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【新文速递】2024年6月26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 2 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇

International Journal of Solids and Structures

Computational homogenization of the elastic properties of polycrystalline fcc metals within Mindlin’s second strain-gradient theory

V. Bagherpour, M.R. Delfani

doi:10.1016/j.ijsolstr.2024.112942

明德林第二应变梯度理论中多晶 fcc 金属弹性特性的计算均质化

The lack of interest in Mindlin’s second strain-gradient theory, despite its success in characterizing various phenomena for which there is no explanation in the classical elasticity, is predominantly due to the numerous higher-order elastic constants involved therein. As an attempt to overcome this shortcoming, a computational homogenization method for determining such elastic constants of polycrystalline face-centered cubic (fcc) metals is proposed in the present study. In this homogenization method, using the Voigt-type averaging scheme, a polycrystalline material is modeled by an isotropic aggregate of randomly oriented single crystals without accounting for the grain size effect and the complexities due to grain boundaries and junctions Subsequently, analytical expressions for the strain energy due to certain modes of loading are determined, and molecular simulations of a few fcc metals under such modes of loading are performed. Then, by fitting the corresponding analytical expressions to the results obtained from these simulations, the effective elastic constants and consequently the effective characteristic lengths of the fcc metals in their polycrystalline form are determined. Moreover, the free-surface-induced reconstruction in a thin layer of a solid is addressed both analytically and by molecular simulations, as a result of which the effective moduli of cohesion of the fcc metals in their polycrystalline form are calculated. In addition, the complete set of conditions for the positive-definiteness of the strain–energy-density function of isotropic materials within the adopted theory is derived, and subsequently a discussion of whether or not the numerical values obtained for the effective elastic moduli of the polycrystalline fcc metals satisfy such conditions is provided.

尽管明德林的第二应变梯度理论成功地描述了经典弹性理论无法解释的各种现象,但人们对它缺乏兴趣,这主要是由于其中涉及大量高阶弹性常数。为了克服这一缺陷,本研究提出了一种计算均质化方法,用于确定多晶面心立方(fcc)金属的此类弹性常数。在这种均质化方法中,使用 Voigt 型平均方案,将多晶材料建模为随机取向单晶的各向同性集 合体,而不考虑晶粒大小效应以及晶界和交界引起的复杂性。然后,通过将相应的分析表达式与这些模拟结果进行拟合,确定了多晶态 fcc 金属的有效弹性常数和有效特征长度。此外,还通过分析和分子模拟解决了固体薄层中的自由表面诱导重构问题,并由此计算出了多晶形式 fcc 金属的有效内聚模量。此外,还推导出在所采用的理论中各向同性材料应变能量密度函数正定义的整套条件,并随后讨论了所获得的多晶 fcc 金属有效弹性模量数值是否满足这些条件。


A machine learning assisted multifidelity modelling methodology to predict 3D stresses in the vicinity of design features in composite structures

Omar A.I. Azeem, Silvestre T. Pinho

doi:10.1016/j.ijsolstr.2024.112946

机器学习辅助多保真度建模方法,用于预测复合材料结构设计特征附近的三维应力

Multifidelity global–local finite element (FE) analyses are typically used to predict damage initiation hotspots around repetitive design features in large composite structures, such as composite airframes. We propose the use of machine learning (ML) methods to accelerate these analyses. We demonstrate this ML assisted framework for the stress analysis of a hole in plate feature in an aerospace C-spar structure. To enable this framework, we develop the following original features: a computationally efficient sampling scheme; a work-equivalent boundary condition homogenisation scheme; a volume averaged ply-by-ply stress approach; and a sequential long-short term memory neural network reformulated from a time basis to a stacking sequence basis with further bi-directionality customisation. Overall, we show that the developed method results in high-accuracy prediction of 3D stresses, with over two orders of magnitude reduction in modelling and simulation time compared to FE analyses.

多保真度全局-局部有限元(FE)分析通常用于预测大型复合材料结构(如复合材料机身)中重复设计特征周围的损伤起始热点。我们建议使用机器学习(ML)方法来加速这些分析。我们演示了这一 ML 辅助框架,用于航空航天 C 型支柱结构中板孔特征的应力分析。为了实现这一框架,我们开发了以下原创功能:计算效率高的采样方案;功当量边界条件均质化方案;体积平均逐层应力方法;以及从时间基础到堆叠序列基础的顺序长短期记忆神经网络,并进一步进行了双向定制。总之,我们表明所开发的方法可实现高精度的三维应力预测,与 FE 分析相比,建模和模拟时间减少了两个数量级以上。


