A review on machinability of carbon fiber reinforced polymer(CFRP)and glass fiber reinforced polymer(GFRP)composite materials

Fiber reinforced polymer(FRP) composite materials are heterogeneous and anisotropic materials that do not exhibit plastic deformation. They have been used in a wide range of contemporary applications particularly in space and aviation,automotive,maritime and manufacturing of sports equipment. Carbon fiber reinforced polymer(CFRP) and glass fiber reinforced polymer(GFRP) composite materials,among other fiber reinforced materials,have been increasingly replacing conventional materials with their excellent strength and low specific weight properties. Their manufacturability in varying combinations with customized strength properties,also their high fatigue,toughness and high temperature wear and oxidation resistance capabilities render these materials an excellent choice in engineering applications.In the present review study,a literature survey was conducted on the machinability properties and related approaches for CFRP and GFRP composite materials. As in the machining of all anisotropic and heterogeneous materials,failure mechanisms were also reported in the machining of CFRP and GFRP materials with both conventional and modern manufacturing methods and the results of these studies were obtained by use of variance analysis(ANOVA),artificial neural networks(ANN) model,fuzzy inference system(FIS),harmony search(HS) algorithm,genetic algorithm(GA),Taguchi's optimization technique,multi-criteria optimization,analytical modeling,stress analysis,finite elements method(FEM),data analysis,and linear regression technique. Failure mechanisms and surface quality is discussed with the help of optical and scanning electron microscopy,and profilometry. ANOVA,GA,FEM,etc. are used to analyze and generate predictive models.

Application of Glass Fiber Reinforced Polymer Composite (GFRPC) Escape Pipeline in Tunnel

During the tunnel construction process,unfavorable geological conditionsare often encountered.Geological disasters such as collapse,roof fall,water inrush,gas explosion,etc.occur frequently,causing different degrees of property damage and casualties to the construction of the tunnel,seriously affecting harmony during construction.The domestic emergency hedging is mainly the use of 8-10mm steel coils,but the steel is heavy and not suitable for the frequent movement of tunnels.This paper introduces the new Glass Fiber Reinforced Polymer Composite(GFRPC)escape pipeline used in Chongqing Jiuyongyi Jinyunshan Tunnel,and compares the traditional steel coil parameters to provide reference for subsequent tunnel hedging measures.

Deriving Tensile Properties of Glass Fiber Reinforced Polymers (GFRP) Using Mechanics of Composite Materials

This work addresses the tensile properties of glass fiber reinforced polymers (GFRP) and investigates the different ways of estimating them without the cost associated with experimentation. This attempt is achieved through comparison between experimental results, derived in accordance with the ASTM standards, and results obtained using the mechanics of composite materials. The experimental results are also compared to results derived from work by other researchers in order to corroborate the findings regarding the correlation of tensile properties of the GFRP material and the fiber volume fraction.

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part I: Experimental study

This work is aimed at studying the strengthening of reinforced concrete (R. C.) beams using prestressed glass fi- ber-reinforced polymer (PGFRP). Carbon fiber-reinforced polymer (CFRP) has recently become popular for use as repair or rehabilitation material for deteriorated R. C. structures, but because CFRP material is very stiff, the difference in CFRP sheet and concrete material properties is not favorable for transferring the prestress from CFRP sheets to R. C. members. Glass fi- ber-reinforced polymer (GFRP) sheets with Modulus of Elasticity quite close to that of concrete was chosen in this study. The load-carrying capacities (ultimate loads) and the deflections of strengthened R. C. beams using GFRP and PGFRP sheets were tested and compared. T- and ⊥-shaped beams were used as the under-strengthened and over-strengthened beams. The GFRP sheets were prestressed to one-half their tensile capacities before being bonded to the T- and ⊥-shaped R. C. beams. The prestressed tension in the PGFRP sheets caused cambers in the R. C. beams without cracks on the tensile faces. The PGFRP sheets also enhanced the load-carrying capacity. The test results indicated that T-shaped beams with GFRP sheets increased in load-carrying capacity by 55% while the same beams with PGFRP sheets could increase load-carrying capacity by 100%. The ⊥-shaped beams with GFRP sheets could increase load-carrying capacity by 97% while the same beams with PGFRP sheets could increase the loading-carrying capacity by 117%. Under the same external loads, beams with GFRP sheets underwent larger deflections than beams with PGFRP sheets. While GFRP sheets strengthen R. C. beams, PGFRP sheets decrease the beams’ ductility, especially for the over-strengthened beams (⊥-shaped beams).

