今日更新:Composite Structures 4 篇,Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 6 篇,Composites Science and Technology 2 篇
Experimental study of bonded, bolted, and hybrid bonded-bolted single lap shear joints with woven CFRP adherends
Mahdi Damghani, Mohammad Saad Khan, Gary A. Atkinson
doi:10.1016/j.compstruct.2024.117989
带编织 CFRP 粘接剂的粘接、螺栓和混合粘接-螺栓单搭接剪力连接的实验研究
This paper presents an extensive experimental performance study of bonded joints (BJs), only bolted joints (OBJs) and hybrid bonded-bolted joints (HJs). For each joint type, three test configurations are considered: namely, short, medium and long overlap lengths. In each case, the adherends comprise quasi-isotropic twill woven CFRP. For each joint type/overlap length combination, three specimens are tested for statistical representation. HJs demonstrate 1.4, 1.5 and 1.5 times higher failure load and 1.5, 1.6 and 1.9 times higher stiffness than OBJs, for short, medium and long overlap, respectively. In all test cases, HJs outperform BJs except for short overlaps where BJs outperform both HJs and OBJs. OBJs perform poorly in terms of failure load and Hooke’s stiffness. Nevertheless, due to bearing deformation at bolt hole locations, OBJs experience higher failure displacements than BJs and HJs leading to a desirable energy absorption mechanism compared to HJs and BJs. This is thanks to the bearing failure mode of the joint despite much lower failure load in OBJs. It was found that increasing the overlap length generally benefits BJs. However, for medium length overlap specifically, HJs show better performance than BJs. Stress–strain behaviours show a linear behaviour for all test groups with significant joint rotation for OBJs compared to BJs and HJs. Failure mechanism studies presented in the paper show that BJs fail in cohesive failure mode for all test groups. OBJs fail in bearing mode, which is followed by net tension failure. OBJs experience matrix cracking and delamination at bolt hole locations. On the contrary, HJs experience considerably less bearing failure at bolt holes due to the load bearing contribution from the adhesive.
本文对粘接接头(BJ)、纯螺栓接头(OBJ)和粘接-螺栓混合接头(HJ)进行了广泛的性能实验研究。每种接头类型都考虑了三种测试配置:即短、中和长重叠长度。在每种情况下,粘合剂都由准各向同性的斜纹编织 CFRP 组成。对于每种连接类型/重叠长度组合,都测试了三个试样以进行统计。在短、中、长重叠情况下,HJ 的破坏载荷分别比 OBJ 高 1.4、1.5 和 1.5 倍,刚度分别比 OBJ 高 1.5、1.6 和 1.9 倍。在所有测试情况下,HJ 均优于 BJ,但在短重叠情况下,BJ 优于 HJ 和 OBJ。OBJ 在破坏载荷和胡克刚度方面表现较差。然而,由于螺栓孔位置的轴承变形,OBJ 比 BJ 和 HJ 具有更高的失效位移,因此与 HJ 和 BJ 相比,OBJ 具有更理想的能量吸收机制。这要归功于接头的轴承失效模式,尽管 OBJ 的失效载荷要低得多。研究发现,增加重叠长度通常对 BJ 有利。然而,具体到中等长度的重叠,HJ 的性能要优于 BJ。应力-应变行为在所有测试组中都表现为线性行为,与 BJ 和 HJ 相比,OBJ 的关节旋转明显。论文中的失效机理研究表明,在所有测试组中,BJ 均以内聚失效模式失效。OBJ 以轴承模式失效,随后是净拉力失效。OBJ 在螺栓孔位置出现基质开裂和分层。相反,由于粘合剂的承载作用,HJ 在螺栓孔处发生的承载失效要少得多。
Complex CFRP damage detection with dual multiscale 1DCNNs and self-selective fusion technique of guided waves
Yunlai Liao, Yuan Huang, Yihan Wang, Minhuang Wu, Fanghong Zhang, Xinlin Qing
doi:10.1016/j.compstruct.2024.117993
利用双多尺度 1DCNN 和导波自选择融合技术检测复杂 CFRP 损伤
This article presents an innovative damage detection method, named DMS1DCNNs, based on new dual multiscale one-dimensional convolutional neural networks (MS1DCNNs) and a novel self-selective fusion technique for damage localization and quantification in complex carbon fiber reinforced plastic (CFRP) structures. Firstly, a new multiscale piecewise aggregate approximation algorithm (MIPA) is proposed to compress the guided wave (GW) signals and extract damage features at various time scales. Considering that signals from low-information sensing paths may interfere with the diagnostic performance of the model, a new method for self-selective fusion of GW sensing paths is proposed. This method can automatically fuse paths with more damage information and remove paths with less damage information. Then, a new DMS1DCNNs model is presented, capable of obtaining multiscale damage features in GW signals from both data and network levels. The model takes GW data as input and employs regression methods for direct prediction of the damage location and size. Finally, the method is validated using the GW testbed, and the mean relative error of location on complex CFRP is 8.32 % and the mean absolute error of quantification is 1.20 mm, superior to other state-of-the-art methods.
