【新文速递】2023年11月6日复合材料SCI期刊最新文章

今日更新：Composite Structures 12 篇，Composites Part A: Applied Science and Manufacturing 1 篇

Composite Structures

Torsional mechanical properties and damage mechanism of glass fiber-ramie hybrid circular tube

Ke Jun, Liu Li-jie, Wu Zhen-yu, Le Zhong-ping, Bao Luo, Luo Dong-wei

doi:10.1016/j.compstruct.2023.117680

玻璃纤维-拉米混合圆管的扭转力学性能和损伤机理

Compared with other green natural fibers, ramie has higher mechanical properties and lower cost. In this study, ramie and glass fiber are made into composite circular tubes by two-dimensional braiding, and their torsional mechanical properties and damage mechanisms are investigated. The results show that under the unit wall thickness, compared with the pure glass fiber circular tube, the maximum torsion angle of the hybrid circular tube with ramie and glass fiber spindle ratio of 1:3 increases by 78%, the weight is reduced by 22%, the cost is reduced by 14%, the maximum torque is increased by 10% and the torsional stiffness is reduced by 18.75%. When the loading direction is the same as the implantation direction with more glass fiber content, the failure is caused by buckling. When the loading direction is the same as the implantation direction with more ramie content, the failure is caused by matrix fracture or fiber fracture. The numerical simulation results of the damage model are consistent with the experimental data and the damage morphology, which verifies the effectiveness of the finite element model. These conclusions provide a reference for the engineering application of composite circular tubes with environmental protection, lightweight and anti-torsion failure ability.

与其他绿色天然纤维相比，苎麻具有更高的机械性能和更低的成本。本研究将苎麻和玻璃纤维通过二维编织制成复合圆管，并对其扭转力学性能和损伤机理进行了研究。结果表明，在单位壁厚条件下，与纯玻璃纤维圆管相比，苎麻与玻璃纤维主轴比为 1:3 的混合圆管的最大扭转角增加了 78%，重量减轻了 22%，成本降低了 14%，最大扭矩增加了 10%，扭转刚度降低了 18.75%。当加载方向与玻璃纤维含量较多的植入方向相同时，破坏是由屈曲引起的。当加载方向与植入方向相同且苎麻含量较多时，破坏是由基体断裂或纤维断裂引起的。损伤模型的数值模拟结果与实验数据和损伤形态一致，验证了有限元模型的有效性。这些结论为具有环保、轻质和抗扭转破坏能力的复合材料圆管的工程应用提供了参考。

Free vibration characteristics of integrated fluted-core composite sandwich cylinders

Li Xinyu, Zhang Hao, Yang Haiyang, Luo Junrong, Xiao Zhongmin, Lei Hongshuai

doi:10.1016/j.compstruct.2023.117691

 

集成凹槽夹芯复合材料圆柱体的自由振动特性

Due to their excellent mechanical properties and inherent design versatility, fluted-core composite sandwich structures have gained substantial attention in aerospace and rail transit applications. This study investigated the free-vibration characteristics of composite fluted-core sandwich cylinders. Theoretical models were established following the Rayleigh-Ritz method to predict the natural frequencies of sandwich cylinders under free vibration. The representative cylindrical specimens were prepared using carbon fiber-reinforced plastics (CFRP) and integrated forming co-cured method. To analyze the additional effects of cutouts on vibration performance, specimens with circular cutouts were also fabricated. The vibration tests were performed to determine the natural frequencies and modal shapes under free-free boundary conditions. Validated finite element simulations were employed to assess the accuracy of theoretical results and investigate the influences of geometric parameters on the structural vibration behavior. The results indicated that circumferential lobar modes characterized the first five mode shapes. Significant enhancements were attained by increasing the structural stiffness through adjustments in the circumferential cell number, core-ribs thickness, or size of cutouts. However, when the structural stiffness increases beyond a certain threshold, it has limited effect on the vibration frequencies. The findings provided a comprehensive understanding of the vibration characteristics and optimized design of fluted-core sandwich cylinders.

