Pub Date : 2024-09-22DOI: 10.1016/j.compstruct.2024.118606
In this study, an electrode wrapped in a carbon network is fabricated using a straightforward hydrothermal technique. Conducting polymers such as polyaniline (PANi) have been used to form carbon networks on the surfaces of carbon fibers. However, the cycling instability of PANi, which is a consequence of structural modifications, is a significant obstacle to its commercial application. This study presents an innovative and effective approach for synthesizing carbon networks using PANi/reduced graphene oxide (PANi-rGO-CF) composites to enhance the performance of vanadium redox flow battery (VRFB) electrodes. PANi-rGO was deposited on carbon felt using a hydrothermal method, followed by calcination under an argon atmosphere. The presence of graphene oxide facilitated the uniform distribution of PANi and enhanced its stability. PANi-rGO-CF demonstrated superior electrocatalysis toward vanadium redox couples owing to the abundant heteroatom active sites, affording VRFBs with extraordinary stability and outstanding energy efficiency after 100 cycles at 100 mA/cm2.
{"title":"High-performance composite electrode based on polyaniline/graphene oxide carbon network for vanadium redox flow batteries","authors":"","doi":"10.1016/j.compstruct.2024.118606","DOIUrl":"10.1016/j.compstruct.2024.118606","url":null,"abstract":"<div><div>In this study, an electrode wrapped in a carbon network is fabricated using a straightforward hydrothermal technique. Conducting polymers such as polyaniline (PANi) have been used to form carbon networks on the surfaces of carbon fibers. However, the cycling instability of PANi, which is a consequence of structural modifications, is a significant obstacle to its commercial application. This study presents an innovative and effective approach for synthesizing carbon networks using PANi/reduced graphene oxide (PANi-rGO-CF) composites to enhance the performance of vanadium redox flow battery (VRFB) electrodes. PANi-rGO was deposited on carbon felt using a hydrothermal method, followed by calcination under an argon atmosphere. The presence of graphene oxide facilitated the uniform distribution of PANi and enhanced its stability. PANi-rGO-CF demonstrated superior electrocatalysis toward vanadium redox couples owing to the abundant heteroatom active sites, affording VRFBs with extraordinary stability and outstanding energy efficiency after 100 cycles at 100 mA/cm<sup>2</sup>.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142327014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-22DOI: 10.1016/j.compstruct.2024.118609
Ring stiffeners improve the buckling resistance of thin-walled hulls. In this study, theoretical models of buckling and strength failure of ring-stiffened composite hulls (RSCHs) were used to determine the design parameters. The hulls were prepared by filament winding on a mould composed of multi-petal-combined foams and steel shafts. The experimental results showed that the hydrostatic bearing performance of RSCHs was 1.79 times that of an unstiffened composite hull (USCH) with the same weight-to-displacement ratio (WDR). The crack in the damaged stiffened hulls penetrated the entire axis and expanded circumferentially, resulting in a stiffener fracture. Imperfections related to thickness deviations were introduced into a nonlinear buckling model by considering progressive damage. In contrast to the failure mechanism of USCH, the failure pressure of RSCHs was not at the peak of nonlinear buckling, and fibre compressive failure at 90° on the outermost layer of the skin was dominant. The error between simulated and experimental results was 4.64 %. The parameter analysis indicated that the stiffener height and width had different effects on the buckling load. However, when only the same type of strength failure occurred, both were independent of the load. This study demonstrated the load-bearing advantages of RSCHs for ocean engineering applications.
