今日更新:Composite Structures 3 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 1 篇
Influence of compaction and curing in the Automated Fiber Placement Process on the mechanical performance of composite laminates
Sylvester Vogl, Ralf Knott, Silvano Sommacal, Paul Compston, Klaus Drechsler
doi:10.1016/j.compstruct.2023.117826
自动纤维铺放工艺中的压实和固化对复合材料层压板机械性能的影响
This paper investigates the effect of compaction and curing states on the mechanical properties and void content of AFP-manufactured laminates. For the mechanical characterization, tensile tests, 4-point-bending tests and interlaminar shear strength (ILSS) tests were applied. The internal structure was evaluated via micro CT. For the surface structure evaluation, an optical profilometer was used. The void content was determined via segmentation of the micro CT images. The paper is subdivided into the description of the applied materials and methods, the results and their discussion and a conclusion. The study showcases the potential of AFP-manufactured aerospace composites to attain high-quality results even without the need for an autoclave, making them well-suited for unmanned applications.
本文研究了压实和固化状态对 AFP 制造的层压板的机械性能和空隙率的影响。在机械性能表征方面,采用了拉伸试验、4 点弯曲试验和层间剪切强度(ILSS)试验。内部结构通过微型 CT 进行评估。表面结构评估则使用了光学轮廓仪。通过对微型 CT 图像进行分割,确定了空隙含量。本文分为应用材料和方法描述、结果及其讨论和结论。该研究展示了 AFP 制造的航空航天复合材料的潜力,即使无需高压灭菌也能获得高质量的结果,使其非常适合无人驾驶应用。
Enhanced prediction of transverse mechanical behavior of unidirectional fiber-reinforced composites using new spatial descriptors based on deep neural networks
Sun Won Kim, Jae Hyuk Lim, Seong Su Kim
doi:10.1016/j.compstruct.2023.117870
利用基于深度神经网络的新空间描述符增强单向纤维增强复合材料横向力学行为的预测能力
In this study, we developed a data-driven approach using a deep neural network (DNN) to predict the nonlinear stress-strain behavior of fiber-reinforced composites under transverse tensile loading. We explored the impact of different input features characterizing the composite microstructure on the prediction accuracy of the DNN model. Specifically, we introduced a spatial descriptor representing fiber arrangement and proposed new spatial descriptors based on fiber area to improve input feature quality. Incorporating widely-used spatial descriptors such as the second-order intensity function and radial distribution function improved the prediction performance compared to previous methods. Combining spatial descriptors for both fiber distribution and alignment further enhanced prediction accuracy. To address the limitations of conventional spatial descriptors, we developed new spatial descriptors using a continuous function. Our findings demonstrate the importance of selecting appropriate input features for improved DNN model performance, even with the same dataset. Moreover, the proposed fiber area-based spatial descriptors offer insights into the micromechanical behavior of composite materials.
在这项研究中,我们利用深度神经网络(DNN)开发了一种数据驱动方法,用于预测横向拉伸载荷下纤维增强复合材料的非线性应力应变行为。我们探索了表征复合材料微观结构的不同输入特征对 DNN 模型预测精度的影响。具体来说,我们引入了代表纤维排列的空间描述符,并提出了基于纤维面积的新空间描述符,以提高输入特征的质量。与之前的方法相比,结合二阶强度函数和径向分布函数等广泛使用的空间描述符提高了预测性能。结合纤维分布和排列的空间描述符进一步提高了预测精度。为了解决传统空间描述符的局限性,我们使用连续函数开发了新的空间描述符。我们的研究结果表明,即使使用相同的数据集,选择适当的输入特征对于提高 DNN 模型性能也非常重要。此外,所提出的基于纤维面积的空间描述符为复合材料的微观机械行为提供了见解。
Mechanical vibration absorber for flexural wave attenuation in multi-materials metastructure
Long Liu, Ji Wan Kim, Gil Ho Yoon, Bing Yi
doi:10.1016/j.compstruct.2023.117859
用于衰减多材料结构中挠曲波的机械减震器
Vibration isolation is a promise to suppress mechanical vibration from a host structure, similarly, a mechanical vibration absorber, a simple but effective device to attenuate flexural wave propagation, which has been implemented in civil and mechanical engineering. This paper presents a type of composite sandwich phononic crystal to attenuate the flexural wave propagation in a beam structure, which can effectively suppress mechanical vibration in a broad band gap by repetitively arranging phononic crystal. First, the elastic wave dispersion characteristic in a composite sandwich beam structure is derived, and a triangular shape phononic crystal for flexural wave attenuation by taking advantage of destructive interference is presented. Then two dimensional phononic crystals are designed by assembling four different unit-cells of metabeam. Finally, numerical experiments are conducted to verify the effectiveness of the proposed mechanical metamaterial absorbers to attenuate flexural wave propagation, the numerical results indicate that the proposed metamaterial is of good performance in mechanical vibration suppression, which can effectively mitigate structure vibration in low-frequency domain than the structure without phononic crystal and single layer metamaterial beam structure. It is the first attempt to design a mechanical metamaterial absorber with the mechanism of destructive interference with composite sandwich phononic crystal.
