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【新文速递】2024年12月5日复合材料SCI期刊最新文章

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今日更新:Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 4 篇,Composites Science and Technology 2 篇

Composites Part A: Applied Science and Manufacturing

Characterisation of near pure mode II quasi-static and fatigue delamination behaviour of a carbon-glass interface using a pure-moment-loaded DCB test rig

Iñigo Urcelay Oca, Simon Mosbjerg Jensen, Brian Lau Verndal Bak, Fahimeh Shakibapour, Esben Lindgaard

doi:10.1016/j.compositesa.2024.108625

利用纯矩加载DCB试验装置表征碳-玻璃界面的近纯II型准静态和疲劳分层行为

This work covers the characterisation of delamination growth in a carbon-glass interface, representative of the one in a wind turbine blade. A pure-moment-loaded Double Cantilever Beam (DCB) test rig is used under quasi-static and fatigue loading. A new fatigue characterisation procedure is adopted by real-time controlling the prescribed energy release rate G . This procedure enables sweeping any desired G range at a user-defined rate independently of the compliance of the specimen. A finite element simulation using a cohesive zone model confirms the testing was performed at near pure mode II conditions. From the quasi-static tests, the onset and steady-state fracture toughnesses are characterised. Fibre bridging is observed, which is believed to explain the characterised R-curve effect. From the fatigue tests, Paris’ law is characterised in a wide G m a x range in each test. The characterisation of the quasi-static and fatigue fracture behaviour of the carbon-glass interface is thus successfully achieved.

这项工作涵盖了碳-玻璃界面中分层生长的特征,代表了风力涡轮机叶片中的分层生长。采用纯矩加载双悬臂梁(DCB)试验台进行准静态和疲劳载荷试验。通过实时控制规定的能量释放率G,采用了一种新的疲劳表征方法。该程序能够以用户定义的速率扫描任何所需的G范围,而不受试样的依从性的影响。利用内聚区模型进行的有限元模拟证实了试验是在接近纯模态II条件下进行的。通过准静态试验,分析了初始断裂韧度和稳态断裂韧度。观察到纤维桥接,这被认为解释了特征的r曲线效应。从疲劳试验来看,巴黎定律在每次试验中都具有很宽的gm2 a x范围。因此,碳-玻璃界面的准静态和疲劳断裂行为的表征是成功的。


Microstructural Characterisation of fibre-hybrid polymer composites using U-Net on optical images

Ji Dong, Ali Kandemir, Ian Hamerton

doi:10.1016/j.compositesa.2024.108569

基于光学图像的U-Net表征纤维杂化聚合物复合材料微观结构

This study investigates the application of deep learning-based image segmentation using 2D optical imaging for the microstructural characterisation of composite materials with hybridised fibres, offering a potentially cost-effective alternative to computed tomography/3D imaging. Laminates were produced using the HiPerDiF method, combining discontinuous carbon and basalt fibres to reinforce a poly(L-lactic acid) (PLA) matrix. The results demonstrate that the Generalised Dice Loss function significantly outperforms others, particularly in the void class, achieving a 19% improvement in Dice Similarity Score on an unseen dataset for full image characterisation. Similarly, for Boundary Intersection over Union (IoU), which measures the accuracy of local boundary detail capture, the model trained with Generalised Dice Loss achieved 61.4%, compared to 55.0% for the next best model trained with Compound Loss. These findings suggest that regional loss functions are better suited for image-based microstructural characterisation and quality inspection. Additionally, volume fraction, relative fibre and void ratios, and fibre alignment computed from the segmentation results closely match ground truth data. Challenges related to data limitations and variability are also briefly discussed.

本研究探讨了基于深度学习的图像分割的应用,使用二维光学成像来表征混合纤维复合材料的微观结构,为计算机断层扫描/3D成像提供了一种潜在的经济可行的替代方案。层压板采用HiPerDiF方法生产,结合不连续的碳和玄武岩纤维来增强聚乳酸(PLA)基质。结果表明,广义骰 子损失函数明显优于其他函数,特别是在void类中,在完整图像表征的未见数据集上,骰 子相似度得分提高了19%。类似地,对于边界交集(IoU),测量局部边界细节捕获的准确性,用广义骰 子损失训练的模型达到了61.4%,而用复合损失训练的下一个最佳模型为55.0%。这些发现表明,区域损失函数更适合于基于图像的微结构表征和质量检测。此外,根据分割结果计算的体积分数、相对纤维和空隙比以及纤维排列与地面真实数据非常吻合。还简要讨论了与数据限制和可变性有关的挑战。