由于具有优异的机械性能和固有的设计多功能性，凹槽芯复合材料夹层结构在航空航天和轨道交通应用中得到了广泛关注。本研究调查了复合材料凹槽夹芯圆柱体的自由振动特性。采用雷利-里兹法建立了理论模型，以预测夹层圆柱体在自由振动下的固有频率。使用碳纤维增强塑料（CFRP）和集成成型共固化方法制备了具有代表性的圆柱形试样。为了分析切口对振动性能的额外影响，还制作了带有圆形切口的试样。振动测试用于确定自由边界条件下的固有频率和模态振型。为了评估理论结果的准确性，并研究几何参数对结构振动行为的影响，采用了经过验证的有限元模拟。结果表明，圆周叶状模态是前五种模态振型的特征。通过调整圆周单元数、芯肋厚度或切口尺寸来增加结构刚度，可以显著提高振动性能。然而，当结构刚度增加超过一定临界值时，对振动频率的影响有限。研究结果为凹槽夹芯圆柱体的振动特性和优化设计提供了全面的理解。

Optimal thickness distribution design for blending composite laminates using buckling factor prediction

Huynh Thanh N., Lee Jaehong

doi:10.1016/j.compstruct.2023.117693

利用屈曲因子预测混合复合材料层压板的最佳厚度分布设计

This article introduces a two-stage optimization approach for finding optimal blended composite laminate designs where the optimal thickness distribution is predicted based on determined stacking sequences. At each iteration, the stacking sequences are first optimized and then utilized as inputs to predict the optimal regional thicknesses through CNN-based regional buckling factor prediction. By predicting the optimal thicknesses, the proposed process simplifies the highly constrained mixed-variable blending optimization problem, expands its option space, and reduces the number of design variables, all of which improve the combinatorial optimization efficiency. An integration of the proposed approach with a design guideline-based Genetic Algorithm is presented. The approach is applied to solve an 18-panel benchmark blending problem, the acquired solutions are compared with those of previous studies in the literature. The obtained result highlights the significant enhancement in performance of the integrated method.

本文介绍了一种用于寻找最佳混合复合材料层压板设计的两阶段优化方法，根据确定的堆叠顺序预测最佳厚度分布。在每次迭代中，首先优化堆叠序列，然后将其作为输入，通过基于 CNN 的区域屈曲因子预测来预测最佳区域厚度。通过预测最佳厚度，所提出的流程简化了高度受限的混合变量混合优化问题，扩大了其选项空间，并减少了设计变量的数量，所有这些都提高了组合优化效率。本文介绍了建议方法与基于设计准则的遗传算法的整合。该方法被应用于解决一个 18 面板基准混合问题，所获得的解决方案与之前文献中的研究进行了比较。结果表明，集成方法的性能显著提高。

Strength and manufacturability enhancement of a composite automotive component via an integrated finite element / artificial neural network multi-objective optimization approach

Henrique Fonseca João, Jang Woojung, Han Dosuck, Kim Naksoo, Lee Hyungyil

doi:10.1016/j.compstruct.2023.117694

通过综合有限元/人工神经网络多目标优化方法提高汽车复合材料部件的强度和可制造性

This study addresses the enhancement of an injection-molded fiber-reinforced plastic / metal hybrid automotive structure and its plastic injection molding process through the integration of the finite element method, artificial intelligence and evolutionary search methods. Experiments are conducted to validate the finite element models. The orthogonal array and Latin hypercube methods are employed to generate a database via finite element analysis. The database is then used to train artificial neural networks that accurately evaluate component distortion, manufacturing time, and structural strength. A genetic optimization algorithm is applied to identify optimal process parameters. The procedure was demonstrated to simultaneously reduce product warpage and manufacturing time by 10 and 62 %, respectively, when compared with the reference manufacturing process while strength is kept above the required levels with a reduced number of required data points. A more in-depth investigation into the causes of strength variation and deformation is also provided. The results contribute to the advance of robust composite automotive structures with superior quality, manufactured through efficient processes.

