今日更新：Composite Structures 1 篇，Composites Part A: Applied Science and Manufacturing 2 篇，Composites Science and Technology 4 篇Composite StructuresA progressive damage model associated with dynamic fracture toughness and IFF criterion with a fast search algorithm of fracture angleZhuo Zhang, Kai Zhang, Bailin Zhengdoi:10.1016/j.compstruct.2023.117802与动态断裂韧性和 IFF 准则相关的渐进损伤模型，以及断裂角快速搜索算法This paper presents a quick search algorithm of the fracture angle of inter-fiber fracture (IFF) criterion and a progressive damage model considering the dynamic fracture toughness effect. The fracture angle determination of the IFF criterion is necessary and time-consuming, which has limited its practicality. Therefore, to accurately calculate stress exposure factors under various combinations of stress states, a highly efficient algorithm is needed. In this paper, a novel algorithm using stress tractions on the fracture plane and the golden section search (GSS) is promoted. Through a series of simulation tests, this novel algorithm has been proven to be exact and efficient compared with other two common algorithms, which saves an average of 63.2% and 28.1% of the time in 1 million calculations and 2 h 2 min 4 sec and 39 min 2 sec in simulations. Additionally, fracture toughness, which controls material damage evolution process, also has strain-rate effect like elastic modulus and strength. Hence, a new progressive damage model considering the dynamic fracture toughness effect is proposed. The results of dynamic compression and ballistic impact tests and simulations demonstrate the fidelity of the novel damage model.本文提出了一种纤维间断裂（IFF）准则断裂角的快速搜索算法和一种考虑到动态断裂韧性效应的渐进损伤模型。纤维间断裂（IFF）准则的断裂角测定既必要又耗时，这限制了其实用性。因此，要准确计算各种应力状态组合下的应力暴露因子，需要一种高效的算法。本文提出了一种利用断裂面上的应力牵引和黄金分割搜索（GSS）的新型算法。通过一系列模拟测试，证明这种新型算法与其他两种常用算法相比，精确高效，在 100 万次计算和 2 小时 2 分 4 秒和 39 分钟 2 秒的模拟中，平均分别节省了 63.2% 和 28.1% 的时间。此外，控制材料损伤演变过程的断裂韧性与弹性模量和强度一样，也具有应变速率效应。因此，提出了一种考虑动态断裂韧性效应的新的渐进损伤模型。动态压缩和弹道冲击试验及模拟结果表明了新型损伤模型的真实性。Composites Part A: Applied Science and ManufacturingOn the understanding of bubble dynamics through a calibrated textile-like porous medium using a machine learning based algorithmJoão Machado, Masoud Bodaghi, Mostafa Nikzad, Pedro P. Camanho, Suresh Advani, Nuno Correiadoi:10.1016/j.compositesa.2023.107955利用基于机器学习的算法了解气泡在经过校准的类纺织多孔介质中的动力学特性In this work, we present a proof of concept for both 3D-printed media and a machine learning analysis methodology to investigate void formation and transport during liquid filling. Through a series of experiments, we characterized void formation and transport at constant flow rates using two calibrated fabric-like porous geometries created by Stereolithography and Multi Jet Fusion 3D printing techniques. Our findings highlight the significance of porous medium geometry and void size, in addition to the capillary number, in characterizing void formation and mobility during resin flow into a mold containing a fibrous preform. Notably, the paper's strength lies in the presentation of advanced bubble analysis methods, including frame-by-frame high-resolution video analysis, enabling the identification of individual bubbles and the extraction of their statistics, such as count, size, and velocity throughout the experiment. These insights contribute to the design of more efficient processes, resulting in composite parts with reduced void content.