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【新文速递】2023年10月22日复合材料SCI期刊最新文章

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今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 2 篇,Composites Science and Technology 3 篇

Composite Structures

A topology optimization framework for 3D Phononic Crystals via the method of successive iteration of analysis and design

Zhu Yixiao, Kang Zhan

doi:10.1016/j.compstruct.2023.117641

通过分析和设计的连续迭代法实现三维声晶的拓扑优化框架

Topology optimization has become a useful tool for designing Phononic Crystals (PnCs) to achieve desired elastic wave propagation properties. However, topological design of three-dimensional (3D) PnCs remains a significant challenge due to extremely high computational cost required for the repeated solution of the nested double-loop problem of design optimization and eigenvalue analysis to determine the band structure during the optimization iteration process. This paper presents a more efficient topology optimization method based on the concept of successive iteration of analysis and design. The method employs a sequential approximation of the eigenpairs through an inverse iteration-like procedure to avoid solving the expensive eigenvalue problems in each design iteration. To further improve the efficiency of the design iteration, the eigenmodes of the intermediate PnCs designs are first computed on a relatively coarse finite element mesh. Then they are mapped onto the fine mesh and used as the initial trial eigenmodes in the eigenpair analysis and design sensitivity analysis. The high efficiency of the proposed method, as compared with conventional nested double-loop optimization approaches, is demonstrated by 3D numerical examples with over one million degrees of freedom. It is shown that this approach can achieve simultaneous convergence of the eigenvectors along with the design evolution of the unit cell, therefore substantially reduces the computational burden for high-resolution topological design of 3D PnCs.

拓扑优化已成为设计声波晶体(PnCs)以实现理想弹性波传播特性的有用工具。然而,由于在优化迭代过程中需要重复解决设计优化和特征值分析的嵌套双环问题以确定带状结构,计算成本极高,因此三维(3D)PnC 的拓扑设计仍然是一项重大挑战。本文提出了一种基于分析和设计连续迭代概念的更高效拓扑优化方法。该方法通过类似反迭代的程序对特征对进行顺序逼近,以避免在每次设计迭代中求解昂贵的特征值问题。为进一步提高设计迭代的效率,首先在相对较粗的有限元网格上计算中间 PnCs 设计的特征模。然后将它们映射到精细网格上,并在特征对分析和设计敏感性分析中用作初始试验特征模型。与传统的嵌套双环优化方法相比,所提出的方法具有很高的效率,超过一百万自由度的三维数值实例证明了这一点。结果表明,这种方法可以实现特征向量与单元设计演化的同步收敛,因此大大减轻了三维 PnC 高分辨率拓扑设计的计算负担。


Composites Part A: Applied Science and Manufacturing

Construction of alternating multilayer films with stable absorption-dominated electromagnetic shielding performance and reinforced mechanical properties via interface engineering

Wang Lingling, Wei Renbo, luo Yu, Liu Chenchen, Liu Xiaobo, Li Dong

doi:10.1016/j.compositesa.2023.107862

 

通过界面工程构建具有稳定吸收为主的电磁屏蔽性能和强化机械性能的交替多层膜

As an ideal material to lessen electromagnetic pollution, absorption-dominated electromagnetic interference (EMI) shielding composites still face the problems of complicated structure design and insufficient performance stability. Herein, an alternating multilayer film with stable absorption-dominated EMI shielding effectiveness (SE) and reinforced mechanical properties is fabricated by constructing hydrogen bonding between multilayers interface. When the layers increase to 4, benefiting from the construction of multilayer structure and the stronger interaction, the reflective shielding effectiveness decrease to 2.9 dB, the absorption coefficient of multilayer film increases from 0.13 to 0.52, the retention rate of EMI SE increases from 1.0 % to 97.6 % after bending 1000 cycles, and the tensile strength is enhanced from 5.7 MPa to 27.3 MPa. The calculated binding energies and the experimental results show that the interaction between Pluronic F127 anchored on the porous film and cellulose nanofibers entangled on the carbon nanotubes layer increases the interlayer interaction force and durability of EMI SE.

