Latest Issue
2024, Volume 41, Issue 9
column
2024,
41(9):
4435-4456.
doi: 10.13801/j.cnki.fhclxb.20240423.004
Abstract:
Biomimetic structures can partly overcome the shortcomings of traditional structures and materials, thereby achieving high performance and diversified functions. Additive manufacturing (3D printing) technology can achieve the formation of complex structures, making it possible to prepare biomimetic structures with superior mechanical properties and more diverse functions. With the continuous development of additive manufacturing technology, the combination of additive manufacturing technology and biomimetic structure design is receiving increasing interests. Simultaneously, additive manufactured biomimetic structures have good mechanical properties and functions, that has attracted attentions in the fields such as aerospace, rail transportation, mechanical industry, and biomedical engineering, etc. This article summarizes the research progress on 3D printed biomimetic structures in recent years, majorly focusing on mechanical performance optimization and functionality. The optimized mechanical properties mainly include energy absorption, high strength, and high stiffness, while the functions are related to sensing, driving, medicine and so on. Finally, this article provides an outlook on the advantages, existing research limitations, and future development of additive manufactured biomimetic structures.
Biomimetic structures can partly overcome the shortcomings of traditional structures and materials, thereby achieving high performance and diversified functions. Additive manufacturing (3D printing) technology can achieve the formation of complex structures, making it possible to prepare biomimetic structures with superior mechanical properties and more diverse functions. With the continuous development of additive manufacturing technology, the combination of additive manufacturing technology and biomimetic structure design is receiving increasing interests. Simultaneously, additive manufactured biomimetic structures have good mechanical properties and functions, that has attracted attentions in the fields such as aerospace, rail transportation, mechanical industry, and biomedical engineering, etc. This article summarizes the research progress on 3D printed biomimetic structures in recent years, majorly focusing on mechanical performance optimization and functionality. The optimized mechanical properties mainly include energy absorption, high strength, and high stiffness, while the functions are related to sensing, driving, medicine and so on. Finally, this article provides an outlook on the advantages, existing research limitations, and future development of additive manufactured biomimetic structures.
2024,
41(9):
4457-4477.
doi: 10.13801/j.cnki.fhclxb.20240731.001
Abstract:
Under the premise of continuous improvement of lightweight and structural performance of carbon fiber reinforced polymer matrix composites, enhancing specific functions, especially in the case of no loss, or even enhancement of their interlaminar fracture toughness, can not only compensate for the inherent shortcomings of structural composite materials, such as the electrical insulation of the resin matrix, but also enable them to meet the requirements of specific products, such as high stiffness and certain sound absorption and noise reduction properties. Obviously, for cutting-edge applications such as aerospace, such function-added or structure-function-integrated composites technology is crucial to the future development of aerospace technology. In this paper, the design, preparation, and performance studies of four typical function-integrated structural composites are presented, which are conductivity-toughening integrated laminate based on functionalized interlayer technology (FIT), and based on inter-woven conductive weft fabric (IWCWF); Sound absorption composite based on honeycomb/micro-perforated panels sandwich structure filled with carbonized cotton fibers with hierarchical pores, and based on folded structures prepared from woven fabric/nonwoven mats. The first two materials achieved simultaneous improvement in the electrical conductivity and interlaminar toughness of composite materials by inserting conductive functional interlayers into the resin-rich layers and introducing a conductive weft network throughout the composite. The latter two materials demonstrated excellent sound absorption performance through the technology using honeycomb/micro-perforated panel sandwich filled with carbonized cotton fibers with hierarchical pores, and the folding technology of woven fabric/nonwoven fiber mats composite sheets. This showcases the application of multi-scale, multi-level structural design and fabrication techniques in the functional integration and structural-functional integration of structural composites.
Under the premise of continuous improvement of lightweight and structural performance of carbon fiber reinforced polymer matrix composites, enhancing specific functions, especially in the case of no loss, or even enhancement of their interlaminar fracture toughness, can not only compensate for the inherent shortcomings of structural composite materials, such as the electrical insulation of the resin matrix, but also enable them to meet the requirements of specific products, such as high stiffness and certain sound absorption and noise reduction properties. Obviously, for cutting-edge applications such as aerospace, such function-added or structure-function-integrated composites technology is crucial to the future development of aerospace technology. In this paper, the design, preparation, and performance studies of four typical function-integrated structural composites are presented, which are conductivity-toughening integrated laminate based on functionalized interlayer technology (FIT), and based on inter-woven conductive weft fabric (IWCWF); Sound absorption composite based on honeycomb/micro-perforated panels sandwich structure filled with carbonized cotton fibers with hierarchical pores, and based on folded structures prepared from woven fabric/nonwoven mats. The first two materials achieved simultaneous improvement in the electrical conductivity and interlaminar toughness of composite materials by inserting conductive functional interlayers into the resin-rich layers and introducing a conductive weft network throughout the composite. The latter two materials demonstrated excellent sound absorption performance through the technology using honeycomb/micro-perforated panel sandwich filled with carbonized cotton fibers with hierarchical pores, and the folding technology of woven fabric/nonwoven fiber mats composite sheets. This showcases the application of multi-scale, multi-level structural design and fabrication techniques in the functional integration and structural-functional integration of structural composites.
2024,
41(9):
4478-4501.
doi: 10.13801/j.cnki.fhclxb.20240026.001
Abstract:
Constraint-free design, rapid production, and the absence of mold requirements are just a few of the reasons why continuous fiber-reinforced 3D printing (CFR3DP) has emerged as one of the most innovative advanced composite manufacturing technologies nowadays. This study examines the recent developments in research concerning process defects and the failure behaviors of CFR3DP. In order to systematically categorize the printing process, the notion of "dry/wet/dry-wet-mixed" has been introduced, with an emphasis on the three distinct groups of defects that may be introduced during the additive manufacturing process. Following this, an analysis was conducted to summarize the failure behaviors of CFR3DP while also identifying the primary causes of failure. In conclusion, we propose the prospect of CFR3DP with respect to cost reduction, efficiency, the mitigation of process defects, and improvement of failure mode.
Constraint-free design, rapid production, and the absence of mold requirements are just a few of the reasons why continuous fiber-reinforced 3D printing (CFR3DP) has emerged as one of the most innovative advanced composite manufacturing technologies nowadays. This study examines the recent developments in research concerning process defects and the failure behaviors of CFR3DP. In order to systematically categorize the printing process, the notion of "dry/wet/dry-wet-mixed" has been introduced, with an emphasis on the three distinct groups of defects that may be introduced during the additive manufacturing process. Following this, an analysis was conducted to summarize the failure behaviors of CFR3DP while also identifying the primary causes of failure. In conclusion, we propose the prospect of CFR3DP with respect to cost reduction, efficiency, the mitigation of process defects, and improvement of failure mode.
2024,
41(9):
4502-4517.
doi: 10.13801/j.cnki.fhclxb.20240722.005
Abstract:
Continuous fiber-reinforced thermoplastic composites offer exceptional mechanical and chemical properties, attracting widespread attention in both academia and industry. To meet the automation requirements for high-performance complex structural components, additive manufacturing technologies for continuous fiber-reinforced thermoplastic composites have garnered significant interest. These manufacturing methods include Fused Deposition Modeling and automated fiber placement. The additive manufacturing process involves multi-scale physical phenomena, presenting a complex interplay that is not yet fully understood. The inherent properties of thermoplastic polymers, such as their high melting points and viscosities, further complicate processing, posing substantial challenges in the control of manufacturing processes. Addressing the intricate mechanical challenges within the manufacturing process can be facilitated through the application of multi-scale process mechanics simulations. The integration of these simulations with theoretical and empirical research aids in forging a clear correlation between manufacturing process parameters and the quality of the final product. This provides theoretical support for optimizing process parameters and equipment module design. However, the implementation of multi-scale process simulation requires in-depth comprehension and precise description of physical phenomena. It also involves the design of sophisticated algorithms and the construction of intricate models, thereby increasing the difficulty and challenge of the simulation. This paper reviews recent studies employing various numerical modeling approaches to investigate the processing mechanisms of continuous fiber reinforced thermoplastic composites during the AFP and FDM processes. It also outlines potential promising directions in the field.
Continuous fiber-reinforced thermoplastic composites offer exceptional mechanical and chemical properties, attracting widespread attention in both academia and industry. To meet the automation requirements for high-performance complex structural components, additive manufacturing technologies for continuous fiber-reinforced thermoplastic composites have garnered significant interest. These manufacturing methods include Fused Deposition Modeling and automated fiber placement. The additive manufacturing process involves multi-scale physical phenomena, presenting a complex interplay that is not yet fully understood. The inherent properties of thermoplastic polymers, such as their high melting points and viscosities, further complicate processing, posing substantial challenges in the control of manufacturing processes. Addressing the intricate mechanical challenges within the manufacturing process can be facilitated through the application of multi-scale process mechanics simulations. The integration of these simulations with theoretical and empirical research aids in forging a clear correlation between manufacturing process parameters and the quality of the final product. This provides theoretical support for optimizing process parameters and equipment module design. However, the implementation of multi-scale process simulation requires in-depth comprehension and precise description of physical phenomena. It also involves the design of sophisticated algorithms and the construction of intricate models, thereby increasing the difficulty and challenge of the simulation. This paper reviews recent studies employing various numerical modeling approaches to investigate the processing mechanisms of continuous fiber reinforced thermoplastic composites during the AFP and FDM processes. It also outlines potential promising directions in the field.
2024,
41(9):
4518-4534.
doi: 10.13801/j.cnki.fhclxb.20240418.004
Abstract:
Carbon fiber toughened ceramic matrix composites inherit the excellent mechanical properties of carbon fibers and the high oxidation and corrosion resistance of ceramics, become the most promising candidate thermal protection materials for hypersonic vehicles. The high-temperature oxidation mechanisms and damage mechanical behaviors of carbon fiber toughened ceramic matrix composites in coupled service environments are important topics in the study of design, property characteristic and evaluation of thermal protection material. This provides a detailed discussion and summary of the research and analysis methods employed to characterize the oxidation damage of C/SiC and C/ZrB2-SiC composites in three aspects: High-temperature oxidation mechanisms, coupled failure experiment, and high-temperature oxidation model. The limitations and applicability of various research methods are analyzed and evaluated. In addition, the development trend of investigation of oxidation damage in carbon fiber toughened ceramic matrix composites is provided. It provides guidance for the study of thermal/mechanical response analysis and performance evaluation of carbon fiber toughened ceramic matrix composites in the thermal/mechanical/oxygen environment.
Carbon fiber toughened ceramic matrix composites inherit the excellent mechanical properties of carbon fibers and the high oxidation and corrosion resistance of ceramics, become the most promising candidate thermal protection materials for hypersonic vehicles. The high-temperature oxidation mechanisms and damage mechanical behaviors of carbon fiber toughened ceramic matrix composites in coupled service environments are important topics in the study of design, property characteristic and evaluation of thermal protection material. This provides a detailed discussion and summary of the research and analysis methods employed to characterize the oxidation damage of C/SiC and C/ZrB2-SiC composites in three aspects: High-temperature oxidation mechanisms, coupled failure experiment, and high-temperature oxidation model. The limitations and applicability of various research methods are analyzed and evaluated. In addition, the development trend of investigation of oxidation damage in carbon fiber toughened ceramic matrix composites is provided. It provides guidance for the study of thermal/mechanical response analysis and performance evaluation of carbon fiber toughened ceramic matrix composites in the thermal/mechanical/oxygen environment.
2024,
41(9):
4535-4562.
doi: 10.13801/j.cnki.fhclxb.20240407.003
Abstract:
Continuous fiber reinforced composites have gained wide attention and application in high-end equipment fields such as aerospace, defense, and medical devices, due to their excellent specific stiffness, specific strength, and other properties. The fiber orientation has a significant impact on the mechanical performance of continuous fiber reinforced composites. However, due to the limitations of conventional manufacturing processes, the fiber paths are usually set along regular directions such as 0°, 45°, 90°, etc., which hinders the full utilization of the advantages of continuous fiber reinforced composites. Nowadays, the development of 3D printing technology has facilitated the manufacturing of composites with complex curved fiber paths, and the corresponding optimization methods for fiber orientation and path design have gradually attracted attention from experts and scholars worldwide. In this article, we focus on the optimization methods for fiber orientation and path design of fiber reinforced composites. We introduce the theory of orthogonal anisotropic material direction optimization, review the methods for fiber angle optimization, summarize the existing fiber path planning algorithms, discuss relevant cutting-edge issues, and provide future prospects. This review provides important information for the design optimization and manufacturing of high-performance continuous fiber reinforced composites, which will contribute to the rapid development and wide application of continuous fiber reinforced composites.
Continuous fiber reinforced composites have gained wide attention and application in high-end equipment fields such as aerospace, defense, and medical devices, due to their excellent specific stiffness, specific strength, and other properties. The fiber orientation has a significant impact on the mechanical performance of continuous fiber reinforced composites. However, due to the limitations of conventional manufacturing processes, the fiber paths are usually set along regular directions such as 0°, 45°, 90°, etc., which hinders the full utilization of the advantages of continuous fiber reinforced composites. Nowadays, the development of 3D printing technology has facilitated the manufacturing of composites with complex curved fiber paths, and the corresponding optimization methods for fiber orientation and path design have gradually attracted attention from experts and scholars worldwide. In this article, we focus on the optimization methods for fiber orientation and path design of fiber reinforced composites. We introduce the theory of orthogonal anisotropic material direction optimization, review the methods for fiber angle optimization, summarize the existing fiber path planning algorithms, discuss relevant cutting-edge issues, and provide future prospects. This review provides important information for the design optimization and manufacturing of high-performance continuous fiber reinforced composites, which will contribute to the rapid development and wide application of continuous fiber reinforced composites.
