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
Thermo-Mechanical analysis of laminated Doubly-Curved Shells: Higher order Equivalent Layer-Wise formulation
Francesco Tornabene, Matteo Viscoti, Rossana Dimitri
doi:10.1016/j.compstruct.2024.117995
层叠双曲面壳体的热力学分析:高阶等效层智公式
The paper presents a refined two-dimensional formulation for the thermo-mechanical analysis of laminated doubly-curved shell structures under thermodynamic equilibrium conditions. Both the kinematic configuration variables and the temperature variation with respect to the natural equilibrium state are described with a generalized formulation, following the Equivalent Layer-Wise (ELW) approach employing higher order polynomials, along with some proper zigzag functions. The governing equations are derived from the stationary configuration of the Helmholtz free energy of the system, and a semi-analytical solution is found. In the post-processing phase, the Fourier-based Generalized Differential Quadrature (F-GDQ) is applied to recover the actual three-dimensional response of the doubly-curved shell solid, and very accurate results are obtained for the quantities of both mechanical and heat conduction problems. In addition, the integrals occurring in the theory are performed numerically with the Taylor-based Generalized Integral Quadrature (GTIQ), showing a high level of accuracy with a reduced number of sample points. The model is validated in some case studies where the accuracy of the model is shown, and the numerical predictions are successfully compared with those of refined three-dimensional numerical simulations. After that, an extensive set of parametric investigations is reported, pointing out the effects of the panel’s curvature, lamination schemes and different levels of coupling on the thermo-mechanical structural behavior of the investigated panels.
本文针对热力学平衡条件下的层叠双曲面壳体结构的热机械分析,提出了一种改进的二维公式。运动构型变量和相对于自然平衡状态的温度变化均采用通用公式进行描述,该公式采用了高阶多项式和一些适当的之字形函数的 "等效分层"(ELW)方法。根据系统的亥姆霍兹自由能的静态配置推导出控制方程,并找到半解析解。在后处理阶段,应用基于傅立叶的广义微分正交(F-GDQ)来恢复双曲面壳体固体的实际三维响应,并获得了机械和热传导问题的非常精确的结果。此外,理论中出现的积分采用基于泰勒的广义积分正交(GTIQ)进行数值计算,在样本点数量减少的情况下显示出很高的精度。该模型在一些案例研究中得到了验证,证明了模型的准确性,并成功地将数值预测与精细的三维数值模拟进行了比较。随后,报告了一系列广泛的参数研究,指出了面板的曲率、层压方案和不同程度的耦合对所研究面板的热机械结构行为的影响。
Lightweight zirconium modified carbon–carbon composites with excellent microwave absorption and mechanical properties
Weikang Tang, Shun Dong, Tangyin Cui, Jianqiang Xin, Yongshuai Xie, Guiqing Chen, Changqing Hong, Xinghong Zhang
doi:10.1016/j.compositesa.2024.108102
具有优异微波吸收能力和机械性能的轻质锆改性碳-碳复合材料
With the rapid development of space technology, multi-functional materials with advantages such as heat insulation, lightweight, and electromagnetic (EM) wave absorption have gained broad application prospects. Since porous carbon fiber reinforced carbon (C/C) composites often have lightweight and high heat insulation properties, improving their mechanical and electromagnetic wave absorbing properties will significantly expand their application. In this study, a new kind of zirconium-modified C/C (Zr-C/C) composites prepared by polymer infiltration and pyrolysis using zirconium-modified phenolic resin is presented. By adjusting the content of Zr, the compressive strengths of the composites are increased up to 48% compared with the composites without Zr, while the thermal insulation properties are little changed. The incorporation of zirconium can make the composites exhibit better microwave absorption performance to some extent, and Zr-C/C composites with 10% zirconium have the best microwave absorption performance among all the samples. The excellent electromagnetic wave absorption performance of Zr-C/C composites is attributed to the enhanced interfacial polarization effect and the improved electrical conductivities of the material due to its internal carbon microsphere structure. Multi-functional Zr-C/C composites that combine lightweight, high thermal insulation, high compressive strength, and high electromagnetic wave absorption have obvious applications in fields such as stealth aircraft. Therefore, this work provides a new way to prepare multi-functional materials.
