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【新文速递】2024年11月21日复合材料SCI期刊最新文章

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今日更新:Composite Structures 4 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 1 篇

Composite Structures

Experimental and numerical investigation on the size effect of interlaminar shear strength for thick composites

Ziqing Hao, Xiaoyu Wang, Hongjun Ke, Gaojian Wei, George Kardomateas, Liu Liu

doi:10.1016/j.compstruct.2024.118710

厚复合材料层间剪切强度尺寸效应的实验与数值研究

The study investigates the variation of interlaminar shear properties for unidirectional glass fiber reinforced polymer (GFRP) composites with different thickness using the short-beam shear (SBS) test in conjunction with DIC. To verify the scaling principle and clarify possible mechanisms of the interlaminar shear strength size effect, the quantitative parameters for characterizing randomly distributed irregular voids are proposed. It is seen that the variation of probability for void characteristics with thickness is one of the mechanisms for the interlaminar shear strength size effect. Furthermore, a micromechanical representative volume element (RVE) model with randomly distributed irregular voids is developed for numerical verication. The analysis indicates that the weakest link is related to not only the void size but also the void irregularity and void concentration. The void concentration has a pronounced negative impact on shear strength due to the intersection of the microcracks around the voids.

采用短束剪切(SBS)试验结合DIC研究了不同厚度的单向玻璃纤维增强聚合物(GFRP)复合材料层间剪切性能的变化。为了验证层间剪切强度尺寸效应的标化原理,阐明层间剪切强度尺寸效应的可能机制,提出了表征随机分布不规则空洞的定量参数。可见,孔隙特征的概率随厚度的变化是层间剪切强度尺寸效应的机制之一。在此基础上,建立了随机分布不规则孔洞的微力学代表性体积元模型进行数值验证。分析表明,最薄弱环节不仅与孔洞大小有关,还与孔洞的不规则性和孔洞浓度有关。由于孔洞周围的微裂纹相交,孔洞浓度对抗剪强度有显著的负影响。


Fatigue life prognosis of composite structures using a transferable deep reinforcement learning-based approach

Cheng Liu, Yan Chen, Xuebing Xu

doi:10.1016/j.compstruct.2024.118727

基于可转移深度强化学习方法的复合材料结构疲劳寿命预测

Accurately predicting the remaining useful life (RUL) of Carbon Fiber Reinforced Polymer (CFRP) structures under fatigue loading is crucial for enhancing safety and minimizing maintenance costs, especially in industries like aerospace and automotive. However, the complex physical properties of CFRP, combined with the scarcity of real-world damage-condition data, make this task extremely challenging. To address these issues, we propose a novel deep reinforcement learning (DRL)-based prognostic method. Our approach integrates Denoising Autoencoder (DAE) and Transformer architectures to construct a powerful DRL Policy Network, capable of extracting high-quality features from X-ray records to capture the subtle progression of damage in CFRP structures. Additionally, we employ advanced data augmentation techniques to overcome the limitations of small datasets and introduce transfer learning to extend the model’s generalization capabilities across different CFRP structures. By pre-training on diverse CFRP datasets, our model achieves highly accurate RUL predictions for new designs, even with minimal labeled data from the target structure. Experimental results demonstrate that our method significantly outperforms current state-of-the-art (SOTA) techniques, offering a scalable, efficient, and practical solution for the real-world monitoring and prognostics of CFRP structures, with broad potential for industrial applications.