2024,
41(9):
4563-4588.
doi: 10.13801/j.cnki.fhclxb.20240606.002
Abstract:
The increasing utilization of composite materials in aircraft necessitates increasingly stringent safety requirements. The hidden nature and complexity of damage to the composite make predicting failure modes and service life challenging. Consequently, real-time monitoring of structural responses, state information collection, operation evaluation, and damage and remaining life assessment are essential for ensuring the safe and stable operation of aircraft structures. This paper first provides a brief overview of the application of composite structures in typical aircraft structures and the research and application of composite structure health monitoring technology. It then delves into common structural health monitoring techniques, including the research progress of optical fiber sensing monitoring technology, ultrasonic guided wave monitoring technology, acoustic emission monitoring technology, and electromechanical impedance monitoring technology. The application of structural health monitoring technology in various spacecraft structures, such as fuel tank structures, thermal protection structures, engine structures, and wing leading edge structures, is also analyzed and discussed. The research progress of typical structural health monitoring technology evaluation methods is analyzed and summarized. Finally, the development trends and challenges of aerospace composite structure health monitoring technology are discussed and summarized.
The increasing utilization of composite materials in aircraft necessitates increasingly stringent safety requirements. The hidden nature and complexity of damage to the composite make predicting failure modes and service life challenging. Consequently, real-time monitoring of structural responses, state information collection, operation evaluation, and damage and remaining life assessment are essential for ensuring the safe and stable operation of aircraft structures. This paper first provides a brief overview of the application of composite structures in typical aircraft structures and the research and application of composite structure health monitoring technology. It then delves into common structural health monitoring techniques, including the research progress of optical fiber sensing monitoring technology, ultrasonic guided wave monitoring technology, acoustic emission monitoring technology, and electromechanical impedance monitoring technology. The application of structural health monitoring technology in various spacecraft structures, such as fuel tank structures, thermal protection structures, engine structures, and wing leading edge structures, is also analyzed and discussed. The research progress of typical structural health monitoring technology evaluation methods is analyzed and summarized. Finally, the development trends and challenges of aerospace composite structure health monitoring technology are discussed and summarized.
2024,
41(9):
4589-4605.
doi: 10.13801/j.cnki.fhclxb.20240826.002
Abstract:
The vigorous development of China's space exploration industry has posed numerous challenges to the reliability of aerospace equipment. In environments with drastic temperature changes, precise control of thermal deformation in materials and structures such as large-scale space structures, precision detection equipment, and microelectronic packaging has become a bottleneck issue that urgently needs to be broken through. Therefore, it is of great significance to develop mechanical metamaterials with tailorable thermal expansion coefficients. This article provides an overview of the current status and progress of research on the design, preparation, and characterization of tailorable thermal expansion mechanical metamaterials. It systematically sorts out the design methods of tailorable thermal expansion mechanical metamaterials, summarizes the collaborative control strategies of thermal expansion, stiffness, Poisson's ratio, and other mechanical parameters, explores the topological optimization methods of tailorable thermal expansion mechanical metamaterials, and introduces the preparation techniques and performance evaluation methods of thermally tailorable mechanical metamaterials. This article also looks into the development trends of tailorable thermal expansion mechanical metamaterials, providing guidance and reference for their in-depth application in aerospace equipment.
The vigorous development of China's space exploration industry has posed numerous challenges to the reliability of aerospace equipment. In environments with drastic temperature changes, precise control of thermal deformation in materials and structures such as large-scale space structures, precision detection equipment, and microelectronic packaging has become a bottleneck issue that urgently needs to be broken through. Therefore, it is of great significance to develop mechanical metamaterials with tailorable thermal expansion coefficients. This article provides an overview of the current status and progress of research on the design, preparation, and characterization of tailorable thermal expansion mechanical metamaterials. It systematically sorts out the design methods of tailorable thermal expansion mechanical metamaterials, summarizes the collaborative control strategies of thermal expansion, stiffness, Poisson's ratio, and other mechanical parameters, explores the topological optimization methods of tailorable thermal expansion mechanical metamaterials, and introduces the preparation techniques and performance evaluation methods of thermally tailorable mechanical metamaterials. This article also looks into the development trends of tailorable thermal expansion mechanical metamaterials, providing guidance and reference for their in-depth application in aerospace equipment.
2024,
41(9):
4606-4627.
doi: 10.13801/j.cnki.fhclxb.20240304.002
Abstract:
This article reviews the energy absorption mechanism and damage modes of fiber reinforced resin matrix composites in the field of impact resistance. Firstly, the applications of fiber reinforced composites in the fields of ballistic protection and aerospace are introduced. In addition, the advantages and disadvantages of high-performance fibers such as ultra-high molecular weight polyethylene fiber (UHMWPE), aramid fibers and carbon fibers are compared. Secondly, based on ballistic experiments and theoretical simulations of various fiber reinforced resin matrix composites, the energy absorption mechanism and damage mode of bulletproof composites are analyzed. It is found that tensile deformation is the main energy absorption mode of composites, and delamination is its main damage mode. Finally, the classification and characteristics of fabric structures and their influence on the ballistic performance of composites are summarized and the development prospect of fiber reinforced resin matrix composites is prospected.
This article reviews the energy absorption mechanism and damage modes of fiber reinforced resin matrix composites in the field of impact resistance. Firstly, the applications of fiber reinforced composites in the fields of ballistic protection and aerospace are introduced. In addition, the advantages and disadvantages of high-performance fibers such as ultra-high molecular weight polyethylene fiber (UHMWPE), aramid fibers and carbon fibers are compared. Secondly, based on ballistic experiments and theoretical simulations of various fiber reinforced resin matrix composites, the energy absorption mechanism and damage mode of bulletproof composites are analyzed. It is found that tensile deformation is the main energy absorption mode of composites, and delamination is its main damage mode. Finally, the classification and characteristics of fabric structures and their influence on the ballistic performance of composites are summarized and the development prospect of fiber reinforced resin matrix composites is prospected.
2024,
41(9):
4628-4653.
doi: 10.13801/j.cnki.fhclxb.20240923.001
Abstract:
Fiber reinforced SiC ceramic matrix composites (FRCMC) have emerged as preferred materials in aerospace, nuclear energy, and other cutting-edge scientific and technological fields owing to their exceptional specific strength and modulus, as well as superior resistance to high temperatures and chemicals. Although FRCMC are prepared by molding techniques, some machining processes, such as grinding, are necessary to enhance dimensional accuracy and surface integrity, and are indispensable in the high-performance fabrication of FRCMC structural components. However, the innate material properties of high hardness and brittleness, coupled with structural characteristics such as anisotropy and non-homogeneity, pose challenges for efficient and low-damage grinding. The grinding force, serving as a crucial indicator for feedback and control in the production process, is influenced by synergistic effect of multiple parameters of the grinding process, such as wheel and workpiece geometry and kinematics. Therefore, elucidating the mechanical behavior of abrasive grains and work-pieces, and modeling the grinding force, are imperative for comprehending the processing mechanism and guiding efficient production practices. Based on this, the paper firstly analyzed the influence of material properties and grinding parameters on the interaction mechanism between abrasive grains and FRCMC during the grinding process. Secondly, the current research status of FRCMC grinding force prediction modeling was systematically reviewed. The modeling process of grinding force was analytically deduced from the grinding force of a single grain, the geometry of the grain, the geometric properties of the random distribution of fibers, and the criteria for determining the stage of material removal. Furthermore, it discussed the unique aspects of material removal mechanisms and grinding force modeling for ultrasonic vibration-assisted grinding of FRCMC from the viewpoints of the chips shaping mechanism, the thickness of the undeformed chips, and the kinematics of the abrasive grains. Finally, the paper discussed current research gap, and identifies potential research hotspots. The objective is to formulate practical guidelines for low-damage grinding of FRCMC and establish a robust theoretical framework to advance grinding force modeling not only for FRCMC but also for other materials.
Fiber reinforced SiC ceramic matrix composites (FRCMC) have emerged as preferred materials in aerospace, nuclear energy, and other cutting-edge scientific and technological fields owing to their exceptional specific strength and modulus, as well as superior resistance to high temperatures and chemicals. Although FRCMC are prepared by molding techniques, some machining processes, such as grinding, are necessary to enhance dimensional accuracy and surface integrity, and are indispensable in the high-performance fabrication of FRCMC structural components. However, the innate material properties of high hardness and brittleness, coupled with structural characteristics such as anisotropy and non-homogeneity, pose challenges for efficient and low-damage grinding. The grinding force, serving as a crucial indicator for feedback and control in the production process, is influenced by synergistic effect of multiple parameters of the grinding process, such as wheel and workpiece geometry and kinematics. Therefore, elucidating the mechanical behavior of abrasive grains and work-pieces, and modeling the grinding force, are imperative for comprehending the processing mechanism and guiding efficient production practices. Based on this, the paper firstly analyzed the influence of material properties and grinding parameters on the interaction mechanism between abrasive grains and FRCMC during the grinding process. Secondly, the current research status of FRCMC grinding force prediction modeling was systematically reviewed. The modeling process of grinding force was analytically deduced from the grinding force of a single grain, the geometry of the grain, the geometric properties of the random distribution of fibers, and the criteria for determining the stage of material removal. Furthermore, it discussed the unique aspects of material removal mechanisms and grinding force modeling for ultrasonic vibration-assisted grinding of FRCMC from the viewpoints of the chips shaping mechanism, the thickness of the undeformed chips, and the kinematics of the abrasive grains. Finally, the paper discussed current research gap, and identifies potential research hotspots. The objective is to formulate practical guidelines for low-damage grinding of FRCMC and establish a robust theoretical framework to advance grinding force modeling not only for FRCMC but also for other materials.
2024,
41(9):
4654-4672.
doi: 10.13801/j.cnki.fhclxb.20231127.003
Abstract:
Currently, continuous fiber-reinforced polymer matrix composite find extensive applications in aerospace and various other industries. These materials undergo intricate multiaxial stress states during usage, with a predominant presence of fatigue loads. Consequently, delving into the multiaxial fatigue study of composite materials becomes imperative. Research on the multiaxial fatigue of composite materials is presently categorized into three primary domains: Exploration of multiaxial fatigue behavior across different specimens, identification of factors influencing such behavior, and the development of multiaxial fatigue life prediction methods. The investigation into multiaxial fatigue testing of composite materials encompasses tube-shaped, cross-shaped, and plate-shaped specimens. Among these, cross-shaped and tube-shaped specimen tests are the most prevalent. The impact of factors such as stacking sequence, multiaxial degree, and load loading methods on the multiaxial fatigue strength of composite materials under varying multiaxial fatigue loading conditions are discussed in this article. Concerning the prediction of biaxial fatigue life in composite materials, available methods predominantly consist of phenomenological models and non-classical models. While akin to uniaxial fatigue life prediction methods, these models overlook damage evolution under biaxial fatigue loads and the damage mechanisms controlling final failure. A comprehensive overview of the progress in researching multiaxial fatigue of fiber-reinforced composite materials is furnished, and an in-depth introduction is provided for the three dimensions of multiaxial fatigue. Through the synthesis and analysis of existing research findings, prospective directions for future research on multiaxial fatigue in composite materials are discussed.
Currently, continuous fiber-reinforced polymer matrix composite find extensive applications in aerospace and various other industries. These materials undergo intricate multiaxial stress states during usage, with a predominant presence of fatigue loads. Consequently, delving into the multiaxial fatigue study of composite materials becomes imperative. Research on the multiaxial fatigue of composite materials is presently categorized into three primary domains: Exploration of multiaxial fatigue behavior across different specimens, identification of factors influencing such behavior, and the development of multiaxial fatigue life prediction methods. The investigation into multiaxial fatigue testing of composite materials encompasses tube-shaped, cross-shaped, and plate-shaped specimens. Among these, cross-shaped and tube-shaped specimen tests are the most prevalent. The impact of factors such as stacking sequence, multiaxial degree, and load loading methods on the multiaxial fatigue strength of composite materials under varying multiaxial fatigue loading conditions are discussed in this article. Concerning the prediction of biaxial fatigue life in composite materials, available methods predominantly consist of phenomenological models and non-classical models. While akin to uniaxial fatigue life prediction methods, these models overlook damage evolution under biaxial fatigue loads and the damage mechanisms controlling final failure. A comprehensive overview of the progress in researching multiaxial fatigue of fiber-reinforced composite materials is furnished, and an in-depth introduction is provided for the three dimensions of multiaxial fatigue. Through the synthesis and analysis of existing research findings, prospective directions for future research on multiaxial fatigue in composite materials are discussed.
2024,
41(9):
4673-4700.
doi: 10.13801/j.cnki.fhclxb.20240611.003
Abstract:
The large-scale application of composite materials is the main means of weight reduction for aircraft stiffened panel structures, but due to overly conservative design criteria, the weight reduction effect of the structure is not ideal. Thin-walled stiffened panel structures usually have a long post-buckling bearing history, but due to the lack of effective analysis methods for post-buckling design and evaluation, currently, aircraft composite stiffened panels almost do not allow the skin to buckle below the limited load, which cannot fully utilize the weight reduction characteristics of composite materials. This article reviewed the development process of stability design for composite stiffened panels and elaborates on the necessity of conducting post-buckling design analysis, and provided a detailed review of the research progress on the buckling and post-buckling performance analysis and design methods of stiffened panel structures, focusing on two aspects: engineering analysis technology and numerical analysis technology; Explored the main factors affecting the buckling and post-buckling performance of composite stiffened panels, and discussed the effects of buckling fatigue, damage/defects, and humid thermal environment on structural performance; Finally, the overall status of post-buckling design and analysis technology for composite stiffened panels was summarized, and future technological development trends were discussed.
