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【新文速递】2024年6月9日固体力学SCI期刊最新文章

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今日更新:Journal of the Mechanics and Physics of Solids 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 2 篇

Journal of the Mechanics and Physics of Solids

Correlation between synthesis parameters and hyperelasticity of hydrogels: experimental investigation and theoretical modeling

Zhicheng Wang, Danming Zhong, Rui Xiao, Shaoxing Qu

doi:10.1016/j.jmps.2024.105733

合成参数与水凝胶超弹性的关系:实验研究与理论建模

The mechanical properties of hydrogels are significantly influenced by synthesis parameters. Although the mapping from the space of synthesis parameters to the space of properties has been investigated experimentally, a quantitative theoretical framework is still lacking. In this work, the effect of synthesis parameters on the hyperelastic behaviors of hydrogels was experimentally studied. Subsequently, we conducted theoretical analysis by combining the constitutive model and polymer physics to quantify the correlation between synthesis parameters (the initial water content, current water content, and degree of cross-linking) and hyperelasticity (the elastic modulus, degree of entanglement, and stress-stretch ratio curve) of hydrogels. The internal relation between critical polymer content for entanglement and both the initial water content and degree of cross-linking arises from the scaling laws. By analyzing the critical polymer content for entanglement and comparing it with the current polymer content, hydrogels are categorized as either cross-linking-dominated or entanglement-dominated. The current study indicates that a low degree of cross-linking, i.e., a long-chain structure, is an important prerequisite for plenty of entanglements. Hydrogels with low cross-linking are highly entangled, whether they possess high initial water content/low current water content or low initial water content/high current water content. This work paves the way for the systematic design of synthesis parameters, thereby guiding the modulation and optimization of the overall mechanical properties and the application of hydrogels.

水凝胶的力学性能受合成参数的影响较大。虽然已经对合成参数空间到性质空间的映射进行了实验研究,但仍然缺乏定量的理论框架。实验研究了合成参数对水凝胶超弹性行为的影响。随后,我们结合本构模型和高分子物理学进行理论分析,量化水凝胶的合成参数(初始含水量、当前含水量、交联度)与超弹性(弹性模量、缠结度、应力-拉伸比曲线)之间的相关性。缠结的临界聚合物含量与初始含水量和交联度之间的内在关系源于标度定律。通过分析导致缠结的关键聚合物含量,并将其与现有聚合物含量进行比较,将水凝胶分为交联为主和缠结为主两类。目前的研究表明,低交联度,即长链结构,是大量缠结的重要前提。低交联的水凝胶,无论是高初始含水量/低电流含水量,还是低初始含水量/高电流含水量,都是高度纠缠的。这项工作为系统设计合成参数铺平了道路,从而指导水凝胶整体力学性能的调制和优化以及水凝胶的应用。


International Journal of Plasticity

Onset of dynamic void coalescence in porous ductile solids

Z.G. Liu, W.H. Wong, T.F. Guo

doi:10.1016/j.ijplas.2024.104019

多孔延性固体中动态孔洞聚并的开始

This paper investigates void growth and coalescence in porous ductile solids under dynamic loading condition. A physical definition for the onset of void coalescence in porous ductile solids under dynamic loading is proposed. The onset is deemed to occur when the third invariant of the tensorial form of the Hill–Mandel condition attains a zero value. The definition allows for systematic investigations on the effects of dimensionless stress rate κ and stress state, defined by the stress triaxiality T and Lode parameter L, on the onset of void coalescence via micromechanical analyses. The analyses reveal that the critical macroscopic effective strain for the onset of void coalescence displays an increasing–decreasing transition trend as the dimensionless stress rate increases, for all levels of T and L considered. The macroscopic effective strain at the transition is identified as the “ductile–brittle” transition strain. The dimensionless stress rate at which the transition strain occurs is found to be relatively constant. A mapping in the κ−T space for L=−1, representative of a generalized uniaxial tension typical in spall fracture experiments, is established which depicts regions where coalescence and non–coalescence can take place, as well as the ductile–brittle regions demarcated by a ductile–brittle transition curve. The results also show that the critical void volume fraction and macroscopic effective strain at the onset of void coalescence are insensitive to inertia at high stress triaxialities at L=−1.