{"title":"Mechanical properties and failure analysis of ring-stiffened composite hulls under hydrostatic pressure","authors":"","doi":"10.1016/j.compstruct.2024.118609","DOIUrl":"10.1016/j.compstruct.2024.118609","url":null,"abstract":"<div><div>Ring stiffeners improve the buckling resistance of thin-walled hulls. In this study, theoretical models of buckling and strength failure of ring-stiffened composite hulls (RSCHs) were used to determine the design parameters. The hulls were prepared by filament winding on a mould composed of multi-petal-combined foams and steel shafts. The experimental results showed that the hydrostatic bearing performance of RSCHs was 1.79 times that of an unstiffened composite hull (USCH) with the same weight-to-displacement ratio (<em>WDR</em>). The crack in the damaged stiffened hulls penetrated the entire axis and expanded circumferentially, resulting in a stiffener fracture. Imperfections related to thickness deviations were introduced into a nonlinear buckling model by considering progressive damage. In contrast to the failure mechanism of USCH, the failure pressure of RSCHs was not at the peak of nonlinear buckling, and fibre compressive failure at 90° on the outermost layer of the skin was dominant. The error between simulated and experimental results was 4.64 %. The parameter analysis indicated that the stiffener height and width had different effects on the buckling load. However, when only the same type of strength failure occurred, both were independent of the load. This study demonstrated the load-bearing advantages of RSCHs for ocean engineering applications.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323125","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118596
A new method to identify causes of fracture in composites based on acoustic emission (AE) and clusterization of AE data based on reference datasets is presented within the manuscript. Acoustic Emission (AE) is a widely used non-destructive method for fracture analysis, but data due to their multidimensionality are not easy to analyze especially if the acoustic events appear simultaneously and have similar parameters even if they are an effect of different failure mechanisms. In this research, we utilize an unsupervised learning algorithm besides the simplest K-means, through fuzzy c-means to Gaussian Mixture Model (GMM) and spectral clustering to investigate the dataset obtained from the three-point bending test manufactured by us composite. The analysis is preceded by data curation, feature determination (Laplacian score) and the best number of cluster investigations (DB index, Caliński-Harabasz score, and Silhouette method) To enable interpretation of the clustering we run an additional three groups of tests covering fibre breakage (two methods), resin fracture (in tension and in compression) and delamination (DCB test) creating reference datasets. These datasets were statistically analyzed and kernel density estimators were generated for each AE feature as well as amplitude-frequency characteristics. Clusters obtained for the main dataset were then assigned to particular causes of failure by comparing them with the reference dataset. It was found that clusters generated using spectral clustering were the most realistic ones, as it was possible to assign the cause of failure to them.
{"title":"Damage characterisation of GFRP composites based on clustering acoustic emission events utilizing single-failure-cause tests as reference","authors":"","doi":"10.1016/j.compstruct.2024.118596","DOIUrl":"10.1016/j.compstruct.2024.118596","url":null,"abstract":"<div><div>A new method to identify causes of fracture in composites based on acoustic emission (AE) and clusterization of AE data based on reference datasets is presented within the manuscript. Acoustic Emission (AE) is a widely used non-destructive method for fracture analysis, but data due to their multidimensionality are not easy to analyze especially if the acoustic events appear simultaneously and have similar parameters even if they are an effect of different failure mechanisms. In this research, we utilize an unsupervised learning algorithm besides the simplest K-means, through fuzzy c-means to Gaussian Mixture Model (GMM) and spectral clustering to investigate the dataset obtained from the three-point bending test manufactured by us composite. The analysis is preceded by data curation, feature determination (Laplacian score) and the best number of cluster investigations (DB index, Caliński-Harabasz score, and Silhouette method) To enable interpretation of the clustering we run an additional three groups of tests covering fibre breakage (two methods), resin fracture (in tension and in compression) and delamination (DCB test) creating reference datasets. These datasets were statistically analyzed and kernel density estimators were generated for each AE feature as well as amplitude-frequency characteristics. Clusters obtained for the main dataset were then assigned to particular causes of failure by comparing them with the reference dataset. It was found that clusters generated using spectral clustering were the most realistic ones, as it was possible to assign the cause of failure to them.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118595
The invisible damage caused by low-velocity impacts are safety threats to engineering structures. Thus, impact force identification is crucial in the context of composite structures for both structure health monitoring (SHM) and composite structure design. This paper investigates the process of identifying impacts on composite structures subjected to low-velocity impact. Considering the damage evolution in the composite structure during impact, this paper explores the influence of impact damage on the accuracy of force identification. Impact experiments on carbon fiber reinforced polymer (CFRP) laminates were conducted to obtain impact force peaks and displacement responses. Furthermore, a validated finite element model (FEM) is established for more elaborate analysis on the mechanism. The findings reveal that the structural damage can lead to significant deviations in force identification if the damage is not considered. Finally, a neural network is employed to predict the force history taking impact damage into consideration. This research provides a reference for the composite structures design and health monitoring of engineering structures considering impact damage.
