今日更新:Composite Structures 3 篇,Composites Science and Technology 2 篇
Investigating the Effect of Cure Schedules and Cure Initiators on Sustainable Composites for Large Offshore Structures
Pothnis J.R., Vélon K., Bhatia G.S., Hejjaji A., Comer A.J.
doi:10.1016/j.compstruct.2023.117648
研究固化时间表和固化引发剂对大型近海结构可持续复合材料的影响
This study evaluates the effect of post-cure schedules and cure initiator form on the mechanical properties of Glass fibre reinforced polymer (GFRP) laminates manufactured using an infusible reactive thermoplastic resin. Tensile, flexural, shear and dynamic mechanical analysis tests were conducted. Fractography was also performed. Specimens fabricated using liquid cure initiator and subjected to an elevated temperature post-cure were the control specimens. Ambient cured specimens decreased by no more than 12% in the case of tensile properties (modulus of 90° specimens) and by < 14.3% in the case of flexural properties (also modulus in 90° specimens). Furthermore, the difference in mechanical properties of 0° specimens fabricated using a powder cure initiator was observed to be within ≈ 7% of respective properties of control specimens. In the context of fabricating thick laminates for large-size offshore structures, the results suggest that an extended ambient post-cure cycle in conjunction with an initiator in powder form can be employed instead of an elevated temperature post-cure schedule with initiator in liquid form. This is economically beneficial since it eliminates infrastructure required for elevated temperature curing/post-curing. The risk of porosity induced due to liquid-based initiators is also avoided.
本研究评估了后固化时间和固化引发剂形式对使用可浸润反应性热塑性树脂制造的玻璃纤维增强聚合物(GFRP)层压板机械性能的影响。研究进行了拉伸、弯曲、剪切和动态机械分析测试。此外,还进行了碎裂分析。使用液态固化引发剂制造的试样和固化后的高温试样为对照试样。常温固化试样的拉伸性能(90° 试样的模量)下降不超过 12%,弯曲性能(90° 试样的模量)下降小于 14.3%。此外,还观察到使用粉末固化引发剂制作的 0° 试样的机械性能与对照试样各自性能的差异在 ≈ 7% 以内。结果表明,在为大型海上结构制造厚层压板时,可以采用延长的环境后固化周期和粉末状引发剂,而不是采用液态引发剂的高温后固化计划。这在经济上是有利的,因为它省去了高温固化/后固化所需的基础设施。此外,还可避免液态引发剂引起的气孔风险。
The effect of load concentration on one-way response of 3D-woven sandwich panels
Mirsalehi Maryam, Kianpour Kiarash, Shahbeyk Sharif, Bakhshi Mohammad
doi:10.1016/j.compstruct.2023.117659
荷载集中对三维编织夹芯板单向响应的影响
As a relatively new class of load bearing elements, 3D-woven sandwich panels (3DWSPs) are emerging in many engineering applications. Similar to other structural elements, the practical usage of the 3DWSPs requires deep understanding around their mechanical properties like elastic stiffness and failure strength. The present study investigates the effect of load concentration on one-way response of the 3DWSPs by: (1) running a comprehensive set of 64 tests to find out the influence of various interfering parameters such as loading span length, the thickness of loaded skin, the shape of loading bar, and panel’s direction, (2) thoughtful interpretation of the elastic and failure results, (3) generation of failure maps, and (4) development of reliable theoretical models for the linear elastic response and the four observed failure mechanisms of skin indentation, skin wrinkling, core shear collapse, and interpillar skin buckling.