随着航天技术的飞速发展,具有隔热、轻质和吸收电磁波等优点的多功能材料获得了广阔的应用前景。由于多孔碳纤维增强碳(C/C)复合材料通常具有轻质和高隔热性能,因此改善其机械性能和电磁波吸收性能将大大拓展其应用领域。本研究利用锆改性酚醛树脂,通过聚合物浸渗和热解制备了一种新型锆改性碳纤维增强碳(C/C)复合材料(Zr-C/C)。与不含锆的复合材料相比,通过调整锆的含量,复合材料的抗压强度提高了 48%,而隔热性能变化不大。锆的加入能在一定程度上使复合材料表现出更好的微波吸收性能,其中含 10%锆的 Zr-C/C 复合材料的微波吸收性能是所有样品中最好的。Zr-C/C 复合材料优异的电磁波吸收性能得益于界面极化效应的增强以及材料内部碳微球结构带来的导电性能的改善。集轻质、高隔热、高抗压强度和高电磁波吸收能力于一身的多功能 Zr-C/C 复合材料在隐形飞机等领域具有明显的应用前景。因此,这项工作为制备多功能材料提供了一条新途径。
The role of nanoclay in processing immiscible polypropylene and poly (ethylene terephthalate) waste blends using twin screw extrusion
Shawn Martey, Mansoureh Jamalzadeh, Wan-Ting Chen, Margaret J. Sobkowicz
doi:10.1016/j.compositesb.2024.111320
纳米粘土在使用双螺杆挤出机加工不相溶聚丙烯和聚(乙烯对苯二甲酸乙二酯)废料混合物中的作用
Polypropylene and poly(ethylene terephthalate) waste were blended with different types of nanoclay (cloisite Na+, cloisite 20A and CT4270) to understand the role of nanoclay in immiscible polymer blends. The blend morphology was investigated using scanning electron microscopy, the dispersion of the nanoclay was characterized using wide angle x-ray diffraction (WAXD) and rheology. WAXD results showed partial exfoliation for cloisite Na+ and intercalation for cloisite 20A and CT4270. It was predicted that cloisite Na + settled in the PET phase while cloisite 20A settled at the interface of PP and PET. Morphology analysis showed that increasing the concentration of nanoclay in the blend decreased the droplet size. The nanoclay was shown to inhibit coalescence of the droplets causing a decrease due to its rigidity.
将聚丙烯和聚对苯二甲酸乙二酯废料与不同类型的纳米土(cloisite Na+、cloisite 20A 和 CT4270)混合,以了解纳米土在不相溶聚合物共混物中的作用。使用扫描电子显微镜研究了共混物的形态,使用广角 X 射线衍射(WAXD)和流变学表征了纳米土的分散性。WAXD 结果显示,钙钛矿 Na+ 部分剥离,而钙钛矿 20A 和 CT4270 则发生了插层。据预测,loisite Na + 沉淀在 PET 相中,而 cloisite 20A 沉淀在 PP 和 PET 的界面上。形态分析表明,增加混合物中纳米土的浓度会减小液滴尺寸。纳米粘土可抑制液滴的凝聚,从而降低液滴的硬度。
Influence of unidirectional composite failure envelope shape on predicting compressive failure of a laminate with a filled hole
Ivan R. Cózar, José M. Guerrero, Pere Maimí, Albertino Arteiro, Santiago García-Rodríguez, Mélanie Herman, Albert Turon
doi:10.1016/j.compositesb.2024.111352
单向复合材料破坏包络线形状对带填充孔层压破坏预测的影响
In recent decades, several computational models have emerged at the mesoscale for predicting the failure development and strength of composite materials. Nevertheless, the intricate failure mechanisms of composites pose a formidable challenge in developing models capable of consistently reproducing diverse sets of experimental data. Furthermore, the absence of standardised multiaxial tests has hindered consensus on failure envelopes and criteria for composites. In this work, an in-house constitutive model implemented in a finite element code is employed to predict the failure strength of several filled hole compressive carbon/epoxy experimental tests, varying in stacking sequences, sizes, bolt preloads, and other parameters. The influence the selected failure criterion has on the predictions is analysed. The findings indicate a large impact of the failure envelope on both the ultimate compressive strength and developed failure mechanisms. Therefore, the correct adjustment of the failure criteria can be as relevant as defining accurately the material input parameters. These results emphasise the importance of accurately establishing failure envelopes, rather than overemphasising the development of complex models.
