Plate bending behavior of a pultruded GFRP bridge deck system

The bi-directional plate bending behavior of a pultruded GFRP bridge deck system with orthotropic material and system properties was investigated by means of two full-scale experiments and numerical modeling. Furthermore, the maximum span of the deck between two main girders was determined using Eurocode loading and presupposing a maximum deflection ratio of span/300.

Compared to an isotropic plate-strip, the bi-directional behavior of the orthotropic deck was not very pronounced. Nevertheless, selecting experiment specimen with five profiles instead of only three reduced the maximum deflections at the serviceability limit state (SLS) by ca. 50%.

Therefore, since the SLS governs in the design of GFRP bridge decks, the possible contribution of bi-directional plate bending is not insignificant and should be considered and improved in order to fully exploit the potential of pultruded GFRP bridge decks.     

Flexural fatigue analysis of a CFRP form reinforced concrete bridge deck

Concrete bridge decks reinforced with fiber reinforced polymer (FRP) composite panels have recently been used where the FRP panels also serve as the permanent formwork for concrete. Comparing to their short-term behavior, their long-term performance especially under repeated traffic loads (fatigue) has not yet been widely known. This paper presents a fatigue analysis tool developed for a new steel-free concrete bridge deck reinforced with carbon FRP stay-in-place form. The developed model takes into account the cyclic creep of concrete in compression, the reduction in flexural stiffness due to fatigue tensile cracking and the reduction in modulus of rupture under cyclic loading. Comparisons with experimental data show reasonable agreement where a full-size 2-span deck specimen was subjected to millions of fatigue cycles. The parametric study recommends reducing the amount of FRP reinforcement and concrete strength of the current design, and lower loading rate may introduce more stiffness degradation in the system.     

Development of a pedestrian bridge with GFRP profiles and fiber reinforced self-compacting concrete deck

In recent years, the number of pedestrian bridges built from composites materials has notably increased. The combination of fiber reinforced polymers (FRP) profiles with fiber reinforced concrete (FRC) elements is being adopted in this type of structures, since the ductility, high post-cracking tensile strength, compressive stiffness and strength of FRC can be combined with the benefits derived from the use of FRP’s profiles to obtain high performance structural systems.     

Quasi-static and fatigue performance of a cellular FRP bridge deck adhesively bonded to steel girders

This paper describes the quasi-static and fatigue performance of hybrid bridge girders composed of cellular FRP bridge decks and steel girders. The FRP bridge deck is connected adhesively to the steel girders and acts as the top chord of the hybrid section. Compared to a reference steel girder, the stiffness and quasi-static load-carrying capacity of the hybrid girders were considerably increased due to composite action between the FRP decks and the steel girders. Failure due to quasi-static loading occurred in the FRP decks during yielding of the bottom steel flanges. The adhesive bond between the FRP decks and the steel girders showed no signs of damage due to fatigue loading. The results of the investigation showed that the well-established design method for steel–concrete composite girders with shear stud connections can essentially be used for the design of such FRP-steel girders. The principal modifications necessary for design are proposed.     

The static behavior of a modular foam-filled GFRP bridge deck with a strong web-flange joint

The static behavior of a modular bridge deck filled with a low-density polyurethane foam was experimentally investigated. The web-flange joint of the deck was strong enough so that a failure of the deck in the transverse direction was governed by the delamination of the bond between two adjacent modules whether the deck was filled or not. Although the elastic modulus of the foam was only a thousandth of the homogenized modulus of the GFRP deck, the structural performance of the deck in the transverse direction was significantly improved by the foam filled inside the deck. It was shown experimentally that tensile stress could develop in the top flange of the deck subjected to three point bending because of shear deformation. Such a development of tensile stress was significantly mitigated by the foam filled inside the deck.     

Load and resistance factor design of fiber reinforced polymer composite bridge deck

The majority of our bridges were constructed with conventional civil engineering materials of steel and concrete in a typical slab on girder or truss construction. Reinforced concrete bridge decks have approximately 40% life of the steel girders that support these structures. In order to support the use of alternative materials to replace deteriorating concrete decks, this paper outlines the Load and Resistance Factor Design (LRFD) of Fiber Reinforced Polymer composite (FRP) panel highway bridge deck. The deck would be of a sandwich construction where 152.4 mm × 152.4 mm × 9.5 mm square pultruded glass FRP (GFRP) tubes are joined and sandwiched between two 9.5 mm GFRP plates. The deck would be designed by Allowable Stress Design (ASD) and LRFD to support AASHTO design truckload HL-93. There are currently no US standards and specifications for the design of FRP pultruded shapes including a deck panel therefore international codes and references related to FRP profiles will be examined and AASHTO-LRFD specifications will be used as the basis for the final design. Overall, years of research and laboratory and field tests have proven FRP decks to be a viable alternative to conventional concrete deck. Therefore, conceptualizing the design of FRP bridge decks using basic structural analysis and mechanics would increase awareness and engineering confidence in the use of this innovative material.     