隔振是一种抑制来自主机结构的机械振动的承诺,同样,机械吸振器也是一种简单而有效的衰减挠性波传播的装置,在土木工程和机械工程中已经得到了应用。本文提出了一种用于衰减梁结构中挠曲波传播的复合夹层声子晶体,通过重复排列声子晶体,可有效抑制宽带隙中的机械振动。首先,推导了复合夹层梁结构中的弹性波色散特性,并提出了一种利用破坏性干涉来衰减挠曲波的三角形声子晶体。然后,通过组装四个不同的元梁单元,设计了二维声子晶体。最后,通过数值实验验证了所提出的机械超材料吸波材料对挠性波传播的衰减效果,数值实验结果表明,所提出的超材料在机械振动抑制方面具有良好的性能,与不含声子晶体的结构和单层超材料梁结构相比,能有效缓解结构在低频域的振动。这是首次尝试利用复合夹层声子晶体的破坏性干涉机制设计机械超材料吸波材料。
Spatial variability characterization and modelling of 2.5D woven SiO2f/SiO2 composites
Hongyue Wang, Bing Wang, Maoqing Fu, Guodong Fang, Songhe Meng
doi:10.1016/j.compositesa.2023.107997
2.5D SiO2f/SiO2 编织复合材料的空间变化特征和建模
2.5D woven SiO2f/SiO2 composites possess geometric variabilities across scales, such as the spatial fluctuations of fibers and yarns or the random distributions of defects and pores formed in the manufacturing process, which induces a complex stress and strain distribution in material testing. In this study, a multivariate cross-correlated non-Gaussian random field based on Vine Copula is proposed to characterize the spatial variability of mechanical properties. A database of material mechanical properties is acquired by stochastic representative volume element (SRVE) simulation results which contains realistic meso-geometry characteristics and spatially random voids. Based on this database, the cross- and auto-correlations of the mechanical properties are quantified by Vine Copula and non-Gaussian random field model. In a comparison of different numerical models and experimental results, the proposed method is verified, which shows great advantages in characterizing the spatial variability and big potential abilities in damage or reliability analysis.
