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.

Preparation and Mechanical Properties of UV⁃Assisted Filament Winding Glass Fiber Reinforced Polymer⁃Matrix Composite

This paper studied the preparation and mechanical properties of glass fiber reinforced polymer-matrix composite rings prepared by filament winding assisted by ultraviolet(UV)curing.A ray-tracing method was used to calculate the penetration ability of UV light in the resin casting,and then a typical composite ring with dual⁃curing characteristics was prepared by UV-assisted curing.The effects of winding speed and thermal initiator concentration on the distribution of fiber fraction and mechanical properties were studied.Microscopic morphology was used for the observation of the differences in fiber volume fraction.Mechanical properties tests and scanning electron micrographs were performed to investigate the failure and damage mechanisms of the composite ring samples.The ray tracing results indicate that the UV light can pass through a single yarn thickness and the energy transmitted is sufficient to cure the back side quickly.The experimental results show that the mechanical properties of the composite ring prepared in this paper are comparable to those of the heat-cured samples,which is sufficient to meet the requirements of the flywheel.

Static and Fatigue Behavior of Hybrid Bonded/Bolted Glass Fiber Reinforced Polymer Joints Under Tensile Loading

This paper presents the static and fatigue tests of hybrid(bonded/bolted)glass fiber reinforced polymer(GFRP)joints.Nine specimens of single-lap hybrid GFRP joints have been fabricated to study the static and fatigue behaviors in the experimental campaign.The static tests of uniaxial tension loading are first conducted,from which the static ultimate bearing capacities of the joints are obtained.High-cycle fatigue tests are subsequently carried out so that the fatigue failure mode,fatigue life,and stiffness degradation of joints can be obtained.The measuring techniques including acoustic emission monitoring and three-dimensional digital image correlation have been employed in the tests to record the damage development process.The results revealed that the static strength and fatigue behavior of such thick hybrid GFRP joints were controlled by the bolted connections.The four stages of fatigue failure process are obtained from tests and acoustic emission signals analysis:cumulative damage of adhesive layer,damage of the adhesive layer,cumulative damage of GFRP plate,and damage of GFRP plate.The fatigue life and stiffness degradation can be improved by more bolts.The S-N(fatigue stress versus life)curves for the fatigue design of the single-lap hybrid GFRP joints under uniaxial tension loading are also proposed.

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。

桥梁结构中E-GFRP单向板徐变性能与双尺度均匀化数值评估

由于玻璃纤维增强复合材料(GFRP)组分材料中的树脂属于高分子材料,桥梁工程界对GFRP结构的徐变性能十分担忧,阻碍了其推广应用。该文聚焦于桥梁工程E型玻璃纤维增强复合材料(E-GFRP)单向板,基于双尺度均匀化数值模拟方法,从纤维和树脂的徐变性能评估了E-GFRP单向板的徐变性能,并与试验结果进行比较验证了预测结果的准确性。在此基础上,分析了应力水平、纤维体积率及持荷形式对E-GFRP单层板徐变性能的影响,结果表明,应力水平越高、纤维体积率越小,单层板的徐变粘滞应变越大。在此基础上,提出了不同纤维体积率下E-GFRP单层板粘滞应变模型,准确表述了应力水平、持荷时间和徐变应变之间的关系。最后,提出了E-GFRP单层板徐变断裂时间预测公式,可为E-GFRP结构的长期性能预测提供参考。

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.

GFRP约束ECC短柱偏压试验研究

纤维增强复合材料(Fiber Reinforced Polymer,FRP)约束工程纤维增强水泥基复合材料(Engineered Fiber Reinforced Cementitious Composites,ECC)轴压柱可显著提高其承载能力和延性,但偏压作用下FRP约束ECC柱的性能提升程度和作用机理有待研究。基于此,以偏心距(0、10、30、50 mm)和FRP层数(0、2、4层)为试验变量,对玻璃纤维增强复合材料(Glass Fiber Reinforced Polymer,GFRP)约束ECC短柱展开了竖向加载试验,并对试验结果进行了分析。研究结果表明:小偏心破坏时受压侧FRP断裂、混凝土被压碎,大偏心破坏时受拉侧FRP撕裂与混凝土横向裂缝近乎同时出现。轴压作用下,轴向变形和抗压强度显著增大;偏压作用下,抗压承载力随着偏心距的增大而减小,而极限位移无明显变化规律。此外,承载力和延性都随着FRP层数的增加而增大。

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。

Bond Mechanical Properties of Glass Fiber Reinforced Polymer Anti-Floating Anchor in Concrete Baseplate

