今日更新:Composite Structures 3 篇,Composites Part A: Applied Science and Manufacturing 2 篇
CARBON FABRIC REINFORCED CEMENTITIOUS MORTAR CONFINEMENT OF CONCRETE CYLINDERS: THE MATRIX EFFECT FOR MULTI-PLY WRAPPING
Alessio Cascardi, Salvatore Verre, Luciano Ombres, Maria Antonietta Aiello
doi:10.1016/j.compstruct.2024.117919
碳纤维布增强水泥砂浆约束混凝土圆柱体:多层包覆的基体效应
The confinement of columns is one of the most used strengthening techniques for reinforced concrete (RC) framed structures being able to improve both the axial strength and ductility. In the last decades, technological advances provided different tools/solutions for the achievement of an effective confinement, among all: the RC-jacket, the steel ties, the fibre reinforced polymer (FRP) wrapping, and lastly the fabric reinforced cementitious mortar (FRCM) plastering. The proposed research aims to investigate two open-issues and their combination related to the use of the FRCM, such as the multi-ply confinement and the role of the inorganic matrix with respect to the confinement effectiveness. At this scope, a set of pure compression tests were carried out to evaluate the representative laws of the mechanical behaviour of confined columns, namely the axial stress versus axial/lateral strain. Consequently, the axial strength and ductility gains were computed. In particular, the investigated variables were the grade of the inorganic matrix, by varying its compressive strength (i.e. ∼25 MPa and ∼50 MPa), and the number of plies (i.e. 1, 2 and 3). The results showed that the higher gain in term of axial strength and ductility is met by increasing the mortar’s compressive/tensile strength and, at the same time, the number of plies. Lastly, available design-oriented analytical models were found able to predict the FRCM-confinement effect in terms of strength. In addition, an available analysis-oriented model accurately foreseen the axial stress-strain law when dealing with the high-grade strength matrix confining in both single, double and triple layer of FRCM-system.
柱约束是钢筋混凝土框架结构中最常用的加固技术之一,可以提高结构的轴向强度和延性。在过去的几十年里,技术的进步为实现有效的限制提供了不同的工具/解决方案,其中包括:rc护套,钢带,纤维增强聚合物(FRP)包裹,最后是织物增强水泥砂浆(FRCM)抹灰。提出的研究旨在调查与FRCM使用相关的两个开放问题及其组合,例如多层约束和无机基质在约束有效性方面的作用。在此范围内,进行了一组纯压缩试验,以评估承压柱力学行为的代表性规律,即轴向应力与轴向/侧应变的关系。因此,计算了轴向强度和延性增益。特别是,研究的变量是无机基质的等级,通过改变其抗压强度(即~ 25 MPa和~ 50 MPa)和层数(即1、2和3)。结果表明,通过增加砂浆的抗压/抗拉强度,同时增加层数,可以实现更高的轴向强度和延性增益。最后,发现现有的面向设计的分析模型能够在强度方面预测frp - cm约束效应。此外,现有的面向分析的模型在处理单层、双层和三层frcm体系的高等级强度矩阵时,都能准确预测轴向应力-应变规律。
Preparation and performance enhancement of n-eicosane/polyvinyl alcohol/MXene flexible phase change composites with sandwich structure
Jinlong Zheng, Yong Deng, Dajun Luo, Fuzhong Wu, Xinyi Dai
doi:10.1016/j.compstruct.2024.117930
夹心结构正二糖烷/聚乙烯醇/MXene柔性相变复合材料的制备及性能增强
In this work, flexible n-eicosane (C20)/polyvinyl alcohol (PVA)/MXene flexible composite PCMs (CPM fc-PCMs) with sandwich structure were designed and prepared. The sandwich structure was prepared by layer-by-layer coating, which was beneficial for enhancing performance of flexible phase change composites. Specifically, the sandwich structure of CPM fc-PCMs could effectively solve the leakage and poor thermal reliability of C20, while significantly improving their thermal storage, mechanical and photothermal conversion performance. The results showed that CPM fc-PCMs had high heat storage capacities, and the maximum latent heat reached □157.43 J/g. It was worth noting that the decrease of latent heat of 1CPM70 after 200 phase transition cycles was 2.58 %, showing good thermal reliability due to the micro-morphology and microstructure of CPM fc-PCMs. The addition of MXene with rich surface functional groups could provide hydrogen bonding sites to enhance the bond between layers, so that the CPM fc-PCMs demonstrated excellent flexibility and mechanical performance (□16.65 MPa). MXene could effectively improve the light-to-heat conversion ability of CPM fc-PCMs, indicating that the CPM fc-PCMs had a good temperature regulation ability in the thermal management of human wearable clothing. In addition, the CPM fc-PCMs demonstrated good thermal stability by TG analysis.