本研究通过整合有限元方法、人工智能和进化搜索方法，对注塑成型的纤维增强塑料/金属混合汽车结构及其注塑成型工艺进行改进。实验验证了有限元模型。采用正交阵列法和拉丁超立方法通过有限元分析生成数据库。然后利用该数据库训练人工神经网络，以准确评估部件变形、制造时间和结构强度。遗传优化算法用于确定最佳工艺参数。结果表明，与参考制造流程相比，该流程可同时将产品翘曲和制造时间分别减少 10% 和 62%，同时在减少所需数据点数量的情况下将强度保持在所需水平之上。此外，还对强度变化和变形的原因进行了更深入的研究。这些结果有助于推动通过高效工艺制造出质量上乘的坚固复合材料汽车结构。

Formation of non-uniform fibre distribution and its effect on the flexural performance of pultruded GFRP box beams

Qi Songming, Alajarmeh Omar, Alhawamdeh Mohammad, Shelley Tristan, Schubel Peter, Rendle-Short Kendric, Zeng Xuesen

doi:10.1016/j.compstruct.2023.117695

 

非均匀纤维分布的形成及其对拉挤 GFRP 箱形梁弯曲性能的影响

This study investigates the effect of non-uniform fibre distribution (NUFD) as a defect in the pull-winding manufacturing process on the mechanical properties of pultruded glass fibre-reinforced polymer (GFRP) box section profiles. These profiles exhibit balanced mechanical properties but are susceptible to NUFD during production, negatively affecting local buckling capacity. Experimental and numerical analyses were conducted on pultruded GFRP profiles manufactured under three winding tension configurations, resulting in a 5% variance in load capacity during bending. Results show that corner NUFD influences local buckling capacity more than flange NUFD. Specifically, corner NUFD decreases load capacity by up to 20%, while flange NUFD increases it by up to 3%. Conversely, the effect of NUFD location is insignificant to the failure determined by the material strength without buckling instability. Moreover, a linear relationship between the rotational restraint coefficient and corner fibre volume fraction provides insight into the impact of material imperfections on load capacity.

本研究调查了非均匀纤维分布（NUFD）这一拉卷制造过程中的缺陷对拉挤玻璃纤维增强聚合物（GFRP）箱型材机械性能的影响。这些型材具有均衡的机械性能，但在生产过程中容易出现 NUFD，对局部屈曲能力产生负面影响。我们对在三种缠绕张力配置下生产的拉挤 GFRP 型材进行了实验和数值分析，结果显示弯曲时的负载能力差异为 5%。结果表明，转角 NUFD 比凸缘 NUFD 对局部屈曲能力的影响更大。具体来说，角部无损探伤最多会降低 20% 的承载能力，而凸缘无损探伤最多会提高 3%。相反，NUFD 位置的影响对于由材料强度决定的无屈曲不稳定性的失效并不明显。此外，旋转约束系数与边角纤维体积分数之间的线性关系有助于深入了解材料缺陷对承载能力的影响。

Manufacturing and characterization of an interpenetrating metal matrix composite reinforced with a 3D-printed metallic glass lattice structure (Ni60Nb20Ta20)

Dittmann Kerstin, Trauth Anna, André Weidenmann Kay

doi:10.1016/j.compstruct.2023.117697

用 3D 打印金属玻璃晶格结构（Ni60Nb20Ta20）增强的互穿金属基复合材料的制造与表征

Metallic glasses (MG) exhibit remarkable properties, like high strength, hardness, and elastic strain limit due their amorphous structure. But they also exhibit low ductility and brittle behavior, making them less suitable for monolithic components. Therefore, MG offer high potential for use as a reinforcing phase in a ductile matrix. Especially interpenetrating metal matrix composites (MMCs) are suitable, since good interfacial adhesion can be achieved due to the metallic character of the MG and mechanical properties can be further enhanced by the interpenetrating structure. Temperature during manufacturing process must be below crystallization temperature of the MG. Until now, interpenetrating MMCs have been manufactured by infiltrating the metal matrix foam with MG, requiring a high melting temperature of the matrix and thus excludes lightweight metals. In this work it was possible to infiltrate an open porous lattice structure of MG (Ni60Nb20Ta20) due to its high crystallization temperature with AlSi12 by gas pressure infiltration resulting in a novel MMC. X-ray diffraction measurements confirm that no crystallization occurred during infiltration. Micrographs show a good infiltration quality and interfacial bonding between both phases. An increase in Young's modulus of 28% and compressive strength in the MMC can be achieved compared to the AlSi12-matrix.