2.5D SiO2f/SiO2 编织复合材料具有跨尺度的几何变异性,如纤维和纱线的空间波动或制造过程中形成的缺陷和孔隙的随机分布,从而在材料测试中引起复杂的应力和应变分布。本研究提出了一种基于 Vine Copula 的多元交叉相关非高斯随机场,用于描述力学性能的空间变异性。材料力学性能数据库由随机代表体积元素(SRVE)模拟结果获得,其中包含真实的中间几何特征和空间随机空隙。在该数据库的基础上,采用 Vine Copula 和非高斯随机场模型对力学性能的交叉和自相关性进行了量化。通过比较不同的数值模型和实验结果,验证了所提出的方法在表征空间变异性方面的巨大优势,以及在损伤或可靠性分析方面的巨大潜力。
Functionalizing chitosan-based film with highly sensitive fire response and commendable flame retardancy for intelligent fire-alarm system
Rongkai Wu, Yu Wang, Yunyirui Liu, Bihe Yuan
doi:10.1016/j.compositesa.2023.107999
将壳聚糖基薄膜功能化,使其具有高度灵敏的火灾反应和值得称赞的阻燃性能,用于智能火灾报警系统
Recently, the extensive use of combustible materials has amplified building fire damage, making it essential to incorporate fire-detection devices and flame-retardant materials in building. Herein, the chitosan/gelatin (CG) film and KH2PO4-modified CG (KCG) films were fabricated via an eco-friendly water evaporation method. Impressively, KCG films demonstrate swift response times: 0.5 s at 100 ℃ and 1.8 s under flame, facilitating prompt alarms during fire incidents. Compared to CG, KCG achieve a 70.4% and 46.2% reduction in peak heat release rate and total heat release respectively. They also offer flexibility, transparency, repeated fire-warning efficacy and superior char formation. With these properties, KCG hold promise for innovative building fire safety solutions like smart fire-alarm wallpaper. Besides, a tailored wireless-based fire-alarm system for KCG further decreases building fire damage. This work mitigates damages arising from building fires work, marking significant leap forward in the use of bio-based materials for fire prevention in architecture.
近年来,可燃材料的广泛使用加剧了建筑物的火灾损失,因此在建筑物中加入火灾探测装置和阻燃材料至关重要。本文采用环保的水蒸发法制作了壳聚糖/明胶(CG)薄膜和 KH2PO4 改性 CG(KCG)薄膜。令人印象深刻的是,KCG 薄膜的响应时间很快:在 100 ℃ 下为 0.5 秒,在火焰下为 1.8 秒,有助于在火灾事故中迅速报警。与 CG 相比,KCG 的峰值放热率和总放热率分别降低了 70.4% 和 46.2%。此外,KCG 还具有柔韧性、透明性、多次火灾预警效果和优异的炭化性能。凭借这些特性,KCG有望成为智能火警墙纸等创新型建筑消防安全解决方案的首选。此外,为 KCG 量身定制的基于无线的火灾报警系统还能进一步降低建筑火灾损失。这项工作减轻了建筑火灾造成的损失,标志着生物基材料在建筑防火领域的应用取得了重大飞跃。
The synergistic effect of greenhouse gas CO2 and silica fume on the properties of 3D printed mortar
Hao Lucen, Li Long, Zhang Shipeng, Zhang Huanghua, Xiao Jianzhuang, Poon Chi Sun
doi:10.1016/j.compositesb.2023.111188
温室气体二氧化碳和硅灰对 3D 打印砂浆性能的协同效应
To fulfil the requirements of pumpability and buildability, the rheological properties of mortar/concrete for 3D printing should follow much stricter requirements than traditional-cast mortar/concrete. This study proposed to use a secondary CO2 mixing technique coupled with the addition of silica fume (SF) to achieve in-situ rheology control of 3D printed mortar. The influences of CO2 mixing on the properties of the cast mortar and the 3D printed mortar prepared with SF were systematically studied. The pH, conductivity and ion concentration were tested to revel the essential chemical reactions and phase evolutions during CO2 mixing. It was found that the CO2 mixing effectively enhanced the early-age penetration resistance and yield stress of mortar incorporated with SF, and thus significantly improved the buildability of 3D printed mortar, while the maximum printing layer increased higher than 33 layers. Meanwhile, the mechanical properties of the SF-incorporated mortar were improved by this process. It was revealed that during the CO2 mixing process, the injected CO2 rapidly reacted with calcium ions to form CaCO3, which further reacted with C3A to form monocarboaluminate (Mc). The fast precipitation of calcium ions during CO2 mixing accelerated the hydration of C3A and C3S, contributing to the rapid development of strength at early ages and the improved performance of hardened mortar. The addition of SF in mortar greatly amplified the beneficial effect of CO2 mixing, which due to SF as nucleation sites promoted the formation of CaCO3 and Mc during CO2 mixing.
