今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 1 篇
Free vibration of cracked FGM Mindlin plate in fluid
Hui-Cui Li, Jia-Jia Mao, Heng Hu, Liao-Liang Ke
doi:10.1016/j.compstruct.2024.118013
流体中开裂 FGM Mindlin 板的自由振动
The free vibration of cracked functionally graded material (FGM) plate in fluid is investigated in this paper. The material components are supposed following the power law and formulated by the Voigt model. The Mindlin plate theory (MPT) including the shear deformation effect is established and the physical neutral plane is adopted to simplify the derivation due to the in-plane displacements of this plane assumed as zero. A massless linear rotational spring model (LRSM) is established to simulate the through-width surface crack. The hydrodynamic pressure at the fluid-plate interface is derived by the potential flow theory, and is regarded as the added mass of cracked FGM plate during the analyses of fluid-plate coupled vibration. The derivation and discretization of vibrational equations for cracked FGM plates in fluid are respectively achieved though the Hamilton’s principle and differential quadrature (DQ) method. The frequencies and mode shapes are iteratively calculated with these values of the vacuum case. The influences of immersed depth, fluid density, gradient index, crack depth, crack location, length-to-width ratio, length-to-thickness ratio, and boundaries on vibration characteristics are conducted in the section of numerical results. The present vibration analyses of cracked structures can be applicable to avoid structural resonance and failure.
本文研究了流体中开裂的功能分级材料(FGM)板的自由振动。材料成分假定遵循幂律,并通过 Voigt 模型进行计算。建立了包含剪切变形效应的明德林板理论(MPT),并采用了物理中性面来简化推导,因为该平面的面内位移假定为零。建立了无质量线性旋转弹簧模型(LRSM)来模拟通宽表面裂缝。流体-板材界面上的流体动力压力由势能流理论推导得出,在流体-板材耦合振动分析中被视为裂纹 FGM 板材的附加质量。流体中裂纹 FGM 板振动方程的推导和离散化分别通过汉密尔顿原理和微分正交(DQ)方法实现。利用真空情况下的这些值迭代计算频率和模态振型。在数值结果部分,研究了浸入深度、流体密度、梯度指数、裂纹深度、裂纹位置、长宽比、长厚比和边界对振动特性的影响。本裂纹结构振动分析可用于避免结构共振和失效。
Development of a novel flax soy-based polyurethane prepreg composite
A. Belzile, F. Armanasco, L.M. Chiacchiarelli, G. Lebrun, E. Ruiz
doi:10.1016/j.compositesa.2024.108136
开发新型亚麻大豆基聚氨酯预浸料复合材料
High performance composite materials are mostly synthesized from non-renewable resources with a detrimental environmental impact. In this work an innovative flax fiber-reinforced soy-based polyurethane composite prepreg was developed from a soy-based polyol crosslinked with glycerin and isocyanate. The flax reinforcement was manufactured by binding unidirectional flax strings with short flax fibers. Composite prepregs were fabricated using a three rolls mill and oven pre-curing to obtain a beta stage. Vacuum assisted molding was used to manufacture laminates with a fiber volume fraction up to 41 %. Electron beam and optical microscope images of the composite cross-section indicated an adequate microstructure. Tensile strength (209 MPa), flexural strength (231 MPa), and short beam shear strength (25 MPa) demonstrated that the composites had good specific mechanical properties comparable with composites containing glass fibers studied in previous works, while having a significantly lower expected environmental impact. These properties demonstrate the appropriateness of the eco-responsible composite material.
高性能复合材料大多由不可再生资源合成,对环境造成不利影响。在这项工作中,利用大豆基多元醇与甘油和异氰酸酯交联,开发出了一种创新的亚麻纤维增强大豆基聚氨酯复合预浸料。亚麻增强材料是通过将单向亚麻绳与短亚麻纤维结合在一起制成的。复合预浸料是用三辊轧机和烘箱预固化法制造的,以获得β阶段。使用真空辅助成型技术制造纤维体积分数高达 41% 的层压板。复合材料横截面的电子束和光学显微镜图像显示了适当的微观结构。拉伸强度(209 兆帕)、抗弯强度(231 兆帕)和短束剪切强度(25 兆帕)表明,复合材料具有良好的特定机械性能,可与之前研究的含玻璃纤维的复合材料相媲美,同时对环境的预期影响明显降低。这些特性证明了生态责任复合材料的适当性。
Highly effective CNT-based magnetic pn-junction nanocomposite photocatalyst/solar-energy material for hazmat conversion to hydrogen fuel
Majid Ghanimati, Mohsen Lashgari, Ander Diego-Lopez, Francisco Bosca, M. Luisa Marin
doi:10.1016/j.compositesb.2024.111367
用于将危险品转化为氢燃料的高效 CNT 磁性 pn 结纳米复合光催化剂/太阳能材料
Hazmat conversion to hydrogen using low-cost effective eco-friendly solar energy active materials is a sustainable strategy for environmental remediation and provision of future green fuel. In this paper, a novel magnetic pn-junction nanocomposite was rationally designed and synthesized through a facile hydrothermal route using affordable chemicals in the absence and presence of CNT (carbon nanotube). The easy recyclable/re-collectable CNT-based magnetic materials with the scaling up capability synthesized here were applied as effective nanoenergy materials for photocatalytic conversion of H2S feed to hydrogen fuel. The maximum hydrogen production was attained for the pn-junction nanocomposite photocatalyst at the molar ratio 1:2 of p to n (rate :5652 μmol H2 g.h) and boosted 60% by adding CNT. Transient photocurrent, impedance, fluorescence and electron paramagnetic resonance (EPR) investigations revealed that the charge recombination is reduced in the presence of CNT and hence the photogenerated e−/h+ pairs can more effectively be utilized in the hazmat-to-fuel conversion process. The junction formation was approved at an atomistic scale through HRTEM observation. Furthermore, the magnetic property of the synthesized nanocomposite photocatalyst was improved in the presence of CNT and discussed in detail from physicochemical standpoint using VSM (vibrating sample magnetometric) and XPS (X-ray photoelectron spectroscopic) evidence.