The large-scale application of composite materials is the main means of weight reduction for aircraft stiffened panel structures, but due to overly conservative design criteria, the weight reduction effect of the structure is not ideal. Thin-walled stiffened panel structures usually have a long post-buckling bearing history, but due to the lack of effective analysis methods for post-buckling design and evaluation, currently, aircraft composite stiffened panels almost do not allow the skin to buckle below the limited load, which cannot fully utilize the weight reduction characteristics of composite materials. This article reviewed the development process of stability design for composite stiffened panels and elaborates on the necessity of conducting post-buckling design analysis, and provided a detailed review of the research progress on the buckling and post-buckling performance analysis and design methods of stiffened panel structures, focusing on two aspects: engineering analysis technology and numerical analysis technology; Explored the main factors affecting the buckling and post-buckling performance of composite stiffened panels, and discussed the effects of buckling fatigue, damage/defects, and humid thermal environment on structural performance; Finally, the overall status of post-buckling design and analysis technology for composite stiffened panels was summarized, and future technological development trends were discussed.
2024,
41(9):
4701-4719.
doi: 10.13801/j.cnki.fhclxb.20240416.003
Abstract:
Three-dimensional composite materials have great application value in aerospace and other fields due to their excellent anti-delamination capability. In recent years, they have attracted extensive attention from domestical and abroad researchers. However, for the traditional three-dimensional (3D) composite materials, they require long manufacturing cycles, complex manufacturing technique and are hard to be formed. This has become one of the key challenges restricting the broad application of the 3D composite components. Tufting is a simple single-sided stitching technique characterized by non-interlocked structure. This feature probably allows three-dimensional preforms made by tufting to be shaped on curved surfaces without defects. Firstly, this paper outlines the development of tufting technology and the structural characteristics of tufted composite materials. Secondly, it reviews existing research on forming tufted preform with curved mold, focusing on three aspects: Formability analysis, definition of forming defects, and digital characterization methods. It points out the progress made in current research and the shortcomings that still exist. Furthermore, it summarizes the numerical simulation methods for the forming process of tufted preform, highlighting the specific forming model of the tufted preform. Finally, it explores the future direction of tufting technology in the field of forming for composite materials.
Three-dimensional composite materials have great application value in aerospace and other fields due to their excellent anti-delamination capability. In recent years, they have attracted extensive attention from domestical and abroad researchers. However, for the traditional three-dimensional (3D) composite materials, they require long manufacturing cycles, complex manufacturing technique and are hard to be formed. This has become one of the key challenges restricting the broad application of the 3D composite components. Tufting is a simple single-sided stitching technique characterized by non-interlocked structure. This feature probably allows three-dimensional preforms made by tufting to be shaped on curved surfaces without defects. Firstly, this paper outlines the development of tufting technology and the structural characteristics of tufted composite materials. Secondly, it reviews existing research on forming tufted preform with curved mold, focusing on three aspects: Formability analysis, definition of forming defects, and digital characterization methods. It points out the progress made in current research and the shortcomings that still exist. Furthermore, it summarizes the numerical simulation methods for the forming process of tufted preform, highlighting the specific forming model of the tufted preform. Finally, it explores the future direction of tufting technology in the field of forming for composite materials.
2024,
41(9):
4720-4739.
doi: 10.13801/j.cnki.fhclxb.20240719.002
Abstract:
Jet vane has been widely studied and applied because of its fast response and large attitude angle rotation. However, the ablation and denudation of jet vane surface seriously restricts its development. In this paper, the typical research progress of jet vane is reviewed, including the flow performance of jet vane, the surface thermal chemical ablation and mechanical erosion of metal and composite materials jet vane structure. In addition, in view of the light composite jet vane is an inevitable trend in the future development, the paper also discusses the ablative and denudation of other relevant composite structures for reference. Based on this, the paper finally puts forward the future development focus of composite jet vane, in order to provide reference for the research, application and development of composite jet vane in China.
Jet vane has been widely studied and applied because of its fast response and large attitude angle rotation. However, the ablation and denudation of jet vane surface seriously restricts its development. In this paper, the typical research progress of jet vane is reviewed, including the flow performance of jet vane, the surface thermal chemical ablation and mechanical erosion of metal and composite materials jet vane structure. In addition, in view of the light composite jet vane is an inevitable trend in the future development, the paper also discusses the ablative and denudation of other relevant composite structures for reference. Based on this, the paper finally puts forward the future development focus of composite jet vane, in order to provide reference for the research, application and development of composite jet vane in China.
2024,
41(9):
4740-4751.
doi: 10.13801/j.cnki.fhclxb.20240205.002
Abstract:
Featured by simple structure, fast response, high sensitivity, and low cost, etc., flexible capacitive pressure sensor has been widely used in the fields of health care, robotics, wearable devices and so on. However, the trade-off between the effective upper and lower detection limits greatly restricts the applications of the flexible capacitive pressure sensor. In this work, a flexible and porous carbon nanotube particles (CNTs)/carbonyl iron particles (CIPs)-silicone composite was produced by using sugar particles (SPs) as the pore-forming agents, CIPs as the magneto-responsive fillers, CNTs as the conductive fillers and silicone rubber as the flexible matrix. After serving as the dielectric layer, the porous CNT-CIP/silicone composite endows the capacitive pressure sensor produced a wide effective detection range of 0.07-180 kPa (at the frequency range of 0-5 Hz), much wider than most capacitive pressure sensors reported. In virtue of the wide detection range, long-term stability and fast response, the sensor produced is capable of monitoring human breath, arm movement, talking, and robotic movement, thus showing great promise in health monitoring, wearable electronic devices, and intelligent robotics, etc.
Featured by simple structure, fast response, high sensitivity, and low cost, etc., flexible capacitive pressure sensor has been widely used in the fields of health care, robotics, wearable devices and so on. However, the trade-off between the effective upper and lower detection limits greatly restricts the applications of the flexible capacitive pressure sensor. In this work, a flexible and porous carbon nanotube particles (CNTs)/carbonyl iron particles (CIPs)-silicone composite was produced by using sugar particles (SPs) as the pore-forming agents, CIPs as the magneto-responsive fillers, CNTs as the conductive fillers and silicone rubber as the flexible matrix. After serving as the dielectric layer, the porous CNT-CIP/silicone composite endows the capacitive pressure sensor produced a wide effective detection range of 0.07-180 kPa (at the frequency range of 0-5 Hz), much wider than most capacitive pressure sensors reported. In virtue of the wide detection range, long-term stability and fast response, the sensor produced is capable of monitoring human breath, arm movement, talking, and robotic movement, thus showing great promise in health monitoring, wearable electronic devices, and intelligent robotics, etc.
2024,
41(9):
4752-4764.
doi: 10.13801/j.cnki.fhclxb.20231030.002
Abstract:
Stretching process is one of the critical procedures that affect the honeycomb cell structure of Aramid honeycomb. In this study, the viscoelastic constitutive relationship of node bond adhesive was determined by a fitting method based on nanoindentation, and a finite element model of honeycomb biaxial stretching process was established. The validity of the model was verified by the honeycomb stretching-holding experiment. The study found that the stress relaxation behavior of the adhesive caused an increase in the radius of the inscribed circles at both ends of the honeycomb and a decrease in the middle. Meanwhile, during the holding process, the node bond adhesive fillet radius decreased, leading to a decrease in the internal angle of the honeycomb cell. Finally, the influence of gluing process parameters on the size of honeycomb cell after stretching was explored based on the finite element model. The study showed that the increase in gluing width and thickness would lead to a decrease in the diameter of the inscribed circle of the honeycomb cell, and the honeycomb cell's internal angle was only affected by the gluing width, which increased with the gluing width.
Stretching process is one of the critical procedures that affect the honeycomb cell structure of Aramid honeycomb. In this study, the viscoelastic constitutive relationship of node bond adhesive was determined by a fitting method based on nanoindentation, and a finite element model of honeycomb biaxial stretching process was established. The validity of the model was verified by the honeycomb stretching-holding experiment. The study found that the stress relaxation behavior of the adhesive caused an increase in the radius of the inscribed circles at both ends of the honeycomb and a decrease in the middle. Meanwhile, during the holding process, the node bond adhesive fillet radius decreased, leading to a decrease in the internal angle of the honeycomb cell. Finally, the influence of gluing process parameters on the size of honeycomb cell after stretching was explored based on the finite element model. The study showed that the increase in gluing width and thickness would lead to a decrease in the diameter of the inscribed circle of the honeycomb cell, and the honeycomb cell's internal angle was only affected by the gluing width, which increased with the gluing width.
2024,
41(9):
4765-4777.
doi: 10.13801/j.cnki.fhclxb.20240423.003
Abstract:
As a particle-reinforced polymer composite with high inclusion ratio, the macro-mechanical properties of solid propellants depend on their meso-structures. Especially, under external loads, the stress concentration usually happens besides the regions of the initial imperfections and the particle agglomerations, leading to the interfacial debonding between the particles and the polymeric binders, consequently deteriorating macroscopic mechanical properties. How to build a relationship between the microscopic damage states and the macroscopic mechanical performances is the key issue for both the rational usage of the microscopic experimental results of solid propellants and the accurate prediction of structural disasters in solid rocket motors. For this purpose, this article develops an artificial neural network (ANN) based on the framework of continuum mechanics, with the scalar invariant of the deformation gradient tensor as the input and the scalar free energy as the output. Existing free energy functions and damage growth functions are selected as the activation functions of the ANN, and therefore the ANN can naturally satisfy the requirements of the continuum mechanics, including the deformation continuity, the coordinate invariance, and the thermodynamic consistency. These merits can guarantee the rapid convergence of the ANN with sparse training data, and additionally can obtain a bottom-up mapping of the microscopic damage states towards the macroscopic mechanical performances. Finally, using the dataset obtained from finite element analysis, the predictive ability of the ANN on the mechanical properties of solid propellants with different pre-damage states under uniaxial tension, biaxial tension, and pure shear are validated.
As a particle-reinforced polymer composite with high inclusion ratio, the macro-mechanical properties of solid propellants depend on their meso-structures. Especially, under external loads, the stress concentration usually happens besides the regions of the initial imperfections and the particle agglomerations, leading to the interfacial debonding between the particles and the polymeric binders, consequently deteriorating macroscopic mechanical properties. How to build a relationship between the microscopic damage states and the macroscopic mechanical performances is the key issue for both the rational usage of the microscopic experimental results of solid propellants and the accurate prediction of structural disasters in solid rocket motors. For this purpose, this article develops an artificial neural network (ANN) based on the framework of continuum mechanics, with the scalar invariant of the deformation gradient tensor as the input and the scalar free energy as the output. Existing free energy functions and damage growth functions are selected as the activation functions of the ANN, and therefore the ANN can naturally satisfy the requirements of the continuum mechanics, including the deformation continuity, the coordinate invariance, and the thermodynamic consistency. These merits can guarantee the rapid convergence of the ANN with sparse training data, and additionally can obtain a bottom-up mapping of the microscopic damage states towards the macroscopic mechanical performances. Finally, using the dataset obtained from finite element analysis, the predictive ability of the ANN on the mechanical properties of solid propellants with different pre-damage states under uniaxial tension, biaxial tension, and pure shear are validated.
2024,
41(9):
4778-4790.
doi: 10.13801/j.cnki.fhclxb.20240722.003
Abstract:
Alternating high and low temperatures represent a typical operational environment for fastening structures (e.g., bolted structures) in the aerospace field, which have a pronounced/significant influence on the mechanical performance of bolted structures. In order to explore the impact of temperature variations on the pull-through mechanical performance of different bolts, an out-of-plane pull-through experiment was conducted on carbon-fiber-reinforced bismaleimide resin composites. Additionally, a specialized pull-through experiment fixture was developed for high/low temperature conditions. Using acoustic emission (AE) techniques, optical microscopy, and scanning electron microscopy (SEM), a multidimensional characterization of pull-through failure mechanisms was conducted, revealing the influence of temperature environments and bolts on the pull-through experiment failure mechanisms of composite materials. The findings reveal a correlation between temperature variations and the pull-through strength of differing bolts in composite materials. Specifically, as temperatures rise, the pull-through strength of protruding head fasteners demonstrates a gradual decline. However, the pull-through strength of countersink fasteners exhibits an initial increase followed by a subsequent decrease. The temperature exerts an influence on the damage patterns during the pull-through process of fastening structures. Observations in elevated temperature environments reveal a river pattern of matrix failure, confirming the existence of matrix plastic deformation in the process of interlaminar crack propagation at high temperatures. This provides a plausible explanation for the observed phenomenon of a decrease in pull-through strength of countersink structures with increasing temperature.
Alternating high and low temperatures represent a typical operational environment for fastening structures (e.g., bolted structures) in the aerospace field, which have a pronounced/significant influence on the mechanical performance of bolted structures. In order to explore the impact of temperature variations on the pull-through mechanical performance of different bolts, an out-of-plane pull-through experiment was conducted on carbon-fiber-reinforced bismaleimide resin composites. Additionally, a specialized pull-through experiment fixture was developed for high/low temperature conditions. Using acoustic emission (AE) techniques, optical microscopy, and scanning electron microscopy (SEM), a multidimensional characterization of pull-through failure mechanisms was conducted, revealing the influence of temperature environments and bolts on the pull-through experiment failure mechanisms of composite materials. The findings reveal a correlation between temperature variations and the pull-through strength of differing bolts in composite materials. Specifically, as temperatures rise, the pull-through strength of protruding head fasteners demonstrates a gradual decline. However, the pull-through strength of countersink fasteners exhibits an initial increase followed by a subsequent decrease. The temperature exerts an influence on the damage patterns during the pull-through process of fastening structures. Observations in elevated temperature environments reveal a river pattern of matrix failure, confirming the existence of matrix plastic deformation in the process of interlaminar crack propagation at high temperatures. This provides a plausible explanation for the observed phenomenon of a decrease in pull-through strength of countersink structures with increasing temperature.