为了满足可泵性和可施工性的要求,3D 打印砂浆/混凝土的流变特性应遵循比传统浇注砂浆/混凝土更严格的要求。本研究建议采用二次二氧化碳混合技术,并添加硅灰(SF),以实现对 3D 打印砂浆的原位流变控制。该研究系统地研究了二氧化碳混合对浇注砂浆和用 SF 制备的 3D 打印砂浆性能的影响。测试了 pH 值、电导率和离子浓度,以揭示二氧化碳混合过程中的基本化学反应和相变。研究发现,CO2 混合能有效提高掺入 SF 的砂浆的早龄期抗渗透性和屈服应力,从而显著改善 3D 打印砂浆的可施工性,最大打印层数比 33 层更高。同时,该工艺还改善了掺入 SF 的砂浆的力学性能。研究发现,在二氧化碳混合过程中,注入的二氧化碳迅速与钙离子反应生成 CaCO3,再与 C3A 反应生成单碳铝酸盐(Mc)。CO2 混合过程中钙离子的快速析出加速了 C3A 和 C3S 的水化,有助于早期龄期强度的快速发展和硬化砂浆性能的改善。在砂浆中加入 SF 大大提高了 CO2 混合的有益效果,因为 SF 是成核场所,在 CO2 混合过程中促进了 CaCO3 和 Mc 的形成。
A self-powered piezoelectric Poly(vinyl alcohol)/Polyvinylidene fluoride fiber membrane with alternating multilayer porous structure for energy harvesting and wearable sensors
Yaru Yu, Xiaowen Zhao, Huaiguo Ge, Lin Ye
doi:10.1016/j.compscitech.2023.110429
具有交替多层多孔结构的自供电压电聚(乙烯醇)/聚偏氟乙烯纤维膜,用于能量采集和可穿戴传感器
Development of flexible wearable electronic devices requires high-performance piezoelectric sensors, being advantageous in high sensitivity, ease to microintegration without external power supply. In this work, poly(vinyl alcohol) (PVA)/polyvinylidene fluoride (PVDF) fiber membranes with stable alternating multilayer structure were constructed through electrospinning and subsequent gas-phase crosslinking. The PVA/PVDF fiber was fully stretched with smooth surface and uniform diameter at appropriate PVDF concentration, exhibiting high porosity (88 %). The α-phase was transformed into the electroactive β-phase of PVDF in the electrospinning process, while the crystallinity and β-phase percentage (Fβ) were improved by mixing spinning of PVA and PVDF, with Fβ reaching above 90 %. The PVA/PVDF fiber membrane showed high mechanical strength/toughness and liquid absorbency (719.03 %). The significant electrical signal output (10.07 V and 166.42 nA) was generated, accompanying with high stress sensitivity, short response time and high stability, exhibiting excellent piezoelectricity and making the fiber membrane not only monitor large deformation movements of limbs as self-powered wearable sensor, but also sense weak signals of pulse, breathing etc. for monitoring human health, as well as environmental humidity. Meanwhile, the harvested energy could drive electronic device, showing prosperous potentials in fields of artificial intelligence.
柔性可穿戴电子设备的开发需要高性能的压电传感器,这些传感器具有灵敏度高、易于微集成且无需外部电源等优点。在这项工作中,通过电纺丝和随后的气相交联,构建了具有稳定交替多层结构的聚乙烯醇(PVA)/聚偏氟乙烯(PVDF)纤维膜。在适当的 PVDF 浓度下,PVA/PVDF 纤维完全拉伸,表面光滑,直径均匀,孔隙率高(88%)。在电纺丝过程中,PVDF 的 α 相转变为具有电活性的 β 相,而通过 PVA 和 PVDF 的混合纺丝,结晶度和 β 相百分比(Fβ)得到了改善,Fβ 达到了 90% 以上。PVA/PVDF 纤维膜具有较高的机械强度/韧性和吸液率(719.03%)。产生的电信号输出(10.07 V 和 166.42 nA)具有应力灵敏度高、响应时间短和稳定性高等特点,表现出优异的压电性,使纤维膜不仅能监测肢体的大变形运动,成为自供电的可穿戴传感器,还能感知脉搏、呼吸等微弱信号,用于监测人体健康和环境湿度。同时,采集到的能量可以驱动电子设备,在人工智能领域大有可为。