Damage performance of particles filled quasi-isotropic glass–fibre reinforced polyester resin composites

The purpose of this work was to determine the toughening mechanisms in interlayered quasi-isotropic glass–fibre reinforced polyester resin (GFRP) composites. Particles of polyethylene and aluminium tri-hydrate, Al(OH)3, were mixed with the polyester resin prior to laminating with woven E-glass-fibre cloth. Mode-I, mode-II, and impact tests were performed to determine critical strain energy-release rates (GIc and GIIc), absorbed energy and residual compressive strength for the laminates with and without particulate additions. Mode-I and mode-II delamination toughness were characterized using double cantilever beam (DCB) and end-notched flexure (ENF) specimens, respectively, and the delaminated surfaces of specimens were examined using scanning electron microscopy (SEM) to investigate the interlaminar morphology after fracture. The results indicate that the interlaminar toughness (GIc and GIIc), absorbed energy and residual compressive strength values of the GFRP composite increases with increase of particle content. The improved behaviour of particle containing GFRP is linked to stress-concentration induced plastic deformation and crack bridging. Polyethylene particles increase the toughness of the matrix material, which results in composites with higher values of mode-I, mode-II and impact than the composites with aluminium tri-hydrate particles. © 1998 Chapman & Hall     

Field and laboratory performance of a rectangular shaped glass fiber reinforced polymer deck

Fiber reinforced polymer (FRP) composites have been favorably noticed as state-of-the art construction materials, but sufficient material and structural data about FRP applications are not available. This study was intended to evaluate the applications and safety of FRP deck systems, which are developed by laboratory testing (static and fatigue tests), field application and testing of glass fiber reinforced polymer (GFRP) deck systems made of glass fiber and vinyl ester resin. The results show that the developed FRP deck systems have the expected strength and stiffness to replace the existing systems. FRP deck systems can effectively shorten the construction time and reduce the equipment required. In addition, it is determined that there is a need to evaluate the long-term structural behavior and durability of FRP deck systems in order to obtain comprehensive data for preparing the future design, manufacturing and construction materials.     

Evaluation of mechanical and thermal properties of banana–flax based natural fibre composite

Hybrid materials of any kind are the keynote for today’s demands. This paper deals with one of such hybrid composite made of natural fibres namely, banana and flax fibres. The structural build-up is such that one layer of banana fibre is sandwiched between two layers of flax fibres by hand layup method with a volume fraction of 40% using Epoxy resin and HY951 hardener. Glass fibre reinforcement polymer (GFRP) is used for lamination on both sides. This lamination also increases the overall mechanical properties along with better surface properties. The properties of this hybrid composite are determined by testing its tensile, impact, and flexural loads using a Universal testing machine. Thermal properties are analysed and hybrid composites of flax and banana with GFRP have better thermal stability and flame resistance over flax, banana with GFRP single fibre hybrid composites. Morphological analysis is done using Scanning Electron Microscope (SEM). The result of test shows that hybrid composite has far better properties than single fibre glass reinforced composite under impact and flexural loads. However it is found that the hybrid composite have better strength as compared to single fibre composites.     

圆弧形单向纤维增强树脂复合材料的I型层间断裂韧性测试及分析

层合板的I型层间断裂韧性的测量方法通常为单向纤维增强树脂复合材料的末端切口(End notched flexure, ENF)试样的双悬臂梁(Double cantilever beam, DCB)试验。为了得到带有弧度的层合复合材料结构的I型层间断裂韧性,对圆弧形末端切口(Arc-ENF)试样进行DCB试验。基于梁的弯曲理论和Irwin-Kies公式得到Arc-ENF试样的柔度公式与I型临界能量释放率G_IC公式,并且利用ABAQUS软件对DCB试验进行数值模拟。最终,通过对比分析理论公式计算结果、数值模拟结果和DCB试验结果来验证柔度公式和G_IC公式的合理性和有效性,对带有任意弧度的DCB试样的I型层间断裂韧性的测试与分析具有参考价值。      

Adhesive repair of bismaleimide/carbon fiber composites with bisphenol E cyanate ester

The adhesive strength and repair efficiency of bisphenol E cyanate ester (BECy) is investigated for the injection repair of high temperature polymer-matrix composites (PMCs) by lap shear (LS), short beam shear bending (SBSB), and double-cantilever beam (DCB) tests. Bismaleimide/carbon fiber (BMI-cf) composites were chosen as a model substrate. The BECy resin showed similar strength at room temperature to a benchmark epoxy adhesive and outperformed the epoxy at high temperature (200 °C) in all mechanical tests performed. The influence of moisture content of the PMC substrate on the adhesive strength of BECy was systematically investigated. Drying of PMC before repair was necessary for excellent repair performance. Both the flexural strength of repaired SBSB specimens and the inter-laminar fracture toughness of repaired DCB specimens were significantly higher than that of the control composites and stable over a broad temperature range.     