准确预测碳纤维增强聚合物(CFRP)结构在疲劳载荷下的剩余使用寿命(RUL)对于提高安全性和最小化维护成本至关重要,特别是在航空航天和汽车等行业。然而,CFRP复杂的物理特性,加上现实世界损伤状况数据的稀缺性,使得这项任务极具挑战性。为了解决这些问题,我们提出了一种新的基于深度强化学习(DRL)的预测方法。我们的方法集成了去噪自动编码器(DAE)和变压器架构,构建了一个强大的DRL策略网络,能够从x射线记录中提取高质量特征,以捕捉CFRP结构损伤的微妙进展。此外,我们采用先进的数据增强技术来克服小数据集的局限性,并引入迁移学习来扩展模型在不同CFRP结构中的泛化能力。通过对不同碳纤维增强材料数据集进行预训练,我们的模型即使使用目标结构的最小标记数据,也能对新设计实现高度准确的RUL预测。实验结果表明,我们的方法明显优于当前最先进的(SOTA)技术,为CFRP结构的实际监测和预测提供了可扩展、高效和实用的解决方案,具有广泛的工业应用潜力。


Numerical investigation of composite metal foams using substructure techniques

Márió Kovács, Balázs Pere, Imre Norbert Orbulov

doi:10.1016/j.compstruct.2024.118731

基于子结构技术的复合金属泡沫数值研究

An accurate description of the mechanical behaviour of inhomogeneous, anisotropic composite materials, such as metal matrix syntactic foams (MMSFs), is a challenging task. This paper is based on the so-called substructure technique, which has never been used for the mechanical modelling of metal foams or MMSFs. Using this method, a finite element model with low computational requirements but still modelling inhomogeneous properties can be constructed that reproduces the results of laboratory measurements with high accuracy. In all cases, the tests presented in this paper are limited to the linearly elastic phase. As the most common investigation of MMSFs is the compression test, this study considers only this loading case. A more detailed discussion of the stress analysis of MMSFs is given at the end of this work. A potential cause of 45° crack planes during compression tests and the evolution of stresses as a function of space-filling are also investigated.

准确描述非均匀、各向异性复合材料(如金属基复合泡沫(mmsf))的力学行为是一项具有挑战性的任务。本文基于所谓的子结构技术,该技术从未用于金属泡沫或mmsf的力学建模。使用该方法,可以构建计算量低但仍能模拟非均匀性的有限元模型,以高精度再现实验室测量结果。在所有情况下,本文中提出的试验仅限于线弹性阶段。由于对mmsf最常见的调查是压缩试验,因此本研究只考虑这种荷载情况。在本文的最后,对mmsf的应力分析进行了更详细的讨论。在压缩试验中45°裂纹面的潜在原因和应力随空间填充的演化也进行了研究。


Experimental study on the electrical conductivity and strain sensitivity of fibre-reinforced thermoplastic for structural health monitoring

Ciampaglia, S. Roccia, R. Ciardiello

doi:10.1016/j.compstruct.2024.118729

结构健康监测用纤维增强热塑性塑料的电导率和应变敏感性试验研究

This experimental study explores the mechanical, electrical, and piezometric characteristics of conductive thermoplastic polymers reinforced with short carbon and glass fibres. The work investigates how the local anisotropy induced during the manufacturing injection process impacts the properties of the composite. Tensile tests showed that the material orientation respect to the injection flow direction significantly affects the mechanical properties due to the alignment of the fibres with the injection flow, as shown with the microscopy analysis. Contrarily, electrically conductive tests showed that the influence of the orientation on the conductive properties of the material is negligible. The study also unveils the difference in the surface and bulk conductivity with the increasing distance of the electrodes. Tensile tests with in-situ electrical measurements were conducted to assess strain sensitivity by correlating stress–strain curves with changes in material conductivity. The results demonstrate the predominant impact of local anisotropy on piezometric response. Finally, a model for the piezometric response of the material is proposed and applied for the structural health monitoring of a tensile specimen, revealing its ability to detect local damage before final failure. This application underscores the prognostic capabilities of this material and its potential significance in ensuring structural integrity.

