今日更新:Composite Structures 1 篇,Composites Part A: Applied Science and Manufacturing 2 篇,Composites Part B: Engineering 1 篇,Composites Science and Technology 3 篇
An efficient moving-mesh strategy for predicting crack propagation in unidirectional composites: Application to materials reinforced with aligned CNTs
Domenico Ammendolea, Francesco Fabbrocino, Lorenzo Leonetti, Paolo Lonetti, Arturo Pascuzzo
doi:10.1016/j.compstruct.2024.118652
预测单向复合材料裂纹扩展的有效移动网格策略:在定向碳纳米管增强材料中的应用
This paper presents an efficient numerical approach for reproducing the process of crack propagation inside unidirectional composites subjected to general loading conditions, with special reference to epoxy materials enhanced with embedded aligned CNTs. This approach involves a traditional FE framework improved by the Moving Mesh (MM) technique based on the Arbitrary Lagrangian-Eulerian (ALE) formulation and the Interaction Integral Method (M−integral). The MM serves as a powerful numerical tool to simulate the discrete crack advance with minimal remeshing, thus reducing the computational complexities. Instead, the M−Integral method, formulated for generally anisotropic materials, has been employed to extract the mixed-mode Stress Intensity Factors (SIFs), which are necessary to define the crack onset condition and propagation direction on the basis of the modified Maximum Hoop Stress Criterion. The proposed strategy includes the extended rule of mixtures to evaluate the homogenized elastic properties of nano-reinforced composites. The validity of the proposed methodology has been assessed through comparisons with experimental data and numerical results available in the literature.
本文提出了一种有效的数值方法来模拟单向复合材料在一般载荷条件下的裂纹扩展过程,特别针对嵌入定向碳纳米管增强的环氧材料。该方法采用了基于任意拉格朗日-欧拉(ALE)公式和相互作用积分法(M−积分)的移动网格(MM)技术改进的传统有限元框架。MM作为一种强大的数值工具,可以用最小的网格来模拟离散裂纹的进展,从而降低了计算的复杂性。相反,采用M−积分方法,为一般各向异性材料制定,提取混合模式应力强度因子(SIFs),这是在修正的最大环向应力准则的基础上定义裂纹开始条件和扩展方向所必需的。该方法采用扩展混合规则来评价纳米增强复合材料的均质弹性性能。通过与文献中可用的实验数据和数值结果的比较,评估了所提出方法的有效性。
Moisture effects on the transverse compressive behaviour of single flax fibres
Anouk Chevallier, Wajih Akleh, Jason Govilas, Florian Boutenel, Violaine Guicheret-Retel, Johnny Beaugrand, Cédric Clévy, Vincent Placet
doi:10.1016/j.compositesa.2024.108509
水分对亚麻纤维横向压缩性能的影响
Studying the effects of moisture on the mechanical behaviour of single flax fibres, particularly in the transverse direction, is of key importance for the reliable use of biobased composites exposed to varying humidity levels. In this study, the apparent transverse Young’s modulus evolution of single flax fibres is recorded through repeated compressive load/unload cycles conducted at three Relative Humidity (RH) levels— 40%, 60%, and 80%. No significant changes in the apparent Young’s modulus, determined from the unloading, were observed during transverse compression cycling or under increasing humidity conditions. The absence of apparent softening with the rise in RH is attributed to the expression of two antagonistic mechanisms: wall softening due to plasticisation and structural stiffening linked to fibre compaction. Intriguingly, a noteworthy transverse stiffening is recorded at 40% RH following the humidification and drying of the fibre. This outcome is ascribed to a hornification phenomenon.
