今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 2 篇,Composites Science and Technology 1 篇
Structurally embedded gradient index lens for guided wave amplification in polymers
Hrishikesh Danawe, Didem Ozevin, Serife Tol
doi:10.1016/j.compstruct.2023.117868
用于聚合物导波放大的结构嵌入式梯度指数透镜
Guided wave inspection is a commonly used technique in structural health monitoring, yet there are challenges associated with ultrasonic inspection of polymeric structures due to high material damping resulting in wave attenuation. In this work, we present a structurally embedded gradient-index phononic crystal (GRIN-PC) lens for elastic wave amplification in polyvinyl chloride (PVC) structures to overcome the attenuation problem in long-range guided wave inspection. The GRIN-PC lens is made up of cylindrical brass stubs of varying heights or diameters embedded in the PVC base structure, providing a hyperbolic secant profile of refractive index distribution transverse to the wave propagation direction. We first demonstrate flexural wave focusing in a PVC plate by implementing the embedded lens design via numerical simulations and experiments. Then, the embedded GRIN-PC lens concept is implemented to PVC pipe for multi-mode wave focusing using a single lens design which is studied through numerical simulations. The proposed GRIN-PC lens design reduces the amplitude decay due to material damping by amplifying the wave energy at the focal regions of the lens. The embedded lens concept developed for polymers can also benefit other applications requiring the transmission of wave energy in structures with high material damping.
导波检测是结构健康监测中的一种常用技术,但由于高材料阻尼会导致波衰减,因此在对聚合物结构进行超声波检测时面临着挑战。在这项工作中,我们提出了一种结构嵌入式梯度指数声子晶体(GRIN-PC)透镜,用于聚氯乙烯(PVC)结构中的弹性波放大,以克服远距离导波检测中的衰减问题。GRIN-PC 透镜由嵌入聚氯乙烯基底结构的不同高度或直径的圆柱形黄铜短棒组成,提供了横向于波传播方向的双曲正割折射率分布轮廓。我们首先通过数值模拟和实验演示了聚氯乙烯板中的挠性波聚焦,实现了嵌入式透镜设计。然后,通过数值模拟研究,将嵌入式 GRIN-PC 透镜概念应用于 PVC 管,利用单透镜设计实现多模波聚焦。所提出的 GRIN-PC 透镜设计通过放大透镜焦点区域的波能,减少了材料阻尼导致的振幅衰减。为聚合物开发的嵌入式透镜概念也可惠及需要在高材料阻尼结构中传输波能的其他应用。
Multifunctional Polyimide Nanofibrous Aerogel Sensor for Motion Monitoring and Airflow Perception
Jun Lin, Jianwei Li, Wen Li, Shuting Chen, Yuyan Lu, Lijun Ma, Xinhai He, Qiangli Zhao
doi:10.1016/j.compositesa.2023.108003
用于运动监测和气流感知的多功能聚酰亚胺纳米纤维气凝胶传感器
Aerogel sensors have garnered significant attention within the realm of recent academic research. However, the challenge of simultaneously maintaining superior mechanical performance and expanding the range of potential applications in varying environmental conditions has yet to be overcome. This study presents a novel approach for fabricating a polyimide nanofibrous aerogel (PINA) using direct electrospinning, which exhibits exceptional mechanical durability and lightweight properties. Subsequently, a flexible wearable sensor was developed through the deposition of pyrrole (Py) on the PINA substrate, with the purpose of monitoring both respiratory health and everyday activities. Furthermore, PINA@PPy possesses the capability to function as a wearable apparatus capable of sound detection. This feature enables the device to gather sound signals and subsequently discern various types of natural acoustic activities. More importantly, the prepared sensor can be used to monitor respiration and diagnose obstructive sleep apnea (OSA), showing high sensitivity to weak airflow at different angles. The PINA@PPy airflow sensor has an ultralow detection limit (0.0027 m/s-1), rapid respiratory response/recovery (0.64/1.18 s), and multi-angle airflow response (0°, 45°, and 90°), providing a convenient and practical method for real-time respiratory monitoring.
