Pub Date : 2025-01-21DOI: 10.1177/10567895241313243
Qiuping Li, Jie Liu, Hao Wang
To effectively prevent dynamic gas disasters, the adding vertical and unloading radial stress were investigated in laboratory and numerical simulation experiments. The objective about the research was to ascertain how various gas pressures and loading rates affected permeability and damage deformation. The results conclude that shear failure predominates in gassy coal, a rise in loading rate causes the permeability to mutate more slowly, and the plastic strain gradually decreases at the yield, peak, and post-peak stable points in gassy coal. As well, a rise in gas pressure causes an earlier transition from compression to expansion state of specimens, enhances permeability, and rises the plastic strain at specified points. Furthermore, the study focuses on the meso-scale failure and permeability characteristics. During failure, the seepage channel within the coal body gradually transitions from a vertical orientation to irregular deformation. In addition, a damage model is formulated centered around energy consumption, demonstrating that damage evolution curves exhibit an ‘ S’ shape with vertical strain. Meanwhile, higher axial loading rates delay the onset of unstable crack propagation, but raising gas pressure quickens the pace of damage to specimens. The conclusions of this research hold significant practical implications for mitigating coal-rock gas dynamic disasters.
{"title":"Damage and permeability of gassy coal in loading – Unloading path","authors":"Qiuping Li, Jie Liu, Hao Wang","doi":"10.1177/10567895241313243","DOIUrl":"https://doi.org/10.1177/10567895241313243","url":null,"abstract":"To effectively prevent dynamic gas disasters, the adding vertical and unloading radial stress were investigated in laboratory and numerical simulation experiments. The objective about the research was to ascertain how various gas pressures and loading rates affected permeability and damage deformation. The results conclude that shear failure predominates in gassy coal, a rise in loading rate causes the permeability to mutate more slowly, and the plastic strain gradually decreases at the yield, peak, and post-peak stable points in gassy coal. As well, a rise in gas pressure causes an earlier transition from compression to expansion state of specimens, enhances permeability, and rises the plastic strain at specified points. Furthermore, the study focuses on the meso-scale failure and permeability characteristics. During failure, the seepage channel within the coal body gradually transitions from a vertical orientation to irregular deformation. In addition, a damage model is formulated centered around energy consumption, demonstrating that damage evolution curves exhibit an ‘ S’ shape with vertical strain. Meanwhile, higher axial loading rates delay the onset of unstable crack propagation, but raising gas pressure quickens the pace of damage to specimens. The conclusions of this research hold significant practical implications for mitigating coal-rock gas dynamic disasters.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"46 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142992031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In the highway construction of the southwestern Transverse Mountain area of China, mass mudstone engineering disasters have occurred, primarily attributed to engineering disturbances and water-rock interaction. Engineering disturbances commonly lead to varying degrees of pre-peak damage. To elucidate the evolutionary laws of strength in pre-peak damaged mudstone, we first defined the pre-peak damage variable ( Da) for mudstone, and through triaxial loading and unloading tests, obtained the mechanical characteristics of pre-peak damaged mudstone, analyzing its brittle properties from an energy perspective. Subsequently, through scanning electron microscopy tests, we analyzed the microstructural features to reveal the failure mechanism. Finally, the damage ratio strength theory (DR) was introduced to characterize the strength of the mudstone and validate the suitability of the DR. The results demonstrate that: (1) Mudstone with pre-peak damage exhibits a significant weakening effect due to water-rock interaction, with a maximum reduction in peak strength of approximately 28%. Compared to the loading stress path (LSP), the overall strength of the mudstone is lower under the unloading stress path (ULSP), and the deformation modulus decreases more significantly with Da under the ULSP. (2) Both the Daand confining pressure contribute to a decrease in the brittleness index of the mudstone. Under the ULSP, the mudstone is more prone to brittle failure. (3) The development of micro-cracks in pre-peak damaged mudstone makes it more susceptible to water infiltration, exacerbating the deteriorating effect of water-rock interaction, thus affecting its mechanical properties. (4) The DR can effectively characterize the strength of pre-peak damaged mudstone. The Damage Ratio (ν D,c) of mudstone under the LSP is in the range of 1.07∼1.50, and under the ULSP is in the range of 1.11∼1.52. The ν D,c under the LSP is smaller than under the ULSP, decreases with the Da, and exhibits plastic deformation, indicating that the DR can simultaneously characterize the strength and brittleness of the mudstone. The research results can provide guidance for the design parameters and disaster prevention of disturbed mudstone engineering.