在这项工作中，我们提出了一种三维打印介质的概念验证和机器学习分析方法，用于研究液体填充过程中的空隙形成和传输。通过一系列实验，我们利用立体光刻和多喷射融合三维打印技术创建的两种校准织物状多孔几何形状，对恒定流速下的空隙形成和传输进行了表征。我们的研究结果凸显了多孔介质几何形状和空隙大小以及毛细管数量在表征树脂流入含有纤维预型件的模具过程中空隙形成和流动性方面的重要性。值得注意的是，论文的优势在于介绍了先进的气泡分析方法，包括逐帧高分辨率视频分析，从而能够识别单个气泡并提取其统计数据，如整个实验过程中的数量、大小和速度。这些见解有助于设计更高效的工艺，从而减少复合材料部件的空隙含量。Ultrastretchable and adhesive MXene-based hydrogel for high-performance strain sensing and self-powered applicationWei Zhang, Pei-Lin Wang, Xing-Xiang Ji, Ling-Zhi Huang, Da-Qi Cao, Junfeng Li, Ming-Guo Madoi:10.1016/j.compositesa.2023.107957 用于高性能应变传感和自供电应用的超拉伸和粘性 MXene 基水凝胶Conductive hydrogels have been extensively explored for human movement and health monitoring. However, the poor adhesion of hydrogels to the skin hinders their performance in real-time monitoring with minimal loss of signal transmission. In this work, hydrogels composed of acrylic acid (AA), acrylic acid–N-hydrosuccinimide ester (AA–NHS), sulfobetaine methacrylate (SBMA), and cellulose nanofibers (CNFs) in the presence of initiators were rapidly gelated (within a few minutes) after adding Ti3C2TX MXene as a versatile crosslinking agent. AA and SBMA copolymerized to form the main network structure of the hydrogel and the introduced CNF improved the tensile strain of the hydrogels from 1737% to 2240%. By virtue of the combined zwitterionic-adhesion mechanism and NHS-activated ester bonds, the hydrogels conformally adhered to porcine skin with an adhesive strength of 11.6 kPa. When assembled as strain sensors, the hydrogel sensors exhibited high sensitivity (gauge factor = 4.98) and a fast response (95 ms). Next, the hydrogel was assembled as the electrode in a triboelectric nanogenerator (TENG) for mechanical-energy harvesting and self-powered sensing. The TENG exhibited good electrical output properties and could charge commercial capacitors with the mechanical energy harvested from walking. This work promises the design of wearable hydrogel devices with mechanical extensibility and self-adhesive properties.导电水凝胶已被广泛用于人体运动和健康监测。然而，水凝胶与皮肤的粘附性较差，这阻碍了其在实时监测中实现最小信号传输损失的性能。在这项研究中，由丙烯酸（AA）、丙烯酸-N-氢琥珀酰亚胺酯（AA-NHS）、甲基丙烯酸磺基甜菜碱（SBMA）和纤维素纳米纤维（CNFs）组成的水凝胶在加入作为多功能交联剂的 Ti3C2TX MXene 后，在引发剂的存在下（几分钟内）迅速凝胶化。AA 和 SBMA 共聚形成了水凝胶的主要网络结构，引入的 CNF 将水凝胶的拉伸应变从 1737% 提高到 2240%。凭借齐聚物粘附机制和 NHS 激活的酯键，水凝胶与猪皮肤贴合粘附，粘附强度达到 11.6 千帕。当组装成应变传感器时，水凝胶传感器表现出高灵敏度（测量系数 = 4.98）和快速响应（95 毫秒）。接着，水凝胶被组装成三电纳米发电机（TENG）的电极，用于机械能收集和自供电传感。该 TENG 具有良好的电输出特性，并能利用从行走中收集的机械能为商用电容器充电。这项研究有望设计出具有机械延伸性和自粘性的可穿戴水凝胶设备。