本文研究了动态加载条件下多孔韧性固体中的空隙增长和凝聚。本文提出了动态加载条件下多孔韧性固体中空隙凝聚开始的物理定义。当希尔-曼德尔(Hill-Mandel)条件的张量形式的第三个不变量达到零值时,即认为开始凝聚。根据这一定义,可以通过微观力学分析系统地研究无量纲应力速率 κ 和应力状态(由应力三轴度 T 和洛德参数 L 定义)对空洞凝聚开始的影响。分析表明,在考虑的所有 T 和 L 水平上,随着无量纲应力率的增加,空洞凝聚开始时的临界宏观有效应变呈现出由增到减的过渡趋势。过渡时的宏观有效应变被确定为 “韧性-脆性 ”过渡应变。过渡应变发生时的无量纲应力速率相对恒定。建立了 L=-1 的 κ-T 空间映射,代表了典型的剥落断裂实验中的广义单轴拉伸,描绘了可能发生凝聚和非凝聚的区域,以及由延性-脆性过渡曲线划分的延性-脆性区域。结果还表明,在 L=-1 的高应力三轴度条件下,空隙凝聚开始时的临界空隙体积分数和宏观有效应变对惯性不敏感。


Thin-Walled Structures

Thermal instability and vibration characteristics of laminated composite struts with Graphene reinforcements: An analysis of distribution patterns and geometrical imperfections

S.F. Nikrad, A.H. Akbarzadeh, M. Bodaghi, M. Hamidinejad, Z.T. Chen

doi:10.1016/j.tws.2024.112083

石墨烯增强层压复合材料支撑的热不稳定性和振动特性:分布模式和几何缺陷分析

This study explores the effect of local buckling on the compressive performance of slender structural elements, particularly those with thin-walled sections. The phenomenon of local buckling significantly reduces the axial compressive stiffness, leading to a notable decrease in the load-bearing capacity of these elements. The main goal of this research is to examine how the post-buckling characteristics of polymeric composite channel section struts can be improved under thermal loading by incorporating multi-layer graphene reinforcements. The solution methodology incorporates the von Karman geometrical nonlinearity and is based on the layerwise third-order shear deformation theory (LW-TSDT). To ascertain the precision and computational performance of the results derived from LW-TSDT, a three-dimensional (3D) finite element model is created in ABAQUS for comparative evaluation. An extensive analysis of nonlinear thermal instability in perfect and geometrically imperfect FG-GRC laminated channel section struts is undertaken to discern the graphene distribution patterns that are most and least effective in elevating the critical buckling temperature and natural frequencies through pre- and post-buckling conditions. The comparative analysis indicates that employing the FG-X graphene distribution pattern across the thickness of the web and flanges in channel section struts leads to a projected increase of 12% in the critical buckling temperature for clamped channel section struts, in contrast to those that adopt the FGO graphene distribution pattern. For cases with simply-supported boundary conditions, this increase is noted to be approximately 9%. Moreover, findings confirm that incorporating an asymmetric graphene distribution pattern (FGV) or introducing geometrical imperfections in the flanges and web that generate a bending moment within the structure from the beginning of thermal loading effectively prevents the primary natural frequencies of FG-GRC channel section struts from declining to zero close to the critical buckling temperature. This is significantly different from scenarios involving perfectly structured and symmetrically reinforced graphene distribution patterns such as FGX.

本研究探讨了局部屈曲对细长构件,特别是薄壁构件抗压性能的影响。局部屈曲现象显著降低了轴向抗压刚度,导致这些构件的承载能力显著降低。本研究的主要目的是研究如何通过加入多层石墨烯增强材料来改善聚合物复合通道截面支板在热载荷下的后屈曲特性。求解方法结合了von Karman几何非线性,基于分层三阶剪切变形理论(LW-TSDT)。为了确定LW-TSDT结果的精度和计算性能,在ABAQUS中建立了三维(3D)有限元模型进行比较评价。本文对完美和几何不完美的FG-GRC层压通道截面支板的非线性热不稳定性进行了广泛的分析,以识别在屈曲前和屈曲后提高临界屈曲温度和固有频率方面最有效和最无效的石墨烯分布模式。对比分析表明,与采用FGO石墨烯分布模式相比,采用FG-X石墨烯分布模式的通道截面支板在腹板和法兰厚度上的临界屈曲温度预计提高了12%。对于具有简单支持边界条件的情况,这一增加约为9%。此外,研究结果证实,在法兰和腹板中加入不对称石墨烯分布模式(FGV)或引入几何缺陷,可以有效防止FG-GRC通道截面支撑的主要固有频率在接近临界屈曲温度时降至零。这与完美结构和对称增强石墨烯分布模式(如FGX)的情况有很大不同。