本文基于新型双多尺度一维卷积神经网络(MS1DCNNs)和新型自选择融合技术,提出了一种创新的损伤检测方法(DMS1DCNNs),用于复杂碳纤维增强塑料(CFRP)结构的损伤定位和量化。首先,提出了一种新的多尺度片状集 合近似算法(MIPA),用于压缩导波(GW)信号并提取不同时间尺度的损伤特征。考虑到来自低信息传感路径的信号可能会干扰模型的诊断性能,提出了一种自选择融合导波传感路径的新方法。这种方法可以自动融合损伤信息较多的路径,并移除损伤信息较少的路径。然后,提出了一种新的 DMS1DCNNs 模型,该模型能够从数据和网络两个层面获取全球大气气象数据信号中的多尺度损伤特征。该模型以 GW 数据为输入,采用回归方法直接预测损伤位置和大小。最后,该方法通过 GW 试验台进行了验证,在复杂 CFRP 上的定位平均相对误差为 8.32 %,量化平均绝对误差为 1.20 mm,优于其他最先进的方法。
Prediction of transverse permeability in representative volume elements with closely arranged fibers through the application of delaunay-triangulation and electrical-circuit analogy
Hyeonseong Jo, Sangyoon Bae, Hyunsoo Hong, Wonvin Kim, Seong Su Kim
doi:10.1016/j.compstruct.2024.117984
通过应用德劳内三角测量法和电路类比法预测具有紧密排列纤维的代表性体积元素中的横向渗透率
The distribution of fibers in composite manufacturing significantly affects fiber bundle permeability, a crucial factor for resin impregnation and void formation, which determines final product quality. However, as the industry increasingly seeks composite materials characterized by high fiber volume fractions, the existing numerical analysis methodologies employed for predicting permeability require a considerable computational cost. In this study, the permeability prediction model was developed using a fluid domain simplification technique based on Delaunay triangulation. The inter-fiber flow was approximated using a lubrication model, and continuity was ensured using a circuit analogy. This model can explain stochastic permeability characteristics according to fiber distribution and accurately predicts the permeability regardless of the distance between fibers. Additionally, compared to existing computational fluid dynamics simulations, it achieved an incredible accuracy of 97.74% and reduced computational costs by an average of 1,700 times.
