今日更新:Composite Structures 2 篇,Composites Part A: Applied Science and Manufacturing 3 篇,Composites Part B: Engineering 3 篇,Composites Science and Technology 1 篇
Damage evolution modeling of CFRP/Al single-lap screw type blind riveted joints during realistic installation process
Feng Jia-ming, Zhang Jing-dong, Jin Wan-jun, Liao Ri-dong
doi:10.1016/j.compstruct.2024.118023
CFRP/Al 单圈螺钉型盲铆接在实际安装过程中的损伤演变模型
As studies on the damage behaviors of composites during screw type blind riveting are notably absent, this paper seeks to fill this gap by combining experimental tests and numerical simulation methods. A three-dimensional finite element model was proposed, and the simulation results were obtained and validated by experimental data. The light microscope and scanning electron microscope were used to observe the stress state, axial deformation, damage modes, and damage distribution in two load-bearing regions at the initial contact and after installation. The results demonstrated that the preload showed a four-step “zero -steep rise -decline -steep rise” development during installation. The stress and deformation were concentrated in two circular zones, with the maximum axial stress component and deformation of 321 MPa and 0.046 mm, respectively. In two pressed zones, there were three failure modes, with out-plane matrix crushing being the most severe. In-plane matrix cracking damage is seen at a 45° direction in the first layer, with a damage index of 0.745. In addition, the effect of two geometric parameters of the sleeve on the blind head shape, load-bearing regions, and CFRP damage was investigated. The results would build confidence in reducing CFRP damage and enhancing joint integrity.
由于缺乏对复合材料在螺钉型盲铆过程中的损伤行为的研究,本文试图通过结合实验测试和数值模拟方法来填补这一空白。本文提出了一个三维有限元模型,获得了模拟结果,并通过实验数据进行了验证。利用光学显微镜和扫描电子显微镜观察了两个承重区域在初始接触和安装后的应力状态、轴向变形、损伤模式和损伤分布。结果表明,预紧力在安装过程中呈现出 "零--陡升--下降--陡升 "的四级发展过程。应力和变形集中在两个圆形区域,最大轴向应力分量和变形量分别为 321 兆帕和 0.046 毫米。在两个压区中,有三种破坏模式,其中平面外基体破碎最为严重。在第一层的 45° 方向上出现了面内基体开裂破坏,破坏指数为 0.745。此外,还研究了套筒的两个几何参数对盲头形状、承重区域和 CFRP 损伤的影响。这些结果将为减少 CFRP 损坏和提高连接完整性树立信心。
Experimental, analytical, and numerical studies of the energy absorption capacity of bi-material lattice structures based on quadrilateral bipyramid unit cell
Hussain Gharehbaghi, Amin Farrokhabadi
doi:10.1016/j.compstruct.2024.118042
基于四边形双锥单元的双材料晶格结构能量吸收能力的实验、分析和数值研究
The present study investigates the mechanical performance and energy absorption capacity of bi-material 3D lattice structures via experimental, analytical, and numerical approaches. The analytical model has been developed to obtain the effective parameters in energy absorption, such as equivalent elastic modulus and yield stress. Analytical relations based on hyperbolic shear deformation beam theory were extended to calculate the mechanical properties of an extracted unit cell from the lattice structure subjected to applied loads and appropriate boundary conditions. Then, experimental and nonlinear numerical studies have been conducted to analyze the energy absorption properties of the bi-material lattice structure. Quasi-static compression tests were conducted to analyze this lattice structure's mechanical properties and energy absorption capacity. As the numerical study, the elastic-plastic damage behavior was implemented in finite element analyses to examine the nonlinear response of considered structures. The obtained results reveal that the numerical models exhibit an acceptable prediction. According to the results, not only does the use of hybrid structures provide more energy absorption and improve mechanical properties, but also, in comparison to the usual lattice structures fabricated with a single material, the rational combination of two materials makes the bi-material three-dimensional lattice structure to inherit the optimum energy absorption and stiffness.