本实验研究探讨了用短碳和玻璃纤维增强的导电热塑性聚合物的机械、电气和测压特性。研究了在制造注射过程中引起的局部各向异性对复合材料性能的影响。拉伸测试表明,由于纤维与注射流动的对齐,材料的取向相对于注射流动方向显著影响机械性能,这与显微镜分析结果一致。相反,导电测试表明,取向对材料导电性能的影响可以忽略不计。该研究还揭示了随着电极距离的增加,表面和体积电导率的差异。通过原位电测量进行拉伸试验,通过将应力-应变曲线与材料电导率的变化相关联来评估应变敏感性。结果表明,局部各向异性对压敏响应的主要影响。最后,提出了材料的压电响应模型,并将其应用于拉伸试件的结构健康监测,揭示了其在最终破坏之前检测局部损伤的能力。这种应用强调了这种材料的预测能力及其在确保结构完整性方面的潜在意义。


Composites Part A: Applied Science and Manufacturing

A new ISO standard for the experimental characterization of in-plane permeability of fibrous reinforcements

D. May, S.G. Advani, M. Duhovic, A. Endruweit, E. Fauster, A. George, P.-J. Liotier, C. Lira, S.V. Lomov, M.F. Pucci, S. Schmeer, D. Abliz, D.C. Berg, C. Binetruy, M. Bodaghi, S. Comas-Cardona, M. Etchells, Q. Govignon, A. Koorevaar, V. Michaud, C.H. Park, R. Schubnel, P. Sousa, R. Ravel, M. Rouhi, E. Syerko, R. Umer, M. Vollmer, A. Yong

doi:10.1016/j.compositesa.2024.108592

纤维增强材料面内渗透性实验表征的ISO新标准

During Liquid Composite Molding, a fibrous reinforcement is impregnated with liquid resin. Process design requires knowledge of the reinforcement permeability for fluid flow, but until recently, there has been no standard available for its measurement. In 2023, following decades of benchmarking activities and a standardization project, an ISO standard for the experimental characterization of in-plane permeability of fibrous reinforcements for liquid composite molding was finally published. It focuses on the experimental characterization of unsaturated in-plane permeability and specifies the requirements for test equipment, methods and data analysis. Given the deficiency of standardized procedures within the composites industry, this paper intends to provide an example of the steps towards standardization and summarizes lessons learned. It illustrates the research milestones that led to the establishment of the standard, promotes the standard by detailing its general content and notable features and finally gives explanations and reasoning behind the developed guidelines.

在液态复合成型过程中,纤维增强物被液态树脂浸渍。工艺设计需要了解流体流动的增强渗透率,但直到最近,还没有可用于其测量的标准。2023年,经过数十年的基准测试活动和标准化项目,最终发布了用于液体复合材料成型的纤维增强材料平面内渗透率实验表征的ISO标准。重点介绍了非饱和面内渗透率的实验表征,并对试验设备、方法和数据分析提出了要求。鉴于复合材料行业中标准化程序的不足,本文打算提供一个迈向标准化的步骤示例并总结经验教训。它说明了导致标准建立的研究里程碑,通过详细说明其一般内容和显着特征来促进标准,最后给出了开发指南背后的解释和推理。


“Totally-additive-manufacturing”-functionalized carbon fiber-reinforced polymer composites with an ultrasensitive self-sensing network

Qingqing Wang, Ming Ma, Anchalee Duongthipthewa, Wanglinhan Zhang, Yanfeng Lang, Guojie Luo, Yiyin Su, Menglong Liu, Limin Zhou, Zhongqing Su

doi:10.1016/j.compositesa.2024.108596

 

“全增材制造”——具有超灵敏自传感网络的功能化碳纤维增强聚合物复合材料

With recent advancement in multi-material additive manufacturing, we develop a new manufacturing framework driven by the concept of “totally-additive-manufacturing”, to functionalize carbon fiber-reinforced polymer (CFRP) composites with the capacity of in situ, real-time integrity monitoring through service lifespan. It is composed of (i) fused deposition modeling-printed continuous carbon fibers, (ii) nylon-based matrix and electrical insulation layers, and (iii) an ultrathin, aerosol jet printing-fabricated piezoresistive sensing network made with graphene/cellulose nanocrystals nanocomposite ink, as well as the silver ink-based electric circuits. Interfaces among different components are interrogated via micromorphological and interlaminar shear strength tests, affirming adequate interfacial bonding warranted by the “totally-additive-manufacturing”. Thus-functionalized CFRP composites exhibit ultrahigh sensitivity to quasi-static strains induced by cyclic loads and ultrasonic elastic perturbation up to 200 kHz. This study underscores the concept of “totally-additive-manufacturing” for fabricating functionalized composites, seamlessly merging structural functionality with self-sensing of structural health status, but not downgrading the original structural integrity.