纤维在复合材料生产中的分布对纤维束的渗透性有很大影响,而纤维束的渗透性是树脂浸渍和空隙形成的关键因素,决定着最终产品的质量。然而,随着业界对高纤维体积分数复合材料的需求与日俱增,用于预测渗透性的现有数值分析方法需要相当高的计算成本。本研究采用基于 Delaunay 三角剖分的流体域简化技术开发了渗透性预测模型。纤维间的流动使用润滑模型进行近似,并使用电路类比确保连续性。该模型可根据纤维分布解释随机渗透特性,并准确预测渗透率,而不受纤维间距的影响。此外,与现有的计算流体动力学模拟相比,该模型的精确度达到了惊人的 97.74%,计算成本平均降低了 1,700 倍。
Characterization and prediction of tensile properties of carbon fiber-reinforced thermoplastics composed of hybrid short carbon fiber/PA6 fiber nonwoven mats
Qian Gao, Yi Wan, Haowen Wei, Jun Takahashi
doi:10.1016/j.compstruct.2024.117996
由混合短碳纤维/PA6 纤维无纺毡组成的碳纤维增强热塑性塑料的拉伸特性表征与预测
Hybrid carbon fiber/resin fiber nonwoven mats are considered as a highly promising application of recycled carbon fibers due to their low cost and simple synthesis process. However, the mechanical properties of hybrid nonwoven mats are subject to uncertainties due to nonuniformity of fiber orientations during production procedures, which restricts their use in structural components. This study investigates the characteristics of various types of hybrid nonwoven mats with different volume fractions and fiber orientation distributions. Notably, the investigation yields noteworthy tensile properties, exemplified by a tensile strength of 367.20 MPa and a stiffness of 32.85 GPa, when the volume fraction is 28.9%. Tensile properties of the hybrid nonwoven mats and their fluctuations are then analyzed through statistical analyses. A three-dimensional microstructure-based fiber network model is established using the Monte Carlo method to represent the statistical and stochastic properties of the material. Furthermore, a prediction method of tensile properties based on microstructural properties in the model is proposed, which shows good agreement with all experimental results for adjustments of the volume fraction of carbon fibers, distribution of fiber lengths, and anisotropy of the materials, significantly reducing the experimental burden for optimization research. The tensile characteristics of composites are reliably anticipated with a nominal error margin below 10%. Additionally, this prediction method enables the prediction of scatter and stable standard deviation, making it possible to apply hybrid nonwoven mats in recycling and industrial processes.
碳纤维/树脂纤维混合非织造毡因其低成本和简单的合成工艺而被认为是再生碳纤维的一种极具前景的应用。然而,由于生产过程中纤维取向的不均匀性,混合非织造毡的机械性能存在不确定性,限制了其在结构部件中的应用。本研究调查了具有不同体积分数和纤维取向分布的各类混合无纺布毡的特性。值得注意的是,这项研究获得了显著的拉伸特性,例如,当体积分数为 28.9% 时,拉伸强度为 367.20 兆帕,刚度为 32.85 千兆帕。然后通过统计分析分析了混合无纺毡的拉伸性能及其波动。使用蒙特卡罗方法建立了基于三维微结构的纤维网模型,以表示材料的统计和随机特性。此外,还提出了一种基于模型中微观结构特性的拉伸特性预测方法,该方法在调整碳纤维体积分数、纤维长度分布和材料各向异性时与所有实验结果显示出良好的一致性,大大减轻了优化研究的实验负担。复合材料的拉伸特性得到了可靠的预测,误差率低于 10%。此外,这种预测方法还能预测散度和稳定的标准偏差,从而使混合无纺毡在回收和工业流程中的应用成为可能。
Studies on 8.4 W/m·K thermally conductive silicone rubber with high compressibility, high electrical insulation, high thermal reliability, and low cost
Jianping Liu, Zhiming Fang, Chenlu Bao.
doi:10.1016/j.compositesa.2024.108100
研究具有高压缩性、高电绝缘性、高热稳定性和低成本的 8.4 W/m-K 导热硅橡胶
Thermally conductive silicone rubber (TCSR) has been widely used to enhance heat dissipation in electronics and energy storage devices. Currently, it is a challenge to produce TCSR which combines high thermal conductivity, high compressibility, high thermal reliability, high electrical insulation, and low cost. Here, we report a state-of-the-art TCSR which achieves such a combination. Owing to the optimized alumina gradation, the loading level of alumina in the TCSR reaches 96 wt%. The TCSR reaches a high and isotropic thermal conductivity of 8.4 W/m·K, a high compression ratio of 48 % (under a pressure of 6 psi or 42.4 kPa), and a high dielectric strength (>6 kV/mm). After heating at 180 °C for 100 h, little oil bleeding is observed. More importantly, these properties remain stable (variation < 10 %) after 2000 h of thermal aging at 135 °C, indicating high thermal reliability.
