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【新文速递】2024年2月15日固体力学SCI期刊最新文章

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今日更新:International Journal of Solids and Structures 3 篇,Journal of the Mechanics and Physics of Solids 1 篇,Thin-Walled Structures 1 篇

International Journal of Solids and Structures

Synergistic effect of interface and agglomeration on Young's modulus of graphene-polymer nanocomposites

Jie Wang, Liangfei Gong, Shangbin Xi, Chao Li, Yu Su, Lina Yang

doi:10.1016/j.ijsolstr.2024.112716

界面和团聚对石墨烯-聚合物纳米复合材料杨氏模量的协同效应

Filler agglomeration can severely hinder the stress transfer at the graphene-polymer interface, leading to deterioration of the interfacial properties and the overall mechanical performance of graphene nanocomposites. However, the correlation between the agglomeration and the interface effect was rarely investigated in the past. We hereby propose a novel and efficient approach to accurately obtain the effective Young’s modulus of graphene nanocomposites. We first introduced Cauchy's cumulative probability function to describe the progressive deterioration of the filler-matrix interface as the graphene’s volume concentration increases. Then, via the shear-lag approach, we developed a modified Halpin-Tsai model to take into account the effects of the agglomeration threshold, the filler-matrix interfacial moduli, and the surfactant treatment. The entire approach was validated by comparing the predicted results with five groups of experimental data. It was found that the interfacial properties are roughly linearly related to the matrix-to-nanofiller modulus ratio, which illustrates that a severer interfacial modulus mismatch leads to poorer interfacial bonding quality, and thus to a lower overall elastic modulus. The interfacial coefficient can also quantitatively characterize the enhancement effect of surfactant treatment. Besides, the synergistic effect of filler-matrix interface and filler agglomeration in the overall Young's modulus of composites was confirmed by comparison between theoretical and experimental results, and the latter becomes increasingly dominant as the graphene volume concentration increases.

填料团聚会严重阻碍石墨烯-聚合物界面的应力传递,导致界面性能和石墨烯纳米复合材料的整体机械性能下降。然而,过去很少有人研究团聚与界面效应之间的相关性。在此,我们提出了一种新颖、高效的方法来精确获得石墨烯纳米复合材料的有效杨氏模量。我们首先引入考奇累积概率函数来描述随着石墨烯体积浓度的增加,填料-基体界面逐渐恶化的过程。然后,通过剪切滞后方法,我们建立了一个改进的 Halpin-Tsai 模型,以考虑团聚阈值、填料-基质界面模量和表面活性剂处理的影响。通过将预测结果与五组实验数据进行比较,验证了整个方法。结果发现,界面特性与基体-纳米填料模量比大致呈线性关系,这说明界面模量失配越严重,界面结合质量越差,从而导致整体弹性模量越低。界面系数还可以定量表征表面活性剂处理的增强效果。此外,通过比较理论和实验结果,证实了填料-基体界面和填料团聚在复合材料整体杨氏模量中的协同效应,而且随着石墨烯体积浓度的增加,后者变得越来越主要。


Size-dependence of fracture processes in intact rocks

Aleksander Zubelewicz

doi:10.1016/j.ijsolstr.2024.112699

完整岩石断裂过程的尺寸依赖性

In brittle heterogeneous materials, the ultimate stress carries information on the material’s load-bearing capacity and, for this reason, this stress is an important engineering quantity. However, this stress is just a point in the sequence of stress–strain responses, each of them reflects the current state of damage in the material. Initially, isolated cracks grow, sense each other, and form multiple crack networks. The networks enable dilatational shear and facilitate further growth of damage. Large samples contain a broad spectrum of the crack-enabling defects and, therefore, the sample size becomes an irrelevant factor. However, when the defect population is limited, the damage process is constrained and, as a result, the peak stress is rising. According to the central limit theorem, the defect’s propensity for generating cracks should obey the rules of normal distribution. It turns out that the normal distribution of defects becomes a Weibull-like distribution of strength, where shape of the distribution is affected by the sample size and, also, is sensitive to hydrostatic pressure. The size-dependence of fracture processes is the main objective of the study.