作为减少电磁污染的理想材料,以吸收为主的电磁干扰(EMI)屏蔽复合材料仍然面临着结构设计复杂、性能不够稳定等问题。本文通过在多层膜界面之间构建氢键,制备了一种具有稳定的吸收主导型电磁干扰屏蔽效能(SE)和增强机械性能的交替多层膜。当层数增加到 4 层时,得益于多层结构的构建和更强的相互作用,反射屏蔽效果降低到 2.9 dB,多层薄膜的吸收系数从 0.13 增加到 0.52,弯曲 1000 次后 EMI SE 的保持率从 1.0 % 增加到 97.6 %,拉伸强度从 5.7 MPa 提高到 27.3 MPa。计算得出的结合能和实验结果表明,锚定在多孔薄膜上的 Pluronic F127 与缠结在碳纳米管层上的纤维素纳米纤维之间的相互作用增加了层间相互作用力,提高了 EMI SE 的耐久性。


An inverse method for curing process-induced eigenstrain reconstruction of laminated composites

Zhang Zaoxu, Zhao Xueying, Ji Qingxiang, Zhang Jiawei, Xu Fuquan, Wang Changguo

doi:10.1016/j.compositesa.2023.107863

 

层状复合材料固化过程诱导特征应变重建的反演方法

Accurate acquisition of the curing process-induced eigenstrain distribution is vital for predicting residual stress of laminated composites. In this work we develop a novel inverse method for full-field PIE reconstruction of laminated composites. We design standard laminates to obtain the PIE of unidirectional and woven lamina which are key ingredients of full-field PIE. Then an inverse model is established to accurately calculate lamina’s PIE from the measured residual middle-plane strain and curvature of standard laminates. Full-field PIE of validation laminates are then reconstructed by the obtained lamina’s PIE. Experimental results are in good agreement with the reconstructed results, verifying the accuracy and effectiveness of our proposed method. Finally, we implement the inverse method in accurately reconstructing full-field PIE of a hybrid laminated composite I-beam. We also observe that the PIE is process dependent, indicating that PIE can be used to evaluate the effect of curing process on residual stress.

准确获取固化过程引起的特征应变分布对于预测层状复合材料的残余应力至关重要。在这项工作中,我们开发了一种用于层状复合材料全场 PIE 重建的新型逆方法。我们设计了标准层压板,以获得单向层压板和编织层压板的 PIE,这是全场 PIE 的关键要素。然后建立一个逆模型,根据测量到的标准层压板残余中间平面应变和曲率精确计算层压板的 PIE。然后根据所获得的层压板 PIE 重建验证层压板的全场 PIE。实验结果与重建结果十分吻合,验证了我们提出的方法的准确性和有效性。最后,我们采用反演方法精确地重建了混合层压复合材料工字梁的全场 PIE。我们还观察到 PIE 与工艺相关,这表明 PIE 可用于评估固化工艺对残余应力的影响。


Composites Part B: Engineering

Significant improvement of the room and cryogenic mechanical properties of an AlN particle reinforced Al matrix composite by alloying element magnesium

Sun Xinda, Fan Yong, Nie Jinfeng, Chen Yuyao, Xie Kewei, Liu Sida, Zhao Yoghao, Liu Xiangfa

