【新文速递】2023年12月1日复合材料SCI期刊最新文章

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今日更新：Composite Structures 5 篇，Composites Part A: Applied Science and Manufacturing 1 篇，Composites Part B: Engineering 1 篇

Composite Structures

Agglomeration and interphase-influenced effective elastic properties of Metal/Graphene nanocomposites: A developed mean-field model

Mojtaba Mazaheri, Javad Payandehpeyman, Mahdi Hedayatian

doi:10.1016/j.compstruct.2023.117762

金属/石墨烯纳米复合材料的团聚和相间影响的有效弹性特性：开发的均场模型

The strength of metallic nanocomposites structures can be greatly improved by adding nanofillers to the matrix. However, there is a discrepancy between the conventional theories and the experimental evidence on the effect of nanofiller loading on the strength of the nanocomposite. The conventional theories predict that the strength increases with the nanofiller loading, but the experimental evidence shows that there is an optimal nanofiller loading beyond which the strength does not improve much. This discrepancy, especially at high filler loadings, is due to the neglect of the agglomeration and the interphase region formation in the composite structure modeling. In this paper, we propose a new micromechanical model based on mean-field theory to examine how the agglomeration and the interphase region influence the elastic modulus of metal/graphene nanocomposites (MGNs). We also explore how other factors, such as interphase region thickness and strength, graphene size, and metallic matrix elastic modulus, influence the elastic modulus of MGNs. We present a mathematical model that describes how the thickness and modulus of the interphase layer of graphene nanoplatelets change due to agglomeration. This model allows us to reproduce the parabolic behavior of the elastic modulus of the composite, which is consistent with the experimental results.

在基体中添加纳米填料可以大大提高金属纳米复合材料结构的强度。然而，在纳米填料的添加量对纳米复合材料强度的影响方面，传统理论与实验证据之间存在差异。传统理论预测强度会随着纳米填料含量的增加而增加，但实验证据表明，存在一个最佳的纳米填料含量，超过这个含量，强度不会有太大改善。这种差异，尤其是在高填充量时，是由于在复合材料结构建模中忽略了团聚和相间区域的形成。在本文中，我们提出了一种基于均场理论的新微机械模型，以研究团聚和相间区如何影响金属/石墨烯纳米复合材料（MGNs）的弹性模量。我们还探讨了相间区厚度和强度、石墨烯尺寸和金属基体弹性模量等其他因素如何影响 MGN 的弹性模量。我们提出了一个数学模型，用于描述石墨烯纳米片相间层的厚度和模量如何因团聚而发生变化。通过该模型，我们可以再现复合材料弹性模量的抛物线行为，这与实验结果是一致的。

Continuous fiber reinforced meta-composites with tailorable Poisson’s ratio and effective elastic modulus: Design and experiment

Guixing Li, Yuan Chen, Guangkai Wei

doi:10.1016/j.compstruct.2023.117768

具有可定制泊松比和有效弹性模量的连续纤维增强元复合材料：设计与实验

Auxetic metamaterials, i.e., with negative Poisson’s ratio are attracting increasing attention. This study develops a novel method to design and investigate continuous fiber-reinforced meta-composites with tailorable negative Poisson’s ratio and effective elastic modulus. First, the design scheme based on parametric level set method, is proposed by combining fast marching method, filtering technology and matrix rotation for attaining the two-dimensional isotropic composites. A novel objective function considering both negative Poisson’s ratio and effective elastic modulus is introduced and the result demonstrate that it is effective to not only accelerate the numerical convergence but also achieve a larger negative Poisson’s ratio when compared with that using the currently-used objective function. By tailoring a weight ratio for balancing the negative Poisson’s ratio and effective elastic modulus, a general contradictive trend was captured. Experimentally, the specimens are accordingly fabricated via 3D printing. Then, the axial compression tests are performed with the aid of digital image correlation technology to characterize the deformation behaviors and evaluate the mechanical properties of the designed meta-composites. Experimental results show that, as the weight ratio increases from 0.02 to 1.57, the effective elastic modulus increases from 180.5 MPa to 310.3 MPa (enhanced by 71.9%) while the negative Poisson’s ratio decreases from −0.41 to −0.036 (reduced by 91.4%), proving the effectiveness of the design method. The design methods and experimental results can provide effective approaches and important information for designing novel continuous fiber reinforced meta-composites with tailorable mechanical performance.