本文设计并制备了具有夹层结构的柔性正二十烷(C20)/聚乙烯醇(PVA)/MXene复合材料(CPM fc-PCMs)。采用逐层涂覆的方法制备夹层结构,有利于提高柔性相变复合材料的性能。具体而言,CPM fc- pcm的夹层结构可以有效解决C20的泄漏和热可靠性差的问题,同时显著提高其储热、机械和光热转换性能。结果表明:CPM fc- pcm具有较高的储热能力,最大潜热可达□157.43 J/g;值得注意的是,经过200次相变循环后,1CPM70的潜热下降幅度为2.58 %,由于CPM fc- pcm的微观形貌和微观结构,表现出良好的热可靠性。表面官能团丰富的MXene的加入可以提供氢键位点,增强层间的键合,使得CPM fc- pcm具有优异的柔韧性和力学性能(□16.65 MPa)。MXene能有效提高CPM fc- pcm的光热转换能力,说明CPM fc- pcm在人体可穿戴服装热管理中具有良好的温度调节能力。此外,热重分析表明,CPM fc-PCMs具有良好的热稳定性。
A New Mechanism Based Cohesive Zone Model for Mode I Delamination Coupled with Fiber Bridging of Composite Laminates
Qingfeng Duan, Haixiao Hu, Dongfeng Cao, Wei Cai, Shuxin Li
doi:10.1016/j.compstruct.2024.117931
基于新机制的复合材料层合板I型剥离与纤维桥接的内聚区模型
Based on identification of the two distinguishing delamination mechanisms within the two delamination zones associated with Mode I fracture toughness testing of composite laminates using the well-known ASTM standard double cantilever specimen (DCB), a new mechanism based cohesive zone model (MB-CZM) is proposed in this work. Overcoming the limitations with the widely used superposed cohesive zone models, the proposed MB-CZM develops two traction-separation relations to individually represent the two distinctive delamination mechanisms. One for the quasi-brittle linear elastic behavior of composite material and another for the nonlinear characteristics of fiber bridging which is commonly simplified with tri-linear to multi-linear approximation in the previous cohesive zone models (CZMs). Energy decomposition is carried out based on different damage and toughening mechanisms associated with delamination initiation and propagation. The proposed new MB-CZM is implemented in the finite element analysis via two UMAT subroutines and used in the numerical simulations. The good agreement of the simulation results with the experimental results provides the verification and demonstration of the capabilities of the proposed MB-CZM.
