising tool to construct high-resolution numerical models for further studies such as performance optimization of C/C composites.
2024,
41(7):
3544-3556.
doi: 10.13801/j.cnki.fhclxb.20231205.003
Abstract:
Polylactic acid (PLA) as a biobased degradable plastic has increasingly become a research hotspot. However, PLA's application in packaging and electrical appliances is limited due to its high combustibility. In order to solve the above problem, lignin containing silicon-nitrogen synergistic (Si-NLig) was synthesized by modification of alkali lignin (Lig), and its TGA results showed that the temperature corresponding to mass loss 5wt% of material (T5%) increased by 20℃ and the high temperature residue increased from 2.3% to 25.5% in air. And Si-NLig was used as a charring agent, and compounded with ammonium polyphosphate (APP) to prepared flame retardant polylactic acid (Si-NLig-APP/PLA) by melt blending and hot-press molding, and the PLAs' flame retardant properties, mechanical properties, and combustion behavior, were investigated. The results showed that addition of 10wt% Si-NLig-APP with the mass ratio 1∶4 made Si-NLig-8%APP/PLA reach the limiting oxygen index (LOI) value of 27% and the vertical burning UL-94 V-0 level, while the LOI value of Lig-8%APP/PLA with Lig as charring agent at the same condition was 26% and the vertical burning UL-94 only passed V-2 rating. Meanwhile, the peak heat release rate (PHRR) reduced by 27% compared to Lig-8%APP/PLA. Raman spectroscopy was used to characterize the structure of the residual char after cone calorimeter testing, it was found that the degree of graphitization of Si-NLig-8%APP/PLA increased by 36.7% compared to that of Lig-8%APP/PLA, which provides a theoretical basis for its good flame retardancy. Introduction of Si-NLig led to the enhancement of mechanical properties of the flame retardant PLA with tensile strength increasing by 21%. It can be seen that Si-NLig has potential application prospect in the field of halogen-free flame retardant PLA.
Polylactic acid (PLA) as a biobased degradable plastic has increasingly become a research hotspot. However, PLA's application in packaging and electrical appliances is limited due to its high combustibility. In order to solve the above problem, lignin containing silicon-nitrogen synergistic (Si-NLig) was synthesized by modification of alkali lignin (Lig), and its TGA results showed that the temperature corresponding to mass loss 5wt% of material (T5%) increased by 20℃ and the high temperature residue increased from 2.3% to 25.5% in air. And Si-NLig was used as a charring agent, and compounded with ammonium polyphosphate (APP) to prepared flame retardant polylactic acid (Si-NLig-APP/PLA) by melt blending and hot-press molding, and the PLAs' flame retardant properties, mechanical properties, and combustion behavior, were investigated. The results showed that addition of 10wt% Si-NLig-APP with the mass ratio 1∶4 made Si-NLig-8%APP/PLA reach the limiting oxygen index (LOI) value of 27% and the vertical burning UL-94 V-0 level, while the LOI value of Lig-8%APP/PLA with Lig as charring agent at the same condition was 26% and the vertical burning UL-94 only passed V-2 rating. Meanwhile, the peak heat release rate (PHRR) reduced by 27% compared to Lig-8%APP/PLA. Raman spectroscopy was used to characterize the structure of the residual char after cone calorimeter testing, it was found that the degree of graphitization of Si-NLig-8%APP/PLA increased by 36.7% compared to that of Lig-8%APP/PLA, which provides a theoretical basis for its good flame retardancy. Introduction of Si-NLig led to the enhancement of mechanical properties of the flame retardant PLA with tensile strength increasing by 21%. It can be seen that Si-NLig has potential application prospect in the field of halogen-free flame retardant PLA.
2024,
41(7):
3561-3571.
doi: 10.13801/j.cnki.fhclxb.20231129.002
Abstract:
Red mud/polydimethylsiloxane (PDMS) composites were prepared by filling red mud in flexible PDMS by mechanical stirring, vacuum magnetic stirring defoamination and heating curing. The structure, microstructure, mechanical and thermal properties of the composites were characterized and analyzed. The results show that: Red mud as a cross-linked node and self-lubricating particle improves the elastic modulus, tensile strength, hardness Shore, impact strength and friction and wear properties of the composites, among which the impact strength increases significantly from 41.13 kJ·m−2 to 273.33 kJ·m−2, an increase of 565%. In addition, red mud as a non-combustible also improves the flame retardant performance of the composites, the limiting oxygen index increases from 25.7% to 34.7%, an increase of 35%, into the range of refractory materials (> 27%). This is expected to expand the application field of this silicone material, and provide a reference for the resource utilization of red mud and the research of new red mud/polymer composites.
Red mud/polydimethylsiloxane (PDMS) composites were prepared by filling red mud in flexible PDMS by mechanical stirring, vacuum magnetic stirring defoamination and heating curing. The structure, microstructure, mechanical and thermal properties of the composites were characterized and analyzed. The results show that: Red mud as a cross-linked node and self-lubricating particle improves the elastic modulus, tensile strength, hardness Shore, impact strength and friction and wear properties of the composites, among which the impact strength increases significantly from 41.13 kJ·m−2 to 273.33 kJ·m−2, an increase of 565%. In addition, red mud as a non-combustible also improves the flame retardant performance of the composites, the limiting oxygen index increases from 25.7% to 34.7%, an increase of 35%, into the range of refractory materials (> 27%). This is expected to expand the application field of this silicone material, and provide a reference for the resource utilization of red mud and the research of new red mud/polymer composites.
2024,
41(7):
3568-3576.
doi: 10.13801/j.cnki.fhclxb.20231223.001
Abstract:
Polyether sulfone (PES) resin possesses excellent heat resistance, mechanical properties, and high-temperature stability, making it suitable for the production of high-performance thermoplastic resin-based carbon fiber composite materials. However, due to the poor interfacial adhesion between PES resin and commercial grade carbon fibers, PES resin based carbon fiber composites exhibit poor interfacial properties. In previous studies, it discovered that thermosetting cyanate ester (CE) resin had advantages such as good melt flowability, a curing temperature close to that of PES resin, and some compatibility with PES resin. In this paper, CE resin is utilized as an interface transition layer for PES resin-based carbon fiber composite materials, leveraging the transition layer resin's excellent bonding capability with the carbon fiber surface sizing agents and its strong mechanical interlocking with PES resin, the impact of the thermosetting resin transition layer on the interface performance of thermoplastic resin-based composite materials is investigated. The results demonstrate that introducing a CE resin transition layer can enhance the interfacial bonding performance of PES-based carbon fiber composite materials. Compared to carbon fiber (CF)/PES composite materials, the CF/(10%CE-PES)-L composite material with a 10wt%CE resin transition layer exhibits an 18.7% increase in flexural strength, a 24.2% increase in interlaminar shear strength, additionally, the glass transition temperature (Tg) of the CF/(5%CE-PES)-L composite material increased from 166℃ to 179℃. The method of preparing thermoplastic resin-based carbon fiber composites by adding an interlayer between the thermoplastic resin matrix and commercial carbon fibers has addressed the issue of poor interface performance in thermoplastic resin-based carbon fiber composites. This investigation important research insights and a theoretical basis for its engineering applications.
Polyether sulfone (PES) resin possesses excellent heat resistance, mechanical properties, and high-temperature stability, making it suitable for the production of high-performance thermoplastic resin-based carbon fiber composite materials. However, due to the poor interfacial adhesion between PES resin and commercial grade carbon fibers, PES resin based carbon fiber composites exhibit poor interfacial properties. In previous studies, it discovered that thermosetting cyanate ester (CE) resin had advantages such as good melt flowability, a curing temperature close to that of PES resin, and some compatibility with PES resin. In this paper, CE resin is utilized as an interface transition layer for PES resin-based carbon fiber composite materials, leveraging the transition layer resin's excellent bonding capability with the carbon fiber surface sizing agents and its strong mechanical interlocking with PES resin, the impact of the thermosetting resin transition layer on the interface performance of thermoplastic resin-based composite materials is investigated. The results demonstrate that introducing a CE resin transition layer can enhance the interfacial bonding performance of PES-based carbon fiber composite materials. Compared to carbon fiber (CF)/PES composite materials, the CF/(10%CE-PES)-L composite material with a 10wt%CE resin transition layer exhibits an 18.7% increase in flexural strength, a 24.2% increase in interlaminar shear strength, additionally, the glass transition temperature (Tg) of the CF/(5%CE-PES)-L composite material increased from 166℃ to 179℃. The method of preparing thermoplastic resin-based carbon fiber composites by adding an interlayer between the thermoplastic resin matrix and commercial carbon fibers has addressed the issue of poor interface performance in thermoplastic resin-based carbon fiber composites. This investigation important research insights and a theoretical basis for its engineering applications.
