今日更新:Composite Structures 1 篇,Composites Part B: Engineering 2 篇,Composites Science and Technology 1 篇
Efficient zigzag theory-based spectral element model for guided waves in composite structures containing delaminations
Jain Mayank, Kapuria Santosh
doi:10.1016/j.compstruct.2023.117585
基于 "之 "字形理论的高效频谱元素模型:含分层复合结构中的导波
Lamb wave-based structural health monitoring offers excellent potential for real-time delamination detection in laminated structures. It necessitates fast and accurate numerical simulation of guided wave interaction with delaminations. Towards this objective, we present an efficient layerwise zigzag theory (ZIGT) based time-domain spectral element for wave propagation analysis of composite beam- and panel- type structures (strips) containing delamination at arbitrary locations. The ZIGT delivers accuracy like layerwise theories by allowing slope discontinuities in the in-plane displacement field at layer interfaces while maintaining computational efficiency like equivalent single-layer (ESL) theories, making it ideal for such analyses. The high-order elemental nodes at Lobatto points have only four displacement variables, irrespective of the number of layers in the laminate. Delamination is modelled using the region approach, adapting the recently proposed hybrid point-least squares continuity method to satisfy the nonlinear displacement field continuity at the delamination fronts. The model’s efficacy is examined vis-à-vis elasticity-based elements, ESL theory-based elements, and the ZIGT-based standard finite element for free vibration and guided wave propagation responses of composite strips featuring multiple delaminations. The present model shows superior overall efficiency, accuracy, and convergence. An application of the model is also explored for identifying delamination locations from Lamb wave velocity fields.
基于 Lamb 波的结构健康监测为层状结构的实时分层检测提供了巨大的潜力。这就需要对导波与分层的相互作用进行快速、准确的数值模拟。为了实现这一目标,我们提出了一种基于高效分层之字形理论(ZIGT)的时域频谱元素,用于分析任意位置含有分层的复合梁式和板式结构(带)的波传播。ZIGT 允许层界面处平面内位移场出现斜率不连续,从而提供了与分层理论相同的精度,同时保持了与等效单层(ESL)理论相同的计算效率,使其成为此类分析的理想选择。洛巴托点的高阶元素节点只有四个位移变量,与层压板的层数无关。分层采用区域法建模,调整了最近提出的混合点最小二乘法连续性方法,以满足分层前沿的非线性位移场连续性。与基于弹性的元素、基于 ESL 理论的元素和基于 ZIGT 的标准有限元相比,该模型在具有多重分层的复合材料带材的自由振动和导波传播响应方面的功效得到了检验。本模型在整体效率、精确度和收敛性方面均表现出众。此外,还探讨了该模型在从 Lamb 波速度场识别分层位置方面的应用。
Experimental and numerical fatigue damage characterization in multidirectional thermoplastic glass/polypropylene laminates based on in-situ damage observations
Sommer J., Hajikazemi M., De Baere I., Van Paepegem W.
doi:10.1016/j.compositesb.2023.111028
基于原位损伤观测的多向热塑性玻璃/聚丙烯层压板疲劳损伤特征的实验和数值分析
Quantifying microscopic damage mechanisms in opaque composite laminates with multiple off-axis plies throughout fatigue experiments is challenging. However, if successful, important relations can be revealed between actual evolving damages and their contribution to the mechanical laminate response. This study characterizes the evolution of matrix cracking in ±45 and 90 embedded off-axis plies together with effects of delamination and relates them to the global mechanical property reductions in Glass/Polypropylene laminates. [0/45/0/-45]s and [0/45/90/-45]s laminates are tested under tension-tension fatigue over 500 000 cycles at three different stress levels. In-situ edge damage detection by optical measurements are performed as well as the validation of damages by detailed post-mortem microscopy. Moreover, through-the-width sectioning is applied to reveal the damages inside the laminate after testing. Additionally, the effects of different fabrication histories on damage progression are assessed. Influences of 45-ply thickness and different ply neighbouring orientations on the damage behaviour are discussed with their contribution to the normalized stiffness degradation and Poisson's ratio evolution. Moreover, experimental results are compared with a modelling approach by which the effects of damages in multiple plies can be considered, showing very good accordance.
在整个疲劳实验过程中,对具有多个离轴层的不透明复合材料层压板的微观损伤机制进行量化具有挑战性。不过,如果成功的话,就能揭示实际损伤演变与其对层压板机械响应的贡献之间的重要关系。本研究描述了 ±45 和 90 嵌入偏轴层中基体开裂的演变以及分层的影响,并将其与玻璃/聚丙烯层压板的整体机械性能降低联系起来。对[0/45/0/-45]s和[0/45/90/-45]s层压板在三种不同应力水平下进行了500 000次拉伸疲劳测试。通过光学测量进行了原位边缘损伤检测,并通过详细的死后显微镜对损伤进行了验证。此外,在测试结束后,还采用了通宽切片技术来揭示层压板内部的损伤情况。此外,还评估了不同制造历史对损伤发展的影响。讨论了 45 层厚度和不同层相邻方向对损伤行为的影响,以及它们对归一化刚度退化和泊松比演变的贡献。此外,实验结果还与一种建模方法进行了比较,通过这种方法可以考虑多层中的损伤影响,结果显示两者非常吻合。
A review of advancements in synthesis, manufacturing and properties of environment friendly biobased Polyfurfuryl Alcohol Resin and its Composites
Odiyi D.C., Sharif T., Choudhry R.S., Mallik Sabuj, Shah S.Z.H.