Experimental and numerical investigations on the mechanical behaviour of large-span circular steel-concrete composite slabs for wind power tower

Liang-Dong Zhuang, Mu-Xuan Tao, Ji-Zhi Zhao, Ke-Yang Yang

doi:10.1016/j.tws.2024.112107

风电塔用大跨度圆形钢-混凝土组合板力学性能试验与数值研究

Circular slabs as novel structural shapes offer excellent application possibilities for offshore wind power foundations. By applying a steel-concrete composite structure to a circular slab, steel consumption can be reduced, and the foundation span can be increased compared to steel structures. In addition, it further reduces the structural height and lightens the self-weight of the structure compared to concrete slabs. In this study, experimental investigations and theoretical analysis analyses were combined. First, four circular steel-concrete composite slab components were produced, and a quasi-static experimental study was conducted. Secondly, based on the elastic-plastic theory, the bearing capacity of the circular steel-concrete composite slab was theoretically derived, and the main parameters affecting the bearing capacity were determined. Finally, a finite element model of a circular steel-concrete composite slab was created and verified based on the test results. A parameter analysis was conducted on the circular composite slab to investigate the influence of factors such as the number of main beams, stiffening rib design, concrete strength, steel strength, and boundary conditions on the ultimate bearing capacity of the structure. A design method for this type of circular steel-concrete composite slab is summarised, which provides a theoretical basis and engineering recommendations for the application of this new type of structure.

圆形板作为一种新颖的结构形式,为海上风电基础提供了良好的应用前景。通过在圆板上采用钢-混凝土组合结构,与钢结构相比,可以减少钢材消耗,并增加基础跨度。此外,与混凝土板相比,它进一步降低了结构高度,减轻了结构的自重。本研究采用实验研究与理论分析相结合的方法。首先,制作了4个圆形钢-混凝土组合板构件,进行了准静力试验研究。其次,基于弹塑性理论,对圆形钢-混凝土组合楼板的承载力进行了理论推导,确定了影响其承载力的主要参数;最后,建立了圆形钢-混凝土组合楼板的有限元模型,并根据试验结果进行了验证。对圆形组合楼板进行了参数分析,探讨了主梁数、加筋设计、混凝土强度、钢材强度、边界条件等因素对结构极限承载力的影响。总结了这种型钢-混凝土组合板的设计方法,为这种新型结构的应用提供了理论依据和工程建议。



来源:复合材料力学仿真Composites FEM
ACTMechanicalSystemMarcAbaqus振动断裂复合材料非线性理论材料试验
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首次发布时间:2024-11-20
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【新文速递】2024年6月11日复合材料SCI期刊最新文章