Composites Part B: Engineering

A unified strain energy-based fatigue life prediction methodology for composite and metal adhesive joints: Effects of adhesive, geometry and, environment

Fernando Castro Sousa, Alireza Akhavan-Safar, Ricardo J.C. Carbas, Eduardo A.S. Marques, Lucas F.M. da Silva

doi:10.1016/j.compositesb.2024.112022

基于应变能的复合材料和金属粘接接头疲劳寿命预测方法:粘接、几何和环境的影响

Ensuring the efficiency and safety of bonded structures across diverse engineering sectors requires a robust fatigue model for adhesive joints in both composite and metal substrates. This study presents a unified fatigue life prediction methodology for similar and dissimilar composite and metal adhesive joints. The proposed model integrates hydrostatic and deviatoric strain energy density components with the theory of critical distances. The model has been validated against diverse experimental data from different joint geometries, loading conditions, and different environments. The linear-elastic assumption is sufficient for toughened epoxies, whereas an elastoplastic model is necessary for ductile methacrylate adhesives. Calibration based on a single fatigue test yields the highest accuracy, while quasi-static test calibration is also satisfactory. The methodology addresses diverse loading conditions and environmental factors, showing a strong correlation with experimental results. It advances the performance, design, and reliability of similar and dissimilar composite to metal adhesive joints.

为了确保不同工程领域的粘合结构的效率和安全性,需要针对复合材料和金属基板的粘合接头建立一个强大的疲劳模型。提出了一种统一的相似和不同复合材料和金属粘接接头疲劳寿命预测方法。该模型将流体静力和偏应变能密度分量与临界距离理论相结合。该模型已通过不同节点几何形状、加载条件和不同环境的实验数据进行了验证。对于增韧环氧树脂,线弹性假设是足够的,而对于延性甲基丙烯酸酯胶粘剂,弹塑性模型是必要的。基于单一疲劳试验的校准精度最高,而准静态试验校准也令人满意。该方法考虑了不同的加载条件和环境因素,与实验结果有很强的相关性。它提高了相似和不同复合材料对金属粘合接头的性能、设计和可靠性。


Preparation of energy-efficient, environmentally friendly and high-strength biocomposites from wood fibre ultramicro self-composite cellulose matrices

MingTao Bai, Yang Yang, Lei Zhang, HongFei Huo, Jijuan Zhang, Zhifeng Wang, Zhongfeng Zhang

doi:10.1016/j.compositesb.2024.112047

   

木纤维超微自复合纤维素基质制备节能环保高强生物复合材料

Considering the diminishing forest as a natural resource, the efficient use of small-diameter shrubs is crucial for global sustainable development. This approach has significant potential to prevent wasting forest resources and reduce carbon emissions. However, small-diameter timber has inherent drawbacks, such as the looseness of this material, susceptibility to cracking and deformation, and low strength, all of which significantly impact its range of applications. In this study, an efficient, green method was developed to prepare adhesive-free biocomposites from discarded small-diameter shrubs via ultrasonic pretreatment and thermoforming. After the ultrasonic pretreatment, the flexural and tensile strengths of the biocomposites increased by 145% and 132%, respectively. Ultrasonic pretreatment separated and destroyed chemical bonds among the lignocellulosic biomass macromolecules through high-speed shear and microjets. This process significantly increased the amount of binding sites on the cellulose fibres, and further densified the cell walls through hot pressing. Moreover, the ultrasonic pretreatment may remove components of the wood flour that act as fillers or density enhancers, resulting in a reduction in the density of the biocomposite. Simultaneously, lignin acted as a binder and improved fibre bonding through both physical and chemical cross-linking, resulting in a dense cellulose structure with a three-dimensional lattice structure and a less hydrophilic surface, as evidenced by a water contact angle of 81.72°. In addition, the high-quality, binder-free biocomposites did not emit harmful gases such as formaldehyde. Hence, they are expected to become sustainable materials for building decoration and furniture applications in the future.