Composites Science and TechnologyMode I fracture toughness with fiber bridging of unidirectional composite laminates under cryogenic temperatureJinxin Meng, Hongshuai Lei, Yuanchen Li, Yunlong Ma, Heng Yang, Panding Wang, Daining Fangdoi:10.1016/j.compscitech.2023.110386 低温条件下单向复合材料层压板纤维架桥的 I 型断裂韧性Carbon fiber reinforced polymer (CFRP) composites have widely been used in the aerospace field owing to their excellent mechanical properties. However, composite structures often fail under complex space environmental conditions. In particular, the fiber bridging and cryogenic temperature may greatly change the fracture toughness of CFRP composites. Herein, the effects of cryogenic temperature and fiber bridging on the fracture toughness of unidirectional composite laminates were experimentally examined by double cantilever beam (DCB) testing at different temperatures (room temperature, −50 °C, −70 °C, −100 °C, −150 °C, and −180 °C). Different calculation methods of fracture toughness were used and the results were compared. A method without measuring the delamination length at low temperatures was used and the results were consistent with other methods. The average difference in fracture toughness values was less than 5 %. The fiber-bridging microstructures of composites under cryogenic temperatures were examined by confocal microscopy along with the geometric morphology and parameters of surface roughness. The results suggested changes in the matrix failure mechanism at −50 °C, resulting in maximum fracture toughness, which is 26.45 % higher than that at room temperature. A semi-analytic approach was then proposed to express the bridge stress, and a bilinear cohesive zone model was established to simulate the delamination of composite laminates at low temperatures. Overall, the numerical data agreed well with the experimental results (peak force maximum error of 17 %), suggesting the usefulness of the proposed method for the prediction of interlamination properties and structural damage design of composite structures at cryogenic temperature.碳纤维增强聚合物（CFRP）复合材料因其优异的机械性能而被广泛应用于航空航天领域。然而，复合材料结构经常会在复杂的太空环境条件下失效。其中，纤维架桥和低温会极大地改变 CFRP 复合材料的断裂韧性。本文通过不同温度（室温、-50 °C、-70 °C、-100 °C、-150 °C和-180 °C）下的双悬臂梁（DCB）测试，实验研究了低温和纤维架桥对单向复合材料层压板断裂韧性的影响。采用了不同的断裂韧性计算方法，并对结果进行了比较。使用了一种在低温下不测量分层长度的方法，结果与其他方法一致。断裂韧性值的平均差异小于 5%。共聚焦显微镜检查了低温条件下复合材料的纤维桥接微结构以及几何形态和表面粗糙度参数。结果表明，在-50 °C时基体破坏机制发生了变化，导致断裂韧性达到最大值，比室温下的断裂韧性高出26.45%。随后提出了一种半解析方法来表达桥应力，并建立了双线性内聚区模型来模拟复合材料层压板在低温下的分层。总体而言，数值数据与实验结果吻合良好（峰值力最大误差为 17%），表明所提出的方法可用于预测低温下复合材料结构的层间特性和结构损伤设计。Experimental and simulation analysis of the effect of GNPs on the mechanical and interfacial properties of CF/PEEK-Ti fiber metal laminatesMeng Cao, Shuo Wang, Jian Zang, Mingyu Liu, Changjiang Qian, Yewei Zhang, Di Nadoi:10.1016/j.compscitech.2023.110387 GNPs 对 CF/PEEK-Ti 纤维金属层压板机械性能和界面性能影响的实验和模拟分析In this study, graphene nanoplatelets (GNPs) were used to improve the interfacial and mechanical properties of carbon fibre-reinforced polyetheretherketone-based titanium alloy laminates (CF/PEEK-Ti) and molecular dynamics (MD) simulations were used to investigate the mechanism by which GNPs improve CF/PEEK-Ti, collectively known as fibre reinforced metal laminates (FMLs). In addition, surface anodising of titanium (Ti) sheets was used further to enhance the interfacial