{"title":"Study on mechanical properties and strength criterion of mudstone under loading and unloading considering pre-peak damage","authors":"Hui Qin, Hua Tang, Xiaotao Yin, Xu Cheng, Shengping Tang","doi":"10.1177/10567895241297327","DOIUrl":"https://doi.org/10.1177/10567895241297327","url":null,"abstract":"In the highway construction of the southwestern Transverse Mountain area of China, mass mudstone engineering disasters have occurred, primarily attributed to engineering disturbances and water-rock interaction. Engineering disturbances commonly lead to varying degrees of pre-peak damage. To elucidate the evolutionary laws of strength in pre-peak damaged mudstone, we first defined the pre-peak damage variable ( D<jats:sub>a</jats:sub>) for mudstone, and through triaxial loading and unloading tests, obtained the mechanical characteristics of pre-peak damaged mudstone, analyzing its brittle properties from an energy perspective. Subsequently, through scanning electron microscopy tests, we analyzed the microstructural features to reveal the failure mechanism. Finally, the damage ratio strength theory (DR) was introduced to characterize the strength of the mudstone and validate the suitability of the DR. The results demonstrate that: (1) Mudstone with pre-peak damage exhibits a significant weakening effect due to water-rock interaction, with a maximum reduction in peak strength of approximately 28%. Compared to the loading stress path (LSP), the overall strength of the mudstone is lower under the unloading stress path (ULSP), and the deformation modulus decreases more significantly with D<jats:sub>a</jats:sub> under the ULSP. (2) Both the D<jats:sub>a</jats:sub>and confining pressure contribute to a decrease in the brittleness index of the mudstone. Under the ULSP, the mudstone is more prone to brittle failure. (3) The development of micro-cracks in pre-peak damaged mudstone makes it more susceptible to water infiltration, exacerbating the deteriorating effect of water-rock interaction, thus affecting its mechanical properties. (4) The DR can effectively characterize the strength of pre-peak damaged mudstone. The Damage Ratio (ν <jats:sub>D,c</jats:sub>) of mudstone under the LSP is in the range of 1.07∼1.50, and under the ULSP is in the range of 1.11∼1.52. The ν <jats:sub>D,c</jats:sub> under the LSP is smaller than under the ULSP, decreases with the D<jats:sub>a</jats:sub>, and exhibits plastic deformation, indicating that the DR can simultaneously characterize the strength and brittleness of the mudstone. The research results can provide guidance for the design parameters and disaster prevention of disturbed mudstone engineering.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"12 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142936733","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-01-06DOI: 10.1177/10567895241297301
Feker Mnif, Guesmi Youssef, Rémy Larouche, Hatem Mrad, Sébastien Morin, Robert Poirier, Ahmed Koubaa
In the wood panel industry, metallic contaminants raise significant concerns, especially regarding the press plate's surface integrity, which requires a thorough inspection. This study investigated the effect of metallic contaminants on press plate damage and evaluated the use of infrared thermography (IRT) and infrared (IR) spectroscopy as non-destructive testing (NDT) methods for detecting these contaminants in wood panel manufacturing. Metallic contaminants embedded within lab-scale wood panels demonstrated their impact on the surface quality of both the press plate and the resulting panels. Moreover, confocal laser microscope analysis revealed that the surface roughness of the press plate surface was influenced by the specific alloy composition of contaminants, with steel and chromium contaminants exhibiting the more severe damage (e.g., mean roughness values of 59,80 and 84,64 μm, respectively). Thermography images exhibited the efficacy of IRT in detecting contaminants close to the surface of thin panels. However, an advanced camera is recommended for thicker panels and deeper contaminants to obtain a more accurate inspection. The Fourier-transform infrared spectroscopy (FTIR) evaluation revealed the presence of the metal-oxygen vibration band at approximately 668 cm−1 across all alloy compositions, suggesting its potential as a reliable reference for detecting metallic contaminants.