Linear and nonlinear torsional behavior of unidirectional CFRP and GFRP

The helicopter bearingless rotor flexbeam is usually made of glass-fiber reinforced plastic composite (GFRP). Carbon-fiber composites (CFRP) are candidate for future flexbeam materials due to their superior tensile fatigue strength. This research examines the feasibility of CFRP as a future flexbeam material. The torsion behaviors of unidirectional CFRP and GFRP with the same matrix resin were investigated. As a result, it was confirmed that the behavior of both CFRP and GFRP is comprised of linear/nonlinear domains. The initial torsional rigidity of CFRP was almost the same as that of GFRP. The torsional rigidities calculated from Lekhnitskii’s equations agreed with the experimental results, and they are mainly determined by the shear stiffness of the materials. The nonlinear torsional behavior was observed above 0.5% of the shear strain, and it is due to plastic deformation of the matrix resin. A 3D plasticity model proposed by Sun et al. was applied to the plasticity parameters obtained from off-axis tensile tests. The numerical curves agree with the experimental data below 1.5% of the shear strain. The experimental result suggests that GFRP can be replaced by CFRP as torsional elements of a helicopter flex beam without an increase in torsional rigidity.     

海水浸泡对FRP筋-珊瑚混凝土粘结性能的影响

开展了30℃海水浸泡条件下玻璃纤维增强树脂基复合材料（GFRP）筋、碳纤维增强树脂基复合材料（CFRP）筋与珊瑚混凝土粘结性能的试验研究,分析了纤维增强树脂基复合材料（FRP）筋-珊瑚混凝土粘结滑移曲线特征、破坏形态及粘结强度变化。试验结果表明,海水浸泡后FRP筋力学性能和粘结性能均表现为不同程度的降低。随浸泡时间增加,GFRP筋表层树脂与纤维间的孔隙率明显增大,并逐渐出现脱粘现象,纤维本身遭受到侵蚀,而CFRP筋仅表面基体有少许损伤,其耐久性明显优于GFRP筋;FRP筋-珊瑚混凝土粘结强度呈现出先增加后减小的趋势,且后期下降速率逐渐变小,部分GFRP筋-珊瑚混凝土试件的破坏模式逐渐由筋被拔出转变为筋材断裂;增加保护层厚度能有效地减缓海水对GFRP筋的侵蚀,有利于保持GFRP筋-珊瑚混凝土间的粘结性能。     

Piezoelectric control of delamination response in woven fabric composites under mode I loading

This paper investigates the application of piezoelectric actuators to control the delamination response in woven fabric composites subjected to Mode I loading. Experiments were conducted on a double cantilever beam (DCB) specimen of woven glass fiber reinforced polymer (GFRP) composite laminates with piezoelectric ceramic actuators bonded on the surfaces, in order to evaluate the dependence of the delamination behavior on the applied electric fields. A finite element analysis of the DCB specimen with surface-bonded actuators was also performed, and a comparison was made between the finite element predictions and the test results. In addition, the effect of the actuator location on the effectiveness of the piezoelectric control was examined numerically.     

玻璃纤维布/ES-CEP复合材料粘结修理金属结构的耐久性试验研究

随着FRP修复技术的广泛应用,其修复结构的耐久性也越来越受到人们的关注。通过设计不同质量比的有机硅环氧树脂/脂环族环氧树脂(ES/CEP)在干湿循环作用下玻璃纤维增强复合材料(GFRP)和GFRP粘接修复损伤试样的拉伸试验,探讨树脂配比、干湿环境对GFRP和GFRP修复损伤铝板耐久性的影响。试验结果表明:干湿循环对GFRP的力学性能影响较小,而对GFRP修复试样性能影响较大,修复试样的极限载荷出现较大幅度的下降。改变树脂的配比结构,引入耐久性能较好的树脂,可以同时提高GFRP的修复效率和修复构件的耐久性能。     