在脆性异质材料中,极限应力包含了材料承载能力的信息,因此,极限应力是一个重要的工程量。然而,该应力只是应力-应变反应序列中的一个点,每个应力-应变反应序列都反映了材料当前的损坏状态。起初,孤立的裂缝会逐渐扩大,相互感应,并形成多个裂缝网络。这些裂纹网络能够产生扩张剪切,并促进损伤的进一步发展。大样本中包含了广泛的裂纹致能缺陷,因此样本大小成为一个无关紧要的因素。然而,当缺陷数量有限时,损伤过程受到限制,因此峰值应力不断上升。根据中心极限定理,缺陷产生裂纹的倾向应遵守正态分布规则。结果发现,缺陷的正态分布变成了类似于 Weibull 的强度分布,分布的形状受样本大小的影响,而且对静水压力也很敏感。研究的主要目标是断裂过程的尺寸依赖性。


Green’s functions for the isotropic planar relaxed micromorphic model — Concentrated force and concentrated couple

Panos Gourgiotis, Gianluca Rizzi, Peter Lewintan, Davide Bernardini, Adam Sky, Angela Madeo, Patrizio Neff

doi:10.1016/j.ijsolstr.2024.112700

各向同性平面松弛微观模型的格林函数 - 聚力和聚偶

We derive the Green’s functions (concentrated force and couple in an infinite space) for the isotropic planar relaxed micromorphic model. Since the relaxed micromorphic model particularises into the micro-stretch, Cosserat (micropolar), couple-stress, and linear elasticity model for certain choices of material parameters, we recover the fundamental solutions in all these cases.

我们推导出了各向同性平面松弛微形态模型的格林函数(无限空间中的集中力和耦合力)。由于松弛微形态模型在某些材料参数的选择下会具体化为微拉伸、Cosserat(微极性)、耦合应力和线性弹性模型,因此我们恢复了所有这些情况下的基本解。


Journal of the Mechanics and Physics of Solids

Anomalous tension–compression asymmetry in amorphous silicon: insights from atomistic simulations and elastoplastic constitutive modeling

Bin Ding, Liang Hu, Yuan Gao, Yuli Chen, Xiaoyan Li

doi:10.1016/j.jmps.2024.105575

非晶硅中反常的拉伸-压缩不对称现象:原子模拟和弹塑性结构建模的启示

Recent experiments observed an inherent, anomalous tension-compression (T-C) asymmetry with T>C in microscale amorphous silicon (a-Si), which is free of dominant microcracks or dislocations. However, quantifying the disordered structure of a-Si and correlating it with T-C asymmetry remains mysterious. Here, we first conduct a series of atomistic simulations to explore this anomaly in a-Si. Results reveal a positive correlation between cooling rate q and fraction of liquid-like phase ϕll, suggesting that higher cooling rates trap more atoms in liquid-like phase. Uniaxial tension and compression tests reveal that T-C asymmetry with T>C persists across all cooling rates, where the physical origin is attributed to variations in initial ϕll and its subsequent spatial and temporal evolutions during loading. A physics based, Mohr-Coloumb type elastoplastic constitutive model, determining cohesion c by the content of liquid-like component ϕll, successfully reproduces the observed anomalous T-C asymmetry and its dependence on the initial structure in a-Si. Furthermore, the degree of asymmetry tends to diminish with an increase in initial ϕll, a trend general to both amorphous Si and CuZr metallic glass (MG). While the contrasting atomic volumes of the liquid-like phase in a-Si and MG explain their differing T-C asymmetries, with a-Si exhibiting T>C and CuZr exhibiting T< C. These insights enhance the fundamental understanding of processing-structure-property relationship in amorphous materials, which benefits for designing amorphous with desired asymmetry in practical applications.