doi:10.1016/j.compositesb.2023.111056

通过添加镁合金元素显著改善氮化铝颗粒增强铝基复合材料的室温和低温力学性能

Nowadays, the mechanical properties of aluminum alloys have been studied extensively, but the study of aluminum matrix composites (AMCs) at extreme temperatures, particularly at cryogenic temperatures, is rare. In this work, an AlNp reinforced AMCs with excellent room and cryogenic temperature mechanical properties was manufactured by adding magnesium, and the corresponding microstructure evolution and strengthening mechanisms were systematically investigated. There are two kinds of particles in AlNp/Al, the small AlNp and the large AlB2p. With the Mg content increased, the AlNp became more dispersed and the AlB2p transformed into AlMgB4p. In addition, Mg atoms also dissolved in the matrix, which played a positive role in improving the mechanical properties. The ultimate tensile strength of the composites at RT was increased to 317 MPa, 419 MPa, and 485 MPa from 251 MPa after adding 1, 3, and 5 wt% Mg respectively. The cryogenic strength was further increased to 519 MPa, 592 MPa, and 611 MPa from 469 MPa, while keeping a decent ductility of about 5.6%, which was due to the more uniform microstructure avoiding crack generation.

目前,人们对铝合金的力学性能进行了广泛的研究,但对铝基复合材料(AMC)在极端温度,尤其是低温下的力学性能的研究却很少见。本研究通过添加镁制备了具有优异室温和低温力学性能的 AlNp 增强 AMC,并系统研究了其相应的微观结构演变和强化机理。AlNp/Al 中存在两种颗粒,即小颗粒 AlNp 和大颗粒 AlB2p。随着镁含量的增加,AlNp 变得更加分散,AlB2p 转变为 AlMgB4p。此外,镁原子也溶解在基体中,这对改善力学性能起到了积极作用。添加 1、3 和 5 wt% 的镁后,复合材料在 RT 时的极限拉伸强度分别从 251 MPa 提高到 317 MPa、419 MPa 和 485 MPa。低温强度从 469 兆帕进一步提高到 519 兆帕、592 兆帕和 611 兆帕,同时保持了约 5.6% 的良好延展性,这是由于微观结构更加均匀,避免了裂纹的产生。


Synergistically enhancing weavability and interface behavior by applying PDMS/MXene on carbon fiber surface through ultrasound assistance

Sun Zhaoling, Zheng Baoping, Chen Chaoyu, Dong Zhijia, Ma Pibo

doi:10.1016/j.compositesb.2023.111071

通过超声波辅助将 PDMS/MXene 应用于碳纤维表面,协同增强可织造性和界面行为

The poor interfacial properties and weavability of carbon fiber reinforced polymer (CFRP) composites stem from the surface chemical inertness and low wear resistance of carbon fiber (CF). Herein, we developed an effective approach to fabricate the CF@Polydimethylsiloxane/MXene (CF@PDMS/MXene) using ultrasound-assisted techniques, to improve both wear resistance and interfacial properties. The effectiveness of the modified treatment was assessed by Fourier transform infrared spectroscopy (FT-IR), microscopic confocal laser Raman spectrometer (Raman), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The success of the graft was evaluated using field emission scanning electron microscopes (FE-SEM) and energy dispersive spectrometry (EDS). The interfacial shear strength (IFSS) of the composite was evaluated through fiber pull-out experiments. Different weight ratios of MXene nanoparticles were employed during the grafting process to investigate their impact on surface morphology, wear resistance, and interfacial properties. The results demonstrated that CF@PDMS/MXene-1.5 wt% exhibited a residual fracture tensile strength 14.8 % higher than desized CF when the MXene concentration was increased to 1.5wt%. Additionally, the IFSS of CF@PDMS/MXene-1.5 wt% was observed to be 113 % greater than desized CF. Consequently, this novel modification strategy holds great promise for enhancing the mechanical performance of CFRP composites.

