今日更新：Composite Structures 4 篇，Composites Part A: Applied Science and Manufacturing 1 篇，Composites Part B: Engineering 1 篇Composite StructuresRheology of flexible fiber-reinforced cement pastes: Maximum packing fraction determination and structural build-up analysisZhenbang Guo, Jingping Qiu, Duanping Huang, Kai Liu, Alex Kirichek, Chen Liu, Boyu Chen, Yingliang Zhao, Zhengyao Qudoi:10.1016/j.compstruct.2024.118662柔性纤维增强水泥浆的流变学：最大堆积分数测定和结构堆积分析The maximum packing fraction (φfm) of flexible fibers is an essential parameter for understanding the rheological behavior of flexible fiber-reinforced cement paste (FFRCP). However, direct measurement of φfm of flexible fibers is still lacking. In this study, a shear rheology-based method for direct measurement of φfm was proposed and the assumption of fiber conformation under shear was verified by micro-CT. Based on this, a yield stress model for FFRCP was constructed to explain the entanglement and friction effects in the fiber network. Finally, static yield stress tests and small amplitude oscillatory shear (SAOS) tests were carried out to explore the structural build-up of FFRCP. It was found that the proposed method enables direct determination of φfm through only a few viscosity-fiber content data for a given FFRCP. Furthermore, the proposed model can describe the static yield stress of FFRCP well. Finally, the relative structural build-up rate of FFRCP follows a similar trend as the relative yield stress, with a critical relative fiber volume fraction (0.299) as the boundary. Subsequently, the relative structural build-up gradually deviates from the relative yield stress due to the limiting effect of the fibers.柔性纤维的最大填充分数（φfm）是理解柔性纤维增强水泥浆（FFRCP）流变行为的重要参数。然而，直接测量柔性纤维的φfm的方法尚未出现。本研究提出了一种基于剪切流变的直接测量φfm的方法，并通过微CT验证了纤维在剪切下的形态假设。在此基础上，构建了FFRCP的屈服应力模型，以解释纤维网络中的缠结和摩擦效应。最后，进行了静态屈服应力试验和小振幅振荡剪切（SAOS）试验，以探索FFRCP的结构形成过程。结果表明，该方法可以通过仅提供给定FFRCP的少量粘度-纤维含量数据来直接确定φfm。此外，该模型可以很好地描述FFRCP的静态屈服应力。最后，FFRCP的相对结构形成速率与相对屈服应力相似，以0.299的相对纤维体积分数为边界。随后，由于纤维的限制作用，相对结构应力逐渐偏离相对屈服应力。Examining the effect of the shear coefficient on the prediction of progressive failure of fiber-reinforced compositesBowen Wu, Yang Chen, Chao Zhangdoi:10.1016/j.compstruct.2024.118663研究剪切系数对纤维增强复合材料渐进破坏预测的影响The ultimate damage of composites under tension usually results from fiber damage, which includes both tensile and shear contributions. In this study, the shear coefficient α of the fiber yarn is incorporated into the failure criterion to consider the shear effect of the fiber yarn. An analytical model is then proposed that combines a homogenization method and the enhanced failure criterion to facilitate quick evaluation of the progressive damage and failure of the composite. The sensitivity of α on the behaviors of progressive damage and failure are comprehensively explored for different types of fiber-reinforced composites, including a laminate, a plain weave composite, a two-dimensional triaxially braided composite, and a three-dimensional woven composite. The results indicate that damage and failure behaviors are generally sensitive to the shear coefficient, and composites with more complex textile structure demonstrates greater sensitivity to the α. An analysis of the sensitivity of α for different failure criteria was also conducted, and the results reveal that the Hashin–Hou criterion shows more sensitivity to α than the Chang–Chang criterion, the Hoffman criterion, or the Tsai–Wu criterion. Therefore, the identification of the shear coefficient is significant for exploring the damage and failure behaviors of fiber-reinforced composites.