今日更新:Composite Structures 4 篇,Composites Part A: Applied Science and Manufacturing 1 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 1 篇
Numerical assessment of fiber distribution effects on strain-hardening cement composites using a rate-dependent Voronoi-Cell-Lattice-Model
Ji Woon Park, Bonhwi Choo, Jeongun Lee, Yun Mook Lim
doi:10.1016/j.compstruct.2024.118515
基于速率相关Voronoi-Cell-Lattice-Model的纤维分布对应变硬化水泥复合材料影响的数值评估
Strain-hardening cementitious composites, also known as high-performance fiber-reinforced cementitious composites, display exceptional strength and toughness not only under static conditions but also under high-speed dynamic loading. The mechanical properties of these composites are greatly influenced by the orientation and dispersion of embedded fibers. However, experimental analysis of complex fiber arrangements in real specimens has limitations, necessitating the development of computational models to understand the impact of fiber distribution. This study examines the effect of fiber distribution conditions on composite behavior using a Voronoi-Cell-Lattice-Model that incorporates reinforcing effects into discrete-type quasi-brittle matrix elements. Firstly, virtual fiber distribution models revealed that as the gauge length of specimens increased, weaknesses in fiber distribution were more likely to form, leading to decreased strength and strain capacity. Secondly, the model demonstrated that favorable fiber orientation relative to the loading direction and minimal sectional deviation in fiber dispersion significantly increased strain capacity and toughness. Finally, the study explored the wall-effect that may arise during specimen fabrication due to the boundary of the casting mold.
应变硬化胶凝复合材料,也被称为高性能纤维增强胶凝复合材料,不仅在静态条件下,而且在高速动态载荷下都表现出优异的强度和韧性。包埋纤维的取向和分散对复合材料的力学性能有很大影响。然而,对真实样品中复杂纤维排列的实验分析存在局限性,需要开发计算模型来了解纤维分布的影响。本研究使用Voronoi-Cell-Lattice-Model来检验纤维分布条件对复合材料性能的影响,该模型将增强效应纳入离散型准脆性基体元素中。首先,虚拟纤维分布模型表明,随着试件规范长度的增加,纤维分布的弱点更容易形成,从而导致强度和应变能力下降。其次,该模型表明,相对于加载方向有利的纤维取向和纤维分散的最小截面偏差显著提高了应变能力和韧性。最后,研究探讨了由于铸型边界在试样制作过程中可能产生的壁效应。
Transient thermal fracture analysis of a honeycomb layer with a central crack
Wenzhi Yang, Zengtao Chen
doi:10.1016/j.compstruct.2024.118518
含中心裂纹蜂窝层的瞬态热断裂分析
Auxetic honeycomb materials with negative Poisson’s ratio received rapidly growing attention in recent years owing to their exceptional thermomechanical properties in constructing sandwich composites. The objective of this article is to investigate the transient thermal behavior and fracture risk of a honeycomb layer with a central crack subject to a sudden thermal shock by theoretical modeling. Two different material configurations along both orthogonal directions, as well as the conventional and auxetic hexagonal alumina honeycomb cells, are examined to illustrate their effects on the thermal stress intensity factors. To solve the thermoelastic governing equations subject to complex boundary conditions, the methodology of integral transform with singular integral equation is employed. The numerical results demonstrate that the auxetic honeycombs can reduce the thermal stress intensity factors significantly compared to their conventional counterparts. The ratio of stress intensity factors in auxetic to non-auxetic honeycombs under the same absolute value of the internal cell angle θ decreases monotonically with increasing |θ|. In addition, the effects of the relative density, crack length, and crack position are investigated. Our findings would provide a more comprehensive understanding of the honeycomb’s fracture behaviors and contribute to the material design of the sandwich composites with honeycomb cores.