作为一类相对较新的承重元件,三维编织夹芯板(3DWSP)正在许多工程应用中崭露头角。与其他结构元件类似,3DWSP 的实际应用需要深入了解其机械特性,如弹性刚度和破坏强度。本研究通过以下方法研究荷载集中对 3DWSP 单向响应的影响:(1)进行 64 项综合测试,以找出加载跨度长度、加载表皮厚度、加载杆形状和面板方向等各种干扰参数的影响;(2)对弹性和破坏结果进行周到的解释;(3)生成破坏图;(4)为线性弹性响应以及表皮压痕、表皮起皱、核心剪切塌陷和柱间表皮屈曲这四种观察到的破坏机制建立可靠的理论模型。
Application of Elastic Metamaterials/Meta-structures in Civil Engineering: A Review
Contreras Nicolás, Zhang Xihong, Hao Hong, Hernández Francisco
doi:10.1016/j.compstruct.2023.117663
弹性超材料/超结构在土木工程中的应用:综述
Inspired by sonic engineering, locally resonant metamaterials have attracted much attention from researchers in civil engineering for their unique characteristics of stress wave attenuation and vibration control capacities. This paper presents a comprehensive review of the latest progress of locally resonant metamaterials and their potential applications in civil engineering for structure protection against dynamic loads. The concepts of metamaterials for stress wave attenuation are introduced first, followed by a comprehensive overview of the historical origins and development of metamaterials. Existing analytical approaches for metamaterials, including theoretical solutions, numerical simulations, and experimental examinations, are summarised. Commonly used meta-structures with internal or external resonators and their applications are reviewed and discussed. Research gaps and future outlooks are also identified and briefed.
受声波工程学的启发,局部谐振超材料因其独特的应力波衰减特性和振动控制能力而备受土木工程研究人员的关注。本文全面综述了局部谐振超材料的最新进展及其在土木工程中用于动态载荷结构保护的潜在应用。首先介绍了用于应力波衰减的超材料概念,然后全面概述了超材料的历史起源和发展。总结了现有的超材料分析方法,包括理论求解、数值模拟和实验检验。回顾并讨论了带有内部或外部谐振器的常用超材料结构及其应用。此外,还确定并简要介绍了研究差距和未来展望。
A new integrated modeling method for predicting low-velocity impact behavior and residual tensile failure of Z-pinned T-joints
Zhou Jianwu, Zhao Zhibin, Jia Liyong, Zhang Chao
doi:10.1016/j.compscitech.2023.110316
预测 Z 销 T 型接头低速冲击行为和残余拉伸失效的新型综合建模方法
Composite T-joints are highly susceptible to low-velocity impact, which can significantly affect their residual performance due to the primary working condition of bearing out-of-plane tensile loads. Currently, most methods that employ multiple models or analytical steps to sequentially assess the mechanical properties of composites generally exhibit certain limitations, leaving room for improvement. This study has developed a finite element (FE) model to simulate the low-velocity impact and post-impact tensile behaviors of carbon fiber reinforced polymers (CFRP) T-joints using an integrated analysis method. The model is based on stress failure criteria and continuous stiffness degradation theory and incorporates corrections to the damage variables. Both the low-velocity impact and quasi-static tensile portions of the model are implemented using an explicit solver with the VUMAT subroutine for calculations in Abaqus. The element damage states are transferred between the two models via a Python script, mitigating the inefficiencies and uncontrollable errors associated with the traditional method of transferring element information between multiple models or analytical steps. Finally, the numerical results of mechanical response and damage states are compared with experimental findings from various perspectives, and the bridging mechanism of Z-pins is thoroughly investigated. The results show that the model exhibits a maximum error of 10.41 % in the main key parameters during low-velocity impact and a maximum error of 10.30 % in the ultimate load during post-impact tension. The model's delamination damage state and final tensile failure mode closely align with the experimental results. Furthermore, a comprehensive analysis of the FE model indicates that the pull-out force of the Z-pin is unrelated to its implantation position or pull-out rate, and the reinforcing effect of the Z-pin becomes significantly apparent only after the CFRP T-joint reaches a certain degree of initial damage.