{"title":"Research on the influence of impact damage on force identification for composite material","authors":"","doi":"10.1016/j.compstruct.2024.118595","DOIUrl":"10.1016/j.compstruct.2024.118595","url":null,"abstract":"<div><div>The invisible damage caused by low-velocity impacts are safety threats to engineering structures. Thus, impact force identification is crucial in the context of composite structures for both structure health monitoring (SHM) and composite structure design. This paper investigates the process of identifying impacts on composite structures subjected to low-velocity impact. Considering the damage evolution in the composite structure during impact, this paper explores the influence of impact damage on the accuracy of force identification. Impact experiments on carbon fiber reinforced polymer (CFRP) laminates were conducted to obtain impact force peaks and displacement responses. Furthermore, a validated finite element model (FEM) is established for more elaborate analysis on the mechanism. The findings reveal that the structural damage can lead to significant deviations in force identification if the damage is not considered. Finally, a neural network is employed to predict the force history taking impact damage into consideration. This research provides a reference for the composite structures design and health monitoring of engineering structures considering impact damage.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323126","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118579
Laminates allow tailoring the fiber orientations in the layers to obtain the desired mechanical response. The optimal layup design is a challenging task in the case of finite deformations and buckling. For an assigned design, an incremental-iterative finite element analysis is needed to compute the structural response. Gradient-based methods are very often the most efficient optimization tools. Their bottleneck is the gradient evaluation, generally possible only approximately by finite differences. This article shows how to compute the exact gradient of the geometrically nonlinear finite element solution with respect to the stacking sequence. The strategy relies on the implicit differentiation of the nonlinear discrete equations of a control equilibrium point corresponding to an assigned displacement. This provides the load factor gradient by a single fast-solution linear system with the already factorized tangent stiffness matrix, regardless of the number of design variables, and scalar products involving the partial derivatives of the discrete internal force vector, calculated in an exact and efficient way. Several applications demonstrate the efficiency and robustness of the approach.
{"title":"Optimal lamination angles via exact and efficient differentiation of the geometrically nonlinear finite element solution","authors":"","doi":"10.1016/j.compstruct.2024.118579","DOIUrl":"10.1016/j.compstruct.2024.118579","url":null,"abstract":"<div><div>Laminates allow tailoring the fiber orientations in the layers to obtain the desired mechanical response. The optimal layup design is a challenging task in the case of finite deformations and buckling. For an assigned design, an incremental-iterative finite element analysis is needed to compute the structural response. Gradient-based methods are very often the most efficient optimization tools. Their bottleneck is the gradient evaluation, generally possible only approximately by finite differences. This article shows how to compute the exact gradient of the geometrically nonlinear finite element solution with respect to the stacking sequence. The strategy relies on the implicit differentiation of the nonlinear discrete equations of a control equilibrium point corresponding to an assigned displacement. This provides the load factor gradient by a single fast-solution linear system with the already factorized tangent stiffness matrix, regardless of the number of design variables, and scalar products involving the partial derivatives of the discrete internal force vector, calculated in an exact and efficient way. Several applications demonstrate the efficiency and robustness of the approach.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118597
Bio-inspired hierarchical discontinuous fibrous composite materials are investigated with the aim of achieving enhanced pseudo-ductility and elevated toughness. A novel methodology is proposed to search quickly and efficiently through the vast design space of the geometrical parameters of the discontinuities, combining advanced numerical simulations of the material’s mechanical behavior with state-of-the-art Machine Learning approaches, such as Active Learning. A continuum mesoscale-based numerical model is developed to simulate the mechanical behavior of discontinuous composites under three-point bending loading and is utilized in a sequential Bayesian optimization scheme that iteratively searches for the material architecture that maximizes toughness. Five independent geometrical variables related to the size and exact topology of the discontinuities form a vast five-dimensional design space of more than 2.6 million possible combinations. In this space, the proposed methodology efficiently identifies, after 100 iterations, a remarkable optimal configuration that increases the material’s toughness by more than 100%, with a knock-down effect on the ultimate bending strength of only 10%.