不同温度下玻璃钢材料放气速率的试验研究

设计了一套基于压差流量法的试验装置来测量玻璃钢试样的放气速率。将试样的表面采用砂纸（500#）进行打磨，采用扫描探针显微镜对试样表面粗糙度进行测量。测量了不同温度下玻璃钢试样的放气速率。试验结果表明测量室温度越高，测量室的气体压力越高，玻璃钢试样的放气速率越大。     

Effect of carbon black nanoparticle intrinsic properties on the self-monitoring performance of glass fibre reinforced composite rods

Self-monitoring composite rods, made of an internal conductive core surrounded by an external structural skin, were manufactured and tested. Both parts were made of glass fibre-epoxy. Electrical conductivity was achieved in the inner core by incorporating as an alternative high surface area or low surface area carbon black in the resin. Self-monitoring performance was assessed by simultaneous mechanical and electrical resistance measurements. The aim was to correlate the electrical resistance variation to stress. Only one type of material showed appropriate self-monitoring properties, since increase of electrical resistance was recorded at increasing loading (both monothonic and cyclic tensile loading), while electrical resistance recovery at high loads was found in the other case. Calorimetric analysis, rheological measurements and SEM observations were carried out to explain this result. Filler dispersion seems to be the key feature affecting the self-monitoring properties. Only high surface area nanoparticles can ensure self-monitoring reliability.     

Joint performance of the glass fiber reinforced polypropylene leaf spring

Commercial utilization of the composite leaf springs in the suspension application is significantly decided by its eye end joint performance. Present work attempts to design and evaluate the performance of double bolted end joint for thermoplastic composite leaf spring. Injection molded 20% glass fiber reinforced polypropylene leaf springs were considered for the joint strength evaluation. Servo hydraulic test facility is utilized to evaluate the static and fatigue performance of the bolted joint. Various bolt sizes were utilized for the joint and its performances were evaluated under static loading condition to understand the effect of fit between bolt and its hole of the joints. Ultimate bearing strength of the joint is found to decrease with the increase in the clearance between bolt and part hole. Joints were subjected to various amplitudes of completely reversed fatigue loads to evaluate the endurance strength. Load–deflection hysteresis plot of the joint under fatigue conditions is continuously measured and used as the bearing damage index of the joint. Inspection of the bearing surface tested under static and fatigue loading condition revealed severe matrix deformation and fibrillation. In spite of unidirectional load being acted at the joint, curved nature of the bearing surface induces bi-axial stresses, which results in severe matrix fibrillation at the bearing surface. Failure morphology under static conditions shows net-tension beside the bearing damage. Failure morphology under fatigue condition revealed net-tension, and shear-out failures besides the bearing damages.     

Mechanical behaviour of glass and carbon fibre reinforced composites at varying strain rates

The choice of composite materials as a substitute for metallic materials in technological applications is becoming more pronounced especially due to the great weight savings these materials offer. In many of these practical situations, the structures are prone to high impact loads. Material and structural response vary significantly under impact loading conditions as compared to quasi-static loading. The strain rate sensitivity of both carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP) are studied by testing a single laminate configuration, viz. cross-ply [0°/90°] polymer matrix composites (PMC) at strain rates of 10⁻³ and 450 s⁻¹. The compressive material properties are determined by testing both laminate systems, viz. CFRP and GFRP at low to high strain rates. The laminates were fabricated from 48 layers of cross-ply carbon fibre and glass fibre epoxy. Dynamic test results were compared with static compression test carried out on specimens with the same dimensions. Preliminary compressive stress–strain vs. strain rates data obtained show that the dynamic material strength for GFRP increases with increasing strain rates. The strain to failure for both CFRP and GFRP is seen to decrease with increasing strain rate.     