随着多材料增材制造的最新进展,我们开发了一种新的制造框架,以“全增材制造”的概念为驱动,使碳纤维增强聚合物(CFRP)复合材料具有原位、实时完整性监测和使用寿命的能力。它由(i)熔融沉积建模印刷连续碳纤维,(ii)尼龙基基体和电绝缘层,以及(iii)由石墨烯/纤维素纳米晶体纳米复合墨水制成的超薄气溶胶喷射印刷制造的压阻传感网络,以及银墨水基电路组成。通过微观形态和层间剪切强度测试,研究了不同组件之间的界面,确认了“完全增材制造”所保证的足够的界面粘合。因此,功能化CFRP复合材料对循环载荷和高达200 kHz的超声弹性扰动引起的准静态应变具有超高的敏感性。本研究强调了“全增材制造”的概念,用于制造功能化复合材料,将结构功能与结构健康状态的自我感知无缝融合,但不降低原有结构的完整性。


Composites Part B: Engineering

The immiscible W/Cu composites with heterostructures and excellent bond strength prepared by additively manufactured transient liquid-phase direct bonding: Experiments and simulations

Zhangping Hu, Yanan Zhao, Xiaohong Zhan, Jiawei Xu, Zongqing Ma

doi:10.1016/j.compositesb.2024.111981

 

增材瞬态液相直接键合制备具有异质结构和优异键合强度的非混相W/Cu复合材料:实验与模拟

Immiscible metallic composites are a class of promising materials with unique physical properties and excellent comprehensive mechanical properties. However, obtaining high-performance immiscible composites through solid-phase direct/indirect bonding processes has been a great challenge due to the difficulty of bonding and high melting-point difference in immiscible metal/alloy systems, especially immiscible W-Cu systems with the highest positive formation heat and high melting point variations. This work confirms that high-strength bonding between immiscible and highly melting-point-differentiated metals can be achieved under highly non-equilibrium transient liquid-phase direct bonding. Specifically, not only the construction of transient liquid-phase interfaces without interlayers between W and CuCrZr was realized under highly non-equilibrium conditions of melting/solidification and extremely high cooling rates brought about by the laser powder bed fusion additive manufacturing, but also the surface nanocrystallization was simultaneously obtained at the interface, forming the W/CuCrZr composite material with heterogeneous grain size structure. The W/CuCrZr composite materials possessed a gradient microstructure of micron-sized equiaxed tungsten grains, nano tungsten grains and columnar Cu grains in sequence as well as having excellent interfacial bonding strength and a high effective bonding area ratio. By combining experiments and molecular dynamics simulations, it was clarified that the introduction of crystal defects and the formation of tungsten nanograins promote the diffusion of immiscible W and Cu and achieve strong bonding. Our work provides a new strategy and in-depth view into the fabrication of excellent-performance composite materials between immiscible metals/alloys.

非混相金属复合材料具有独特的物理性能和优异的综合力学性能,是一类很有发展前途的材料。然而,由于非混相金属/合金体系,特别是具有最高正形成热和高熔点变化的非混相W-Cu体系的键合困难和高熔点差异,通过固相直接/间接键合工艺获得高性能的非混相复合材料一直是一个巨大的挑战。本研究证实,在高度非平衡的瞬态液相直接键合下,非混相和高熔点分化金属之间可以实现高强度的键合。具体而言,在激光粉末床熔融增材制造带来的高度非平衡的熔化/凝固条件和极高的冷却速率下,不仅实现了W与CuCrZr之间无中间层的瞬态液相界面的构建,而且在界面处同时实现了表面纳米化,形成了具有非均匀晶粒尺寸结构的W/CuCrZr复合材料。W/CuCrZr复合材料具有微米级等轴钨晶、纳米级钨晶和柱状铜晶依次排列的梯度微观结构,具有优异的界面结合强度和较高的有效结合面积比。通过实验和分子动力学模拟相结合,阐明了晶体缺陷的引入和钨纳米颗粒的形成促进了不混相W和Cu的扩散,实现了强键合。我们的工作为制备高性能的非混相金属/合金复合材料提供了新的策略和深入的视角。