Combined with fiber Bragg grating(FBG)sensing technology,four glass fiber reinforced polymer(GFRP)anti-floating anchors and four steel anti-floating anchors were tested for on-site destructive failure to investigate the anchoring performance and the bonding characteristics between GFRP anti-floating anchor and concrete floor.The test results show that bending GFRP anchor will be broken at the common boundary between vertical anchorage section and bending section during the pullout process,and the spring-back load provided by the rupture contributes to a decrease of bearing capacity and an inflection point on the load-slip curve.The loaddisplacement curve of the straight anchor GFRP anti-floating anchor is smoother and has better predictability than the same type of steel anchor.Additionally,different forms of GFRP anti-floating bolt have different bondslip constitutive relations.By introducing the sliding-slip correction factor of bending bolt,constitutive models describing the rising-section of sliding-slip relation of bending and straight-anchored GFRP anti-floating bolt are established respectively.The model can fit the test results rightly.

Mechanical behavior of concrete filled glass fiber reinforced polymer-steel tube under cyclic loading

The mechanical behavior of concrete-filled glass fiber reinforced polymer(GFRP)-steel tube structures under combined seismic loading is investigated in this study. Four same-sized specimens with different GFRP layout modes were tested by a quasi-static test system. Finite element analysis(FEA) was also undertaken and the results were presented. Results of the numerical simulation compared well with those from experimental tests. Parametric analysis was conducted by using the FE models to evaluate the effects of GFRP thickness, axial compression rate, and cross sectional steel ratio. The experimental and numerical results show that the technique of GFRP strengthening is effective in improving the seismic performance of traditional concrete-filled steel tubes, with variations related to different GFRP layout modes.

Experimental Study of the Shear Capacity of Glass Fiber Reinforced Polymer Reinforced Concrete Beam with Circular Cross Section

In order to research the shear behavior of glass fiber reinforced polymer (GFRP) reinforced concrete beam with circular cross section, based on the test results of 36 concrete beams subjected to four-point loading up to failure, the shear capacity and mechanical properties of deformation were analyzed comparatively between GFRP reinforced concrete (GFRP-RC) beams and steel reinforced concrete (steel-RC) beams. Furthermore, influencing factors of shear capacity of GFRP-RC beam with circular cross section were also investigated. The test results indicate that the failure modes of GFRP-RC and steel-RC beams are the same, but the crack patterns are slightly different. And, the shear capacity of GFRP-RC beam firstly increases with the reduction of shear span ratio, and then decreases. In addition, it was found that the influencing coefficient of GFRP on concrete increases with shear span ratio reducing.

基于数据库的玻璃纤维增强复合材料箍筋弯拉强度计算方法

玻璃纤维增强复合材料箍筋弯拉强度试验主要研究弯折半径与直径之比对弯拉强度的影响,直线段抗拉强度对弯拉强度的影响研究较少。本文基于ACI 440.3R-12中B.5试验方法,开展3组(9个弯拉试件)不同直线段抗拉强度的玻璃纤维增强复合材料箍筋弯拉强度试验研究。3组试件直线段抗拉强度分别为530(A组)、850(B组)和1100 MPa(C组),弯折半径与箍筋直径之比均为3。试验结果表明:所有试件均发生玻璃纤维增强复合材料箍筋弯折段被拉断的破坏模式;A、B、C组试件弯拉强度分别为325、445和530 MPa。本文系统收集了国内外已有93个弯拉试件,并结合本文9个弯拉试件建立了玻璃纤维增强复合材料箍筋弯拉强度试验数据库。基于数据库统计分析,提出了保证率不小于95%的玻璃纤维增强复合材料箍筋弯拉强度计算方法。

GFRP锚杆拉拔时效模型研究

近年来GFRP锚杆因耐腐蚀性好、强度重量比高等优点而逐渐应用于边坡等岩土体的支护,但其时效力学特性却对加固的岩土体造成了潜在的威胁。本文在分析GFRP锚杆拉拔机理的基础上,引入Merchant流变模型,建立了反映GFRP锚杆拉拔时效特性的黏弹性流变模型。根据推导出的控制方程,运用有限差分方法得到了锚杆轴力、剪应力和位移沿杆长的分布,及其随时间变化的规律。在该模型的基础上,对影响GFRP锚杆拉拔时效特性的主要因素进行了一系列的参数研究,并得到了一些关于GFRP锚杆加固机理的结论。