气凝胶传感器在最近的学术研究领域获得了极大关注。然而,如何在不同的环境条件下同时保持优异的机械性能和扩大潜在的应用范围,这一难题仍有待攻克。本研究提出了一种利用直接电纺丝技术制造聚酰亚胺纳米纤维气凝胶(PINA)的新方法,这种气凝胶具有优异的机械耐久性和轻质特性。随后,通过在 PINA 基底上沉积吡咯(Py),开发出一种柔性可穿戴传感器,用于监测呼吸健康和日常活动。此外,PINA@PPy 还具有可穿戴设备的功能,能够检测声音。这一功能使该设备能够收集声音信号,并随后辨别各种类型的自然声音活动。更重要的是,准备好的传感器可用于监测呼吸和诊断阻塞性睡眠呼吸暂停(OSA),对不同角度的微弱气流表现出高度敏感性。PINA@PPy 气流传感器具有超低检测限(0.0027 m/s-1)、快速呼吸响应/恢复(0.64/1.18 s)和多角度气流响应(0°、45° 和 90°)等特点,为实时呼吸监测提供了一种方便实用的方法。
A wrapped and infiltrated ∼20-μm-thick 3D ceramic framework composite enables fast Li+ diffusion and interfacial compatibility for lithium-metal batteries
Bixia Wei, Yueqing Li, Wentao Lin, Jing Yu, Dengjie Chen
doi:10.1016/j.compositesb.2024.111192
20-μm 厚的包裹和浸润式三维陶瓷框架复合材料可实现锂+的快速扩散和锂金属电池的界面兼容性
Composite polymer electrolytes (CPEs) have shown potential for energy-dense Li-metal batteries (LMBs), but CPEs have always encountered poor ionic conductivity, low Li+ transference ability, and dendrite propagation. In our work, a mechanically robust three-dimensional porous framework (3DPF) with a thickness of ∼21 μm was successfully prepared by tape-casting and firing Li6.75La3Zr1.75Ta0.25O12 (LLZTO). After wrapping and infiltrating poly(vinylidene fluoride) (PVDF)−salt (LiTFSI)−LLZTO solution to 3DPF (3DPF-PVDF-LLZTO) for subsequent solidification, the resultant composite electrolyte (∼22 μm) shows an excellent room-temperature ionic conductivity of 1.67 × 10−4 S cm−1 and an extremely high Li + transference number of 0.82, indicating fast Li+ diffusion. Furthermore, 3DPF-PVDF-LLZTO exhibits a mechanical strength of 37.5 MPa, and the assembled Li|3DPF-PVDF-LLZTO|Li cell ensures stable operation at 1.0 mA cm−2 and presents prolonged cycling stability at 0.2 mA cm−2 over 800 h without exhibiting dendrites, demonstrating excellent interfacial compatibility. A Li|3DPF-PVDF-LLZTO|LiFePO4 battery delivers excellent room-temperature cycle stability and rate capability, with an initial capacity 160.7 mAh g−1 at 0.2 C and 115.3 mAh g−1 over 450 cycles at 1.0 C. This work provides a practical strategy for constructing highly conductive composite electrolyte with electrode−electrolyte compatibility for LMBs and deepens our understanding of Li+ diffusion pathways.
复合聚合物电解质(CPEs)在高能量锂金属电池(LMBs)中已显示出潜力,但CPEs一直存在离子导电性差、Li+转移能力低和枝晶扩展等问题。在我们的工作中,通过胶带浇铸和烧结 Li6.75La3Zr1.75Ta0.25O12 (LLZTO),成功制备了厚度为 21 μm 的机械强度高的三维多孔框架 (3DPF)。将聚(偏二氟乙烯)(PVDF)-盐(LiTFSI)-LLZTO 溶液包裹并渗透到 3DPF 中(3DPF-PVDF-LLZTO)进行固化后,得到的复合电解质(∼22 μm)显示出卓越的室温离子电导率(1.67 × 10-4 S cm-1)和极高的 Li + 转移数(0.82),表明 Li + 扩散速度极快。此外,3DPF-PVDF-LLZTO 还具有 37.5 MPa 的机械强度,组装后的 Li|3DPF-PVDF-LLZTO|Li 电池可确保在 1.0 mA cm-2 下稳定工作,并在 0.2 mA cm-2 下持续循环 800 小时,且未出现树枝状突起,显示出优异的界面相容性。锂|3DPF-PVDF-LLZTO|LiFePO4电池具有出色的室温循环稳定性和速率能力,在0.2 C时初始容量为160.7 mAh g-1,在1.0 C时循环450次后容量为115.3 mAh g-1。这项工作为构建具有电极-电解质兼容性的高导电性复合电解质提供了一种实用策略,并加深了我们对Li+扩散途径的理解。
Incorporation of hexagonal nitride and multi-walled carbon nanotube for motion sensing triboelectric nanogenerators
Byung Gwan Hyun, Yun-Seok Jun, Jung-Hyub Lee, Mahdi Hamidinejad, Zia Saadatnia, Shahriar Ghaffari-Mosanenzadeh, Hani E. Naguib, Chul B. Park
doi:10.1016/j.compositesb.2024.111193
将六方氮化物和多壁碳纳米管纳入运动传感三电纳米发电机
In this study, the thermoplastic polyurethane (TPU) composite that incorporates hexagonal nitride (h-BN) and multi-walled carbon nanotube (MWCNT) is fabricated and employed as an electrification layer for triboelectric nanogenerators (TENG). Owing to the high elasticity of TPU, the TPU/h-BN/MWCNT composite shows high stretching ability with low Young's modulus of 2∼3 MPa, similar to that of soft tissues. The addition of h-BN efficiently helps construct the conductive network of MWCNT, and the combination of h-BN and MWCNT significantly boosts the dielectric constant of the composite. The mixture of 6 vol% of h-BN and 1.05 vol% of MWCNT exhibits an excellent combination of a real permittivity of 232 and a loss tangent of 2.4, generating the output voltage and current of 47V and 244 nA, respectively. In addition, the increase of resistance is not considerable up to 60 % tensile strain when 1.05 vol% of MWCNT exists in the TPU, and the TPU/h-BN/MWCNT composite presented a stable TENG performances under 60 % strain. Moreover, the TENG made from the TPU/h-BN/MWCNT composite successfully senses a range of complicated hand gestures by producing very distinct output voltages. Thus, it presents promising possibility as a wearable, skin mountable, and self-powered motion sensor.