考虑到森林作为一种自然资源的日益减少,小直径灌木的有效利用对全球可持续发展至关重要。这种方法在防止森林资源浪费和减少碳排放方面具有巨大潜力。然而,小直径木材具有固有的缺点,例如材料的松散,易开裂和变形,强度低,所有这些都严重影响了其应用范围。本研究开发了一种高效、绿色的方法,通过超声波预处理和热成型,从废弃的小直径灌木中制备无粘合剂生物复合材料。经超声预处理后,生物复合材料的抗弯强度和拉伸强度分别提高了145%和132%。超声波预处理通过高速剪切和微射流分离和破坏木质纤维素生物质大分子之间的化学键。这一过程显著增加了纤维素纤维上结合位点的数量,并通过热压使细胞壁进一步致密化。此外,超声波预处理可以去除木粉中作为填料或密度增强剂的成分,从而导致生物复合材料密度的降低。同时,木质素作为粘合剂,通过物理交联和化学交联改善纤维的结合,使纤维素结构致密,具有三维晶格结构,表面亲水性较低,水接触角为81.72°。此外,这种高质量、无粘合剂的生物复合材料不会释放甲醛等有害气体。因此,它们有望成为未来建筑装饰和家具应用的可持续材料。


Enhanced carbon fiber interface with thermoplastics via nanostructure surface modification: failure, morphology and wettability analysis

Weiqing Fang, Adam Pearson, Yige Huang, Hani E. Naguib

doi:10.1016/j.compositesb.2024.112054

   

通过纳米结构表面改性增强碳纤维与热塑性塑料的界面:失效、形貌和润湿性分析

Improving the fiber-matrix adhesion in thermoplastic composites remains a significant challenge due to the lack of chemical bonding between thermoplastics and common reinforcing fibers. This study investigates the effectiveness of carbon fibers enhanced with nanostructure surface modification for strengthening the interfacial adhesion to thermoplastic matrices. The fiber surface was modified with graphene nanoplatelets (GNP) through the facile coating method, and the apparent interfacial shear strength (IFSS) was determined by the single-fiber pullout test. GNP-coated fiber improved IFSS by 74% with neat high-density polyethylene (HDPE-Neat) and 28% with maleic anhydride-grafted HDPE (HDPE-8MA), while reduced by 27% with polyamide 6 (PA6) due to different failure mechanisms. Morphology, chemical, and wettability analysis were conducted on the nano-enhanced carbon fibers to quantitatively elucidate these findings on micro/nanoscale, combining machine learning-based image segmentation, X-ray photoelectron spectroscopy (XPS), and contact-angle measurements of intermittent beading on fibers.

由于热塑性塑料与普通增强纤维之间缺乏化学结合,提高热塑性复合材料中纤维-基体的粘附性仍然是一个重大挑战。本研究考察了纳米结构表面改性增强碳纤维与热塑性基体界面粘附的有效性。用石墨烯纳米薄片(GNP)通过易涂法对纤维表面进行改性,并通过单纤维拉拔试验测定纤维的表观界面剪切强度(IFSS)。采用纯高密度聚乙烯(HDPE- neat)和马来酸酐接枝HDPE (HDPE- 8ma)分别提高了74%和28%的IFSS,而采用聚酰胺6 (PA6)由于失效机制的不同,使IFSS降低了27%。结合基于机器学习的图像分割、x射线光电子能谱(XPS)和纤维上间歇性珠状的接触角测量,对纳米增强碳纤维进行了形态学、化学和润湿性分析,以在微/纳米尺度上定量阐明这些发现。


Controllable fabrication of the luminescent photocatalytic material AgB/SMSO for application in cement: Optimization of doping strategies and all-weather degradation of pollutants