2024,
41(7):
3577-3586.
doi: 10.13801/j.cnki.fhclxb.20231128.001
Abstract:
One of the important ways to improve the mechanical properties of continuous glass fiber reinforced nylon 6 composites (cGF/PA6) is to improve the interface interactions between glass fiber and nylon 6. In this study, star-branched polyamide 6 (SPA6) was applied to cGF/PA6 composite system, and continuous glass fiber reinforced nylon composites with different contents of SPA6 (cGF/PA6-SPA6) were prepared by melt extrusion combined with hot pressing. The characterization of contact angle indicates that the polarity between SPA6 and cGF is more similar. DSC results show that there is not much difference in the melting temperature among PA6, SPA6 and PA6-SPA6 composite matrix, and both the crystallization temperature and crystallinity of PA6-SPA6 are increased. The flexural strength of PA6-SPA6 matrix is lower than that of PA6 and SPA6 measured by three-point flexural tests. However, compared with cGF/PA6, the flexural strength of cGF/5wt%SPA6 and cGF/10wt%SPA6 composites increased by 4.9% and 6.4%, respectively, and the shearing strength of cGF/5wt%SPA6 and cGF/10wt%SPA6 composites increased by 16.7% and 15.6%, respectively. The impact strength of cGF/PA6 and cGF/SPA6 composites is 12 times and 26.3 times that of PA6 and SPA6, respectively. Combined with the observation of impact fracture morphology, it can be inferred that adding 5wt% or 10wt% SPA6 to cGF/PA6 composites can improve the flexural and shearing strength of the composites, while having little influence on the impact strength, and considering its cost-effectiveness, it proves to be of practical value for applications.
One of the important ways to improve the mechanical properties of continuous glass fiber reinforced nylon 6 composites (cGF/PA6) is to improve the interface interactions between glass fiber and nylon 6. In this study, star-branched polyamide 6 (SPA6) was applied to cGF/PA6 composite system, and continuous glass fiber reinforced nylon composites with different contents of SPA6 (cGF/PA6-SPA6) were prepared by melt extrusion combined with hot pressing. The characterization of contact angle indicates that the polarity between SPA6 and cGF is more similar. DSC results show that there is not much difference in the melting temperature among PA6, SPA6 and PA6-SPA6 composite matrix, and both the crystallization temperature and crystallinity of PA6-SPA6 are increased. The flexural strength of PA6-SPA6 matrix is lower than that of PA6 and SPA6 measured by three-point flexural tests. However, compared with cGF/PA6, the flexural strength of cGF/5wt%SPA6 and cGF/10wt%SPA6 composites increased by 4.9% and 6.4%, respectively, and the shearing strength of cGF/5wt%SPA6 and cGF/10wt%SPA6 composites increased by 16.7% and 15.6%, respectively. The impact strength of cGF/PA6 and cGF/SPA6 composites is 12 times and 26.3 times that of PA6 and SPA6, respectively. Combined with the observation of impact fracture morphology, it can be inferred that adding 5wt% or 10wt% SPA6 to cGF/PA6 composites can improve the flexural and shearing strength of the composites, while having little influence on the impact strength, and considering its cost-effectiveness, it proves to be of practical value for applications.
2024,
41(7):
3591-3601.
doi: 10.13801/j.cnki.fhclxb.20231106.001
Abstract:
In order to obtain upconversion nanomaterials with bright red emission for deep bioimaging applications, a series of Tm3+, Ho3+ doped NaErF4@NaYF4 core-shell upconversion nanocrystals were prepared by thermal decomposition method, and their morphology, structure and luminescence properties were characterized. The results show that NaErF4, NaErF4∶Tm3+ and NaErF4∶Ho3+ bare core all exhibit hexagonal phase structure and good spherical morphology, with average sizes of 28.01 nm 23.19 nm, and 27.89 nm, respectively. After coating NaYF4 inert shell, the crystal phase remains unchanged, but the morphology became short rod-like, and the average length increases to 37.82 nm, 38.51 nm, 42.65 nm. Under the excitation of 980 nm near-infrared light, NaErF4, NaErF4∶Tm3+ and NaErF4∶Ho3+ show obvious red emission due to the 4F9/2→4I15/2 transition of Er3+, and the luminescence intensity and lifetime increase significantly after coating NaYF4 inert shell. In particular, the luminescence intensity of NaErF4@NaYF4 core-shell sample is about 1787 times that of NaErF4 bare core, and the lifetime is 2.04 ms. In addition, compared with NaErF4@NaYF4, the Tm3+, Ho3+ ions in the NaErF4∶(Tm3+, Ho3+)@NaYF4 system act as energy trapping centers and generate energy transfer with Er3+, resulting in a larger red-green emission peak ratio (R/G), and the luminescence color is closer to red, which is consistent with the chromaticity coordinate (CIE) color region. Finally, according to the relationship between luminescence intensity and excitation power, the upconversion luminescence enhanced mechanism and the possible energy transfer process are analyzed in detail.
In order to obtain upconversion nanomaterials with bright red emission for deep bioimaging applications, a series of Tm3+, Ho3+ doped NaErF4@NaYF4 core-shell upconversion nanocrystals were prepared by thermal decomposition method, and their morphology, structure and luminescence properties were characterized. The results show that NaErF4, NaErF4∶Tm3+ and NaErF4∶Ho3+ bare core all exhibit hexagonal phase structure and good spherical morphology, with average sizes of 28.01 nm 23.19 nm, and 27.89 nm, respectively. After coating NaYF4 inert shell, the crystal phase remains unchanged, but the morphology became short rod-like, and the average length increases to 37.82 nm, 38.51 nm, 42.65 nm. Under the excitation of 980 nm near-infrared light, NaErF4, NaErF4∶Tm3+ and NaErF4∶Ho3+ show obvious red emission due to the 4F9/2→4I15/2 transition of Er3+, and the luminescence intensity and lifetime increase significantly after coating NaYF4 inert shell. In particular, the luminescence intensity of NaErF4@NaYF4 core-shell sample is about 1787 times that of NaErF4 bare core, and the lifetime is 2.04 ms. In addition, compared with NaErF4@NaYF4, the Tm3+, Ho3+ ions in the NaErF4∶(Tm3+, Ho3+)@NaYF4 system act as energy trapping centers and generate energy transfer with Er3+, resulting in a larger red-green emission peak ratio (R/G), and the luminescence color is closer to red, which is consistent with the chromaticity coordinate (CIE) color region. Finally, according to the relationship between luminescence intensity and excitation power, the upconversion luminescence enhanced mechanism and the possible energy transfer process are analyzed in detail.
2024,
41(7):
3602-3612.
doi: 10.13801/j.cnki.fhclxb.20231121.001
Abstract:
1, 4-cyclohexanedimethanol-based polycarbonates have desired thermodynamic property yet poor degradation capability. Introducing aliphatic units into the molecular chains could effectively improve the degradability at the severe expense of thermodynamic properties. For this reason, biobased 2, 5-tetrahydrofurandimethanol (THFDM) with cyclic ether rigidity was selected as the modification unit and poly(1, 4-cyclohexyldimethylene-co-2,5-tetrahydrofurandimethanol carbonate) (PCThC) copolymers with higher molecular weights were synthesized via melt ester exchange polycondensation method. The composition and microstructure were investigated by NMR, which confirmed the random distribution among the copolymer components. DSC and WAXD results reveals that the introduction of THFDM units break the regular arrangement of the molecular chains in PCThCs, reduce the crystallisation ability, which promote the transition from the semi-crystalline to amorphous. Furthermore, the rigid ring structure in THFDM prevents the rapid declination of glass transition temperature (Tg) and keeps the good thermal stability. The ring structure in the THFDM endow higher stiffness and better mechanical performance for the polymer. The ether bonds in THFDM enhance the hydrophilicity of the PCThC copolymers, resulting in a gradual acceleration of the hydrolysis rate. The copolymers exhibit pleasant degradation ability either under acidic or alkaline environment.
1, 4-cyclohexanedimethanol-based polycarbonates have desired thermodynamic property yet poor degradation capability. Introducing aliphatic units into the molecular chains could effectively improve the degradability at the severe expense of thermodynamic properties. For this reason, biobased 2, 5-tetrahydrofurandimethanol (THFDM) with cyclic ether rigidity was selected as the modification unit and poly(1, 4-cyclohexyldimethylene-co-2,5-tetrahydrofurandimethanol carbonate) (PCThC) copolymers with higher molecular weights were synthesized via melt ester exchange polycondensation method. The composition and microstructure were investigated by NMR, which confirmed the random distribution among the copolymer components. DSC and WAXD results reveals that the introduction of THFDM units break the regular arrangement of the molecular chains in PCThCs, reduce the crystallisation ability, which promote the transition from the semi-crystalline to amorphous. Furthermore, the rigid ring structure in THFDM prevents the rapid declination of glass transition temperature (Tg) and keeps the good thermal stability. The ring structure in the THFDM endow higher stiffness and better mechanical performance for the polymer. The ether bonds in THFDM enhance the hydrophilicity of the PCThC copolymers, resulting in a gradual acceleration of the hydrolysis rate. The copolymers exhibit pleasant degradation ability either under acidic or alkaline environment.