碳纤维增强聚合物(CFRP)复合材料的界面性能和可织造性差源于碳纤维(CF)的表面化学惰性和低耐磨性。在此,我们开发了一种利用超声辅助技术制造 CF@聚二甲基硅氧烷/MXene(CF@PDMS/MXene)的有效方法,以改善其耐磨性和界面性能。傅立叶变换红外光谱(FT-IR)、显微共焦激光拉曼光谱仪(Raman)、X 射线光电子能谱(XPS)和热重分析(TGA)对改性处理的效果进行了评估。使用场发射扫描电子显微镜(FE-SEM)和能量色散光谱仪(EDS)评估了接枝的成功率。通过纤维拉出实验评估了复合材料的界面剪切强度(IFSS)。在接枝过程中采用了不同重量比的 MXene 纳米粒子,以研究它们对表面形貌、耐磨性和界面性能的影响。结果表明,当 MXene 的浓度增加到 1.5wt% 时,CF@PDMS/MXene-1.5 wt% 的残余断裂拉伸强度比脱盐 CF 高 14.8%。此外,还观察到 CF@PDMS/MXene-1.5 wt% 的 IFSS 比去甲基化 CF 高 113%。因此,这种新型改性策略有望提高 CFRP 复合材料的机械性能。


Composites Science and Technology

Lightweight and recyclable hybrid multifunctional foam based cellulose fibers with excellent flame retardant, thermal, and acoustic insulation property

Liao Jianming, Hou Yansu, Li Jun, Zhang Min, Dong Yunyuan, Chen Xiaobin

doi:10.1016/j.compscitech.2023.110315

 

基于纤维素纤维的轻质可回收混合多功能泡沫,具有优异的阻燃、隔热和隔音性能

The development of eco-friendly and good-performance foam materials is essential for the environment and energy saving. Conventional inorganic and organic foams suffer from brittleness and contamination problems. Here, we report a facile and scalable hybrid strategy to prepare shape-stable cellulose-based multifunctional foam via physical cross-linking of PVA and stabilization of HGMs. The prepared foam exhibits ultra-low density (27.0 mg/cm3), enhanced flame-retardant performance (the PHRR decreased from 161.8 to 89.1 kW/m2, LOI value up to 26.2%), low thermal conductivity (48.2 mW/mK), good acoustic insulation property (NRC of 0.41), and good mechanical properties (with specific compressive modulus of 15.3 MPa cm3/g). Moreover, the foam can be recycled under simplified procedures. Our approach provides a novel alternative to the manufacture of low-cost, eco-friendly, and scalable foam materials. This multifunctional lightweight material is highly sought after for modern engineering construction applications.

为了保护环境和节约能源,开发环保型高性能泡沫材料至关重要。传统的无机和有机泡沫材料存在脆性和污染问题。在此,我们报告了一种通过物理交联 PVA 和稳定 HGMs 来制备形状稳定的纤维素基多功能泡沫的简便且可扩展的混合策略。制备的泡沫具有超低密度(27.0 mg/cm3)、更强的阻燃性能(PHRR 从 161.8 kW/m2 降至 89.1 kW/m2,LOI 值高达 26.2%)、低导热率(48.2 mW/mK)、良好的隔音性能(NRC 为 0.41)和良好的机械性能(比压缩模量为 15.3 MPa cm3/g)。此外,这种泡沫还可以通过简化程序进行回收。我们的方法为制造低成本、环保和可扩展的泡沫材料提供了一种新的选择。这种多功能轻质材料在现代工程建筑应用中备受青睐。


Synthesis of fractal crystallized organic microspheres together with constructing full covalent bonding at the interface to strengthen and toughen aramid fiber composites

Fan Chunlin, Lyu Junwei, Li Zheng, Luo Longbo, Liu Xiangyang

doi:10.1016/j.compscitech.2023.110313

 