金属玻璃（MG）因其无定形结构而具有高强度、硬度和弹性应变极限等显著特性。但它们也表现出低延展性和脆性，因此不太适合用于整体元件。因此，MG 作为韧性基体中的增强相具有很大的应用潜力。特别是互穿金属基复合材料（MMC），因为 MG 的金属特性可以实现良好的界面粘附性，互穿结构可以进一步提高机械性能。制造过程中的温度必须低于 MG 的结晶温度。迄今为止，互穿式 MMC 都是通过在金属基泡沫塑料中渗入 MG 来制造的，这要求基体具有较高的熔化温度，因此不包括轻质金属。在这项工作中，由于 MG（Ni60Nb20Ta20）的结晶温度较高，因此可以通过气压渗透将其与 AlSi12 一起渗透到开放多孔晶格结构中，从而制造出新型 MMC。X 射线衍射测量证实，在浸润过程中没有发生结晶。显微照片显示，两相之间的浸润质量和界面结合良好。与 AlSi12 基质相比，MMC 的杨氏模量和抗压强度提高了 28%。

Concurrent stacking sequence and layout optimization of stiffened composite plates using a spectral element method and an index-based optimization technique

Alan Salih, Shaban Nefize, Sendur Gullu Kiziltas, Bediz Bekir

doi:10.1016/j.compstruct.2023.117698

使用谱元法和基于指数的优化技术同时优化加劲复合板的堆叠顺序和布局

Stiffened composite panels are increasingly used in aerospace, marine, and automotive industries due to their lightweight and high-strength properties. However, determining the optimal stacking sequence and/or layout of stiffeners concurrently while adhering to manufacturing guidelines and empirical rules is challenging. To address this issue, we propose a novel one-step optimization framework that couples a highly accurate and computationally efficient spectral element modeling technique with an index-based optimization approach that inherently satisfies the manufacturing guideline and empirical rules. Spectral element modeling (SEM) combines the high accuracy of spectral (meshless) methods with the geometric flexibility of finite element methods. To determine the optimal design, an index-based optimization is proposed to decrease the number of design variables and remove the constraints. We demonstrated the accuracy and computational performance of SEM with results obtained by finite element analysis on composite laminates with and without a cutout. Finally, we applied the proposed optimization framework to various stiffened composite (balanced and symmetric) laminates of up to 200 plies to demonstrate its capability and efficiency.

由于具有轻质高强的特性，加劲复合板越来越多地应用于航空航天、船舶和汽车行业。然而，在遵守制造准则和经验规则的同时，确定加劲件的最佳堆叠顺序和/或布局极具挑战性。为解决这一问题，我们提出了一种新颖的一步优化框架，该框架将高精度、高计算效率的谱元建模技术与基于索引的优化方法结合起来，从本质上满足了制造准则和经验规则。谱元建模（SEM）结合了谱（无网格）方法的高精度和有限元方法的几何灵活性。为了确定最佳设计，我们提出了一种基于指数的优化方法，以减少设计变量的数量并消除约束。我们通过对有切口和无切口的复合材料层压板进行有限元分析所获得的结果，证明了 SEM 的准确性和计算性能。最后，我们将提出的优化框架应用于多达 200 层的各种加劲复合材料（平衡和对称）层压板，以证明其能力和效率。

Post-Buckling Behavior and Collapse of Double-Double Composite Single Stringer Specimens

Vescovini A., Li C.X., Paz J., Jin B., Manes A., Bisagni C.

doi:10.1016/j.compstruct.2023.117699

双层复合单弦杆试件的屈曲后行为和坍塌

This paper presents the work on six single-stringer specimens manufactured using the card-sliding technique with non-crimp fabrics and adopting a Double-Double (DD) stacking sequence. These specimens, representative of sub-structure level components, are used to investigate post-buckling and failure in aerospace structures. Two specimens maintain a constant thickness cross-section, while four are tapered, two of which incorporate a Teflon insert in the stringer flange. All specimens are tested under compression loading conditions, inducing skin buckling, skin-stringer separation, and eventual collapse. Numerical simulations are validated by experimental results and serve to analyze the specimens behavior and the failure mode. The load versus displacement curves of both experimental tests and Finite Element Method (FEM) analyses are compared, along with the out-of-plane displacement field. Subsequently, the observed failure modes are discussed, focusing on the various mechanisms that occurred and considering the impact of flanges and stiffener tapering. Both the FEM simulations and experimental tests demonstrate good agreement, with the flanges tapering revealing notable results. This offers promising evidence of a viable solution to optimize aeronautical structures and enhance resistance to skin-stringer separation.