Xinjie Cai, Yidong Xu

doi:10.1016/j.compositesb.2024.112060

水泥用发光光催化材料AgB/SMSO的可控制备:掺杂策略优化及污染物全天候降解

This paper presents an innovative luminescent photocatalytic material, Ag3PO4/BiVO4/Sr2MgSi2O7:(Eu2+, Dy3+) (AgB/SMSO), which overcomes a pivotal limitation of photocatalysts—dependence on a light source—and effectively remediates pollutants and augments cement-based composite properties. The efficient carrier separation facilitated by Ag3PO4, in conjunction with the broad spectral response of BiVO4, enables AgB/SMSO to harness the internal luminescent properties of SMSO as a persistent light source, achieving continuous degradation of pollutants, which reveals the exceptional afterglow characteristics and photocatalytic activity of AgB/SMSO. At a 1:1:40 ratio, AgB/SMSO maintained its catalytic efficacy for over 8 h in the dark (methylene blue degradation rate of 70.43%), surpassing the 3-hour limit of current luminescent photocatalysts. Furthermore, the impact of integrating AgB/SMSO with cement on early-stage cement hydration, morphology, and micromechanical properties was comprehensively assessed. Ultimately, the overall photocatalytic capability of the derived AgB/SMSO cement-based composites was evaluated through experiments, revealing the synergistic mechanisms involved. This study not only enriches the theoretical understanding of photocatalysis but also provides a robust technical foundation for the innovation of environmentally friendly building materials and the advancement of sustainable urban development.

本文提出了一种创新的发光光催化材料Ag3PO4/BiVO4/Sr2MgSi2O7:(Eu2+, Dy3+) (AgB/SMSO),它克服了光催化剂依赖光源的关键限制,有效地修复了污染物并增强了水泥基复合材料的性能。Ag3PO4促进了高效的载流子分离,结合BiVO4的广谱响应,使AgB/SMSO能够利用SMSO的内部发光特性作为持续光源,实现污染物的连续降解,这揭示了AgB/SMSO独特的余辉特性和光催化活性。在1:1:40的比例下,AgB/SMSO在黑暗中保持了8 h以上的催化效果(亚甲蓝降解率为70.43%),超过了目前发光光催化剂3小时的极限。此外,还综合评估了AgB/SMSO与水泥的掺入对水泥早期水化、形态和微观力学性能的影响。最后,通过实验评估了衍生的AgB/SMSO水泥基复合材料的整体光催化能力,揭示了所涉及的协同机制。本研究不仅丰富了光催化的理论认识,而且为环保建筑材料的创新和城市可持续发展的推进提供了坚实的技术基础。


Composites Science and Technology

Influence of expansion ratio and multilayered gradient structure on the electromagnetic interference shielding performance of lightweight poly (lactic acid)/carbon nanostructures composite foams

Qian Ren, Youquan Wei, Xueyun Li, Cao Yu, Long Wang, Bin Shen, Wenge Zheng

doi:10.1016/j.compscitech.2024.110992

   

膨胀率和多层梯度结构对轻质聚乳酸/碳纳米复合泡沫电磁干扰屏蔽性能的影响

Cellular structures incorporated in conductive polymer composites (CPC) are gaining recognition as a promising alternative to traditional metal materials for electromagnetic interference (EMI) shielding applications, owing to their outstanding properties and lightweight nature. In this study, the polylactic acid (PLA)/carbon nanostructure (CNS) composite foam with a multilayered gradient structure was prepared by supercritical carbon dioxide (CO2) foaming technology. The original size of the sample, saturation pressure, and foaming temperature had obvious effects on the foaming behavior of the PLA/CNS composite. In the prepared multilayered gradient-structured sample, the CNS content increased layer by layer (from 1 wt% to 7 wt%), and its density could be as low as 0.22 g/cm³. In addition, the EMI SE value of the prepared sample could be as high as 51.8 dB with an absorption coefficient of 0.85, thus providing superior EMI shielding performance. This result indicated that high-performance and lightweight polymer-based shielding materials could be obtained by preparing multilayered gradient-structured foam samples, which have broad application prospects in aerospace and electronics.

导电性聚合物复合材料(CPC)的细胞结构由于其优异的性能和轻便的特性,被认为是传统金属材料在电磁干扰(EMI)屏蔽应用中的一种有前途的替代品。本研究采用超临界二氧化碳(CO2)发泡技术制备了具有多层梯度结构的聚乳酸(PLA)/碳纳米结构(CNS)复合泡沫材料。样品的原始尺寸、饱和压力和发泡温度对PLA/CNS复合材料的发泡行为有明显的影响。在制备的多层梯度结构样品中,CNS含量逐层增加(从1 wt%增加到7 wt%),其密度可低至0.22 g/cm³。此外,制备的样品的EMI SE值可高达51.8 dB,吸收系数为0.85,具有优异的EMI屏蔽性能。这一结果表明,制备多层梯度结构泡沫样品可以获得高性能轻质聚合物基屏蔽材料,在航空航天和电子领域具有广阔的应用前景。