今日更新:Composite Structures 4 篇,Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 3 篇Composite StructuresLine finite element method for geometrically nonlinear analysis of functionally graded members accounting for twisting effectsGuanghua Li, Zi-Zhang Gu, Hao-Yi Zhang, Weihang Ouyang, Si-Wei Liudoi:10.1016/j.compstruct.2024.118268 考虑扭转效应的功能梯度构件几何非线性分析的线有限元方法Functionally graded materials with spatially varying properties have gained widespread use in various engineering disciplines due to their exceptional mechanical characteristics. Nevertheless, these materials can lead to non-symmetric properties of cross-sections and an offset between centroid and shear center of functionally graded (FG) members, thereby significantly affecting the mechanical behavior. This phenomenon, known as twisting effects, poses a substantial challenge for the geometrically nonlinear analysis of FG members, as existing methods rely on traditional beam-column elements that assume the centroid and shear center of sections coincide. Thus, this paper proposes a new framework for geometrically nonlinear analysis of FG members, incorporating twisting effects through a novel Timoshenko beam-column element. An efficient finite-element-based approach that employs the nonhomogeneous plane triangle (NPT) element for calculating the cross-sectional properties of arbitrary FG cross-sections is presented. These cross-sectional properties are then utilized within the advanced line-element formulation to perform geometrically nonlinear analysis of FG structures considering twisting effects. The accuracy of the proposed method is validated through three examples, followed by several case studies to examine the impact of twisting effects on FG members. Furthermore, the proposed cross-section analysis method is integrated into a new structural analysis software MSASect2 to facilitate its application.具有空间变化特性的功能梯度材料由于其优异的力学特性在各种工程学科中得到了广泛的应用。然而,这些材料会导致功能梯度(FG)构件的截面非对称特性和质心与剪切中心之间的偏移,从而显著影响力学行为。这种被称为扭转效应的现象对FG构件的几何非线性分析提出了实质性的挑战,因为现有的方法依赖于传统的梁柱单元,假设截面的质心和剪切中心重合。因此,本文提出了一种新的框架,用于FG构件的几何非线性分析,通过一种新的Timoshenko梁柱单元纳入扭转效应。提出了一种利用非均匀平面三角形(NPT)单元计算任意FG截面截面特性的有效有限元方法。这些截面特性然后在先进的线素公式中被利用,以执行考虑扭转效应的FG结构的几何非线性分析。通过三个实例验证了所提出方法的准确性,然后通过几个案例研究来检查扭转效应对FG构件的影响。此外,本文还将所提出的截面分析方法集成到新的结构分析软件MSASect2中,以方便其应用。Review on mechanical properties of metal lattice structuresXun Miao, Jianxin Hu, Yiyi Xu, Jun Su, Yang Jingdoi:10.1016/j.compstruct.2024.118267金属晶格结构力学性能研究进展Metallic lattice structures are garnering increasing attention across various research domains for their potential to create lightweight yet high-strength solutions. Their appeal largely stems from a range of beneficial attributes, including their low weight, substantial specific strength and stiffness, and superior energy absorption qualities. These characteristics have facilitated their widespread use in industries like aerospace, shipping, defense, and automotive, particularly in scenarios demanding weight minimization, multifunctionality, and enhanced safety in intricate environments. The mechanical properties of these structures are, therefore, of paramount importance. This paper offers an exhaustive review and synthesis of existing research approaches, production techniques, and evaluations of both static and dynamic mechanical properties associated with metallic lattice structures. It starts by delineating the various types and manufacturing methods, followed by an analysis of factors impacting their mechanical properties. The paper concludes by exploring prospective research avenues concerning the static and dynamic mechanical performance of metallic lattice structures.金属晶格结构因其创造轻质高强度解决方案的潜力而在各个研究领域受到越来越多的关注。它们的吸引力很大程度上源于一系列有益的属性,包括它们的低重量,可观的比强度和刚度,以及优越的能量吸收特性。这些特性促进了它们在航空航天、航运、国防和汽车等行业的广泛应用,特别是在复杂环境中要求重量最小化、多功能和增强安全性的场景中。因此,这些结构的力学性能是至关重要的。本文对现有的研究方法、生产技术以及与金属晶格结构相关的静态和动态力学性能的评估进行了详尽的回顾和综合。