复合材料在拉伸作用下的最终损伤通常是由纤维损伤引起的，纤维损伤包括拉伸和剪切两种作用。在本研究中，将纤维纱的剪切系数α纳入破坏准则中，以考虑纤维纱的剪切效应。在此基础上，提出了一种结合均质化方法和增强破坏准则的分析模型，以方便对复合材料的渐进损伤和破坏进行快速评估。对不同类型的纤维增强复合材料，包括层压复合材料、平纹编织复合材料、二维三轴编织复合材料和三维编织复合材料，全面探讨了α对其渐进损伤和破坏行为的敏感性。结果表明：复合材料的损伤和破坏行为对剪切系数普遍敏感，织物结构越复杂的复合材料对α的敏感性越高；结果表明，Hashin-Hou准则对α的敏感性高于Chang-Chang准则、Hoffman准则和Tsai-Wu准则。因此，确定剪切系数对研究纤维增强复合材料的损伤破坏行为具有重要意义。Interfacial dynamic impermeable crack analysis in dissimilar piezoelectric materials by a new interaction integralShuai Zhu, Hongjun Yu, Zhiyong Wangdoi:10.1016/j.compstruct.2024.118668用一种新的相互作用积分分析不同压电材料界面动态不渗透裂纹Dynamic intensity factors (IFs) provide an important parameter for assessing the failure risk of an interfacial crack for piezoelectric composites exposed to electromechanical impact loadings. In the present research, a new dynamic interaction integral (I-integral) is built for computing the dynamic stress IFs (SIFs) and electric displacement IF (EDIF) of an interfacial crack located in dissimilar inhomogeneous piezoelectric media. Through proper selection of auxiliary variables, the domain expression of I-integral for the inhomogeneous piezoelectric bi-materials does not need to take into account any derivative term for any piezoelectric material property. Further, after rigorous theoretical derivation, the resulting I-integral is still valid for complex models where the integration domain contains other multiple interfaces, regardless of whether the extra materials are straight or curved. Incorporating the modified extended finite element approach, the accuracy is confirmed by checking the dynamic IFs extracted from the I-integral with referenced results. The domain-independence is tested by varying ranges of integration domains for inhomogeneous piezoelectric bi-materials and multi-interface piezoelectric composites. Finally, typical examples are employed to discuss the influences of the direction and magnitude of electric impact loading, combination of polarizations, inhomogeneous degree of piezoelectric bi-materials and complex distribution of diverse material properties on the dynamic IFs.动态强度因子（IFs）是评估压电复合材料在机电冲击载荷作用下界面裂纹失效风险的重要参数。本文建立了一种新的动态相互作用积分（i积分），用于计算不同非均质压电介质中界面裂纹的动应力IF （SIFs）和电位移IF （EDIF）。通过选择适当的辅助变量，非齐次双压电材料的i积分的定义域表达式不需要考虑任何压电材料性质的导数项。此外，经过严格的理论推导，所得的i积分对于积分域包含其他多个界面的复杂模型仍然有效，无论额外的材料是直的还是弯曲的。结合改进的扩展有限元法，通过将从i积分中提取的动态if与参考结果进行比对，验证了该方法的准确性。通过改变非均质双压电材料和多界面压电复合材料的积分域范围来测试其域无关性。最后，通过典型实例讨论了电冲击载荷的方向和大小、极化组合、压电双材料的不均匀程度以及多种材料性能的复杂分布对动态if的影响。Broadband large-scale acoustic topological waveguidesYafeng Chen, Xueyun Wen, Yan Lu, Zhihao Lan, Lei Fan, Harold S. Park, Zhongming Gu, Jie Zhu, Zhongqing Sudoi:10.1016/j.compstruct.2024.118669宽带大尺度声学拓扑波导The acoustic topological waveguide (ATW) hosting topologically protected waveguide modes provides a unique opportunity for achieving large-scale sound transport with robustness. However, prevailing ATWs are typically designed by forward-designed sonic crystals (SCs) based on physical intuitions, unavoidably leading to restricted bandwidths. Here, using the inverse-designed SCs with maximized topological bandgaps, we construct broadband ATWs based on both the quantum spin Hall effect and the quantum valley Hall effect. Broadband large-scale transportation, spin-locked one-way transportation, and the squeezing effect of acoustic waves are demonstrated. This study ushers a new path for designing topological devices with broadband performance for large-scale acoustic wave transportation.承载拓扑保护波导模式的声学拓扑波导（ATW）为实现具有鲁棒性的大规模声音传输提供了独特的机会。然而，目前流行的atw通常是由基于物理直觉的前向设计声波晶体（sc）设计的，这不可避免地导致了带宽的限制。本文利用反向设计的具有最大拓扑带隙的sc，构建了基于量子自旋霍尔效应和量子谷霍尔效应的宽带atw。