{"title":"Metallic contaminants in wood panel production process: Evaluating press plate damage and detecting potential using IR thermography and spectroscopy","authors":"Feker Mnif, Guesmi Youssef, Rémy Larouche, Hatem Mrad, Sébastien Morin, Robert Poirier, Ahmed Koubaa","doi":"10.1177/10567895241297301","DOIUrl":"https://doi.org/10.1177/10567895241297301","url":null,"abstract":"In the wood panel industry, metallic contaminants raise significant concerns, especially regarding the press plate's surface integrity, which requires a thorough inspection. This study investigated the effect of metallic contaminants on press plate damage and evaluated the use of infrared thermography (IRT) and infrared (IR) spectroscopy as non-destructive testing (NDT) methods for detecting these contaminants in wood panel manufacturing. Metallic contaminants embedded within lab-scale wood panels demonstrated their impact on the surface quality of both the press plate and the resulting panels. Moreover, confocal laser microscope analysis revealed that the surface roughness of the press plate surface was influenced by the specific alloy composition of contaminants, with steel and chromium contaminants exhibiting the more severe damage (e.g., mean roughness values of 59,80 and 84,64 μm, respectively). Thermography images exhibited the efficacy of IRT in detecting contaminants close to the surface of thin panels. However, an advanced camera is recommended for thicker panels and deeper contaminants to obtain a more accurate inspection. The Fourier-transform infrared spectroscopy (FTIR) evaluation revealed the presence of the metal-oxygen vibration band at approximately 668 cm<jats:sup>−1</jats:sup> across all alloy compositions, suggesting its potential as a reliable reference for detecting metallic contaminants.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"13 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2025-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142935157","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-30DOI: 10.1177/10567895241302543
Yamato Hoshikawa, Kazuki Ryuzono, Sota Onodera, Yoshiaki Kawagoe, Tomonaga Okabe
Fiber-reinforced composites are essential in the aerospace industry, highlighting the need for an in-depth understanding of their durability. This study introduces a novel approach that integrates viscoelasticity and damage evolution based on continuum damage mechanics, employing finite element analysis. The method utilizes an anisotropic viscoelastic constitutive law to examine creep behavior under constant stress, decomposing stresses into equilibrium and non-equilibrium components. Moreover, it integrates a transverse crack damage variable associated with crack density. After solving stiffness equations, a detailed analysis of transverse crack propagation is conducted. This technique was applied to creep tests on carbon fiber-reinforced plastics and 3D woven ceramic matrix composites, resulting in strain and crack density profiles. The numerical simulations successfully reproduced experimental outcomes. The developed method offers a comprehensive tool for analyzing transverse crack propagation under viscoelastic creep conditions through finite element analysis, significantly enhancing design considerations by incorporating aspects of long-term durability.