具有负泊松比的超材料正受到越来越多的关注。本研究开发了一种新方法，用于设计和研究具有可定制负泊松比和有效弹性模量的连续纤维增强超材料。首先，结合快速行进法、过滤技术和矩阵旋转，提出了基于参数水平集法的设计方案，以获得二维各向同性复合材料。引入了同时考虑负泊松比和有效弹性模量的新目标函数，结果表明，与目前使用的目标函数相比，它不仅能有效加快数值收敛速度，还能获得更大的负泊松比。通过调整权重比来平衡负泊松比和有效弹性模量，可以捕捉到一个普遍的矛盾趋势。实验中，试样是通过三维打印制作的。然后，借助数字图像相关技术进行轴向压缩试验，以表征变形行为并评估所设计元复合材料的力学性能。实验结果表明，随着重量比从 0.02 增加到 1.57，有效弹性模量从 180.5 兆帕增加到 310.3 兆帕，提高了 71.9%，负泊松比从-0.41 下降到-0.036，降低了 91.4%，证明了设计方法的有效性。设计方法和实验结果可为设计具有可定制力学性能的新型连续纤维增强元复合材料提供有效方法和重要信息。

Femtosecond laser drill high modulus CFRP multidirectional laminates with a segmented arc-based concentric scanning method

Chunyang Zhao, Zhenhua Ma, Jiayan Sun, Likuan Zhu

doi:10.1016/j.compstruct.2023.117769

利用基于分段圆弧的同心扫描方法，用飞秒激光钻削高模量 CFRP 多向层压板

High modulus carbon fiber reinforced plastic multidirectional laminates (HM-CFRP-MDL) are widely employed in the aerospace industry as crucial structural materials for satellites, rockets, and aircraft. However, it is difficult for the femtosecond laser to drill holes on HM-CFRP-MDL with the traditional concentric scanning method (CSM). To improve drilling quality and precision, this study proposes a segmented arc-based concentric scanning method (SAB-CSM) and investigates the interaction mechanisms between femtosecond lasers and CFRP. By adopting the proposed scanning method with optimized parameters, the overall average HAZ width can be decreased to 10 μm in different regions on the surface of the drilled hole, the hole taper can be reduced significantly, and the consistency across different layers can be improved. Compared to CSM, the HAZ width can be decreased by 40.8% (12.597μm to 7.464μm) and 50.3% (15.585μm to 7.748μm) in the regions where the angles between fiber direction and scanning direction are 45° and 90° respectively, and the taper can be reduced by 34.5% (0.084 to 0.055). Moreover, the SAB-CSM approach effectively decreases quality discrepancies between different layers, and substantially reduces those defects which results in smooth and uniform hole walls, facilitating synergistic removal of multidirectional carbon fibers and resin matrix.

高模量碳纤维增强塑料多向层压板（HM-CFRP-MDL）作为卫星、火箭和飞机的重要结构材料被广泛应用于航空航天领域。然而，传统的同心扫描法（CSM）很难在 HM-CFRP-MDL 上用飞秒激光钻孔。为了提高钻孔质量和精度，本研究提出了一种基于分段圆弧的同心扫描方法（SAB-CSM），并研究了飞秒激光与 CFRP 之间的相互作用机制。通过采用建议的扫描方法和优化参数，钻孔表面不同区域的整体平均 HAZ 宽度可降至 10 μm，钻孔锥度可显著减小，不同层间的一致性可得到改善。与 CSM 相比，HAZ 宽度可减少 40.8%（12.597μm 至 7.464μm），在纤维方向与扫描方向的夹角分别为 45° 和 90° 的区域，HAZ 宽度可减少 50.3%（15.585μm 至 7.748μm），锥度可减少 34.5%（0.084 至 0.055）。此外，SAB-CSM 方法还能有效减少不同层之间的质量差异，并大幅减少缺陷，从而获得光滑均匀的孔壁，促进多向碳纤维和树脂基体的协同去除。