最近的实验观察到,在微尺度非晶硅(a-Si)中存在固有的反常拉伸-压缩(T-C)不对称现象,T>C。然而,量化非晶硅的无序结构并将其与 T-C 不对称相关联仍是一个谜。在此,我们首先进行了一系列原子模拟,以探索非晶硅中的这一反常现象。结果表明,冷却速率 q 与类液相的比例 ϕll 之间存在正相关,这表明较高的冷却速率会将更多原子捕获到类液相中。单轴拉伸和压缩测试表明,在所有冷却速率下,T-C 不对称与 T>C 都持续存在,其物理原因可归结为初始 ϕll 的变化及其随后在加载过程中的空间和时间演变。基于物理学的莫尔-科鲁姆(Mohr-Coloumb)型弹塑性构成模型,通过类液体成分ϕll的含量来确定内聚力c,成功地再现了观察到的反常T-C不对称现象及其与a-Si初始结构的依赖关系。此外,不对称的程度往往会随着初始 ϕll 的增加而减小,这是无定形硅和 CuZr 金属玻璃 (MG) 的普遍趋势。这些见解加深了人们对非晶材料的加工-结构-性能关系的基本认识,有利于在实际应用中设计出具有所需不对称性的非晶材料。


Thin-Walled Structures

Investigation on shock wave mitigation performance of modified polyurea coated helmet

Shengpeng Xue, Wenlong Xu, Cheng Wang, Xuefang Li, Shiyu Jia

doi:10.1016/j.tws.2024.111704

改性聚脲涂层头盔的冲击波减缓性能研究

In recent years, traumatic brain injury caused by explosive blast has become the leading cause of death in current military conflicts. However, as for the existing battlefield protection equipment, most of them focus on how to protect against infered injury caused by high-speed shrapnel. Accordingly, there is a lack of systematic research based on shock wave protection. In this work, a new modified polyurea is designed by adding SiO2 nanoparticles filler firstly. The effects of different proportions of SiO2 nanoparticles on the thermodynamic, quasi-static and dynamic mechanical properties of matrix are investigated. In recent years, traumatic brain injury caused by explosive blast has become the leading cause of death in current military conflicts. However, as for the existing battlefield protection equipment, most of them focus on how to protect against infered injury caused by high-speed shrapnel. Accordingly, there is a lack of systematic research based on shock wave protection.. The protection property of the material under shock wave is tested by the shock tube. Based on the above test results, the full-size shock wave protection test model of human head is developed, and the measurement of overpressure and acceleration peak of several key positions of head is realized. Finally, a new type of shock wave protection helmet is developed, which realizes efficient protection against shock wave. Under quasi-static loading conditions, the yield stress of PU-SiO2 decreases gradually with the increase of the content of SiO2 nanoparticles. Under high strain rate conditions, the strain hardening characteristic of PU-SiO2 increases gradually with the increase of SiO2 content. In the shock mitigation experiment, the peak overpressure and peak acceleration of shock wave decrease by 32.60% and 50.90%, respectively. The peak overpressure decreases again by 11.20% when the protective material is PU-SiO2, indicating that the SiO2 particles can improve the shock mitigation of PU. In the brain protection experiment, the changes in peak overpressure and peak acceleration at the three monitoring sites of the prefrontal lobe, posterior skull, and head reflect the degree of protection of the new material against shock wave.

近年来,爆炸造成的脑外伤已成为当前军事冲突中的主要死亡原因。然而,就现有的战场防护装备而言,它们大多侧重于如何防护高速弹片造成的脑损伤。因此,缺乏基于冲击波防护的系统研究。本研究首先通过添加 SiO2 纳米粒子填料设计了一种新型改性聚脲。研究了不同比例的 SiO2 纳米粒子对基体热力学、准静态和动态力学性能的影响。近年来,爆炸造成的脑外伤已成为当前军事冲突中的主要死亡原因。然而,就现有的战场防护装备而言,它们大多侧重于如何防护高速弹片造成的脑损伤。因此,目前还缺乏基于冲击波防护的系统研究。通过冲击管测试材料在冲击波作用下的防护性能。在上述试验结果的基础上,开发了全尺寸的人体头部冲击波防护试验模型,并实现了对头部几个关键位置的超压和加速度峰值的测量。最后,研制出一种新型冲击波防护头盔,实现了对冲击波的有效防护。在准静态加载条件下,随着纳米二氧化硅含量的增加,聚氨酯二氧化硅的屈服应力逐渐减小。在高应变速率条件下,随着 SiO2 含量的增加,PU-SiO2 的应变硬化特性逐渐增强。在减震实验中,冲击波的峰值过压和峰值加速度分别降低了 32.60% 和 50.90%。当保护材料为 PU-SiO2 时,过压峰值又降低了 11.20%,这表明 SiO2 颗粒可以改善 PU 的减震性能。在脑保护实验中,前额叶、后颅骨和头部三个监测点的峰值过压和峰值加速度的变化反映了新材料对冲击波的保护程度。