2024,
41(7):
3609-3619.
doi: 10.13801/j.cnki.fhclxb.20231120.004
Abstract:
PEG60-polylactic acid (PLA40)-CNT0.6-X(y) phase-change energy storage composites were prepared in this paper by physically hybridizing carbon nanotubes (CNT) with BN, Al2O3, and copper powder (Cu), respectively, to investigate the effects of nanoparticles with different structures on the shape stability and photovoltaic conversion efficiency of polyethylene glycol (PEG) based phase-change composites. The incorporation of Al2O3 and Cu nanofillers has a minor effect on the electrical conductivity of the PEG-PLA-CNT-X(y) composites. However, the introduction of BN drastically reduces the electrical conductivity of the composites. When the mass ratio of BN reaches 40%, the electrical conductivity of the PEG60-PLA40-CNT0.6-BN(40) composites is only 8.71×10−7 S/m, indicating obvious insulating properties. The spherical Al2O3 nanoparticles were found to be uniformly distributed inside the composites by SEM and EDS energy spectroscopy, and the thermal conductivity and enhancement factor (\begin{document}$ \varPhi $\end{document} \begin{document}$ \eta $\end{document}
PEG60-polylactic acid (PLA40)-CNT0.6-X(y) phase-change energy storage composites were prepared in this paper by physically hybridizing carbon nanotubes (CNT) with BN, Al2O3, and copper powder (Cu), respectively, to investigate the effects of nanoparticles with different structures on the shape stability and photovoltaic conversion efficiency of polyethylene glycol (PEG) based phase-change composites. The incorporation of Al2O3 and Cu nanofillers has a minor effect on the electrical conductivity of the PEG-PLA-CNT-X(y) composites. However, the introduction of BN drastically reduces the electrical conductivity of the composites. When the mass ratio of BN reaches 40%, the electrical conductivity of the PEG60-PLA40-CNT0.6-BN(40) composites is only 8.71×10−7 S/m, indicating obvious insulating properties. The spherical Al2O3 nanoparticles were found to be uniformly distributed inside the composites by SEM and EDS energy spectroscopy, and the thermal conductivity and enhancement factor (
2024,
41(7):
3620-3629.
doi: 10.13801/j.cnki.fhclxb.20231204.002
Abstract:
Carbon-based material supported Cu is an efficient catalyst for methanol oxidative carbonylation to dimethyl carbonate, but Cu nanoparticles are prone to agglomeration and oxidation. Cu-BTC were prepared by hydrothermal method. And then CuOx/C catalysts was prepared by pyrolysis Cu-BTC under N2 atmosphere. The effect of pyrolysis temperature on Cu nanoparticle size, Cu valence state and performance for methanol oxidative carbonylation to dimethyl carbonate were investigated. The characterization results show that increasing the pyrolysis temperature is beneficial to the reduction of Cu2+ to (Cu0+Cu+), but would lead to the agglomeration of Cu nanoparticles. Catalytic activity decreases with the increasing of pyrolysis temperature. CuOx/C-300, prepared by pyrolysis of Cu-BTC at 300℃, shows the optimized catalytic activity and the space-time yield of dimethyl carbonate is 1209 mg·g−1·h−1. This is attributed to the smallest particle size of Cu nanoparticles (7.5 nm). In addition, the space-time yield of dimethyl carbonate decreased to 468 mg·g−1·h−1 after 6 cycle experiments. The main reasons for catalyst inactivation are the oxidation of (Cu0+Cu+) and the agglomeration of Cu nanoparticles.
Carbon-based material supported Cu is an efficient catalyst for methanol oxidative carbonylation to dimethyl carbonate, but Cu nanoparticles are prone to agglomeration and oxidation. Cu-BTC were prepared by hydrothermal method. And then CuOx/C catalysts was prepared by pyrolysis Cu-BTC under N2 atmosphere. The effect of pyrolysis temperature on Cu nanoparticle size, Cu valence state and performance for methanol oxidative carbonylation to dimethyl carbonate were investigated. The characterization results show that increasing the pyrolysis temperature is beneficial to the reduction of Cu2+ to (Cu0+Cu+), but would lead to the agglomeration of Cu nanoparticles. Catalytic activity decreases with the increasing of pyrolysis temperature. CuOx/C-300, prepared by pyrolysis of Cu-BTC at 300℃, shows the optimized catalytic activity and the space-time yield of dimethyl carbonate is 1209 mg·g−1·h−1. This is attributed to the smallest particle size of Cu nanoparticles (7.5 nm). In addition, the space-time yield of dimethyl carbonate decreased to 468 mg·g−1·h−1 after 6 cycle experiments. The main reasons for catalyst inactivation are the oxidation of (Cu0+Cu+) and the agglomeration of Cu nanoparticles.
2024,
41(7):
3630-3642.
doi: 10.13801/j.cnki.fhclxb.20231218.002
Abstract:
2.5D woven SiCf/SiC composites were designed and prepared to meet the requirements of high temperature microwave absorbing structural composites, and the microwave absorbing properties were studied by combining experiment and simulation. The reflection loss of the material was measured by means of the bow method, and the geometrical parameters of the material were extracted by X-ray computed tomography (Micro-CT) to establish a full-thickness mesoscopic model. The reflection loss of the material was simulated and calculated on the CST electromagnetic simulation software, and compared with the experiment results. Based on the theory of equivalent electromagnetic parameters and field distribution map, the microwave-absorbing mechanism is analyzed, and the effects of geometric structure parameters, electromagnetic parameters, electromagnetic field polarization direction and incidence angle on the microwave-absorbing property of materials are studied. The experimental results show that the 2.5D woven SiCf/SiC composites prepared in this paper have an effective absorption bandwidth of 3 GHz in the frequency range of 1-18 GHz, and the maximum reflection loss reaches −17 dB at the absorption peak of 9.3 GHz, which is basically consistent with the simulation results. The composite absorbs electromagnetic microwave mainly through the way of electrical loss, and its good microwave absorption performance is the result of the synergistic effect of structural design and material characteristics. The overall material thickness and fiber dielectric constant are the key factors affecting the microwave absorption performance of 2.5D woven SiCf/SiC composites.
2.5D woven SiCf/SiC composites were designed and prepared to meet the requirements of high temperature microwave absorbing structural composites, and the microwave absorbing properties were studied by combining experiment and simulation. The reflection loss of the material was measured by means of the bow method, and the geometrical parameters of the material were extracted by X-ray computed tomography (Micro-CT) to establish a full-thickness mesoscopic model. The reflection loss of the material was simulated and calculated on the CST electromagnetic simulation software, and compared with the experiment results. Based on the theory of equivalent electromagnetic parameters and field distribution map, the microwave-absorbing mechanism is analyzed, and the effects of geometric structure parameters, electromagnetic parameters, electromagnetic field polarization direction and incidence angle on the microwave-absorbing property of materials are studied. The experimental results show that the 2.5D woven SiCf/SiC composites prepared in this paper have an effective absorption bandwidth of 3 GHz in the frequency range of 1-18 GHz, and the maximum reflection loss reaches −17 dB at the absorption peak of 9.3 GHz, which is basically consistent with the simulation results. The composite absorbs electromagnetic microwave mainly through the way of electrical loss, and its good microwave absorption performance is the result of the synergistic effect of structural design and material characteristics. The overall material thickness and fiber dielectric constant are the key factors affecting the microwave absorption performance of 2.5D woven SiCf/SiC composites.
2024,
41(7):
3643-3655.
doi: 10.13801/j.cnki.fhclxb.20231220.001
Abstract:
The removal efficiency of hydroxyapatite (HAP ) to fluoride was low due to its easy agglomeration during the synthesis process. Based on this, a clean, simple, green and environmentally fiendly electrochemcial synthesis method was applied to improve the fluoride removal efficiency. Polyethylene glycol (PEG), a non ionic surfactant with strong hydrophilicity and excellent dispersion, was added to the mixed support electrolyte for preparing HAP. A new type of HAP composite (PEG/HAP) was prepared on the surface of copper sheet as the working electrode. By contrast to HAP, the crystal structure, pore size, specific surface area, surface morphology, elemental proportion, and functional groups of PEG/HAP were analyzed to reveal the instrinsic mechnism of the higher fluoride removal efficiency of PEG/HAP than HAP. The results show that PEG/HAP and HAP have the same crystal plane structure characteristics, elements and chemical bonds, while the proportion of various elements as well as the absorption peaks and intensity of hydroxyl and phosphate ion functional groups in PEG/HAP have certain differences compared to HAP. PEG transformed HAP from a short rod-shaped surface morphology to a porous and porous structure that facilitated the exchange and adsorption of fluoride ions. Average pore size of PEG/HAP decreased from 16.58 nm of HAP to 11.93 nm, and its specific surface area increased from 24.29 m2/g OF HAP to 29.83 m2/g. Although the adsorption types of PEG/HAP and HAP were both IV type H3 hysteresis loop, and their mesoporous distribution ranges were consistent, the number of micropores and mesopores in PEG/HAP were significantly higher than those in HAP. Although the adsorption reactions of both materials for fluoride ions exhibited entropy increase, endothermic, and spontaneous process characteristics with the adsorption isotherm model conforming to Langmuir-Freundlich, the intra particle diffusion rate constant of PEG/HAP was slightly higher than HAP. Therefore, the maximum adsorption capacity of PEG/HAP for fluoride ions can reach 9.56 mg/g, which was higher than that of HAP of 8.36 mg/g. Compared with 4 times of recycle regeneration for removing fluoride ions of HAP, PEG/HAP can arrived at 6. In addition, the presence of PEG did not affect the change trend of preparation parameters such as electrolyte pH on the adsorption capacity of HAP for fluoride ions. However, PEG increased the adsorption capacity of HAP for fluoride ions. All coexisiting ions such as Cl−, NO3 −, SO4 2−, and CO3 2− did not interfere with the adsorption of fluoride ions for PEG/HAP and HAP.