{"title":"Finite element modeling of viscoelastic creep behavior and transverse cracking in fiber-reinforced composite materials","authors":"Yamato Hoshikawa, Kazuki Ryuzono, Sota Onodera, Yoshiaki Kawagoe, Tomonaga Okabe","doi":"10.1177/10567895241302543","DOIUrl":"https://doi.org/10.1177/10567895241302543","url":null,"abstract":"Fiber-reinforced composites are essential in the aerospace industry, highlighting the need for an in-depth understanding of their durability. This study introduces a novel approach that integrates viscoelasticity and damage evolution based on continuum damage mechanics, employing finite element analysis. The method utilizes an anisotropic viscoelastic constitutive law to examine creep behavior under constant stress, decomposing stresses into equilibrium and non-equilibrium components. Moreover, it integrates a transverse crack damage variable associated with crack density. After solving stiffness equations, a detailed analysis of transverse crack propagation is conducted. This technique was applied to creep tests on carbon fiber-reinforced plastics and 3D woven ceramic matrix composites, resulting in strain and crack density profiles. The numerical simulations successfully reproduced experimental outcomes. The developed method offers a comprehensive tool for analyzing transverse crack propagation under viscoelastic creep conditions through finite element analysis, significantly enhancing design considerations by incorporating aspects of long-term durability.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"35 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142904782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study focused on understanding the fatigue response of anisotropic spherulitic polymers by employing a multiscale microscopic modeling approach. The crystal plasticity model together with the Arruda-Boyce model were used to describe the mechanical response of crystalline phase and amorphous. The fatigue behaviors and crack initiation were captured by Fatemi-Socie multiaxial criterion and continuous damage theory under multiaxial and non-proportional loading conditions. The sheaf-like structure of spherulitic polymers was considered to shed light on the anisotropic nature of fatigue failure. The results highlight the role of features of sheaf structure, e.g., initiation orientation, on the fatigue performance of spherulitic polymers, which have not been reported. The localized degradation of mechanical properties and the accumulation of fatigue damage were systematically discussed with various loading patterns. This study provided an in-depth understanding of potential fatigue mechanisms, offering robust support for fatigue resistance design in engineering applications.
{"title":"Micromechanical analysis of spherulitic polymers in multiaxial and non-proportional fatigue crack nucleation","authors":"Chenxu Jiang, Jia Zhou, Jiaxin Cui, Changqing Miao","doi":"10.1177/10567895241302873","DOIUrl":"https://doi.org/10.1177/10567895241302873","url":null,"abstract":"This study focused on understanding the fatigue response of anisotropic spherulitic polymers by employing a multiscale microscopic modeling approach. The crystal plasticity model together with the Arruda-Boyce model were used to describe the mechanical response of crystalline phase and amorphous. The fatigue behaviors and crack initiation were captured by Fatemi-Socie multiaxial criterion and continuous damage theory under multiaxial and non-proportional loading conditions. The sheaf-like structure of spherulitic polymers was considered to shed light on the anisotropic nature of fatigue failure. The results highlight the role of features of sheaf structure, e.g., initiation orientation, on the fatigue performance of spherulitic polymers, which have not been reported. The localized degradation of mechanical properties and the accumulation of fatigue damage were systematically discussed with various loading patterns. This study provided an in-depth understanding of potential fatigue mechanisms, offering robust support for fatigue resistance design in engineering applications.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"12 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142887747","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents a novel three-phase damage model for the prediction of the post-peak responses of composite materials, such as recycled aggregate concrete (RAC). The proposed damage model is based on composite damage mechanics and is composed of three phases: cement paste, interface transition zone (ITZ), and aggregate. All phases are assumed to be linearly elastic and isotropic materials. The aggregate is supposed to be the undamaged material, while the cement paste and ITZ are considered the damaged materials. Three different composite damage models, namely Voigt (parallel), Reuss (serial), and the proposed generalized self-consistent (spherical), represent the damage growth in the composite materials. The Voigt parallel model is employed to address the upper bound of post-peak stiffness and stress, while the Reuss serial model represents the lower bound. To investigate the softening phenomenon after the post-peak state, both linear and exponential functions are used to describe the stress-strain curve in this state. Two numerical simulations are provided to examine the stress degradation in the softening state. Both simulations reveal that the post-peak stress degrades with increasing damage parameters and ITZ thickness. Therefore, both damage and ITZ’s thickness are significant factors for analyzing the post-peak responses of RAC.