合成分形结晶有机微球并在界面上构建全共价键以增强和韧化芳纶纤维复合材料

Regulating the interface to simultaneously enhance the strength and toughness of aramid fiber composites remains a great challenge. Herein, a resilient, full covalent interface was constructed by introducing fractal crystallized organic microspheres into the interface of aramid fiber composites using the twice fluorination approach. Firstly, the aromatic polyamide with ether bonds was synthesized, and the fractal crystallized microspheres with a porous surface containing amino groups were prepared by thermally induced solution self-assembly. Subsequently, the twice fluorination method introduces C–F bonds to the surfaces of both fibers and microspheres, respectively. Then, the covalent bonds among fibers, microsphere, and resin were formed by the derivative reaction of C–F bonds. This interface boosts the interlaminar shear strength (ILSS) of composites by 100.5% to 36.7 MPa and the unnotched impact toughness of composites by 13.5%–1363 kJ/m2. Comparative analyses reveal the full covalent interface and the fractal structure of microspheres contribute 47.8% and 52.2% to the ILSS enhancement, respectively. In addition, the fractal structure of microspheres is the only factor for increased toughness. Finite element analysis reveals that the fractal crystallized microspheres combined with full covalent interface facilitate elastic stress transfer within the composites to enhance the performance of composites.

调节界面以同时提高芳纶纤维复合材料的强度和韧性仍然是一项巨大的挑战。在此,我们采用两次氟化法,在芳纶纤维复合材料的界面中引入分形结晶有机微球,从而构建了一种具有弹性的全共价界面。首先合成具有醚键的芳香族聚酰胺,并通过热诱导溶液自组装制备出表面多孔且含有氨基的分形结晶微球。随后,通过两次氟化法分别在纤维和微球表面引入 C-F 键。然后,纤维、微球和树脂之间通过 C-F 键的衍生反应形成共价键。这种界面使复合材料的层间剪切强度(ILSS)提高了 100.5% 至 36.7 MPa,使复合材料的无缺口冲击韧性提高了 13.5% 至 1363 kJ/m2。对比分析表明,全共价界面和微球的分形结构对提高 ILSS 的贡献率分别为 47.8% 和 52.2%。此外,微球的分形结构是提高韧性的唯一因素。有限元分析表明,分形结晶微球与全共价界面相结合,促进了复合材料内部的弹性应力传递,从而提高了复合材料的性能。


Enhancing fracture toughness of polydimethylsiloxane with cyclosiloxane hybrid polymer microspheres

Tao Yuan, Mei Shuxing, Yi Haokun, Pan Xuansheng, Zhang Rong, Li Zhuo

doi:10.1016/j.compscitech.2023.110314

 

用环硅氧烷杂化聚合物微球增强聚二甲基硅氧烷的断裂韧性

Polydimethylsiloxane (PDMS) offers many unique advantages, but the poor fracture toughness (300–500 J/m2) limits its applications. Conventional methods of toughening PDMS through chain modification or inorganic fillers may negatively impact other properties, such as increase in hysteresis, stiffness, or viscosity. To address this problem, we introduce organic cyclosiloxane hybrid polymer (CHP) microspheres to toughen PDMS. These microspheres are synthesized by emulsion polymerization of two cyclosiloxane monomers and can be regarded as an extremely crosslinked PDMS. The interpenetration of polymer chains between CHP and matrix increases the interface adhesion to transfer the stress while the high modulus contrast can prevent the propagation of cracks, resulting in a high toughness without a sharp increase in stiffness. At the same time, the low friction between the filler and matrix reduces viscosity and hysteresis. Moreover, by incorporating magnetically responsive Fe3O4 nanoparticles, the CHP microspheres can be aligned. Aligned-CHP/PDMS composites exhibit a fracture toughness of 4223 J/m2, three times higher than SiO2 reinforced composites and nearly an order of magnitude higher than pure PDMS. These composites also have a lower modulus (3.3 MPa), lower hysteresis (0.167), and a viscosity two orders of magnitude lower compared to SiO2-filled counterparts. This method offers a new pathway for toughening siloxane elastomers without affecting other properties.