The removal efficiency of hydroxyapatite (HAP ) to fluoride was low due to its easy agglomeration during the synthesis process. Based on this, a clean, simple, green and environmentally fiendly electrochemcial synthesis method was applied to improve the fluoride removal efficiency. Polyethylene glycol (PEG), a non ionic surfactant with strong hydrophilicity and excellent dispersion, was added to the mixed support electrolyte for preparing HAP. A new type of HAP composite (PEG/HAP) was prepared on the surface of copper sheet as the working electrode. By contrast to HAP, the crystal structure, pore size, specific surface area, surface morphology, elemental proportion, and functional groups of PEG/HAP were analyzed to reveal the instrinsic mechnism of the higher fluoride removal efficiency of PEG/HAP than HAP. The results show that PEG/HAP and HAP have the same crystal plane structure characteristics, elements and chemical bonds, while the proportion of various elements as well as the absorption peaks and intensity of hydroxyl and phosphate ion functional groups in PEG/HAP have certain differences compared to HAP. PEG transformed HAP from a short rod-shaped surface morphology to a porous and porous structure that facilitated the exchange and adsorption of fluoride ions. Average pore size of PEG/HAP decreased from 16.58 nm of HAP to 11.93 nm, and its specific surface area increased from 24.29 m2/g OF HAP to 29.83 m2/g. Although the adsorption types of PEG/HAP and HAP were both IV type H3 hysteresis loop, and their mesoporous distribution ranges were consistent, the number of micropores and mesopores in PEG/HAP were significantly higher than those in HAP. Although the adsorption reactions of both materials for fluoride ions exhibited entropy increase, endothermic, and spontaneous process characteristics with the adsorption isotherm model conforming to Langmuir-Freundlich, the intra particle diffusion rate constant of PEG/HAP was slightly higher than HAP. Therefore, the maximum adsorption capacity of PEG/HAP for fluoride ions can reach 9.56 mg/g, which was higher than that of HAP of 8.36 mg/g. Compared with 4 times of recycle regeneration for removing fluoride ions of HAP, PEG/HAP can arrived at 6. In addition, the presence of PEG did not affect the change trend of preparation parameters such as electrolyte pH on the adsorption capacity of HAP for fluoride ions. However, PEG increased the adsorption capacity of HAP for fluoride ions. All coexisiting ions such as Cl−, NO3 −, SO4 2−, and CO3 2− did not interfere with the adsorption of fluoride ions for PEG/HAP and HAP.
2024,
41(7):
3656-3667.
doi: 10.13801/j.cnki.fhclxb.20240017.001
Abstract:
The development of moisture-resistant room-temperature gas sensors based on semiconductor functional materials has always been a hot and difficult research topic in the field of gas sensors. Considering the high sensitivity and stability of metal oxide semiconductor, the room-temperature gas-sensing behaviors of MXene (Ti3C2Tx) and the hydrophobicity of polytetrafluoroethylene (PTFE), the PTFE/ZnO/MXene composite films were prepared by depositing the PTFE and ZnO layers orderly onto the MXene film surface via a magnetron sputtering method, followed by the construction of the gas sensors based on the composite films. The PTFE/ZnO/MXene composite films were characterized by SEM, TEM and XPS, and the gas-sensing and humidity-resistant properties of the composite films-based gas sensors were investigated. Results show that the PTFE/ZnO/Ti3C2Tx composite films-based gas sensors exhibite good selectivity, high sensitivity, and excellent reproducibility towards ammonia at room temperature. With the increase of the thickness of the PTFE layers, the humidity resistance of the composite films-based gas sensors gradually increases, but at the cost of sensitivity.
The development of moisture-resistant room-temperature gas sensors based on semiconductor functional materials has always been a hot and difficult research topic in the field of gas sensors. Considering the high sensitivity and stability of metal oxide semiconductor, the room-temperature gas-sensing behaviors of MXene (Ti3C2Tx) and the hydrophobicity of polytetrafluoroethylene (PTFE), the PTFE/ZnO/MXene composite films were prepared by depositing the PTFE and ZnO layers orderly onto the MXene film surface via a magnetron sputtering method, followed by the construction of the gas sensors based on the composite films. The PTFE/ZnO/MXene composite films were characterized by SEM, TEM and XPS, and the gas-sensing and humidity-resistant properties of the composite films-based gas sensors were investigated. Results show that the PTFE/ZnO/Ti3C2Tx composite films-based gas sensors exhibite good selectivity, high sensitivity, and excellent reproducibility towards ammonia at room temperature. With the increase of the thickness of the PTFE layers, the humidity resistance of the composite films-based gas sensors gradually increases, but at the cost of sensitivity.
2024,
41(7):
3668-3676.
doi: 10.13801/j.cnki.fhclxb.20231206.003
Abstract:
In order to solve the problem of interface end peeling of textile reinforced concrete (TRC) reinforced concrete beam structures, an end self-locking technique was proposed to anchor the TRC slabs at the bottom of the beams. Owing to the end anchorage provided by this technique, the TRC slab can continue to carry the load even if interfacial debonding occurs. However, compared with the fiber sheet, the fiber mesh has poor synergistic stress performance due to much larger gaps between the fiber bundles, and it is doubtful whether self-locking can be achieved without treatment. In order to improve the utilization of fiber mesh strength, this paper investigates the end-anchor self-locking enhancement effect through the end self-locking anchored fiber mesh tensile test. Measures such as increasing physical friction or adding chemical bonding to the fiber grid are taken to stretch it to failure. The failure modes and load-strain curves of each specimen are analyzed and compared, and a formula for calculating the bearing capacity of the fiber grid after enhancement is proposed. The results show that even if the size of the fiber grid is limited, the strength utilization rate of the fiber grid under end anchoring is increased by 60.66% by reinforcement measures, and the tensile bearing capacity of the three-layer grid can be similar to that of the fiber sheet. The application of the self-locking anchorage technology is expected to solve the problem of end-interface debonding in TRC-reinforced concrete beams, enhance the material utilization, and improve the strengthening effect. The proposed formula for calculating the bearing capacity after fiber mesh reinforcement can provide a useful reference for related engineering practice.
In order to solve the problem of interface end peeling of textile reinforced concrete (TRC) reinforced concrete beam structures, an end self-locking technique was proposed to anchor the TRC slabs at the bottom of the beams. Owing to the end anchorage provided by this technique, the TRC slab can continue to carry the load even if interfacial debonding occurs. However, compared with the fiber sheet, the fiber mesh has poor synergistic stress performance due to much larger gaps between the fiber bundles, and it is doubtful whether self-locking can be achieved without treatment. In order to improve the utilization of fiber mesh strength, this paper investigates the end-anchor self-locking enhancement effect through the end self-locking anchored fiber mesh tensile test. Measures such as increasing physical friction or adding chemical bonding to the fiber grid are taken to stretch it to failure. The failure modes and load-strain curves of each specimen are analyzed and compared, and a formula for calculating the bearing capacity of the fiber grid after enhancement is proposed. The results show that even if the size of the fiber grid is limited, the strength utilization rate of the fiber grid under end anchoring is increased by 60.66% by reinforcement measures, and the tensile bearing capacity of the three-layer grid can be similar to that of the fiber sheet. The application of the self-locking anchorage technology is expected to solve the problem of end-interface debonding in TRC-reinforced concrete beams, enhance the material utilization, and improve the strengthening effect. The proposed formula for calculating the bearing capacity after fiber mesh reinforcement can provide a useful reference for related engineering practice.
2024,
41(7):
3677-3688.
doi: 10.13801/j.cnki.fhclxb.20231206.001
Abstract:
To investigate the degradation pattern of tensile properties of epoxy resin-based hybrid carbon-basalt fiber reinforcing bars (CF-BF/Epoxy) in seawater sea-sand concrete (SSC) under seawater immersion, the CF-BF/Epoxy in SSC were soaked in seawater at different temperatures (25℃, 40℃, and 55℃) for durations of 60, 90 and 120 days. The tensile performance of the CF-BF/Epoxy in SSC was examined through tensile tests, and the changes in their microstructure were analyzed by SEM and FTIR. The results indicate that ambient temperature significantly affects the tensile properties of CF-BF/Epoxy. After 120 days of immersion at 55℃, the tensile strength decreases by 13.84%, the elastic modulus experiences a slight fluctuation within a 3% range, and pseudo-ductility is observed in the CF-BF/Epoxy. Additionally, blending of basalt fibers and carbon fibers delay the further intrusion of OH− from SSC into CF-BF/Epoxy, while the hydrolysis of the resin in the outer basalt fiber region and the degradation of the resin-fiber interface are identified as the primary causes of the decline in the tensile properties of CF-BF/Epoxy. Lastly, based on the Arrhenius equation, it is predicted that the tensile strength retention rate of CF-BF/Epoxy embedded in SSC will drop to 70% between 584 and 803 days.
To investigate the degradation pattern of tensile properties of epoxy resin-based hybrid carbon-basalt fiber reinforcing bars (CF-BF/Epoxy) in seawater sea-sand concrete (SSC) under seawater immersion, the CF-BF/Epoxy in SSC were soaked in seawater at different temperatures (25℃, 40℃, and 55℃) for durations of 60, 90 and 120 days. The tensile performance of the CF-BF/Epoxy in SSC was examined through tensile tests, and the changes in their microstructure were analyzed by SEM and FTIR. The results indicate that ambient temperature significantly affects the tensile properties of CF-BF/Epoxy. After 120 days of immersion at 55℃, the tensile strength decreases by 13.84%, the elastic modulus experiences a slight fluctuation within a 3% range, and pseudo-ductility is observed in the CF-BF/Epoxy. Additionally, blending of basalt fibers and carbon fibers delay the further intrusion of OH− from SSC into CF-BF/Epoxy, while the hydrolysis of the resin in the outer basalt fiber region and the degradation of the resin-fiber interface are identified as the primary causes of the decline in the tensile properties of CF-BF/Epoxy. Lastly, based on the Arrhenius equation, it is predicted that the tensile strength retention rate of CF-BF/Epoxy embedded in SSC will drop to 70% between 584 and 803 days.