本文介绍了采用无皱织物的卡片滑动技术和双倍（DD）堆叠顺序制造的六个单弦试样。这些试样代表子结构级部件，用于研究航空航天结构的后屈曲和失效。两个试样保持恒定厚度的横截面，四个试样为锥形，其中两个试样在支撑翼缘中加入了特氟龙插入物。所有试样均在压缩加载条件下进行测试，以诱发蒙皮屈曲、蒙皮-弦杆分离和最终坍塌。实验结果对数值模拟进行了验证，并对试样的行为和破坏模式进行了分析。比较了实验测试和有限元法（FEM）分析的载荷与位移曲线以及平面外位移场。随后，对观察到的失效模式进行了讨论，重点是发生失效的各种机理，并考虑了法兰和加劲件锥度的影响。有限元模拟和实验测试均显示出良好的一致性，其中法兰锥度的结果尤为显著。这为优化航空结构和提高抗蒙皮弦杆分离能力提供了可行的解决方案。

A Dovetail Core Design for Joints in Composite Sandwich Structures

Aqel Rawan, Severson Patrick, Elhajjar Rani

doi:10.1016/j.compstruct.2023.117700

复合材料夹层结构接缝的燕尾芯设计

The increase in the size of composite sandwich structures requires the introduction of core splices to join various segments. In this study, a novel core splice joint configuration is studied and proposed for composite sandwich structures of thick aluminum-based honeycomb core and facesheets made from carbon fibers and epoxy matrix. Experimental and numerical efforts investigate the impact of dovetail joints with different tenon angles on the auxiliary behavior of composite sandwich structures. The results are compared to conventional or straight-core splices without dovetail features. The core-splice interaction with the complete mechanical behavior of the system was assessed by subjecting the fabricated specimens to combinations of bending and shear forces. Additionally, 3D-finite element models compared normal and shear stresses in the splice material and the core/splice interface among the dovetail configurations considered. The study shows that depending on the dovetail joint detail, an ultimate strength increase between 13 to 51% is achieved compared to the strength from currently used straight joints. In terms of toughness, the dovetail specimens show a 2% to 35% higher toughness compared to the standard straight joints.

随着复合材料夹层结构尺寸的增大，需要采用芯材拼接来连接各个部分。本研究针对由厚铝基蜂窝芯材和由碳纤维及环氧基质制成的面材组成的复合材料夹层结构，研究并提出了一种新型芯材拼接接头结构。实验和数值研究了不同榫角的燕尾接头对复合材料夹层结构辅助行为的影响。实验结果与传统或无燕尾槽的直芯拼接进行了比较。通过对制作的试样施加弯曲力和剪切力组合，评估了芯材拼接与系统整体机械行为的相互作用。此外，三维有限元模型还比较了所考虑的燕尾槽配置中拼接材料和芯材/拼接界面的法向应力和剪切应力。研究结果表明，根据燕尾接头细节的不同，与目前使用的直接头相比，其极限强度可提高 13% 至 51%。在韧性方面，与标准直接头相比，燕尾槽试样的韧性提高了 2% 至 35%。

Form-finding of elastic gridshell based on spatial elastica model

WANG Xianheng, CHEN Cong, ZHANG Jinsong, QIU Xinming

doi:10.1016/j.compstruct.2023.117653

基于空间弹性模型的弹性网格壳的形状确定

In engineering design, elastic gridshells, which are composed of a number of elastic rods, are advantageous because they are lightweight, easy to construct, and low-cost as well as have a long-span space. However, the form-finding of a gridshell is challenging owing to the large deformation and strong geometric-nonlinearity of the structure. In this paper, a new form-finding method based on spatial elastica model (FMSE) is proposed. The deformations of elastic rods, obtained via the elliptic integral solution of spatial elastica, is integrated into the overall deformation of the gridshell. A set of transcendental equations is solved using the quasi-Newton method to ensure that the deformation of the gridshell satisfies the given boundary conditions. To validate the proposed FMSE method, desktop experiments (designed using the theory of Chebyshev nets) are performed on gridshells made of glass fiber reinforced polymer rods. The predictions of the FMSE method agree well with the experimental results. Accordingly, the proposed FMSE method is expected to have potential applications in elastic gridshells, on the investigations of form-finding, load-bearing capability, non-local deformation behavior, and also stability of structures.