2024,
41(9):
4791-4801.
doi: 10.13801/j.cnki.fhclxb.20231019.003
Abstract:
In response to the difficulty in balancing load-bearing and electromagnetic (EM) wave absorbing performance in the design of existing aircraft composite skin, the unique mechanical and electrical characteristics of carbon fiber prepreg were utilized to enhance the mechanical and electrical properties of glass fiber laminated structure (GFLS). Gradient carbon fiber arrays were designed with excellent absorbing performance based on the impedance gradient principle, endowing the structure with EM wave absorbing performance; Carbon fiber reinforced polymer (CFRP) back sheet with excellent load-bearing performance was utilized to achieve enhanced design of mechanical properties. By enhancement design of both magnetic and mechanical properties of GFLS, the EM wave absorbing and load-bearing integrated laminated structure (ILS) was finally constructed. EM simulation and experiment show that the ILS realizes a broadband (5-18 GHz), multiangle (0°-70°), and efficient (average absorptivity >94%) absorption effects for EM wave under thin thickness (<5 mm). Through study of absorption mechanisms, it is discovered that the resonant frequency of a structure is inversely proportional to the width of carbon fibers. The layer-by-layer gradual change of the width of the carbon fibers in the ILS is designed to produce multiple adjacent strong absorption frequency points in a wide range of frequency band, which achieves a broadband and strong EM wave absorption. The mechanical experiment results show that the specific bending strength and specific stiffness of the ILS have increased by 86.8% and 76.3% respectively, compared to the GFLS of the same size. Through the introduction of carbon fiber prepreg in glass fiber prepreg layup and structural design in this paper, the EM wave absorbing and load-bearing performance of the GFLS have significantly been enhanced, providing a novel solution for the EM wave absorbing and load-bearing integrated design of aircraft composite skin.
In response to the difficulty in balancing load-bearing and electromagnetic (EM) wave absorbing performance in the design of existing aircraft composite skin, the unique mechanical and electrical characteristics of carbon fiber prepreg were utilized to enhance the mechanical and electrical properties of glass fiber laminated structure (GFLS). Gradient carbon fiber arrays were designed with excellent absorbing performance based on the impedance gradient principle, endowing the structure with EM wave absorbing performance; Carbon fiber reinforced polymer (CFRP) back sheet with excellent load-bearing performance was utilized to achieve enhanced design of mechanical properties. By enhancement design of both magnetic and mechanical properties of GFLS, the EM wave absorbing and load-bearing integrated laminated structure (ILS) was finally constructed. EM simulation and experiment show that the ILS realizes a broadband (5-18 GHz), multiangle (0°-70°), and efficient (average absorptivity >94%) absorption effects for EM wave under thin thickness (<5 mm). Through study of absorption mechanisms, it is discovered that the resonant frequency of a structure is inversely proportional to the width of carbon fibers. The layer-by-layer gradual change of the width of the carbon fibers in the ILS is designed to produce multiple adjacent strong absorption frequency points in a wide range of frequency band, which achieves a broadband and strong EM wave absorption. The mechanical experiment results show that the specific bending strength and specific stiffness of the ILS have increased by 86.8% and 76.3% respectively, compared to the GFLS of the same size. Through the introduction of carbon fiber prepreg in glass fiber prepreg layup and structural design in this paper, the EM wave absorbing and load-bearing performance of the GFLS have significantly been enhanced, providing a novel solution for the EM wave absorbing and load-bearing integrated design of aircraft composite skin.
2024,
41(9):
4802-4816.
doi: 10.13801/j.cnki.fhclxb.20240418.002
Abstract:
Based on the ablation and heat protection mechanism of ultra-lightweight quartz/phenolic composite, a multi-physics field model for the ablation of composite containing silica phase transition was established. The surface and backside temperature, pyrolysis degree, different layer thicknesses and pore pressure distribution of ultra-lightweight quartz/phenolic composite were predicted. The numerical simulation obtained the variation law of the thickness of the liquid layer of surface silica through calculation, and the temperature results predicted by the model are consistent with the measurement results in the ablation experiment. According to the heat flow analysis results of various heat transfer modes, it can be seen that the most important factors affecting the prevention/insulation mechanism are thermal radiation, thermal blockage and silica gasification. Aiming at the typical application conditions of ultra-lightweight quartz/phenolic composite, the heat flux densities between 0.5 MW/m2 and 2.5 MW/m2 were used as environmental input parameters to study the ablation behavior of ultra-lightweight quartz/phenolic composite. The results show that the surface ablation retreat of ultra-light quartz/phenolic composite increases with the increase of heat flux density; When the heat flux density is less than 1.5 MW/m2, the thickness of the surface liquid layer increases with the increase of heat flux density. When the heat flux density is greater than 1.5 MW/m2, the thickness of the surface liquid layer remains unchanged. This model provides certain guidance for in-depth research on the ablation mechanism of ultra-lightweight quartz/phenolic composite.
Based on the ablation and heat protection mechanism of ultra-lightweight quartz/phenolic composite, a multi-physics field model for the ablation of composite containing silica phase transition was established. The surface and backside temperature, pyrolysis degree, different layer thicknesses and pore pressure distribution of ultra-lightweight quartz/phenolic composite were predicted. The numerical simulation obtained the variation law of the thickness of the liquid layer of surface silica through calculation, and the temperature results predicted by the model are consistent with the measurement results in the ablation experiment. According to the heat flow analysis results of various heat transfer modes, it can be seen that the most important factors affecting the prevention/insulation mechanism are thermal radiation, thermal blockage and silica gasification. Aiming at the typical application conditions of ultra-lightweight quartz/phenolic composite, the heat flux densities between 0.5 MW/m2 and 2.5 MW/m2 were used as environmental input parameters to study the ablation behavior of ultra-lightweight quartz/phenolic composite. The results show that the surface ablation retreat of ultra-light quartz/phenolic composite increases with the increase of heat flux density; When the heat flux density is less than 1.5 MW/m2, the thickness of the surface liquid layer increases with the increase of heat flux density. When the heat flux density is greater than 1.5 MW/m2, the thickness of the surface liquid layer remains unchanged. This model provides certain guidance for in-depth research on the ablation mechanism of ultra-lightweight quartz/phenolic composite.
2024,
41(9):
4817-4825.
doi: 10.13801/j.cnki.fhclxb.20240307.002
Abstract:
Three types of 3D woven composites (3DWC) with different warp paths were designed. Using a combination of experimental research, finite element analysis and SEM morphology analysis, the bending properties, damage mechanism and fracture morphology of 3DWC were studied. The results show that the warp paths have a significant effect on the bending properties of 3DWC. Compared to the stuffer plain woven composites (SPWC), with the increase of the warp yarns float length, the stuffer twill and stuffer satin woven composites (STWC and SSWC) bending strength increase by 54.64% and 127.61%, and the modulus increase by 44.11% and 47.11%, respectively. The failure modes of the SPWC are the fracture of the stuffer and the warp yarns, while the fracture modes of the STWC and SSWC are mainly yarns fracture and interface debonding. The stuffer yarns play the main role under the process of bending load, while the difference of warp yarn paths leads to the change of stress transfer, crack propagation, bending property and failure mode of three 3DWC.
Three types of 3D woven composites (3DWC) with different warp paths were designed. Using a combination of experimental research, finite element analysis and SEM morphology analysis, the bending properties, damage mechanism and fracture morphology of 3DWC were studied. The results show that the warp paths have a significant effect on the bending properties of 3DWC. Compared to the stuffer plain woven composites (SPWC), with the increase of the warp yarns float length, the stuffer twill and stuffer satin woven composites (STWC and SSWC) bending strength increase by 54.64% and 127.61%, and the modulus increase by 44.11% and 47.11%, respectively. The failure modes of the SPWC are the fracture of the stuffer and the warp yarns, while the fracture modes of the STWC and SSWC are mainly yarns fracture and interface debonding. The stuffer yarns play the main role under the process of bending load, while the difference of warp yarn paths leads to the change of stress transfer, crack propagation, bending property and failure mode of three 3DWC.
2024,
41(9):
4826-4836.
doi: 10.13801/j.cnki.fhclxb.20240417.001
Abstract:
Short fiber reinforced polymer composites (SFRPC) possess complex microscale structures, and understanding the fiber orientation distribution (FOD) within the SFRPC is a prerequisite for mechanical modeling of short fiber composites. However, the statistical analysis of fiber orientation requires collecting a large amount of fiber orientation information, and traditional manual annotation and retrieval of micrographs are costly and time-consuming, making it challenging to ensure both statistical efficiency and accuracy. In this study, image analysis algorithms were employed to capture geometric features of fiber cross-sections, and a corresponding image processing technique for FOD was developed, enabling the rapid statistical analysis of FOD information. The reasonable range of key parameters in image analysis algorithms was explored, and microstructure characterization was conducted on short glass fiber-reinforced and short carbon fiber-reinforced polyetherimide (SGF/PEI and SCF/PEI) composites fabricated using extrusion and injection molding processes. The statistical fiber orientation information was then incorporated into the laminate analogy approach (LAA) and Fu-Lauke model frameworks to predict the modulus and strength of the two composites with different volume fractions. The predicted results exhibited good agreement with finite element simulation results and experimental tensile test data. By combining the image processing technique for FOD with the prediction methods for composite mechanical properties, this study is helpful to more efficient and accurate understanding of the structure-property relationship of short fiber reinforced composites, providing valuable guidance for composite structural design.
Short fiber reinforced polymer composites (SFRPC) possess complex microscale structures, and understanding the fiber orientation distribution (FOD) within the SFRPC is a prerequisite for mechanical modeling of short fiber composites. However, the statistical analysis of fiber orientation requires collecting a large amount of fiber orientation information, and traditional manual annotation and retrieval of micrographs are costly and time-consuming, making it challenging to ensure both statistical efficiency and accuracy. In this study, image analysis algorithms were employed to capture geometric features of fiber cross-sections, and a corresponding image processing technique for FOD was developed, enabling the rapid statistical analysis of FOD information. The reasonable range of key parameters in image analysis algorithms was explored, and microstructure characterization was conducted on short glass fiber-reinforced and short carbon fiber-reinforced polyetherimide (SGF/PEI and SCF/PEI) composites fabricated using extrusion and injection molding processes. The statistical fiber orientation information was then incorporated into the laminate analogy approach (LAA) and Fu-Lauke model frameworks to predict the modulus and strength of the two composites with different volume fractions. The predicted results exhibited good agreement with finite element simulation results and experimental tensile test data. By combining the image processing technique for FOD with the prediction methods for composite mechanical properties, this study is helpful to more efficient and accurate understanding of the structure-property relationship of short fiber reinforced composites, providing valuable guidance for composite structural design.
2024,
41(9):
4837-4851.
doi: 10.13801/j.cnki.fhclxb.20231027.002
Abstract:
This study investigates the mechanical behavior of the transverse tensile properties of unidirectional carbon fiber-reinforced epoxy resin composites with varying fiber and void volume fractions, focusing on the influence of temperature and void volume fractions. For this purpose, an algorithm based on the maximum offset method for the generation of representative volume elements (RVE) was developed. A series of high-fidelity RVE models were constructed for unidirectional composites with different fiber and void volume fractions. To address the localization problems in damage models and to overcome the inefficiency of traditional finite element methods (FEM), a coupled non-local damage model with fast Fourier transform (FFT) computational framework was proposed. After comparative analysis with reported models and results, the proposed computational framework was validated to have good accuracy and reliability. Based on the validation, we investigated the influence of temperature, void and fiber volume fraction on the transverse tensile performance of composites. Specifically, elevated temperatures correspond to a decrease in the transverse tensile strength and modulus of the composites. In addition, an increase in voids results in a significant reduction in both tensile strength and modulus. Furthermore, as the fiber volume fraction increases, the transverse modulus of the composite material increases significantly while the tensile strength remains relatively constant. The computational framework and research findings presented in this study are expected to play a significant guiding role in the design and manufacturing of composite materials, aiming to enhance material performance and reliability.
This study investigates the mechanical behavior of the transverse tensile properties of unidirectional carbon fiber-reinforced epoxy resin composites with varying fiber and void volume fractions, focusing on the influence of temperature and void volume fractions. For this purpose, an algorithm based on the maximum offset method for the generation of representative volume elements (RVE) was developed. A series of high-fidelity RVE models were constructed for unidirectional composites with different fiber and void volume fractions. To address the localization problems in damage models and to overcome the inefficiency of traditional finite element methods (FEM), a coupled non-local damage model with fast Fourier transform (FFT) computational framework was proposed. After comparative analysis with reported models and results, the proposed computational framework was validated to have good accuracy and reliability. Based on the validation, we investigated the influence of temperature, void and fiber volume fraction on the transverse tensile performance of composites. Specifically, elevated temperatures correspond to a decrease in the transverse tensile strength and modulus of the composites. In addition, an increase in voids results in a significant reduction in both tensile strength and modulus. Furthermore, as the fiber volume fraction increases, the transverse modulus of the composite material increases significantly while the tensile strength remains relatively constant. The computational framework and research findings presented in this study are expected to play a significant guiding role in the design and manufacturing of composite materials, aiming to enhance material performance and reliability.
2024,
41(9):
4852-4862.
doi: 10.13801/j.cnki.fhclxb.20240228.001
Abstract:
4D X-ray CT in-situ tensile testing, along with deep learning technology, was used to characterize the damage and failure process of quasi-isotropic lay-up satin C/SiC composites under tensile loading, and to reveal the damage evolution mechanism under the coupled action of (0°/90°) lay-up tension and (±45°) lay-up shear. Using the deep learning image segmentation method, damages were extracted for quantitative analysis based on intelligent detection of matrix cracks, delamination of the material under loading. Furthermore, damage and failure mechanisms were investigated by examining the fracture morphology. It is found that ±45° oblique cracks account for the major part of matrix cracks. Oblique cracks were mainly induced by small cracks at the initial loading stage. Although transverse cracks were less than oblique ones, their lengths and crack opening distance developed rapidly. Delamination was induced by the deflection of matrix cracks along the interfaces between adjacent layers. For a (0°/90°) satin lay-up, transverse split took place in the tissue point region of 90° fibre tows, and accompanied by bending in the floating length region of 90° fibre tows. Fractures occurred in the tissue point region of 0° fibre tows, and accompanied by longitudinal split in the floating length region of 0° tows. For a (±45°) satin lay-up, oblique split and relatively sliding occurred in −45° (or +45°) tows. While fractures accompanied by fibre tow bridging and bending took place in the +45° (or −45°) tows of the same lay-up.