Journal of the Mechanics and Physics of Solids

Wrinkle-free membranes through spatioselective exposure

Guangliang Qi, Heng Gao, Jianyue Wang, Guozhong Zhao, Dzianis Marmysh, Zhan Kang, Kexi Zhu, Ming Li

doi:10.1016/j.jmps.2024.105752

通过空间选择性曝光实现无皱薄膜

The extreme flexibility-induced wrinkling significantly hampers the promising engineering applications of membranes, while the existing wrinkling-suppression approaches have challenges for area loss, weight increase and interfacial delamination. Here we propose a facile wrinkle-free technique that enables stiffness modulation through spatioselective ultraviolet (UV) exposure, regulates stress distribution to eliminate compressive stresses and achieves robust wrinkle-free membranes. A small-deformation theoretical model with the Marguerre function is implemented to evaluate the wrinkling capability of a stiffness-modulated membrane, the non-gradient particle swarm optimization (PSO) algorithm is performed to obtain the optimal material distribution, and the related robust wrinkle-free performance is verified through both finite-deformation post-buckling analyses and physical experiments. In addition, an empirical wrinkle-free solution is also given without the requirement of excessive optimization. This wrinkle-free approach, with neither area loss, weight increase nor interfacial delamination, provides useful guidance for the research on wrinkle-free membranes.

由极端柔性引起的皱纹严重阻碍了膜的工程应用前景,而现有的皱纹抑制方法又面临着面积损失、重量增加和界面分层的挑战。在这里,我们提出了一种简便的无皱技术,通过空间选择性紫外线(UV)照射实现刚度调节,调节应力分布以消除压应力,从而实现坚固的无皱膜。该研究利用马盖尔函数的小变形理论模型来评估刚度调制膜的起皱能力,并采用非梯度粒子群优化(PSO)算法来获得最佳材料分布,通过有限变形后屈曲分析和物理实验来验证相关的稳健无皱性能。此外,还给出了无需过度优化的经验无皱解决方案。这种无皱方法既不会造成面积损失、重量增加,也不会造成界面分层,为无皱膜的研究提供了有益的指导。


Mechanics of Materials

A mechanistic interpretation of Nelson curves for PVP failures under high temperature hydrogen attack

Dong Han, Yanfei Gao, Phillip E. Loya, Michael Swindeman, Jorge Penso, Zhili Feng

doi:10.1016/j.mechmat.2024.105079

高温氢气侵蚀下 PVP 失效的纳尔逊曲线机理解析

As an empirically established design criterion, Nelson curves that relate the service temperature and the allowable hydrogen partial pressure have been developed and utilized for more than sixty years in pressure vessels and piping (PVP) safety design. Despite a relatively clear thermodynamic understanding of the high-temperature-hydrogen-attack (HTHA) problem, the detailed fracture process on the microstructural length scales, however, remains elusive, and a quantitative assessment of the PVP lifetime under HTHA from the available creep fracture dataset is still not possible. This work develops a microstructure-informed and micromechanics-based model by incorporating a synergy between hydrogen transport and intergranular-cavity-based fracture process. Based on the available creep lifetime data of C-0.5Mo steels, we are able to calibrate material constitutive parameters, and then conduct nonlinear finite element simulations that reveal a real-time stress-induced hydrogen diffusional transport along grain boundaries, coupled with a microstructure-explicit failure process, from which Nelson curves can be computed. Such failure analyses allow us to delineate two distinct regimes on the Nelson curves, i.e., dislocation-creep-controlled or grain boundary diffusion-assisted cavity growth. More importantly, we found that a small change of the pipe thickness and applied stresses can significantly shift these lifetime curves. However, these two parameters are usually not provided in Nelson curves, thus limiting their usage in material selection and safety design. This discrepancy can clearly be mitigated by extensive parametric studies from our micromechanical modeling/simulation framework.

纳尔逊曲线是根据经验确定的设计标准,它将使用温度和允许的氢分压联系起来,在压力容器和管道 (PVP) 安全设计中已经开发和使用了六十多年。尽管对高温氢气侵蚀(HTHA)问题有了相对清晰的热力学认识,但微观结构长度尺度上的详细断裂过程仍然难以捉摸,而且仍然无法根据现有的蠕变断裂数据集对高温氢气侵蚀下的 PVP 寿命进行定量评估。本研究结合氢传输和基于晶间空腔的断裂过程之间的协同作用,建立了一个基于微观结构和微观力学的模型。根据现有的 C-0.5Mo 钢蠕变寿命数据,我们能够校准材料构成参数,然后进行非线性有限元模拟,以揭示沿晶界的实时应力诱导氢扩散传输,并结合微观结构明确的失效过程,从而计算出纳尔逊曲线。通过这种失效分析,我们可以在纳尔逊曲线上划分出两种截然不同的状态,即位错-蠕变控制或晶界扩散辅助空穴生长。更重要的是,我们发现管材厚度和外加应力的微小变化都会显著改变这些寿命曲线。然而,纳尔逊曲线通常不提供这两个参数,因此限制了它们在材料选择和安全设计中的应用。通过我们的微机械建模/模拟框架进行广泛的参数研究,这种差异显然可以得到缓解。