它首先描述了各种类型和制造方法,然后分析了影响其机械性能的因素。最后,对金属晶格结构静动力力学性能的研究方向进行了展望。A Transformer-based neural network for automatic delamination characterization of quartz fiber-reinforced polymer curved structure using improved THz-TDSQiuhan Liu, Qiang Wang, Jiansheng Guo, Wenquan Liu, Ruicong Xia, Jiayang Yu, Xinghao Wangdoi:10.1016/j.compstruct.2024.118272基于Transformer的神经网络用于石英纤维增强聚合物弯曲结构的自动分层表征Quartz fiber-reinforced polymer (QFRP) is a vital non-polar material used in aviation wave-transparent structural components. Automatic characterization of delamination defects in QFRP is critical to aviation structural component safety. Terahertz time-domain spectroscopy (THz-TDS) is one of the new non-destructive testing (NDT) methods with highly accurate characterization of internal defects in non-polar material. Hence, attempts to extract features of THz time-domain signals for automatic characterization have been made by using deep learning algorithms. In this work, a Transformer-based neural network to classify the THz time-domain signals collected from a QFRP curved structure for automatic characterization of pre-embedded delamination defects has been reported. A THz-TDS system combined with a collaborative robot for collecting the THz signals from QFRP curved structure has been built. An automatic characterization method framework is developed. Results show that the precision rates of Transformer-based neural network for 1st delamination to 5th delamination are 1.0, 1.0, 1.0, 0.985, 1.0, and F1 score of it is 0.982. During the process of testing, delamination defects inside the QFRP curved structure were visualized using pixels with different colors. Results indicate that the Transformer-based neural network can characterize all pre-embedded delamination defects while minimizing false identification of non-defective areas, performing outstanding generalization.石英纤维增强聚合物(QFRP)是一种重要的非极性材料,用于航空透波结构部件。自动表征 QFRP 中的分层缺陷对航空结构部件的安全性至关重要。太赫兹时域光谱(THz-TDS)是一种新型无损检测(NDT)方法,可对非极性材料的内部缺陷进行高精度表征。因此,人们尝试使用深度学习算法来提取太赫兹时域信号的特征,以便进行自动表征。在这项工作中,报告了一种基于变压器的神经网络,用于对从 QFRP 曲线结构中收集到的太赫兹时域信号进行分类,以自动表征预埋分层缺陷。建立了一个 THz-TDS 系统,该系统与协作机器人相结合,用于从 QFRP 曲面结构中采集 THz 信号。开发了自动表征方法框架。结果表明,基于变压器的神经网络对第 1 层分层至第 5 层分层的精确率分别为 1.0、1.0、1.0、0.985、1.0,其 F1 分数为 0.982。在测试过程中,QFRP 曲线结构内部的分层缺陷用不同颜色的像素可视化显示。结果表明,基于变压器的神经网络可以表征所有预埋分层缺陷,同时最大限度地减少对非缺陷区域的错误识别,具有出色的泛化能力。Form-finding of thermal-adaptive pin-bar assemblies based on eigenvalue modificationHongchuang Liu, Hua Dengdoi:10.1016/j.compstruct.2024.118275基于特征值修正的热自适应针杆组件寻形Lattice structures with tunable expansion properties have been investigated in multidisciplinary fields to control the temperature effects of structures or materials. The expected thermal adaptivity can be achieved by optimizing the structural geometry. A novel method for the form-finding of thermal-adaptive pin-bar assemblies is developed in this paper by considering the control of structural temperature effects as the minimization of the potential energy of the system. Based on the stationarity condition of the potential energy with respect to the nodal coordinates, the compatibility relationship between the thermal elongations of members and the target nodal displacements is proven to be the sufficient and necessary condition for structural thermal adaptivity. The solvability of the compatibility equation is determined by the rank equality between the compatibility matrix and its augmented form, which can be measured by the number of nonzero eigenvalues of its Gramian matrix. The analytical relationship between the eigenvalues of the Gramian matrix and the nodal coordinates is established using the matrix perturbation theory. A numerical strategy based on Newton’s method is proposed in which the eigenvalues are gradually modified by adjusting the nodal coordinates until the rank equality is satisfied. To address the existence of multiple solutions