Enhanced Electromagnetic Wave Absorption and Thermal Conductivity in Epoxy Composites with a Heterostructure-Rich 3D MoS₂/CMF Network Framework

Haoran Geng, Long Zhao, Jing Deng, Jingru Chen, Yihao Fan, Qingyun Zhao, Hongxing Gui, Jianhe Liao, Yanfang Zhao, Yongxin Qian, Guizhen Wang

doi:10.1016/j.compscitech.2024.110993

   

具有丰富异质结构的三维MoS 2 /CMF网络框架的环氧复合材料的电磁波吸收和导热性

With the widespread application of highly integrated and high-frequency power devices in the electronics field, traditional electronic packaging materials can no longer effectively resist the harm caused by electromagnetic interference and heat accumulation to electronic equipment. To address these challenges, we have successfully constructed a heterostructure-rich dual-level three-dimensional (3D) network framework (MoS2/CMF) by effectively integrating molybdenum disulfide (MoS2) with carbonized melamine foam (CMF). These fillers were then composited with epoxy resin (EP) to develop MoS2/CMF/EP composites exhibiting both electromagnetic wave absorption (EMA) and enhanced thermal conductivity. Specifically, two-dimensional (2D) MoS2 nanosheets with a 1T/2H-phase structure uniformly grew on the surface of CMF, improving the poor impedance characteristics of the 3D carbon structure and increasing heterointerfaces and multiple scattering abilities. Owing to the synergistic effects of attenuation performance and impedance matching, the EP-based MoS2/CMF-1 composite demonstrated an impressive reflection loss value of -64.80 dB and an effective absorption bandwidth of 8.48 GHz, achieved with only a 5 wt.% loading. Correspondingly, CST simulation results indicated that when electromagnetic waves are vertically incident on MoS2/CMF-1/EP samples, the radar cross-section (RCS) attenuation value can reach up to 35.4 dBm2. Moreover, the highly interconnected 3D carbon structure of CMF provides broad pathways for phonon transport, resulting in the thermal conductivity of MoS2/CMF-1/EP reaching 0.41 W/m·K at room temperature, a nearly 141% improvement compared to pure EP. This multifunctional EP-based composite, with its high-efficiency EMA and thermal management performance, shows great potential for application in the packaging of highly integrated electronic devices.

随着高集成度、高频功率器件在电子领域的广泛应用,传统的电子封装材料已不能有效抵御电磁干扰和热量积累对电子设备造成的危害。为了解决这些挑战,我们通过将二硫化钼(MoS2)与碳化三聚氰胺泡沫(CMF)有效整合,成功构建了富含异质结构的双层三维(3D)网络框架(MoS2/CMF)。然后将这些填料与环氧树脂(EP)复合,制备出具有电磁波吸收(EMA)和增强导热性的MoS2/CMF/EP复合材料。具体而言,具有1T/ 2h相结构的二维(2D) MoS2纳米片在CMF表面均匀生长,改善了三维碳结构的阻抗特性,增加了异质界面和多次散射能力。由于衰减性能和阻抗匹配的协同效应,基于ep的MoS2/CMF-1复合材料显示出令人印象深刻的反射损耗值为-64.80 dB,有效吸收带宽为8.48 GHz,负载仅为5.wt .%。相应的,CST仿真结果表明,电磁波垂直入射到MoS2/CMF-1/EP样品上,雷达截面(RCS)衰减值可达35.4 dBm2。此外,高度互连的CMF三维碳结构为声子输运提供了广阔的途径,导致MoS2/CMF-1/EP在室温下的导热系数达到0.41 W/m·K,比纯EP提高了近141%。这种多功能ep基复合材料具有高效的EMA和热管理性能,在高度集成的电子器件封装中显示出巨大的应用潜力。