Modeling and analysis for surface roughness in machining glass fibre reinforced plastics using response surface methodology

Now a days glass fiber reinforced plastic (GFRP) composite materials are a feasible alternative to engineering materials. They have excellent properties and are being extensively used in variety of engineering applications. However, the users of FRP are facing difficulties to machine it, because of its anistropic properties. In this paper, an attempt has been made to model the surface roughness through response surface method (RSM) in machining GFRP composites. Four factors five level central composite, rotatable design matrix is employed to carryout the experimental investigation. Analysis of variance (ANOVA) is used to check the validity of the model. For finding the significant parameters student’s t-test is used. Also, an analysis of the influences of the entire individual input machining parameters on the response has been carried out and presented in this study.     

侵蚀环境下FRP条带加固锈蚀钢筋混凝土圆柱轴心受压试验

通过侵蚀环境下碳纤维增强聚合物(CFRP)复合材料条带和玻璃纤维增强聚合物(GFRP)复合材料条带加固锈蚀钢筋混凝土圆柱试验,分析了侵蚀环境对混凝土强度、纤维增强聚合物基复合材料加固锈蚀柱的极限荷载和荷载-轴向位移曲线的影响。结果表明,混凝土强度受冻融环境影响较大,受干湿环境影响较小;纤维增强聚合物(FRP)复合材料加固锈蚀柱的轴向极限荷载与冻融循环次数、钢筋锈蚀率及FRP复合材料种类有关,随冻融循环次数分别增加到25次、50次、75次,GFRP复合材料条带和CFRP复合材料条带加固锈蚀钢筋混凝土圆柱的轴向极限荷载分别降低了10.97%、13.37%、16.04%和5.95%、4.66%、4.33%;FRP复合材料加固锈蚀柱的刚度和耗能受侵蚀环境种类、侵蚀环境作用次数、锈蚀率及FRP复合材料种类的影响。在试验研究的基础上,通过理论分析侵蚀环境下混凝土强度损伤系数和锈蚀钢筋强度退化方程,提出了侵蚀环境下FRP复合材料条带加固锈蚀钢筋混凝土圆柱轴心受压承载力计算方法。      

新型轻木GFRP夹芯板拉挤成型工艺及其界面性能

选用无碱玻璃纤维束、短切纤维毡、不饱和树脂与泡桐木芯材,制备了轻木-玻璃纤维增强塑料(GFRP)夹芯板,对其拉挤工艺进行了研究.研究表明:设定模具加热温度(凝胶区)为160 ℃、选取的拉挤速率为10 cm/min时,可制造得到表观性能良好的泡桐木-GFRP夹芯板.通过双悬臂梁(DCB)试验,在芯材表面开槽和不开槽2种情况下,研究了泡桐木与GFRP面层之间的界面黏结性能,并与真空导入工艺制作的夹芯板的界面黏结性能进行了对比.结果表明:拉挤工艺生产的泡桐木-GFRP夹芯板的界面黏结性能已达到甚至优于真空导入工艺生产的.芯材表面开槽可以有效提高试件的界面能量释放率,且对真空导入工艺制作的试件效果更为明显.在拉挤工艺中,树脂难以有效填充齿槽形成"树脂钉",故不能明显提高界面黏结力.在对界面性能要求不严格时,拉挤工艺中芯材表面可不开槽,以减少生产工序、降低生产难度.     

玻璃纤维增强聚合物复合材料筋与工程水泥基复合材料黏结性能

为了研究玻璃纤维增强聚合物（GFRP）复合材料筋和工程水泥基复合材料（ECC）黏结性能的影响因素,对42个GFRP/ECC试件进行了拉拔试验,分析了GFRP复合材料筋表面形式、直径、ECC基体强度及保护层厚度等因素对GFRP复合材料筋与ECC基体黏结性能的影响。结果表明:GFRP/ECC试件的破坏形式主要有拔出破坏、筋剥离剪切破坏、劈裂破坏三种形式。表面带肋GFRP复合材料筋黏结强度比光滑GFRP复合材料筋高约66%;当ECC保护层厚度由1.5D（D为GFRP筋直径）增大至4D时,GFRP/ECC黏结强度提高了约58%;当GFRP复合材料筋直径为12~18 mm时,GFRP/ECC黏结强度随着GFRP复合材料筋直径的增大而降低;ECC强度由33.7 MPa增大至73.3 MPa时,GFRP/ECC黏结强度增大约3倍。增加GFRP复合材料筋表面形式复杂程度,或一定程度上提高ECC基体保护层厚度、提高ECC强度等级,有助于提高GFRP复合材料筋与ECC的黏结强度。      