{"title":"Three-phase damage model based on composite mechanics for post-peak analysis of recycled aggregate concrete","authors":"Worathep Sae-Long, Nattapong Damrongwiriyanupap, Suchart Limkatanyu, Yunping Xi, Tanakorn Phoo-ngernkham, Piti Sukontasukkul, Suraparb Keawsawasvong","doi":"10.1177/10567895241303221","DOIUrl":"https://doi.org/10.1177/10567895241303221","url":null,"abstract":"This paper presents a novel three-phase damage model for the prediction of the post-peak responses of composite materials, such as recycled aggregate concrete (RAC). The proposed damage model is based on composite damage mechanics and is composed of three phases: cement paste, interface transition zone (ITZ), and aggregate. All phases are assumed to be linearly elastic and isotropic materials. The aggregate is supposed to be the undamaged material, while the cement paste and ITZ are considered the damaged materials. Three different composite damage models, namely Voigt (parallel), Reuss (serial), and the proposed generalized self-consistent (spherical), represent the damage growth in the composite materials. The Voigt parallel model is employed to address the upper bound of post-peak stiffness and stress, while the Reuss serial model represents the lower bound. To investigate the softening phenomenon after the post-peak state, both linear and exponential functions are used to describe the stress-strain curve in this state. Two numerical simulations are provided to examine the stress degradation in the softening state. Both simulations reveal that the post-peak stress degrades with increasing damage parameters and ITZ thickness. Therefore, both damage and ITZ’s thickness are significant factors for analyzing the post-peak responses of RAC.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"32 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142867093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-09DOI: 10.1177/10567895241303157
Zhibiao Guo, Jingwei Gao, Jinglin You, Dongshan Yang
To comprehensively investigate the influence of water content on the mechanical and crack propagation characteristics of coal rock assemblage (CRA) with a rough interface, uniaxial compression tests were conducted on specimens with varying water content. Nuclear magnetic resonance (NMR) and acoustic emission (AE) techniques were employed to monitor the water content and AE signals throughout the experiment. The physical and mechanical properties, as well as the extent of crack development and acoustic emission (AE) parameters, were comprehensively investigated under conditions of water erosion. The results demonstrate that a rough interface contributes to an enhancement in the compressive strength of the composite material. Moreover, the moisture content exerts a significant influence on various aspects of the composite specimen, including its compressive strength, time b value, crack development, and crack propagation. With the increase in water content, the initial single slope shear failure of the composite specimen gradually transitions into a multi-section shear failure mechanism. Under the influence of water-rock interaction, sandstone within the formation undergoes a metamorphosis from a densely cemented structure to an irregular honeycomb-like configuration. This transformative process engenders novel porosity and fractures, ultimately compromising the rock’s mechanical strength. The analysis focuses on the relationship between the AE parameter b and uniaxial stress and water content, with emphasis on its relevance to damage theory. A damage model based on water immersion rate was established to elucidate the correlation between damage variables and water content. This was achieved by considering the characteristics of water-rock coupling AE and constructing a structural model of the water absorption process in different pore throats, thereby providing valuable insights for stability design and evaluation of roadway rock masses.