来源:复合材料力学仿真Composites FEM
ACTMechanicalOpticalMAGNETDeform疲劳断裂复合材料化学光学航空航天建筑电子理论材料控制
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【新文速递】2024年11月26日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Thin-Walled Structures 3 篇International Journal of Solids and StructuresBeyond effective stiffness: A modified differential Mori-Tanaka-Voigt homogenization for predicting stresses in individual inclusionsDeepjyoti Dhar, Atul Jaindoi:10.1016/j.ijsolstr.2024.113152超越有效刚度:用于预测单个夹杂应力的改进的Mori-Tanaka-Voigt微分均质化Mean field homogenization (MFH) methods are widely employed for homogenizing heterogeneous materials. However, they are limited to predicting effective properties and phase-averaged stresses, failing to capture stresses within individual inclusions. This paper introduces a novel homogenization approach, termed MDMT-Voigt, aimed at addressing this lacuna. The proposed model is validated extensively using finite element analysis (FEA), encompassing virtual Representative Volume Elements (RVEs) with a range of aspect ratios, volume fractions, and orientation distributions. Furthermore, validation is conducted using RVEs derived from experimentally determined microstructures via micro-computed tomography. Across all models considered, the FEA results yield a range of stresses for inclusions with same orientation and aspect ratio which is captured well by the proposed MDMT-Voigt model. Prediction of stresses in individual inclusions represents a significant advancement over conventional MFH methods, offering substantial potential for enhanced micromechanics modelling comparable to full finite element approaches, but at a computational efficiency order of magnitude lower. The paper ends with a demonstration confirming improved micromechanics using the Modified Coulomb criteria.平均场均质(MFH)方法被广泛应用于非均质材料的均质化。然而,它们仅限于预测有效性质和相平均应力,而不能捕获单个夹杂物中的应力。本文介绍了一种新的均质化方法,称为MDMT-Voigt,旨在解决这一空白。该模型采用有限元分析(FEA)进行了广泛的验证,包括具有一系列宽高比、体积分数和方向分布的虚拟代表性体积单元(RVEs)。此外,通过微计算机断层扫描实验确定的微观结构,使用RVEs进行验证。在所有考虑的模型中,FEA结果产生了具有相同取向和纵横比的包裹体的应力范围,这被提出的MDMT-Voigt模型很好地捕获。与传统的MFH方法相比,单个包裹体的应力预测是一项重大进步,为增强微观力学建模提供了巨大的潜力,可与全有限元方法相媲美,但计算效率要低一个数量级。最后,用修正的库仑准则验证了改进的细观力学。Journal of the Mechanics and Physics of SolidsCapillary rise in a packing of glass spheresRatul Das, Vikram S. Deshpande, Norman A. Fleckdoi:10.1016/j.jmps.2024.105963毛细管在玻璃球填料中上升A series of experiments are performed to give insight into the mechanisms of liquid rise in a 3D dense random packing of glass spheres. A sharp knee in the log-log plot of water height h versus time t curve is observed, with an attendant change in h(t) characteristic from h ∝ t0.5 to h ∝ t0.05. This behaviour is observed for 5 choices of diameter distribution of spheres, such that the mean diameter is in the range of 0.22 mm to 1.20 mm, and the ratio of standard deviation to mean diameter lies between 0.014 and 0.157. Immediate arrest in water rise occurs when the water reservoir is removed from the bottom of the column, in support of the conclusion that water rise is by capillary action. In the post-knee regime of the h(t) response, water rise occurs in a jerky manner by a series of jumps, involving transverse jumps and more occasional vertical jumps in water ingress; each jump is by an increment of sphere diameter. The incubation time for each vertical jump is sensitive to height of meniscus and dictates the overall rate of water rise. Pendular-rings at the junctions between glass spheres are not observed above the meniscus; this casts doubt upon the notion that the jerky motion of the meniscus is due to the incubation time for a vapour-fed pendular-ring