聚二甲基硅氧烷(PDMS)具有许多独特的优点,但其断裂韧性较差(300-500 J/m2),限制了其应用范围。通过链改性或无机填料增韧 PDMS 的传统方法可能会对其他性能产生负面影响,如增加滞后性、刚度或粘度。为了解决这个问题,我们引入了有机环硅氧烷杂化聚合物(CHP)微球来增韧 PDMS。这些微球是通过两种环硅氧烷单体的乳液聚合合成的,可视为一种极度交联的 PDMS。CHP 与基体之间聚合物链的相互渗透增加了界面粘附力,从而可以传递应力,而高模量对比可以防止裂纹扩展,从而在不急剧增加刚度的情况下获得高韧性。同时,填料与基体之间的低摩擦力可降低粘度和滞后性。此外,通过加入具有磁响应性的 Fe3O4 纳米粒子,CHP 微球还可以对齐。对齐的 CHP/PDMS 复合材料的断裂韧性高达 4223 J/m2,是二氧化硅增强复合材料的三倍,比纯 PDMS 高出近一个数量级。这些复合材料的模量(3.3 兆帕)、滞后(0.167)和粘度也比填充二氧化硅的同类产品低两个数量级。这种方法为增韧硅氧烷弹性体而不影响其他性能提供了一条新途径。


来源:复合材料力学仿真Composites FEM
ACTMechanicalSystemMAGNET断裂复合材料化学拓扑优化建筑电子CONVERGE裂纹化机材料试验
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首次发布时间:2024-11-03
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【新文速递】2023年10月13日固体力学SCI期刊最新文章