导热硅橡胶(TCSR)已被广泛用于提高电子设备和储能设备的散热性能。目前,生产兼具高导热性、高可压缩性、高热稳定性、高电绝缘性和低成本的导热硅橡胶是一项挑战。在此,我们报告了一种最先进的 TCSR,它实现了这样的组合。由于优化了氧化铝级配,TCSR 中的氧化铝含量达到 96 wt%。这种 TCSR 的各向同性热导率高达 8.4 W/m-K,压缩比高达 48%(压力为 6 psi 或 42.4 kPa),介电强度也很高(大于 6 kV/mm)。在 180 °C 下加热 100 小时后,几乎没有渗油现象。更重要的是,这些特性在 135 °C 下经过 2000 小时的热老化后仍然保持稳定(变化 < 10 %),表明热可靠性很高。
Electronic metal-support interaction-induced space charge polarization for boosting photoelectrochemical water splitting
Chengming Zhang, Jianli Chen, Meng Wang, Haibao Zhu, Jun Ma, Huanhuan Wu, Huihui Ding, Xiaolong Fang, Fazhi Xie, Zhi Tang, Xiaoli Zhao, Yi Ding, Hewen Liu, Xiufang Wang
doi:10.1016/j.compositesb.2024.111327
电子金属-支撑物相互作用诱导的空间电荷极化促进光电化学水分离
Overcoming the inherent transportation of charge constraint of the photoanode has been critical for seeking feasible photoelectrochemical (PEC) water splitting. Here, we propose to utilize electron metal-support interactions (EMSI) between Cu nanoparticles (NPs) and N-C support for modifying the electronic structure of CuNPs-N-C/SnS2 photoanode and analyze the impact of EMSI on the process of PEC water splitting. The combination of detailed theoretical simulation calculations and comprehensive characterizations indicates that the charge imbalance induced by EMSI within the CuNPs-N-C and SnS2 interfaces results in an enhanced interfacial polarized electric field and boosts the separation of photo-induced carriers at the CuNPs-N-C and SnS2 interfaces. The optimal CuNPs-N-C/SnS2 photoanode displays remarkable properties with a considerably upgraded photocurrent of 2.33 mA cm−2 at 1.23 VRHE, which is 6.30 beyond the value of SnS2 (0.37 mA cm−2). This work paves a way to developing high-performance photoanodes for efficient PEC water splitting.
克服光阳极固有的电荷传输限制对于寻求可行的光电化学(PEC)水分离至关重要。在此,我们提出利用铜纳米粒子(NPs)与 N-C 支持物之间的电子金属-支持物相互作用(EMSI)来改变 CuNPs-N-C/SnS2 光阳极的电子结构,并分析 EMSI 对 PEC 水分离过程的影响。详细的理论模拟计算和全面的表征相结合表明,EMSI 在 CuNPs-N-C 和 SnS2 界面上引起的电荷不平衡导致界面极化电场增强,并促进了光诱导载流子在 CuNPs-N-C 和 SnS2 界面上的分离。最佳的 CuNPs-N-C/SnS2 光阳极具有显著的特性,在 1.23 VRHE 下的光电流高达 2.33 mA cm-2,比 SnS2(0.37 mA cm-2)高出 6.30 倍。这项工作为开发用于高效 PEC 水分离的高性能光阳极铺平了道路。
Predicting failure in injection-moulded short-fibre subcomponents under varied environmental conditions through fracture mechanics
Yuki Fujita, Satoshi Noda, Junichi Takahashi, Emile S. Greenhalgh, Soraia Pimenta
doi:10.1016/j.compositesb.2024.111343
通过断裂力学预测不同环境条件下注塑短纤维子组件的失效情况
Injection-moulded short-fibre composites are lightweight materials suitable for high-volume applications; however, current simulation methods (based on failure initiation criteria) to design components using these materials cannot yet accurately predict failure. This work presents a methodology to predict failure of injection-moulded short-glass-fibre reinforced thermoplastic (IM-SFRP) composite subcomponents, based on experimentally measured properties. The material's fracture toughness was characterized by Compact Tension tests for different fibre orientations and environmental conditions. These fracture toughnesses were used as the input for cohesive zone modelling in Finite Element simulations of subcomponents representative of automotive applications, coupled with fibre orientation fields predicted by an injection-moulding process simulation. These coupled simulations presented excellent agreement with the experimental results for subcomponents both in terms of (i) the peak load (highlighting the importance of accounting for the finite fracture toughness of the material to accurately predict the ultimate failure of the subcomponents), and (ii) the pre- and post-peak sequence of failure events (verified using fractographic analyses). This work also verified the applicability of temperature-moisture equivalence, not only for material characterisation using coupons including the material's fracture toughness, but also for the mechanical response of subcomponents until final failure. The methodology demonstrated in this paper contributes to designing safer and more efficient damage-tolerant IM-SFRP components.