研究水分对单个亚麻纤维力学性能的影响,特别是在横向上的影响,对于暴露在不同湿度水平下的生物基复合材料的可靠使用至关重要。在这项研究中,通过在三种相对湿度(RH)水平(40%、60%和80%)下重复压缩加载/卸载循环,记录了单个亚麻纤维的表观横向杨氏模量演变。在横向压缩循环或增加湿度条件下,从卸载确定的表观杨氏模量没有显著变化。随着相对湿度的升高,没有明显的软化是由于两种拮抗机制的表达:由于塑化引起的壁软化和与纤维压实有关的结构硬化。有趣的是,在纤维的加湿和干燥后,在40% RH下记录了一个值得注意的横向硬化。这种结果归因于角质化现象。
Freeform trajectory generation for fiber reinforced polymer composites additive manufacturing with variable-deposition-width
Danjie Bi, Pengcheng Hu, Zhaoyu Li, Jiancheng Hao, Kai Tang, Molong Duan
doi:10.1016/j.compositesa.2024.108516
变沉积宽度纤维增强聚合物复合材料增材制造的自由曲面轨迹生成
Continuous carbon fiber-reinforced polymers (CCFRPs) printing is a unique additive manufacturing (AM) technique that enhances design flexibility and enables on-demand production of lightweight, high-strength composite parts. However, current trajectory generation methods for CCFRPs-AM have limited control over fiber placement and flexible matrix path infill, particularly in complex regions, often using constant deposition widths that restrict path coverage and mechanical properties. To address these limitations, this paper presents a variable-deposition-width (VDW) trajectory generation method for CCFRPs-AM. The approach integrates a streamline-based technique for fiber paths with a Voronoi diagram-based method for matrix path generation, optimizing path placement based on 2D stress fields while accommodating user-defined fiber paths. Mechanical tests by us on fabricated open-hole composite components demonstrate that the proposed approach enhances the interfacial bonding and increases the maximal loading capacity under tensile stress.
连续碳纤维增强聚合物(CCFRPs)打印是一种独特的增材制造(AM)技术,可提高设计灵活性,并可按需生产轻质、高强度复合材料部件。然而,目前CCFRPs-AM的轨迹生成方法对纤维放置和柔性矩阵路径填充的控制有限,特别是在复杂区域,通常使用恒定的沉积宽度,限制了路径覆盖和机械性能。为了解决这些限制,本文提出了一种CCFRPs-AM的变沉积宽度(VDW)轨迹生成方法。该方法集成了基于流线的光纤路径技术和基于Voronoi图的矩阵路径生成方法,基于二维应力场优化路径放置,同时适应用户定义的光纤路径。我们对预制的裸眼复合材料构件进行了力学试验,结果表明该方法增强了界面结合,提高了拉伸应力下的最大载荷能力。
Unveiling Exotic Multi-Scale Microstructure Transformation and Crack Formation Mechanisms in Eutectic Ceramic Composite by Laser Powder Bed Fusion
Zhonglin Shen, Haijun Su, Minghui Yu, Yang Cao, Yinuo Guo, Hao Jiang, Yuan Liu, Xiang Li, Dong Dong, Peixin Yang, Zhuo Zhang, Min Guo, Wentao Yan
doi:10.1016/j.compositesb.2024.111883
揭示激光粉末床熔合共晶陶瓷复合材料的多尺度显微组织转变和裂纹形成机制
Laser powder bed fusion (LPBF) represents an advanced and versatile technology. Exploiting its distinctive advantages for direct and rapid fabrication of complex-structured melt-grown oxide eutectic ceramic composite represents a pioneering yet challenging endeavor. In this work, LPBF is creatively employed to fabricate turbine blade-shaped, in-situ ternary eutectic ceramic composite. Through the integration of experimental procedures, Finite element method (FEM) simulations, and numerical analyses, an innovative design and manufacturing of oxide eutectic ceramic composites have been successfully established. Comprehensive FEM simulations, with detailed interface characteristic analysis, have revealed macro-scale cracks induced by intense maximum principal stress, and micro-cracks stemming from significant interfacial energy disparities among the three constituent phases. The applications of rapid solidification and nucleation theories have facilitated profound insights into the formation mechanisms of multi-scale exotic microstructures, including top-layer coarse dendrites, rosette-like spherical internally grown eutectic colony within layers, and columnar eutectic colonies with ultra-fine lamellar eutectic structures. Micro-mechanical property testing reveals enhanced performance in the inter-layer ultra-fine lamellar eutectic structure, which is attributed to a refined eutectic spacing of approximately 61 nm, coupled with distinct and robust bonding interfaces. These groundbreaking achievements, focusing on the processing-microstructure-property relationship in the fabrication of gas turbine blade-shaped solidified eutectic ceramic composite using LPBF, provide invaluable theoretical insights and data. This knowledge is crucial for the LPBF production of high-temperature structural materials, highlighting its significant potential applications in fields of aerospace and mechanical engineering.