来源:复合材料力学仿真Composites FEM
ACTMechanicalSystem断裂复合材料ADSUG裂纹理论爆炸材料试验
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首次发布时间:2024-11-06
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【新文速递】2024年2月15日复合材料SCI期刊最新文章

今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 4 篇Composite StructuresAdjustable mechanical performances of 4D-printed shape memory lattice structuresYu Dong, Kaijuan Chen, Hu Liu, Jian Li, Zhihong Liang, Qianhua Kandoi:10.1016/j.compstruct.2024.1179714D 打印形状记忆晶格结构的可调机械性能Lattice structures are widely used due to their inherent advantages. With the development of smart devices, there is a growing demand for programmable, adjustable, and reconfigurable performances. However, a significant limitation of traditional lattice structures is that their shape, function, and performance cannot be changed after fabrication. In order to address this issue, we conducted experimental and simulated investigations on the shape memory effect, adjustable mechanical performances, and their deformation mechanism using the shape memory programming method. Two bending-dominated lattice structures, namely four curved bars lattice structure (FCBL) and sinusoidal wave horseshoe lattice structure (SWHL), were taken as examples. Results show that the deformation modes of both structures are switched from a bending-dominated mode to a stretching-dominated one after programming while exhibiting distinct bending sections. FCBL displays a &#39;C&#39; shape with one bending section, whereas SWHL exhibits an &#39;S&#39; shape with two bending sections. These deformation modes significantly enhance the tensile moduli by 480.9% (FCBL) and 1546% (SWHL), and change their Poisson’s ratio from -0.29 to 0.25 (FCBL) and -0.31 to 0.43 (SWHL), respectively. The modulus and Poisson’s ratio of FCBL and SWHL are well reproduced by the finite element modeling, providing a reference for designing the tunable mechanical performances of lattice structures.晶格结构因其固有的优势而得到广泛应用。随着智能设备的发展,人们对可编程、可调节和可重构性能的需求日益增长。然而,传统晶格结构的一个显著局限是其形状、功能和性能在制造后无法改变。为了解决这个问题,我们利用形状记忆编程方法对形状记忆效应、可调机械性能及其变形机制进行了实验和模拟研究。我们以两种以弯曲为主的晶格结构(即四弯杆晶格结构(FCBL)和正弦波马蹄形晶格结构(SWHL))为例进行了研究。结果表明,这两种结构的变形模式在编程后都从以弯曲为主的模式转换为以拉伸为主的模式,同时表现出明显的弯曲截面。FCBL 显示出具有一个弯曲截面的 &quot;C &quot;形,而 SWHL 则显示出具有两个弯曲截面的 &quot;S &quot;形。这些变形模式分别将拉伸模量大幅提高了 480.9%(FCBL)和 1546%(SWHL),并将泊松比从 -0.29 变为 0.25(FCBL)和 -0.31 变为 0.43(SWHL)。有限元建模很好地再现了 FCBL 和 SWHL 的模量和泊松比,为设计晶格结构的可调力学性能提供了参考。Composites Part A: Applied Science and ManufacturingCarbon fibre surface modification by plasma for enhanced polymeric composite performance: A reviewMaximilian Pitto, Holger Fiedler, Nam Kyeun Kim, Casparus Johannes Reinhard Verbeek, Tom David Allen, Simon Bickertondoi:10.1016/j.compositesa.2024.108087利用等离子体对碳纤维表面进行改性,以提高聚合物复合材料的性能:综述Energetic species in plasma have been used for four decades to functionalise or coat the hydrophobic and inert carbon fibre (CF) surface with the aim to enhance interface performance with polymeric matrices. To encourage a data-driven polymeric composite manufacturing process, this review communicates introductory plasma science, treatment methods, reaction mechanisms, fibre properties