International Journal of Plasticity

Time-resolved evolution of the deformation mechanisms in a TRIP/TWIP Fe50Mn30Co10Cr10 high entropy during tensile loading probed with synchrotron X-ray diffraction

J.G. Lopes, J. Shen, E. Maawad, P. Agrawal, N. Schell, R.S. Mishra, J.P. Oliveira

doi:10.1016/j.ijplas.2024.104048

利用同步辐射 X 射线衍射探测 TRIP/TWIP Fe50Mn30Co10Cr10 高熵在拉伸加载过程中变形机制的时间分辨演变

The present research focuses on analyzing the deformation mechanisms associated with tensile loading of the Fe50Mn30Co10Cr10 high entropy alloy (HEA) using synchrotron x-ray diffraction (SXRD). This novel material is comprised by two major phases: γ-FCC and ε-HCP, where transformation induced plasticity (TRIP) effectively transforms the first into the latter, upon the application of an external stress. However, the presence of thermally stable ε-HCP prior to loading will also influence the deformation mechanism of the material during mechanical solicitation. As such, here we investigate the activation of different strain accommodation mechanisms and the consequent microstructural evolution. Four stages were identified in the mechanical response of this novel HEA, where the TRIP and the twinning induced plasticity (TWIP) deformation modes are the main events granting this HEA its outstanding properties. Such sequence of events allows to evidence the effectiveness of the collaboration between the transformative capability of the γ-FCC phase and the work hardening potential of the ε-HCP phase. This analysis is performed via quantitative and qualitative analysis of the SXRD data, allowing also to investigate the response behavior of specific crystallographic planes to the increasing stress throughout the experiment.

本研究的重点是利用同步辐射 X 射线衍射 (SXRD) 分析与 Fe50Mn30Co10Cr10 高熵合金 (HEA) 拉伸负载相关的变形机制。这种新型材料由两个主要相组成:γ-FCC 和 ε-HCP,在施加外部应力时,转化诱导塑性(TRIP)可有效地将前者转化为后者。然而,加载前存在热稳定的 ε-HCP 也会影响材料在机械激励过程中的变形机制。因此,我们在此研究了不同应变容纳机制的激活以及随之而来的微结构演变。在这种新型 HEA 的机械响应中发现了四个阶段,其中 TRIP 和孪生诱导塑性(TWIP)变形模式是赋予这种 HEA 杰出性能的主要事件。这一系列事件证明了γ-FCC 相的转化能力与ε-HCP 相的加工硬化潜力之间的协同效应。这种分析是通过对 SXRD 数据进行定量和定性分析来完成的,同时还可以研究特定晶面在整个实验过程中对应力增加的响应行为。


Thin-Walled Structures

An advanced design diagram of stiffened plate subjected to combined in-plane and lateral loads considering initial deflection effects

Zhuo Wang, Xiangshao Kong, Weiguo Wu, Do Kyun Kim

doi:10.1016/j.tws.2024.112144

考虑初始挠度效应的平面和侧向联合载荷加劲板高级设计图

This study presents an advanced methodology for stiffened plates subjected to combined in-plane longitudinal compression and lateral loads. The proposed methodology is based on comprehensive numerical parametric analyses, and it utilises newly developed design curves for the lateral pressure limit and tailored empirical formulae for stiffened plates to increase the precision of ship structural designs. Plate–stiffener combination (PSC) members are used for the limit state analysis, which introduces various positions and initial deflection shapes specific to the PSC models. Local buckling-shaped deflections of the stiffener web are also incorporated into the analysis, which closely mirrors the real-world welding conditions of stiffened plates and provides deeper insight into their load-bearing capacities. These findings highlight the importance of accurately selecting the positions and initial deflections of stiffeners in PSC-based analyses to ensure that structural predictions are safe and reliable. The proposed method is grounded in conservative PSC models and represents a significant advancement in ship structural design in terms of safety and practicality.

本研究针对承受平面纵向压缩和横向荷载的加劲板提出了一种先进的方法。所提出的方法基于全面的数值参数分析,并利用新开发的横向压力极限设计曲线和为加劲板量身定制的经验公式来提高船舶结构设计的精度。极限状态分析使用了板-加劲板组合(PSC)构件,引入了 PSC 模型特有的各种位置和初始挠度形状。加劲板腹板的局部屈曲形挠度也被纳入分析中,这密切反映了加劲板的实际焊接条件,并提供了对其承载能力的更深入了解。这些发现强调了在基于 PSC 的分析中准确选择加劲板位置和初始挠度的重要性,以确保结构预测安全可靠。所提出的方法以保守的 PSC 模型为基础,在安全性和实用性方面代表了船舶结构设计的重大进步。