在工程设计中，由许多弹性杆组成的弹性栅壳具有重量轻、易于建造、成本低以及跨度空间大等优点。然而，由于网格壳结构的大变形和强几何非线性，网格壳的形状搜索具有挑战性。本文提出了一种基于空间弹性模型（FMSE）的全新找形方法。通过空间弹性椭圆积分求解得到的弹性杆的变形被整合到网格壳的整体变形中。使用准牛顿法求解一组超越方程，以确保网格壳的变形满足给定的边界条件。为了验证所提出的 FMSE 方法，在玻璃纤维增强聚合物棒制成的网格壳上进行了桌面实验（利用切比雪夫网理论设计）。FMSE 方法的预测结果与实验结果非常吻合。因此，所提出的 FMSE 方法有望应用于弹性网格壳，研究结构的寻形、承载能力、非局部变形行为以及稳定性。

Design and optimization of the dual-functional lattice-origami metamaterials

Jiang Tengjiao, Han Sihao, Han Qiang, Li Chunlei

doi:10.1016/j.compstruct.2023.117670

双功能晶格原形超材料的设计与优化

This study proposes a multi-scale composite lattice-origami metamaterial (MCLOM) to achieve excellent bandgap characteristics and energy absorption capacities. The MCLOMs are constructed by considering the high impedance mismatch of lattice structures, the spatial deformability of origami structures, and the tunability of the components in multi-scale composite materials. Firstly, elastic wave propagation characteristics are analyzed in the Bloch wave framework, revealing the realization of complete bandgaps and their generation mechanism by mode shape analysis and transmission spectrum. Subsequently, an optimization framework integrating the particle swarm optimization (PSO) algorithm is developed to maximize the first bandgap’s bandwidth by adjusting various component parameters. Under optimal distribution, the proposed metamaterials achieve remarkable improvements of 289% and 271% in the design objectives of two lattice-origami metamaterials with 90° dihedral angle compared to the initial distribution. It can be demonstrated that non-uniform distributions of multi-scale composite materials are dramatically effective for broadband wave attenuation. Additionally, while striving to widen the bandgap, the energy absorption capacities of structures are also crucial. The effect of the distribution of multi-scale composite materials with the optimal bandgap on the energy absorption performance is investigated. The results reveal that the optimal distribution of the lattice-origami metamaterials yields notable improvements of 48.26% and 34.86% under low-velocity impact, and 37.41% and 25.19% under medium-velocity impact. This work presents innovative concepts and approaches for devising and implementing novel dual-functional metamaterials, undoubtedly propelling the continual progress of material science and engineering technology in the times ahead.

本研究提出了一种多尺度复合晶格-折纸超材料（MCLOM），以实现优异的带隙特性和能量吸收能力。考虑到晶格结构的高阻抗失配性、折纸结构的空间变形性以及多尺度复合材料中各成分的可调谐性，构建了 MCLOM。首先，在布洛赫波框架下分析了弹性波的传播特性，通过模形分析和透射谱揭示了完整带隙的实现及其产生机制。随后，结合粒子群优化（PSO）算法建立了一个优化框架，通过调整各种组件参数来最大化第一带隙的带宽。在最佳分布条件下，与初始分布相比，所提出的超材料在两个具有 90° 二面角的晶格原形超材料的设计目标上分别实现了 289% 和 271% 的显著改进。这表明，多尺度复合材料的非均匀分布对宽带波衰减具有显著效果。此外，在努力拓宽带隙的同时，结构的能量吸收能力也至关重要。本文研究了具有最佳带隙的多尺度复合材料的分布对能量吸收性能的影响。结果表明，晶格原形超材料的最佳分布在低速撞击下分别产生了 48.26% 和 34.86% 的显著改善，在中速撞击下分别产生了 37.41% 和 25.19% 的显著改善。这项研究提出了设计和实现新型双功能超材料的创新理念和方法，无疑将推动材料科学和工程技术在未来时代的不断进步。

Multi-phase metamaterials containing framework structures to program thermal expansion and mechanical performances