近几十年来,在中尺度上出现了一些用于预测复合材料失效发展和强度的计算模型。然而,复合材料的失效机理错综复杂,这对开发能够持续再现各种实验数据的模型提出了严峻的挑战。此外,标准化多轴测试的缺乏也阻碍了对复合材料失效包络和标准达成共识。在这项工作中,采用了一个在有限元代码中实施的内部构成模型来预测多个填充孔压缩碳/环氧实验测试的破坏强度,这些测试在堆叠顺序、尺寸、螺栓预紧力和其他参数方面各不相同。分析了所选失效准则对预测结果的影响。研究结果表明,失效包络线对极限抗压强度和失效机理都有很大影响。因此,正确调整失效标准与准确定义材料输入参数同样重要。这些结果强调了准确确定破坏包络的重要性,而不是过分强调复杂模型的开发。
A honeycomb-inspired carboxymethyl chitosan-covalently link NH2-black phosphorene biobased cellulose green nanocomposites with tremendously enhancement fire safety and thermal conductivity
Kunxin Wang, Zhencai Qu, Hui Yang, Guoming Yuan, Xiu-e Li, Zhijun Liu, Yanhan Tao, Yang Li, Kun Wu, Jun Shi
doi:10.1016/j.compscitech.2024.110535
一种蜂窝状羧甲基壳聚糖共价连接 NH2-黑磷烯生物基纤维素绿色纳米复合材料,可大幅提高防火安全性和导热性能
Biobased carboxymethyl chitosan-modified black phosphorene (BP-CMC) was prepared through an amidation reaction between amino group functionalized black phosphorene (NH2-BP) and CMC. Density functional theory (DTF) express that the adsorption energy between urea and phosphene is −6.28 eV, indicating a strong interaction. The resulting BP-CMC was further applied to reinforce the mechanical, flame-retardant and thermal conductivity performance of honeycomb cellulose nanofiber (CNF) film via vacuum filtration. Cone calorimetry test (CCT) result exhibits that the introduction of 30 wt% BP-CMC significantly promoted the fire safety of CNF. For instance, a 98.41% reduction in smoke production rate (SPR), 92.00 % decline in CO release and a 61.31% decrease in heat release rate (HRR) were observed compared to neat CNF. Furthermore, Thermogravimetric infrared (TG-IR) indicates a significant decrease in the release of flammable gases. Raman spectra verify that the incorporation of 30 wt% BP-CMC improves the graphitization degree of residual chars, thus limiting the transfer of heat and oxygen. The improvement in fire safety is attributed to the formation of an intumescent flame-retardant system, which is rich in carbon source (CMC), acid source (BP) and gas source (amino). Simultaneously, the introduction of 30 wt% BP-CMC into CNF leads to considerable enhancement in thermal conductivity (up to 17.49 %), thermal diffusion (utmost to 43.45 %) and heat capacity (increased by 19.23 %). Moreover, the 30 wt % addition of BP-CMC into CNF possesses excellent mechanical properties with the improvement of toughness (increased by 143.50 %) and tensile strength (increased by 140.90 %). This strategy not only provides a new strategy for functionalizing BP but also upgrades the application potential of BP nanosheets in the fire safety of polymer composite films.
通过氨基官能化黑磷烯(NH2-BP)与 CMC 的酰胺化反应制备了生物基羧甲基壳聚糖改性黑磷烯(BP-CMC)。密度泛函理论(DTF)表明,脲与磷烯之间的吸附能为 -6.28 eV,表明存在很强的相互作用。通过真空过滤,得到的 BP-CMC 进一步用于增强蜂窝纤维素纳米纤维(CNF)薄膜的机械、阻燃和导热性能。锥形量热试验(CCT)结果表明,30 wt% BP-CMC 的引入显著提高了 CNF 的防火安全性。例如,与纯 CNF 相比,产烟率(SPR)降低了 98.41%,一氧化碳释放量减少了 92.00%,热释放率(HRR)降低了 61.31%。此外,热重红外(TG-IR)显示可燃气体的释放量显著减少。拉曼光谱验证了 30 wt% BP-CMC 的加入提高了残留炭的石墨化程度,从而限制了热量和氧气的传递。防火安全性的提高归功于富含碳源(CMC)、酸源(BP)和气源(氨基)的膨胀阻燃体系的形成。同时,在 CNF 中引入 30 wt%的 BP-CMC 可显著提高导热率(高达 17.49%)、热扩散率(高达 43.45%)和热容量(提高 19.23%)。此外,在氯化萘纤维中添加 30 wt % 的 BP-CMC 可提高韧性(提高 143.50 %)和拉伸强度(提高 140.90 %),从而具有优异的机械性能。这种策略不仅为 BP 功能化提供了一种新策略,还提升了 BP 纳米片在聚合物复合薄膜防火安全方面的应用潜力。