Fatigue performance of a self-piercing rivet joint between aluminum and glass fiber reinforced thermoplastic composite

Lightweight structures are more and more widely used in the automotive industry due to the growing importance of environment regulations related to CO₂ emissions. In this context of saving weight, composites offer an alternative to metals because they can achieve a better stiffness to weight ratio. A problematic becomes crucial: which process can be used to join efficiently composite and metallic parts?An innovative way would be the application of self-piercing riveting to thermoplastic composite–metal structure. Since the self-piercing riveting does not require a pre-drilled hole, the time process is short. Nevertheless, this process generates damage in the composite such as fiber cutting and delamination.The aim of this work is to evaluate the fatigue strength of a PA6.6-GF (Glass Fiber reinforced Polyamide 6.6)/Aluminum assembly joined by self-piercing riveting. Experimental results show that the SPR joint achieve high fatigue resistance on uniaxial shearing test. The joint strength at 2 · 10⁶ cycles is more than half of the joint strength in static. Joint manufacturing process parameters like the rivet shape were investigated. Some fatigue tests were performed under severe environmental conditions like high temperature. This study shows that process parameters have less influences on the joint strength than the parameters that impact the composite resistance such as the composite type and the test temperature. The composite stresses evolution is useful for the failure modes analyses.     

Optimization of infrared radiation cure process parameters for glass fiber reinforced polymer composites

Elevated temperature post curing is one of the most critical step in the processing of polymer composites. It ensures that the complete cross-linking takes place to produce the targeted properties of composites. In this work infrared radiation (IR) post curing process for glass fiber reinforced polymer composite laminates is studied as an alternative to conventional thermal cure. Distance from the IR source, curing schedule and volume of the composite were selected as the IR cure parameters for optimization. Design of experiments (DOE) approach was adopted for conducting the experiments. Tensile strength and flexural strength of the composite laminate were the responses measured to select the final cure parameters. Analysis of variance (ANOVA), surface plots and contour plots clearly demonstrate that the distance from the IR source and volume of the composite contribute nearly 70% to the response functions. This establishes that polymer composites cured using IR technique can achieve the same properties using only 25% of the total time compared to that of conventional thermal curing.     

Enhancement of delamination fatigue resistance in carbon nanotube reinforced glass fiber/polymer composites

We show that the addition of small volume fractions of multi-walled carbon nanotubes (CNTs) to the matrix of glass–fiber composites reduces cyclic delamination crack propagation rates significantly. In addition, both critical and sub-critical inter-laminar fracture toughness values are increased. These results corroborate recent experimental evidence that the incorporation of CNTs improve fatigue life by a factor of two to three in in-plane cyclic loading. We show that in both the critical and sub-critical cases, the degree of delamination suppression is most pronounced at lower levels of applied cyclic strain energy release rate, ΔG. High-resolution scanning electron microscopy of the fracture surfaces suggests that the presence of the CNTs at the delamination crack front slows the propagation of the crack due to crack bridging, nanotube fracture, and nanotube pull-out. Further examination of the sub-critical fracture surfaces shows that the relative proportion of CNT pull-out to CNT fracture is dependent on the applied cyclic strain energy, with pull-out dominating as ΔG is reduced. The conditions for crack propagation via matrix cracking and nanotube pull-out and fracture are studied analytically using fracture mechanics theory and the results compared with data from the experiments. It is believed that the shift in the fracture behavior of the CNTs is responsible for the associated increase in the inter-laminar fracture resistance that is observed at lower levels of ΔG relative to composites not containing CNTs.     

The dispersion of SWCNTs treated by dispersing agents in glass fiber reinforced polymer composites

It is an obstacle issue for carbon nanotubes (CNTs) particularly for single-wall carbon nanotubes (SWCNTs) with nano-level dispersion in fiber reinforced polymer matrix composites. In this paper, the dispersing agents such as Volan and BYK-9076 were employed to treat SWCNTs to improve their dispersion in the glass fiber/epoxy (GF/EP) composites. The dispersing results of SWCNTs in composites were observed by scanning electron microscopy (SEM). Then the glass transition temperature (T_g) of these kinds of composites with treated and untreated SWCNTs were obtained by dynamic mechanical thermal analysis (DMTA). Moreover, the flexural tests were performed on these composites. Based on the experiment results, the dispersion of SWCNTs was improved and the flexural property of SWCNTs/GF/EP composite was enhanced too.     