研究了宽带大尺度输运、自旋锁定单向输运以及声波的压缩效应。该研究为设计具有宽带性能的大规模声波传输拓扑器件开辟了一条新途径。Composites Part A: Applied Science and ManufacturingFused filament fabrication and mechanical characterization of hybrid reinforced polypropylene composites with talc fillers and cellulose nanofibersTatsuto Yamamoto, Chao Luo, Kouta Ide, Kenji Aoki, Yang-Kai Jian, Yu-Hsi Huang, Yasutomo Uetsujidoi:10.1016/j.compositesa.2024.108536 含滑石粉和纤维素纳米纤维的混杂增强聚丙烯复合材料的熔丝制备及力学性能Hybrid reinforced composites with talc fillers and cellulose nanofibers (CNFs) were proposed as a new fused filament fabrication for polypropylene (PP). The effect of filler addition was clarified by experiments and multiscale finite element method (FEM). PP filaments with talc and CNF dispersion were fabricated using maleic anhydride-modified PP. Mechanical properties of printed PP composites were clarified by tensile tests and micro-ball impact tests. The experimentals were in good agreement with the multiscale FEM developed through three-step homogenization. The effects of voids due to poor filling and interfaces between solidified filaments formed by printing were quantified, and the mechanism of property degradation was elucidated. The multiscale FEM indicated that the Young’s modulus and maximum stress had a good linearity with talc content. It was suggested that this linear relationship can be used for efficient design of hybrid PP composites.提出了以滑石粉和纤维素纳米纤维为填料的混杂增强复合材料，作为聚丙烯（PP）的新型熔丝材料。通过实验和多尺度有限元分析，阐明了填料的加入对结构的影响。用马来酸酐改性聚丙烯制备了滑石粉和CNF分散体聚丙烯长丝，并通过拉伸试验和微球冲击试验阐明了印刷PP复合材料的力学性能。实验结果与采用三步均质法建立的多尺度有限元模型吻合较好。定量分析了填充不良产生的空洞和打印固化长丝之间形成的界面对材料性能的影响，并对性能退化的机理进行了分析。多尺度有限元分析表明，滑石的杨氏模量和最大应力与滑石含量呈良好的线性关系。该线性关系可用于杂化PP复合材料的高效设计。Composites Part B: EngineeringPull-off Behavior of Stitched Composite T-JointsAditya Shah, Andrew E. Lovejoy, Rani W. Sullivan, Daniel A. Drakedoi:10.1016/j.compositesb.2024.111911复合材料t型接缝的拉拔性能T-joints are key structural elements that connect opposing surfaces, thereby providing the load path between flat or curved panels (i.e., upper and lower wing skins) and transverse components (i.e., stiffeners). Due to the low interlaminar strength of polymer matrix composites and their geometrical discontinuities, these joints are vulnerable to pull-off loads. To address these issues, through-thickness reinforcements can be employed to enhance the interlaminar capability of these type of joints. In this study, T-joints were manufactured using through-thickness stitching in dry carbon preforms and cured using the vacuum-assisted resin transfer molding (VARTM) process. Stitched and unstitched T-joints were tested under pull-off loading conditions, and surface strain fields were obtained using a 3D digital image correlation system. The ultimate load, displacement, and absorbed energy of the stitched T-joints were greater than their unstitched counterparts by approximately 16%, 34%, and 58%, respectively. Failure mechanisms were identified by examining fracture surfaces using optical microscopy. Results demonstrate that through-thickness stitching significantly improves the damage tolerance of T-joints, which highlights the effectiveness of stitching to enhance the structural integrity of large aerospace components.t形接头是连接相对表面的关键结构元件，从而提供平面或弯曲面板（即上下机翼蒙皮）和横向组件（即加强筋）之间的载荷路径。由于聚合物基复合材料的层间强度低，其几何不连续，这些接头容易受到拉脱载荷的影响。为了解决这些问题，可以采用透厚加固来提高这类节点的层间能力。在这项研究中，t型接头是在干燥的碳预制体中通过厚度拼接制造的，并使用真空辅助树脂传递模塑（VARTM）工艺进行固化。对缝合和未缝合的t型接头进行了拉脱载荷试验，利用三维数字图像相关系统获得了t型接头的表面应变场。缝合t型节点的极限荷载、位移和吸收能量分别比未缝合t型节点大约16%、34%和58%。通过光学显微镜检查断口表面，确定了断裂机制。结果表明，通过厚度拼接可显著提高t型接头的损伤容限，凸显了拼接技术在提高大型航空部件结构完整性方面的有效性。来源：复合材料力学仿真Composites FEM