今日更新:International Journal of Solids and Structures 1 篇,Journal of the Mechanics and Physics of Solids 1 篇,Mechanics of Materials 1 篇,International Journal of Plasticity 1 篇,Thin-Walled Structures 1 篇International Journal of Solids and StructuresDeep homogenization networks for elastic heterogeneous materials with two- and three-dimensional periodicityWu Jiajun, Jiang Jindong, Chen Qiang, Chatzigeorgiou George, Meraghni Fodildoi:10.1016/j.ijsolstr.2023.112521二维和三维周期性弹性异质材料的深度均质网络We present a deep learning framework that leverages computational homogenization expertise to predict the local stress field and homogenized moduli of heterogeneous materials with two- and three-dimensional periodicity, which is named physics-informed Deep Homogenization Networks (DHN). To this end, the displacement field of a repeating unit cell is expressed as two-scale expansion in terms of averaging and fluctuating contributions dependent on the global and local coordinates, respectively, under arbitrary multi-axial loading conditions. The latter is regarded as a mesh-free periodic domain estimated using fully connected neural network layers by minimizing residuals of Navier's displacement equations of anisotropic microstructured materials for specified macroscopic strains with the help of automatic differentiation. Enabled by the novel use of a periodic layer, the boundary conditions are encoded directly in the DHN architecture which ensures exact satisfaction of the periodicity conditions of displacements and tractions without introducing additional penalty terms. To verify the proposed model, the local field variables and homogenized moduli were examined for various composites against the finite-element technique. We also demonstrate the feasibility of the proposed framework for simulating unit cells with locally irregular fibers via transfer learning and find a significant enhancement in the accuracy of stress field recovery during neural network retraining.我们提出了一种深度学习框架,利用计算均质化专业知识来预测具有二维和三维周期性的异质材料的局部应力场和均质化模量,并将其命名为物理信息深度均质网络(DHN)。为此,在任意多轴加载条件下,重复单元格的位移场被表示为双尺度扩展,即分别取决于全局坐标和局部坐标的平均贡献和波动贡献。在自动微分的帮助下,通过最小化各向异性微结构材料的纳维位移方程残差来估算指定的宏观应变,从而将后者视为使用全连接神经网络层估算的无网格周期域。通过新颖地使用周期层,边界条件被直接编码到 DHN 架构中,从而确保在不引入额外惩罚项的情况下准确满足位移和牵引的周期性条件。为了验证所提出的模型,我们使用有限元技术对各种复合材料的局部场变量和均质化模量进行了检验。我们还证明了通过迁移学习模拟具有局部不规则纤维的单元格的可行性,并发现在神经网络再训练过程中应力场恢复的准确性显著提高。Journal of the Mechanics and Physics of SolidsEffect of stacking sequence and interlayer toughening in +/−45 laminatesNguyen Minh Hoang, Waas Anthony M.doi:10.1016/j.jmps.2023.105458+/-45层压板中堆叠顺序和层间增韧的影响This paper investigates the combined effect of stacking sequence and interlayer toughening on the mechanical response and failure modes of ± 45 carbon fiber reinforced laminates, through experimental and numerical studies. Two material systems (T800H/3631, T800S/3900) and three stacking sequences (4 double plies, 4 plies, 8 plies) have been examined. Digital Image Correlation (DIC) and a high resolution edge camera were utilized to capture the intricate crack patterns in each ply. This paper also addresses the challenge of the nonlinear in-plane shear characterization of each lamina, and proposes an amendment to the existing ASTM standard to obtain the lamina shear strength and the in-situ non-linear response. The complex progression of micro-damage, matrix cracks and delamination as well as the final two-piece failure were captured by the enhanced semi-discrete damage modeling (eSD2M) framework. A parametric study was performed to reverse-engineer the most critical parameters such as interlayer strengths and toughnesses. The obtained values reflect the difference in the interlayer composition between the two material systems.本文研究了堆叠顺序和层间增韧对 ± 45 碳纤维增强层压板的力学响应和破坏模式的综合影响。研究了两种材料系统(T800H/3631、T800S/3900)和三种堆叠顺序(4 层、4 层、8 层)。利用数字图像相关性(DIC)和高分辨率边缘照相机捕捉每层中错综复杂的裂纹图案。本文还探讨了对每层板进行非线性面内剪切表征的难题,并提出了对现有 ASTM 标准的修改建议,以获得层板剪切强度和原位非线性响应。增强型半离散损伤建模(ESD2M)框架捕捉到了微损伤、基体裂纹和分层的复杂发展过程以及最终的两片破坏。通过参数研究反向设计了最关键的参数,如层间强度和韧性。所获得的数值反映了两种材料系统层间成分的差异。