GFRP复合材料加固带壁柱砖墙抗震性能试验研究

对玻璃纤维复合材料(Glass Fiber Reinforced Polymer,GFRP)加固带壁柱砖墙抗震性能进行试验研究。通过1片未加固带壁柱砖墙和8片GFRP加固带壁柱砖墙在低周往复荷载作用下的抗震性能试验,阐述了各试件的破坏特征;研究GFRP加固前后墙体的滞回特性、刚度及退化特性、变形性能、耗能性能等变化规律,以及加固方式、加固量和“对拉”锚固措施对加固效果的影响。研究结果表明:加固方式对墙体的刚度退化性能和变形性能影响不大,但对墙体的耗能性能影响较明显;按照本文提出的加固方式粘贴GFRP能够有效地提高墙体的极限荷载、减缓墙体的刚度退化、增强其变形能力和耗能能力;同时考虑采用混合加固方式、增大加固量、采用锚固措施三因素时,墙体的抗震性能较好。

GFRP复合材料与砖界面粘结性能的数值模拟

纤维复合材料(Fiber Reinforced Polymer,FRP)加固砌体结构剥离破坏是一种常见的破坏形式。对玻璃纤维复合材料(GFRP)和砖粘结界面进行数值模拟,用Solid65单元和Shell41单元分别模拟砖和GFRP,采用接触单元的方法,用"接触对"将砖实体单元和GFRP单元连接在一起,研究粘结界面的应力、应变分布特点和破坏过程。分析结果表明用有限元模拟分析粘结界面应力状态具有一定的可行性。

GFRP土钉拉拔特性研究

由于传统土钉材料存在易腐蚀、耐久性差等缺点,近年来以GFRP为代表的新型土钉材料得到了高度重视。针对GFRP土钉受力特性,运用双曲线模型描述其在拉拔过程中剪应力–剪应变关系,采用数值方法求解拉拔控制方程,从而确定轴力、剪应力及位移沿钉长的分布。同时,通过室内GFRP模型土钉的拉拔试验,验证了该模型预测结果的准确性。在此基础上,对土钉直径、土–钉界面抗剪强度、土–钉模量比等参数进行了参数分析,并针对GFRP土钉容许拉拔力的确定提出了按位移控制的思路。

基于递归定量分析与多核学习支持向量机的玻璃纤维增强复合材料缺陷识别技术

为了提高玻璃纤维增强复合材料(Glass Fiber Reinforced Polymer,GFRP)超声检测中缺陷识别技术的准确性,提出基于递归定量分析(Recurrence Quantitative Analysis,RQA)与多核学习支持向量机(MKLSVM)相结合的检测模型,以提高检测GFRP中不同类型缺陷的能力。结果表明,该模型能够准确识别GFRP中的分层缺陷与夹杂缺陷,检测识别率达到92.92%,并且与基于离散小波变换(Discrete Wavelet Transform,DWT)和经验模态分解(Empirical Mode Decomposition,EMD)的MKLSVM检测模型的识别率相比,所提出的检测模型的识别率分别提高了7.5%和3.75%。

双跨连续GFRP-混凝土组合板的试验研究

为研究GFRP-混凝土组合板的受力性能,对3块GFRP-混凝土组合连续板进行了静载试验.3块组合板分别通过环氧树脂胶或剪力栓钉与下部型钢支座连接.试验结果表明:所有组合板的最终破坏形态均表现为加载垫块处局部冲剪破坏;中支座处和边支座处没有出现荷载重分布现象,组合板表现出良好的空间受力性能及变形协调能力.然后,基于塑性极限理论,提出了一种GFRP-混凝土组合板极限承载力计算方法.预测值与试验值的比较结果表明,所提方法可以有效地预测GFRP-混凝土组合板的极限承载力.

基于微观分析的GFRP浸水老化弯曲性能研究

本文开展了玻璃纤维增强复合材料(GFRP)在去离子水和Na Cl溶液中常温浸泡前后的质量、弯曲强度、弯曲模量、腐蚀深度变化的研究,并基于微观分析研究了GFRP片材在去离子水和Na Cl溶液中浸泡后的弯曲性能。研究结果表明,GFRP置于不同的溶液中,吸水率均呈现先上升后趋于平稳的趋势;GFRP在去离子水环境中的吸水率约为在Na Cl溶液中的2倍;GFRP置于去离子水和Na Cl溶液中120d后,片材的弯曲强度和模量均发生先上升后下降的变化;相同浸泡时间下,片材在去离子水中的腐蚀深度大于在Na Cl溶液中的腐蚀深度。