来源:复合材料力学仿真Composites FEM
ACTMechanicalDeformFidelity断裂复合材料非线性航空航天船舶ADS焊接理论材料控制管道
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首次发布时间:2024-11-21
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【新文速递】2024年6月1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 Science and Technology 7 篇Composite StructuresEasy manufacturing constraint based topology optimization of dual-scale and dual-constituent lattice metastructure with thermal dimensional stabilityZihao Yang, Yongcun Zhang, Shutian Liudoi:10.1016/j.compstruct.2024.118247基于易于制造约束的具有热尺寸稳定性的双尺度双组份晶格元结构拓扑优化Thermal dimensional stability (TDS) is a crucial issue in the development of high-end industry equipment and precision instruments that work in fluctuating thermal environments. To endow meta-structures with high load-carrying capacity and TDS functionality simultaneously, this paper proposes a topology optimization framework to optimize the topologies of lattice meta-structures at macroscopic structural and microscopic material scales concurrently. An important feature of the current optimization model is the introduction of a material concentration distribution (MCD) constraint to reduce the number of dual-constituent interfaces (DIs), which enables the easy manufacturing of the optimized structures because an additional fabrication process is required for the connection of heterogeneous lattice members. Designs for two dual-scale TDS structures, potentially employed for satellite payload platforms and the supporting structure of space telescopes, are completed. Compared with mono-scale TDS structures, the dual-scale schemes exhibit superior structural performances due to the opening of the dual-scale design space. Numerical experiments are performed to validate the ultra-low structural thermal deformations of the optimized TDS structures with values of 0.0743 μm/℃ and 0.153 μm/℃. Furthermore, the imposition of the MCD constraint significantly reduces the number of DIs from 38 to 10 within a lattice cell, enabling the easy assembly of the demonstrative 3D printing dual-constituent samples.热尺寸稳定性(TDS)是开发在波动热环境下工作的高端工业设备和精密仪器的关键问题。为了使晶格元结构同时具有高承载能力和TDS功能,本文提出了一种拓扑优化框架,在宏观结构尺度和微观材料尺度上同时优化晶格元结构的拓扑结构。当前优化模型的一个重要特征是引入了材料浓度分布(MCD)约束,以减少双组分界面(DIs)的数量,这使得优化结构的制造变得容易,因为异质晶格成员的连接需要额外的制造工艺。完成了两种双尺度TDS结构的设计,可能用于卫星有效载荷平台和空间望远镜的支撑结构。由于双尺度设计空间的开放,与单尺度TDS结构相比,双尺度方案表现出更优越的结构性能。通过数值实验验证了优化后的TDS结构的超低结构热变形值分别为0.0743 μm/℃和0.153 μm/℃。此外,MCD约束的施加显着将晶格单元内的DIs数量从38个减少到10个,从而使演示性3D打印双组分样品的组装变得容易。Composites Part A: Applied Science and ManufacturingLimitations of composite strength theory for predicting the ultimate strengths of layered 3D printing polymersGonghe Zhang, Xiaodong Zheng, Qinglin Wang, Yinxu Ni, Fenghua Liu, Kai Zhao, Luoyu Roy Xudoi:10.1016/j.compositesa.2024.108288 复合材料强度理论在预测层状3D打印聚合物极限强度方面的局限性Composite laminates and 3D printing materials both have layered structures. Although the Tsai–Hill composite strength criterion is useful for predicting the strengths of some 3D printing polymers made with fused filament fabrication (FFF), our experimental and theoretical studies showed that this criterion has some limitations in predicting the strengths of other 3D printing polymers. In this study, a new quadratic strength criterion was employed to predict a conservative lower bound for the strengths of polymers made with FFF and selective laser sintering (SLS). The printing surface angles of the printing specimens ranged from 0° to 90°. Interestingly, the scope of this study unexpectedly widened from strength research to fracture mechanics research because dynamic crack branching was observed in some SLS specimens (printing surface angles ranged from 0° to 75°) under static tension—a novel phenomenon among 3D printing materials. Crack branching not only followed previous crack branching rules, such as rules on the crack speed and energy release but also presented new challenges for dynamic fracture mechanics theory.