本研究通过实验、分析和数值方法研究了双材料三维晶格结构的机械性能和能量吸收能力。通过建立分析模型,获得了能量吸收的有效参数,如等效弹性模量和屈服应力。基于双曲剪切变形梁理论的分析关系被扩展用于计算从晶格结构中提取的单元格在外加载荷和适当边界条件下的力学性能。然后,通过实验和非线性数值研究分析了双材料晶格结构的能量吸收特性。通过准静态压缩试验分析了该晶格结构的机械性能和能量吸收能力。在数值研究中,在有限元分析中采用了弹塑性损伤行为,以检查所考虑结构的非线性响应。结果表明,数值模型的预测结果是可以接受的。结果表明,使用混合结构不仅能提供更多的能量吸收并改善力学性能,而且与通常使用单一材料制造的晶格结构相比,两种材料的合理组合使双材料三维晶格结构继承了最佳的能量吸收和刚度。
Effect of shear stresses on fibre direction tensile failure using a new simple and reliable test method with thin plies
Meisam Jalalvand, Mohamad Fotouhi, Michael R. Wisnom
doi:10.1016/j.compositesa.2024.108155
使用一种新的简单可靠的薄层试验方法,分析剪切应力对纤维方向拉伸破坏的影响
A new method of creating in-plane combined tension-shear stress states using only tensile loading is proposed. Thin-ply angle-ply carbon/epoxy laminates are sandwiched between unidirectional glass layers to eliminate any stress concentration around the samples ends and gripping zone. Use of the thin plies successfully suppresses early occurrence of other modes of failure i.e. matrix cracking and free edge delamination, so the first mode of failure is fibre failure in the angle-ply carbon sub-laminate. Compared with other methods of creating combined tension-shear stresses, the proposed technique has a simpler geometry, is significantly easier and cheaper to manufacture and test. Therefore, it provides more repeatable low-scatter experimental results. The obtained experimental results showed that the presence of in-plane shear stresses did not have a significant impact on the tensile fibre-direction failure strain of the tested carbon/epoxy laminate, suggesting that even at high shear stresses, the longitudinal tensile strength of the carbon/epoxy laminate is not significantly reduced.
本文提出了一种仅使用拉伸加载来产生平面内拉伸剪切综合应力状态的新方法。薄层角材碳/环氧层压板夹在单向玻璃层之间,以消除样品端部和夹持区周围的应力集中。薄层的使用成功地抑制了其他失效模式(即基体开裂和自由边缘分层)的早期发生,因此第一种失效模式是角层碳子层压板中的纤维失效。与其他产生拉伸-剪切组合应力的方法相比,所提出的技术具有更简单的几何形状,在制造和测试方面明显更容易、更便宜。因此,它能提供可重复性更高的低散射实验结果。实验结果表明,面内剪应力的存在对测试的碳/环氧层压板的拉伸纤维方向破坏应变没有显著影响,这表明即使在高剪应力下,碳/环氧层压板的纵向拉伸强度也不会显著降低。
Correlation of the permeability and porosity development of carbon/carbon composites during pyrolysis
Tania Lavaggi, Faheem Muhammed, Laure Moretti, John W. Gillespie, Suresh G. Advani
doi:10.1016/j.compositesa.2024.108156
热解过程中碳/碳复合材料渗透性和孔隙率发展的相关性
A cost-effective approach to manufacture Carbon/Carbon composites is to infiltrate carbon fiber preforms with a polymer precursor and pyrolyze it to form the carbon matrix. During pyrolysis, the microstructure changes due to decomposition reactions creating a high degree of porosity consisting of interconnected network of voids and cracks. To densify, the pyrolyzed composite is infiltrated with polymer precursor to fill the porous network. The cycle of pyrolysis followed by infiltration is repeated until the porosity is minimized and the desired density is achieved. The permeability, porosity and viscosity of the polymer govern the infusion pressure and time for the re-infiltration steps. In this work, the permeability of benzoxazine-based Carbon/Carbon composites was measured for different degradation levels with three distinctly different pyrolyzing schedules. The samples were characterized systematically at increasing pyrolyzing temperatures until full conversion of the precursor into carbon matrix was achieved. The porosity of the material was evaluated by X-ray micro-computed tomography and by pycnometry. The through the thickness permeability of the composite was measured via a pulse-decay experiment after each heating step in the pyrolysis cycle. In this experiment pressure decay with time is recorded as air is evacuated from the cavity through the connected pathways of the porous network within the sample. The experimental correlation between the permeability and interconnected porosity of the microstructure is established. It is shown that the pulse-decay test with air effectively characterizes the permeability of the pyrolyzed composite.