Conductive nanoparticle-embedded carbon composite bipolar plates for vanadium redox flow batteries

Jaeheon Choe, Jun Woo Lim

doi:10.1016/j.compstruct.2023.117770

用于钒氧化还原液流电池的导电纳米粒子嵌入碳复合双极板

Electrochemical reduction and oxidation reactions of vanadium ions can enable efficient power management by a secondary battery, such as a vanadium redox flow battery (VRFB). To increase the energy efficiency of a VRFB system, the electrical resistance of the cell component, such as a bipolar plate, should be reduced. In this study, particles of polyaniline (PANI), a conductive polymer, were embedded in a carbon/epoxy composite by spraying on the prepreg surface to increase the electrical conductivity of the bipolar plate. The effect of the PANI particles on the electrical and mechanical properties was investigated. Furthermore, the optimum PANI content of 3 wt.% achieved an area-specific resistance of 16.7 mΩ·cm2, 55.2% lower than that of the neat specimen. The tensile strength was improved to 586 MPa, a 13.8% increase compared with the neat specimen. Finally, the cell performance of the fabricated bipolar plate was verified via permeability and single-cell charge/discharge tests.

钒离子的电化学还原和氧化反应可使钒氧化还原液流电池（VRFB）等二次电池实现高效的电源管理。为了提高钒氧化还原液流电池系统的能量效率，应降低电池组件（如双极板）的电阻。在本研究中，通过在预浸料表面喷涂的方式，将导电聚合物聚苯胺（PANI）颗粒嵌入碳/环氧树脂复合材料中，以提高双极板的导电性。研究了 PANI 粒子对电气和机械性能的影响。此外，3 wt.% 的最佳 PANI 含量可实现 16.7 mΩ-cm2 的面积特定电阻，比纯试样低 55.2%。拉伸强度提高到 586 兆帕，比纯试样提高了 13.8%。最后，通过渗透性和单电池充放电测试验证了制作的双极板的电池性能。

Vibration-based prediction of residual fatigue life for composite laminates through frequency measurements

Zhihong Liang, Karthik Ram Ramakrishnan, Ching-Tai NG, Zhifang Zhang, Jiyang Fu

doi:10.1016/j.compstruct.2023.117771

通过频率测量以振动为基础预测复合材料层压板的残余疲劳寿命

Fiber reinforced polymer (FRP) structures may experience cumulative fatigue damage during their service life which can lead to structural failure. This paper focuses on predicting the residual fatigue life of FRP structures using vibration parameters. The relationship between residual fatigue life and natural frequencies is examined through modal testing and fatigue measurements on FRP beam specimens. Two prediction methods; semi-empirical models and machine learning (ML) algorithms, are utilized. The semi-empirical models are derived from existing “residual stiffness” models based on the relationship between bending stiffness and flexural frequencies. ML algorithms Support Vector Machine (SVM) and Artificial Neural Network (ANN), are developed for fatigue life prediction. Experimental validation is performed using measured frequencies during fatigue testing of FRP beams. The ML algorithms can use multimode frequencies unlike single mode of semi-empirical models. The verification results show that the ML algorithms can be used to predict the residual fatigue life with the selection of the appropriate mode of frequency. The results show that ML algorithms outperform single-mode frequency inputs, and the use of higher modes of measured frequencies improves the precision of fatigue life prediction. An inverse algorithm based on SVM exhibits higher prediction accuracy and stability, even with limited training samples.

纤维增强聚合物（FRP）结构在其使用寿命期间可能会经历累积性疲劳损伤，从而导致结构失效。本文的重点是利用振动参数预测 FRP 结构的残余疲劳寿命。通过对玻璃钢梁试样进行模态测试和疲劳测量，研究了残余疲劳寿命与固有频率之间的关系。采用了两种预测方法：半经验模型和机器学习（ML）算法。半经验模型是根据弯曲刚度和挠曲频率之间的关系，从现有的 "残余刚度 "模型中推导出来的。为疲劳寿命预测开发了支持向量机（SVM）和人工神经网络（ANN）等 ML 算法。在对玻璃钢梁进行疲劳测试时，使用测得的频率进行了实验验证。与半经验模型的单一模式不同，ML 算法可以使用多模式频率。验证结果表明，通过选择适当的频率模式，ML 算法可用于预测残余疲劳寿命。结果表明，ML 算法优于单模式频率输入，使用较高的测量频率模式可提高疲劳寿命预测的精度。基于 SVM 的反算法即使在训练样本有限的情况下也能表现出更高的预测精度和稳定性。