with structural thermal adaptivity, structural symmetry and periodicity constraints are introduced to narrow the solution space. The thermal-adaptive configurations of three illustrative pin-bar assemblies are analyzed using the proposed form-finding method, and the expected thermal deformations are verified for the obtained configurations using the finite element software ABAQUS. Comparing the results obtained by the proposed method with those obtained by nonlinear programming and the genetic algorithm validates the advantages of the proposed method in terms of computational time, optimality of the obtained configuration and applicability to complex structural geometries.具有可调膨胀特性的晶格结构在多学科领域得到了广泛的研究,用于控制结构或材料的温度效应。通过优化结构的几何形状,可以达到预期的热适应性。将结构温度效应控制作为系统势能的最小化,提出了一种热自适应针杆组件寻形的新方法。基于势能相对于节点坐标的平稳条件,证明了构件热伸长与目标节点位移的相容关系是结构热自适应的充要条件。相容方程的可解性由相容矩阵与其增广形式之间的秩相等决定,可由相容矩阵的非零特征值的个数来衡量。利用矩阵摄动理论建立了格拉姆矩阵的特征值与节点坐标的解析关系。提出了一种基于牛顿法的数值策略,通过调整节点坐标逐渐修正特征值,直至满足秩相等。为了解决具有结构热自适应的多解的存在性,引入结构对称性和周期性约束来缩小解空间。采用所提出的寻形方法对3个典型销杆组件的热自适应结构进行了分析,并利用有限元软件ABAQUS对得到的结构进行了预期热变形验证。将所提方法与非线性规划和遗传算法的计算结果进行了比较,验证了所提方法在计算时间短、构型最优性好、适用于复杂几何结构等方面的优势。Composites Part A: Applied Science and ManufacturingA direct correlation between damage parameters and effective permeation coefficients in composite laminatesRaffael Bogenfeld, Caroline Lüders, Michael Ebermann, Vineeth Ravidoi:10.1016/j.compositesa.2024.108307复合材料层合板损伤参数与有效渗透系数之间的直接关系We introduce an innovative approach for determining the gas permeability of composite laminates, explicitly accounting for inter-fiber fracture. Our method forges a direct correlation between the Continuum Damage Mechanics (CDM) damage parameter for transverse inter-fiber fracture and the effective permeation coefficients, which are crucial in assessing leak tightness. This correlation stems from a geometric similarity between the ratio of the damaged material’s load-carrying capacity to that of its pristine state, and the relative projected crack length as crucial parameter for the effective permeability assessment. This CDM-based approach represents a significant advancement in directly deriving a laminate’s permeability from mechanical failure analysis results. This is essential for the design process of Type V hydrogen storage tanks. Literature-based experimental results validate the plausibility of our method, proving its effectiveness across various laminate orientations and damage scenarios. Nonetheless, the observed deviations highlight the need for detailed damage information, elaborate material characterization.我们介绍了一种创新的方法来确定复合材料层合板的透气性,明确地考虑纤维间断裂。我们的方法在横向纤维间断裂的连续损伤力学(CDM)损伤参数与有效渗透系数之间建立了直接关联,而有效渗透系数是评估泄漏密封性的关键。这种相关性源于损坏材料的承载能力与其原始状态的承载能力之比之间的几何相似性,以及相对预计裂缝长度作为有效渗透率评估的关键参数。这种基于cdm的方法在直接从机械失效分析结果中得出层压板的渗透率方面取得了重大进展。这对V型储氢罐的设计过程至关重要。基于文献的实验结果验证了我们的方法的合理性,证明了它在各种层压板方向和损伤场景下的有效性。尽管如此,观察到的偏差强调需要详细的损伤信息,详细的材料表征。Composites Part B: EngineeringMillefeuille-inspired biomass alternate multilayer composite, for excellent absorption-dominated, broadband EMI shielding and Joule heatingQi Zhang, Xiaohong Tang, Qian Zhao, Xianchun Chen, Ke Wang, Qin Zhang, Qiang Fudoi:10.1016/j.compositesb.2024.111620 千叶启发的生物质交替多层复合材料,具有优异的吸收主导,宽带EMI屏蔽和焦耳加热The development of biomass electromagnetic interference (EMI) shielding materials with low cost, low reflection(R-value), and high shielding efficiency is promising but also challenging. Inspired by the alternate structure of a millefeuille, we propose an alternating assembly approach for conductive and magnetic layers. Employing sustainable bamboo fibers (BF) and biodegradable polylactic acid (PLA) as raw matrix, the magnetic and conductive layers were fabricated by compositing copper-plated BF (Cu@BF) and iron-plated BF (Fe@BF) with PLA, respectively. By alternately stacking magnetic and conductive layers and followed by hot pressing, the high EMI SE and low R-value biomass multilayer