树脂基复合材料用增强材料研究进展

介绍树脂基复合材料用增强材料的新进展，分析了增强材料的结构与性能。     

纤维增强CBT树脂基复合材料研究进展

介绍了环形对苯二甲酸丁二醇酯（CBT）的性能特点及其应用,综述了纤维增强CBT树脂基复合材料的国内外研究现状,包括制备工艺、力学性能以及应用等,并对其在复合材料领域的发展进行了总结与展望。     

基于激光超声二次谐波技术检测纤维增强树脂复合材料加固混凝土结构剥离损伤

纤维增强树脂(FRP)复合材料加固混凝土结构的早期剥离损伤往往趋向于闭合状态,传统线性超声技术对这种剥离损伤不敏感.本文提出了基于连续激光激发窄带超声波技术结合非线性超声二次谐波法检测FRP复合材料加固混凝土剥离损伤的方法,该方法通过强度调制激光技术在加固结构的表面激励窄带超声表面波,在超声波的扰动下,依据弹簧模型的接...     

湿热环境下纤维增强树脂基复合材料疲劳性能研究进展

纤维增强树脂基复合材料在航空航天航海等领域受到广泛应用,湿热环境下长时间循环载荷的作用是复合材料结构设计必须面对的问题,对复合材料结构的强度和刚度有显著的影响.本文首先简要介绍复合材料的水分扩散机理,阐述湿热环境对其力学性能的退化机制.然后着重介绍了湿热环境下纤维增强树脂基复合材料疲劳性能的研究进展,梳理了影响纤维增强...     

纤维增强树脂复合材料约束超高性能混凝土轴压性能的细观数值模拟

利用LS-DYNA有限元分析软件建立纤维增强树脂(FRP)复合材料约束超高性能混凝土(UHPC)圆柱细观有限元模型,以研究其单轴受压性能。通过已有试验数据验证了模型的有效性,并建立了能准确反映FRP复合材料约束作用的K&C模型的剪切膨胀参数预测公式。在此基础上进行参数分析,研究FRP复合材料厚度、纤维缠绕角度和钢纤维掺量的影响。结果表明,本文模型不仅能模拟随机分布钢纤维对试件应力分布的影响,且能较准确反映FRP复合材料约束作用对核心UHPC强度和延性的提高效果。模型在轴压作用下的破坏模式和应力-应变曲线与试验结果基本一致。参数分析表明,随FRP复合材料厚度或纤维缠绕角度的增大,试件极限承载力和延性均增大,而增大钢纤维掺量虽可限制核心UHPC斜裂缝的开展,但对试件强度和延性影响较小。      

纤维增强树脂基复合材料拼接结构拉伸性能

为了解拼接结构的力学特性,更好地设计高强度的拼接结构,测试了三种含拼接结构的单向碳纤维增强环氧树脂基(CF/EP)层合板复合材料的拉伸性能,通过监测结构在拉伸过程中的形态分析其破坏特点,并利用有限元软件对不同拼接结构的拉伸过程进行模拟,分析拼接结构受拉过程中的受力特点。所有材料均采用真空辅助灌注工艺(VARTM)获得。结果表明,拼接结构的引入大大降低了CF/EP材料的拉伸强度;由于拼接位置产生明显的应力集中,结构破坏从拼接位置开始,最终破坏模式为层间破坏;拼接位置处的剪切应力和侧向拉伸应力是结构发生初始破坏的主要因素;为了尽可能避免产生拼接位置处的剪切应力和侧向拉伸应力以提高结构强度,应尽可能设计为对称结构。     

FRP筋预应力混凝土梁抗弯性能研究进展

FRP筋预应力混凝土结构已成为国内外工程领域研究的重点，文章分别介绍了国内外体内有粘结、体内无粘结和体外无粘结FRP筋预应力混凝土梁抗弯性能研究的主要成果，并对今后拟开展的研究工作提出了建议。     