Composites Part A: Applied Science and Manufacturing

Significantly Enhanced Tribological Properties of PTFE/PEEK Fabric Composites by Macroporous Metal−Organic Frameworks with Solid–Liquid Synergistic Lubrication

Mingkun Xu, Jing Zhang, Song Li, Tingmei Wang, Qihua Wang, Liming Tao, Peng Liu

doi:10.1016/j.compositesa.2023.107935

大孔金属有机框架固液协同润滑显著增强 PTFE/PEEK 织物复合材料的摩擦学性能

In this work, a macroporous oil-containing metal-organic framework material (CuBTCO) was prepared by a solvothermal method and vacuum impregnation. The tribological behaviors of PTFE/PEEK fabric composites (PFC) filled with CuBTCO were evaluated by the pin-on-disk tribometer under different loads. The coefficient of friction and mass wear rate of PFC containing 6 wt% CuBTCO (PFC-CuBTCO-6%) were 0.017 and 1.1×10-9 g/(Nm), respectively, which were reduced by 63.8% and 76.3% in comparison to PFC containing 6 wt% CuBTC under the same conditions. The excellent tribological properties of PFC-CuBTCO-6% are attributed to the solid–liquid synergistic lubrication between the adsorption film formed by the oleylamine released from CuBTCO and the PTFE-based transfer film. This work provides a novel approach for the structural design of solid–liquid synergistic lubrication of fabric liner composites.

本研究采用溶热法和真空浸渍法制备了一种大孔含油金属有机框架材料（CuBTCO）。在不同载荷下，采用针盘摩擦磨损试验仪对填充了 CuBTCO 的 PTFE/PEEK 纤维复合材料（PFC）的摩擦学行为进行了评估。在相同条件下，含 6 wt% CuBTCO 的 PFC（PFC-CuBTCO-6%）的摩擦系数和质量磨损率分别为 0.017 和 1.1×10-9 g/(Nm)，与含 6 wt% CuBTC 的 PFC 相比分别降低了 63.8% 和 76.3%。PFC-CuBTCO-6% 的优异摩擦学特性归功于 CuBTCO 释放的油胺形成的吸附膜与基于 PTFE 的转移膜之间的固液协同润滑作用。这项研究为织物衬垫复合材料的固液协同润滑结构设计提供了一种新方法。

Composites Part B: Engineering

Mechanism-based damage and failure of fused filament fabrication components

Iván Rivet, Narges Dialami, Miguel Cervera, Michele Chiumenti

doi:10.1016/j.compositesb.2023.111119

基于机理的熔融长丝制造组件的损坏和失效

Fused Filament Fabrication (FFF) is a polymer-based Additive Manufacturing (AM) technology that produces complex layered components. The characterization of the inherited orthotropic properties of FFF components and their failure analysis is a challenging endeavor. In this paper, the failure mechanics of FFF parts are studied via a Mechanism-Based (MB) damage material model. A MB damage criterion is developed by considering that the damage is driven by different failure modes identified according to the printing pattern. The developed criterion is compared to the Tsai–Wu (TW) criterion, which is commonly used for orthotropic materials with different strengths in tension and compression. Also, a MB cracking model that incorporates the orthotropic brittleness of FFF components is developed. The application of this cracking model requires solely two parameters to be defined. Numerical predictions of the cracking of two different experimental tests illustrate the similarities and the differences between the MB and TW damage criteria. The results demonstrate that the MB damage criterion can accurately match the experimental results, while the TW criterion fails to describe correctly the failure modes in complex 3D stress states.