基于ASTM标准双悬臂试件(DCB)复合材料层合板I型断裂韧性测试中两个分层区中两种不同的分层机制,提出了一种新的基于机制的内聚区模型(MB-CZM)。克服了广泛使用的叠加内聚带模型的局限性,提出的MB-CZM模型建立了两种牵引-分离关系,分别代表了两种不同的分层机制。一种是复合材料的准脆性线弹性行为,另一种是纤维桥接的非线性特性,这种非线性特性在以往的黏聚区模型中通常被简化为三线性到多线性近似。能量分解是基于与分层萌生和扩展相关的不同损伤和增韧机制。提出的新MB-CZM通过两个UMAT子程序在有限元分析中实现,并用于数值模拟。仿真结果与实验结果吻合较好,验证了所提出的MB-CZM的性能。
Hollow glass microsphere/polydopamine/glass fiber reinforced composites with high thermal insulation performance by inhibiting conductive and radiative heat transfer
Ahram Jeong, Seung Mo Son, Suyeon Lee, Dong Gi Seong
doi:10.1016/j.compositesa.2024.108041
中空玻璃微球/聚多巴胺/玻璃纤维增强复合材料通过抑制导热和辐射传热而具有高绝热性能
Glass fiber-reinforced polymer (GFRP) is commonly used as an insulating lightweight material because of low thermal conductivity. Due to the increasing demand for lightweight composites with the extreme thermal insulation properties, a highly insulating composite was proposed with inhibiting both conductive and radiative heat transfer. We embedded hollow glass microspheres (HGMs), as a conductive heat transfer inhibitor, onto glass fiber by leveraging the adhesive properties and black color of polydopamine, as a radiative heat transfer inhibitor. The new GFRP integrated with polydopamine and HGMs improved thermal insulation properties by 14% compared with neat GFRP and infrared blocking performance while increasing interlaminar and impact strengths by 48.7%, 28.4% and maintaining similar tensile and compressive strengths. Moreover, it improved flame retardant properties with 27.1% reduction in heat release rate and 25 s of ignition time delay. Based on the excellent multi-functions, it can be applied to industries such as cryogenic container parts.
玻璃纤维增强聚合物(GFRP)由于其导热系数低,通常被用作绝缘轻质材料。由于对具有极端隔热性能的轻质复合材料的需求日益增加,提出了一种既能抑制导热又能抑制辐射传热的高隔热复合材料。我们利用聚多巴胺作为一种辐射传热抑制剂的粘附特性和黑色,将作为传导传热抑制剂的中空玻璃微球(HGMs)嵌入到玻璃纤维上。与纯GFRP相比,添加聚多巴胺和hgm的新型GFRP的隔热性能和红外阻隔性能提高了14%,层间强度和冲击强度分别提高了48.7%和28.4%,并保持了相似的拉伸和抗压强度。此外,它还能提高阻燃性能,放热率降低27.1%,点火时间延迟25 s。基于其优异的多功能,可应用于低温容器零件等行业。
A novel prediction method for nanoplatelets content dependent yield strength of graphene nanoplatelets reinforced metal matrix composites at different temperatures
Pan Dong, Mengqing Yang, Jianzuo Ma, Shifeng Zheng, Weiguo Li, Wenli Pi
doi:10.1016/j.compositesa.2024.108038
石墨烯纳米片增强金属基复合材料在不同温度下屈服强度随纳米片含量的预测方法
Especially, the quantitative relationship between the thickness and volume fraction of graphene and the grain size of graphene nanoplatelets reinforced metal matrix composites was revealed, based on which the influence of grain refinement, load transfer and dislocation strengthening on the yield strength of composites and their evolution with temperature was quantitatively characterized. Furthermore, by introducing the weakening effect of graphene agglomeration on associated control mechanism of yield strength, a prediction model of temperature dependent yield strength of graphene nanoplatelets reinforced metal matrix composites was established. The proposed prediction approach is verified by comparing the predictions with the experimental data in other literature. Moreover, using the established model, the quantitative effects of length and thickness of nanoplatelets on the yield strength of composites and their evolution with temperature were carried out. This research also provides an effective method for investigating the optimal volume fraction and failure volume fraction of added graphene.
特别是揭示了石墨烯的厚度和体积分数与石墨烯纳米片增强金属基复合材料晶粒尺寸之间的定量关系,在此基础上定量表征了晶粒细化、载荷传递和位错强化对复合材料屈服强度的影响及其随温度的演变规律。在此基础上,引入石墨烯团聚弱化对屈服强度的相关控制机理,建立了石墨烯纳米片增强金属基复合材料屈服强度的温度依赖预测模型。通过与其他文献的实验数据进行比较,验证了所提出的预测方法。利用所建立的模型,定量分析了纳米薄片长度和厚度对复合材料屈服强度的影响及其随温度的变化规律。该研究也为研究添加石墨烯的最佳体积分数和失效体积分数提供了有效的方法。