复合材料 T 型接头极易受到低速冲击,由于其主要工作条件是承受平面外拉伸载荷,这可能会严重影响其剩余性能。目前,大多数采用多种模型或分析步骤依次评估复合材料机械性能的方法普遍存在一定的局限性,有待改进。本研究开发了一种有限元(FE)模型,利用综合分析方法模拟碳纤维增强聚合物(CFRP)T 型接头的低速冲击和冲击后拉伸行为。该模型基于应力失效标准和连续刚度退化理论,并结合了对损伤变量的修正。该模型的低速冲击和准静态拉伸部分均采用显式求解器和 VUMAT 子程序在 Abaqus 中进行计算。元素损伤状态通过 Python 脚本在两个模型之间传输,从而减少了在多个模型或分析步骤之间传输元素信息的传统方法所带来的低效率和不可控误差。最后,从不同角度将机械响应和损伤状态的数值结果与实验结果进行了比较,并深入研究了 Z 销的桥接机制。结果表明,该模型在低速冲击时主要关键参数的最大误差为 10.41%,在冲击后拉伸时极限载荷的最大误差为 10.30%。模型的分层破坏状态和最终拉伸破坏模式与实验结果非常吻合。此外,对 FE 模型的综合分析表明,Z 形销的拔出力与其植入位置或拔出率无关,只有在 CFRP T 形接头达到一定的初始损坏程度后,Z 形销的加固作用才会显著显现。
Rapid and scalable synthesis of novel carboxylated aramid nanofibers for simultaneously improving the strength and toughness of carbon fiber/epoxy laminates
Yu Boshi, Wang Weitao, Zhou Guodong, Song Yihu, Peng Mao
doi:10.1016/j.compscitech.2023.110320
快速、可扩展地合成新型羧基芳纶纳米纤维,以同时提高碳纤维/环氧层压板的强度和韧性
Carbon fiber reinforced composites (CFRCs) are widely used in the aviation, aerospace and automotive industries. The modification of CFRCs with nanomaterials has attracted extensive research interests in recent years. Herein, we report the preparation of novel carboxylated aramid nanofibers (cANFs) by polymerization induced self-assembly, i.e. polycondensation of para-phenylenediamine with terephthaloyl chloride in the presence of a polyamide acid as both a dispersant and surface modifier, for the modification of epoxy resin and CFRCs. cANFs effectively improve the mechanical properties of epoxy resin, and after being sprayed onto CF fabrics, greatly improve the mechanical properties of CFRCs. With the addition of only 0.42 mg/cm2 of cANFs on each CF sheets, storage modulus, flexural strength, flexural modulus and total energy dissipation are enhanced by 27 %, 51 %, 29 % and 67 %, respectively; interlaminar shear strength (ILSS) and Mode II interlayer fracture toughness (G_IIC) are improved by 24 % and 74 %, respectively. cANFs can be comparable or even superior to most previously reported carbon nanomaterials in improving flexural strength and ILSS; and exceed most previously reported electrospun nanofibrous mats in increasing G_IIC. This study provides a new method for the rapid synthesis of functionalized ANFs to simultaneously increase the flexural properties and interlayer properties of CFRCs.
碳纤维增强复合材料(CFRC)广泛应用于航空、航天和汽车行业。近年来,纳米材料对碳纤维增强复合材料的改性引起了广泛的研究兴趣。在此,我们报告了通过聚合诱导自组装(即对苯二胺与对苯二甲酰氯在聚酰胺酸作为分散剂和表面改性剂存在的情况下缩聚)制备新型羧基芳纶纳米纤维(cANFs),用于环氧树脂和 CFRC 的改性。cANFs 可有效改善环氧树脂的机械性能,喷涂到 CF 织物上后可大大改善 CFRC 的机械性能。在每块 CF 片材上仅添加 0.42 mg/cm2 的 cANFs,就能使储能模量、抗弯强度、抗弯模量和总能量耗散分别提高 27%、51%、29% 和 67%;层间剪切强度(ILSS)和模式 II 层间断裂韧性(G_IIC)分别提高 24% 和 74%。cANFs 在提高抗弯强度和 ILSS 方面可与之前报道的大多数碳纳米材料相媲美,甚至更胜一筹;在提高 G_IIC 方面超过了之前报道的大多数电纺纳米纤维毡。这项研究为快速合成功能化 ANFs 提供了一种新方法,可同时提高 CFRC 的抗弯性能和层间性能。