熔融长丝制造（FFF）是一种基于聚合物的增材制造（AM）技术，可生产复杂的分层部件。表征 FFF 部件的继承正交特性并对其进行失效分析是一项具有挑战性的工作。本文通过基于机理（MB）的损伤材料模型对 FFF 零件的失效力学进行了研究。考虑到破坏是由根据印刷模式确定的不同破坏模式驱动的，因此制定了 MB 破坏准则。所开发的准则与蔡武（TW）准则进行了比较，后者通常用于具有不同拉伸和压缩强度的各向同性材料。此外，还开发了一种包含 FFF 组件正交脆性的 MB 裂纹模型。应用该开裂模型只需定义两个参数。对两种不同实验测试的开裂情况进行的数值预测说明了 MB 和 TW 损坏标准之间的异同。结果表明，MB 损伤准则能够准确匹配实验结果，而 TW 准则则无法正确描述复杂三维应力状态下的破坏模式。

来源：复合材料力学仿真Composites FEM

【新文速递】2023年12月6日复合材料SCI期刊最新文章

今日更新：Composite Structures 7 篇Composite StructuresComparison of local, gradient-enhanced and integral form of continuum damage approaches to strain localization in fiber reinforced compositesG. Gopinath, R.C. Batradoi:10.1016/j.compstruct.2023.117737纤维增强复合材料应变定位的局部、梯度增强和连续损伤积分形式方法比较Structures often have inserts and notches that cause stress concentration and consequent reduction in the load bearing capacity. The literature on numerical implementation of continuum damage mechanics (CDM) has generally focused on using local theories of damage.However, their use to analyze deformations of notched laminates that are prone to strain localization can cause numerical convergence issues that can be alleviated by employing a non-local theory. There are a few studies using a non-local damage theory for fiber-reinforced polymeric composites (FRPCs) and even fewer for strain localization in FRPCs. The non-local theories employ an equivalent (or effective or von Mises) strain often used in metal plasticity while most theories for studying failure of FRPCs use individual strain/stress components.Here, we compare predictions from local and nonlocal CDM approaches that are effective in studying strain localization in FRPCs. For the local approach, we employ a rate-dependent evolution relation. For the non-local approach, we either compute damage at a point as the weighted sum of damage at its neighbors that introduces a length scale into the problem, or employ a gradient-enhanced approach that also introduces a length scale. It is shown that numerical predictions from both the rate-dependent and the non-local theory alleviate to different degrees sensitivity of results to the finite element mesh used and the strain localization issues.Of these, a local rate-type approach is more convenient and cost effective.结构中经常会有嵌入物和缺口，这些嵌入物和缺口会导致应力集中，从而降低承载能力。有关连续损伤力学（CDM）数值实施的文献通常侧重于使用局部损伤理论。然而，使用局部损伤理论分析容易产生应变局部化的缺口层压板的变形会导致数值收敛问题，而采用非局部理论则可以缓解这些问题。针对纤维增强聚合物复合材料（FRPCs）使用非局部损伤理论的研究很少，而针对 FRPCs 中应变局部化的研究则更少。非局部理论采用金属塑性中常用的等效应变（或有效应变或冯米塞斯应变），而研究 FRPC 失效的大多数理论则采用单个应变/应力成分。对于局部方法，我们采用了与速率相关的演化关系。对于非局部方法，我们要么将某点的损伤计算为其邻近点损伤的加权和，从而在问题中引入长度尺度，要么采用同样引入长度尺度的梯度增强方法。结果表明，依赖速率理论和非局部理论的数值预测都在不同程度上缓解了结果对所使用的有限元网格和应变局部化问题的敏感性。Long-term bolt preload relaxation and contact pressure distribution in clamping anchorages for CFRP platesGuozhen Ding, Peng Feng, Yu Wang, Pengcheng Ai, Qinyu Wangdoi:10.1016/j.compstruct.2023.117780CFRP 板材夹紧锚固件中螺栓预紧力的长期松弛和接触压力分布Clamping anchorages are commonly used to anchor CFRP (carbon fiber reinforced polymer) plates, and the anchoring performance is significantly impacted by bolt preload. This research presents experimental and numerical investigations of long-term bolt preload relaxation in clamping anchorages for CFRP plates. First, a compression test was conducted to obtain the elastic modulus in the thickness direction of CFRP plates. Then, four types of relaxation