Experimental investigation of engineered geopolymer composite for structural strengthening against blast loads

The recent increase in blast/bombing incidents all over the world has pushed the development of effective strengthening approaches to enhance the blast resistance of existing civil infrastructures.Engineered geopolymer composite(EGC)is a promising material featured by eco-friendly,fast-setting and strain-hardening characteristics for emergent strengthening and construction.However,the fiber optimization for preparing EGC and its protective effect on structural elements under blast scenarios are uncertain.In this study,laboratory tests were firstly conducted to evaluate the effects of fiber types on the properties of EGC in terms of workability,dry shrinkage,and mechanical properties in compression,tension and flexure.The experimental results showed that EGC containing PE fiber exhibited suitable workability,acceptable dry shrinkage and superior mechanical properties compared with other types of fibers.After that,a series of field tests were carried out to evaluate the effectiveness of EGC retrofitting layer on the enhancement of blast performance of typical elements.The tests include autoclaved aerated concrete(AAC)masonry walls subjected to vented gas explosion,reinforced AAC panels subjected to TNT explosion and plain concrete slabs subjected to contact explosion.It was found that EGC could effectively enhance the blast resistance of structural elements in different scenarios.For AAC masonry walls and panels,with the existence of EGC,the integrity of specimens could be maintained,and their deflections and damage were significantly reduced.For plain concrete slabs,the EGC overlay could reduce the diameter and depth of the crater and spallation of specimens.

Structural Design and Analysis of a Booster Arm Made of a Carbon Fiber Reinforced Epoxy Composite Material

An analysis of a booster arm made of a carbon fiber reinforced epoxy composite material is conducted by means of a finite element analysis method.The mechanical properties are also determined through stretching and compression performance tests.It is found that the surface treatment of the fibers causes the silane coupling agent to undergo a chemical reaction on the surface of the glass fiber.The used material succeeds in producing significant vibrations damping(vibration attenuation effect is superior to that obtained with conventional alloy materials).

Experimental Research on Behavior of Composite Material Projectile Penetrating Concrete Target

Projectile made of carbon fiber composite material shell and metal warhead penetrates concrete target at speeds of 336,m/s,447,m/s and 517,m/s.The angles between the perpendicu-lar of target surface and projectile axis are 0°and 30°.The thickness of concrete target is 200,mm and the compression strength is 30 MPa.The experimental results indicate that the strength of composite material structure is high.Composite projectile can go through concrete tar-get without fiber segregation and breakage.The percent fill is 18.5% in the composite material projectile.It is about twice as that of metal projectile,if the density of metal is taken as 7.8,g/cm3.Comparing with metal projectile,low-density,high-strength composite material can lessen projec-tile weight,improve charge-weight ratio of detonator and enhance destructive powder.

One-pot synthesis of Sb-Fe-carbon-fiber composites with in situ catalytic growth of carbon fibers

A Sb-Fe-carbon-fiber （CF） composite was prepared by a chemical vapor deposition （CVD） method with in situ growth of CFs us- ing Sb203/Fe2O3 as the precursor and acetylene （C2H2） as the carbon source. The Sb-Fe-CF composite was characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FESEM） and transmission electron microscopy （TEM）, and its electrochemical per- formance was investigated by galvanostatic charge-discharge cycling and electrochemical impedance spectroscopy. The Sb-Fe-CF composite shows a better cycling stability than the Sb-amorphous-carbon composite prepared by the same CVD method but using Sb2O3 as the precur- sor. Improvements in cycling stability of the Sb-Fe-CF composite can be attributed to the formation of three-dimensional network structure by CFs, which can connect Sb particles firmly. In addition, the CF layer can buffer the volume change effectively.