复合层压板和3D打印材料都具有层状结构。虽然Tsai-Hill复合材料强度准则可用于预测某些用熔丝制造(FFF)制成的3D打印聚合物的强度,但我们的实验和理论研究表明,该准则在预测其他3D打印聚合物的强度方面存在一定的局限性。在这项研究中,采用一个新的二次强度准则来预测FFF和选择性激光烧结(SLS)聚合物强度的保守下界。印刷试样的印刷表面角度范围为0°~ 90°。有趣的是,这项研究的范围出乎意料地从强度研究扩大到断裂力学研究,因为在一些SLS样品(打印表面角度从0°到75°)中观察到静态张力下的动态裂纹分支,这是3D打印材料中的一种新现象。裂纹分支不仅遵循原有的裂纹分支规律,如裂纹速度和能量释放规律,而且对动态断裂力学理论提出了新的挑战。Effect of long-time annealing at high temperature on the microstructure and mechanical properties of different types of SiC fibersShuang Wu, Yanzi Gou, Yu Xiang, Weifeng Kang, Yongshou Wang, Quzhi Song, Nana Xu, Yingde Wangdoi:10.1016/j.compositesa.2024.108291高温长时间退火对不同类型SiC纤维显微组织和力学性能的影响SiC fibers play a crucial role in ceramic-matrix composites due to their excellent high-temperature resistance. To analyze the high temperature stability of different types of SiC fibers, this work investigated three typical SiC fibers (KD-II, KD-S, KD-SA) after being annealed at 1600 °C and 1800 °C for 1 h ∼ 200 h, respectively. For annealing at 1600 °C, the decomposition of the SiCxOy phase and grain growth were the main reasons for strength degradation in KD-II and KD-S fibers, while the KD-SA fiber maintained good thermal stability due to its large grain size. For long-time annealing at 1800 °C, obvious Si sublimation in the three fibers, leading to appearance of skin-core structure, resulted in obvious strength decline. This phenomenon was more pronounced over 1800 °C. These results in this work could be helpful guidance for the preparation of higher performance SiC fibers and SiCf/SiC composites.SiC纤维以其优异的耐高温性能在陶瓷基复合材料中起着至关重要的作用。为了分析不同类型SiC纤维的高温稳定性,本工作研究了三种典型的SiC纤维(KD-II, KD-S, KD-SA)在1600 °C和1800 °C分别退火1 h ~ 200 h后的高温稳定性。1600 ℃退火时,KD-II和KD-S纤维强度下降的主要原因是SiCxOy相的分解和晶粒长大,而KD-SA纤维由于晶粒尺寸大,保持了良好的热稳定性。在1800 ℃下长时间退火,三种纤维中Si明显升华,出现皮芯结构,强度下降明显。这种现象在1800° °C以上更为明显。研究结果对制备高性能SiC纤维和SiCf/SiC复合材料具有指导意义。Composites Science and TechnologyTemperature- and rate-dependent tensile behaviour of unidirectional carbon/polyamide-6 composite under off-axis loading with oblique tabsDaniele Finazzi, Marco Bertani, Wim Van Paepegemdoi:10.1016/j.compscitech.2024.110685 斜片离轴载荷下单向碳/聚酰胺-6复合材料的温度和速率相关拉伸行为Unidirectional carbon/polyamide-6 (CPA6) is a thermoplastic composite with attractive properties for many industrial applications. However, shortage of experimental data may hinder the development of reliable material models. This paper is the first to provide a complete dataset for the tensile behaviour of unidirectional CPA6, including the longitudinal, transverse, in-plane shear, and off-axis response, at different temperatures and (quasi-static) strain rates. The oblique end tab design, already proven in the literature for off-axis testing of composites at room temperature, was successfully extended to the elevated temperature of 120 °C. The use of cardboard tabs and fast-curing adhesive greatly simplified the tab manufacturing and application for all the combinations of fibre angles, temperatures and strain rates. Digital image correlation (DIC) was performed through the window of the temperature chamber to verify the homogeneous strain field produced by the oblique tabs. The in-plane shear behaviour was extracted from the off-axis tests, allowing to estimate the shear modulus and shear strength. Finally, the robustness of the experimental results generated in this study was demonstrated with well-established analytical models that could excellently predict the elastic modulus, Poisson’s ratio, and failure stress at different fibre angles.单向碳/聚酰胺-6 (CPA6)是一种热塑性复合材料,具有许多工业应用的吸引力。然而,实验数据的缺乏可能会阻碍可靠材料模型的发展。本文首次提供了单向CPA6拉伸行为的完整数据集,包括在不同温度和(准静态)应变速率下的纵向、横向、面内剪切和离轴响应。在室温下的复合材料离轴测试中,斜端标签设计已经在文献中得到验证,并成功地扩展到120°C的高温。纸板标签和快速固化粘合剂的使用大大简化了标签的制造和应用,适用于纤维角度、温度和应变率的所有组合。通过温度室窗口进行数字图像相关(DIC),验证斜片产生的均匀应变场。从离轴试验中提取平面内剪切行为,从而可以估计剪切模量和剪切强度。最后,通过完善的分析模型证明了本研究实验结果的鲁棒性,该模型可以很好地预测不同纤维角度下的弹性模量、泊松比和破坏应力。