tests (single bolt, planar and curved anchorage, external load effect, and thickened anchorage) were conducted, considering the effects of the number of CFRP plates, anchorage type, external load, and initial preload. The elastic interaction during the tightening process was also investigated. The contact pressure distribution was simulated through the finite element method, which is in good agreement with the results obtained from pressure papers. To fit relaxation test results and predict million-hour relaxation, different theoretical models were employed. The results indicate that the number of CFRP plates is crucial to preload relaxation, and the presence of CFRP plates introduces strong elastic interactions between bolts in the anchorage. Preload relaxation also increases under external loads and with the increase in initial preload. Curved anchorage has less bolt preload relaxation in the long term under external loads. Furthermore, thickened anchorages have a more uniform contact pressure distribution due to the improved pressure diffusion mechanism.夹紧锚固装置通常用于锚固 CFRP（碳纤维增强聚合物）板，而螺栓预紧力对锚固性能影响很大。本研究对 CFRP 板材夹紧锚固件中螺栓预紧力的长期松弛进行了实验和数值研究。首先，通过压缩试验获得 CFRP 板厚度方向的弹性模量。然后，考虑到 CFRP 板的数量、锚固类型、外部载荷和初始预紧力的影响，进行了四种松弛试验（单螺栓、平面和曲面锚固、外部载荷效应和加厚锚固）。此外，还研究了拧紧过程中的弹性相互作用。通过有限元方法模拟了接触压力分布，与压力论文获得的结果十分吻合。为了拟合松弛测试结果和预测百万小时松弛，采用了不同的理论模型。结果表明，CFRP 板的数量对预载松弛至关重要，CFRP 板的存在会在锚固件中的螺栓之间产生强烈的弹性相互作用。在外部荷载作用下，预紧松弛也随着初始预紧的增加而增加。在外部荷载的长期作用下，弧形锚固件的螺栓预紧松弛较小。此外，由于压力扩散机制得到改善，加厚锚固件的接触压力分布更加均匀。A new method of preparing lattice structures of continuous carbon fiber-reinforced thermoplasticsBaosheng Liu, Yulin Wang, Ruishen Lou, Yunxiang Yao, Xianglin Chen, Huimin Lidoi:10.1016/j.compstruct.2023.117781制备连续碳纤维增强热塑性塑料晶格结构的新方法The three-dimensional lattice sandwich structure of composite has attracted extensive attention in the engineering field due to its superior mechanical property and multifunctional designability. Developing technology that can guarantee both production cycle and cost remains challenging. In this work, an innovative forming technology based on 3D printing and hot folding process is presented to fabricate lattice sandwich structures of continuous fiber-reinforced thermoplastics. The prepared lattice sandwich structures show obvious competitiveness and superior material efficiency, which is reflected in high compressive strength (23.55 MPa/(g/cm3)) and specific compressive modulus (457.82 MPa/(g/cm3)). The simplified theoretical model and 3D progressive failure model are carried out to predict the compressive behaviors of the lattice sandwich structures, and the results are consistent with the experimental results. Additionally, the flexibility of the proposed method is demonstrated by fabricating various 3D structures.三维晶格夹层结构复合材料以其优越的机械性能和多功能设计性在工程领域受到广泛关注。开发既能保证生产周期又能降低成本的技术仍具有挑战性。本研究提出了一种基于三维打印和热折叠工艺的创新成型技术，用于制造连续纤维增强热塑性塑料的格子夹层结构。所制备的格子夹层结构具有明显的竞争力和优异的材料效率，具体表现为较高的抗压强度（23.55 兆帕/（克/立方厘米））和比压缩模量（457.82 兆帕/（克/立方厘米））。通过简化理论模型和三维渐进破坏模型来预测格子夹层结构的抗压行为，结果与实验结果一致。此外，还通过制造各种三维结构证明了所提方法的灵活性。