and composite performance. The digest on fibre properties after plasma modification informs the mechanical property enhancement of micro- and macro-scale fibre-reinforced polymeric composites. To reliably emulate CF plasma treatments for industrial polymeric composites manufacture, the bulk plasma must be characterised to produce the same reactive species in a non-identical plasma device. Integration of plasma diagnostics can spearhead interdisciplinary work to predict CF surface modification throughout the bundle and fabric, substituting the trial and error status quo. To justify the use of plasma, its environmental, social, and economic impact must be quantitatively compared to alternative fibre surface treatments.四十年来,等离子体中的高能物质一直被用来对疏水性和惰性碳纤维(CF)表面进行功能化或涂层处理,以提高其与聚合物基质的界面性能。为了鼓励以数据为导向的聚合物复合材料制造工艺,本综述介绍了等离子体科学、处理方法、反应机制、纤维特性和复合材料性能。等离子体改性后的纤维性能摘要为微观和宏观尺度纤维增强聚合物复合材料机械性能的提高提供了信息。要在工业聚合物复合材料制造中可靠地模拟 CF 等离子处理,必须对大块等离子体进行表征,以便在非相同的等离子体设备中产生相同的反应物种。整合等离子体诊断技术可以引领跨学科工作,预测整个纤维束和纤维织物的 CF 表面改性,从而取代反复试验的现状。为了证明使用等离子体的合理性,必须将其对环境、社会和经济的影响与其他纤维表面处理方法进行量化比较。A lightweight, flexible, and polarization-insensitive microwave absorbing honeycomb core using conductive losses in printed periodic patternSang Min, Won Jun Leedoi:10.1016/j.compositesa.2024.108089一种轻质、灵活、对偏振不敏感的微波吸收蜂窝芯,采用印刷周期图案中的导电损耗This study proposes a method for providing electromagnetic function by arranging patterns three-dimensionally on honeycomb partition walls. A conductive paste is thinly printed to fabricate a resistance component. To increase the current path induced by the incident electromagnetic waves, a rectangular pattern with an aspect ratio is used to further generate electromagnetic losses. Rectangular patterns are arranged alternately to ensure the homogeneity of the entire honeycomb medium. The proposed honeycomb achieved excellent absorption performance in the C, X, and Ku bands, regardless of the polarization. Simulations were used to show that the microwave-absorption performance of a honeycomb with a three-dimensional pattern could be estimated analytically. The obtained results were compared with those of other studies. The proposed honeycomb was effective in reducing the broadband monostatic radar cross section when applied to the leading edge of a wing box.本研究提出了一种通过在蜂窝隔墙上三维排列图案来提供电磁功能的方法。通过薄薄地印刷导电浆料来制造电阻元件。为了增加入射电磁波引起的电流路径,使用了具有高宽比的矩形图案,以进一步产生电磁损耗。矩形图案交替排列,以确保整个蜂窝介质的均匀性。所提出的蜂窝在 C、X 和 Ku 波段都实现了出色的吸收性能,与偏振无关。模拟结果表明,具有三维图案的蜂窝的微波吸收性能可以通过分析估算出来。所得结果与其他研究结果进行了比较。当应用于翼盒前缘时,所提出的蜂窝能有效减少宽带单静态雷达截面。Composites Part B: EngineeringCalcium crosslinked macroporous bacterial cellulose scaffolds with enhanced in situ mineralization and osteoinductivity for cranial bone regenerationXiaowei Xun, Yaqiang Li, Ming Ni, Yong Xu, Jiaxin Li, Dongxue Zhang, Guochang Chen, Haiyong Ao, Honglin Luo, Yizao Wan, Tao Yudoi:10.1016/j.compositesb.2024.111277用于颅骨再生的钙交联大孔细菌纤维素支架具有更强的原位矿化和骨诱导能力The inherent biological inertness and lack of three-dimensional (3D) macroporous structures greatly hinder the use of pristine bacterial cellulose (BC) as a tissue engineering scaffold for bone regeneration. To address this issue, we developed a simple and effective strategy to