激光粉末床熔合(LPBF)是一种先进的、通用的技术。利用其独特的优势,直接和快速制造复杂结构的熔融生长氧化物共晶陶瓷复合材料代表了一个开创性但具有挑战性的努力。在这项工作中,LPBF创造性地用于制造涡轮叶片形状的原位三元共晶陶瓷复合材料。通过实验、有限元模拟和数值分析相结合,成功建立了氧化物共晶陶瓷复合材料的创新设计和制造方法。综合有限元模拟和详细的界面特征分析,揭示了由强烈的最大主应力引起的宏观裂纹和由三个组成相之间显著的界面能差异引起的微观裂纹。快速凝固和成核理论的应用,有助于深入了解多尺度外来组织的形成机制,包括顶层粗枝晶、层内玫瑰花状球形共晶集落和具有超细层状共晶组织的柱状共晶集落。微观力学性能测试表明,层间超细层状共晶结构的性能得到了提高,这是由于共晶间距细化到约61 nm,结合界面明显且坚固。这些突破性的成果,聚焦于利用LPBF制造燃气轮机叶片型凝固共晶陶瓷复合材料的加工-显微组织-性能关系,提供了宝贵的理论见解和数据。这些知识对于高温结构材料的LPBF生产至关重要,突出了其在航空航天和机械工程领域的重要潜在应用。
Rate-dependent mechanical and self-monitoring behaviors of 3D printed continuous carbon fiber composites
Lanting Liu, Yinggang Miao, Qiong Deng, Xiaobin Hu, Yu Zhang, Ruifeng Wang, Yongshuai Wang, Mengjia Su, Yiu-Wing Mai
doi:10.1016/j.compscitech.2024.110914
3D打印连续碳纤维复合材料的速率依赖力学和自监测行为
3D printed continuous carbon fiber reinforced polymer (CFRP) composites offer great advantages in structural health monitoring (SHM) owing to their flexibility in complex structure fabrication. Considering the many prospective aerospace applications, tensile experiments were designed to study their mechanical and self-sensing behaviors under a wide range of strain rates. The turning points in the resistance vs strain curves reveal the damage evolution of the specimens and divide the deformations into linear straining and damage evolution regions. Fiber elongation and fiber contact reduction dominate the resistance increase in the linear straining region and the resistance curve behaves linearly. But fiber breakage is the predominant factor in the damage evolution region, yielding a concave resistance curve. Strength, fracture strain, and resistance variation are found to display significant strain rate dependencies that increase with increasing strain rate. Numerous microcracks are formed and evolved into secondary cracks under dynamic loading. This process absorbs more strain energy and produces more carbon fiber breaks, sustaining a higher fracture strain and resistance variations. A model is developed to describe the strain- and strain rate- dependent resistance behaviors, and the predicted results agree well with experimental data. The outcomes of this work contribute to the application of 3D printed continuous CFRP composites in SHM.
3D打印连续碳纤维增强聚合物(CFRP)复合材料由于其在复杂结构制造中的灵活性,在结构健康监测(SHM)方面具有很大的优势。考虑到许多潜在的航空航天应用,设计了拉伸实验来研究它们在大范围应变速率下的力学和自传感行为。电阻应变曲线的拐点反映了试样的损伤演化过程,并将变形划分为线性应变区和损伤演化区。在线性应变区,纤维伸长和纤维接触减少主导了电阻的增加,电阻曲线呈线性变化。但纤维断裂是损伤演化区的主导因素,形成凹形的阻力曲线。强度、断裂应变和阻力变化显示出显著的应变速率依赖性,随应变速率的增加而增加。在动加载作用下,形成了大量微裂纹并演变为次生裂纹。这个过程吸收更多的应变能,产生更多的碳纤维断裂,保持更高的断裂应变和阻力变化。建立了一个模型来描述应变和应变速率相关的电阻行为,预测结果与实验数据吻合较好。本研究成果有助于3D打印连续碳纤维增强塑料复合材料在SHM中的应用。
In situ Analysis of Three-Dimensional Microcrack Propagation in Cross-Ply Laminates Using Synchrotron Radiation X-ray Computed Tomography
Kosuke Takahashi, Ryuto Higashiyama, Gaoge Xue, Takashi Nakamura
doi:10.1016/j.compscitech.2024.110918
交叉层合板三维微裂纹扩展的同步辐射x射线计算机断层原位分析
This study utilized synchrotron radiation X-ray computed tomography to investigate the initiation and propagation of microcracks in cross-ply carbon fiber-reinforced polymer (CFRP) laminates under mechanical loading. Initially, static tensile loads were applied to detect microcracks within a ply thickness of 160 μm. The crack propagation was subsequently characterized, extending across adjacent carbon fibers and along the interfaces of individual fibers into the material's interior. The experiment was repeated with cyclic loading, where the laminates were imaged periodically. Analysis of the images revealed the presence of microcracks and provided insights into their progression from the point of initiation. Notably, microcracks exhibited the initiation toward the interior of the material rather than across the neighboring carbon fibers, whereas their propagation is more significant across the adjacent carbon fibers particularly under the static loading. Under cyclic loading, however, the crack propagation toward the interior of the material was more pronounced, implying different propagation behavior than when under static loading. These findings were also validated through the distribution of energy release rate and stress triaxiality along the crack tip calculated by finite element analysis.