Mechanics of MaterialsCombined mean-field and full-field homogenization of porous elasto-plastic materials and composites under arbitrary stress triaxialitiesNaili Chiheb, Doghri Issamdoi:10.1016/j.mechmat.2023.104818任意三轴应力条件下多孔弹塑性材料和复合材料的均质化和全场均质联合研究A predictive micromechanical approach is proposed for porous materials where the unreinforced or reinforced matrix phase is elasto-plastic with hardening. The cavities can be spheres, long or short cylinders. The approach is based on an alternative microstructure made of elasto-plastic inhomogeneities embedded in a homogenized porous matrix phase, and the volume fractions are determined from a maximum packing argument. The effective properties of single hollow solids are computed with an energy-based approach coupled with full-field finite element (FE) analyses. Next, the alternative microstructures are homogenized with mean-field (MF) models. For reinforced porous materials, a two-level method is adopted, where the proposed approach is used at the lower level to obtain a fictitious homogenized matrix, in which reinforcements are embedded at the upper level. The present work is restricted to monotonic and proportional loadings and to the secant formulation of isotropic or transversely isotropic elasto-plasticity. However, no constitutive models are supposed or identified. The predictions were verified against reference full-field FE results on the actual microstructures in 3D and 2D plane strain or stress, for arbitrary stress triaxialities, and good agreement was found in all cases.针对多孔材料提出了一种预测性微机械方法,在这种材料中,非增强或增强基体相是具有硬化的弹性塑性相。空腔可以是球体、长圆柱体或短圆柱体。该方法基于由嵌入均质化多孔基质相中的弹塑性非均质物构成的替代微结构,并通过最大堆积论证确定体积分数。通过基于能量的方法和全场有限元(FE)分析,计算了单个空心固体的有效特性。然后,用均值场 (MF) 模型对替代微结构进行均匀化处理。对于增强多孔材料,采用了两级方法,即在下级使用所建议的方法来获得虚构的均质化基体,在上级嵌入增强材料。目前的研究仅限于单调荷载和比例荷载,以及各向同性或横向各向同性弹塑性的正割公式。但是,没有假定或确定构成模型。在任意应力三轴性条件下,预测结果与实际微结构在三维和二维平面应变或应力条件下的全场有限元分析参考结果进行了验证,结果发现在所有情况下都具有良好的一致性。International Journal of PlasticityA data-based derivation of the internal stress in the discrete-continuum transition regime of dislocation based plasticityLee Sing-Huei, Schulz Katrindoi:10.1016/j.ijplas.2023.103771基于数据的差排塑性离散-连续转变机制中的内应力推导Effectively homogenizing microstructure heterogeneity within the coarse-graining volume is a long-lasting challenge in crystal plasticity theories. In this paper, we propose a data-based homogenization method that utilizes discrete dislocation dynamic simulations to derive the nearfield correction stress (back stress) for continuum models. This stress accounts for the effective stress field induced by microstructure heterogeneity under the length scale of a coarse-graining volume, providing a physically based homogenization approach. To bridge the gap between discrete and continuous regimes, we introduce two versions of the nearfield correction stress, as well as a criterion based on microstructure and numerical parameters to determine the discrete and continuous transition. Moreover, by analyzing the mathematical connections with the work-conjugated gradient plasticity theory, we further provide a physical explanation for the observed material length scale in the thermodynamically consistent back stress term. This work presents a novel methodology for effectively addressing microstructure heterogeneity and advancing the understanding and modeling of material behavior bridging different length scales.有效地均化粗晶粒体积内的微观结构异质性是晶体塑性理论长期面临的挑战。在本文中,我们提出了一种基于数据的均质化方法,利用离散位错动态模拟来推导连续模型的近场校正应力(背应力)。该应力考虑了粗晶粒体积长度尺度下微结构异质性引起的有效应力场,提供了一种基于物理的均质化方法。为了弥合离散和连续状态之间的差距,我们引入了两个版本的近场修正应力,以及一个基于微观结构和数值参数的标准,以确定离散和连续的过渡。此外,通过分析与功-共轭梯度塑性理论的数学联系,我们进一步为热力学一致的背应力项中观察到的材料长度尺度提供了物理解释。这项研究提出了一种新颖的方法,可有效解决微结构异质性问题,并促进对弥合不同长度尺度的材料行为的理解和建模。Thin-Walled StructuresExperimental investigation on stiffened plates with non-continuous longitudinal stiffeners ending within the panelLukas Immo, Timmers Ralph, Ropele Melanie, Lang Robertdoi:10.1016/j.tws.2023.111260带有非连续纵向加强筋的加劲板的实验研究The present contribution investigates a construction method predominately applied in crane manufacturing known as non-continuous longitudinal stiffening. In this approach, the longitudinal stiffeners end within the panel, leaving a gap before reaching the transverse stiffener or the end of the girder. Current standardization is limited to conventional continuous stiffening. Therefore, the present study conducts an experimental test series of 50 close-to-reality scaled, non-continuously longitudinally stiffened plates subjected to uniform compression to characterize their structural behavior. The results are compared regarding different geometry parameters. One main conclusion is that the gap drastically governs the ultimate resistance, usually leading to a triangular-shaped buckling mode.本论文研究的是一种主要应用于起重机制造的施工方法,即非连续纵向加劲。在这种方法中,纵向加劲件在面板内结束,在到达横向加劲件或大梁端部之前留有间隙。目前的标准化仅限于传统的连续加劲。因此,本研究对 50 块接近真实比例的非连续纵向加劲板进行了一系列实验测试,对其进行均匀压缩,以确定其结构行为特征。实验结果针对不同的几何参数进行了比较。一个主要结论是,间隙极大地影响了极限阻力,通常会导致三角形屈曲模式。来源:复合材料力学仿真Composites FEM

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