Seismic performance of ECC shell-RC composite pier column and its plastic hinge developing mechanism
2024,
41(7):
3689-3703.
doi: 10.13801/j.cnki.fhclxb.20240009.003
Abstract:
To improve the seismic performance of reinforced concrete (RC) pier column and fully utilize the mechanical properties of engineered cementitious composites (ECC), an innovative ECC shell-RC composite pier column was proposed. The numerical analysis model of the composite pier column was established and verified based on ABAQUS platform and existing experimental results, respectively. On this basis, the influence of common design parameters on the seismic performance of the composite pier column was systematically investigated, including the ECC segment height, ECC shell thickness, longitudinal reinforcement ratio, volume stirrup ratio and axial compression ratio. Finally, the plastic hinge development mechanism of the composite pier column was clarified. The results show that compared with RC pier column, the bearing capacity, displacement ductility and energy dissipating capacity of ECC shell-RC composite pier columns are improved. The peak loads of the composite pier columns increase with the ECC segment height increasing. The seismic performance of the composite pier columns can approach to that of the ECC pure pier column when the height of the ECC shell-RC composite segment is larger than 1.4h (Transverse dimension of the pier column h). The peak load and ductility of the composite pier column increase with the ECC shell thickness and longitudinal reinforcement ratio increasing. However, the seismic performance of the composite pier column will not significantly change when the ECC shell thickness is larger than 1/5h. The increase of the axial compression ratio can increase the initial stiffness and peak load of the specimen, while has a negative impact on its ductility. The decreasing of the volume stirrup ratio around the plastic hinge zone will significantly decrease the ductility of the specimen, but little affect its bearing capacity. The plastic hinge development mechanism of the composite pier column is significantly influenced by the height of the ECC shell-RC composite segment. There is a minimum critical height of the composite segment to make the plastic hinge zone not transfer.
To improve the seismic performance of reinforced concrete (RC) pier column and fully utilize the mechanical properties of engineered cementitious composites (ECC), an innovative ECC shell-RC composite pier column was proposed. The numerical analysis model of the composite pier column was established and verified based on ABAQUS platform and existing experimental results, respectively. On this basis, the influence of common design parameters on the seismic performance of the composite pier column was systematically investigated, including the ECC segment height, ECC shell thickness, longitudinal reinforcement ratio, volume stirrup ratio and axial compression ratio. Finally, the plastic hinge development mechanism of the composite pier column was clarified. The results show that compared with RC pier column, the bearing capacity, displacement ductility and energy dissipating capacity of ECC shell-RC composite pier columns are improved. The peak loads of the composite pier columns increase with the ECC segment height increasing. The seismic performance of the composite pier columns can approach to that of the ECC pure pier column when the height of the ECC shell-RC composite segment is larger than 1.4h (Transverse dimension of the pier column h). The peak load and ductility of the composite pier column increase with the ECC shell thickness and longitudinal reinforcement ratio increasing. However, the seismic performance of the composite pier column will not significantly change when the ECC shell thickness is larger than 1/5h. The increase of the axial compression ratio can increase the initial stiffness and peak load of the specimen, while has a negative impact on its ductility. The decreasing of the volume stirrup ratio around the plastic hinge zone will significantly decrease the ductility of the specimen, but little affect its bearing capacity. The plastic hinge development mechanism of the composite pier column is significantly influenced by the height of the ECC shell-RC composite segment. There is a minimum critical height of the composite segment to make the plastic hinge zone not transfer.
2024,
41(7):
3704-3715.
doi: 10.13801/j.cnki.fhclxb.20231205.001
Abstract:
Granite powder (0%-32%) was used to replace part of cement clinker to prepare machine-made sand concrete. The isothermal calorimetry, mercury intrusion porosimetry as well as gas penetration testing-methods were employed to measure the hydration heat, pore structure, mechanical strength and gas permeability of the concrete. Combined with the gray-correlation analysis method, the relationship between gas permeability properties and pore-structure characteristics was established for concrete at various curing ages (28 days-130 days). The results show that appropriate granite powder added can slow down the hydration heat release rate, refine pore structure, increase compressive strength, and reduce gas permeability. The compressive strength value of the concrete with 8% granite powder is the highest while its gas permeability coefficient reaches the lowest. The gray-correlation analysis shows that the effective porosity and the pore with the size less than 100 nm play the most significant impact on gas permeability.
Granite powder (0%-32%) was used to replace part of cement clinker to prepare machine-made sand concrete. The isothermal calorimetry, mercury intrusion porosimetry as well as gas penetration testing-methods were employed to measure the hydration heat, pore structure, mechanical strength and gas permeability of the concrete. Combined with the gray-correlation analysis method, the relationship between gas permeability properties and pore-structure characteristics was established for concrete at various curing ages (28 days-130 days). The results show that appropriate granite powder added can slow down the hydration heat release rate, refine pore structure, increase compressive strength, and reduce gas permeability. The compressive strength value of the concrete with 8% granite powder is the highest while its gas permeability coefficient reaches the lowest. The gray-correlation analysis shows that the effective porosity and the pore with the size less than 100 nm play the most significant impact on gas permeability.
2024,
41(7):
3717-3726.
doi: 10.13801/j.cnki.fhclxb.20231107.002
Abstract:
Rice husk ash is the primary supplementary cementitious material, with rubber particles injected as artificial flaws. Rice husk ash and crumb rubbers engineered cementitious composites (CR-RHA/ECC) are low carbon, ecologically friendly cementitious composites with good ductility. The effects of rubber content (0, 10%, 20%, 30%) on the ductility and cracking characteristics of CR-RHA/ECC at each curing ages (7 days and 28 days) were explored employing macroscopic mechanical properties and microscopic investigations. The results show that: With the increase of age, there is a great difference in the ductility of CR-RHA/ECC. The replacement of 10% river sand by CR weakens the ductility of CR-RHA/ECC at 7 days by 54% and increases the ductility of CR-RHA/ECC at 28 days by 67%. With the increase of age (28 days), When CR replaces 30% river sand, the ductility of CR-RHA/ECC can reach 6%, and the tensile fracture width of CR-RHA/ECC decreases by 52.79% compared with that of CR-RHA/ECC without CR replacement.
Rice husk ash is the primary supplementary cementitious material, with rubber particles injected as artificial flaws. Rice husk ash and crumb rubbers engineered cementitious composites (CR-RHA/ECC) are low carbon, ecologically friendly cementitious composites with good ductility. The effects of rubber content (0, 10%, 20%, 30%) on the ductility and cracking characteristics of CR-RHA/ECC at each curing ages (7 days and 28 days) were explored employing macroscopic mechanical properties and microscopic investigations. The results show that: With the increase of age, there is a great difference in the ductility of CR-RHA/ECC. The replacement of 10% river sand by CR weakens the ductility of CR-RHA/ECC at 7 days by 54% and increases the ductility of CR-RHA/ECC at 28 days by 67%. With the increase of age (28 days), When CR replaces 30% river sand, the ductility of CR-RHA/ECC can reach 6%, and the tensile fracture width of CR-RHA/ECC decreases by 52.79% compared with that of CR-RHA/ECC without CR replacement.
2024,
41(7):
3727-3737.
doi: 10.13801/j.cnki.fhclxb.20231127.001
Abstract:
In order to study the fitness of discrete element method (DEM) in the simulation of mechanical properties of foam concrete and the influence of non-spherical pores on the uniaxial compression characteristics of foam concrete, X-ray computed tomography (X-CT) test and uniaxial compression-acoustic emission joint test were carried out on foamed concrete with density of 500 kg/m3. Based on the measured pore structure characteristics, a series of three-dimensional mesoscopic DEM models with different non-spherical particle proportions were established and the uniaxial compression process was simulated. The results show that the uniaxial compression damage process of the model is basically consistent with the acoustic emission test results, which has obvious stage characteristics. The non-spherical particle discrete element model can characterize the oscillation of the stress-strain curve in the initial compaction stage, and simulate the shear and interlocking of the matrix in the stress dissipation stage. When establishing the discrete element model of foam concrete, the influence of pore shape should be considered. The compressive strength of the DEM model decreases linearly with the increase of the non-spherical rate of the pores in the model while the correlation coefficient is 0.94.
In order to study the fitness of discrete element method (DEM) in the simulation of mechanical properties of foam concrete and the influence of non-spherical pores on the uniaxial compression characteristics of foam concrete, X-ray computed tomography (X-CT) test and uniaxial compression-acoustic emission joint test were carried out on foamed concrete with density of 500 kg/m3. Based on the measured pore structure characteristics, a series of three-dimensional mesoscopic DEM models with different non-spherical particle proportions were established and the uniaxial compression process was simulated. The results show that the uniaxial compression damage process of the model is basically consistent with the acoustic emission test results, which has obvious stage characteristics. The non-spherical particle discrete element model can characterize the oscillation of the stress-strain curve in the initial compaction stage, and simulate the shear and interlocking of the matrix in the stress dissipation stage. When establishing the discrete element model of foam concrete, the influence of pore shape should be considered. The compressive strength of the DEM model decreases linearly with the increase of the non-spherical rate of the pores in the model while the correlation coefficient is 0.94.