{"title":"Influence of water saturation on mechanical characteristics and fracture evolution of coal rock assemblage with rough interfaces","authors":"Zhibiao Guo, Jingwei Gao, Jinglin You, Dongshan Yang","doi":"10.1177/10567895241303157","DOIUrl":"https://doi.org/10.1177/10567895241303157","url":null,"abstract":"To comprehensively investigate the influence of water content on the mechanical and crack propagation characteristics of coal rock assemblage (CRA) with a rough interface, uniaxial compression tests were conducted on specimens with varying water content. Nuclear magnetic resonance (NMR) and acoustic emission (AE) techniques were employed to monitor the water content and AE signals throughout the experiment. The physical and mechanical properties, as well as the extent of crack development and acoustic emission (AE) parameters, were comprehensively investigated under conditions of water erosion. The results demonstrate that a rough interface contributes to an enhancement in the compressive strength of the composite material. Moreover, the moisture content exerts a significant influence on various aspects of the composite specimen, including its compressive strength, time b value, crack development, and crack propagation. With the increase in water content, the initial single slope shear failure of the composite specimen gradually transitions into a multi-section shear failure mechanism. Under the influence of water-rock interaction, sandstone within the formation undergoes a metamorphosis from a densely cemented structure to an irregular honeycomb-like configuration. This transformative process engenders novel porosity and fractures, ultimately compromising the rock’s mechanical strength. The analysis focuses on the relationship between the AE parameter b and uniaxial stress and water content, with emphasis on its relevance to damage theory. A damage model based on water immersion rate was established to elucidate the correlation between damage variables and water content. This was achieved by considering the characteristics of water-rock coupling AE and constructing a structural model of the water absorption process in different pore throats, thereby providing valuable insights for stability design and evaluation of roadway rock masses.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"28 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142797124","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-09DOI: 10.1177/10567895241305324
Alper Gunoz, Memduh Kara
The use of carbon and kevlar fiber-reinforced composite materials continues to grow in high-tech applications such as aerospace engineering. One of the most desired properties in composite structures is a strong interfacial bond between the matrix and the fiber. Nano-material reinforcement is one of the most preferred methods for strengthening the fiber-matrix interfacial bond. In the present research, polyamide 6.6 (PA 6.6) nanofiber and multi-walled carbon nanotubes (MWCNTs) reinforced kevlar fabric (KF), carbon fabric (CF) and epoxy matrix nanocomposite plates were produced by functional grading of these two fabrics. PA 6.6 nanofibers, obtained by electrospinning, were placed between the layers, and 12-layer nanocomposite plates were fabricated using a vacuum-assisted hand lay-up method. In producing MWCNTs reinforced nanocomposite plates, 0.3 wt.% of MWCNTs were added into the epoxy matrix. A comprehensive set of 16 distinct composite plates was manufactured, encompassing unreinforced plates, plates reinforced with MWCNTs, plates reinforced with PA 6.6, and plates reinforced with a combination of PA 6.6 and MWCNTs (PA 6.6-MWCNTs). The impact strengths of the produced composite plates were investigated at energy levels of 20, 40 and 60 J. The effects of reinforcing the composite structure with MWCNTs, PA 6.6, and PA 6.6-MWCNTs, as well as functionally grading KF/CF on impact strength, were investigated in detail. The damages that occurred in the material as a result of the low-velocity impact tests were interpreted by examining the high-resolution camera and optical microscope images. Thus, the nanofiber and nanoparticle reinforcement to composite structure and hybridization effect were evaluated together. With the reinforcement of PA 6.6, MWCNTs and PA 6.6-MWCNTs, the impact strength of the nanocomposite samples increased significantly compared to the unreinforced samples. Moreover, the amount of damage caused by the low-velocity impact test in reinforced samples was significantly reduced.