doi:10.1016/j.compositesb.2023.111034
环境友好型生物基聚糠醇树脂及其复合材料的合成、制造和性能进展综述
The quest for environmentally friendly and sustainable materials in the production of fibre reinforced composite materials has led to the use of biobased materials, which are easily accessible and renewable. Biomass-derived chemicals, their derivatives, and their applications have become increasingly prevalent in various industries and processes, greatly contributing to the goal of ecological sustainability. The biobased Polyfurfuryl Alcohol (PFA) resin is one of such polymeric materials that is gaining attention for composite applications due to its endearing Fire Smoke and Toxicity properties. Derived from agricultural by products such as sugar cane bagasse, it has been known for applications within the foundry, coating, and wood industries. However, there has been a growing interest in its use for fibre reinforced composite applications. For this reason, this work intends to provide a comprehensive review of the PFA resin in relationship to fibre reinforced composites applications. The work provides an in-depth discussion on the synthesis, curing process, manufacturing, and properties of the PFA resin as well as its composites.
在纤维增强复合材料的生产过程中,对环保和可持续材料的追求促使人们开始使用生物基材料,因为生物基材料易于获取且可再生。生物质衍生化学品、其衍生物及其应用在各种工业和工艺中日益普及,极大地促进了生态可持续发展目标的实现。生物基聚糠醇(PFA)树脂就是这样一种高分子材料,由于其耐火烟和毒性的特性,它在复合材料应用领域越来越受到关注。PFA 源自甘蔗渣等农副产品,在铸造、涂料和木材行业的应用已广为人知。然而,人们对其在纤维增强复合材料中的应用越来越感兴趣。因此,本研究旨在全面审查 PFA 树脂与纤维增强复合材料应用的关系。作品深入探讨了 PFA 树脂及其复合材料的合成、固化过程、制造和特性。
Supramolecular cross-linking affords chitin nanofibril nanocomposites with high strength and water resistance
Jiao Dejin, Li Zhengqun, Hu Jia Yu, Zhang Xin Ning, Guo Jiaqi, Zheng Qiang, Wu Zi Liang
doi:10.1016/j.compscitech.2023.110295
超分子交联产生具有高强度和耐水性的甲壳素纳米纤维纳米复合材料
Polysaccharide nanofibrils of chitins or celluloses are emerging biobased building blocks for sustainable, high-performance bioinspired nanocomposites fusing high stiffness, strength, and other functionalities. Owing to their hygroscopicity, a crucial challenge towards real-life applications of these nanocomposites is to maintain their mechanical performances in the humid or even fully swollen conditions. Here, we report water resistant nanocomposites composed of sustainable chitin nanofibrils (ChNFs) and polyvinyl alcohol (PVA) that are physically cross-linked by tannic acid (TA) to afford enhancement and stabilization of the wet mechanical properties. We demonstrate that the formation of polymer-coated core/shell nanofibrils at the intermediate stage is crucial for the well-defined nanopaper structures after casting. By infiltrating TA, the formation of hydrogen bonding in the PVA matrix and at the ChNF/PVA interface renders the nanocomposites with extremely high strength and stiffness, even under high humidity and swelling conditions. With the increase in the amount of conjugated TA, the Young's modulus and tensile strength of the swollen nanocomposites reach up to 3.0 GPa and 70 MPa, respectively, which are superior to the existing water-borne nanofibils/polymer nanocomposites. Moreover, the nanocomposite films show excellent gas barrier properties at high relative humidity (90%), as well as UV shielding, antibacterial properties and biodegradability, complementing the multifunctional property profile and allowing a transfer into applications as advanced packaging materials.
甲壳素或纤维素多糖纳米纤维是一种新兴的生物基构件,可用于制造可持续的高性能生物启发纳米复合材料,这种复合材料融合了高硬度、高强度和其他功能。由于其吸湿性,这些纳米复合材料在实际应用中面临的一个重要挑战是如何在潮湿甚至完全膨胀的条件下保持其机械性能。在这里,我们报告了由可持续甲壳素纳米纤维(ChNFs)和聚乙烯醇(PVA)组成的耐水纳米复合材料,它们通过单宁酸(TA)的物理交联来增强和稳定湿机械性能。我们证明,在中间阶段形成聚合物包覆的核/壳纳米纤维对于浇铸后形成清晰的纳米纸结构至关重要。通过渗入 TA,在 PVA 基体和 ChNF/PVA 界面形成氢键,使纳米复合材料具有极高的强度和刚度,即使在高湿度和膨胀条件下也是如此。随着共轭 TA 含量的增加,膨胀纳米复合材料的杨氏模量和拉伸强度分别高达 3.0 GPa 和 70 MPa,优于现有的水性纳米纤维/聚合物纳米复合材料。此外,纳米复合薄膜在高相对湿度(90%)条件下表现出优异的气体阻隔性能、紫外线屏蔽性能、抗菌性能和生物可降解性,补充了多功能性能特征,可用作先进的包装材料。