制造碳/碳复合材料的一种经济有效的方法是在碳纤维预型件中渗入聚合物前体,然后热解形成碳基体。在热解过程中,微观结构会因分解反应而发生变化,形成由空隙和裂缝相互连接的网络组成的高孔隙率。为了增密,热解后的复合材料会渗入聚合物前驱体,以填充多孔网络。先热解后渗透的循环反复进行,直到孔隙率降到最低并达到所需的密度。聚合物的渗透性、孔隙率和粘度决定了再浸润步骤的浸润压力和时间。在这项工作中,我们测量了苯并恶嗪基碳/碳复合材料在三种截然不同的热解过程中的不同降解水平下的渗透性。在热解温度不断升高直至前驱体完全转化为碳基质的过程中,对样品进行了系统表征。材料的孔隙率是通过 X 射线显微计算机断层扫描和比重测定法进行评估的。在热解循环的每个加热步骤之后,通过脉冲衰减实验测量了复合材料的穿透厚度。在该实验中,当空气通过样品内多孔网络的连接通道从空腔中排出时,压力随时间的衰减被记录下来。实验确定了微观结构的渗透性和相互连接的孔隙率之间的相关性。实验结果表明,空气脉冲衰减测试可有效表征热解复合材料的渗透性。
Toughing epoxy nanocomposites with Graphite-Nanocellulose layered framework
Da Li, Peng E, Yibo Shen, Yueshan Li, Fei Cong, Li Liu, Yudong Huang, Zhen Hu
doi:10.1016/j.compositesa.2024.108159
具有石墨-纳米纤维素层状框架的韧性环氧纳米复合材料
Epoxy nanocomposites hold immense promise for advanced high-performance applications in coatings, adhesives, and fiber-reinforced composite matrices. However, their widespread use is hindered by low fracture toughness, attributed to highly cross-linked network structure. Here, this study presents a synergistic manufacturing strategy combining ultrasonic graphite-nanocellulose assembly and bidirectional freeze casting to fabricate epoxy nanocomposites with remarkable layered architectures. Subsequent infiltration and curing with epoxy prepolymer produce nanocomposites exhibiting a fracture toughness 4.67 times higher than pure epoxy. Both experimental and theoretical analyses demonstrate the nanocomposite's superior crack propagation resistance, attributable to a range of synergistic toughening mechanisms. These include robust interfacial bonding and mechanical interlocking, which arise from fiber pull-out/flake fracture effects, effectively impeding crack growth. Additionally, the distinctive layered architecture promotes tortuous crack pathways, optimizing fracture energy dissipation. This work offers pivotal insights into structure–property relationships, paving the way for the design of next-generation nanocomposites with tailored, superior mechanical performance.
环氧纳米复合材料在涂料、粘合剂和纤维增强复合材料基材等先进的高性能应用领域前景广阔。然而,由于高度交联的网络结构导致的低断裂韧性,阻碍了它们的广泛应用。在此,本研究提出了一种协同制造策略,将超声波石墨-纳米纤维素组装和双向冷冻浇注相结合,制造出具有显著分层结构的环氧纳米复合材料。随后与环氧预聚物进行浸润和固化,生产出的纳米复合材料的断裂韧性是纯环氧的 4.67 倍。实验和理论分析表明,纳米复合材料具有优异的抗裂纹扩展能力,这归功于一系列协同增韧机制。其中包括由纤维拔出/片状断裂效应产生的稳固的界面粘合和机械互锁,从而有效地阻止了裂纹的扩展。此外,独特的分层结构促进了曲折的裂纹路径,优化了断裂能量耗散。这项研究为了解结构与性能之间的关系提供了重要依据,为设计具有量身定制的卓越机械性能的下一代纳米复合材料铺平了道路。
Melt flow characterization of highly loaded cooper filled poly(acrylonitrile-co-butadiene-co-styrene)
Rogério Sakahara, Daniel José da Silva, Shu Hui Wang
doi:10.1016/j.compositesb.2024.111392
高负载铜填充聚(丙烯腈-共丁二烯-共苯乙烯)的熔体流动特性分析
The knowledge of the rheological behavior of hybrid polymer melts is essential to develop fused deposition modeling (FDM) filaments to print metal and ceramic goods. In this contribution, we performed an in-depth analysis of the morphology and the rheological behavior in the linear elastic domain of poly(acrylonitrile-co-butadiene-co-styrene) (ABS) highly filled with copper microparticles functionalized by bioinspired polydopamine, containing polyethylene waxes (PEW) as lubricant agent. The composite systems have potential applicability in manufacturing FDM filaments for the 3D printing of metallic parts. Small amplitude oscillatory shear (SAOS) tests, scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) demonstrate complex relationships among polydopamine coating, filler content, morphology, and rheological properties of the ABS/PEW/Cu system. Furthermore, PEW affects the interface adhesion and shear transmission between the ABS copolymer and the copper filler coated with polydopamine. Also, the polydopamine influences the rheological parameters of the polymer composites, namely retardation and relaxation times, melt flow, and cohesive energy density (Ec).