2024,
41(7):
3738-3746.
doi: 10.13801/j.cnki.fhclxb.20231106.003
Abstract:
In order to solve the problems of high flame-retardant addition and deterioration of mechanical properties in the modification of wood-plastic composites (WPCs) by traditional expandable graphite, flame-retardant reinforced wood-plastic composites with a multilayered sandwich structure were prepared by laminated hot pressing process and structure optimization design using poplar wood flour (WF), high-density polyethylene (HDPE), expandable graphite (EG) and nano-silicon dioxide (n-SiO2) as the main raw materials. And the appropriate characterization and equipment such as cone calorimeter, vertical burner, limiting oxygen index (LOI) tester and mechanical testing machine were used to investigate the effects of single layer, double layer and triple layer sandwich structures on the flame retardant and mechanical properties of wood-plastic composites, respectively. The experimental results show that compared with the control wood-plastic composite (WPC-0), the multilayer structure wood-plastic composites exhibite significant reduction of heat release rate, total heat release, smoke production rate and total smoke production, and remarkable improvement of residue yield in the cone test when the contents of EG in the flame-retardant layer and n-SiO2 in the reinforcement layer are 10% and 5%, respectively. Among all the multilayer wood-plastic composites, WPC-E3B with a triple layer sandwich structure improves its LOI from 20.8% to 30.6% and passes the UL-94 test with a V-0 rating. Moreover, it also shows better mechanical properties compared with WPC-0, such as a 61.9% increase in impact strength and 16.2% and 13.4% increases in tensile and flexural strength, respectively.
In order to solve the problems of high flame-retardant addition and deterioration of mechanical properties in the modification of wood-plastic composites (WPCs) by traditional expandable graphite, flame-retardant reinforced wood-plastic composites with a multilayered sandwich structure were prepared by laminated hot pressing process and structure optimization design using poplar wood flour (WF), high-density polyethylene (HDPE), expandable graphite (EG) and nano-silicon dioxide (n-SiO2) as the main raw materials. And the appropriate characterization and equipment such as cone calorimeter, vertical burner, limiting oxygen index (LOI) tester and mechanical testing machine were used to investigate the effects of single layer, double layer and triple layer sandwich structures on the flame retardant and mechanical properties of wood-plastic composites, respectively. The experimental results show that compared with the control wood-plastic composite (WPC-0), the multilayer structure wood-plastic composites exhibite significant reduction of heat release rate, total heat release, smoke production rate and total smoke production, and remarkable improvement of residue yield in the cone test when the contents of EG in the flame-retardant layer and n-SiO2 in the reinforcement layer are 10% and 5%, respectively. Among all the multilayer wood-plastic composites, WPC-E3B with a triple layer sandwich structure improves its LOI from 20.8% to 30.6% and passes the UL-94 test with a V-0 rating. Moreover, it also shows better mechanical properties compared with WPC-0, such as a 61.9% increase in impact strength and 16.2% and 13.4% increases in tensile and flexural strength, respectively.
2024,
41(7):
3747-3756.
doi: 10.13801/j.cnki.fhclxb.20231120.001
Abstract:
Traditional methods of cancer treatment include surgery, radiotherapy, and chemotherapy. The surgical treatment is highly traumatic and easy to recur, while the period of radiotherapy is too long. Although chemotherapy is considered as the first choice to destroy tumor cells, it has obvious toxic and side effects, and the long-term chemotherapy can seriously affect the quality of the patients' life. In this study, CuS was selected as a photothermal agent, and mesoporous silica (mSiO2) was coated on the surface of CuS using the solvothermal and template removal methods. With the aid of the large specific surface area of mSiO2, a highly doxorubicin hydrochloride (DOX) loaded nanodrug system was prepared (CuS@mSiO2-DOX). XRD, UV-vis, SEM, TEM, and DLS results jointly confirm that the CuS@mSiO2-DOX nanosystem with a particle size of approximately 300-400 nm is successfully synthesized, and the loading efficiency of DOX in this system can reach up to 99.76%. The 24 h-drug release rate of CuS@mSiO2-DOX reaches 63.44% under the conditions of pH=5.5 and 45℃, which is nearly 20 times higher than that under the normal physiological environment (pH=7.4 and 35℃), indicating that the CuS@mSiO2-DOX nanosystem possesses obvious pH and temperature responsive release characteristics. In addition, the photothermal performance and in-vitro cytotoxicity of the CuS@mSiO2 nanodrug delivery system was tested, and the results show that CuS@mSiO2 exhibits a good photothermal stability with a photothermal conversion efficiency of 31.67%, and which also reveals low toxicity to normal human liver cells (HL-7702). CuS@mSiO2 nanosystem has good biocompatibility, outstanding photothermal conversion and drug loading properties, and after DOX adsorption, the system exhibits excellent pH and laser responsive drug controlled release performance, which is expected to be widely used in the field of combining the photothermal-chemotherapy to synergistically resist tumor.
Traditional methods of cancer treatment include surgery, radiotherapy, and chemotherapy. The surgical treatment is highly traumatic and easy to recur, while the period of radiotherapy is too long. Although chemotherapy is considered as the first choice to destroy tumor cells, it has obvious toxic and side effects, and the long-term chemotherapy can seriously affect the quality of the patients' life. In this study, CuS was selected as a photothermal agent, and mesoporous silica (mSiO2) was coated on the surface of CuS using the solvothermal and template removal methods. With the aid of the large specific surface area of mSiO2, a highly doxorubicin hydrochloride (DOX) loaded nanodrug system was prepared (CuS@mSiO2-DOX). XRD, UV-vis, SEM, TEM, and DLS results jointly confirm that the CuS@mSiO2-DOX nanosystem with a particle size of approximately 300-400 nm is successfully synthesized, and the loading efficiency of DOX in this system can reach up to 99.76%. The 24 h-drug release rate of CuS@mSiO2-DOX reaches 63.44% under the conditions of pH=5.5 and 45℃, which is nearly 20 times higher than that under the normal physiological environment (pH=7.4 and 35℃), indicating that the CuS@mSiO2-DOX nanosystem possesses obvious pH and temperature responsive release characteristics. In addition, the photothermal performance and in-vitro cytotoxicity of the CuS@mSiO2 nanodrug delivery system was tested, and the results show that CuS@mSiO2 exhibits a good photothermal stability with a photothermal conversion efficiency of 31.67%, and which also reveals low toxicity to normal human liver cells (HL-7702). CuS@mSiO2 nanosystem has good biocompatibility, outstanding photothermal conversion and drug loading properties, and after DOX adsorption, the system exhibits excellent pH and laser responsive drug controlled release performance, which is expected to be widely used in the field of combining the photothermal-chemotherapy to synergistically resist tumor.
2024,
41(7):
3757-3764.
doi: 10.13801/j.cnki.fhclxb.20231123.001
Abstract:
The development of novel drug controlled release composite materials is of great significance in the fields of medicine and agriculture. Using chitosan and sodium alginate (CS-Alg) gel network as carrier, PPy/CS-Alg composite slow-release material was prepared by in-situ oxidation of polypyrrole (PPy). The microstructure, structure composition and photothermal conversion properties were studied by SEM, FTIR, XPS and UV-vis-NIR. Indolebutyric acid (IBA) was used as a model drug molecule to study its sustained release performance. The results show that the porous morphology of PPy/CS-Alg microspheres is conducive to the loading and release of IBA. The PPy oxidized state formed by in-situ oxidation can be slowly reduced in the CS-Alg gel network, and changes from a positive state to an uncharged state. As a result, IBA can be slowly released from the gel network of PPy/CS-Alg microspheres, with the long-term release rate of 56.12%. In addition, the temperature of PPy/CS-Alg microspheres under simulated sunlight can rise from 26℃ to 39℃ based on the photothermal effect of PPy, which is conducive to the formation of temperature gradients inside and outside the microspheres and further enhancing the slow-release of IBA. The controlled release material of auxin IBA based on the slow reduction and photothermal effect of PPy has broad application prospects in the agricultural field.
The development of novel drug controlled release composite materials is of great significance in the fields of medicine and agriculture. Using chitosan and sodium alginate (CS-Alg) gel network as carrier, PPy/CS-Alg composite slow-release material was prepared by in-situ oxidation of polypyrrole (PPy). The microstructure, structure composition and photothermal conversion properties were studied by SEM, FTIR, XPS and UV-vis-NIR. Indolebutyric acid (IBA) was used as a model drug molecule to study its sustained release performance. The results show that the porous morphology of PPy/CS-Alg microspheres is conducive to the loading and release of IBA. The PPy oxidized state formed by in-situ oxidation can be slowly reduced in the CS-Alg gel network, and changes from a positive state to an uncharged state. As a result, IBA can be slowly released from the gel network of PPy/CS-Alg microspheres, with the long-term release rate of 56.12%. In addition, the temperature of PPy/CS-Alg microspheres under simulated sunlight can rise from 26℃ to 39℃ based on the photothermal effect of PPy, which is conducive to the formation of temperature gradients inside and outside the microspheres and further enhancing the slow-release of IBA. The controlled release material of auxin IBA based on the slow reduction and photothermal effect of PPy has broad application prospects in the agricultural field.
2024,
41(7):
3765-3776.
doi: 10.13801/j.cnki.fhclxb.20231107.001
Abstract:
Experimental and numerical studies on the bearing response of single-lap, countersunk composite joints which were designed according to ASTM 5961 under various bolt preload were presented. The specimens were manufactured from carbon fiber/epoxy unitapes with quasi-isotropic lay-ups. To obtain a more accurate hole strain, 2D digital image correlation (DIC) measurement technique was used. Three-dimensional finite element model was constructed using ABAQUS/standard and validated by comparing to the experiment. The validated model was used to provide a detailed stress analysis around the hole boundary considering various bolt preload and friction conditions. The results show that countersunk hole is the region where the severest damage occurs, and bolt preload could significantly improve the 2% hole deformation bearing strength but only slightly increase the ultimate bearing strength. Through stress analysis, increasing either bolt preload or friction between laminates are found to have an active effect on relieving stress concentration, and will make a better bearing performance of single-lap, single-bolt, countersunk composite joints.