4D X-ray CT in-situ tensile testing, along with deep learning technology, was used to characterize the damage and failure process of quasi-isotropic lay-up satin C/SiC composites under tensile loading, and to reveal the damage evolution mechanism under the coupled action of (0°/90°) lay-up tension and (±45°) lay-up shear. Using the deep learning image segmentation method, damages were extracted for quantitative analysis based on intelligent detection of matrix cracks, delamination of the material under loading. Furthermore, damage and failure mechanisms were investigated by examining the fracture morphology. It is found that ±45° oblique cracks account for the major part of matrix cracks. Oblique cracks were mainly induced by small cracks at the initial loading stage. Although transverse cracks were less than oblique ones, their lengths and crack opening distance developed rapidly. Delamination was induced by the deflection of matrix cracks along the interfaces between adjacent layers. For a (0°/90°) satin lay-up, transverse split took place in the tissue point region of 90° fibre tows, and accompanied by bending in the floating length region of 90° fibre tows. Fractures occurred in the tissue point region of 0° fibre tows, and accompanied by longitudinal split in the floating length region of 0° tows. For a (±45°) satin lay-up, oblique split and relatively sliding occurred in −45° (or +45°) tows. While fractures accompanied by fibre tow bridging and bending took place in the +45° (or −45°) tows of the same lay-up.
2024,
41(9):
4863-4874.
doi: 10.13801/j.cnki.fhclxb.20240612.005
Abstract:
The continuous carbon fiber reinforced silicon carbide matrix composite (SiCf/SiC) has become an important thermal structural material for the next generation of aerospace engines due to its advantages of lightweight, high-temperature resistance, and high damage tolerance. However, the long fatigue test cycles and high costs severely limit the in-depth understanding and engineering applications of complex microstructures of SiCf/SiC. To fully exploit the advantages and tunability of SiCf/SiC, and to achieve the prediction of structural load response and optimization design, this study analyzed the fatigue life curves of unidirectional, orthogonal, and two-dimensional braiding SiCf/SiC using fatigue hysteresis models and progressive damage theory. The sensitivity evaluations of SiCf/SiC fatigue life were achieved by adjusting parameters such as interfacial shear stress (±20%), fiber strength (±5%), fiber Weibull modulus (±1%), and fiber volume fraction (±5%) through bias processing. The resulting upper and lower bounds of the fatigue life curves enveloped the primary experimental results. Based on the above analysis, a method for fitting fatigue life curves was verified, controlling hazard estimation and conservative estimation with damage parameters. The practicality of this method for practical engineering evaluation was demonstrated with simulated structures of SiCf/SiC turbine blades.
The continuous carbon fiber reinforced silicon carbide matrix composite (SiCf/SiC) has become an important thermal structural material for the next generation of aerospace engines due to its advantages of lightweight, high-temperature resistance, and high damage tolerance. However, the long fatigue test cycles and high costs severely limit the in-depth understanding and engineering applications of complex microstructures of SiCf/SiC. To fully exploit the advantages and tunability of SiCf/SiC, and to achieve the prediction of structural load response and optimization design, this study analyzed the fatigue life curves of unidirectional, orthogonal, and two-dimensional braiding SiCf/SiC using fatigue hysteresis models and progressive damage theory. The sensitivity evaluations of SiCf/SiC fatigue life were achieved by adjusting parameters such as interfacial shear stress (±20%), fiber strength (±5%), fiber Weibull modulus (±1%), and fiber volume fraction (±5%) through bias processing. The resulting upper and lower bounds of the fatigue life curves enveloped the primary experimental results. Based on the above analysis, a method for fitting fatigue life curves was verified, controlling hazard estimation and conservative estimation with damage parameters. The practicality of this method for practical engineering evaluation was demonstrated with simulated structures of SiCf/SiC turbine blades.
2024,
41(9):
4875-4887.
doi: 10.13801/j.cnki.fhclxb.20240402.003
Abstract:
Composite stiffened panel is typical structural form, which is widely used in aircraft wing, tail, and fuselage structures. When suffering aerodynamic loading, such composite stiffened panel on the wing surface of the wing is under compressive pressure, and this pressure could cause such panel to buckle or even failure. In this paper, an engineering method of reasonably predicting the buckling load of composite stiffened panels under axial compression is proposed, according to previous research on the stability engineering method composite stiffened panels under axial compression and stability engineering method of metal stiffened panels under axial compression which has been maturely applied in engineering. Therefore, two kinds of reinforcement composite stiffened panels (i.e., three types of Y type and two types of J type) are considered. The axial buckling load of the example is calculated by using the engineering method proposed in this paper, and the finite element numerical simulation and test verification are carried out. Compared with the experimental results, the relative error of the engineering method is less than 10%. Compared with the finite element calculation results, the relative errors of the other configurations are 5% except for one Y-shaped truss stiffened panel which is 10%, which meets the engineering requirements and proves the effectiveness of this method. This engineering method has been applied in the development of model aircraft. In addition, it is found that the weakening of the stringer edge of the stiffened panel will reduce the buckling load of the composite stiffened panel, and the weakening of the middle two stringers of the Y-stiffened panel can make the stringers more match the stiffness of the skin, and improve the failure strain level of the Y-stiffened panel.
Composite stiffened panel is typical structural form, which is widely used in aircraft wing, tail, and fuselage structures. When suffering aerodynamic loading, such composite stiffened panel on the wing surface of the wing is under compressive pressure, and this pressure could cause such panel to buckle or even failure. In this paper, an engineering method of reasonably predicting the buckling load of composite stiffened panels under axial compression is proposed, according to previous research on the stability engineering method composite stiffened panels under axial compression and stability engineering method of metal stiffened panels under axial compression which has been maturely applied in engineering. Therefore, two kinds of reinforcement composite stiffened panels (i.e., three types of Y type and two types of J type) are considered. The axial buckling load of the example is calculated by using the engineering method proposed in this paper, and the finite element numerical simulation and test verification are carried out. Compared with the experimental results, the relative error of the engineering method is less than 10%. Compared with the finite element calculation results, the relative errors of the other configurations are 5% except for one Y-shaped truss stiffened panel which is 10%, which meets the engineering requirements and proves the effectiveness of this method. This engineering method has been applied in the development of model aircraft. In addition, it is found that the weakening of the stringer edge of the stiffened panel will reduce the buckling load of the composite stiffened panel, and the weakening of the middle two stringers of the Y-stiffened panel can make the stringers more match the stiffness of the skin, and improve the failure strain level of the Y-stiffened panel.
2024,
41(9):
4888-4896.
doi: 10.13801/j.cnki.fhclxb.20231219.001
Abstract:
To reveal the effect of opening position on pinned-joints mechanical properties and failure mechanism of 3D woven composites, three different 3D woven composite structures were designed and prepared, and the load-bearing performance and damage modes of these composites with different opening positions was discussed. The results show that there are differences in the effect of end-diameter ratio (E/D) on composites with different structural parameters. When the E/D decreases from 3 to 2, the ultimate compressive strength of three structural composites decreases by 5.3%, 9.9%, and 5.9%, respectively. When the E/D decreases from 2 to 1, the ultimate compressive strength decreases by 73.3%, 68.9%, and 69.8%, respectively. When the E/D changes from 3 to 1, the damage mode of the composites changes from extrusion damage to interfacial debonding, and the damage propagation of each yarn layer presents obvious angle features.
To reveal the effect of opening position on pinned-joints mechanical properties and failure mechanism of 3D woven composites, three different 3D woven composite structures were designed and prepared, and the load-bearing performance and damage modes of these composites with different opening positions was discussed. The results show that there are differences in the effect of end-diameter ratio (E/D) on composites with different structural parameters. When the E/D decreases from 3 to 2, the ultimate compressive strength of three structural composites decreases by 5.3%, 9.9%, and 5.9%, respectively. When the E/D decreases from 2 to 1, the ultimate compressive strength decreases by 73.3%, 68.9%, and 69.8%, respectively. When the E/D changes from 3 to 1, the damage mode of the composites changes from extrusion damage to interfacial debonding, and the damage propagation of each yarn layer presents obvious angle features.
2024,
41(9):
4897-4908.
doi: 10.13801/j.cnki.fhclxb.20240019.003
Abstract:
Considering the strain characteristics of the composite structures changing with fatigue loading, so that this paper attempts to monitor the strain characteristics in real time during the fatigue cycle and assesses the fatigue life through the strain signals. However, from the published literatures, resistance strain gauge often suffered from early fatigue failure in the long-time dynamic testing, which is not suitable for strain signal acquisition during the full fatigue cycle. Therefore, the novel polyvinylidene difluoride piezoelectric film (PVDF) with high fatigue resistance is used to acquire fatigue characteristic signals of composite structures. The piezoelectric signals during the fatigue process of the composite laminates are obtained by pasting PVDF on the surface of carbon fiber reinforced plastic (CFRP) plates (T700/9A16). Based on the piezoelectric effect, the strain information during the fatigue process is converted into the piezoelectric signal from PVDF. Then, a Random Forest Regression (RFR) algorithm is trained based on the database generated from the experimental tests to efficiently establish the correlation between the piezoelectric signals and fatigue cycles of composite laminates. Through the trained RFR network, the actual fatigue cycles of the test pieces can be accurately predicted based on the piezoelectric signals, in which the maximum percentage error of logarithms of fatigue cycles is controlled within 5%. This paper provides a new research idea and technical support for the fatigue life assessment of composite materials.
Considering the strain characteristics of the composite structures changing with fatigue loading, so that this paper attempts to monitor the strain characteristics in real time during the fatigue cycle and assesses the fatigue life through the strain signals. However, from the published literatures, resistance strain gauge often suffered from early fatigue failure in the long-time dynamic testing, which is not suitable for strain signal acquisition during the full fatigue cycle. Therefore, the novel polyvinylidene difluoride piezoelectric film (PVDF) with high fatigue resistance is used to acquire fatigue characteristic signals of composite structures. The piezoelectric signals during the fatigue process of the composite laminates are obtained by pasting PVDF on the surface of carbon fiber reinforced plastic (CFRP) plates (T700/9A16). Based on the piezoelectric effect, the strain information during the fatigue process is converted into the piezoelectric signal from PVDF. Then, a Random Forest Regression (RFR) algorithm is trained based on the database generated from the experimental tests to efficiently establish the correlation between the piezoelectric signals and fatigue cycles of composite laminates. Through the trained RFR network, the actual fatigue cycles of the test pieces can be accurately predicted based on the piezoelectric signals, in which the maximum percentage error of logarithms of fatigue cycles is controlled within 5%. This paper provides a new research idea and technical support for the fatigue life assessment of composite materials.
2024,
41(9):
4909-4918.
doi: 10.13801/j.cnki.fhclxb.20240521.005
Abstract:
The demand for protective composites that can rapidly attenuate stress waves is high across various industrial sectors such as civil defense, armor, and ships. Drawing inspiration from dragonfly wings, this paper introduces a novel design of protective composites combining the principle of particle local resonance and bioinspired microstructures. The key findings include: (1) When the frequency of the incident wave closely matches the intrinsic frequency of the local resonance unit, maximum excitation of the local resonance mechanism occurs, and a significant amount of incident stress wave energy is converted into the mechanical energy of particles; (2) The intrinsic frequency of a local resonant unit decreases with the increase of the core particle size and density, and the soft coating thickness, but increases with the rise in the elastic modulus of the soft coatings; (3) A hybrid design with a mix of units with varying intrinsic frequencies incorporated into the composite material, can achieve effective attenuation of incident stress waves across a broad frequency range. This research provides valuable guidance for developing high-performance impact-resistant composites utilizing the principles of local resonance and bionic microstructures.
The demand for protective composites that can rapidly attenuate stress waves is high across various industrial sectors such as civil defense, armor, and ships. Drawing inspiration from dragonfly wings, this paper introduces a novel design of protective composites combining the principle of particle local resonance and bioinspired microstructures. The key findings include: (1) When the frequency of the incident wave closely matches the intrinsic frequency of the local resonance unit, maximum excitation of the local resonance mechanism occurs, and a significant amount of incident stress wave energy is converted into the mechanical energy of particles; (2) The intrinsic frequency of a local resonant unit decreases with the increase of the core particle size and density, and the soft coating thickness, but increases with the rise in the elastic modulus of the soft coatings; (3) A hybrid design with a mix of units with varying intrinsic frequencies incorporated into the composite material, can achieve effective attenuation of incident stress waves across a broad frequency range. This research provides valuable guidance for developing high-performance impact-resistant composites utilizing the principles of local resonance and bionic microstructures.
2024,
41(9):
4919-4931.
doi: 10.13801/j.cnki.fhclxb.20240801.001
Abstract:
The lightweight of automobile structures is an important way to reduce automobile energy consumption and increase cruising range. Although thermosetting matrix composites such as fiber reinforced epoxy have extremely high mechanical properties and lightweight potential, their applications in automotive structures are hindered by high manufacturing energy consumption, maintenance costs, and low design and manufacturing efficiency. A new type of "Double-Double" layup (DD) thermoplastic laminate ([±Ф/±Ψ]n) is expected to solve the above problems. This paper analyzed the advantages of DD laminates compared to π/4 laminates (Quad) in lightweight design, and compared the mechanical properties and design analysis processes of laminates with different layup methods (DD, Woven, Quad layups) and different matrix materials (thermosetting epoxy resin, thermoplastic nylon 6). The results showed that the stiffness and strength of high axial stiffness DD laminates in the main load direction were much higher than those of Woven laminates with the same fiber and matrix. The stiffness performance of DD laminates was similar to that of Quad laminates with the same fiber and matrix, but the design efficiency of DD laminates was higher than that of Quad laminates. At the same time, research on DD thermoplastic laminates of carbon fiber reinforced nylon 6 composites (carbon/PA6) found that although the tensile modulus and tensile strength of unidirectional carbon/PA6 were lower than those of unidirectional carbon/epoxy, DD carbon/PA6 laminates could still be designed through the layup so that the stiffness and strength in the main load direction exceeded that of Woven carbon/epoxy laminates. Moreover, themoplastic carbon/PA6 has excellent repairability and recyclability, showing its advantages in automobile structural design.