注塑短纤维复合材料是适合大批量应用的轻质材料;然而,目前使用这些材料设计组件的模拟方法(基于失效启动标准)还不能准确预测失效。本研究提出了一种基于实验测量属性预测注塑短玻纤增强热塑性塑料(IM-SFRP)复合材料子组件失效的方法。材料的断裂韧性是通过不同纤维取向和环境条件下的紧凑拉伸试验确定的。这些断裂韧性被用作汽车应用子部件有限元模拟中内聚区建模的输入,并与注塑成型工艺模拟预测的纤维取向场相结合。这些耦合模拟在以下两个方面与实验结果非常吻合:(i) 峰值载荷(突出了考虑材料有限断裂韧性对准确预测子部件最终失效的重要性);(ii) 失效事件的前后峰值序列(使用断裂分析进行验证)。这项工作还验证了温度-湿度等效的适用性,不仅适用于使用包括材料断裂韧性在内的试样进行材料表征,还适用于直到最终失效的子组件机械响应。本文展示的方法有助于设计更安全、更高效的 IM-SFRP 容损组件。
Quantitative ultrasonic imaging of weave structure in textile composites
Xiaoyu Yang, Mathias Kersemans, Zheng Fan
doi:10.1016/j.compositesb.2024.111310
纺织复合材料编织结构的定量超声波成像
Textile composites owe their desirable mechanical properties to the intricate fabric architecture. However, manufacturing deviations can influence these attributes, significantly affecting their mechanical performance. Thus, ensuring the quality and structural integrity of fabric architectures has become pivotal, leading to the advancement of ultrasonic non-destructive testing techniques. However, existing techniques, primarily tailored for unidirectional laminates, often struggle with weave pattern extraction, given the complex features of fabric laminates. To address this gap, a pulse-echo ultrasound coupled to a 2D analytic-signal analysis is proposed. The 2D analytic-signal methodology autonomously discerns the complex ultrasound features from fabric laminates, streamlining weave pattern analysis. The study showcases ply-by-ply reconstruction of local weave patterns of fabric laminates with nominal layups of [#(0/90)]8 and [#(+45/−45 )#(0/90)]5s, respectively. The efficacy of the methodology is ascertained through quantitative metrics, highlighting its innovative potential for through-depth extraction of local weave patterns in a swift and automated manner.