bonding properties of the FMLs. The experimental results showed that the flexural and shear strengths of the anodised FMLs were increased by 77.7% and 29.5%, respectively, compared with those of the Ti plates without surface anodisation. Based on this, different levels (0–1.5 wt%) of GNPs were added to the FMLs matrix, and test results showed that FMLs containing 0.5 wt% GNPs had the best flexural and shear strengths, 108.9% and 130.8% higher than untreated FMLs without GNPs. In addition, an in-depth microscopic analysis was carried out to understand the enhancement mechanism of GNPs on FMLs. Finally, MD simulations were used to analyze the role and mechanism of GNPs in this system. The results show that the addition of GNPs can increase the interfacial energy of FMLs. In other words, the interfacial mechanical properties of FMLs are improved. The effect of the dispersion of GNPs on the interfacial properties of FMLs was also investigated. The polyetheretherketone (PEEK) matrix could be significantly improved by well-dispersed GNPs. These findings provide insight into designing high-performing composites for various engineering applications.本研究利用石墨烯纳米片（GNPs）改善了碳纤维增强聚醚醚酮基钛合金层压板（CF/PEEK-Ti）的界面和机械性能，并利用分子动力学（MD）模拟研究了 GNPs 改善 CF/PEEK-Ti （统称为纤维增强金属层压板（FMLs））的机理。此外，还对钛（Ti）片进行了表面阳极氧化处理，以进一步提高 FML 的界面结合性能。实验结果表明，与未进行表面阳极氧化处理的钛板相比，经过阳极氧化处理的 FML 的抗弯强度和抗剪强度分别提高了 77.7% 和 29.5%。在此基础上，在 FMLs 基体中添加了不同含量（0-1.5 wt%）的 GNPs，测试结果表明，含有 0.5 wt% GNPs 的 FMLs 的抗弯强度和抗剪强度最好，分别比未添加 GNPs 的 FMLs 高出 108.9% 和 130.8%。此外，还进行了深入的显微分析，以了解 GNPs 对 FML 的增强机制。最后，利用 MD 模拟分析了 GNPs 在该体系中的作用和机制。结果表明，GNPs 的加入可以增加 FMLs 的界面能。换言之，FML 的界面力学性能得到了改善。此外，还研究了 GNPs 的分散对 FMLs 的界面性能的影响。分散良好的 GNPs 能显著改善聚醚醚酮（PEEK）基体的性能。这些发现为设计各种工程应用的高性能复合材料提供了启示。An embedded digital element model to simulate the wrinkle defects driven by the consolidation of compositesYongshan Li, Kai Liu, Guangchang Chen, Ge Jingran, Jing Yang, Xuefeng Li, Shuo Liu, Jun Liangdoi:10.1016/j.compscitech.2023.110389 模拟复合材料固结产生的皱纹缺陷的嵌入式数字元素模型Understanding the mechanisms of fiber wrinkling during the compaction process is of paramount importance as fiber wrinkling significantly affects the mechanical properties of composite materials. This study introduces an embedded digital element model for simulating the consolidation process of prepreg. Flexible digital element chains are employed to simulate the reinforcing effect of fibers on resin, accounting for the viscoelastic constitutive behavior of uncured resin. The simulation captures intra-layer wrinkles and in-plane waviness defects in the consolidated prepreg, thereby uncovering the mechanism behind fiber wrinkle formation during composite material prepreg consolidation. The accuracy of the model is validated through compression experiments on flat plates and L-shaped structures. The results demonstrate that the proposed embedded digital element model accurately predicts wrinkle defects. Factors such as interlayer friction of the prepreg, consolidation temperature, and mold curvature radius significantly influence the shape and size of wrinkles.