Experimental and numerical studies on the bearing response of single-lap, countersunk composite joints which were designed according to ASTM 5961 under various bolt preload were presented. The specimens were manufactured from carbon fiber/epoxy unitapes with quasi-isotropic lay-ups. To obtain a more accurate hole strain, 2D digital image correlation (DIC) measurement technique was used. Three-dimensional finite element model was constructed using ABAQUS/standard and validated by comparing to the experiment. The validated model was used to provide a detailed stress analysis around the hole boundary considering various bolt preload and friction conditions. The results show that countersunk hole is the region where the severest damage occurs, and bolt preload could significantly improve the 2% hole deformation bearing strength but only slightly increase the ultimate bearing strength. Through stress analysis, increasing either bolt preload or friction between laminates are found to have an active effect on relieving stress concentration, and will make a better bearing performance of single-lap, single-bolt, countersunk composite joints.
2024,
41(7):
3777-3789.
doi: 10.13801/j.cnki.fhclxb.20231114.001
Abstract:
The structural parameters of TiB2-based ceramic tools with complex edge shapes were designed based on microwave sintering characteristics. The effect of tool design parameters on turning forces and temperatures when turning QT450 ductile cast iron was investigated using finite element simulation. For TiB2-based ceramic tools with complex cutting edges, the optimum tool front angle was found to be 5°, the optimum back angle was found to be 6° and the optimum tip radius was found to be 0.8 mm. Complex edge-shaped TiB2-based ceramic tools were prepared by microwave sintering technology, and the effects of pressing pressure and holding time on the relative density, mechanical properties and microstructure of complex edge-shaped TiB2-based ceramic tools were investigated. The results show that the pressing pressure has a great influence on the abnormal growth of grains, and a reasonable pressing pressure can inhibit the abnormal growth of grains, improve the tool fracture mode, and then improve the tool performance. A reasonable holding time can make the white phase on the surface of the tool partition uniform and prevent aggregation, which is conducive to improving the fracture toughness of the tool. When the pressing pressure is 200 MPa and the holding time is 4 min, the dimensional shrinkage of each part of the tool is more average, the forming accuracy is higher, the densification is the highest, the microstructure is more uniform, the grain arrangement is more compact, and the overall mechanical properties are optimal.
The structural parameters of TiB2-based ceramic tools with complex edge shapes were designed based on microwave sintering characteristics. The effect of tool design parameters on turning forces and temperatures when turning QT450 ductile cast iron was investigated using finite element simulation. For TiB2-based ceramic tools with complex cutting edges, the optimum tool front angle was found to be 5°, the optimum back angle was found to be 6° and the optimum tip radius was found to be 0.8 mm. Complex edge-shaped TiB2-based ceramic tools were prepared by microwave sintering technology, and the effects of pressing pressure and holding time on the relative density, mechanical properties and microstructure of complex edge-shaped TiB2-based ceramic tools were investigated. The results show that the pressing pressure has a great influence on the abnormal growth of grains, and a reasonable pressing pressure can inhibit the abnormal growth of grains, improve the tool fracture mode, and then improve the tool performance. A reasonable holding time can make the white phase on the surface of the tool partition uniform and prevent aggregation, which is conducive to improving the fracture toughness of the tool. When the pressing pressure is 200 MPa and the holding time is 4 min, the dimensional shrinkage of each part of the tool is more average, the forming accuracy is higher, the densification is the highest, the microstructure is more uniform, the grain arrangement is more compact, and the overall mechanical properties are optimal.
2024,
41(7):
3790-3796.
doi: 10.13801/j.cnki.fhclxb.20240024.002
Abstract:
Absorbing honeycomb, which has the characteristics of lightweight, load-bearing, and microwave absorbing, is widely used in radar absorbing structure design. But it has shortcoming in low-frequency absorption performance. In this paper, a metamaterial with strong electromagnetic wave absorption performance was designed using square open resonant ring (SSRR) units. The metamaterial was applied to modify the electromagnetic performance of an absorbing honeycomb, and realized significant improvement on broadband microwave absorption performance. First, the SSRR unit was designed. The variation of electromagnetic scattering characteristics with the shape parameters of the SSRR unit was studied. The influence of the four main design parameters, including the thickness of the dielectric layer, the width of the square ring, the opening width of the square ring and the length of the square ring, on the absorption performance of the metamaterial was explored through simulation. The change rules of the electromagnetic absorption peak with the shape of the square split ring resonator unit were analyzed. A scheme with strong narrow-band absorbing ability was proposed. Then, a design method for metamaterial absorbing honeycomb was proposed by combining the SSRR metamaterial with the absorbing honeycomb. Research shows that compared with the absorbing honeycomb, the reflection loss of the metamaterial absorbing honeycomb is improved by 4.4 dB in 1-10 GHz on average. The absorption performance of the absorbing honeycomb has been significantly enhanced.
Absorbing honeycomb, which has the characteristics of lightweight, load-bearing, and microwave absorbing, is widely used in radar absorbing structure design. But it has shortcoming in low-frequency absorption performance. In this paper, a metamaterial with strong electromagnetic wave absorption performance was designed using square open resonant ring (SSRR) units. The metamaterial was applied to modify the electromagnetic performance of an absorbing honeycomb, and realized significant improvement on broadband microwave absorption performance. First, the SSRR unit was designed. The variation of electromagnetic scattering characteristics with the shape parameters of the SSRR unit was studied. The influence of the four main design parameters, including the thickness of the dielectric layer, the width of the square ring, the opening width of the square ring and the length of the square ring, on the absorption performance of the metamaterial was explored through simulation. The change rules of the electromagnetic absorption peak with the shape of the square split ring resonator unit were analyzed. A scheme with strong narrow-band absorbing ability was proposed. Then, a design method for metamaterial absorbing honeycomb was proposed by combining the SSRR metamaterial with the absorbing honeycomb. Research shows that compared with the absorbing honeycomb, the reflection loss of the metamaterial absorbing honeycomb is improved by 4.4 dB in 1-10 GHz on average. The absorption performance of the absorbing honeycomb has been significantly enhanced.
2024,
41(7):
3797-3803.
doi: 10.13801/j.cnki.fhclxb.20231020.001
Abstract:
Due to the influence of fiber winding molding process and the variable curvature/thickness of the dome, the stress state of the dome of the composite pressure vessel was relatively complicated. It was of great significance to accurately predict the thickness of the winding layer of the dome, which was of great significance for constructing a high-precision finite element model and guiding engineering applications. In order to solve the above problems, this study developed a layer-by-layer prediction method for the winding layer thickness of composite pressure vessel dome based on the dual formula method and cubic spline function method. The effects of polar hole radius, the thickness of single-layer yarn thickness and number of winding layers on the thickness and winding angle of the dome were studied. The results show that as the polar hole radius increases, the thickness of the single-layer yarn sheet in the dome decreases gradually, the extreme value of the fiber winding layer of the dome gradually decreases, and the variation of winding angle at the equatorial circle decreases with the decrease of the radius of the polar hole and the thickness of single-layer yarn. Furthermore, by comparing the thickness of each layer of the dome, it is found that the thickness of each winding layer from the inner layer to the outer increases first, then decreases, and finally tends to be the same as the radius of parallel circle increases.
Due to the influence of fiber winding molding process and the variable curvature/thickness of the dome, the stress state of the dome of the composite pressure vessel was relatively complicated. It was of great significance to accurately predict the thickness of the winding layer of the dome, which was of great significance for constructing a high-precision finite element model and guiding engineering applications. In order to solve the above problems, this study developed a layer-by-layer prediction method for the winding layer thickness of composite pressure vessel dome based on the dual formula method and cubic spline function method. The effects of polar hole radius, the thickness of single-layer yarn thickness and number of winding layers on the thickness and winding angle of the dome were studied. The results show that as the polar hole radius increases, the thickness of the single-layer yarn sheet in the dome decreases gradually, the extreme value of the fiber winding layer of the dome gradually decreases, and the variation of winding angle at the equatorial circle decreases with the decrease of the radius of the polar hole and the thickness of single-layer yarn. Furthermore, by comparing the thickness of each layer of the dome, it is found that the thickness of each winding layer from the inner layer to the outer increases first, then decreases, and finally tends to be the same as the radius of parallel circle increases.