to grow and coalesce with the meniscus. Possible sources of the height-dependent incubation time for each vertical jump are discussed, including a time-dependent increase in surface tension. Additional insight is obtained by observing water rise, and glycerol rise in (i) a monolayer of glass spheres, (ii) in a capillary tube of diameter slightly greater than that of the glass beads and filled with a single column of glass spheres and (iii) an empty capillary tube. Continued liquid rise beyond the knee in the h(t) curve is noted in all cases except for that of an empty capillary tube.一系列实验旨在探究玻璃球三维密集随机堆砌中液体上升的机制。在水位高度h与时间t的对数-对数图中观察到一个明显的拐点,伴随着h(t)特征的变化,从h ∝ t0.5变为h ∝ t0.05。这种行为在5种不同直径分布的玻璃球中被观察到,其平均直径在0.22毫米至1.20毫米之间,标准差与平均直径之比在0.014至0.157之间。当从柱子底部移除水容器时,水位立即停止上升,这支持了水位上升是由毛细作用引起的结论。在h(t)响应的拐点后区域,水位以一系列跳跃的方式不规则上升,涉及横向跳跃和更偶尔的水渗透垂直跳跃; 每次跳跃都是一个球体直径的增量。每个垂直跳跃的孵化时间对液面高度敏感,并决定了水位上升的整体速度。在玻璃球接合处的关节处没有观察到摆动环。这使人们对“膝关节液面的抖动是由蒸汽供能的摆环生长并与液面凝聚所需的孵化时间造成的”这一观点产生了怀疑。讨论了每个垂直跳跃高度依赖的孵化时间的可能来源,包括表面张力随时间的变化。通过观察水在(i)一层玻璃球、(ii)直径略大于玻璃珠的毛细管(内装有一根玻璃珠柱)和(iii)空毛细管中的上升情况,获得了更多洞察力。在h(t)曲线中,除了空毛细管的情况外,所有情况下均观察到了液面在膝盖处之后继续上升。Thin-Walled StructuresStainless steel I-section beams at elevated temperatures: Lateral–torsional buckling behaviour and designMerih Kucuklerdoi:10.1016/j.tws.2024.112720不锈钢工字钢在高温下:侧向扭转屈曲行为和设计In this paper, a comprehensive investigation into the structural response and design of stainless steel I-section beams susceptible to lateral–torsional buckling (LTB) at elevated temperatures is carried out. A very large number of stainless steel I-section beams are considered, taking into account various cross-section geometries, beam slendernesses and different stainless steel grades and elevated temperature levels. Extensive structural performance data on the behaviour of stainless steel I-section beams are generated through nonlinear shell finite element modelling. Assessment of the existing LTB design rules for stainless steel I-section beams at elevated temperatures provided in the current version of the European structural steel fire design standard EN 1993-1-2 and its upcoming version prEN 1993-1-2 is presented. New LTB design rules based upon an Ayrton-Perry equation that is able to provide a consistent mechanical appraisal of the LTB behaviour of stainless steel I-section beams in fire are proposed. The accuracy and safety of the proposed new LTB design rules for stainless steel I-section beams are comprehensively verified. It is also shown that the proposed LTB design equations in this paper lead to a considerably higher level of consistency and reliability for the LTB design of stainless steel I-section beams in fire relative to the LTB assessment rules provided in EN 1993-1-2 and prEN 1993-1-2.本文对高温下易受侧向扭转屈曲(LTB)影响的不锈钢工字截面梁的结构响应和设计进行了全面的研究。考虑到不同的截面几何形状、梁的细长度、不同的不锈钢等级和升高的温度水平,考虑了大量的不锈钢工字钢。广泛的结构性能数据的行为不锈钢工字钢截面梁是通过非线性壳有限元建模产生的。介绍了欧洲结构钢防火设计标准EN 1993-1-2和即将发布的版本prEN 1993-1-2中提供的高温下不锈钢工字截面梁的现有LTB设计规则的评估。提出了基于Ayrton-Perry方程的新的LTB设计规则,该规则能够为不锈钢工字截面梁在火灾中的LTB行为提供一致的力学评估。全面验证了所提出的不锈钢工字截面梁LTB设计规则的准确性和安全性。本文提出的LTB设计方程相对于EN 1993-1-2和prEN 1993-1-2规定的LTB评定规则,对不锈钢工字钢火灾条件下的LTB设计具有较高的一致性和可靠性。