Composites Science and Technology

Enhance the piezoelectricity of poly(vinylidene fluoride) through co-crystal with polycaprolactone

Zhiwei Ye, Juan Yi, Yibo Zhang, Chuanxi Xiong

doi:10.1016/j.compscitech.2024.110973

 

通过与聚己内酯共晶提高聚偏氟乙烯的压电性

The strategies of solid solution and doping have been well-established obtaining high piezoelectric ceramics, achieving a significant increase in the piezoelectric coefficient. Nevertheless, there is a paucity of research investigating this strategy in polymer piezoelectric materials. In this work, we present a novel approach to co-crystal formation between polycaprolactone (PCL) and poly(vinylidene fluoride) (PVDF), which markedly enhances the piezoelectricity of PVDF. The formation of a co-crystal results in a notable reduction in the crystal size of PVDF, an increase in the interface between the crystalline and amorphous regions, and the directional arrangement of dipoles under an electric field. The piezoelectric coefficient of the 3% PCL/PVDF film is approximately twice that of the commercial PVDF film (22.0 pC/N), and the sensor device exhibits favorable linear sensing characteristics. The present study proposes a novel strategy for the development of films with exceptional piezoelectric properties.

采用固溶和掺杂的方法制备高压电陶瓷,实现了压电系数的显著提高。然而,在聚合物压电材料中研究这种策略的研究很少。在这项工作中,我们提出了一种在聚己内酯(PCL)和聚偏氟乙烯(PVDF)之间形成共晶的新方法,该方法显著提高了PVDF的压电性。共晶的形成使PVDF的晶体尺寸明显减小,晶界与非晶界之间的界面增大,偶极子在电场作用下的定向排列。3% PCL/PVDF薄膜的压电系数约为商用PVDF薄膜(22.0 pC/N)的两倍,传感器器件表现出良好的线性传感特性。本研究提出了一种开发具有特殊压电性能薄膜的新策略。



