Pultruded Glass Fiber Research Articles

Axial compression behaviour of all-composite modular wall system

The structural behaviour of modular wall systems made from pultruded glass fibre reinforced polymer profile and composite sheathings was evaluated experimentally and numerically. Full-scale wall panels were tested under axial compression to investigate critical design parameters including presence of wall sheathing, connections between sheathing and frame, width of the panel, and frame configurations. The results showed that the failure of the wall panels, where top and bottom plates are extended throughout the width, is governed by the lateral deformation of the plate due to their low transverse strength and stiffness. Finite element (FE) results of the composite wall systems with extended studs showed that they are ten times stiffer and stronger than the walls with extended plates. This study demonstrated the high potential of fibre composite materials for the modular wall systems.

Material Selection and Characterization for a Novel Frame-Integrated Curtain Wall.

Curtain walls are the façade of choice in high-rise buildings and an indispensable element of architecture for a contemporary city. In conventional curtain walls, the glass panels are simply supported by the metal framing which transfers any imposed load to the building structure. The absence of composite action between glass and metal results in deep frames, protruding to the inside, occupying valuable space and causing visual disruption. In response to the limited performance of conventional systems, an innovative frame-integrated unitized curtain wall is proposed to reduce structural depth to one fifth (80%) allowing an inside flush finish and gaining nettable space. The novel curtain wall is achieved by bonding a pultruded glass fiber reinforced polymer (GFRP) frame to the glass producing a composite insulated glass unit (IGU). This paper selects the candidate frame and adhesive materials performing mechanical tests on GFRP pultrusions to characterize strength and elasticity and on GFRP-glass connections to identify failure module and strength. The material test results are used in a computer-based numerical model of a GFRP-glass composite unitized panel to predict the structural performance when subjected to realistic wind loads. The results confirm the reduction to one fifth is possible since the allowable deflections are within limits. It also indicates that the GFRP areas adjacent to the support might require reinforcing to reduce shear stresses.

Experimental Investigation of Long Term Seawater Durability and Shear Properties of Pultruded GFRP Composite

The effect of long term immersion in seawater at different temperatures on the properties of pultruded glass fibre reinforced polymer (GFRP) composite rebar was investigated. Samples were conditioned in seawater and in dry at 23, 55 and 75 °C for 0, 8, 20, 30 and 36 months to analyse the changes in shear properties such as transverse shear strength (TSS) and short beam shear strength (SBSS). Both TSS and SBSS increased after conditioning in dry at 55 and 75 °C; on the other hand, TSS decreased gradually due to conditioning in seawater at 23, 55 and 75 °C, whereas SBSS decreased due to conditioning in seawater only at 75 °C. Microscopic analysis specified that the shear strength decreased due to fibre/matrix interfacial failure as a result of de-bonding and fibre pull-out. Compared to the short beam shear test, the transverse shear test was found to be a sensitive technique to measure the durability of pultruded GFRP rebar. FT-IR analysis indicated superficial hydrolysis reaction of polymer matrix occurred when the sample was conditioned at 75 °C. A reversible change in glass transition temperature (Tg) and in viscoelastic property of the polymer matrix was observed due to conditioning in seawater at 23 and 55 °C.

Quasi-plastic flexural behavior of adhesive-bolt hybrid connection for large scale pultruded GFRP frame

Flexural behavior of an adhesive-bolt hybrid connection for pultruded glass fiber reinforced polymer (GFRP) frame is investigated through monotonic and cyclic loading tests. It is shown that the hybrid connection fabricated using resin adhesive and steel bolts is able to exhibit a quasi-plastic behavior. Multistage damage occurred in tests, and the adhesive failed initially, followed by GFRP failure at bolt holes. Effect of shear force was investigated by variable shear-span ratios in tests. Additionally, moment and rotation curves obtained from monotonic and cyclic loading tests are found to be similar, indicating that loading schemes have little impact on structural performance of the hybrid connection. Energy dissipation is analyzed based on cyclic loading tests. Finite element model is also built, and design formulas are proposed to predict the quasi-yield moment and maximum moment. A good agreement is found between experimental results and analytical predictions. In addition, design recommendation on the use of adhesive-bolt hybrid connection is provided.