Fe_(2)O_(3)-MWNTs Composite with Reinforced Concrete Structure as High-performance Anode Material for Lithium-ion Batteries

A Fe_(2)O_(3)-MWNTs(multi-walled carbon nanotubes)composite with a reinforced concrete structure was fabricated employing a two-step method which involves a sol-gel process followed by high-temperature in situ sintering.This Fe_(2)O_(3)-MWNTs composite,intended to be used as an anode material for lithium-ion batteries,maintained a reversible capacity as high as 896.3 mA·h/g after 100 cycles at a current density of 100 mA/g and the initial coulombic efficiency reached 75.5%.The rate capabilities of the Fe_(2)O_(3)-MWNTs composite,evaluated using the ratios of capacity at 100,200,500,1000,2000 and 100 mA/g after every 10 cycles,were determined to be 904.7,852.1,759.0,653.8,566.8 and 866.3 mA·h/g,respectively.Such a superior electrochemical performance of the Fe_(2)O_(3)-MWNTs composite is mainly attributed to the reinforced concrete construction,in which the MWNTs function as the skeleton and conductive network.Such a structure contributes to shortening the transport pathways for both Li+and electrons,enhancing conductivity and accommodating volume expansion during prolonged cycling.This Fe_(2)O_(3)-MWNTs composite with the designed structure is a promising anode material for high-performance lithium-ion batteries.

房屋建筑工程中钢管混凝土的施工技术研究

针对房屋建筑工程中钢管混凝土的施工技术,研究提出了一种利用碳纤维增强基复合材料包裹受损区域的修复技术,以此提高钢管混凝土柱的承载能力。研究结果表明,该方法显著提高了构件的承载能力,修复后的构件承载力较修复前提高了14.8%。该技术不仅有效增强了受损构件的承载力,还显著提升了其安全性和耐久性。该研究为房屋建筑工程中钢管混凝土柱的施工和修复提供了新的技术方向,具有一定的经济价值。

Experimental study and analysis on fatigue stiffness of RC beams strengthened with CFRP and steel plate

The objective of this work is to investigate the fatigue behavior of reinforced concrete(RC) beams strengthened with externally bonded carbon fiber reinforced polymer(CFRP) and steel plate. An experimental investigation and theoretical analysis were made on the law of deflection development and stiffness degradation, as well as the influence of fatigue load ranges. Test results indicate that the law of three-stage change under fatigue loading is followed by both midspan deflection and permanent deflection, which also have positive correlation with fatigue load amplitude. Fatigue stiffness of composite strengthened beams degrades gradually with the increasing of number of cycles. Based on the experimental results, a theoretical model by effective moment of inertia method is developed for calculating the sectional stiffness of such composite strengthened beams under fatigue loading, and the calculated results are in good agreement with the experimental results.

碳纤维增强复合材料在航空航天领域的应用

碳纤维增强复合材料在航空航天领域广泛应用,涵盖飞机结构、发动机、航天器等方面。其在飞机结构中轻量、高强的特性提高了飞机性能,同时在发动机和航天器中的应用,如天线罩、次级结构件和热防护层,为提高航天器的稳定性和耐高温能力提供了先进材料解决方案。未来,高性能和多尺度复合材料将是发展的趋势,为航空航天领域带来更多创新。

CFRP加固RC梁力学性能试验研究及有限元分析

为了研究碳纤维增强复合材料(CFRP)对钢筋混凝土梁的加固效果,对6组钢筋混凝土梁的抗弯性能开展试验研究,在试验研究中重点考察了CFRP加固对RC梁受弯时力学性能的影响。结果表明:①经CFRP布加固后的RC梁相较于未加固的RC梁,开裂荷载增加47.4%,屈服荷载增加34.2%,极限荷载增加27.4%。②CFRP加固后,梁内纵筋屈服时最大裂缝宽度减小0.1 mm,梁破坏时最大裂缝宽度减小0.8 mm。③CFRP加固能较大程度提高梁的力学性能及梁的延性,改善梁的破坏过程。为了继续探究CFRP的最佳加固形式,通过ABAQUS有限元数值模型模拟未加固及不同加固形式作用下梁加载的受力全过程,模拟结果与试验结果基本吻合。结果表明:增加加固层数、加固层厚度及改变加固形式都能显著提高梁的承载力,其中四面环绕式及三面U形的加固形式加固效果最好,加固层数控制在3层内加固效果最佳。