A three-dimensional viscoelastic-viscoplastic and viscodamage constitutive model for unidirectional fibre-reinforced polymer laminatesI.R. Cózar, P. Maimí, E.V. González, P.P. Camanho, F. Oterodoi:10.1016/j.compscitech.2024.110634 单向纤维增强聚合物层合板的三维粘弹粘塑性和粘损伤本构模型A novel 3D viscoelastic-viscoplastic and viscodamage constitutive model is proposed to predict the viscous effects due to dynamic loading conditions of unidirectional carbon fibre-reinforced polymer laminates at the meso-scale level. The present model is developed under continuum damage mechanics and the thermodynamics of irreversible processes framework. The viscoelastic response is modelled using the generalised Maxwell model, while an overstress model is employed to address the viscoplastic strain. The onset of the viscodamage mechanisms is based on experimental expressions, and their propagation is defined as a function of the corresponding fracture toughness. The mechanical response of the present constitutive model under pure longitudinal shear loading conditions at different strain rates is presented. The higher the strain rate is, the stiffer the responses in the viscoelastic and viscoplastic regions. Additionally, the onset of viscodamage increases with higher strain rates. Off-axis compressive experimental data at two different strain rates are employed to demonstrate the capabilities of the present model with good predictions being obtained.提出了一种新的三维粘弹-粘塑性和粘损伤本构模型,用于在细观尺度上预测单向碳纤维增强聚合物层合板在动态加载条件下的粘滞效应。该模型是在连续损伤力学和不可逆过程热力学框架下建立的。粘弹性响应采用广义Maxwell模型,粘塑性应变采用超应力模型。粘损伤机制的开始是基于实验表达式的,其扩展被定义为相应断裂韧性的函数。给出了本构模型在不同应变率下纯纵向剪切加载条件下的力学响应。应变率越高,粘弹区和粘塑性区的响应越硬。此外,粘胶损伤的发生随着应变速率的增加而增加。采用两种不同应变速率下的离轴压缩实验数据来证明该模型的能力,并获得了良好的预测结果。Multimodal Electrohydrodynamic Jet Printing-Based Microstructure-Sensitized Flexible Pressure SensorHongji Guo, Wuhao Zou, Tianming Zhao, Jiawen Liang, Ya Zhong, Peilin Zhou, Ying Zhao, Lianqing Liu, Haibo Yudoi:10.1016/j.compscitech.2024.110686 基于多模态电流体动力喷射打印的微结构敏化柔性压力传感器Surface modification with micro/nanostructures is a common approach for enhancing the performance of flexible pressure sensors. However, the current fabrication of the singular functionality of instruments and redundancy of processes increase the complexity of the sensor manufacturing process. In this study, we developed a multilayer microstructure-enhanced flexible capacitive pressure sensor based on the multimodal electrohydrodynamic jet (E-jet) printing technology. The experimental results demonstrate that the sensors incorporating the microstructure-sensitized electrode layer and the polyvinyl alcohol/graphene/polydimethylsiloxane dielectric layer exhibit the following characteristics: high sensitivity (0.3139 kPa-1/0-2 kPa), low limit of detection (∼100 mg), and stable performance even after 10,000 cycles. Moreover, microstructure-enhanced sensors have considerable potential for human behavior detection, such as detecting fluid flow, tracking muscle movements, and measuring pulse rates. Finally, microstructure-enhanced sensors fabricated using the E-jet printing method present a novel approach for designing sensitized structures in capacitive pressure sensors.微纳结构表面改性是提高柔性压力传感器性能的常用方法。然而,目前制造的单一功能的仪器和冗余的过程增加了传感器制造过程的复杂性。在这项研究中,我们开发了一种基于多模态电流体动力射流(E-jet)打印技术的多层微结构增强柔性电容压力传感器。实验结果表明,包含微结构敏化电极层和聚乙烯醇/石墨烯/聚二甲基硅氧烷介电层的传感器具有以下特点:高灵敏度(0.3139 kPa-1/0-2 kPa),低检测限(~ 100 mg),即使在10,000次循环后性能稳定。此外,微结构增强传感器在人类行为检测方面具有相当大的潜力,例如检测流体流动、跟踪肌肉运动和测量脉搏率。最后,利用E-jet打印技术制备的微结构增强传感器为电容式压力传感器的敏化结构设计提供了一种新的方法。