Expanding the Mechanical and Mass-Transport combination for Bone Scaffolds: Through Stretched StructureXing Peng, Shiyu Li, Dongyang He, Junyan Li, Shuxin Qu, Zhongmin Jindoi:10.1016/j.compstruct.2023.117783扩展骨支架的机械和质量传输组合：通过拉伸结构Optimizing the mechanical and mass-transport properties of porous biomaterials simultaneously can be challenging, as they often correspond one-to-one through structure. For instance, increasing permeability by reducing relative density frequently leads to lower mechanical properties. In this study, we introduced a stretched structure to optimize the two properties simultaneously. Initially, the stretched scaffolds were evaluated at the same porosity, revealing that the elastic modulus and permeability of the stretched scaffold are approximately twice that of the original type. Subsequently, the orientation dependence of these properties was investigated. The results suggest that the stiffness of the stretched structure in the width direction is compromised, aligning with the mechanical properties of cortical bone in shaft bones. The permeability of the stretched structure exhibits significant anisotropy, with values much higher than those of original structure. Moreover, our biological experiments demonstrate that extremely stretched structures exhibit low and uneven curvature, potentially impeding cell growth. Hence, striking a balance between curvature and the stretching method employed is crucial. The stretching method can also be applied to other strut-based structures, enabling greater design flexibility in achieving a desirable mechanical and mass-transport combination, providing a foundation for high-performance artificial bone prostheses.同时优化多孔生物材料的机械性能和质量传输性能是一项挑战，因为它们往往通过结构一一对应。例如，通过降低相对密度来增加渗透性往往会导致机械性能降低。在这项研究中，我们引入了一种拉伸结构来同时优化这两种特性。首先，在相同孔隙率下对拉伸支架进行评估，结果表明拉伸支架的弹性模量和渗透性大约是原始支架的两倍。随后，研究了这些特性的取向依赖性。结果表明，拉伸结构在宽度方向上的刚度受到影响，这与轴骨中皮质骨的机械特性一致。拉伸结构的渗透性表现出明显的各向异性，其值远高于原始结构。此外，我们的生物实验证明，极度拉伸的结构会表现出较低且不均匀的曲率，可能会阻碍细胞生长。因此，在曲率和拉伸方法之间取得平衡至关重要。拉伸方法还可应用于其他基于支柱的结构，从而在实现理想的机械和质量传输组合方面具有更大的设计灵活性，为高性能人工骨假体奠定基础。Meso-viscoelastic modeling of solid propellant using XCT technology and virtual element methodBo Jin, Huiru Cui, Hualin Fandoi:10.1016/j.compstruct.2023.117784利用 XCT 技术和虚拟元素法建立固体推进剂的介观弹性模型This paper proposes a scheme to develop 2D mesoscale propellant models from X-ray computed tomography (XCT) images, including digital image processing (DIP)-based models and molecular dynamics (MD)-based models. In the MD-based approach, parametric models can be constructed by presuming that the particles are discs that satisfy the size distribution and volume fraction derived from XCT images of propellant. Based on the advantages of the virtual element method (VEM) for simulating the deformation of composite materials, this study obtains statistical information from XCT images to generate mesostructural models and compare their mechanical behaviors. Under the assumption of small deformation, the mesoscopic behaviors predicted by both mesostructural models are in good agreement, indicating that simpler MD-based models are adequate to characterize the overall viscoelastic properties of propellant. The impacts of propellant mesostructure parameters were addressed by using MD-based models.本文提出了一种从 X 射线计算机断层扫描（XCT）图像开发二维中尺度推进剂模型的方案，包括基于数字图像处理（DIP）的模型和基于分子动力学（MD）的模型。在基于 MD 的方法中，可以通过假定粒子为圆盘来构建参数模型，这些圆盘满足从推进剂 XCT 图像中得出的尺寸分布和体积分数。基于虚拟元素法（VEM）在模拟复合材料变形方面的优势，本研究从 XCT 图像中获取统计信息，生成中观结构模型，并比较其力学行为。在小变形假设下，两种介观结构模型预测的介观行为非常一致，表明基于 MD 的较简单模型足以表征推进剂的整体粘弹特性。利用基于 MD 的模型研究了推进剂介观结构参数的影响。