Strengthening reinforced concrete beams using prestressed glass fiber-reinforced polymer-Part II:Analytical study

Strengthening reinforced concrete (R. C.) beams using prestressed glass fiber-reinforced polymer (PGFRP) was studied experimentally as described in Part I of this paper (Huang et al., 2005). In that paper, R. C. beams, R. C. beams with GFRP (glass fiber-reinforced polymer) sheets, and R. C. beams with PGFRP sheets were tested in both under-strengthened and over-strengthened cases. The test results showed that the load-carrying capacities (ultimate loads) of the beams with GFRP sheets were greater than those of the beams without polymer sheets. The load-carrying capacities of beams with PGFRP sheets were greater than those of beams with GFRP sheets. The objective of this work is to develop an analytical method to compute all of these load-carrying capacities. This analytical method is independent of the experiments and based only on the traditional R. C. and P. C. (prestressed concrete) theory. The analytical results accorded with the test results. It is suggested that this analytical method be used for analyzing and designing R. C. beams strengthened using GFRP or PGFRP sheets.

双腹板工字型GFRP腰梁机械连接力学性能试验研究

为深入研究双腹板工字型玻璃纤维增强复合材料(glass fiber reinforced polymer,GFRP)腰梁机械连接节点的力学性能,基于无连接和有机械连接2种类型GFRP腰梁的静载试验,分析双腹板工字型GFRP腰梁在三分点对称加荷下的受力特征,明确2种类型腰梁的极限状态和破坏形式。结果表明:GFRP腰梁采用双腹板工字型截面型式,截面的最大应力为183 MPa,是GFRP腰梁纵向抗拉强度的62%,纵向抗压强度的73%(容许压缩承载力的205%),可以使GFRP材料强度得到充分发挥,腰梁稳定性能良好;GFRP腰梁容易出现局部破坏,首先在翼缘板处发生局部失稳,随即引起腹板产生屈曲破坏,翼缘和腹板连接处出现面层剥离和鼓起,腰梁连接处增设的缀板和螺栓可有效地抑制该局部破坏变形;采用螺栓机械连接并在连接处增设同材质缀板,可降低螺栓钻孔对梁体本身截面的削弱作用,使GFRP腰梁的刚度和极限承载能力分别提高17.9%和44.9%,是GFRP腰梁的合理连接方式。研究成果可为GFRP腰梁的推广应用提供参考和借鉴。

废旧GFRP回收及其增强沥青性能

玻璃纤维增强复合材料(glass fiber reinforced polymer,GFRP)因其优异的力学性能和耐腐蚀性而广泛应用于航空、船舶和风力发电等领域。GFRP的广泛使用导致大量废弃物的产生,对环境造成了巨大的危害,因此废旧GFRP的回收处理问题备受关注。将废旧环氧基GFRP和聚氨酯基GFRP破碎粉末(直径<0.075 mm)作为沥青增强材料,研究了其对沥青基本性能的影响,并对比了硅烷偶联剂对增强作用的影响。结果表明,2种GFRP粉末对沥青的增强作用并不明显,而使用硅烷偶联剂对GFRP粉末进行表面处理后,能够显著改善GFRP粉末与沥青间相互作用,并提高沥青的流变性能和表面自由能,降低玻璃化转变温度,其中硅烷偶联剂对环氧基GFRP的改善效果优于聚氨酯基GFRP。该文为废弃GFRP提供了一种相对有效且环保的物理回收方法,并为纤维增强复合材料(fiber reinforced polymer,FRP)的回收利用提供了新思路。