fabricate a BC-based scaffold with excellent bioactivity and macroporous structure by crosslinking short-cut BC nanofibers using Ca2+. The Ca2+ crosslinked macroporous BC scaffold (MPBC@Ca) presents better structural stability due to the enhanced cellulose hydration. Importantly, the Ca2+ on the surface of BC nanofibers can serve as an active nucleation site to accelerate the deposition of hydroxyapatite (HAp), which is beneficial for the construction of biomimetic bone tissue extracellular matrix (ECM) microenvironment. The HAp-deposited MPBC@Ca scaffolds (HAp-MPBC@Ca) with biomimetic ECM microenvironment have excellent cytocompatibility and enhanced osteogenic differentiation of stem cells in vitro. Furthermore, the results of in vivo tests revealed that the biomimetic ECM microenvironment HAp-MPBC@Ca scaffold has favorable osteoinductivity and accelerates cranial bone tissue regeneration. This study proposes a novel strategy to improve the bioactivity of BC and presents the great potential of biomimetic ECM microenvironment BC-based scaffold for repairing large cranial bone defects.原始细菌纤维素(BC)固有的生物惰性和缺乏三维(3D)大孔结构极大地阻碍了其作为组织工程支架用于骨再生。为解决这一问题,我们开发了一种简单有效的策略,通过使用 Ca2+ 交联短切 BC 纳米纤维,制造出一种具有优异生物活性和大孔结构的 BC 基支架。由于纤维素水合作用增强,Ca2+交联的大孔BC支架(MPBC@Ca)具有更好的结构稳定性。重要的是,BC 纳米纤维表面的 Ca2+ 可作为活性成核位点,加速羟基磷灰石(HAp)的沉积,有利于构建仿生骨组织细胞外基质(ECM)微环境。具有仿生 ECM 微环境的 HAp 沉积 MPBC@Ca 支架(HAp-MPBC@Ca)具有良好的细胞相容性,并能增强体外干细胞的成骨分化。此外,体内试验结果表明,仿生 ECM 微环境 HAp-MPBC@Ca 支架具有良好的骨诱导性,可加速颅骨组织再生。该研究提出了一种提高 BC 生物活性的新策略,并展示了基于生物仿生 ECM 微环境 BC 支架修复大面积颅骨缺损的巨大潜力。Composites Science and TechnologyMathematical study of the mechanical properties of NOL rings with different winding process parametersZesheng Huang, Wei Shen, Lifeng Chen, Lvtao Zhudoi:10.1016/j.compscitech.2024.110502 不同缠绕工艺参数下 NOL 环机械性能的数学研究This study investigates the impact of different winding tension parameters (40 N, 45 N, and 50 N) on the quality of fiber-wrapped products using the Navy Ordnance Laboratory (NOL) composite rings. Design Expert software was utilized to analyze the response surface of fiber winding process parameters, including winding tension, winding speed, and curing temperature, which significantly influence the mechanical properties of the fiber. Mathematical models were developed to understand the combined effects of these process parameters on the mechanical properties of NOL rings. Furthermore, a satisfaction function was employed to synthesize the two mechanical response variables into a comprehensive index for parameter optimization. Experimental validation was conducted to verify the reliability of the proposed design scheme.本研究使用海军军械实验室(NOL)的复合环,研究了不同缠绕张力参数(40 N、45 N 和 50 N)对纤维缠绕产品质量的影响。利用 Design Expert 软件分析了纤维缠绕工艺参数的响应面,包括缠绕张力、缠绕速度和固化温度,这些参数对纤维的机械性能有显著影响。通过建立数学模型,了解了这些工艺参数对 NOL 环机械性能的综合影响。此外,还采用了满意度函数,将两个机械响应变量综合成一个综合指标,用于参数优化。通过实验验证了所提设计方案的可靠性。