Damage evolution in flax fibre composite under creep loadJianqun Hao, Alexandros Prapavesis, Stepan V. Lomov, C.A. Fuentes Rojas, Aart Willem Van Vuuredoi:10.1016/j.compstruct.2023.117786蠕变载荷下亚麻纤维复合材料的损伤演变This work aims to reveal the damage mechanisms and evolution in unidirectional flax fibre biocomposites when subjected to creep load. X-ray micro computed tomography and acoustic emission (AE) was used to monitor the failure progress during flexural creep tests. A correlation between the event clusters and directly observed damage modes was established based on coupons with expected failure mechanisms and then validated by computed tomography observations. The damage initiated from matrix cracking in the primary creep stage, and then fibre-matrix interface debonding combined with fibre pull-out occurred sequentially during the steady creep stage. In the tertiary creep stage, the explosive fibre fracture emerged and eventually triggered catastrophic failure. Considerably more AE events were detected during creep tests compared to those in quasi-static tests, which indicates that intensive damage is generated under creep load, and therefore causes the strength degradation. A good agreement was observed between the cumulative number of AE events and the increasing damage volume fraction over time determined by X-ray micro computed tomography during multi-step creep tests.这项研究旨在揭示单向亚麻纤维生物复合材料在承受蠕变载荷时的破坏机制和演变过程。在挠曲蠕变试验中，采用 X 射线显微计算机断层扫描和声发射（AE）技术监测破坏过程。根据具有预期破坏机制的试样，建立了事件群与直接观察到的破坏模式之间的相关性，然后通过计算机断层扫描观察进行验证。在一级蠕变阶段，损坏从基体开裂开始，然后在稳定蠕变阶段，纤维-基体界面脱粘与纤维拉出相继发生。在三级蠕变阶段，出现了爆炸性纤维断裂，并最终引发了灾难性破坏。与准静态试验相比，蠕变试验中检测到的 AE 事件要多得多，这表明在蠕变载荷作用下会产生密集的损伤，从而导致强度下降。在多步蠕变试验中，通过 X 射线显微计算机断层扫描测定的 AE 事件累积数量与随时间增加的损伤体积分数之间存在良好的一致性。Normal Contact Mechanism of Flexible Film/Substrate Bilayer Structure: Experimental and Numerical InsightShouyao Liu, Jian Wu, Shixue He, Bohan Yang, Benlong Su, Xuebo Yuan, Youshan Wangdoi:10.1016/j.compstruct.2023.117791柔性薄膜/基底双层结构的正常接触机制：实验与数值分析The film/substrate bilayer structure design plays a crucial role in enhancing the adaptability of flexible tactile sensors in complex environments. Nonetheless, as the cornerstone for machine tactility, the normal contact mechanism of the film/substrate bilayer structure remains elusive. Herein, the normal contact characteristics of polydimethylsiloxane film/sponge bilayer structure (PF/SBS) with different structural parameters, including substrate porosity, film mass ratio, and relative thickness between film and substrate, are investigated by experimental and numerical methods. The roles of the film and substrate structure parameters of PF/SBS in the normal contact process are analyzed by a cohesive contact model from the energy perspective. The results demonstrate that PF/SBS not only modulates the maximum normal force by substrate porosity but also exerts a substantial impact on the critical contact state by the film mass ratios. The contribution of film thickness to the critical separation state can be enhanced up to 90% with increasing relative thickness.薄膜/基板双层结构设计在增强柔性触觉传感器在复杂环境中的适应性方面发挥着至关重要的作用。然而，作为机器触感的基石，薄膜/基底双层结构的正常接触机制仍然难以捉摸。本文通过实验和数值方法，研究了具有不同结构参数（包括基底孔隙率、薄膜质量比、薄膜与基底的相对厚度）的聚二甲基硅氧烷薄膜/海绵双层结构（PF/SBS）的正常接触特性。通过内聚接触模型，从能量角度分析了 PF/SBS 的薄膜和基底结构参数在正常接触过程中的作用。结果表明，PF/SBS 不仅能通过基底孔隙率调节最大法向力，还能通过薄膜质量比对临界接触状态产生重大影响。随着相对厚度的增加，薄膜厚度对临界分离状态的贡献率最高可达 90%。来源：复合材料力学仿真Composites FEM