Closed loop recycling of electrically damaged meta-aramid papers with high electrical insulation and mechanical strengthFangcheng Lv, Lvqian Fu, Qibin Wang, Kaixuan Sun, Rui Yang, Sidi Fan, Xiang Yudoi:10.1016/j.compscitech.2024.110688 具有高电绝缘性和机械强度的电损坏间位芳纶纸的闭环回收High-performance aramid papers are ideal insulating materials in the electric industry, due to their superior mechanical strength and insulation capabilities. However, when subjected to prolonged high-voltage and high-power operations, these papers are prone to electrical damage, such as breakdown or corona aging. Unfortunately, most damaged aramid papers are viewed as mere waste, discarded through landfill or other unsustainable disposal methods. It is not only contrary to circular economy principles but also poses a significant environmental threat due to the potential for pollution. Herein, a closed-loop recycling strategy is proposed that efficiently and effectively reclaims electrically damaged meta-aramid papers. Using the DMAc/LiCl deprotonation system, waste aramid papers are completely decomposed into molecular chains, exposing carbon residues resulting from electrical breakdown. These carbon residues are removed through a step-by-step purification process. A reprotonation treatment is then applied to regenerate new meta-aramid papers by reforming the intermolecular hydrogen bonds. This approach not only fully restores the original honeycomb-like structure but also ensures the crystallization and hydrogen bond content, maintaining both electrical and mechanical properties at above 90% of their original values. Notably, our recycling method is also compatible with aramid-based composites, achieving exceptional recycling efficiency.高性能芳纶纸具有优异的机械强度和绝缘性能,是电气工业中理想的绝缘材料。然而,当经受长时间的高压和大功率操作时,这些纸张容易发生电气损坏,例如击穿或电晕老化。不幸的是,大多数受损的芳纶纸被视为纯粹的废物,通过填埋或其他不可持续的处理方法被丢弃。它不仅违背了循环经济原则,而且由于潜在的污染,对环境构成了重大威胁。本文提出了一种闭环回收策略,可以高效、有效地回收电损伤的间位芳纶纸。使用DMAc/LiCl去质子化系统,废弃芳纶纸被完全分解成分子链,暴露出电击穿产生的碳残基。这些碳残留物通过一步一步的净化过程被去除。然后通过重组分子间氢键,应用再生处理再生新的间芳纶纸。这种方法不仅完全恢复了原始的蜂窝状结构,而且保证了结晶和氢键含量,使电学和力学性能保持在原始值的90%以上。值得注意的是,我们的回收方法也与芳纶基复合材料兼容,实现了卓越的回收效率。Construction of a cross-bedded tea polyphenol delivery structure in ultrahigh molecular weight polyethylene against bacteria for joint replacementYue Ren, Jia-Cheng Lv, Shao-Peng Zhao, Haojie Fu, Zhao-Bo Sun, Lingli Li, Shishu Huang, Jia-Zhuang Xu, Zhong-Ming Lidoi:10.1016/j.compscitech.2024.110689 超高分子量聚乙烯抗细菌交叉层状茶多酚传递结构的构建The high jeopardy of prosthesis joint infection demands urgent development of an in-situ drug delivery joint material, while achieving sustained antimicrobial activity remains a challenge. Herein, a sedimentary rock-like “cross-bedded” drug delivery structure was constructed in the ultrahigh molecular weight polyethylene (UHMWPE) joint material. Epigallocatechin gallate (EGCG), a representative tea polyphenol, was employed as a substitute of antibiotics with antimicrobial activity. Delivery pathways composed of EGCG were highly aligned and cross-bedded with the UHMWPE matrix under the strong flow field offered by solid-state extrusion. The EGCG pathlength was thus increased in a longitudinal section, attenuating burst release and prolonging the release time of EGCG. The release of EGCG in the “cross-bedded” structure was restricted to a low concentration at the initial stage yet subsequently extended 2∼3 times compared to that in the massive structure. The prolonged release ratio is nearly equivalent to the EGCG pathlength increment as calculated via a simplified mathematical model. The quantitative relationships between release behavior and antimicrobial performance proved that the cross-bedded structure was efficient in maintaining sustained antimicrobial activity. These findings offer a paradigm to achieve sustained drug therapy in UHMWPE joint material, which is constructive for treating prosthetic bacterial infections in clinical trials.假体关节感染的高危险性迫切需要原位给药关节材料的开发,而实现持续的抗菌活性仍然是一个挑战。本文在超高分子量聚乙烯(UHMWPE)接头材料中构建了类似沉积岩的“交叉层状”给药结构。表没食子儿茶素没食子酸酯(EGCG)是一种具有代表性的茶多酚,可作为抗菌药物的替代品。在固态挤压提供的强流场下,EGCG组成的传递途径与UHMWPE基质高度排列并交叉层状。因此,EGCG的路径长度在纵剖面上增加,减缓了爆发释放,延长了EGCG的释放时间。在“交叉层状”结构中,EGCG的释放在初始阶段被限制在低浓度,但随后比在块状结构中延长了2 ~ 3倍。通过简化的数学模型计算,延长释放比几乎等于EGCG路径长度增量。释放行为与抗菌性能之间的定量关系证明了交层结构在维持持续抗菌活性方面是有效的。这些发现为实现UHMWPE关节材料的持续药物治疗提供了一个范例,这对临床试验中治疗假体细菌感染具有建设性意义。