composite with “multi-(absorption-reflection-reabsorption)” structures were obtained. The performance of different alternating layers (3/5/7/9 layers) was studied, and a linear correlation between layer number, SE, and R-value was established. The results demonstrate that increasing the alternate layer number could readily tune the SE in the X-band from 45.02 dB (3-layer) to 80.2 dB (9-layer) and reduce Rmin from 0.40 to 0.25. Furthermore, the 9-layer composite exhibits approximately 75 dB SE in 1-18 GHz, simultaneously realizing high efficiency, low reflectivity, and broadband shielding. Notably, its excellent conductivity also provides reliable Joule heating performance. The shielding and thermal features of the composite highlight its potential in construction and smart housing heating applications.开发低成本、低反射(r值)、高屏蔽效率的生物质电磁干扰(EMI)屏蔽材料是有前景的,但也具有挑战性。受千费耶交替结构的启发,我们提出了导电层和磁性层交替组装的方法。以可持续竹纤维(BF)和可生物降解聚乳酸(PLA)为原料,分别用镀铜BF (Cu@BF)和镀铁BF (Fe@BF)与PLA复合制备磁性和导电层。通过磁性层和导电层交替叠加,然后进行热压,获得了具有“多(吸收-反射-重吸收)”结构的高电磁干扰SE和低r值生物质多层复合材料。研究了不同交替层(3/5/7/9层)的性能,发现层数、SE和r值之间存在线性相关关系。结果表明,增加交替层数可以很容易地将x波段的SE从45.02 dB(3层)调整到80.2 dB(9层),并将Rmin从0.40降低到0.25。此外,9层复合材料在1-18 GHz范围内的SE约为75 dB,同时实现了高效率、低反射率和宽带屏蔽。值得注意的是,其优异的导电性也提供了可靠的焦耳加热性能。复合材料的屏蔽和热特性突出了其在建筑和智能住宅供暖应用中的潜力。Composites Science and TechnologyMussel-Inspired Structure based CsPbBr3/Aramid Nanofiber Composite Film for Lightweight, Flexible and Superior X-ray ShieldingZizhan Guo, Zhaoqing Lu, Guoqiang Peng, Jingru Zhang, Li Hua, Fengfeng Jia, Jiayue Dong, Qijun Li, Haoxu Wang, Zhiwen Jindoi:10.1016/j.compscitech.2024.110700 基于贻贝启发结构的CsPbBr3/芳纶纳米纤维复合薄膜,用于轻质、柔性和卓越的x射线屏蔽Excessive exposure to X-rays risks human health and the proper functioning of precision instruments. Conventional materials have high atomic numbers, but their unsatisfactory mechanical properties hinder commercial application. Currently, X-ray shielding materials must fulfill the characteristics of high strength, lightweight, flexibility, high shielding efficiency, and low secondary radiation to alleviate urgent radiation risks. Here, this work introduces a mussel-inspired structure into the construction of the lightweight and flexible CsPbBr3/aramid nanofiber (ANF) composite films to enhance the ability of X-ray absorption. The CsPbBr3 provides effective X-ray shielding in millimeter thickness and addresses the challenge of absorption zone matching by containing both Cs and Pb elements. The interlayer reflection caused by the mussel-inspired structure increases the photon travel distance in the film, which synergizes with the absorption of X-rays by the elements, significantly improving shielding performance and weakening secondary radiation. The CsPbBr3/ANF composite film with 60 wt% CsPbBr3 content demonstrates robust tensile stress (57.6 MPa), lightweight (0.87 g/cm3), superior heat resistance, exceptional flexibility with a notable mass attenuation coefficient (58.2-65.6 cm2/g in the 20-70 kV range), which is much higher than Pb plate. Considering its comprehensive performance advantages, the CsPbBr3/ANF composite film significantly impacts the landscape of X-ray shielding.过度暴露于x射线会危及人体健康和精密仪器的正常工作。传统材料原子序数高,但力学性能不理想,阻碍了其商业应用。当前,x射线屏蔽材料必须具备高强度、轻量化、柔韧性、高屏蔽效率、低二次辐射等特点,才能缓解迫在眉睫的辐射风险。在这里,本研究将贻贝启发的结构引入到轻质柔性CsPbBr3/芳纶纳米纤维(ANF)复合薄膜的构建中,以增强x射线吸收能力。CsPbBr3在毫米厚度上提供了有效的x射线屏蔽,并通过同时含有Cs和Pb元素来解决吸收区匹配的挑战。贻贝启发结构引起的层间反射增加了光子在薄膜中的传播距离,与元件对x射线的吸收协同作用,显著提高了屏蔽性能,减弱了二次辐射。CsPbBr3含量为60 wt%的CsPbBr3/ANF复合薄膜具有抗拉应力(57.6 MPa)、重量轻(0.87 g/cm3)、耐热性好、柔韧性好、质量衰减系数显著(20-70 kV范围内58.2-65.6 cm2/g),远高于铅板。考虑到CsPbBr3/ANF复合薄膜的综合性能优势,其对x射线屏蔽的影响是显著的。