海水环境下GFRP筋与低碱混凝土界面黏结性能研究

针对GFRP筋在低碱耐腐蚀水泥基体环境下界面黏结性能的时变规律进行研究,采用中心拉拔试验方法测定了GFRP筋-矿渣硫铝酸盐水泥(G·SAC)混凝土、GFRP筋-硅酸盐水泥(OPC)混凝土在淡水和人工海水环境下养护30 d、90 d和180 d的界面黏结强度,并利用扫描电子显微镜(SEM)及pH计分析了孔溶液浸泡后GFRP筋微观结构的劣化过程及水泥基体孔溶液pH值的变化规律。结果表明:在淡水环境下,GFRP筋-G·SAC混凝土界面黏结强度随养护时间的增加而提高,但GFRP筋-OPC混凝土的黏结强度逐渐降低;在海水环境下,G·SAC基体碱度进一步降低,且海水对其强度发展有促进作用,GFRP筋-G·SAC混凝土在海水中的黏结强度较淡水增长较快。

Behaviour of Multiscale Progressive Damage for Different Matrix Glass Fiber Reinforced Plastics Bars

The damage formation and evolution of glass fiber reinforced plastics( GFRP) bar on mechanical properties were mainly evaluated by theoretical analysis and numerical calculations which lack of test basis of damage process. The two different matrices of unsaturated polyester and vinylester GFRP bars were selected to carry out a series of macro-mesoscopic physical and mechanical tests to analyze the tensile progressive damage process on a multiscale. The formation of apparent crack,the bonding of internal components as well as the strain change were all reflected damage evolution of GFRP bar,and a certain correlation existed between them. Wherein the matrix has an obvious impact on the damage of bar,the component stress transfer effect of vinylester bar is better than unsaturated polyester from crack propagation observation and scanning electron microscopy( SEM). The cyclic loading tests quantitatively reflect the difference of damage accumulation between different matrix bars,and the failure load of bars decreases nearly 10%.

交变载荷下绝缘拉杆用GFRP电树枝劣化特性

气体绝缘组合电器(gas insulated switchgear,GIS)现场调试或运行过程多次发生绝缘拉杆内部击穿问题,影响工程投运与设备可靠性,迫切需要探明故障机理。该文选取GIS断路器绝缘拉杆用玻璃纤维增强环氧树脂复合材料(glass fiber reinforced epoxy resin composite,GFRP)为研究对象,通过计算分、合闸下绝缘拉杆主应力分布特性,设置交变载荷下电树枝劣化实验条件,研究不同交变载荷对GFRP内电树枝生长特性影响规律。结果表明,相较于单一载荷,交变载荷条件下GFRP中电树枝生长速度加快,平均击穿时间降低,击穿概率增大。基于复合材料力学仿真发现交变载荷下GFRP内树脂-纤维界面处会出现较大的应力集中,局部应力损伤已达到失效的临界值。综上,交变载荷下绝缘拉杆纤维-树脂界面机械损伤与绝缘劣化交互演进是造成绝缘击穿的主要原因,也可作为试验考核与结构设计的改进依据。

Predicting the Fatigue Life in Steel and Glass Fiber Reinforced Plastics Using Damage Models

Three cumulative damage models are examined for the case of cyclic loading of AISI 6150 steel, S2 glass fibre/epoxy and E glass fibre/epoxy composites. The Palmgren-Miner, Broutman-Sahu and Hashin-Rotem models are compared to determine which of the three gives the most accurate estimation of the fatigue life of the materials tested. In addition, comparison of the fatigue life of the materials shows the superiority of AISI 6150 steel and S2 glass fibre/epoxy at lower mean stresses, and that of steel to the composites at higher mean stresses.

Thermo-Stamping Process of Glass and Carbon-Fibre Reinforced Polymer Composites

In this work, manufacturing tools for thermoplastic (TP) composites have been developed. The chosen process involves the stacking alternately of oriented dry fabrics and TP films and does not use semi-products in order to reduce material costs. This study was specifically directed towards optimizing the impregnation of continuous glass and carbon fibres reinforcing two TP amorphous matrices, the polyphenylsulfone (PPSU) and polyetherimide (PEI), to obtain semi-finished products employed for aeronautical structures. The impregnation quality of inter and intra-yarns is analyzed and validated by optical and scanning micrographic observations conducted with an optical and a Scanning Electron Microscopies (SEM), respectively. The study showed that besides the process parameters and porosity distribution in the core of warp yarns, the impregnation quality depends on the surface properties of constituents. Desizing treatment has been carried out to improve the wettability of fibres by the TP matrices.