负泊松比辅助蜂窝材料由于其在构建夹层复合材料中具有优异的热力学性能,近年来受到越来越多的关注。本文的目的是通过理论建模研究中心裂纹蜂窝层在突然热冲击作用下的瞬态热行为和断裂风险。研究了正交方向上两种不同的材料结构,以及常规和非对称六方氧化铝蜂窝电池,以说明它们对热应力强度因子的影响。为求解复杂边界条件下的热弹性控制方程,采用奇异积分方程的积分变换方法。数值结果表明,与传统蜂窝相比,辅助蜂窝能显著降低热应力强度因子。在相同胞内角θ绝对值下,随|θ|的增大,消声与非消声蜂窝的应力强度因子之比单调减小。此外,还研究了相对密度、裂纹长度和裂纹位置的影响。本研究结果将为蜂窝的断裂行为提供更全面的认识,并有助于蜂窝芯夹层复合材料的材料设计。
Multiscale fatigue life prediction model for CFRP laminates considering the mechanical degradation of its constituents and the local stress concentration of the matrix
Jeong Hwan Kim, Dongwon Ha, Hoil Choi, Gun Jin Yun
doi:10.1016/j.compstruct.2024.118519
考虑构件力学退化和基体局部应力集中的CFRP复合材料多尺度疲劳寿命预测模型
In the present research, a novel approach for predicting the fatigue life of composites is proposed using a multiscale fatigue model. This model considers two critical physical phenomena that occur in CFRP laminates under tension-tension cyclic loading – the degradation of the physical properties of CFRP constituents and the localized stress concentrations within the matrix. To achieve this, Mori-Tanaka’s mean field theory, a well-known micromechanics model, is employed to consider the deterioration of material properties in various phases, which is dependent on the applied stress level. Localized stress concentration phenomena within the matrix of a composite material are common when CFRP laminate is subjected to cyclic loading. The localized stress concentration on a matrix with different numbers of fibers and orientations using representative volume elements (RVE) is investigated. Two other scales of failure criteria are defined to evaluate its constituent at the material level and ply level at the macroscale. A comparison with fatigue experiment data of AS4/3501-6 composite shows good reliability of the proposed multiscale fatigue model.
本研究提出了一种利用多尺度疲劳模型预测复合材料疲劳寿命的新方法。该模型考虑了CFRP层压板在拉伸-拉伸循环载荷下发生的两个关键物理现象——CFRP成分物理性能的退化和基体内的局部应力集中。为了实现这一点,Mori-Tanaka的平均场理论,一个著名的微观力学模型,被用来考虑材料性能在不同阶段的恶化,这取决于施加的应力水平。复合材料复合材料在循环荷载作用下,基体内部存在局部应力集中现象。利用代表性体积元(RVE)研究了不同纤维数和取向的基体上的局部应力集中。定义了另外两个尺度的破坏准则,分别在材料水平和层数水平上对其成分进行评价。与AS4/3501-6复合材料的疲劳试验数据对比表明,所提出的多尺度疲劳模型具有良好的可靠性。
Modified mode I fracture toughness calculation method for composite laminate with large scale fiber bridging
Qingfeng Duan, Haixiao Hu, Dongfeng Cao, Wei Cai, Junkang Xia, Shuxin Li
doi:10.1016/j.compstruct.2024.118521
大型纤维桥接复合材料层合板的修正I型断裂韧性计算方法
Experimental investigation and theoretical analysis have been carried out in this study to assess the application limitation of the current ASTM D5528 method for Mode I fracture toughness calculation of composite laminate with fiber bridging. It is revealed that additional toughening effect introduced by the fiber bridging is not fully considered in the current method and consequently there are uncertainties associated with the fracture toughness calculated by the current ASTM method. Based on the same principle used in the development of the original ASTM method, a modified method is proposed to extend the applicability of the current method. The modified method is verified with mechanisms based cohesive zone modelling and numerical simulations of the Mode I delamination double cantilever beam tests. The significant improvement of the prediction results compared with experimental results by the modified method over the current method demonstrated its applicability for Mode I delamination fracture toughness calculation of composite laminates with large scale fiber bridging.