纺织复合材料之所以具有理想的机械性能,是因为其复杂的织物结构。然而,制造过程中的偏差会影响这些属性,从而严重影响其机械性能。因此,确保织物结构的质量和结构完整性变得至关重要,从而推动了超声波无损检测技术的发展。然而,鉴于织物层压板的复杂特性,主要针对单向层压板量身定制的现有技术在提取编织图案方面往往力不从心。为了弥补这一不足,我们提出了脉冲回波超声与二维分析信号分析相结合的方法。二维分析信号方法可自主识别织物层压板的复杂超声波特征,从而简化织纹分析。研究展示了逐层重建织物层压板的局部编织图案,其标称层叠分别为 [#(0/90)]8 和 [#(+45/-45 )#(0/90)]5s 。该方法的功效通过定量指标得以确定,突出了其在快速、自动地深入提取局部编织图案方面的创新潜力。
Controlled interlaminar crack initiation in thin notched laminated thermoplastic composites under impact loading: A first step towards unitary layer recovery
Awen Bruneau, Mathieu Imbert, Michael May
doi:10.1016/j.compositesb.2024.111322
冲击载荷下薄型缺口层压热塑性复合材料中受控制的层间裂纹起始:向单元层恢复迈出第一步
The recycling of composite materials is nowadays a major challenge as it is systematically associated with a downcycling due to the reduction of the fiber length. However, recent works demonstrated that the delamination-based recovery of the unitary layers of laminated structures with preserved mechanical properties is possible under dedicated loading conditions. The presented work aims at investigating this innovative process and in particular the interlaminar crack initiation from a straight notch milled in the material by using an impact loading; further crack extension to recover the complete lamina being the following step of the process. A Split Hopkinson Bar setup has been used in a Direct Impact configuration and a dedicated test setup has been implemented to impose translational and rotational kinematics to the impacted side of the tested specimens in order to enable crack initiation and propagation over a few millimeters. Imposing translational kinematics to the impacted side of the specimen has been shown to induce cracks in a reproducible manner. Numerical simulation results explain the more favorable conditions provided by the translational kinematic.
如今,复合材料的回收利用是一项重大挑战,因为纤维长度的减少会导致复合材料的回收利用率降低。然而,最近的研究表明,在特定的加载条件下,基于分层的层压结构单元层的恢复是可能的,并能保持其机械性能。本文介绍的工作旨在研究这一创新工艺,特别是通过使用冲击加载,从材料上铣出的直切口处引发层间裂纹;该工艺的下一步是进一步扩展裂纹,以恢复完整的层状结构。在直接冲击配置中使用了分体式霍普金森棒装置,并实施了专门的测试装置,对测试试样的冲击侧施加平移和旋转运动学,以实现裂纹在几毫米范围内的萌发和扩展。对试样受冲击的一侧施加平移运动学已被证明能以可重复的方式诱发裂纹。数值模拟结果解释了平移运动学提供的更有利条件。
Mechanically robust multifunctional starch films reinforced by surface-tailored nanofibrillated cellulose
Jiarong Tian, Yingqi Kong, Shaoping Qian, Zhaoyan Zhang, Yingbo Xia, Zhijie Li
doi:10.1016/j.compositesb.2024.111339
由表面定制的纳米纤维素增强的机械坚固的多功能淀粉薄膜
The objective of this study was to develop a transparent, mechanically robust, and fully biodegradable film made of sweet potato starch (SPS) reinforced with nanofibrillated cellulose (NFC) to serve as a potential alternative for packaging. Various surface modifications were applied to NFC using urea/NaOH (UA), oxalic acid (OA), citric acid (CA), and (3-mercaptopropyl) trimethoxysilane (MT). SPS/NFC blend was innovatively treated by ball-milling, incorporating different concentrations (2–10 wt%) of surface-modified NFC and calcium gluconate as a modifier. Interestingly, the solution-cast blend films possessed improved tensile strength, tensile modulus, crystallinity, barrier property and hydrophobicity after NFC additions. More importantly, ball-milling promoted the physical combination of starch and NFC and generated metal-organic supramolecular interaction between –OH and Ca2+. In particular, the SPS-OA/NFC6 composite film exhibited remarkable improvements in tensile strength and tensile modulus, increasing from 1.46 MPa and 6.04 MPa–13.7 MPa and 531.33 MPa, respectively, compared to the neat SPS film. The contact angle of the SPS/CA-NFC6 film was approximately 79% higher than that of the pure SPS film. Generally, the optimal NFC addition was 6 wt%. This study provides guidance for the production of a new type of starch-based material with high mechanical strength and transparency.