The lightweight of automobile structures is an important way to reduce automobile energy consumption and increase cruising range. Although thermosetting matrix composites such as fiber reinforced epoxy have extremely high mechanical properties and lightweight potential, their applications in automotive structures are hindered by high manufacturing energy consumption, maintenance costs, and low design and manufacturing efficiency. A new type of "Double-Double" layup (DD) thermoplastic laminate ([±Ф/±Ψ]n) is expected to solve the above problems. This paper analyzed the advantages of DD laminates compared to π/4 laminates (Quad) in lightweight design, and compared the mechanical properties and design analysis processes of laminates with different layup methods (DD, Woven, Quad layups) and different matrix materials (thermosetting epoxy resin, thermoplastic nylon 6). The results showed that the stiffness and strength of high axial stiffness DD laminates in the main load direction were much higher than those of Woven laminates with the same fiber and matrix. The stiffness performance of DD laminates was similar to that of Quad laminates with the same fiber and matrix, but the design efficiency of DD laminates was higher than that of Quad laminates. At the same time, research on DD thermoplastic laminates of carbon fiber reinforced nylon 6 composites (carbon/PA6) found that although the tensile modulus and tensile strength of unidirectional carbon/PA6 were lower than those of unidirectional carbon/epoxy, DD carbon/PA6 laminates could still be designed through the layup so that the stiffness and strength in the main load direction exceeded that of Woven carbon/epoxy laminates. Moreover, themoplastic carbon/PA6 has excellent repairability and recyclability, showing its advantages in automobile structural design.
2024,
41(9):
4932-4941.
doi: 10.13801/j.cnki.fhclxb.20240223.003
Abstract:
With the increasing demand of precision instruments on the bearing platform structure, honeycomb structure has been widely concerned because of its light weight and ultra-high stability. In order to meet the requirements of the special-shaped composite bearing platform, this paper used the combination of hot pressing and resin impregnation carbonization and chemical vapor deposition (CVD) to prepare the curved carbon/carbon honey-comb structure samples of different specifications. Then, according to the structural characteristics of curved honeycomb and the service environment, a test method of uniform load was designed to conduct compression tests on different samples. The influences of honeycomb thickness, layering angle and curvature radius on the mechanical properties of curved honeycomb were analyzed. The results show that when the radial thickness of honeycomb increases, the bending degree of honeycomb wall increases, the load on honeycomb double-walled space increases, and the cracking tendency of adhesive surface becomes more obvious. When the orientation of honeycomb fiber changes from 0° to 45°, the bending mode of honeycomb wall changes to non-buckling, ductile buckling and plastic buckling. When the curvature radius of curved honeycomb decreases, the failure mode gradually changes from decudation cracking to buckling fracture of honeycomb wall. The curved carbon/carbon honeycomb prepared in this paper has a compressive strength of 1.48 MPa, and has good mechanical properties, which can meet the requirements of increasingly complex aerospace structures.
With the increasing demand of precision instruments on the bearing platform structure, honeycomb structure has been widely concerned because of its light weight and ultra-high stability. In order to meet the requirements of the special-shaped composite bearing platform, this paper used the combination of hot pressing and resin impregnation carbonization and chemical vapor deposition (CVD) to prepare the curved carbon/carbon honey-comb structure samples of different specifications. Then, according to the structural characteristics of curved honeycomb and the service environment, a test method of uniform load was designed to conduct compression tests on different samples. The influences of honeycomb thickness, layering angle and curvature radius on the mechanical properties of curved honeycomb were analyzed. The results show that when the radial thickness of honeycomb increases, the bending degree of honeycomb wall increases, the load on honeycomb double-walled space increases, and the cracking tendency of adhesive surface becomes more obvious. When the orientation of honeycomb fiber changes from 0° to 45°, the bending mode of honeycomb wall changes to non-buckling, ductile buckling and plastic buckling. When the curvature radius of curved honeycomb decreases, the failure mode gradually changes from decudation cracking to buckling fracture of honeycomb wall. The curved carbon/carbon honeycomb prepared in this paper has a compressive strength of 1.48 MPa, and has good mechanical properties, which can meet the requirements of increasingly complex aerospace structures.
2024,
41(9):
4942-4955.
doi: 10.13801/j.cnki.fhclxb.20240311.004
Abstract:
Delamination damage is one of the primary damage modes in aerospace composite structures. Mode I delamination exhibits characteristics of low initial fracture toughness and complex damage patterns. Analyzing the interrelationships among three damage mechanisms at the crack tip region and bridging fiber damage evolution plays a crucial role in studying Mode I delamination. This paper specifically designs T700 level carbon fiber/epoxy composite laminates with three different interlayer configurations (0//0, 0//45, 0//90) and conducts Mode I delamination tests. By observing the initiation and evolution of delamination, summarizing double cantilever beam (DCB) experimental results in load-displacement curves and R-curves, and employing various characterization methods like SEM analysis based on specimen fracture surfaces, it reveals the damage mechanisms at the crack tip. Subsequently, a new approach to decoupling layered damage mechanisms is proposed, based on three bilinear cohesive constitutive laws. This method establishes a cohesive element model to decouple layered damage mechanisms at different damage scales, independently characterizing the contributions of different damage mechanisms during layered propagation. Parameters required for simulation are obtained from experiments, and the simulated results exhibit good consistency with experimental data.
Delamination damage is one of the primary damage modes in aerospace composite structures. Mode I delamination exhibits characteristics of low initial fracture toughness and complex damage patterns. Analyzing the interrelationships among three damage mechanisms at the crack tip region and bridging fiber damage evolution plays a crucial role in studying Mode I delamination. This paper specifically designs T700 level carbon fiber/epoxy composite laminates with three different interlayer configurations (0//0, 0//45, 0//90) and conducts Mode I delamination tests. By observing the initiation and evolution of delamination, summarizing double cantilever beam (DCB) experimental results in load-displacement curves and R-curves, and employing various characterization methods like SEM analysis based on specimen fracture surfaces, it reveals the damage mechanisms at the crack tip. Subsequently, a new approach to decoupling layered damage mechanisms is proposed, based on three bilinear cohesive constitutive laws. This method establishes a cohesive element model to decouple layered damage mechanisms at different damage scales, independently characterizing the contributions of different damage mechanisms during layered propagation. Parameters required for simulation are obtained from experiments, and the simulated results exhibit good consistency with experimental data.
2024,
41(9):
4956-4967.
doi: 10.13801/j.cnki.fhclxb.20240308.001
Abstract:
In order to further improve the crushing resistance and energy-absorbing capacity of the honeycomb structure, by periodically arraying typical star-shaped and star-rhombic cells, the reentrant star-shaped honeycomb structures (RSH) and the novel in-plane enhanced star-rhombic honeycomb structures (ESH) were constructed in this paper. The in-plane mechanical response and energy absorption characteristics of ESH under different loading directions were systematically investigated through experiments and finite element (FE) simulations. Compared with RSH, the negative Poisson's ratio characteristics of ESH under quasi-static compression are weakened, but the energy-absorbing capacities are significantly improved. In addition, by combining the deformation features of micro-topological cells, the deformation mechanism that the stress-strain response of ESH-y exhibits a double-plateau characteristic at low velocities of crushing is revealed, and the influence of the structural parameters α, t, and b on the plateau stresses is discussed. Based on the periodic layer-by-layer collapse deformation features of ESH under high-velocity crushing and the momentum theorem, the theoretical solutions of the high-velocity plateau stress in different loading directions are obtained, and theoretical results are in good agreement with FE results. This study can provide a reference for the innovative design of novel negative Poisson's ratio structures with better mechanical properties.
In order to further improve the crushing resistance and energy-absorbing capacity of the honeycomb structure, by periodically arraying typical star-shaped and star-rhombic cells, the reentrant star-shaped honeycomb structures (RSH) and the novel in-plane enhanced star-rhombic honeycomb structures (ESH) were constructed in this paper. The in-plane mechanical response and energy absorption characteristics of ESH under different loading directions were systematically investigated through experiments and finite element (FE) simulations. Compared with RSH, the negative Poisson's ratio characteristics of ESH under quasi-static compression are weakened, but the energy-absorbing capacities are significantly improved. In addition, by combining the deformation features of micro-topological cells, the deformation mechanism that the stress-strain response of ESH-y exhibits a double-plateau characteristic at low velocities of crushing is revealed, and the influence of the structural parameters α, t, and b on the plateau stresses is discussed. Based on the periodic layer-by-layer collapse deformation features of ESH under high-velocity crushing and the momentum theorem, the theoretical solutions of the high-velocity plateau stress in different loading directions are obtained, and theoretical results are in good agreement with FE results. This study can provide a reference for the innovative design of novel negative Poisson's ratio structures with better mechanical properties.
2024,
41(9):
4968-4980.
doi: 10.13801/j.cnki.fhclxb.20240301.001
Abstract:
Carbon fiber reinforced thermoplastic polymer (CFRTP) is the preferred material for weight loss and efficiency improvement of high-end equipment. However, CFRTP is a typical difficult-to-machine material, and damage occurs frequently during processing. In this paper, the process of material removal and damage formation during cutting CFRTP was simulated and experimentally studied. CFRTP is prone to plastic deformation during cutting, and the material properties are greatly affected by temperature. In this paper, a three-dimensional orthogonal cutting simulation model of CFRTP was established, and the J-C model was introduced to characterize the elastic-plastic deformation of resin at different temperatures. The effects of temperature and fiber orientation angle on the cutting removal process of CFRTP were analyzed. The results show that when cutting at room temperature, and the fiber orientation angles are 0° and 45°, the machined surface is relatively flat and the processing quality is better; When the fiber orientation angles are 90° and 135°, the bending degree of the fiber increases obviously, and there are cracks on the machined surface, and the processing quality is poor. When cutting at room temperature, and the fiber orientation angle is 0°, the unremoved material appears on the machined surface; when the fiber orientation angle is 45°, cracks and fiber pull-out phenomenon appear on the machined surface. When the fiber orientation angles are 90° and 135°, the machined surface is more cracked, and the workpiece has obvious out-of-plane deformation along the thickness direction. The material with out-of-plane deformation is difficult to be effectively removed.
Carbon fiber reinforced thermoplastic polymer (CFRTP) is the preferred material for weight loss and efficiency improvement of high-end equipment. However, CFRTP is a typical difficult-to-machine material, and damage occurs frequently during processing. In this paper, the process of material removal and damage formation during cutting CFRTP was simulated and experimentally studied. CFRTP is prone to plastic deformation during cutting, and the material properties are greatly affected by temperature. In this paper, a three-dimensional orthogonal cutting simulation model of CFRTP was established, and the J-C model was introduced to characterize the elastic-plastic deformation of resin at different temperatures. The effects of temperature and fiber orientation angle on the cutting removal process of CFRTP were analyzed. The results show that when cutting at room temperature, and the fiber orientation angles are 0° and 45°, the machined surface is relatively flat and the processing quality is better; When the fiber orientation angles are 90° and 135°, the bending degree of the fiber increases obviously, and there are cracks on the machined surface, and the processing quality is poor. When cutting at room temperature, and the fiber orientation angle is 0°, the unremoved material appears on the machined surface; when the fiber orientation angle is 45°, cracks and fiber pull-out phenomenon appear on the machined surface. When the fiber orientation angles are 90° and 135°, the machined surface is more cracked, and the workpiece has obvious out-of-plane deformation along the thickness direction. The material with out-of-plane deformation is difficult to be effectively removed.
2024,
41(9):
4981-4992.
doi: 10.13801/j.cnki.fhclxb.20240422.001
Abstract:
To gain a comprehensive understanding of the non-isothermal crystallization behavior of carbon fiber reinforced polyetheretherketone (CF/PEEK) composites, optimize process parameters, and enhance the structural forming quality and thermal and mechanical properties of thermoplastic composites, this study investigated the crystallization behavior of CF/PEEK thermoplastic composite materials under different cooling rates. Through conducting differential scanning calorimetry (DSC) experiments on CF/PEEK composite materials at various cooling rates, the non-isothermal crystallization behavior of CF/PEEK composite materials was analyzed using the Avrami, Ozawa, and Mo equations. The activation energy of non-isothermal crystallization was determined, and the crystallization kinetics model was developed. In addition, in-situ detection of the CF/PEEK composite material melting/crystallization process was carried out using fiber Bragg grating (FBG), and the strain variation mechanism during the polymer matrix melting/crystallization process was analyzed in conjunction with the crystallization kinetics model. The results indicate that the crystallinity of CF/PEEK composite materials decreases with increasing cooling rate, accompanied by a decrease in the corresponding crystallization time. It has been demonstrated that the established crystallinity crystallization kinetic model in this study effectively analyzes the crystallization process of CF/PEEK composite materials under different cooling rate. Additionally, it can be combined with fiber Bragg grating strain detection to analyze the influence of matrix phase transition on characteristic strain during the melting/crystallization process of CF/PEEK thermo-plastic composites.
To gain a comprehensive understanding of the non-isothermal crystallization behavior of carbon fiber reinforced polyetheretherketone (CF/PEEK) composites, optimize process parameters, and enhance the structural forming quality and thermal and mechanical properties of thermoplastic composites, this study investigated the crystallization behavior of CF/PEEK thermoplastic composite materials under different cooling rates. Through conducting differential scanning calorimetry (DSC) experiments on CF/PEEK composite materials at various cooling rates, the non-isothermal crystallization behavior of CF/PEEK composite materials was analyzed using the Avrami, Ozawa, and Mo equations. The activation energy of non-isothermal crystallization was determined, and the crystallization kinetics model was developed. In addition, in-situ detection of the CF/PEEK composite material melting/crystallization process was carried out using fiber Bragg grating (FBG), and the strain variation mechanism during the polymer matrix melting/crystallization process was analyzed in conjunction with the crystallization kinetics model. The results indicate that the crystallinity of CF/PEEK composite materials decreases with increasing cooling rate, accompanied by a decrease in the corresponding crystallization time. It has been demonstrated that the established crystallinity crystallization kinetic model in this study effectively analyzes the crystallization process of CF/PEEK composite materials under different cooling rate. Additionally, it can be combined with fiber Bragg grating strain detection to analyze the influence of matrix phase transition on characteristic strain during the melting/crystallization process of CF/PEEK thermo-plastic composites.