本研究通过实验研究和理论分析来评估现行ASTM D5528方法在纤维桥接复合材料层合板I型断裂韧性计算中的应用局限性。结果表明,目前的方法没有充分考虑纤维桥接带来的额外增韧效应,因此现行ASTM方法计算的断裂韧性存在不确定性。在与原ASTM方法发展的原理相同的基础上,提出了一种改进的方法,以扩大现有方法的适用性。通过基于力学的内聚区建模和I型脱层双悬臂梁试验的数值模拟,验证了改进方法的有效性。修正后的方法预测结果与实验结果相比有明显改善,表明该方法适用于大规模纤维桥接复合材料层合板的I型分层断裂韧性计算。
Enhancing interfacial performance and fracture toughness of carbon fibre reinforced thermoplastic composites
Yao Chen, Vishnu Prasad, Miray Yasar, Neal Murphy, Alojz Ivankovic
doi:10.1016/j.compositesa.2024.108434
提高碳纤维增强热塑性复合材料的界面性能和断裂韧性
Enhancing the interlaminar fracture toughness of composites significantly improves their load bearing capacity and structural integrity over longer service life by improving their resistance to delamination. The effect of hybrid toughening of Elium-based thermoplastic composites involving polydopamine (PDA), multi-walled carbon nanotubes (MWCNTs) sizing, and polyphenylene sulfide (PPS) veil interlayers was investigated to observe the mechanical response using 3-point bending, interlaminar shear strength, and Mode I fracture toughness tests. The enhancement of fibre–matrix adhesion contributed to improvements in both flexural strength and interlaminar shear strength, while additional toughening mechanisms, such as PDA bridging, PPS pull-out and breakage, and fibre bridging, enhanced the Mode I interlaminar fracture toughness by 218%.
提高复合材料的层间断裂韧性,通过提高复合材料的抗分层能力,显著提高复合材料的承载能力和结构完整性,延长复合材料的使用寿命。通过3点弯曲、层间剪切强度和I型断裂韧性测试,研究了聚多巴胺(PDA)、多壁碳纳米管(MWCNTs)和聚苯硫醚(PPS)复合材料杂化增韧的效果。纤维基质粘附性的增强有助于提高弯曲强度和层间剪切强度,而额外的增韧机制,如PDA桥接、PPS拔出和断裂以及纤维桥接,使I型层间断裂韧性提高了218%。
Stretch-Steering of Highly Aligned Discontinuous Fiber Tape with Automated Fiber Placement
Alexander Legenstein, Lukas Fussel, Dirk Heider, John W. Gillespie, Thomas A. Cender
doi:10.1016/j.compositesb.2024.111801
高度对准不连续纤维带自动铺布的拉伸控制
Highly aligned discontinuous fiber (ADF) composites have been developed with mechanical properties comparable to continuous fiber composites. These materials can be stretched in the fiber direction during processing enabling the production of complex geometries. This study utilizes 57% fiber volume fraction ADF tape comprised of a thermoplastic Polyetherimide (PEI) matrix with 3 mm long IM7 carbon fibers. The Laser-Assisted Automated Fiber Placement (LA-AFP) process is used to study the limits of stretch-steering of ADF tape at small radii. An experimental technique based on photogrammetry was developed to quantify the effect of stretch parameters on the tape strain fields and path placement accuracy. The measurements captured the local in-plane strain tensor (longitudinal, transverse, and shear) across the width and along the length of steered tapes. The results demonstrate that placement path accuracy can be achieved when the tool center point (center of rotation) of the AFP head is located at the nip-point versus the roller centerline, which is typically used for steering continuous fiber tapes at large steering radii. Accuracy of the in-situ tape stretching was demonstrated up to 60% applied stretch strain. The measurements also confirm that when stretch-steering ADF tape, the resulting strain across the tape width is on average the superposition of the in-situ applied tensile strain and in-plane bending computed from the tape width and steering radius. A statistical-based methodology is presented to select the average tensile stretch levels to minimize the probability of defects forming during steering on the inner radius of the tape. The experiments show that a 12.5 mm wide tape can be accurately placed on a 50 mm radius of curvature without defects. This represents a two order of magnitude improvement in steerability over continuous fiber tapes of the same tape width found in peer-reviewed literature.