本研究旨在开发一种透明、机械坚固且可完全生物降解的薄膜,该薄膜由纳米纤维素(NFC)增强的甘薯淀粉(SPS)制成,可作为一种潜在的包装替代品。使用尿素/NaOH(UA)、草酸(OA)、柠檬酸(CA)和(3-巯基丙基)三甲氧基硅烷(MT)对 NFC 进行了各种表面改性。通过球磨创新性地处理了 SPS/NFC 混合物,加入了不同浓度(2-10 wt%)的表面改性 NFC 和葡萄糖酸钙作为改性剂。有趣的是,添加 NFC 后,溶液浇铸混合薄膜的拉伸强度、拉伸模量、结晶度、阻隔性和疏水性都得到了改善。更重要的是,球磨促进了淀粉和 NFC 的物理结合,并在 -OH 和 Ca2+ 之间产生了金属有机超分子相互作用。与纯 SPS 薄膜相比,SPS-OA/NFC6 复合薄膜的拉伸强度和拉伸模量有了显著提高,分别从 1.46 兆帕和 6.04 兆帕提高到 13.7 兆帕和 531.33 兆帕。SPS/CA-NFC6 薄膜的接触角比纯 SPS 薄膜高出约 79%。一般来说,最佳的 NFC 添加量为 6 wt%。这项研究为生产具有高机械强度和透明度的新型淀粉基材料提供了指导。
A novel 3D topological metamaterial for controllability of polarization-dependent multilayer elastic waves
Guifeng Wang, Tian Wang, Zhenyu Chen, Zhiwen Zhu, C.W. Lim
doi:10.1016/j.compositesb.2024.111341
用于控制偏振相关多层弹性波的新型三维拓扑超材料
The achievement of high-quality wave manipulation and energy concentration has always been considered as state-of-the-art technologies, especially for integrated photonics, acoustics, and mechanics. The exploration of the topological phase of matter provides abundant design tools for robust waveguiding that is immune to backscattering at small defects and sharp bends. Recent research has extended the elastic wave manipulation from 2D edge waveguiding to 3D planar waveguiding. However, most of them are limited to single-mode and single-frequency wave propagation along the designed plane. This paper introduces a novel 3D topological metamaterial structure whose geometrical parameters are specifically configured to obtain dual-mode topological states at distinct frequencies. Parametric studies are presented to demonstrate the controllability of bandgaps and to provide a design principle for preventing the effects of unwanted modes. Topological interface modes with either high group velocity or near-zero group velocity along the z direction are found. Full-scale finite element simulations are presented to uncover the elastic wave propagation behavior. The interesting layer-locked and layer-unlocked waveguiding based on excitation polarization and frequency for both straight path and zig-zag path are demonstrated. The outcomes of this work suggest abundant potential applications related to elastic wave control such as wave filters, energy harvesters, mechanical computers, and the like. This work may also help inspire future research on more complex and sophisticated multi-mode waveguiding in 3D spaces.
实现高质量的波操纵和能量集中一直被认为是最先进的技术,尤其是在集成光子学、声学和力学方面。对物质拓扑相的探索提供了丰富的设计工具,用于设计坚固耐用的波导,这种波导在小缺陷和急弯处不会产生反向散射。最近的研究已将弹性波操纵从二维边缘波导扩展到三维平面波导。然而,这些研究大多局限于单模和单频波沿设计平面的传播。本文介绍了一种新型三维拓扑超材料结构,其几何参数经过专门配置,可在不同频率下获得双模拓扑状态。本文介绍了参数研究,以证明带隙的可控性,并提供了防止不需要的模式影响的设计原则。研究发现拓扑界面模式沿 Z 方向具有高群速度或接近零的群速度。全尺寸有限元模拟揭示了弹性波的传播行为。基于激发极化和频率,演示了直行和之字形路径上有趣的层锁定和层解锁波导。这项工作的成果表明,与弹性波控制相关的应用潜力巨大,例如波滤波器、能量收集器、机械计算机等。这项工作还有助于启发未来在三维空间中开展更复杂、更精密的多模波导研究。
Coupling relationship between molecule structure at silica/silicone gel interfaces and ionic conductivity in polymer composites
Ying Lin, Liye Dong, Chuanle Heng, Kai Chen, Yuhao Liu
doi:10.1016/j.compscitech.2024.110507
二氧化硅/硅凝胶界面分子结构与聚合物复合材料离子传导性之间的耦合关系
Herein, the coupling relationship between molecule structure and ion conductivity in silica filled silicone gel are established. Based on the broadband dielectric spectrum, the concentration of ion charges and ions diffusion coefficients, two key roles for ion conductivity, are calculated. The concentration of ion charges is increased by about four orders of magnitude after the addition of silica. Because of the more short-length chains conformations and more amorphous regions at interfaces, the chains at interfaces are easier to rearrange with higher relaxation frequency, which enhances the ions diffusion process and contributes to negative decoupling exponents between the interface molecule relaxations and ion diffusion coefficients in silicone gel composites. With the increase of fumed silica loading, the ionic conductivity increases first and decreases owing to percolation phenomenon about silica dispersion. Meanwhile, decoupling exponents of the interface molecules are closer to 0. Our findings deepen the understanding how the interface structures act on ions conductivity in insulating polymer composites, which is critical to rationally design interface structures for manipulating the insulation performances.