{"title":"Bio-inspired discontinuous composite materials with a machine learning optimized architecture","authors":"","doi":"10.1016/j.compstruct.2024.118597","DOIUrl":"10.1016/j.compstruct.2024.118597","url":null,"abstract":"<div><div>Bio-inspired hierarchical discontinuous fibrous composite materials are investigated with the aim of achieving enhanced pseudo-ductility and elevated toughness. A novel methodology is proposed to search quickly and efficiently through the vast design space of the geometrical parameters of the discontinuities, combining advanced numerical simulations of the material’s mechanical behavior with state-of-the-art Machine Learning approaches, such as Active Learning. A continuum mesoscale-based numerical model is developed to simulate the mechanical behavior of discontinuous composites under three-point bending loading and is utilized in a sequential Bayesian optimization scheme that iteratively searches for the material architecture that maximizes toughness. Five independent geometrical variables related to the size and exact topology of the discontinuities form a vast five-dimensional design space of more than 2.6 million possible combinations. In this space, the proposed methodology efficiently identifies, after 100 iterations, a remarkable optimal configuration that increases the material’s toughness by more than 100%, with a knock-down effect on the ultimate bending strength of only 10%.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0263822324007256/pdfft?md5=34dfb53e7afc868f36092a059bf5235c&pid=1-s2.0-S0263822324007256-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118608
The aim of this work is to demonstrate that simultaneous electrical resistance (ER) and acoustic emission (AE) techniques are a viable complementary procedures for in-situ mode I delamination monitoring of glass fiber/epoxy composite laminates containing multiwall carbon nanotubes (MWCNTs). The incorporation of MWCNTs was made by the spray-coating technique and composite laminates were manufactured by means of VARI process. The manufactured laminates were cut into double cantilever beam (DCB) specimens for fracture testing and simultaneous ER and AE measurements were carried out under mode I fracture loading condition. The results showed that the ER signal of the DCB specimens follows the load–displacement (P-δ) curve from initiation to growth of delamination failure, confirming the electrical self-sensing capability of the embedded MWCNT electrical network into the laminate. The correlation of AE events with the P-δ curves of the laminates with and without MWCNTs also allowed to detect the mode I delamination initiation and propagation. Although both the ER and AE techniques demonstrated their capability to determine mode I interlaminar fracture toughness and are in agreement with the results of ASTM standard, the presence of MWCNTs into laminates for self-sensing was more favorable since provided mechanical, electrical and sensing capabilities for SHM applications.
这项工作的目的是证明同时使用电阻（ER）和声发射（AE）技术是对含有多壁碳纳米管（MWCNTs）的玻璃纤维/环氧复合材料层压板进行原位模式 I 分层监测的可行补充程序。采用喷涂技术加入多壁碳纳米管，并通过 VARI 工艺制造复合层压板。将制成的层压板切割成双悬臂梁（DCB）试样进行断裂测试，并在模式 I 断裂加载条件下同时进行了 ER 和 AE 测量。结果表明，DCB 试样的 ER 信号与分层破坏从开始到发展的载荷-位移（P-δ）曲线一致，这证实了嵌入层压板的 MWCNT 电网的电自感能力。有无 MWCNT 的层压板的 AE 事件与 P-δ 曲线的相关性也有助于检测模式 I 分层的起始和扩展。虽然 ER 和 AE 技术都证明了其确定模式 I 层间断裂韧性的能力，并且与 ASTM 标准的结果一致，但在层压板中加入 MWCNT 进行自传感更为有利，因为它为 SHM 应用提供了机械、电气和传感能力。
{"title":"Mode I delamination monitoring in carbon nanotubes-glass fiber/epoxy composites using simultaneous electrical self-sensing and acoustic emission techniques","authors":"","doi":"10.1016/j.compstruct.2024.118608","DOIUrl":"10.1016/j.compstruct.2024.118608","url":null,"abstract":"<div><div>The aim of this work is to demonstrate that simultaneous electrical resistance (ER) and acoustic emission (AE) techniques are a viable complementary procedures for in-situ mode I delamination monitoring of glass fiber/epoxy composite laminates containing multiwall carbon nanotubes (MWCNTs). The incorporation of MWCNTs was made by the spray-coating technique and composite laminates were manufactured by means of VARI process. The manufactured laminates were cut into double cantilever beam (DCB) specimens for fracture testing and simultaneous ER and AE measurements were carried out under mode I fracture loading condition. The results showed that the ER signal of the DCB specimens follows the load–displacement (P-δ) curve from initiation to growth of delamination failure, confirming the electrical self-sensing capability of the embedded MWCNT electrical network into the laminate. The correlation of AE events with the P-δ curves of the laminates with and without MWCNTs also allowed to detect the mode I delamination initiation and propagation. Although both the ER and AE techniques demonstrated their capability to determine mode I interlaminar fracture toughness and are in agreement with the results of ASTM standard, the presence of MWCNTs into laminates for self-sensing was more favorable since provided mechanical, electrical and sensing capabilities for SHM applications.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0263822324007360/pdfft?md5=c6aec74e4fa5f5631c4dd0e6168abbed&pid=1-s2.0-S0263822324007360-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142312103","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118574