Analysis of warping defect formation mechanisms in hot molding of CF/PEEK thin-wall structures and their influence on mechanical propertiesYue Li, Aisha Yang, Yuting Liu, Yu Gao, Jianfeng Zhou, Yan Dong, Shu Zhudoi:10.1016/j.tws.2024.112740CF/PEEK薄壁结构热成型翘曲缺陷形成机理及其对力学性能的影响分析The hot molding of carbon fiber-reinforced polyether ether ketone composites (CF/PEEK) thin-wall structures employs high cooling rates, which cause uneven material shrinkage across different parts and pronounced warping defects. This study fabricated CF/PEEK thin-wall laminates with a thickness of 1.2 mm through die-pressing technology and analyzed the effects of various cooling processes on plate warping. In addition, the study elucidated the formation mechanism of warping defects in CF/PEEK thin-wall structures and plotted a cooling rate curve to determine a strategy for effectively mitigating such defects. Notably, CF/PEEK hot molding warping involves an asynchronous contraction of molecular chains of crystalline polymers, leading to thermal residual stress. This study also investigated the effects of warpage on bending properties and stability. When warpage ranged from 10 to 15 mm, the maximum bending strength deviation along the plane was approximately 150 MPa, indicating that excessive warping substantially reduces bending strength. Moreover, laminates with minor warpage differences exhibited consistent performance stability. Overall, this study provides valuable insights for enhancing the forming quality of CF/PEEK, thereby promoting their application in advanced equipment.碳纤维增强聚醚醚酮复合材料(CF/PEEK)薄壁结构的热成型采用高冷却速率,导致材料在不同部位收缩不均匀,并出现明显的翘曲缺陷。采用模压工艺制备了厚度为1.2 mm的CF/PEEK薄壁层压板,并分析了不同冷却工艺对板材翘曲的影响。此外,本研究阐明了CF/PEEK薄壁结构翘曲缺陷的形成机理,并绘制了冷却速率曲线,以确定有效缓解此类缺陷的策略。值得注意的是,CF/PEEK热成型翘曲涉及结晶聚合物分子链的异步收缩,导致热残余应力。本研究还探讨了翘曲对弯曲性能和稳定性的影响。当翘曲量为10 ~ 15 mm时,弯曲强度沿平面的最大偏差约为150 MPa,表明翘曲量过大会大大降低弯曲强度。此外,具有较小翘曲差异的层压板表现出一致的性能稳定性。总的来说,本研究为提高CF/PEEK的成形质量,从而促进其在先进设备中的应用提供了有价值的见解。Determination of residual stress in hybrid laser-arc welded U-rib-to-deck joints by thermo-metallurgical-mechanical simulation and neutron diffractionYuantai Li, Shaoning Geng, Jian Li, Zhijian Fan, Chu Han, Jun Jin, Ping Jiangdoi:10.1016/j.tws.2024.112755用热冶金-力学模拟和中子衍射法测定u型肋-甲板混合激光弧焊接头残余应力Welding residual stress is crucial to the fatigue performance and reliability of U-rib-to-deck joints, and its accurate measurement and control remains challenging and lacking an effective approach. In this paper, a thermo-metallurgical-mechanical finite element model considering solid-state phase transformation was developed to investigated the residual stress states of U-rib-to-deck joints fabricated using hybrid laser-arc welding technique. Neutron diffraction testing was conducted to determine the residual stress distribution in three orthogonal directions to validate the model. The results showed that solid-state phase transformation involving changes in mixed phase properties and transformation strain significantly influenced the residual stress in hybrid laser-arc welded U-rib-to-deck joints. The low yield strength property of the supercooled austenite and the volumetric expansion of the bainite transformation strain are crucial for residual stress reduction. A reasonable S-shaped agreement trend was observed between residual stress simulation and neutron diffraction data along the potential crack propagated path. Thermo-metallurgical-mechanical modeling helps to control welding residual stress fields via simulation methods, which is crucial to consider solid-state phase transformation. These findings provide support for assessing the fatigue performance of U-rib structures using hybrid laser-arc welding.焊接残余应力对u型肋-甲板接头的疲劳性能和可靠性至关重要,其精确测量和控制仍然具有挑战性,并且缺乏有效的方法。本文建立了考虑固相转变的热-冶金-力学有限元模型,研究了激光电弧复合焊接u型肋-甲板接头的残余应力状态。通过中子衍射测试确定了三个正交方向上的残余应力分布,验证了模型的正确性。结果表明,固态相变对u型肋-板复合激光弧焊接头的残余应力有显著影响,相变过程中混合相性能和相变应变的变化对残余应力有显著影响。过冷奥氏体的低屈服强度和贝氏体相变应变的体积膨胀是减小残余应力的关键。沿潜在裂纹扩展路径,残余应力模拟结果与中子衍射数据呈合理的s型一致趋势。热-冶金-力学建模有助于通过仿真方法控制焊接残余应力场,这对于考虑固态相变至关重要。这些研究结果为评估混合激光弧焊u肋结构的疲劳性能提供了支持。来源:复合材料力学仿真Composites FEM

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