有效高度对GFRP筋混凝土板冲切性能的影响

相比于传统的钢筋混凝土板,玻璃纤维增强聚合物(Glass fiber reinforced polymer,GFRP)筋混凝土板具有较高的耐腐蚀性能和较长的使用寿命,被广泛应用于水利工程和港口工程中。有效高度是影响GFRP筋混凝土板冲切承载力的重要因素,为量化其影响规律,完成了3块不同有效高度GFRP筋混凝土板的冲切试验。通过分析板的破坏形式、荷载—变形曲线、GFRP筋应变和混凝土应变,获得了GFRP筋混凝土板有效高度与冲切承载力之间的定量关系。试验结果表明:3块板均被冲切破坏,当有效高度分别增大23%和57%时,虽然抗冲切承载力分别对应提高51%和116%,但是GFRP筋应变和混凝土压应变反而比例减小;增大有效高度虽然一定程度上会减小板的变形,但不是决定极限挠度的唯一因素,在实际设计中应适当考虑有效高度的影响。

考虑二阶效应GFRP筋-钢筋混合配筋柱承载力计算方法

GFRP筋-钢筋混合配筋柱在土木工程中得到大量应用,进行GFRP筋-钢筋混合配筋混凝土柱偏心受压试验研究,分析配筋面积比、偏心距、混凝土强度以及混凝土保护层厚度等参数对承载力的影响.试件的破坏形式以受压区混凝土压碎破坏为主,受压区GFRP筋鼓曲破坏晚于混凝土破坏.GFRP筋-钢筋混合配筋柱承载力较高,大于GFRP筋混凝土柱.配筋面积比、偏心距、混凝土强度等因素对承载力影响较大,混凝土保护层厚度对承载力影响较小.由于GFRP筋弹性模量较小,使得结构的刚度降低,二阶变形增大,应考虑侧移产生的二次弯矩的影响,通过增大弯矩的方式进行偏压承载力计算.采用界限曲率理论的二阶效应计算方法,引进应变修正系数,基于试验数据得到混合配筋混凝土柱二阶效应弯矩增大系数计算方法.考虑二阶效应的混合配筋偏心受压混凝土柱的承载力的计算结果与试验结果吻合较好.研究结果为混合配筋混凝土柱的工程应用提供理论依据和参考.

Experimental Investigation on Flexural Performance of Masonry Walls Reinforced with GFRP

This paper presents the results of a test program for flexure reinforcing characteristics of gless fiber-rein forced polymer（GFRP） sheets bonded to masonry beams. A total of eight specimens subjected to monotonic four-point bending were tested up to failure. These specimens were constructed with two different bond patterns. Six of these specimens were reinforced by using GFRP sheets prior to testing, and the remaining two were not reinforced. The test results indicate a significant increase in both load-bearing capacity and ductile performance of the reinforced walls over the unreinforced ones.

混凝土环境中GFRP筋性能衰退的规律及机理

为了探究玻璃纤维增强复合材料(GFRP)筋在模拟和真实混凝土环境中性能衰退的规律及机理,设置了碱溶液(AS)和混凝土包裹GFRP筋后置于自来水中(CS)2种侵蚀环境,采用短梁剪切法分析了GFRP筋力学性能的衰退规律,并借助扫描电子显微镜、差示扫描量热法分析了GFRP筋的微观结构和玻璃化转变温度(T_(g)).结果表明:随着温度的升高,GFRP筋层间剪切强度衰退的速率加快;GFRP筋在60℃的AS中老化183 d后层间剪切强度保留了48.6%,T_(g)降低了9.2%,部分纤维与树脂脱黏,树脂出现孔洞;相同条件下CS中GFRP筋的层间剪切强度保留了61.4%,T_(g)降低了3.4%,纤维产生浅坑.基于Arrhenius方程建立了北京地区GFRP筋的性能预测模型.