Structural design and mechanical performance test of densely drilled glass fiber reinforced plastics pipelines

Densely drilled glass fiber reinforced plastic (GFRP) pipelines are thought to be of prosperous future in sand control in oilfield. However, due to the fact that the mechanical properties of the perforated GFRP pipelines are always lowered remarkably, some structural design work must be done. Several key factors, including the winding angle of the glass fibers, the mechanical properties of the matrix resin were considered carefully in advance. The tensile strength, compressive strength and the screw-crushing properties of the GFRP pipelines were measured subsequently. Most of the test results were coincided with what had been expected during structural design. The winding angle was proved to be an important factor in improving the mechanical performance of perforated GFRP pipelines. Mechanical property of the matrix resin was another important factor in determining the performance of the GFRP pipelines. The effect of the hole-size and distribution on the mechanical performance of the heavily perforated GFRP pipelines always depended on the winding angle and matrix resin. In the screw-crushing test, the GFRP pipelines showed to be easily destroyed by the slowly rotating drill head.     

多丝碳纤维拉索研制及静载试验研究

为了解决拉索锈蚀和疲劳问题,提高其耐久性,采用轻质、高强、耐腐蚀和耐疲劳的碳纤维(CFRP)筋制作拉索.以环氧树脂砂浆为粘结剂,研制CFRP筋粘结式锚具及成套拉索,并进行了静载试验.分析了影响CFRP拉索锚固性能的各种因素,并进行了相关试验.研究结果表明,筋表面粗糙程度、锚具内锥度、粘结胶的性能和灌浆压力等直接影响锚具的锚固性能.所研制的多丝CFRP拉索的性能稳定,锚固效率系数达95%以上,可直接应用于实际工程.     

Mode III fatigue delamination growth of glass fiber reinforced polymer woven laminates at cryogenic temperatures

This paper investigates the cryogenic fatigue delamination behavior of glass fiber reinforced polymer woven laminates under Mode III loading. Fatigue delamination tests were conducted using split cantilever beam specimens at room temperature, liquid nitrogen temperature (77 K) and liquid helium temperature (4 K). A finite element analysis was also employed to calculate the energy release rate. The temperature dependence of the fatigue delamination growth rate vs. energy release rate range is discussed. Fracture surfaces were examined by scanning electron microscopy to identify the delamination mechanisms under fatigue loading. The important conclusion we reach is that the Mode III fatigue delamination growth rates of woven laminates at cryogenic temperatures are lower than that at room temperature.     

Vibration welding of a unidirectional continuous glass fiber reinforced polypropylene GMT

This paper presents experimental results of vibration welding of a continuous fiber GMT composite of E-glass glass fiber reinforced polypropylene. Vibration welding parameters investigated were vibration time, clamping pressure and vibration amplitude. The effects of these parameters on penetration and lap shear strength of the composite were determined. It was shown that clamping pressure and vibration time should be properly selected to optimize the lap shear strength. Temperature measurements made during vibration welding showed the importance of these two parameters on the interface temperature required for proper vibration welding.     

短纤维增强树脂基复合材料强度和模量的各向异性

研究了短纤维增强聚合物复合材料(SFRP)的强度和模量的各向异性。纤维的平均长度l_(mean)对纤维增强有效因子有很大的影响。在Φ=0°,纤维增强有效因子随着l_(mean)的增加而增加;当Φ=90°,纤维有效因子在Θ不太大时随着l_(mean)增加而增加,当Θ很大时,纤维有效因子值变成零。θ_(mean)对纤维有效因子也有很重要的影响。在Φ=0°,Θ不太大(<40°)时,纤维有效因子随着θ_(mean)增加而减小;而当Θ很大(>50°)时,则随着θ_(mean)的增加而增大。在Φ=90°,Θ不太大时,纤维有效因子随着θ_(mean)增加而减小;而当Θ很大时,纤维有效因子值为零。模式纤维长度对复合材料的强度无明显影响。大l_(mean)对应高的复合材料模量。当Θ接近60°时,平均纤维长度对模量的影响不大。模式纤维长度对模量的影响相对比较小,而对于一个很小的l_(mean),影响则比较明显。当Θ很小时,θ_(mean)值越小,模量值越高;相反,Θ很大时,θ_(mean)值越小,模量值越低。     

Finite element modeling and testing of a deformable carbon fiber reinforced polymer mirror

Thin-shelled composite mirrors have been recently proposed for use as deformable mirrors in optical systems. Large-diameter deformable composite mirrors can be used in the development of active optical zoom systems. We present the fabrication, testing, and modeling of a prototype 0.2 m diameter carbon fiber reinforced polymer mirror for use as a deformable mirror. In addition, three actuation techniques have been modeled and will be presented.