Mechanical properties of fire-retardant glass fiber-reinforced polymer materials with alumina tri-hydrate filler

Alumina tri-hydrate (ATH) can be effectively used to increase fire resistance of Fiber-Reinforced Polymer (FRP) materials. This paper studies the effect of ATH filler on mechanical properties of Glass FRP (GFRP) material, based on compression, tension, shear and flexural test results from three types of GFRP materials with the amount of 0% (control), 25%, and 50% ATH filler by weight of the resin. It was found that the control was the strongest for all tests except for flexure, which is 3% lower than the flexural strength of 25% ATH sample. The compressive strength dropped 19% and 25% for 25% and 50% ATH loadings, respectively, compared to the control. For shear and tensile strengths, the 25% ATH sample acted similarly to the control, but the 50% ATH sample had a significantly lower strength. For stiffness, changing the additive amount from 0% to 50% had only small changes for compression, tension, and flexure. It can be concluded that adding ATH generally decreases the strength and makes FRP more brittle. The performance of a 25% ATH loading is comparable to the control except compression, while a 50% ATH loading has a more significant effect on the mechanical properties of the GFRP. The data presented in this paper can be used to develop fire-resistant FRP systems.     

Adhesive bonding of carbon fiber reinforced composite using UV-curing epoxy resin

Carbon fiber reinforced materials are widely used in a variety of products due to their stiffness, high strength and light weight. However, the strength of fiber reinforced composites will dramatically decrease when they have suffered damage from impact. Therefore, repair is necessary to maintain integrity. In many cases, speed of this repair is paramount. In this work, UV resins adhered to a damaged panel to form a hard patch are considered for fast repair. The challenge in using UV curing resins on carbon fiber reinforced materials is the non-UV transparency of the composite. In this work, a cationic UV epoxy resin is used due to its characteristic of dark polymerization after UV exposure. ASTM lap shear testing showed the shear stress was above 1000 psi. However, the large scale testing failed due to partial curing of adhesive before repair indicating that control in dosing and resin delivery is critical, yet problematic.     

聚酰亚胺颗粒层间增韧碳纤维/邻苯二甲腈树脂复合材料

邻苯二甲腈树脂是一种新型的高性能热固性树脂,具有优良的力学性能和耐高温性能,而邻苯二甲腈树脂本身的脆性限制了其用作结构材料方面的应用。本文采用热塑性聚酰亚胺(PI)颗粒对邻苯二甲腈树脂复合材料进行层间增韧改性,研究改性前后复合材料的耐热性能和力学性能。研究发现,使用PI对邻苯二甲腈复合材料进行改性时,随着掺入量的增加,复合材料的玻璃化转变温度降低。PI颗粒的引入会显著提高复合材料韧性,10wt% PI改性复合材料层间剪切强度提高了41.2%,15wt% PI改性复合材料的Ⅰ型层间断裂韧性提高了156.3%。复合材料的层间能够清晰地观察到颗粒的存在;PI的质量分数进一步提高时,出现粒子团聚缺陷,导致复合材料的层间剪切强度下降。此外PI增韧邻苯二甲腈树脂复合材料在380℃下的层间剪切强度与未改性复合材料数值相当,该温度下PI颗粒的含量已不是影响复合材料韧性的主要因素。      

Reusing recycled fibers in high-value fiber-reinforced polymer composites: Improving bending strength by surface cleaning