Thermal Structure of Glass Fiber Reinforce Plastic Support Structure

The assembled form of thick-wall glass fiber reinforced plastics (GFRP) tube and 0Cr18Ni9 austenitic stainless steel pipes was designed as the radius thermal-insulating and load-supporting structure in cryogenic vessels. In order to study the thermal leakage and gap changes on the support structure, as well as radius temperature and stress distribution on GFRP tube, an experimental investigation has been taken. The results indicate that the support structure is proved to fit well as thermal-insulating and load-supporting part in cryo-genic vessels, furthermore has high security during cryogenic applications.

Seismic retrofitting of reinforced concrete frame structures using GFRP-tube-confined-concrete composite braces

This paper presents a new type of structural bracing intended for seismic retrofitting use in framed structures. This special composite brace, termed glass-fiber-reinforced-polymer （GFRP）-tube-confined-concrete composite brace, is comprised of concrete confined by a GFRP tube and an inner steel core for energy dissipation. Together with a contribution from the GFRP-tube confined concrete, the composite brace shows a substantially increased stiffness to control story drift, which is often a preferred feature in seismic retrofitting. An analysis model is established and implemented in a general finite element analysis program - OpenSees, for simulating the load-displacement behavior of the composite brace. Using this model, a parametric study of the hysteretic behavior （energy dissipation, stiffness, ductility and strength） of the composite brace was conducted under static cyclic loading and it was found that the area ratio of steel core to concrete has the greatest influence among all the parameters considered. To demonstrate the application of the composite brace in seismic retrofitting, a three-story nonductile reinforced concrete （RC） frame structure was retrofitted with the composite braces. Pushover analysis and nonlinear time-history analyses of the retrofitted RC frame structure was performed by employing a suite of 20 strong ground motion earthquake records. The analysis results show that the composite braces can effectively reduce the peak seismic responses of the RC frame structure without significantly increasing the base shear demand.

GFRP管约束竹筋细石混凝土组合杆力学性能试验

在当前绿色发展、“双碳”目标、科技创新的多元化发展中,工程建设行业要实现“双碳”目标,需寻找合适的钢制品替代产品。竹材作为重要工程结构用材应时而发,很有必要研发“以竹代钢”的创新技术和产品。依据实际工程需求,提出一种玻璃纤维复合材料(GFRP)管约束大截面竹筋细石混凝土组合(GBCC)构件,替代薄壁钢管用作围栏承载立杆。GBCC构件力学性能良好、制作工艺简单、产品绿色低碳。为研究GBCC的基本受力性能和不同材料的协同工作状态,进行了12根GBCC短杆轴压破坏试验、7根长杆轴压稳定试验和10根长杆抗弯试验,并研究了GBCC杆力学性能的影响规律。结果表明:GBCC短杆轴压胀裂压溃破坏,长杆轴压失稳,长杆抗弯脆性断裂破坏;GBCC材料构成、含竹率、细石混凝土密实性、试件受力方向、竹筋缺陷均影响GBCC杆的受力性能;含竹率20%左右的GBCC试件能够达到甚至超过薄壁空心钢管试件的承载力和变形能力;GBCC长杆具有很好的弹性变形能力,基于试验结果构建了GBCC长杆抗压失稳极限承载力公式。

内置GFRP管钢管混凝土柱延性非线性分析

利用ABAQUS有限元软件建立内套圆形GFRP(玻璃纤维增强复合材料)管圆钢管混凝土组合柱轴心受压和单向偏心受压模型,研究内套GFRP管厚度、纤维缠绕角度、外层钢管厚度和构件长径比4个因素对构件的位移延性系数的影响,从而得到对构件的延性影响。结果表明:轴压工况下,此组合柱的位移延性系数随着内套圆形GFRP管厚度、长径比的增加而变小,随着外层钢管厚度递增而变大,GFRP管纤维缠绕角度在75°~90°对构件位移延性系数提升效果最好;偏压工况下,内套GFRP管厚度对组合柱的位移延性系数影响规律不明显,外层钢管厚度对构件的位移延性系数前期影响不大,但对后期影响显著,随着构件的长径比增大,构件的位移延性系数呈非线性下降。