Wang Kaiyu, Chen Jiaxin, Wei Kai, Wang Rong, Yang Xujing

doi:10.1016/j.compstruct.2023.117671

包含框架结构的多相超材料可实现热膨胀和机械性能编程

Due to suffering the thermal and mechanical loadings simultaneously, metamaterials integrating with the customizable coefficient of thermal expansion (CTE) and high mechanical performances are desirable to ensure the thermal and structural stabilities in engineering devices. Hence, various multi-phase metamaterials with programmable CTEs and mechanical performances were developed. Specifically, inspired by the mixture of multiple phases in composites and the rigid rotations of framework structures in materials with negative CTE, a typical pyramid unit was introduced. Additionally, two series of metamaterials were systematically designed, which were constructed in batches from different units through the matrix transformation method. The CTEs of the metamaterials were theoretically established and analyzed. Besides, mechanical performances, including relative density, stiffness and strength were also calculated and discussed. The results suggest that the directionality and magnitude of CTEs are determined by the constructing principle of multi-fold rotations. In addition, the large ranges of programmable CTEs and high load-bearing capacity are available in the devised metamaterials by reasonably modulating the geometrical parameters. The thermal expansion and mechanical performances of the metamaterials could be synchronously programmed. The diversity of the phase configurations and geometrical architectures in the metamaterials offers the opportunity to satisfy manifold requirements in different applications.

由于要同时承受热负荷和机械负荷，具有可定制热膨胀系数（CTE）和高机械性能的超材料是确保工程设备热稳定性和结构稳定性的理想选择。因此，各种具有可编程热膨胀系数和机械性能的多相超材料应运而生。具体来说，受复合材料中多相混合以及负 CTE 材料中框架结构刚性旋转的启发，引入了典型的金字塔单元。此外，还系统地设计了两个系列的超材料，通过矩阵变换方法由不同单元分批构建而成。理论上确定并分析了超材料的 CTE。此外，还计算并讨论了超材料的力学性能，包括相对密度、刚度和强度。结果表明，CTE 的方向性和大小由多倍旋转的构造原理决定。此外，通过合理调节几何参数，设计出的超材料还具有大范围的可编程 CTE 和高承载能力。超材料的热膨胀和机械性能可同步编程。超材料相位配置和几何结构的多样性为满足不同应用的多方面要求提供了机会。

Composites Part A: Applied Science and Manufacturing

Observations of Wrinkling in Non-Crimp Fabrics during Multi-Ply Stack Forming using In situ XCT Scanning

Jimenez-Martin Claudia, Maes Vincent, Rosini Sebastian, Smith Ronan, Sinclair Ian, Mavrogordato Mark, McMahon Turlough, Kratz James

doi:10.1016/j.compositesa.2023.107880

使用原位 XCT 扫描观察多层堆叠成形过程中非起皱织物的起皱情况

This paper shows the internal evolution of wrinkles occurring in a single diaphragm forming process using time-resolved in situ XCT scanning. Forming trials were carried out over a curved C-spar geometry using Non-Crimp Fabric (NCF) plies of 45°/135°, 0°/90° and 0°/45° orientations arranged in single-orientation and mixed-orientation stacks. Results show most of the diaphragm movement and change in wrinkle size, shape, and location occurs in the early application (<0.1 bar) of vacuum. The further application of vacuum shows consolidation, with wrinkle size decreasing but shape and location remaining largely unchanged. Single-orientation stacks of 45°/135° plies showed the closest resemblance between initial and final wrinkling, while mixed-orientation stacks showed complex wrinkling due to the 0° plies creating internal ply separation due to excess length. Overall, the study shines a light on the internal interaction between layers that occurs during wrinkling, showing mechanisms only observable with XCT.

本文利用时间分辨原位 XCT 扫描技术展示了单隔膜成形过程中皱纹的内部演变过程。成型试验是在弯曲的 C 型支柱几何形状上进行的，使用的是以单一方向和混合方向堆叠排列的 45°/135°、0°/90° 和 0°/45° 方向的无皱褶织物 (NCF) 层。结果表明，隔膜的大部分移动以及皱纹大小、形状和位置的变化都发生在施加真空的初期（小于 0.1 巴）。进一步施加真空后会出现巩固，皱纹的大小会减小，但形状和位置基本保持不变。由 45°/135° 层组成的单取向叠层显示出初始和最终皱纹之间最接近的相似性，而混合取向叠层则显示出复杂的皱纹，这是因为 0° 层由于长度过长而产生了内部层间分离。总之，这项研究揭示了起皱过程中发生的层间内部相互作用，显示了只有 XCT 才能观察到的机制。