{"title":"Damage behavior of functionally graded kevlar/carbon epoxy nanocomposites reinforced with polyamide 6.6 nanofiber and MWCNTs subjected to low-velocity impact","authors":"Alper Gunoz, Memduh Kara","doi":"10.1177/10567895241305324","DOIUrl":"https://doi.org/10.1177/10567895241305324","url":null,"abstract":"The use of carbon and kevlar fiber-reinforced composite materials continues to grow in high-tech applications such as aerospace engineering. One of the most desired properties in composite structures is a strong interfacial bond between the matrix and the fiber. Nano-material reinforcement is one of the most preferred methods for strengthening the fiber-matrix interfacial bond. In the present research, polyamide 6.6 (PA 6.6) nanofiber and multi-walled carbon nanotubes (MWCNTs) reinforced kevlar fabric (KF), carbon fabric (CF) and epoxy matrix nanocomposite plates were produced by functional grading of these two fabrics. PA 6.6 nanofibers, obtained by electrospinning, were placed between the layers, and 12-layer nanocomposite plates were fabricated using a vacuum-assisted hand lay-up method. In producing MWCNTs reinforced nanocomposite plates, 0.3 wt.% of MWCNTs were added into the epoxy matrix. A comprehensive set of 16 distinct composite plates was manufactured, encompassing unreinforced plates, plates reinforced with MWCNTs, plates reinforced with PA 6.6, and plates reinforced with a combination of PA 6.6 and MWCNTs (PA 6.6-MWCNTs). The impact strengths of the produced composite plates were investigated at energy levels of 20, 40 and 60 J. The effects of reinforcing the composite structure with MWCNTs, PA 6.6, and PA 6.6-MWCNTs, as well as functionally grading KF/CF on impact strength, were investigated in detail. The damages that occurred in the material as a result of the low-velocity impact tests were interpreted by examining the high-resolution camera and optical microscope images. Thus, the nanofiber and nanoparticle reinforcement to composite structure and hybridization effect were evaluated together. With the reinforcement of PA 6.6, MWCNTs and PA 6.6-MWCNTs, the impact strength of the nanocomposite samples increased significantly compared to the unreinforced samples. Moreover, the amount of damage caused by the low-velocity impact test in reinforced samples was significantly reduced.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"70 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142797125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-12-09DOI: 10.1177/10567895241305596
Yi Luo, Chao Ye, Pengpeng Ni, Zhixing Zeng, Yixian Liu
Many historical earthen buildings are damaged due to fire exposure in the past. It is important to understand the strength degradation of rammed earth after elevated temperature for guiding the strategy of building protection or rehabilitation. A total of 24 unconfined compression tests are conducted on lime-stabilized rammed earth specimens after elevated temperature up to 700°C. A quasi-linear reduction in strength and stiffness is found for rammed earth with the increase of temperature. At high temperature, the ductility of rammed earth is enhanced, e.g., strain at peak strength of 2.5% and 1.5% at 700°C and 20°C, respectively. Microstructural analyses demonstrate that with the increase of temperature, the specimen becomes more porous with reduced calcium carbonate precipitation, explaining the strength reduction. A new thermal damage model is proposed to describe the behavior of rammed earth after elevated temperature, in which the closure of pores is captured to show unrecoverable deformation, and the skeleton part is simulated using a thermal damage variable in a statistical manner to present the damage evolution (strain softening). By comparing with the measured stress-strain curves, one can confirm that the proposed method can provide effective prediction for the response of rammed earth after elevated temperature.
{"title":"Statistical damage model with strain softening for lime-stabilized rammed earth after elevated temperature","authors":"Yi Luo, Chao Ye, Pengpeng Ni, Zhixing Zeng, Yixian Liu","doi":"10.1177/10567895241305596","DOIUrl":"https://doi.org/10.1177/10567895241305596","url":null,"abstract":"Many historical earthen buildings are damaged due to fire exposure in the past. It is important to understand the strength degradation of rammed earth after elevated temperature for guiding the strategy of building protection or rehabilitation. A total of 24 unconfined compression tests are conducted on lime-stabilized rammed earth specimens after elevated temperature up to 700°C. A quasi-linear reduction in strength and stiffness is found for rammed earth with the increase of temperature. At high temperature, the ductility of rammed earth is enhanced, e.g., strain at peak strength of 2.5% and 1.5% at 700°C and 20°C, respectively. Microstructural analyses demonstrate that with the increase of temperature, the specimen becomes more porous with reduced calcium carbonate precipitation, explaining the strength reduction. A new thermal damage model is proposed to describe the behavior of rammed earth after elevated temperature, in which the closure of pores is captured to show unrecoverable deformation, and the skeleton part is simulated using a thermal damage variable in a statistical manner to present the damage evolution (strain softening). By comparing with the measured stress-strain curves, one can confirm that the proposed method can provide effective prediction for the response of rammed earth after elevated temperature.