本研究制备了含有六方氮化物(h-BN)和多壁碳纳米管(MWCNT)的热塑性聚氨酯(TPU)复合材料,并将其用作三电纳米发电机(TENG)的电气化层。由于热塑性聚氨酯的高弹性,热塑性聚氨酯/h-BN/MWCNT 复合材料显示出较高的拉伸能力,杨氏模量低至 2∼3 兆帕,与软组织类似。h-BN 的加入有效地帮助构建了 MWCNT 的导电网络,h-BN 和 MWCNT 的结合显著提高了复合材料的介电常数。6 Vol% 的 h-BN 和 1.05 Vol% 的 MWCNT 的混合物表现出了出色的组合,实际介电常数为 232,损耗正切为 2.4,输出电压和电流分别为 47V 和 244 nA。此外,当热塑性聚氨酯中含有 1.05 Vol% 的 MWCNT 时,在 60% 的拉伸应变下电阻的增加并不显著,热塑性聚氨酯/h-BN/MWCNT 复合材料在 60% 的应变下具有稳定的 TENG 性能。此外,由热塑性聚氨酯/h-BN/MWCNT 复合材料制成的 TENG 能产生非常明显的输出电压,从而成功感知一系列复杂的手势。因此,它有望成为一种可穿戴、可安装在皮肤上、自供电的运动传感器。
Multiaxial failure behavior and fatigue life prediction of unidirectional composite laminates
Yuhao Lian, Fuqiang Wu, Qijun Zhao, Yalin Han, Bin Wang
doi:10.1016/j.compscitech.2023.110430
单向复合材料层压板的多轴失效行为和疲劳寿命预测
Complex coupling mechanisms exist between longitudinal and shear stress on the multiaxial fatigue behavior of composites. A thorough reanalysis of matrix shear failure mechanism under multiaxial fatigue loading is presented. Longitudinal single splitting fracture were analyzed and validated as an independent failure mode under multiaxial loading by analogy to the failure mechanism of natural composites. A new multiaxial fatigue life prediction model was established by double projection on the critical and subcritical fracture planes. Experiments on unidirectional tubular specimens were carried out under combined tension-torsion loadings to separate and identify the multiaxial fatigue failure behavior of composites. The proposed model has been verified using unidirectional laminates subjected to cyclic tension-torsion and off-axis loading, and the results showed that the predicted life is in good agreement with the experimental ones. Applications of three-dimensional digital image correlation (3D-DIC) and microscopy regarding verification in multiaxial damage mechanism are also addressed.
在复合材料的多轴疲劳行为中,纵向应力和剪切应力之间存在着复杂的耦合机制。本文对多轴疲劳加载下的基体剪切破坏机理进行了全面的重新分析。通过类比天然复合材料的失效机理,分析并验证了纵向单劈裂断裂是多轴载荷下的一种独立失效模式。通过临界和次临界断裂面的双重投影,建立了新的多轴疲劳寿命预测模型。在拉伸-扭转联合载荷下对单向管状试样进行了实验,以分离和识别复合材料的多轴疲劳破坏行为。使用单向层压板在周期性拉伸-扭转和离轴载荷下对所提出的模型进行了验证,结果表明预测寿命与实验寿命十分吻合。此外,还讨论了三维数字图像相关(3D-DIC)和显微镜在多轴损伤机制验证方面的应用。