Structural integrity is commonly defined by strength and durability of structure’s components. Adhesive joints have advantages over welding and bolted joints by less stress concentration, less weight and easier in manufacturing. In this study, numerical modelling analysis is employed to better understand fracture progression and its mechanism in adhesively bonded joints (lap shear joints) subjected to axial loading. Finite element method and discrete element method were used to predict strength and damage propagation of single lap joints. The study utilized Loctite EA 9497 epoxy as adhesive and three different adherends including polyphtalamide–polyphtalamide (PPA–PPA), aluminium–aluminium (AL–AL) and aluminium–polyphtalamide (AL–PPA) in the lap shear joints. The finite element model employed Cohesive Zone Model to examine joint strength, stress distributions along adhesive/adherend interface, and to perform scalar stiffness degradation analysis. The finite element model revealed that the adhesive damage takes place at the interface adjacent to the adherend with lower material stiffness. In addition, validation using load–displacement curves and comparison with experimental data demonstrated good agreement. Subsequently, discrete element model coupled with the Johnson–Kendall–Roberts (JKR) cohesion model was employed to adapted failure progression based on discrete particle interactions. The developed model was verified and compared with experimental results. Using the innovative discrete element method coupled with the JKR cohesion model, the bond number per particle parameter served as a material failure indicator. Analysis from the discrete element approach revealed that failure consistently takes place at the adhesive/adherend interface, irrespective of the adherend type. These study findings provide insights into investigating failure mechanisms in adhesively bonded joints at both macro- and micro-scales.
结构完整性通常是指结构部件的强度和耐用性。与焊接和螺栓连接相比，粘合连接具有应力集中小、重量轻和易于制造等优点。本研究采用了数值建模分析方法，以更好地了解承受轴向载荷的粘接接头（搭接剪切接头）的断裂进展及其机理。研究采用有限元法和离散元法来预测单搭接接头的强度和损伤扩展。研究使用乐泰 EA 9497 环氧树脂作为粘合剂，并在搭接剪切接头中使用了三种不同的粘合剂，包括聚酞胺-聚酞胺 (PPA-PPA)、铝-铝 (AL-AL) 和铝-聚酞胺 (AL-PPA)。有限元模型采用粘合区模型来检验接头强度、沿粘合剂/外胶界面的应力分布，并进行标量刚度退化分析。有限元模型显示，粘合剂损坏发生在材料刚度较低的毗邻粘合剂的界面上。此外，利用载荷-位移曲线进行验证，并与实验数据进行比较，结果表明两者吻合良好。随后，离散元素模型与约翰逊-肯德尔-罗伯茨（Johnson-Kendall-Roberts，JKR）内聚力模型相结合，在离散粒子相互作用的基础上对破坏进程进行了调整。开发的模型与实验结果进行了验证和比较。利用创新的离散元素方法和 JKR 内聚力模型，每个颗粒的结合数参数可作为材料失效指标。离散元素方法的分析表明，无论粘合剂类型如何，失效始终发生在粘合剂/粘合剂界面。这些研究结果为研究宏观和微观尺度上粘合剂粘接接头的失效机制提供了启示。
{"title":"Failure mechanism investigation of the adhesively bonded joints using Finite Element and Discrete Element methods","authors":"","doi":"10.1016/j.compstruct.2024.118574","DOIUrl":"10.1016/j.compstruct.2024.118574","url":null,"abstract":"<div><div>Structural integrity is commonly defined by strength and durability of structure’s components. Adhesive joints have advantages over welding and bolted joints by less stress concentration, less weight and easier in manufacturing. In this study, numerical modelling analysis is employed to better understand fracture progression and its mechanism in adhesively bonded joints (lap shear joints) subjected to axial loading. Finite element method and discrete element method were used to predict strength and damage propagation of single lap joints. The study utilized Loctite EA 9497 epoxy as adhesive and three different adherends including polyphtalamide–polyphtalamide (PPA–PPA), aluminium–aluminium (AL–AL) and aluminium–polyphtalamide (AL–PPA) in the lap shear joints. The finite element model employed Cohesive Zone Model to examine joint strength, stress distributions along adhesive/adherend interface, and to perform scalar stiffness degradation analysis. The finite element model revealed that the adhesive damage takes place at the interface adjacent to the adherend with lower material stiffness. In addition, validation using load–displacement curves and comparison with experimental data demonstrated good agreement. Subsequently, discrete element model coupled with the Johnson–Kendall–Roberts (JKR) cohesion model was employed to adapted failure progression based on discrete particle interactions. The developed model was verified and compared with experimental results. Using the innovative discrete element method coupled with the JKR cohesion model, the bond number per particle parameter served as a material failure indicator. Analysis from the discrete element approach revealed that failure consistently takes place at the adhesive/adherend interface, irrespective of the adherend type. These study findings provide insights into investigating failure mechanisms in adhesively bonded joints at both macro- and micro-scales.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142323123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-21DOI: 10.1016/j.compstruct.2024.118603