Glass fiber-reinforced polymer (GFRP) composites and carbon fiber-reinforced polymer (CFRP) composites were recycled using superheated steam. Recycled glass fibers (R-GFs) and recycled carbon fibers (R-CFs) were surface treated for reuse as fiber-reinforced polymer (FRP) composites. Treated R-GFs (TR-GFs) and treated R-CFs (TR-CFs) were characterized by scanning electron microscopy (SEM) and remanufactured by vacuum-assisted resin transfer molding (VARTM). Most residual resin impurities were removed by surface treatment. Analysis indicated no adverse effect of surface treatment on bending strength. The mechanical properties of the TR-GF reinforced polymer (TR-GFRP) and TR-CF reinforced polymer (TR-CFRP) composites were determined and compared with those of R-GF reinforced polymer (R-GFRP) and R-CF reinforced polymer (R-CFRP). The bending strengths of R-GFRP (26%) and R-CFRP (49%) were very low, compared to that of virgin glass fiber-reinforced polymer (V-GFRP) and that of virgin carbon fiber-reinforced polymer (V-CFRP). The bending strength of TR-GFRP composites was improved to about 90% of that of V-GFRP, and the bending strength of TR-CFRP composites was improved to about 80% of that of V-CFRP.     

Flexural behavior of reinforced concrete (RC) beams retrofitted with hybrid fiber reinforced polymers (FRPs) under sustaining loads

This paper reports experimental studies of reinforced concrete (RC) beams retrofitted with new hybrid fiber reinforced polymer (FRP) system consisting carbon FRP (CFRP) and glass FRP (GFRP). The objective of this study is to examine effect of hybrid FRPs on structural behavior of retrofitted RC beams and to investigate if different sequences of CFRP and GFRP sheets of the hybrid FRPs have influences on improvement of strengthening RC beams. Toward that goal, 14 RC beams are fabricated and retrofitted with hybrid FRPs having different combinations of CFRP and GFRP sheets. The beams are loaded with different magnitudes prior to retrofitting in order to investigate the effect of initial loading on the flexural behavior of the retrofitted beam. The main test variables are sequences of attaching hybrid FRP layers and magnitudes of preloads. Under loaded condition, beams are retrofitted with two or three layers of hybrid FRPs, then the load increases until the beams reach failure. Test results conclude that strengthening effects of hybrid FRPs on ductility and stiffness of RC beams depend on orders of FRP layers.     

Effect of a crack on strength of fibre-reinforced plastics

In unidirectionally reinforced composites with an elastic-plastic matrix, there is a plastic zone with lengthY ₀ proportional to the crack lengthC (Y ₀ C) at the tip of a crack. This results in a new logarithmic dependence of glass and aramid PABI fibre-reinforced plastics (FRP) on crack length and non-fulfilment of the Griffith criterion. In glass and PABI FRP without an artificial notch, defects already exist equivalent to a crack with a length depending on composite fabrication practice. In GFRP, the epoxy matrix shear yield stress grows 2.0 to 2.5 times, compared to the yield in thin films due to fibre constraint of matrix yielding. The stress distribution in front of a crack in a highly anisotropic composite with an elastic-plastic matrix is derived. The stress concentration at the tip of a crack grows with increasing matrix yield stress, resulting in a change of failure mode from accumulation of fibre breaks at low matrix strength, to brittle failure at high matrix strength. The following factors lead to composite embrittlement: (1) increase of matrix yield stress and composite shear strength; (2) decrease of temperature; (3) increase of Young's modulus of the fibre; (4) reduction of fibre strength. The dependence of aramid PPTA FRP strength on temperature exhibits a maximum. Epoxy matrix plastification leads to some increase of aramid PPTA FRP strength.     

The tensile fatigue behaviour of a silica nanoparticle-modified glass fibre reinforced epoxy composite

An anhydride-cured thermosetting epoxy polymer was modified by incorporating 10 wt.% of well-dispersed silica nanoparticles. The stress-controlled tensile fatigue behaviour at a stress ratio of R = 0.1 was investigated for bulk specimens of the neat and the nanoparticle-modified epoxy. The addition of the silica nanoparticles increased the fatigue life by about three to four times. The neat and the nanoparticle-modified epoxy resins were used to fabricate glass fibre reinforced plastic (GFRP) composite laminates by resin infusion under flexible tooling (RIFT) technique. Tensile fatigue tests were performed on these composites, during which the matrix cracking and stiffness degradation was monitored. The fatigue life of the GFRP composite was increased by about three to four times due to the silica nanoparticles. Suppressed matrix cracking and reduced crack propagation rate in the nanoparticle-modified matrix were observed to contribute towards the enhanced fatigue life of the GFRP composite employing silica nanoparticle-modified epoxy matrix.