Functionalization of Calcium-Deficient Nanohydroxyapatite Improves the Mechanical Properties of 3D Printed Biopolymer NanocompositesDibakar Mondal, Thomas L. Willettdoi:10.1016/j.compscitech.2024.110707 缺钙纳米羟基磷灰石功能化改善3D打印生物聚合物纳米复合材料的力学性能Agglomerations of nanoparticles in a polymer matrix can drastically reduce the mechanical properties of a polymer nanocomposite, especially its strength. The grafting of nanoparticle surfaces with suitable functional groups can provide improved dispersion and stronger interfacial bonding, improving the fracture resistance of the nanocomposite. In this study, calcium-deficient nanohydroxyapatite (nHA) particles were functionalized with an amino acid-based urethane methacrylate (lysine urethane methacrylate, LUM) and subsequently reacted with hydroxyethyl methacrylate. We mixed these functionalized nHA particles with resin, composed of methacrylated acrylated epoxidized soybean oil, methacrylated isosorbide, and triethylene glycol dimethacrylate, and 3D-printed nanocomposites using masked stereolithography. We hypothesized that the functionalized nanoparticles would enhance the mechanical performance of the 3D-printed nanocomposites due to the greater dispersion and stronger interface. Flexural, tensile, compression and Mode-I fracture toughness test specimens were fabricated using a mSLA printer and tested following ASTM standards. The LUM functionalization of nHA improved the dispersion and increased the viscosity of the uncured nanocomposite ink. The flexural fracture strength, yield strength, and mode-I fracture toughness values were increased by 10%, 30%, and 11%, respectively. The LUM improved the strength and fracture toughness by providing a stronger, more stable interface, resisting debonding between the matrix and particles, allowing for greater plastic deformation.纳米颗粒在聚合物基体中的聚集 会大大降低聚合物纳米复合材料的机械性能,尤其是其强度。通过在纳米粒子表面接枝合适的官能团,可以改善纳米复合材料的分散性,增强界面键合,从而提高纳米复合材料的抗断裂性能。在这项研究中,缺钙的纳米羟基磷灰石(nHA)颗粒被氨基酸基甲基丙烯酸氨基酯(赖氨酸甲基丙烯酸氨基酯,LUM)功能化,随后与甲基丙烯酸羟乙酯反应。我们将这些功能化的nHA颗粒与树脂混合,树脂由甲基丙烯酸酯、甲基丙烯酸酯环氧大豆油、甲基丙烯酸酯异山梨酯和三聚乙二醇二甲基丙烯酸酯组成,并使用屏蔽立体光刻技术3d打印纳米复合材料。我们假设功能化的纳米颗粒由于更大的分散性和更强的界面而增强了3d打印纳米复合材料的力学性能。使用mSLA打印机制作弯曲、拉伸、压缩和i型断裂韧性试样,并按照ASTM标准进行测试。nHA的LUM功能化改善了未固化纳米复合油墨的分散性,提高了其粘度。弯曲断裂强度、屈服强度和i型断裂韧性值分别提高了10%、30%和11%。LUM通过提供更强、更稳定的界面,抵抗基体和颗粒之间的脱粘,从而提高了强度和断裂韧性,允许更大的塑性变形。Three-dimensional woven structural electromagnetic composite metamaterial with lightweight, anti-delaminate and in-phase reflection propertiesWuzhou Li, Kun Zhang, Rui Pei, Fujun Xudoi:10.1016/j.compscitech.2024.110708 三维编织结构电磁复合超材料,具有轻质、抗分层、同相反射等特性Electromagnetic metamaterials are capable of tuning or controlling the transmission of the electromagnetic waves to realize high-performance microwave devices. However, the poor mechanical properties caused by the multi-layer structure limited its wide applications, especially in aircraft, satellites or high-speed vehicles. In this study, an electromagnetic metamaterial with in-phase reflection property was integrated into the three-dimensional (3D) woven composite to achieve the combination of unique electromagnetic properties and excellent mechanical properties on multi-functional composites. The 3D electromagnetic composite metamaterial was capable of reflecting electromagnetic waves from the antenna back lobe to the main lobe at 0° phase, resulting in the bandwidth of the test antenna increased from 0.6 GHz to 1.2 GHz, and the gain increased from 2.8 dB to 4.8 dB, an increase of 71.4%. Owing to the tight physical bonding of binder yarn, 3D electromagnetic composite metamaterial exhibited excellent anti-delaminate performance and stable electromagnetic properties in 28 J impact. The impact damage threshold energy of the 3D electromagnetic composite metamaterial was significantly increased from 10 J to 30 J.电磁超材料能够调节或控制电磁波的传输,从而实现高性能的微波器件。然而,由于多层结构导致的力学性能差,限制了其广泛应用,特别是在飞机、卫星或高速车辆上。本研究将一种具有同相反射特性的电磁超材料集成到三维编织复合材料中,实现了多功能复合材料独特的电磁性能与优异的力学性能的结合。三维电磁复合超材料能够在0°相位将天线后瓣的电磁波反射到主瓣,使测试天线的带宽从0.6 GHz提高到1.2 GHz,增益从2.8 dB提高到4.8 dB,提高了71.4%。由于粘结纱的紧密物理结合,三维电磁复合超材料在28j冲击下表现出优异的抗分层性能和稳定的电磁性能。三维电磁复合超材料的冲击损伤阈值能量由10 J显著提高到30 J。来源:复合材料力学仿真Composites FEM

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