2024,
41(9):
4993-5003.
doi: 10.13801/j.cnki.fhclxb.20240410.001
Abstract:
In order to study the pressure-sinkage characteristics of T1000 carbon fiber reinforced composite case, transverse comparative tests of macroscopic mechanical properties of domestic T1000 carbon fiber composite were carried out in this paper. On the basis, the selection of the composite materials was implemented. The high precision finite element model of the composite case was established based on the layup in the process, cubic spline thickness prediction method and non-geodesic theory. The stress-strain response of the composite case dome was calculated, and the damage evolution of the composite case, the failure mode and the burst pressure were predicted based on the progressive damage analysis method. Finally, the simulation model was validated by hydraulic tests. The results show that the performance of domestic T1000 carbon fiber is equivalent to Toray T1000G, and the comprehensive performance of CCF1000S is the best. The deformation disharmony caused by the stiffness discontinuity between the case and the metal boss makes the dome part subject to the coupling effects of bending, tension and shear, which results in the stress level of the dome shoulder being obviously higher than that on both sides. The progressive damage model based on the 3D Hashin damage criterion can effectively describe the damage and failure process of the case, and predict the bursting pressure and failure location of the case more accurately.
In order to study the pressure-sinkage characteristics of T1000 carbon fiber reinforced composite case, transverse comparative tests of macroscopic mechanical properties of domestic T1000 carbon fiber composite were carried out in this paper. On the basis, the selection of the composite materials was implemented. The high precision finite element model of the composite case was established based on the layup in the process, cubic spline thickness prediction method and non-geodesic theory. The stress-strain response of the composite case dome was calculated, and the damage evolution of the composite case, the failure mode and the burst pressure were predicted based on the progressive damage analysis method. Finally, the simulation model was validated by hydraulic tests. The results show that the performance of domestic T1000 carbon fiber is equivalent to Toray T1000G, and the comprehensive performance of CCF1000S is the best. The deformation disharmony caused by the stiffness discontinuity between the case and the metal boss makes the dome part subject to the coupling effects of bending, tension and shear, which results in the stress level of the dome shoulder being obviously higher than that on both sides. The progressive damage model based on the 3D Hashin damage criterion can effectively describe the damage and failure process of the case, and predict the bursting pressure and failure location of the case more accurately.
2024,
41(9):
5004-5015.
doi: 10.13801/j.cnki.fhclxb.20240423.002
Abstract:
Carbon fiber reinforced polymer (CFRP) are widely used in steel structure reinforcement through adhesively bonding, making it crucial to inspect CFRP-steel adhesively bonded structures (ABCSS) to ensure their structural integrity and safety. However, the distinct physical properties of CFRP, epoxy resin, and steel pose challenges in accurately detecting internal damages in such specialized hybrid structures. To address this issue, this study proposes an enhanced electromagnetic induction thermography detection method to enhance the detection of internal damages in ABCSS. This method initially utilizes a conventional electromagnetic induction thermography system to obtain surface temperature data of the object under inspection, followed by preprocessing of the surface temperature data. Subsequently, a designed convolutional autoencoder (CAE) model is employed to extract pixel-level deep thermal features from the preprocessed surface temperature data. Finally, the extracted deep thermal features are utilized to generate enhanced detection results, thereby improving the visibility of damages. Experimental results on ABCSS specimens containing delamination, debonding, and cracks demonstrate that enhanced electromagnetic in-duction thermography effectively enhances the visibility of internal damages. This enhancement contributes to accurately assessing the quality of ABCSS, thereby improving the safety of such structures.
Carbon fiber reinforced polymer (CFRP) are widely used in steel structure reinforcement through adhesively bonding, making it crucial to inspect CFRP-steel adhesively bonded structures (ABCSS) to ensure their structural integrity and safety. However, the distinct physical properties of CFRP, epoxy resin, and steel pose challenges in accurately detecting internal damages in such specialized hybrid structures. To address this issue, this study proposes an enhanced electromagnetic induction thermography detection method to enhance the detection of internal damages in ABCSS. This method initially utilizes a conventional electromagnetic induction thermography system to obtain surface temperature data of the object under inspection, followed by preprocessing of the surface temperature data. Subsequently, a designed convolutional autoencoder (CAE) model is employed to extract pixel-level deep thermal features from the preprocessed surface temperature data. Finally, the extracted deep thermal features are utilized to generate enhanced detection results, thereby improving the visibility of damages. Experimental results on ABCSS specimens containing delamination, debonding, and cracks demonstrate that enhanced electromagnetic in-duction thermography effectively enhances the visibility of internal damages. This enhancement contributes to accurately assessing the quality of ABCSS, thereby improving the safety of such structures.
2024,
41(9):
5016-5031.
doi: 10.13801/j.cnki.fhclxb.20240419.002
Abstract:
The metallic-faced composite corrugated sandwich structure, which combines the impact resistance of metals with the high specific strength and stiffness of composites, represents an exemplary form of innovative construction. During its service life, the sandwich structure is subjected to multiple impact conditions, yet the patterns of damage from repeated impacts and the post-damage residual strength are not yet clearly understood. To address this, a comprehensive study was conducted through a series of impact tests and CT non-destructive scanning analyses, delving into the dynamic response to low-velocity impacts, internal failure modes, load-displacement characteristics, and energy absorption features. Furthermore, based on these findings, plane compression tests were carried out on impacted specimens to analyze the residual compressive strength and failure modes after multiple impacts. The findings indicate that the initial impact inflicts the most damage, and with increasing impact frequency, the energy-absorbing capacity and impact resistance of the sandwich structure diminish. In multiple impacts, the predominant damage modes in the sandwich structure include matrix cracking, delamination, and fiber breakage in the core material, with higher energy impacts invariably causing more extensive damage. Moreover, as the number of impacts increases, the accumulation of damage approaches saturation, and the residual compressive strength trends towards a threshold value.
The metallic-faced composite corrugated sandwich structure, which combines the impact resistance of metals with the high specific strength and stiffness of composites, represents an exemplary form of innovative construction. During its service life, the sandwich structure is subjected to multiple impact conditions, yet the patterns of damage from repeated impacts and the post-damage residual strength are not yet clearly understood. To address this, a comprehensive study was conducted through a series of impact tests and CT non-destructive scanning analyses, delving into the dynamic response to low-velocity impacts, internal failure modes, load-displacement characteristics, and energy absorption features. Furthermore, based on these findings, plane compression tests were carried out on impacted specimens to analyze the residual compressive strength and failure modes after multiple impacts. The findings indicate that the initial impact inflicts the most damage, and with increasing impact frequency, the energy-absorbing capacity and impact resistance of the sandwich structure diminish. In multiple impacts, the predominant damage modes in the sandwich structure include matrix cracking, delamination, and fiber breakage in the core material, with higher energy impacts invariably causing more extensive damage. Moreover, as the number of impacts increases, the accumulation of damage approaches saturation, and the residual compressive strength trends towards a threshold value.
2024,
41(9):
5032-5038.
doi: 10.13801/j.cnki.fhclxb.20240521.003
Abstract:
More and more attention is being paid to the filtration failure and the following disposal issues of filter media with its wide application of baghouse dust removal technology. In this paper, TG-IR-GC/MS and DMA are used to investigate the pyrolysis and dynamic mechanical properties of polytetrafluoroethylene (PTFE) fiber needle punched filter media in comparison with aramid fiber filter media, with the aim to provide the guidance of rational application and disposal of PTFE filter media. The results showed that PTFE decomposed in air, producing harmful gases such as carbonyl fluoride, tetrafluoroethylene, and hexafluoropropylene. Compared to PTFE and aramid fiber woven fabric reinforced aramid fiber filter media, the tensile strength of PTFE woven fabric reinforced PTFE fiber needle punched filter media was decreased significantly with the increase of heating temperature. In addition, PTFE filter media exhibited poor creep resistance while PTFE fiber woven fabric reinforced aramid fiber filter media had good creep resistance at low stress level, and aramid woven fabric reinforced aramid fiber filter media exhibited good creep resistance even at higher stress level.
More and more attention is being paid to the filtration failure and the following disposal issues of filter media with its wide application of baghouse dust removal technology. In this paper, TG-IR-GC/MS and DMA are used to investigate the pyrolysis and dynamic mechanical properties of polytetrafluoroethylene (PTFE) fiber needle punched filter media in comparison with aramid fiber filter media, with the aim to provide the guidance of rational application and disposal of PTFE filter media. The results showed that PTFE decomposed in air, producing harmful gases such as carbonyl fluoride, tetrafluoroethylene, and hexafluoropropylene. Compared to PTFE and aramid fiber woven fabric reinforced aramid fiber filter media, the tensile strength of PTFE woven fabric reinforced PTFE fiber needle punched filter media was decreased significantly with the increase of heating temperature. In addition, PTFE filter media exhibited poor creep resistance while PTFE fiber woven fabric reinforced aramid fiber filter media had good creep resistance at low stress level, and aramid woven fabric reinforced aramid fiber filter media exhibited good creep resistance even at higher stress level.
2024,
41(9):
5039-5052.
doi: 10.13801/j.cnki.fhclxb.20240722.004
Abstract:
Voids have significant influence on the shear properties of carbon fiber/epoxy resin composites. In this paper, carbon fiber/epoxy resin composite laminates with varies porosity were produced by hygroscopic saturation and stepping down the autoclave pressures. Short beam shear (SBS) tests were performed to establish the influence curve of different porosity on SBS strength. The evolution of shear damage induced by voids and the degradation mechanism of SBS strength were both studied by ultrasonic imaging and metallographic observation. The result shows that when the porosity is less than 1.0%, the SBS strength retention rate is about 88.4%-90.8%; When the porosity increases to 1.0%-1.5%, the SBS strength retention rate is about 74.9%-80.6%; When the porosity increases to 1.5%-2.0%, the SBS strength retention rate is about 66.3%-71.9%; When the porosity increases to 2.0%-3.0%, the SBS strength decreases sharply, and the SBS strength retention rate drops below 50%. The SBS shear failure mode is very sensitive to voids. Shear failure mainly occurs close to void and the surrounding stress concentration. The higher the porosity, the more obvious the promotion effect of voids on crack initiation and propagation, yielding the higher crack density, the earlier crack occurrence time, and the faster propagation speed.
Voids have significant influence on the shear properties of carbon fiber/epoxy resin composites. In this paper, carbon fiber/epoxy resin composite laminates with varies porosity were produced by hygroscopic saturation and stepping down the autoclave pressures. Short beam shear (SBS) tests were performed to establish the influence curve of different porosity on SBS strength. The evolution of shear damage induced by voids and the degradation mechanism of SBS strength were both studied by ultrasonic imaging and metallographic observation. The result shows that when the porosity is less than 1.0%, the SBS strength retention rate is about 88.4%-90.8%; When the porosity increases to 1.0%-1.5%, the SBS strength retention rate is about 74.9%-80.6%; When the porosity increases to 1.5%-2.0%, the SBS strength retention rate is about 66.3%-71.9%; When the porosity increases to 2.0%-3.0%, the SBS strength decreases sharply, and the SBS strength retention rate drops below 50%. The SBS shear failure mode is very sensitive to voids. Shear failure mainly occurs close to void and the surrounding stress concentration. The higher the porosity, the more obvious the promotion effect of voids on crack initiation and propagation, yielding the higher crack density, the earlier crack occurrence time, and the faster propagation speed.
2024,
41(9):
5053-5069.
doi: 10.13801/j.cnki.fhclxb.20240724.001
Abstract:
Carbon fiber/polyetheretherketone (CF/PEEK) is widely used in the high-end equipment manufacturing such as aerospace and transportation, due to its lightweight, high strength, and easy to recyclability. However, its strong brittle-soft ductile dual-component structure poses challenges for machining. In this study, the longitudinal-torsional ultrasonic vibration-assisted milling (UVAM) method was introduced, utilizing its high pulse and intermittent contact characteristics to mill CF/PEEK unidirectional laminates. The effects of machining parameters on output characteristics (cutting force, cutting temperature, surface roughness, and damage defects) were compared between UVAM and conventional milling (CM). The results show that UVAM reduces cutting force and surface roughness by 4%-54.1% and 15.8%-66.9%, respectively. Additionally, the UVAM method significantly extends tool life, reduces cumulative temperature, and suppresses damage defects. A multi-objective optimization model for machining parameters is established using the NSGA-II algorithm, targeting extended tool life, reduced surface roughness, and minimized surface defects. The optimal solution is obtained and experimentally validated, with model errors ranging from 2.24% to 22.2%.
Carbon fiber/polyetheretherketone (CF/PEEK) is widely used in the high-end equipment manufacturing such as aerospace and transportation, due to its lightweight, high strength, and easy to recyclability. However, its strong brittle-soft ductile dual-component structure poses challenges for machining. In this study, the longitudinal-torsional ultrasonic vibration-assisted milling (UVAM) method was introduced, utilizing its high pulse and intermittent contact characteristics to mill CF/PEEK unidirectional laminates. The effects of machining parameters on output characteristics (cutting force, cutting temperature, surface roughness, and damage defects) were compared between UVAM and conventional milling (CM). The results show that UVAM reduces cutting force and surface roughness by 4%-54.1% and 15.8%-66.9%, respectively. Additionally, the UVAM method significantly extends tool life, reduces cumulative temperature, and suppresses damage defects. A multi-objective optimization model for machining parameters is established using the NSGA-II algorithm, targeting extended tool life, reduced surface roughness, and minimized surface defects. The optimal solution is obtained and experimentally validated, with model errors ranging from 2.24% to 22.2%.