利用低成本、高效率的生态友好型太阳能活性材料将有害物质转化为氢气,是一种可持续的环境修复战略,也是未来的绿色燃料。本文合理设计了一种新型磁性 pn 结纳米复合材料,并在无 CNT(碳纳米管)和有 CNT(碳纳米管)存在的情况下,利用经济实惠的化学品,通过简便的水热法合成了这种材料。所合成的基于 CNT 的磁性材料易于循环/回收,并具有放大能力,可作为有效的纳米能源材料用于 H2S 进料到氢燃料的光催化转化。当 pn 与 n 的摩尔比为 1:2 时,pn 结纳米复合光催化剂的产氢量达到最大(速率:5652 μmol H2 g.h),加入 CNT 后,产氢量提高了 60%。瞬态光电流、阻抗、荧光和电子顺磁共振(EPR)研究表明,CNT 的存在减少了电荷重组,因此光生成的 e-/h+ 对可以在有害物质转化为燃料的过程中得到更有效的利用。通过 HRTEM 观察,在原子尺度上证实了结的形成。此外,合成的纳米复合光催化剂的磁性能在 CNT 的存在下得到了改善,并利用 VSM(振动样品磁力计)和 XPS(X 射线光电子能谱)证据从物理化学的角度进行了详细讨论。
Global sensitivity analysis for degraded braided composite with interval process
Dongyang Sun, Xuefeng Liang, Huiming Ning, Ning Hu
doi:10.1016/j.compscitech.2024.110542
带间隔过程的降解编织复合材料的全局敏感性分析
Global sensitivity analysis has predominantly focused on examining the effect of time-invariant parameters on the mechanical properties of fiber-reinforced composites, while ignoring degradation. However, fiber-reinforced composites are subject to degradation, which means that the physical system is dynamic. It is important to consider this dynamic behavior in sensitivity analysis. This paper presents a set of sensitivity indices based on the interval method to measure the influence of the time-invariant and time-variant parameters on the synthetic uncertainty of output in global sensitivity analysis for 2D triaxially braided composites (2DTBCs) considering degradation. To achieve this purpose, we represent time-variant uncertain parameter using an interval process and describe them with multiple uncorrelated interval variables using the interval Karhunen-Loève explansion method. We then introduce a two-dimensional interval process and similarity degree to define a new sensitivity index for time-invariant uncertain parameters. For time-variant uncertain parameter, a novel sensitivity index combining multi-dimensional interval process and similarity degree is proposed which considers the synthetic influence of the group of multiple uncorrelated interval variables. Additionally, an efficient sampling-based method is presented to estimate the global sensitivity analysis indices using the Monte Carlo method and Newton-Cotes formula. Finally, the feasibility and potential benefits of the proposed sensitivity indices are demonstrated by applying them to a 2DTBC made of carbon fiber reinforced polyether ether ketone with thermal ageing consideration.
全局敏感性分析主要侧重于研究时间不变参数对纤维增强复合材料机械性能的影响,而忽略了降解问题。然而,纤维增强复合材料会发生降解,这意味着物理系统是动态的。在灵敏度分析中考虑这种动态行为非常重要。本文提出了一套基于区间法的灵敏度指数,用于衡量考虑降解的二维三轴编织复合材料(2DTBC)全局灵敏度分析中的时变参数和时变参数对输出合成不确定性的影响。为此,我们使用区间过程表示时变不确定参数,并使用区间卡胡宁-洛埃夫展开法用多个不相关的区间变量对其进行描述。然后,我们引入二维区间过程和相似度,为时变不确定参数定义新的灵敏度指标。对于时变不确定参数,我们提出了一种结合多维区间过程和相似度的新型灵敏度指数,它考虑了多个不相关区间变量组的合成影响。此外,还提出了一种基于抽样的高效方法,利用蒙特卡罗方法和牛顿-科茨公式估算全局灵敏度分析指数。最后,将所提出的灵敏度指数应用于由碳纤维增强聚醚醚酮制成的 2DTBC 并考虑热老化因素,从而证明了这些指数的可行性和潜在优势。