A short review on basalt fiber reinforced polymer composites

A recent increase in the use of ecofriendly, natural fibers as reinforcement for the fabrication of lightweight, low cost polymer composites can be seen globally. One such material of interest currently being extensively used is basalt fiber, which is cost-effective and offers exceptional properties over glass fibers. The prominent advantages of these composites include high specific mechano-physico-chemical properties, biodegradability, and non-abrasive qualities to name a few. This article presents a short review on basalt fibers used as a reinforcement material for composites and discusses them as an alternative to the use of glass fibers. The paper also discusses the basics of basalt chemistry and its classification. Apart from this, an attempt to showcase the increasing trend in research publications and activity in the area of basalt fibers is also covered. Further sections discuss the improvement in mechanical, thermal and chemical resistant properties achieved for applications in specific industries.     

Evaluation of prestressed basalt fiber and hybrid fiber reinforced polymer tendons under marine environment

This paper studies the degradation of the tensile properties of prestressed basalt fiber-reinforced polymer (BFRP) and hybrid FRP tendons in a marine environment. Two levels of prestressing toward typical prestressing applications were applied in the experiment. The variations of tensile strength, elastic modulus and the relevant coefficient of variation (CV) were first investigated. The effect of prestressing on tensile property degradation was discussed. The characteristics of prestressed hybrid FRP tendons in a marine environment simulated by a salt solution were clarified. Moreover, a prediction model of BFRP tendons with different levels of prestressing in a marine environment was proposed. The results show that the BFRP tendons’ superior resistance to salt corrosion and the degradation rate of their tensile strength is nonlinearly proportional to the prestressing ratios, whereas the elastic modulus remains constant regardless the prestressing ratio and aging duration. Although prestressing on BFRP tendons accelerates degradation, it can still lower the variation of the strength of the BFRP tendon. Hybridization can lower the degradation rate of basalt and carbon FRP (B/CFRP) without prestressing, whereas basalt and steel-wire FRP (B/SFRP) exhibit much faster degradation due to the internal corrosive steel wires. The model regression by the Napierian logarithm equation well represents the degradation trend of BFRP tendons under different levels of prestressing.     

Kenaf fiber reinforced composites: A review

The development of high-performance engineering products made from natural resources is increasing worldwide, due to renewable and environmental issues. Among the many different types of natural resources, kenaf plants have been extensively exploited over the past few years. Therefore, this paper presents an overview of the developments made in the area of kenaf fiber reinforced composites, in terms of their market, manufacturing methods, and overall properties. Several critical issues and suggestions for future work are discussed, which underscore the roles of material scientists and manufacturing engineers, for the bright future of this new “green” material through value addition to enhance its use.     

Analysis of reinforced concrete columns retrofitted with fiber reinforced polymer lamina

Fiber reinforced polymer (FRP) lamina have been used widely in the last decade to enhance strength and deformation capacity of deficient reinforced concrete (RC) columns. Seismic assessment and retrofit of existing columns in buildings and bridge piers necessitate accurate prediction of the available deformation capacity. In this study, a new analytical model is proposed to represent potential plastic hinge regions of RC columns prior to and after FRP retrofit. A recently developed variable confined concrete representation is employed within the framework of fiber-discretized frame elements to model the compression zone of the FRP-confined region. Confinement distribution within this region is included through the use of a bond model, whereas the effect of lap splices are considered using an effective steel strain concept. Comparisons of analytical estimates with experimentally measured response show that the proposed model is capable of capturing essential features of the response such as strength degradation due to lap splice slippage, and failure due to FRP rupture. Furthermore, a detailed sensitivity study is conducted to determine the parameters whose uncertainty significantly affects the behavior. It is observed that, in estimating the response of existing deficient columns, parameters such as plastic hinge length, concrete strength and splice length are important sources of uncertainty. While for FRP-retrofitted columns, parameters such as jacket stiffness, dilatation strain at splice failure and yield strength of the reinforcing bars are more important sources of uncertainty.     