了解混合聚合物熔体的流变行为对于开发用于打印金属和陶瓷制品的熔融沉积成型(FDM)长丝至关重要。在这篇论文中,我们深入分析了聚丙烯腈-共丁二烯-共苯乙烯(ABS)在线性弹性域中的形态和流变行为,其中高度填充了由生物启发聚多巴胺功能化的铜微粒,并含有聚乙烯蜡(PEW)作为润滑剂。这种复合材料系统可用于制造 FDM 长丝,用于 3D 打印金属零件。小振幅振荡剪切(SAOS)测试、扫描电子显微镜(SEM)和傅立叶变换红外光谱(FTIR)显示了 ABS/PEW/Cu 系统的聚多巴胺涂层、填料含量、形态和流变特性之间的复杂关系。此外,PEW 会影响 ABS 共聚物与涂有聚多巴胺的铜填料之间的界面粘附力和剪切传导性。多巴胺还影响聚合物复合材料的流变参数,即延迟和松弛时间、熔体流动和内聚能密度(Ec)。
3D printing finite element analysis of continuous fiber reinforced composite materials considering printing pressure
Baosheng Liu, Boxiao Dong, Huimin Li, Ruishen Lou, Yi Chen
doi:10.1016/j.compositesb.2024.111397
考虑打印压力的连续纤维增强复合材料 3D 打印有限元分析
Continuous fiber reinforced thermoplastic composite (CFRTC) 3D printing technology, as one of the most remarkable manufacturing techniques, has made significant advancements in various fields, including aerospace and automobile manufacturing. However, there is a dearth of research on simulating the printing process of CFRTC considering printing pressure. This article presents a finite element model that incorporates printing pressure and employs element birth and death technology to simulate the printing process. An in-situ pressure monitoring platform is built to provide real data for simulation. By comparing the simulation results with the experimental results, it is found that the errors of the finite element model simulation results with pressure under different printing parameters are predominantly less than 5 %. Furthermore, the impact of printing temperature and speed on the deformation of the 3D printed CFRTC is analyzed. The deformation of the printed sample is more sensitive to the printing temperature than the printing speed. This study can provide important theoretical guidance for engineering applications.
连续纤维增强热塑性复合材料(CFRTC)三维打印技术作为最卓越的制造技术之一,在航空航天和汽车制造等多个领域取得了重大进展。然而,考虑到打印压力而模拟 CFRTC 打印过程的研究却十分匮乏。本文提出了一种包含印刷压力的有限元模型,并采用元素生灭技术来模拟印刷过程。建立了一个现场压力监测平台,为模拟提供真实数据。通过将模拟结果与实验结果进行比较,发现在不同印刷参数下,有限元模型模拟结果与压力的误差主要小于 5%。此外,还分析了打印温度和速度对 3D 打印 CFRTC 变形的影响。与打印速度相比,打印样品的变形对打印温度更为敏感。这项研究可为工程应用提供重要的理论指导。
Influence of microvascular structured void content on composites subjected to in-plane shear loads
Philip Barnett, Jevan Furmanski, Thao Gibson, Dennis Butcher, Jeffery Baur
doi:10.1016/j.compositesb.2024.111390
微血管结构空隙含量对承受平面剪切载荷的复合材料的影响
Microvascular fiber reinforced composites can be used as multifunctional structures capable of self-healing, thermal regulation, and communication, among others. The inclusion of a small volume of microchannels generally has a minimal impact on the mechanical properties of the composites. In the current work, the in-plane shear properties of microvascular composites containing embedded stainless steel and wall-less microchannels produced through sacrificial material removal were characterized for the first time. Microvascular unidirectional composites were manufactured with precisely located microchannels both aligned with and transverse to the fiber direction, and their in-plane shear properties were tested. Microchannels aligned with the fiber direction were shown to cause a substantial (−7%) decrease in shear strength but had no effect on shear modulus or failure strain. Distortion of the laminate surface around the channels oriented transverse to the fiber axis was observed, resulting in an increase in void content (1–4%), a 9% loss in shear modulus, and a 27% loss in shear strength. The use of a caul plate made the loss in shear strength statistically insignificant, increased the shear modulus by 12–15%, and decreased the shear strain by −25% relative to the baseline composite without microchannels. Digital image correlation showed that the surface strains for transversely oriented samples were interrupted near the microchannels, but post-test x-ray computed tomography and optical microscopy do not show crack redirection. The newfound understanding of the shear response of microvascular composites provides important insights that will enable future engineering designs of multifunctional aerospace structures.