Multifunctional polyimide/boron nitride nanosheet/Ti3C2Tx MXene composite film with three-dimensional conductive network for integrated thermal conductive, electromagnetic interference shielding, and Joule heating performancesDongya Guo, Binzhe Tan, Xiaojie Jiang, Guangyu Gao, Yu Lindoi:10.1016/j.compscitech.2024.110690 具有三维导电网络的多功能聚酰亚胺/氮化硼纳米片/Ti3C2Tx MXene复合薄膜,具有综合导热、电磁干扰屏蔽和焦耳加热性能With the demand for further miniaturization and higher frequency operation of electronic devices, polymer films with high thermal conductivity and electromagnetic interference (EMI) shielding effectiveness (SE) are urgently required. Herein, polyimide (PI)/boron nitride nanosheets (BNNS) aerogels with oriented porous structure are fabricated by unidirectional-freezing and freeze-drying methods. Subsequently, hierarchical PI/BNNS/Ti3C2Tx composite films with consecutively electrically and thermally conductive networks are successfully prepared via a unidirectional PI/BNNS aerogels-assisted immersion and hot-pressing strategy. Owing to the three-dimensional conductive dual networks of BNNS and Ti3C2Tx, the composite film exhibits excellent thermal conductivity with the maximum in-plane value of 4.73 W/(m·K), increased by 456% compared to pure PI film. Moreover, the conductive network of Ti3C2Tx is conducive to the excellent EMI shielding performance, endowing the PI/BNNS/Ti3C2Tx composite film with an outstanding EMI SE value of 49.2 dB at 8.2 GHz with a low MXene content of 6 wt% and thickness of 300 μm. Furthermore, the composite film shows the superior Joule heating performance with fast thermal response and sufficient reliability. Therefore, the resulting composite film exhibits excellent thermal conductive, EMI shielding and Joule heating performance, which enables the potential application of multifunctional composites for thermal management and EMI shielding.随着电子器件进一步小型化和高频率工作的要求,迫切需要具有高导热性和屏蔽电磁干扰(EMI)效能的聚合物薄膜。本文采用单向冷冻和冷冻干燥的方法制备了具有定向多孔结构的聚酰亚胺/氮化硼纳米片气凝胶。随后,通过单向PI/BNNS气凝胶辅助浸渍和热压策略,成功制备了具有连续导电和导热网络的分层PI/BNNS/Ti3C2Tx复合薄膜。由于BNNS和Ti3C2Tx的三维双导网络,复合膜具有优异的导热性能,最大面内值为4.73 W/(m·K),比纯PI膜提高了456%。此外,Ti3C2Tx的导电网络有利于优异的EMI屏蔽性能,使得PI/BNNS/Ti3C2Tx复合膜在8.2 GHz时具有49.2 dB的优异EMI SE值,MXene含量低至6 wt%,厚度为300 μm。复合膜具有良好的焦耳加热性能,热响应快,可靠性高。因此,所得到的复合膜具有优异的导热、电磁干扰屏蔽和焦耳加热性能,这使得多功能复合材料在热管理和电磁干扰屏蔽方面的潜在应用成为可能。Thickness effect on ballistic impact behavior of hybrid carbon/Kevlar compositesSai Zhao, Jia Huang, Junchao Cao, Yong Chen, Xiaobiao Zuo, Kai Yi, Chao Zhangdoi:10.1016/j.compscitech.2024.110692 厚度对混杂碳/凯夫拉复合材料弹道冲击性能的影响Carbon fiber composites have poor impact resistance that constrains their wider application in advanced engineering structures, and hybridizing carbon fibers with Kevlar fibers is an effective method to enhance their impact resistance. The ballistic impact resistance can be optimized through regulating the hybridization layout and hybrid ratio, which requires systematically exploration on the inherent failure mechanism. In this work, the ballistic impact behavior of hybrid carbon/Kevlar fiber reinforced epoxy laminates against flat-head projectile are systematically investigated. Hybrid specimens with different thicknesses and hybridization ratios are designed, tested and compared. The results reveal the strong correlation between thickness and ballistic impact performance. When laminates are relatively thin, Kevlar fiber layers at the back surface impart superior impact resistance. In contrast, the opposite result is observed when the thickness is beyond a threshold value. With an increase in the Kevlar fiber hybridization ratio, this threshold value will occur in thinner laminates. Further analysis indicates that this phenomenon is related to a shear plugging effect that dominates the different modes of impact failure.碳纤维复合材料抗冲击性能较差,制约了其在先进工程结构中的广泛应用,碳纤维与凯夫拉纤维杂交是增强其抗冲击性能的有效方法。通过调节混合布局和混合比例来优化其抗弹道冲击性能,这需要对其内在失效机理进行系统的探索。本文系统地研究了复合碳纤维/芳纶增强环氧复合材料对平头弹丸的弹道冲击性能。设计、试验和比较了不同厚度和杂交比的杂交试样。结果表明,厚度与弹道冲击性能之间存在很强的相关性。当层压板相对较薄时,背面的凯夫拉纤维层具有优异的抗冲击性。相反,当厚度超过阈值时,观察到相反的结果。随着凯夫拉纤维杂化比的增加,该阈值将出现在较薄的层压板中。进一步分析表明,这种现象与剪切堵塞效应有关,剪切堵塞效应在不同的冲击破坏模式中占主导地位。来源:复合材料力学仿真Composites FEM

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