高度排列的不连续纤维(ADF)复合材料具有与连续纤维复合材料相当的力学性能。这些材料可以在加工过程中向纤维方向拉伸,从而生产出复杂的几何形状。本研究使用由热塑性聚醚酰亚胺(PEI)基体和3mm长的IM7碳纤维组成的纤维体积分数为57%的ADF胶带。采用激光辅助自动铺放光纤(LA-AFP)工艺研究了ADF胶带在小半径处的拉伸转向极限。提出了一种基于摄影测量的实验技术,以量化拉伸参数对胶带应变场和路径放置精度的影响。测量捕获了局部平面内应变张量(纵向、横向和剪切),沿着导向胶带的宽度和长度。结果表明,当AFP头的工具中心点(旋转中心)位于夹尖点而不是滚轮中心线时,可以实现放置路径精度,这通常用于在大转向半径下转向连续纤维带。原位胶带拉伸的精度可达60%的拉伸应变。测量结果还证实,当拉伸导向ADF胶带时,在胶带宽度上产生的应变是现场施加的拉伸应变与根据胶带宽度和导向半径计算的平面内弯曲的平均叠加。提出了一种基于统计的方法来选择平均拉伸水平,以尽量减少在胶带内半径上转向过程中形成缺陷的概率。实验表明,12.5 mm宽的胶带可以精确地放置在半径为50 mm的曲率上而没有缺陷。与同行评议文献中发现的相同磁带宽度的连续光纤磁带相比,这代表了两个数量级的可操作性改进。
Unlocking thermal management capacity: Optimized organic-inorganic hybrid shell phase change microcapsules with controllable structure and enhanced conductivity
Xueting Wang, Huaxin Chen, Dongliang Kuang, Xiao Huan, Zhengyuan Zeng, Cong Qi, Shanjian Han, Guanyu Li
doi:10.1016/j.compscitech.2024.110836
解锁热管理能力:优化结构可控、电导率增强的有机-无机杂化壳相变微胶囊
Microencapsulated phase change material (MPCM) stands as a strong candidate for temperature control of thermal management systems in broad fields like building construction. A novel design strategy for hybridized shell-based MPCM (HMPCM) containing methyl methacrylate (MMA) and silica was developed by the interfacial hydrolysis-condensation method, with characteristics of controllable structure and enhancement in the interaction between the polymer and inorganic thermal conductivity additives. Two hybridized shell structures, including a homogeneous structure and another unique porous cavity structure shaped like a foam, can be obtained by adjusting for preparation conditions. The results reveal that the thermal conductivity is significantly enhanced by hybridized shells compared to pure MMA shells, with a dramatic increment of 92.16%. Therefore, a highly satisfactory microcapsule material characterized by superior thermal conductivity and energy storage efficiency exceeding 99.9% was fabricated. The results of thermal cycling reliability assessments underscore the favorable attributes of microcapsules, encompassing stable charging/discharging behavior, exceptional phase change reversibility, and prompt thermal responsiveness. Moreover, the feasibility of microcapsules in building thermal management applications has been verified. The temperature difference of 10.3 °C between the matrix with and without microcapsules demonstrates the capability of HMPCMs to effectively regulate the temperature of the surrounding environment. Consequently, these newly developed HMPCMs reinforced by hybridized shells are promising thermoregulation materials for thermal management systems that await further applications.
微封装相变材料(MPCM)是建筑施工等广泛领域热管理系统温度控制的有力候选材料。采用界面水解-缩合的方法,提出了一种新型的含甲基丙烯酸甲酯(MMA)和二氧化硅的杂化壳基MPCM (HMPCM)的设计策略,该策略具有结构可控和增强聚合物与无机导热添加剂相互作用的特点。通过调整制备条件可得到两种杂化壳结构,包括均匀结构和另一种独特的泡沫状多孔腔结构。结果表明,与纯MMA壳层相比,杂化壳层的导热系数显著提高,增幅达92.16%。因此,制备了一种导热性能优异、储能效率超过99.9%的令人满意的微胶囊材料。热循环可靠性评估的结果强调了微胶囊的优点,包括稳定的充放电行为、异常的相变可逆性和快速的热响应性。此外,还验证了微胶囊在建筑热管理应用中的可行性。带微胶囊和不带微胶囊的基质温差为10.3℃,表明hmpcm能够有效调节周围环境温度。因此,这些新开发的杂化壳增强的hmpcm是热管理系统中有前途的热调节材料,有待进一步应用。