混合结构机械臂的设计与仿真分析

为减轻金属机械臂的重量,以六自由度机器人的大臂为研究对象,结合三维编织碳纤维复合材料的成型工艺,设计机械臂结构,提出基于CFRP/QT(碳纤维增强复合材料/QT 500-7铸铁)混合结构的机械臂轻量化设计方法。采用有限元分析方法对混合结构机械臂进行静力学分析,得到满足强度及刚度要求下混合结构机械臂的设计方案。力学仿真结果表明,混合结构机械臂质量减少24%,混合结构机械臂机器人具有良好的运动性能,在J1关节处所需驱动力矩更小。

轴向荷载作用下碳纤维布约束损伤混凝土能量耗散试验研究

本文对碳纤维布约束损伤混凝土在轴向荷载作用下的力学性能开展试验研究。设计了混凝土损伤度、碳纤维布层数及碳纤维布缠绕角度三种变量,通过试验结果分析了三种变量对碳纤维布约束混凝土应力-应变曲线、峰值应力、耗能效果及机械损伤度的影响规律。试验结果表明:相较于未损伤试件,0.4σm(σm为未损伤混凝土试件单轴抗压强度)、0.5σm、0.6σm、0.7σm应力幅值损伤下素混凝土损伤度均值分别为7.24%、14.86%、25.31%、36.66%,损伤度与损伤应力幅值间指数函数呈现良好的正相关。碳纤维布的约束作用增强试件峰值应力及延性,0.4σm损伤应力作用后,相较于未粘贴碳纤维布试件,粘贴1,2,3层碳纤维布试件峰值应力增幅分别为34.99%、55.16%、64.42%,碳纤维布粘贴层数与峰值应力间指数函数呈负相关,过量的纤维布使试件应力增幅不再明显。碳纤维布缠绕角度的增大使试件单位体积耗散能线性降低,缠绕角度的增大降低了荷载作用下试件的承载效果。应力损伤幅值的增大使试件机械损伤度降低,碳纤维布层数的增加使试件机械损伤度增加,纤维布的约束保护作用极大提升了试件的耗能效果。

多元算法融合模型的CFRP约束型钢混凝土柱承载力预测

为准确预测多影响因素下碳纤维增强复合材料(CFRP)约束型钢混凝土柱(SRCC)的轴压承载力,提出了一种基于随机森林(RF)、分类提升(Catboost)、极端梯度提升(XGBoost)、梯度提升回归树(GBRT)的多元算法融合预测模型。首先采用合成少数类过采样技术(SMOTE)算法对原始数据集进行扩充,开展了10种传统机器学习和集成学习模型试验,筛选出决定系数R2均大于0.92的RF、Catboost、XGBoost、GBRT的4种集成学习模型,用随机搜索优化其超参数,然后融合形成了RF-Catboost-XGBoost-GBRT预测模型,对CFRP约束SRCC的承载力进行预测。结果表明,两种数据集下RF-Catboost-XGBoost-GBRT模型的预测性能最好,原始数据集经SMOTE算法处理后,5种预测模型R2平均提高20.43%,其中RF-Catboost-XGBoost-GBRT模型的R2达到了0.942,预测值误差均在±10%以内。

复合混凝土材料及不同蜂窝夹芯结构的力学性能综述

为全面开展复合混凝土材料制备蜂窝夹芯板的研究,综述了国内外关于稻草秸秆纤维与纳米二氧化硅复合混凝土材料及蜂窝夹芯结构的研究,分析了各种检测方法,概述了稻草秸秆纤维与纳米二氧化硅复合混凝土材料及不同蜂窝夹芯结构的力学性能,对复合混凝土材料蜂窝夹芯板研究及应用趋势进行总结。

碳纤维复合材料片材与混凝土粘结界面的力学性能研究进展

针对该粘结界面的力学性能,对国内外相关研究进行归纳对比,总结了静力与疲劳荷载作用下界面的剥离破坏模式,归纳了界面有效粘结长度的计算公式,研究了界面疲劳剥离的开展模式与预测方法。最后,对界面剥离与被加固构件整体受力性能之间的耦合关系提出了进一步研究的建议。