来源:复合材料力学仿真Composites FEM
ACTMechanicalAdditiveSystemSTEPS疲劳复合材料化学电路航空航天汽车增材ECAD裂纹电场材料
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【新文速递】2024年11月19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 2 篇,Mechanics of Materials 1 篇,Thin-Walled Structures 2 篇International Journal of Solids and StructuresAn accurate and efficient method based on the dynamic stiffness matrix for analyzing wave propagation in defective lattice structuresB.W. Yan, Q. Gaodoi:10.1016/j.ijsolstr.2024.113147基于动刚度矩阵的缺陷点阵结构波传播分析方法In this study, we present an efficient and accurate method for analyzing wave propagation in lattice structures with periodic defects, which are composed of three-dimensional (3D) unit cells arranged infinitely in two or three directions, with defects existing periodically along the directions of the arrangement. The unit cell is composed of 3D beams, and the dynamic stiffness formulation of the 3D beam is developed by combining the Timoshenko-Ehrenfest, Rayleigh-Love and torsion theories. Based on the dynamic stiffness matrix, any number or order of natural frequencies of defective lattice structures can be calculated accurately and efficiently using the Wittrick-Williams algorithm. By combining it with the Bloch theorem, the proposed method can be used to calculate the dispersion curves of lattice structures with periodic defects. The accuracy and efficiency of the proposed method are demonstrated through numerical examples. Additionally, the effects of periodic defects in the lattice structures on the bandgap are analyzed.在这项研究中,我们提出了一种有效而准确的方法来分析具有周期性缺陷的晶格结构中的波传播,这些晶格结构是由在两个或三个方向上无限排列的三维(3D)单元胞组成的,缺陷沿着排列方向周期性地存在。单元格由三维梁组成,结合Timoshenko-Ehrenfest、Rayleigh-Love和扭转理论,建立了三维梁的动刚度公式。基于动态刚度矩阵,利用Wittrick-Williams算法可以准确有效地计算出缺陷晶格结构的任意数量或阶数的固有频率。将该方法与布洛赫定理相结合,可用于计算具有周期性缺陷的晶格结构的色散曲线。通过数值算例验证了该方法的准确性和有效性。此外,还分析了晶格结构中周期性缺陷对带隙的影响。Journal of the Mechanics and Physics of SolidsStrain localization in rate sensitive porous ductile materialsAlok Tripathy, Shyam M. Keralavarmadoi:10.1016/j.jmps.2024.105957速率敏感多孔延性材料的应变局部化Ductile failure by the onset of strain localization in rate sensitive porous materials is investigated using a linear perturbation stability analysis. A micromechanics-based constitutive model accounting for inhomogeneous yielding at the micro-scale, due to plastic strain concentration in the inter-void ligaments, is used. Strain and strain rate hardening of the material is accounted for using a phenomenological viscoplastic extension of the model. Unlike in earlier studies employing a rate-dependent model, an analytical closed form expression for the critical value of the hardening modulus at the onset of localization is derived. The predicted shape of the failure locus under proportional loading is shown to be consistent with known results in the literature for the loading path dependence of ductile failure. The model predicted failure loci are validated by comparison with mesoscopic unit cell model simulations of void growth in a viscoplastic power law hardening material. It is shown that the failure strains predicted by the model as a function of the hardening parameters are in good agreement with the strains to the onset of elastic unloading in the cell model simulations, signifying the onset of void coalescence at the micro-scale.采用线性摄动稳定性分析研究了速率敏感多孔材料中应变局部化的延性破坏。采用了基于微力学的本构模型,考虑了由于空隙间韧带的塑性应变集中而导致的微尺度非均匀屈服。材料的应变和应变率硬化是用模型的现象学粘塑性扩展来解释的。与早期采用速率相关模型的研究不同,本文导出了局部化开始时硬化模量临界值的解析封闭形式表达式。在比例加载下,预测的破坏轨迹形状与文献中已知的延性破坏的加载路径依赖结果一致。通过与粘塑性幂律硬化材料中孔洞生长的介观单胞模型模拟对比,验证了该模型预测的失效位点。结果表明,模型预测的失效应变随硬化参数的变化与胞体模型模拟中弹性卸载开始时的应变吻合较好,表明孔隙聚并在微观尺度上开始发生。