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"83 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142797126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pre-stressed anchor bolts serve as an effective means to reinforce fractured rock masses. The long-term efficacy of their anchoring function significantly impacts the safety throughout the entire lifecycle of rock engineering projects. Over time, fractured rock masses undergo creep deformation, which interacts synergistically with the time-dependent changes in the pre-stress of anchor bolts. In this work, we conduct uniaxial tensile tests and tensile creep tests on fractured rock specimens anchored by pre-stressed bolts, analyzing the coordinated deformation between the pre-stressed anchor bolts and the fractured specimens. Firstly, conventional uniaxial tensile tests were conducted on the pre-stressed anchorage specimen. The study found that the tensile strength of the anchored specimens was significantly higher than that of the unanchored specimens. Additionally, the ability of the specimens to withstand tensile stresses and deformation improved as pre-stress increased. Secondly, uniaxial tensile creep tests were conducted on the prestressed anchored specimens. The results indicate that, as the stress level increases, the creep strain continues to increase. The application of prestress can effectively limit the tensile deformation of the specimen and delay its damage time. The greater the pre-stress, the smaller the instantaneous strain and creep strain rate during the graded loading test. Finally, based on the synergistic deformation of pre-stressed anchor bolts and the creeping rock mass, we establish a constitutive model reflecting the creep properties of fractured rock mass and derive a theoretical viscoelastic creep formula for anchored rock mass under uniaxial tension. Comparing the creep model with the test results shows that this model is highly applicable and accurate in verifying the tensile creep deformation of prestressed anchorage specimens.
{"title":"Investigation into the time-dependent mechanical behavior of pre-stressed anchor bolts and fractured rock specimens under synchronized tensile loads","authors":"Wendong Yang, Chuntian Liu, Yiwe Li, Bingqi Wang, Xiang Zhang","doi":"10.1177/10567895241303164","DOIUrl":"https://doi.org/10.1177/10567895241303164","url":null,"abstract":"Pre-stressed anchor bolts serve as an effective means to reinforce fractured rock masses. The long-term efficacy of their anchoring function significantly impacts the safety throughout the entire lifecycle of rock engineering projects. Over time, fractured rock masses undergo creep deformation, which interacts synergistically with the time-dependent changes in the pre-stress of anchor bolts. In this work, we conduct uniaxial tensile tests and tensile creep tests on fractured rock specimens anchored by pre-stressed bolts, analyzing the coordinated deformation between the pre-stressed anchor bolts and the fractured specimens. Firstly, conventional uniaxial tensile tests were conducted on the pre-stressed anchorage specimen. The study found that the tensile strength of the anchored specimens was significantly higher than that of the unanchored specimens. Additionally, the ability of the specimens to withstand tensile stresses and deformation improved as pre-stress increased. Secondly, uniaxial tensile creep tests were conducted on the prestressed anchored specimens. The results indicate that, as the stress level increases, the creep strain continues to increase. The application of prestress can effectively limit the tensile deformation of the specimen and delay its damage time. The greater the pre-stress, the smaller the instantaneous strain and creep strain rate during the graded loading test. Finally, based on the synergistic deformation of pre-stressed anchor bolts and the creeping rock mass, we establish a constitutive model reflecting the creep properties of fractured rock mass and derive a theoretical viscoelastic creep formula for anchored rock mass under uniaxial tension. Comparing the creep model with the test results shows that this model is highly applicable and accurate in verifying the tensile creep deformation of prestressed anchorage specimens.","PeriodicalId":13837,"journal":{"name":"International Journal of Damage Mechanics","volume":"77 1","pages":""},"PeriodicalIF":4.2,"publicationDate":"2024-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142776461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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