由于纤维起皱会严重影响复合材料的机械性能，因此了解压实过程中纤维起皱的机理至关重要。本研究介绍了一种用于模拟预浸料固结过程的嵌入式数字元素模型。采用柔性数字元素链模拟纤维对树脂的增强作用，并考虑未固化树脂的粘弹性构成行为。模拟捕捉了固化预浸料中的层内皱纹和平面波状缺陷，从而揭示了复合材料预浸料固化过程中纤维皱纹形成的机理。通过对平板和 L 型结构进行压缩实验，验证了模型的准确性。结果表明，所提出的嵌入式数字元素模型能准确预测皱纹缺陷。预浸料的层间摩擦力、固结温度和模具曲率半径等因素对皱纹的形状和大小有显著影响。Micromechanical characterization of Carbon/PEEK thermoplastic composite material in-situ consolidated by automated fiber placement: Stiffness predictionEmad Pourahmadi, Rajamohan Ganesan, Farjad Shadmehridoi:10.1016/j.compscitech.2023.110390 通过自动放置纤维对原位加固的碳/PEEK 热塑性复合材料进行微观力学表征：刚度预测Despite manufacturing challenges, Automated Fiber Placement (AFP) offers a viable alternative to conventional manufacturing methods, allowing for time and cost savings. Creating a Representative Volume Element (RVE) that realistically represents long-fiber-reinforced composites with high fiber volume fraction is a challenging task in modeling their response. The present research aims to predict effective stiffness properties of in-situ-consolidated Carbon/PEEK thermoplastic composite material by considering the effect of fiber volume fraction, void content, degree of crystallinity, and interlaminar resin pocket resulting from AFP in-situ consolidation manufacturing process. In this regard, two sets of samples were manufactured by AFP in-situ consolidation and autoclave re-consolidation methods. Both of them were evaluated by micrographic study and thermoanalytical Differential Scanning Calorimetry (DSC) technique to obtain inputs required for micromechanical analysis. The 2D RVEs on a micro-scale are developed to predict the transverse elastic modulus, out-of-plane Poisson's ratio and out-of-plane shear modulus of the composite material by applying Periodic Boundary Conditions (PBCs) and using Asymptotic Homogenization Theory (AHT). Results show that AFP in-situ consolidation may lead the transverse elastic and out-of-plane shear moduli of Carbon/PEEK thermoplastic composite material to be reduced by about 10 % and 20 %, respectively, compared to autoclave re-consolidation whereas the out-of-plane Poisson's ratio remains unchanged. The findings of the present work confirm that the mechanical performance of Carbon/PEEK thermoplastic composite material could be remarkably influenced by AFP in-situ consolidation manufacturing process, particularly in the transverse direction, which must be taken into account in finite element modeling, analyses, and design of AFP-manufactured composite laminates and structures.尽管在制造方面存在挑战，但自动纤维铺放技术（AFP）为传统制造方法提供了一种可行的替代方法，可以节省时间和成本。创建一个能真实再现高纤维体积分数的长纤维增强复合材料的代表体积元素（RVE）是对其响应建模的一项具有挑战性的任务。本研究旨在通过考虑纤维体积分数、空隙含量、结晶度和 AFP 原位固结制造过程中产生的层间树脂袋的影响，预测原位固结碳/PEEK 热塑性复合材料的有效刚度特性。为此，采用 AFP 原位固结法和高压釜再固结法制造了两组样品。通过显微照片研究和热分析差示扫描量热仪（DSC）技术对这两种方法进行了评估，以获得微观机械分析所需的输入数据。通过应用周期边界条件（PBC）和渐近均质化理论（AHT），开发了微尺度上的二维 RVE，以预测复合材料的横向弹性模量、面外泊松比和面外剪切模量。结果表明，与高压釜再固结相比，AFP 原位固结可使碳/PEEK 热塑性复合材料的横向弹性模量和平面外剪切模量分别降低约 10% 和 20%，而平面外泊松比保持不变。本研究结果证实，碳/PEEK 热塑性复合材料的机械性能会受到 AFP 原位固结制造工艺的显著影响，尤其是在横向方向上，这一点必须在 AFP 制造的复合材料层压板和结构的有限元建模、分析和设计中加以考虑。来源：复合材料力学仿真Composites FEM