Implicit implementation of a coupled transformation – plasticity crystal mechanics model for shape memory alloys that includes transformation rotationsRupesh K. Mahendran, Surya R. Kalidindi, Aaron P. Stebnerdoi:10.1016/j.jmps.2024.105964包含变形旋转的形状记忆合金相变-塑性耦合晶体力学模型的隐式实现A rate-dependent crystal-plasticity (CP) framework that captures the coupled phase transformation - plastic deformation behavior of shape memory alloys (SMAs) is presented. Here, different from previous models, the flow rule for martensitic phase transformation incorporates the entire deformation gradient for transformation, including the rotation. Predictions of transformation strain and variant selection of Nickel-Titanium (NiTi) using this model are directly compared with previous formulations that did not include the rotation. The results show that the rotation is essential to accurately calculate the single crystal and polycrystal micromechanics of variant selection and transformation strains of SMAs. The constitutive law formulation also includes current formulations for both slip and deformation twinning plasticity mechanisms, and the differences in transformation mechanisms are further shown to impact plasticity calculations through transformation-plasticity interactions. In addition to the advancement of the constitutive law, a computationally efficient implicit time integration scheme is given for numerical implementation and demonstrated using a user material subroutine (UMAT) in the commercial finite element code ABAQUS Standard. The proposed framework and the associated numerical protocols achieve stable solutions using strain increments on the order of 0.05 mm/mm in simulating inelastic deformations and strain increments 0.01 mm/mm in the elastic-inelastic transitions. Furthermore, the use of an analytic Jacobian results in stable convergence in fewer than 10 global Newton iterations while calculating solutions for elastic-inelastic transitions, making the computational benefits evident.提出了一种考虑形状记忆合金(SMA)相变-塑性变形耦合行为的率相关晶体塑性(CP)框架。与以往模型不同,该模型将马氏体相变的流动规则扩展到整个变形梯度,包括旋转。使用该模型对镍钛(NiTi)合金的相变应变和变体选择的预测直接与未考虑旋转的先前公式进行了比较。结果表明,旋转对于准确计算SMA的单晶和多晶微观力学的变体选择和相变应变至关重要。本构方程还包括目前用于描述滑移和塑性孪生机制的现有公式,并进一步显示了变形机制的差异如何通过相变-塑性相互作用影响塑性计算。除了材料本构方程的改进外,还给出了一个高效的隐式时间积分方案用于数值实现,并用商业有限元代码ABAQUS Standard中的用户材料子程序(UMAT)进行了演示。该框架及其相关数值协议在模拟塑性变形时使用0.05 mm/mm的应变增量,在模拟弹塑性过渡时使用0.01 mm/mm的应变增量,实现了稳定的解。此外,使用解析雅可比矩阵在计算弹塑性过渡的解时实现了在不到10次全局牛顿迭代中实现稳定的收敛,使计算优势显而易见。Mechanics of MaterialsBuckling instability of graphyne nanosheets under local indentationJiazhen Zhang, Peijian Chen, Juan Peng, Hao Liu, Guangjian Peng, Yingying Zhangdoi:10.1016/j.mechmat.2024.105206石墨烯纳米片在局部压痕下的屈曲不稳定性As a novel two-dimensional material, a well understanding of mechanical properties of graphyne under various loading conditions is essential for its blooming applications. However, the buckling mechanism of graphyne under local loads is still unclear, which hinders the development of its related nanodevices. In this work, the buckling behavior of graphyne under local indentation is studied by molecular dynamics simulation and theoretical analysis. It is found that the theoretical prediction of the critical indentation depth for buckling of graphyne agrees well with that from molecular dynamics simulation. The buckling morphology lies in the intermediate region between the contact region and the outer boundary. The critical indentation depth and the buckling morphology can be tuned by adopting various geometric and material parameters. The results should be helpful for not only guiding various applications of graphyne, but also improving the development of nanomechanics.石墨炔作为一种新型的二维材料,深入了解其在各种载荷条件下的力学性能对其广泛应用至关重要。然而,石墨烯在局部载荷作用下的屈曲机理尚不清楚,这阻碍了其相关纳米器件的开发。本文采用分子动力学模拟和理论分析相结合的方法研究了石墨烯在局部压痕作用下的屈曲行为。结果表明,石墨烯屈曲临界压痕深度的理论预测与分子动力学模拟结果吻合较好。屈曲形态位于接触区与外边界之间的中间区域。采用不同的几何参数和材料参数可以调整临界压痕深度和屈曲形态。研究结果不仅有助于指导石墨炔的各种应用,而且有助于促进纳米力学的发展。