船用碳纤维夹芯复合材料防火隔热结构设计与验证

根据多晶莫来石纤维、金属碰钉和碳纤维双轴向织物的材料特性,进行船用碳纤维夹芯复合材料防火隔热结构设计。在完成材料选择和试样制备后,对设计的船用碳纤维夹芯复合材料防火隔热结构进行耐火试验验证。试验结果表明,试样的完整性和隔热性均合格。

基于桥梁改造的新旧混凝土结构粘接加固复材改性研究

试验制备了一种聚乙烯醇(PVA)纤维水泥基复合材料(ECC),并将该材料与碳纤维布(CFRP)结合,对新旧钢筋混凝土梁进行复合加固处理,研究材料性能。结果表明,制备的ECC材料具备较好综合性能,粘接效果和抗裂效果良好,可以与CFRP结合,对桥梁混凝土进行粘接加固;相对于普通钢筋混凝土梁,经过ECC/CFRP复合加固后,钢筋混凝土梁的刚度提高,极限荷载明显提升;随着ECC/CFRP复合加固层厚度的增加、CFRP长度的增加,粘接加固效果越好,极限荷载最大值分别达到30.17、29.73 kN。ECC/CFRP复合加固可以提高旧危桥梁混凝土的性能,粘接加固效果较好。

碳纤维复合材料在轨道交通领域的研究方法与应用发展

文章对碳纤维复合材料在轨道交通领域的理论研究方法模型及应用研究现状展开综述,首先总结了当前常用的复合材料特性研究方法,之后针对轨道交通车辆的重要构件阐述了碳纤维复合材料的应用情况和相关研究,最后指出想要实现规模化应用目前仍存在的问题和未来的发展方向。研究结果表明:碳纤维复合材料的研究方法多以理论研究为主,对于轨道交通的大型结构件多采用有限元仿真为主;目前已有的应用集中于车辆的司机室外罩、车身车体、转向架构架等,且均已证实其在力学性能、结构强度等方面符合设计和运行要求;未来应建立轨道交通行业的专用标准体系、优化结构件设计理念和装配工艺、发展原材料产业链并完善生产线、研发配套的运维检修设备。

碳纤维复合材料箱体结构设计

在结构拓扑优化理论基础上对某部件的箱体进行碳纤维复合材料结构设计,通过拓扑优化得到箱体结构的筋、肋布局,建立碳纤维复合材料的结构模型,并对此进行厚度与角度优化,最终得到碳纤维复合材料箱型结构。

碳纤维粘贴材料在桥梁结构加固中的应用研究

针对当前使用的有关桥梁结构加固方法存在的问题,提出了在桥梁结构加固中粘贴碳纤维材料的应用方法。通过分析任意截面上的法向应力分量、剪应力分量,结合莫尔-库伦强度理论,判断莫尔圆与抗剪强度线的相对位置判断相交点的状态。根据莫尔圆与抗剪强度线几何关系,确定极限平衡条件,由此确定贴碳纤维材料的单位面积用量。以X大桥的K225+150-K225+500断面为研究对象,通过工程实例加固效果可知,所研究方法分析的K225+150-K225+500断面加固容许安全系数均在容许范围内,且最大安全系数为0.98,具有安全加固效果。

电动汽车电池箱体结构轻量化设计

新能源汽车电池箱的质量与续航里程密切相关。为了在保持原有电池箱安全性能的前提下实现新能源汽车电池箱轻量化,进一步增加纯电动汽车续航里程,将电池箱在Solidworks中建模并导入Hypermesh、Abaqus中建立有限元仿真模型,对电池箱进行静强度分析和模态分析。根据仿真结果,对电池箱体使用密度更小,比强度、比刚度更高的碳纤维复合材料T300/5222替换原金属材料以及设计底部支撑支架,并对新材料电池箱进行复杂工况以及挤压仿真分析。仿真结果表明,电池箱静强度得到提升,一阶模态频率提升至31.79 Hz,大于外界激励频率27.78 Hz,解决了原电池箱由于一阶模态频率过低引起的共振问题,电池箱整体质量降低了29.1 kg,减重52.8%。在增强电池箱的强度、刚度和安全性能的基础上,降低了电池箱体的质量,实现了轻量化目标。对电池箱体结构改进和轻量化研究具有参考意义。