本文建立了二氧化硅填充硅凝胶中分子结构与离子导电性之间的耦合关系。根据宽带介电频谱,计算了离子电荷浓度和离子扩散系数这两个对离子导电性起关键作用的参数。加入二氧化硅后,离子电荷浓度增加了约四个数量级。由于界面上有更多的短链构象和更多的无定形区域,界面上的链更容易以更高的弛豫频率重新排列,从而增强了离子的扩散过程,并导致硅凝胶复合材料中界面分子弛豫与离子扩散系数之间的负解耦指数。随着气相二氧化硅负载量的增加,离子电导率先增加后降低,这是由于二氧化硅分散的渗流现象造成的。我们的发现加深了人们对绝缘聚合物复合材料中界面结构如何影响离子导电性的理解,这对于合理设计界面结构以控制绝缘性能至关重要。
High-performance shape memory epoxy resin with high strength and toughness: Prepared by introducing hydrogen bonds through polycaprolactone and low melting point alloy
Zhiwei Tuo, Kunzhi Chen, Qiang Zhou, Yubo Wang, Qiushi Wang, Yuyu Zhang, Zhaohua Lin, Yunhong Liang
doi:10.1016/j.compscitech.2024.110510
具有高强度和韧性的高性能形状记忆环氧树脂:通过聚己内酯和低熔点合金引入氢键制备而成
Epoxy resin (EP) as common polymers have attracted much attention in the field of shape memory materials due to their excellent properties. However, epoxy-based shape memory polymers suffer from a trade-off between strength, toughness, variable stiffness capability and shape memory properties, and thus are subject to significant limitations in their applications. In this paper, we propose a method to prepare epoxy composites with high strength and toughness and high shape memory properties by introducing a lot of hydrogen bonds. Hydrogen bonding is generated through polycaprolactone (PCL) induced EP phase separation. A low melting point alloy (L) was also added to enhance the shape memory properties of the composites. The synthesis mechanism of EP and the formation mechanism of hydrogen bonding were revealed. The effects of the introduction of hydrogen bonding on the mechanical properties, stiffness and shape memory properties of the composites were investigated. New ideas and design directions are provided for the optimisation of modification of high-performance shape memory epoxy resins.
环氧树脂(EP)作为常见的聚合物,因其优异的性能在形状记忆材料领域备受关注。然而,环氧基形状记忆聚合物在强度、韧性、可变刚度能力和形状记忆性能之间存在权衡问题,因此在应用中受到很大限制。本文提出了一种通过引入大量氢键来制备具有高强度、高韧性和高形状记忆性能的环氧树脂复合材料的方法。氢键是通过聚己内酯(PCL)诱导 EP 相分离产生的。此外,还添加了低熔点合金(L),以增强复合材料的形状记忆性能。研究揭示了 EP 的合成机理和氢键的形成机理。研究了氢键的引入对复合材料机械性能、刚度和形状记忆性能的影响。为优化高性能形状记忆环氧树脂的改性提供了新的思路和设计方向。