Ply-drop (PD) is the termination of specific plies for laminated composite structures to obtain continuous thickness changes. It brings flexibility to the design of tapered composite laminates. However, as a structural defect, ply drops could have an impact on performance. Considering the impact of ply drop during stacking sequence design can provide more accurate performance analysis, but this will bring challenges in modeling and optimization. To consider the PD impact and achieve convenience in optimization, this paper proposes a high-fidelity finite element automatic modelling method of tapered laminates and corresponding optimization framework. By parameterizing the PD information and defining the basic elements and nodes of start stacking surface of the structure, the entire finite element model is layer-wisely constructed and controllable. Subsequently, based on the genetic algorithm framework, a repair strategy and its genetic operations are proposed to ensure that the design variables satisfy the ply-drop design guidelines. And a detailed optimization process is provided. Finally, the strength and deflection performance optimization problem of a tapered laminate with PD from 28 layers to 16 layers under three-point bending test is introduced for illustration of the proposed automatic modeling and optimization method. Comparisons between simulation results and experimental data of the obtained optimization solution verify the effectiveness of the proposed modeling and optimization method.
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Pub Date : 2024-09-20DOI: 10.1016/j.compstruct.2024.118599
Currently, dead zones and low sensitivity have hindered the utilization of magnetostrictive sensors. In this paper, a new negative Poisson’s ratio structure inspired by an hourglass is proposed to provide a feasible idea for this problem. The novel negative Poisson’s ratio structure exhibits a high Poisson’s ratio and a high compression resistance. Theoretical studies have demonstrated that the structure’s performance is strongly dependent on four design parameters. The structure is analyzed and tested via finite element analysis simulation by changing the design parameters. This structure’s negative Poisson’s ratio can reach up to −1.004. It possesses a compressive strength of 1.83 kN and an energy absorption capacity of 8.72 J. A magnetostrictive sensor using the proposed negative Poisson’s ratio structure as the base realizes a 271.7 % sensitivity improvement. The problem of dead zones in magnetostrictive sensors can be also solved simultaneously. The proposed structure in this paper provides a feasible solution for further expanding the applications of magnetostrictive sensors.
{"title":"A novel negative Poisson’s ratio structure with high Poisson’s ratio and high compression resistance and its application in magnetostrictive sensors","authors":"","doi":"10.1016/j.compstruct.2024.118599","DOIUrl":"10.1016/j.compstruct.2024.118599","url":null,"abstract":"<div><div>Currently, dead zones and low sensitivity have hindered the utilization of magnetostrictive sensors. In this paper, a new negative Poisson’s ratio structure inspired by an hourglass is proposed to provide a feasible idea for this problem. The novel negative Poisson’s ratio structure exhibits a high Poisson’s ratio and a high compression resistance. Theoretical studies have demonstrated that the structure’s performance is strongly dependent on four design parameters. The structure is analyzed and tested via finite element analysis simulation by changing the design parameters. This structure’s negative Poisson’s ratio can reach up to −1.004. It possesses a compressive strength of 1.83 kN and an energy absorption capacity of 8.72 J. A magnetostrictive sensor using the proposed negative Poisson’s ratio structure as the base realizes a 271.7 % sensitivity improvement. The problem of dead zones in magnetostrictive sensors can be also solved simultaneously. The proposed structure in this paper provides a feasible solution for further expanding the applications of magnetostrictive sensors.</div></div>","PeriodicalId":281,"journal":{"name":"Composite Structures","volume":null,"pages":null},"PeriodicalIF":6.3,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S026382232400727X/pdfft?md5=ff6725b162a03136c3858ecc050d681e&pid=1-s2.0-S026382232400727X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142314334","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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