微血管纤维增强复合材料可用作具有自我修复、热调节和通信等功能的多功能结构。加入少量微通道通常对复合材料的机械性能影响很小。在目前的研究中,我们首次对含有嵌入式不锈钢微通道和通过牺牲性材料去除产生的无壁微通道的微血管复合材料的面内剪切性能进行了表征。在制造微血管单向复合材料时,精确定位了与纤维方向一致和横向的微通道,并测试了它们的面内剪切性能。结果表明,与纤维方向一致的微通道会导致剪切强度大幅下降(-7%),但对剪切模量或破坏应变没有影响。在纤维轴横向通道周围观察到层压板表面变形,导致空隙含量增加(1-4%),剪切模量损失 9%,剪切强度损失 27%。与没有微通道的基线复合材料相比,使用 caul 板使剪切强度的损失在统计学上不明显,剪切模量增加了 12-15%,剪切应变减少了 -25%。数字图像相关性显示,横向取向样品的表面应变在微通道附近中断,但测试后的 X 射线计算机断层扫描和光学显微镜并未显示裂纹重新定向。对微血管复合材料剪切响应的新认识为未来多功能航空航天结构的工程设计提供了重要启示。
Silica aerogel-PVA dough: A high internal phase composite with superior thermal insulation and gas barrier
Jianchao Zhang, Yanchun Han, Liying Zhang, Zhaohui Li, Hongsheng Yang, Xiaofang Zhang, Jianming Zhang
doi:10.1016/j.compscitech.2024.110553
二氧化硅气凝胶-PVA团:具有优异隔热性和气体阻隔性的高内相复合材料
Silica aerogel (SA) has shown great promise in constructing thermal insulation composites in various forms. However, it is still challenging to disperse a huge amount of SA particles into other matrices for fabricating superior thermal insulation materials or highly filled masterbatch, owing to its high specific surface area and ultra-low density. Herein, inspired by high internal phase emulsion (HIPE), we successfully prepare processable SA/polyvinyl alcohol (PVA) composites (SA-PVA dough) with over 74 vol% dispersed SA, using a PVA aqueous solution as a binder. This is achieved by gradually mixing a large amount of hydrophobic SA filler into a small amount of PVA aqueous solution. The resulting SA-PVA dough exhibits an internal structure resembling that of HIPEs, with hydrophobic SA particles stabilized in the water phase by amphiphilic PVA chains, tightly packed within the thin continuous PVA aqueous phase. Benefiting from such a HIPE structure, the SA-PVA dough can be easily shaped into various forms and exhibits good applicability in further processing. The dried dough inherits the excellent properties of SA, including ultra-low density, superhydrophobicity (water contact angle: 153°), thermal insulation (thermal conductivity: 0.03 W m−1 K−1), and flame resistance. Moreover, the continuous PVA network structure, combined with the nanoscale pore structure of SA, provides the dough with excellent gas barrier properties, greatly expanding the application scope of SA-based composites.
二氧化硅气凝胶(SA)在以各种形式制造隔热复合材料方面显示出巨大的潜力。然而,由于二氧化硅气凝胶具有高比表面积和超低密度的特点,要将大量二氧化硅气凝胶颗粒分散到其他基质中以制备优异的隔热材料或高填充母料仍具有挑战性。在此,我们受到高内相乳液(HIPE)的启发,利用 PVA 水溶液作为粘合剂,成功制备出了可加工的 SA/ 聚乙烯醇(PVA)复合材料(SA-PVA 面团),其中 SA 的分散比例超过 74%。这是通过在少量 PVA 水溶液中逐渐混合大量疏水性 SA 填料实现的。由此产生的 SA-PVA 面团显示出类似于 HIPE 的内部结构,疏水性 SA 颗粒被两亲性 PVA 链稳定在水相中,紧密地包裹在薄而连续的 PVA 水相中。得益于这种 HIPE 结构,SA-PVA 面团可以很容易地塑造成各种形状,并在进一步加工中表现出良好的适用性。干燥后的面团继承了 SA 的优良特性,包括超低密度、超疏水性(水接触角:153°)、隔热性(导热系数:0.03 W m-1 K-1)和阻燃性。此外,连续的 PVA 网络结构与 SA 的纳米级孔隙结构相结合,使面团具有优异的气体阻隔性能,从而大大拓宽了基于 SA 的复合材料的应用范围。