本研究利用同步辐射x射线计算机断层扫描技术研究了机械载荷作用下交叉碳纤维增强聚合物(CFRP)层合板微裂纹的萌生和扩展。最初,应用静态拉伸载荷检测厚度为160 μm的微裂纹。随后对裂纹扩展进行了表征,裂纹扩展穿过相邻的碳纤维,并沿着单个纤维的界面延伸到材料内部。在循环加载下重复实验,其中层压板周期性成像。对图像的分析揭示了微裂纹的存在,并提供了从起始点到其进展的见解。值得注意的是,微裂纹在材料内部萌生,而不是在相邻的碳纤维上萌生,而在静态载荷下,微裂纹在相邻碳纤维上的传播更为显著。而在循环加载下,裂纹向材料内部扩展更为明显,其扩展行为与静态加载时不同。通过有限元分析计算裂纹尖端的能量释放率分布和应力三轴性,验证了上述结论。
Breaking mechanical performance trade-off in 3D-printed complex lattice-inspired multi-cell tubes under axial compression
Yulong He, Yanjiao He, Jiapeng Sun, Xin Li, Ming-Hui Lu, Yan-Feng Chen
doi:10.1016/j.compscitech.2024.110920
轴向压缩下3d打印复杂点阵多胞管的断裂力学性能权衡
It is a long-standing challenge to balance the structural load capacity and toughness in the design of lightweight multi-cell tubes. To tackle this challenge, we provide two kinds of complex lattice-inspired composite multi-cell tubes. The composite multi-cell tubes consist of inner polylactic acid (PLA) complex lattice-inspired multi-cell tubes and outside aluminum tubes. The energy absorption capacity of these multi-cell tubes was evaluated under quasi-static axial compression. The effect of cross-sectional topology and thermal exposure were considered in the experiment. The results show that the integration of PLA tubes within aluminum tubes significantly enhances their energy absorption performance, effectively addressing the limitations posed by the low fracture strain of PLA. The synergistic effect between the aluminum and PLA tubes mitigates the fracture instability and distributes the load more evenly, resulting in improved specific energy absorption (SEA) and mean crushing force (MCF) up to 103.32% and 184.38%, respectively. In these composite tubes, a global self-similar layout can markedly enhance its energy absorption. However, their mechanical properties decrease significantly at 323K compared to room temperature. Overall, this research provides a novel approach to enhancing the mechanical performance of PLA tubes, paving the way for their application in engineering fields requiring lightweight and high-strength structures.
在轻量化多孔管的设计中,如何平衡结构承载能力和韧性是一个长期存在的挑战。为了解决这一挑战,我们提供了两种复杂的晶格启发复合多细胞管。复合多胞管由内聚乳酸(PLA)复合点阵多胞管和外铝管组成。在准静态轴向压缩条件下,对多胞管的吸能能力进行了评价。实验中考虑了截面拓扑结构和热暴露的影响。结果表明,将聚乳酸管集成在铝管中显著提高了聚乳酸管的吸能性能,有效地解决了聚乳酸管断裂应变低的局限性。铝管与PLA管的协同作用减轻了断裂失稳,载荷分布更加均匀,比能吸收(SEA)和平均破碎力(MCF)分别提高了103.32%和184.38%。在这些复合管中,整体自相似布局可以显著提高其能量吸收。但在323K时,与室温相比,其力学性能明显下降。总的来说,本研究为提高聚乳酸管的力学性能提供了一种新的方法,为其在需要轻量化和高强度结构的工程领域的应用铺平了道路。