2024,
41(9):
5070-5082.
doi: 10.13801/j.cnki.fhclxb.20240603.001
Abstract:
The fiber reinforced cement composite blended with phosphogypsum solid waste was successfully prepared using the flow slurry method. Firstly, the solid waste phosphogypsum was neutralized with quicklime, decontaminated and baked to stimulate its cementitious properties, and then mixed with mineral powder and steel sand in the ratio of 5∶4∶1 to form modified solid waste phosphogypsum mix (MWPM) to replace part of the cement as an auxiliary cementitious material. At the same time, solid waste phosphogypsum aggregate was used to replace part of the natural fine aggregate, while a small amount of polyoxymethylene (POM) fibers and wood pulp fibers were considered to be incorporated to carry out a baseline proportion design study of fiber-reinforced cementitious composites and to analyses their strength and micro-mechanisms in combination with XRD and SEM. The results show that the dosage of MWPM with phosphogypsum aggregate has almost no effect on the density, water absorption, thermal conductivity, etc. of solid waste fiber-reinforced cement boards; Although the strength in the early stage decreases slightly with the increase in the dosage of MWPM, it can still be maintained at about 4 MPa when the dosage reaches about 18%, and the strength in the later stage is partially enhanced compared to that of MWPM, while the ratio of flexural strength is not less than 70% after freeze-thaw test, which meets the specification requirements of non-load-bearing fiber reinforced cement board. Phosphogypsum aggregates have a minor reinforcing effect on the composites, which is relatively optimal at 20%; Based on the above research, a benchmark mix ratio for fiber-reinforced cement-based composite materials incorporating phosphogypsum waste has been proposed. This mix ratio effectively utilizes phosphogypsum waste at 155.39 kg/m³, reduces cement consumption by 78.58 kg/m³, and lowers carbon dioxide emissions by 27.60 kg/m³. Microscopic analysis reveals that dihydrate phosphogypsum, ettringite, and C-S-H gel interpenetrate to form a three-dimensional spatial structure. Additionally, the incorporation of POM fibers and wood pulp fibers enhances the integration of the matrix, aggregates, and the two types of fibers, creating a denser overall structure. This structure further improves the mechanical performance of the specimens. The fiber-reinforced cement-based composite material with mixed phosphogypsum waste demonstrates excellent mechanical properties and waste utilization efficiency, providing a reference for the development of non-load-bearing green insulation materials.
The fiber reinforced cement composite blended with phosphogypsum solid waste was successfully prepared using the flow slurry method. Firstly, the solid waste phosphogypsum was neutralized with quicklime, decontaminated and baked to stimulate its cementitious properties, and then mixed with mineral powder and steel sand in the ratio of 5∶4∶1 to form modified solid waste phosphogypsum mix (MWPM) to replace part of the cement as an auxiliary cementitious material. At the same time, solid waste phosphogypsum aggregate was used to replace part of the natural fine aggregate, while a small amount of polyoxymethylene (POM) fibers and wood pulp fibers were considered to be incorporated to carry out a baseline proportion design study of fiber-reinforced cementitious composites and to analyses their strength and micro-mechanisms in combination with XRD and SEM. The results show that the dosage of MWPM with phosphogypsum aggregate has almost no effect on the density, water absorption, thermal conductivity, etc. of solid waste fiber-reinforced cement boards; Although the strength in the early stage decreases slightly with the increase in the dosage of MWPM, it can still be maintained at about 4 MPa when the dosage reaches about 18%, and the strength in the later stage is partially enhanced compared to that of MWPM, while the ratio of flexural strength is not less than 70% after freeze-thaw test, which meets the specification requirements of non-load-bearing fiber reinforced cement board. Phosphogypsum aggregates have a minor reinforcing effect on the composites, which is relatively optimal at 20%; Based on the above research, a benchmark mix ratio for fiber-reinforced cement-based composite materials incorporating phosphogypsum waste has been proposed. This mix ratio effectively utilizes phosphogypsum waste at 155.39 kg/m³, reduces cement consumption by 78.58 kg/m³, and lowers carbon dioxide emissions by 27.60 kg/m³. Microscopic analysis reveals that dihydrate phosphogypsum, ettringite, and C-S-H gel interpenetrate to form a three-dimensional spatial structure. Additionally, the incorporation of POM fibers and wood pulp fibers enhances the integration of the matrix, aggregates, and the two types of fibers, creating a denser overall structure. This structure further improves the mechanical performance of the specimens. The fiber-reinforced cement-based composite material with mixed phosphogypsum waste demonstrates excellent mechanical properties and waste utilization efficiency, providing a reference for the development of non-load-bearing green insulation materials.
2024,
41(9):
5083-5097.
doi: 10.13801/j.cnki.fhclxb.20240805.002
Abstract:
To economically, effectively and reasonably apply engineered cementitious composites (ECC) on improving the mechanical properties of reinforced concrete (RC) column, a novel composite column consisting of precast concrete core and precast steel reinforced ECC shell (SECC-PC composite column) was developed in this paper. SECC-PC composite column specimens as well as the contrast pure RC column and pure ECC column specimens were designed and manufactured. The axial compression tests were conducted to investigate the axial compression behaviours of the specimens. And the influence law of ECC shell thickness and stirrup spacing on the axial compression behaviours of the specimens was systematically analyzed. Based on this, the calculation equation of axial compressive bearing capacity of the composite columns considering the additional confinement effect of the stirrup and ECC shell was established. The results show that, compared with the RC column, the SECC-PC composite columns and ECC column exhibit obvious ductile failure characteristic, and no ECC spalling and no segregation phenomena between the precast ECC shell and concrete core occur at failure state. With the ECC shell thickness increasing, the peak load and displacement of the precast composite columns increase, while the relevant initial stiffness and ductility coefficient decrease. The incorporation of the precast ECC shell can significantly improve the ductility and energy dissipation capacity of the specimens. Within the designed ECC shell thickness in this study, the ductility coefficients and the accumulated energy dissipation of the precast composite columns are 1.13-1.35 times and 2.13-2.46 times larger than that of the RC column. With the stirrup spacing decreasing, the bearing capacity improves, while the post-peak ductility and energy dissipation capacity of the specimens improve remarkably. The axial compressive bearing capacity of the composite column should take the constraint effect of the prefabricated ECC shell into account. The relevant bearing capacity calculation equation can be used to calculate the axial compressive bearing capacity of the composite column.
To economically, effectively and reasonably apply engineered cementitious composites (ECC) on improving the mechanical properties of reinforced concrete (RC) column, a novel composite column consisting of precast concrete core and precast steel reinforced ECC shell (SECC-PC composite column) was developed in this paper. SECC-PC composite column specimens as well as the contrast pure RC column and pure ECC column specimens were designed and manufactured. The axial compression tests were conducted to investigate the axial compression behaviours of the specimens. And the influence law of ECC shell thickness and stirrup spacing on the axial compression behaviours of the specimens was systematically analyzed. Based on this, the calculation equation of axial compressive bearing capacity of the composite columns considering the additional confinement effect of the stirrup and ECC shell was established. The results show that, compared with the RC column, the SECC-PC composite columns and ECC column exhibit obvious ductile failure characteristic, and no ECC spalling and no segregation phenomena between the precast ECC shell and concrete core occur at failure state. With the ECC shell thickness increasing, the peak load and displacement of the precast composite columns increase, while the relevant initial stiffness and ductility coefficient decrease. The incorporation of the precast ECC shell can significantly improve the ductility and energy dissipation capacity of the specimens. Within the designed ECC shell thickness in this study, the ductility coefficients and the accumulated energy dissipation of the precast composite columns are 1.13-1.35 times and 2.13-2.46 times larger than that of the RC column. With the stirrup spacing decreasing, the bearing capacity improves, while the post-peak ductility and energy dissipation capacity of the specimens improve remarkably. The axial compressive bearing capacity of the composite column should take the constraint effect of the prefabricated ECC shell into account. The relevant bearing capacity calculation equation can be used to calculate the axial compressive bearing capacity of the composite column.
Crucial parameters and influence rules of axial crushing energy absorption of CFRP-Al hybrid columns
2024,
41(9):
5098-5109.
doi: 10.13801/j.cnki.fhclxb.20240809.001
Abstract:
To investigate the failure behavior and energy absorption characteristics of carbon fiber reinforced polymer (CFRP)-aluminum alloy (Al) open-section hybrid columns under axial load, the combination of quasi-static crushing test and finite element method were employed to analyze the effects of different crucial parameters on axial crushing failure behavior and energy absorption characteristics of CFRP-Al hybrid columns. The results show that the Al model with single-layer shell adopted the elastic-plastic constitutive and GISSMO damage model, as well as the CFRP model with laminated shell adopted the Chang-Chang intralaminar failure criterion and the B-K interlaminar damage model can accurately simulate the axial crushing failure behavior and energy absorption characteristics of CFRP-Al hybrid columns. Through the analysis of crucial parameters such as relative thickness ratio, fillet ratio, opening angle, gradient and induced hole, the specific energy absorption of CFRP-Al hybrid columns reaches a higher level with the relative thickness ratio η=67%, fillet ratio γ=50%, opening angle θ=120°, gradient T=8, and induced hole K=1. By coupling the optimal values of the crucial parameters, the axial crushing energy absorption of the CFRP-Al hybrid column increases by 46.81%, and the specific energy absorption increases by 49.06%.
To investigate the failure behavior and energy absorption characteristics of carbon fiber reinforced polymer (CFRP)-aluminum alloy (Al) open-section hybrid columns under axial load, the combination of quasi-static crushing test and finite element method were employed to analyze the effects of different crucial parameters on axial crushing failure behavior and energy absorption characteristics of CFRP-Al hybrid columns. The results show that the Al model with single-layer shell adopted the elastic-plastic constitutive and GISSMO damage model, as well as the CFRP model with laminated shell adopted the Chang-Chang intralaminar failure criterion and the B-K interlaminar damage model can accurately simulate the axial crushing failure behavior and energy absorption characteristics of CFRP-Al hybrid columns. Through the analysis of crucial parameters such as relative thickness ratio, fillet ratio, opening angle, gradient and induced hole, the specific energy absorption of CFRP-Al hybrid columns reaches a higher level with the relative thickness ratio η=67%, fillet ratio γ=50%, opening angle θ=120°, gradient T=8, and induced hole K=1. By coupling the optimal values of the crucial parameters, the axial crushing energy absorption of the CFRP-Al hybrid column increases by 46.81%, and the specific energy absorption increases by 49.06%.
2024,
41(9):
5110-5124.
doi: 10.13801/j.cnki.fhclxb.20240307.003
Abstract:
To study the axial compression damage performance and failure mechanism of wood columns strengthened with carbon fiber reinforced polymer (CFRP), axial compression tests and real-time acoustic emission (AE) monitoring were carried out on six groups of wood columns with different CFRP winding methods. The effects of different winding layers and winding angle on the damage forms, mechanical properties, energy absorption properties and acoustic emission parameters of CFRP-reinforced wood columns were analyzed. The results show that: The reinforcement of CFRP can significantly improve the mechanical properties of wood, inhibit the occurrence of brittle damage; With the increase of the winding layers and angle, the ultimate bearing capacity of the wood columns increases from 112.63 kN to 161.21 kN, and the displacement ductility factor also increases from 1.44 to 1.72; The increase of CFRP winding layers and angle can significantly improve the stability and energy absorption capacity of CFRP-reinforced wood columns in the axial compression damage process; According to the evolution characteristics of acoustic emission ringing count, the damage process of CFRP-reinforced wood columns can be divided into three stages: Elastic stage, compressive yield stage and damage failure stage; With the increase of the winding layers and angle, the peak frequency of acoustic emission gradually transitions from the low-frequency range (0-80 kHz) to the high-frequency range (160-240 kHz), and the damage form changes from large-scale damage to small-scale damage; The probability density of acoustic emission energy of wood columns with different winding methods follows a power-law scale-free distribution, the critical indices under six reinforcement methods are 1.31, 1.33, 1.36, 1.43, 1.49 and 1.57, respectively; The critical index increases with the increase of winding layers and angles, the reinforcement of CFRP limits the development of internal cracks and weakens the deterioration of the internal structure of the wood.
To study the axial compression damage performance and failure mechanism of wood columns strengthened with carbon fiber reinforced polymer (CFRP), axial compression tests and real-time acoustic emission (AE) monitoring were carried out on six groups of wood columns with different CFRP winding methods. The effects of different winding layers and winding angle on the damage forms, mechanical properties, energy absorption properties and acoustic emission parameters of CFRP-reinforced wood columns were analyzed. The results show that: The reinforcement of CFRP can significantly improve the mechanical properties of wood, inhibit the occurrence of brittle damage; With the increase of the winding layers and angle, the ultimate bearing capacity of the wood columns increases from 112.63 kN to 161.21 kN, and the displacement ductility factor also increases from 1.44 to 1.72; The increase of CFRP winding layers and angle can significantly improve the stability and energy absorption capacity of CFRP-reinforced wood columns in the axial compression damage process; According to the evolution characteristics of acoustic emission ringing count, the damage process of CFRP-reinforced wood columns can be divided into three stages: Elastic stage, compressive yield stage and damage failure stage; With the increase of the winding layers and angle, the peak frequency of acoustic emission gradually transitions from the low-frequency range (0-80 kHz) to the high-frequency range (160-240 kHz), and the damage form changes from large-scale damage to small-scale damage; The probability density of acoustic emission energy of wood columns with different winding methods follows a power-law scale-free distribution, the critical indices under six reinforcement methods are 1.31, 1.33, 1.36, 1.43, 1.49 and 1.57, respectively; The critical index increases with the increase of winding layers and angles, the reinforcement of CFRP limits the development of internal cracks and weakens the deterioration of the internal structure of the wood.