Thin-Walled StructuresFree Vibration and Stability Analyses of Functionally Graded Plates Resting on Elastic Foundations Based on 2D and Quasi-3D Shear Deformation Theories Using the Finite Strip MethodMohammad Foroughi, Mojtaba Azhari, Saeid Sarrami, Hamid Foroughidoi:10.1016/j.tws.2024.112715 基于二维和准三维剪切变形理论的弹性基础上功能梯度板自由振动与稳定性分析This paper explores the elastic buckling and free vibration behavior of thick functionally graded material (FGM) plates placed on elastic foundations, using two-dimensional (2D) and quasi-three-dimensional (quasi-3D) shear deformation theories. The material properties of the FGM plates are assumed to vary continuously through the thickness based on a power-law distribution. By minimizing the total potential energy and solving the associated eigenvalue problem, the classical finite strip method is applied to determine the critical buckling loads and natural frequencies of the FGM plates. A key novelty of this work lies in the development of a quasi-3D shear deformation theory, which incorporates thickness stretching effects, providing a more accurate distribution of transverse shear strains across the plate thickness. Additionally, the FSM is utilized to efficiently discretize the in-plane geometry, offering a computationally cost-effective solution for analyzing free vibration and mechanical buckling characteristics. The elastic foundation is modeled using Winkler and two-parameter Pasternak models. The complexity of the governing equations is reduced by decomposing the transverse displacement into bending, shear, and thickness stretching components. Numerical results for FGM plates with various boundary conditions are validated by comparing them with analytical solutions from existing literature. Additionally, the effects of parameters such as plate thickness-to-length ratio, length-to-width ratio, boundary conditions, and the power-law index are analyzed and discussed.本文利用二维(2D)和准三维(准3d)剪切变形理论,研究了弹性基础上的功能梯度材料厚板的弹性屈曲和自由振动行为。假设FGM板的材料性能随厚度呈幂律分布而连续变化。通过最小化总势能和求解相关的特征值问题,应用经典有限条法确定了FGM板的临界屈曲载荷和固有频率。这项工作的一个关键新颖之处在于准三维剪切变形理论的发展,该理论结合了厚度拉伸效应,提供了更准确的横向剪切应变在板厚上的分布。此外,利用FSM有效地离散平面内几何结构,为分析自由振动和机械屈曲特性提供了一种计算成本低廉的解决方案。采用温克勒模型和双参数帕斯捷尔纳克模型对弹性地基进行建模。通过将横向位移分解为弯曲、剪切和厚度拉伸分量,降低了控制方程的复杂性。通过与已有文献的解析解的比较,验证了不同边界条件下FGM板的数值结果。此外,还分析和讨论了板的厚长比、长宽比、边界条件和幂律指数等参数的影响。Vibration behavior of sandwich circular cylindrical shells with auxetic lattice core and CNT-reinforced facesheetsAmit Yadavdoi:10.1016/j.tws.2024.112716碳纳米管增强面板夹层圆柱壳的振动特性In this paper, free and forced vibration analyses of sandwich circular cylindrical shells with auxetic lattice core and carnanotubes (CNTs) reinforced facesheets are carried out. Simply supported boundary conditions are considered, and harmonic radial point loading is applied at the mid-length of the cylindrical shell. The equivalent mechanical properties of the proposed core and facesheets are obtained using modified Gibson's formula and rule-of-mixture, respectively. The mathematical model is formulated using the first-order shear deformation theory, incorporating von Kármán-type geometric non-linearity. A set of partial governing differential equations (PDEs) is derived using Hamilton's principle. Further, Galerkin's method is used to convert the PDEs into a set of ordinary differential equations. In order to obtain the frequency-amplitude response of the shells, an incremental harmonic balance method along with the arc length method is adopted. A comprehensive numerical investigation is carried out to examine the influence of geometrical parameters of the auxetic lattice, the volume fraction of CNTs, and the core-to-facesheet thickness ratio on the vibration behavior of sandwich cylindrical shells.本文对碳纳米管(cnt)增强表面板和带缺陷晶格芯的夹层圆柱壳进行了自由振动和强迫振动分析。考虑简支边界条件,在圆柱壳中长度处施加谐波径向点荷载。采用改进的Gibson公式和混合规则分别获得了所提出的岩心和面板的等效力学性能。数学模型采用一阶剪切变形理论,考虑von Kármán-type几何非线性。利用哈密顿原理导出了一组偏控制微分方程。进一步,利用伽辽金方法将偏微分方程转化为一组常微分方程。为了得到壳的频幅响应,采用了增量谐波平衡法和弧长法。采用数值模拟方法研究了复合晶格几何参数、碳纳米管体积分数和芯面厚度比对夹层圆柱壳振动特性的影响。来源:复合材料力学仿真Composites FEM

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