Waste cotton stalks enhancing the impact and crystallization performances of polylactic acid/polypropylene composite with PP-g-mah compatibilizerJin Shang, Abdukaiyum Abdurexit, Ruxangul Jamal, Tursun Abdiryim, Xiong Liu, Fangfei Liu, Zhiwei Li, Yanqiang Zhou, Jin Wei, Xinsheng Tangdoi:10.1016/j.compscitech.2024.110485 废棉秆与 PP-g-mah 相容剂可提高聚乳酸/聚丙烯复合材料的抗冲击和结晶性能Although polymers based on polylactic acid (PLA) are considered by researchers as prime candidates for replacing traditional plastics, they are confronted with challenges including high production costs, limited thermal stability, and inferior impact resistance. In this study, novel composites with exceptional impact resistance, robust thermal stability, and satisfactory crystalline properties were fabricated by using PLA and polypropylene (PP) as raw materials, PP-g-MAH was employed as a compatibilizer to enhance the compatibility between the individual components. by adjusting the quantity of discarded cotton stalk fibers (CSF). The optimal mass ratio of CSF was determined to be 20%, resulting in a composite that exhibited a moderate increase of 56.31% in impact strength and a remarkable improvement of 23.05% in Vicat softening temperature. While the crystallinity was enhanced and the crystallization temperature (Tc) value decreased, the storage modulus also increased. Furthermore, the observed increase in storage modulus within the temperature range of 80 °C–100 °C was attributed to the influence of polymer cold crystallization. The hydrophobicity of the composite was enhanced. Significantly, this strategy can be extended to the application of other plant fibers, improving the crystalline properties of semi-crystalline polymers such as PLA and exemplifying the true ‘valorization of waste&#39; through the secondary utilization of discarded CSF.尽管以聚乳酸(PLA)为基础的聚合物被研究人员视为替代传统塑料的主要候选材料,但它们也面临着生产成本高、热稳定性有限和抗冲击性差等挑战。本研究以聚乳酸(PLA)和聚丙烯(PP)为原料,采用 PP-g-MAH 作为相容剂,通过调整废弃棉秆纤维(CSF)的用量,制备出具有优异抗冲击性、强大热稳定性和令人满意的结晶特性的新型复合材料。最终确定 CSF 的最佳质量比为 20%,使复合材料的冲击强度提高了 56.31%,维卡软化温度显著提高了 23.05%。在提高结晶度和降低结晶温度 (Tc) 值的同时,还提高了储存模量。此外,在 80 °C-100 °C 的温度范围内观察到的储存模量增加是由于聚合物冷结晶的影响。复合材料的疏水性得到了增强。值得注意的是,这一策略可扩展到其他植物纤维的应用,改善半结晶聚合物(如聚乳酸)的结晶特性,并通过对废弃 CSF 的二次利用体现真正的 &quot;废物利用&quot;。Flexible bandwidth-enhanced metamaterial absorbers with epoxy/graphene nanoplatelets-silver nanowire polymer composites as substratesM. Anjali, Raghunath Sahoo, Lincy Stephen, C.V. Krishnamurthy, V. Subramaniandoi:10.1016/j.compscitech.2024.110492 以环氧树脂/石墨烯纳米片-银纳米线聚合物复合材料为基材的柔性带宽增强超材料吸收器The realm of flexible devices has seen considerable advancement in recent technology due to their ability to bend and conform to particular shapes. Flexible metamaterial absorbers offer the advantage of combining the features of conventional metamaterials with the attributes of conformal systems, thereby opening new avenues in electromagnetic technology. This work involves the realization of flexible metamaterial absorbers with epoxy/graphene nanoplatelets-silver nanowire (GnP-AgNW) polymer composites as substrates; with a bandwidth enhancement achieved by incorporating losses in the substrate and combining resonances in the unit cell. A novel in-situ technique is employed to synthesize the nanohybrid GnP-AgNW (GA) with different weight percentages of AgNWs grown on GnP (GAx; x = 10, 15, 20 wt%). The dielectric measurements of the polymers showed that an increase in weight percentages of AgNWs in the composite enhanced the dielectric constant as well