2024,
41(7):
3803-3812.
doi: 10.13801/j.cnki.fhclxb.20231103.001
Abstract:
It is well known that honeycombs with negative Poisson's ratio have excellent mechanical properties. In this paper, two kinds of multi-input and multi-output artificial neural network models (ANN) were developed and compared to predict the energy absorption characteristics of honeycombs with negative Poisson's ratio under different geometric parameters. The cell angle θ, the ratio of straight wall length to cell height L/H and the thickness t of honeycomb cells are used as the inputs of ANN, and the outputs are the initial peak force, platform force and total energy absorption of honeycombs. The error in the verification set is all within 8%, and the average correlation coefficient R2 of the verification set and the test set is greater than 98.2%, which shows that the neural network can obtain good prediction effect and it has the ability to learn and capture the potential physical mechanism that relates the topology structure and mechanical properties of the honeycombs. Compared with ANN1, ANN2 has more network parameters, more complex network structure and better prediction accuracy and training speed. By quickly predicting the mechanical properties of the honeycomb with given geometric parameters, an optimized honeycomb was obtained. A reversed design network was established to reverse design the honeycomb, and it is found that the network has a good prediction effect on the cell angle θ and wall thickness t of the honeycomb, but the prediction effect of L/H is relatively weak, because the parameter L/H has little effect on the initial peak force, platform force and total energy absorption. In addition, the sensitivity analysis of input parameters was carried out. The results show that the sensitivity trend of geometric parameters of the honeycombs to initial peak force, platform force and total energy absorption is the same, the sensitivity of honeycomb cell thickness t is the highest, and the ratio of straight wall length to cell height L/H is the lowest. The reverse design network has good prediction performance for parameters with high sensitivity, while the prediction performance for parameters with low sensitivity is relatively poor. In a word, ANN provides a fast and accurate method for the study of energy absorption performance of honeycombs, which is expected to accelerate the optimization and design process of honeycomb structures.
It is well known that honeycombs with negative Poisson's ratio have excellent mechanical properties. In this paper, two kinds of multi-input and multi-output artificial neural network models (ANN) were developed and compared to predict the energy absorption characteristics of honeycombs with negative Poisson's ratio under different geometric parameters. The cell angle θ, the ratio of straight wall length to cell height L/H and the thickness t of honeycomb cells are used as the inputs of ANN, and the outputs are the initial peak force, platform force and total energy absorption of honeycombs. The error in the verification set is all within 8%, and the average correlation coefficient R2 of the verification set and the test set is greater than 98.2%, which shows that the neural network can obtain good prediction effect and it has the ability to learn and capture the potential physical mechanism that relates the topology structure and mechanical properties of the honeycombs. Compared with ANN1, ANN2 has more network parameters, more complex network structure and better prediction accuracy and training speed. By quickly predicting the mechanical properties of the honeycomb with given geometric parameters, an optimized honeycomb was obtained. A reversed design network was established to reverse design the honeycomb, and it is found that the network has a good prediction effect on the cell angle θ and wall thickness t of the honeycomb, but the prediction effect of L/H is relatively weak, because the parameter L/H has little effect on the initial peak force, platform force and total energy absorption. In addition, the sensitivity analysis of input parameters was carried out. The results show that the sensitivity trend of geometric parameters of the honeycombs to initial peak force, platform force and total energy absorption is the same, the sensitivity of honeycomb cell thickness t is the highest, and the ratio of straight wall length to cell height L/H is the lowest. The reverse design network has good prediction performance for parameters with high sensitivity, while the prediction performance for parameters with low sensitivity is relatively poor. In a word, ANN provides a fast and accurate method for the study of energy absorption performance of honeycombs, which is expected to accelerate the optimization and design process of honeycomb structures.
2024,
41(7):
3815-3823.
doi: 10.13801/j.cnki.fhclxb.20231113.003
Abstract:
The application scope of the glass fiber reinforced plastic (GFRP)-balsa sandwich structure composed of GFRP facings and a balsa wood core is constantly expanding in the field of infrastructure. However, GFRP-balsa sandwich structures are susceptible to creep deformation due to their viscoelasticity. Under the controlled temperature of (25±1)℃ and relative humidity of 55%±5%, the three-point flexural creep performance of the GFRP-balsa sandwich beams at 20%, 25% and 30% load levels were tested for a period of 3000-8760 h using the self-designed flexural creep loading devices. Various models were used to simulate and predict the creep response of the GFRP-balsa sandwich beams. The results show that the GFRP-balsa sandwich beams exhibit linear viscoelasticity at the test load levels. Flexural creep has an important impact on the mid-span deflection of the GFRP-balsa sandwich beams, and the creep coefficients at 3000 h of all the specimens are not less than 0.35. The Findley model is applicable for fitting the time-dependent total deflection of the GFRP-balsa sandwich beams at a single load level, and the maximum relative error between the fitting value and the test value at 3000 h is only 0.7%. The Bailey-Norton model and the general power law model are applicable for predicting the creep deflection and the time-dependent total deflection of the GFRP-balsa sandwich beams when the load level does not exceed 30%, respectively. At one year, the maximum relative error between the predicted value of the Bailey-Norton model and the test value is 8.3%, and the maximum relative error between the predicted value of the general power law model and the test value is 5.9%.
The application scope of the glass fiber reinforced plastic (GFRP)-balsa sandwich structure composed of GFRP facings and a balsa wood core is constantly expanding in the field of infrastructure. However, GFRP-balsa sandwich structures are susceptible to creep deformation due to their viscoelasticity. Under the controlled temperature of (25±1)℃ and relative humidity of 55%±5%, the three-point flexural creep performance of the GFRP-balsa sandwich beams at 20%, 25% and 30% load levels were tested for a period of 3000-8760 h using the self-designed flexural creep loading devices. Various models were used to simulate and predict the creep response of the GFRP-balsa sandwich beams. The results show that the GFRP-balsa sandwich beams exhibit linear viscoelasticity at the test load levels. Flexural creep has an important impact on the mid-span deflection of the GFRP-balsa sandwich beams, and the creep coefficients at 3000 h of all the specimens are not less than 0.35. The Findley model is applicable for fitting the time-dependent total deflection of the GFRP-balsa sandwich beams at a single load level, and the maximum relative error between the fitting value and the test value at 3000 h is only 0.7%. The Bailey-Norton model and the general power law model are applicable for predicting the creep deflection and the time-dependent total deflection of the GFRP-balsa sandwich beams when the load level does not exceed 30%, respectively. At one year, the maximum relative error between the predicted value of the Bailey-Norton model and the test value is 8.3%, and the maximum relative error between the predicted value of the general power law model and the test value is 5.9%.
2024,
41(7):
3822-3830.
doi: 10.13801/j.cnki.fhclxb.20231124.001
Abstract:
Thermoset resin based prepregs exhibit very high tensile modulus and relatively low bending stiffness, and the accurate characterization of such special properties of prepregs is critical to predict and avoid the wrinkle defect during forming process, and improve the accuracy of finite element simulation of composite forming process. In the present paper, a finite element model that accurately tracks the fiber directions was built considering the nonlinear in-plane shear behavior of unidirectional prepregs, and the high tensile stiffness and significantly lower bending stiffness of the prepreg were decoupled using superimposed membrane-shell elements. Besides, the tensile stiffness, no-linear shear stiffness, and bending stiffness of the domestic prepreg system AC531/CCF800H were characterized experimentally. Finally, the 30° off-axis tensile test and axial compression test were used to prove the validity of the proposed model, respectively.
Thermoset resin based prepregs exhibit very high tensile modulus and relatively low bending stiffness, and the accurate characterization of such special properties of prepregs is critical to predict and avoid the wrinkle defect during forming process, and improve the accuracy of finite element simulation of composite forming process. In the present paper, a finite element model that accurately tracks the fiber directions was built considering the nonlinear in-plane shear behavior of unidirectional prepregs, and the high tensile stiffness and significantly lower bending stiffness of the prepreg were decoupled using superimposed membrane-shell elements. Besides, the tensile stiffness, no-linear shear stiffness, and bending stiffness of the domestic prepreg system AC531/CCF800H were characterized experimentally. Finally, the 30° off-axis tensile test and axial compression test were used to prove the validity of the proposed model, respectively.
2024,
41(7):
3832-3839.
doi: 10.13801/j.cnki.fhclxb.20240004.001
Abstract:
Smoothed finite element method is based on strain-smoothed technology, it avoids using the isoparametric transformations during numerical integration, and has certain advantages in simulating large deformation problems of soft materials. A numerical format for simulating large deformation of hard magnetic soft materials based on strain-smoothed technology has been established, and the necessary stress tensors and constitutive tensors have been provided. The bending characteristics of hard magnetic soft material beams with different aspect ratios under external magnetic field were studied, and the magnetic load displacement curves obtained were compared with experimental results, evolution process of the morphological of hard magnetic soft material structures with different directions of residual magnetic field under the action of an external magnetic field was simulated, and the calculated final deformation morphology was compared with experimental results. The numerical results indicate that the results obtained by using this numerical format are in good agreement with the experimental results. There is significant deformation at the sudden change in the direction of the residual magnetic field inside hard magnetic soft materials. The research results can provide reference for the mechanical analysis and deformation control design of soft robots and intelligent flexible structures composed of hard magnetic soft materials.
Smoothed finite element method is based on strain-smoothed technology, it avoids using the isoparametric transformations during numerical integration, and has certain advantages in simulating large deformation problems of soft materials. A numerical format for simulating large deformation of hard magnetic soft materials based on strain-smoothed technology has been established, and the necessary stress tensors and constitutive tensors have been provided. The bending characteristics of hard magnetic soft material beams with different aspect ratios under external magnetic field were studied, and the magnetic load displacement curves obtained were compared with experimental results, evolution process of the morphological of hard magnetic soft material structures with different directions of residual magnetic field under the action of an external magnetic field was simulated, and the calculated final deformation morphology was compared with experimental results. The numerical results indicate that the results obtained by using this numerical format are in good agreement with the experimental results. There is significant deformation at the sudden change in the direction of the residual magnetic field inside hard magnetic soft materials. The research results can provide reference for the mechanical analysis and deformation control design of soft robots and intelligent flexible structures composed of hard magnetic soft materials.