Fatigue behavior and modeling of short fiber reinforced polymer composites: A literature review

Applications of short fiber reinforced polymer composites (SFRPCs) have been rapidly increasing and most of the components made of these materials are subjected to cyclic loading. Therefore, their fatigue behavior and modeling have been of much interest in recent years. This literature review presents a broad review of the many factors influencing cyclic deformation, fatigue behavior, and damage development in SFRPCs. These include microstructural related effects as well as effects related to loading condition and their service environment. Microstructural related effects include those related to fiber length, content and orientation, surface treatment, and failure mechanisms. Cyclic deformation and softening, viscous characteristics, and dissipative response used to characterize and model their fatigue damage behavior and accumulation are discussed. The effects of stress concentrations and their gradient on fatigue behavior are also discussed, due to their significant influence. The effects related to the loading condition include mean stress effects which may be accompanied by cyclic creep, variable amplitude loading, and multiaxial stress effects. Since fatigue behavior is substantially influenced by the testing frequency with self-heating as the primary consequence of increased frequency, this effect is also investigated. Environmental effects considered include the effects of moisture content and temperature, as well as thermo-mechanical fatigue behavior. The effect of welded joints in manufactured components made of SFRPCs and fatigue analysis and life estimation techniques used for such components are also included.     

聚合物基天然植物纤维增强复合材料研究进展

综述了近几年来国内外在聚合物基天然植物纤维增强复合材料领域的最新研究进展,介绍了聚合物基天然植物纤维增强复合材料的增强纤维种类、树脂基体种类以及其他因素对复合材料性能的影响,并展望了这类复合材料的发展及应用前景。     

Creep behavior of basalt fiber reinforced polymer tendons for prestressing application

This paper investigates the creep behavior of newly developed basalt fiber reinforced polymer (BFRP) tendons for prestressing application. The creep strain to time relationship, creep rate and residual strength were experimentally studied and the relevant mechanism was elaborated. Furthermore, the creep rupture stress was predicted based on statistical analysis. The results show that the creep strain to time relationship of BFRP tendons depends highly on the stress level applied. The creep rate of BFRP tendons under low levels of stress remains in low and steady values. Meanwhile, the residual strength of BFRP after 1000 h of sustained load still reaches approximately 95% of its initial tensile strength and the corresponding coefficient of variation (CV) is much less than the original CV. For prestressing application, the creep rupture stress limit for BFRP tendons can be adopted up to 52% of its tensile strength according to the reliability based analysis.     

预应力CFRP筋-螺纹钢筋-型钢/混凝土偏拉构件抗震性能试验

为研究预应力碳纤维增强树脂复合材料(CFRP)筋-螺纹钢筋-型钢/混凝土(SRC)偏拉构件的抗震性能,对4根预应力CFRP筋-SRC偏拉构件、4根预应力螺纹钢筋-SRC偏拉构件和3根普通SRC受拉构件进行了低周反复荷载对比试验,试验参数包括偏心距、预应力张拉水平、竖向拉力、预应力筋类型.研究结果表明:所有构件的破坏形态...     

Experimental behaviour of existing precast prestressed reinforced concrete elements strengthened with cementitious composites

Strengthening of reinforced concrete (RC) members by means of fibre reinforced polymers (FRP) has gained increasing importance in the last few decades. On the other hand the necessity of skilled labour, high costs and particularly the weak response under high temperature conditions represent critical issues for the effective application of this technique. The use of fibre reinforced cementitious matrix (FRCM) composites applied to RC members seems to be a promising technique since it combines cost economy and high performance. Despite the fact that a number of experimental investigations on strengthening of RC elements by means of fibre reinforced polymers (FRP) composites are available in the literature, very little information is available about fibre reinforced cementitious matrix composite (FRCM). Hence, the use of cementitious composites in strengthening of RC structures is strongly limited by the lack of design models, guidelines, and recommendations and by the few available experimental investigations.This work aims to better understand the behaviour of FRCM strengthened RC full-scale elements through experimental tests on precast prestressed double-T beams. In addition to investigating the experimental behaviour of an innovative and promising strengthening system, a further element of novelty of the work is that the tested beams belong to an actual existing industrial building, since the few experimental tests available in the literature are mostly related to small-scale and cast-in-place RC elements.