as losses of the polymer (εr՛: 7.7 to 8.8 and εr՛՛: 0.62 to 1.12). The numerical study on the designed flexible metamaterial absorbers with these substrates of thickness 1.4 mm showed a maximum absorptivity of 99% with a bandwidth (having absorption &gt;90%) varying between 1.2 and 1.86 GHz. The experimental measurements on the fabricated metamaterial absorber were found to match the simulation results closely. The polymer composites demonstrated in this work are attractive candidates as substrates for metamaterial absorbers for conformal applications. This paper approaches the problem of bandwidth enhancement of metamaterial absorbers by material engineering along with the resonant structure optimization leading to a synergetic effect in the properties of absorber.柔性器件能够弯曲并符合特定形状,因此在最近的技术领域取得了长足的进步。柔性超材料吸波材料具有将传统超材料的特性与保形系统的属性相结合的优势,从而为电磁技术开辟了新的道路。这项研究以环氧树脂/石墨烯纳米片-银纳米线(GnP-AgNW)聚合物复合材料为基材,实现了柔性超材料吸波材料;通过在基材中加入损耗和在单元格中结合共振实现了带宽增强。我们采用了一种新颖的原位技术来合成纳米杂化 GnP-AgNW(GA),在 GnP 上生长不同重量百分比的 AgNW(GAx;x = 10、15、20 wt%)。聚合物的介电测量结果表明,复合材料中 AgNWs 重量百分比的增加提高了聚合物的介电常数和损耗(εr՛:7.7 至 8.8;εr՛՛:0.62 至 1.12)。对使用这些厚度为 1.4 毫米的基底设计的柔性超材料吸波材料进行的数值研究表明,其最大吸收率为 99%,带宽(吸收率大于 90%)在 1.2 至 1.86 千兆赫之间。对制作的超材料吸收器的实验测量结果与模拟结果非常吻合。这项工作中展示的聚合物复合材料是具有吸引力的超材料吸收器基材,可用于保形应用。本文通过材料工程和谐振结构优化来解决超材料吸收器的带宽增强问题,从而在吸收器的性能方面产生协同效应。Trans-scale analysis of 3D braided composites with voids based on micro-CT imaging and unsupervised machine learningXinyi Song, Jin Zhou, Di Zhang, Shenghao Zhang, Pei Li, Longteng Bai, Xiaohui Yang, Feiping Du, Xuefeng Chen, Zhongwei Guan, Wesley J. Cantwelldoi:10.1016/j.compscitech.2024.110494 基于显微 CT 成像和无监督机器学习的空隙三维编织复合材料跨尺度分析Voids are unavoidable during the manufacturing of 3D braided composites. This study proposes an unsupervised machine learning method combined with micro-computed tomography (micro-CT) scanning and a progressive damage analysis to analyze defects in these composites at a trans-scale level. The method enables the creation of real multiscale models and the determination of the porosity in both the intra-yarn (1.52 %) and inter-yarn (5.04 %) planes. Here, the unsupervised machine learning method is introduced in a trans-scale damage analysis to reduce calculation dimensions and to visualize the clustering data. A user-defined material subroutine (UMAT) is also developed to implement the trans-scale damage model. The experimental validation of the simulation results demonstrates the effective trans-scale damage analysis, showing the predominant pull-shear damage in the yarns, which is primarily located at the interfaces both between the yarns and between the yarns and the matrix. Finally, based on the scanned geometric data the degradation in modulus and strength of 3D braided composites with porosity is studied.在三维编织复合材料的制造过程中,空洞是不可避免的。本研究提出了一种无监督机器学习方法,结合微型计算机断层扫描(micro-CT)和渐进式损伤分析,在跨尺度水平上分析这些复合材料中的缺陷。该方法可创建真实的多尺度模型,并确定纱内(1.52%)和纱间(5.04%)平面的孔隙率。在此,我们在跨尺度损伤分析中引入了无监督机器学习方法,以减少计算维数并实现聚类数据的可视化。此外,还开发了用户自定义材料子程序(UMAT)来实现跨尺度损伤模型。模拟结果的实验验证证明了跨尺度损伤分析的有效性,显示了纱线中主要的拉剪损伤,这种损伤主要位于纱线之间以及纱线与基体之间的界面。最后,根据扫描的几何数据,研究了带有孔隙率的三维编织复合材料的模量和强度退化情况。来源:复合材料力学仿真Composites FEM

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