Effect of fibre layup and bearing length on the web-crippling behaviour of pultruded GFRP profiles

This paper presents an experimental study about the web-crippling behaviour of pultruded glass fibre reinforced polymer (GFRP) profiles, loaded under end two flange (ETF) and interior two flange (ITF) configurations, with varying bearing lengths. The study was performed to address two significant research needs: (i) to obtain a better understanding of the web-crippling phenomenon in GFRP profiles with different cross-sections and fibre layups; and (ii) to provide additional experimental data on web-crippling, necessary to validate advanced numerical models and to develop design formulae. The experimental programme included materials with different levels of transverse reinforcement, provided by a total of four suppliers. These significant differences in the fibre layups among the profiles tested did not seem to affect the stiffness and ultimate loads significantly. To the contrary, the bearing length was found to have a significant effect on the failure mode, stiffness and ultimate load of all I-section profiles. Moreover, and despite their significant differences in terms of geometrical and material properties, all I-section profiles presented similar transverse compressive strain distributions, when loaded in the same conditions, showing that changes in fibre layups had a negligible effect on the effective bearing length of the various specimens.

Comparison of Static and Long-term Creep Behaviors between Balau Wood and Glass Fiber Reinforced Polymer Composite for Cross-arm Application

Cross arms are mainly made up of wood (conventional) and pultruded glass fiber reinforced polymer composite (modern) installed in suspension tower. However, the creep response of both materials has not been fully covered in many literatures to explain the long-term durability of the current cross arm design. Thus, it is necessary to find the creep trends and models to evaluate the behavior in the tropical outdoor environment. The creep properties of Balau wood and pultruded composite at load of 10, 20 and 30 % of ultimate flexural stress were evaluated from quasi-static flexural test results. Using several creep numerical models, the creep properties of wood and composite cross arms were modelled. The results showed that the GFRP had a significant value of flexural strength, while Balau wood performed better in flexural modulus. In terms of creep properties, GFRP specimen exhibited high creep resistance with greater stability during transition from elastic to viscoelastic phase. From numerical modelling perspective, the simulated creep trends from Burger and Norton models were deviated from the experimental data. Subsequently, the most suitable creep model to forecast the creep behavior for wood and composite specimens was Findley model. All in all, pultruded composite is the most appropriate durable material to be applied in cross arms, while Findley model is a suitable model to represent creep performance of anisotropic materials.

Anisotropic dynamic theory to predict blast responses of composite fluted-core sandwich protective door panels

A dynamic theory of simply supported orthotropic pultruded glass fiber reinforce plastic (GFRP) fluted-core sandwich panels under blast loading was proposed based on the first order shear theory, and the analytical solution was given based on the mode superposition method. The displacement curves predicted by the theory are consistent with finite element modeling (FEM) results. Based on the theory, multi-failure criteria of the fluted-core sandwich panel were proposed to reveal the competition between the facesheet failure and the core shear failure. A new type of composite protective door was assembled from GFRP fluted-core sandwich panels and steel frames. Explosion experiments were carried out and the test displacements and strains were compared with theoretical predictions considering damping. The peak blast pressure the door panel could sustain was predicted by multi-failure criteria. The theory is effective in predicting the elastic dynamic response and failure pressure of the GFRP fluted-core sandwich panel. The composite door has little damage when the scaled distance is larger than 1.494 ​m/kg1/3. With weight of only 111.4 ​kg and excellent performance under blast loading, the GFRP fluted-core sandwich is a good choice for protective doors.

Damage tolerance of adhesively bonded pultruded GFRP double-strap joints

Compared with mechanical fastening, adhesive bonding offers numerous advantages in the joining of pultruded glass fiber reinforced polymer (GFRP) sections. However, one critical issue associated with bonded joints is the assessment of their mechanical behavior considering bondline defects. This paper presents the results of an experimental investigation of the damage tolerance of adhesively bonded pultruded GFRP joints considering bondline defects. Double-strap specimens with and without bondline defects were prepared and tested in tension until failure. The location (five different locations in the bond length and width directions), size (10%, 20%, and 30% of the total bonded area in both the bond length and width directions), shape (triangular, rectangular, square, circular, and elliptical), and number (between 1 and 8) of defects within the bondline were considered as variable parameters. This paper reports and discusses the observed failure modes, load–displacement curves, and joint capacities, considering the effects of bondline defects. Interface debonding was observed in regions neighboring the bondline defects, and delamination was observed in other bonded areas. All joints exhibited a linear elastic load–displacement response with sudden and brittle failure, regardless of the presence of bondline defects. The observed capacity reduction of up to 33% could be significant if the defects were located at the edges of the bonded area. Defects of different shapes resulted in similar reductions in joint capacity (21%). Furthermore, the joint was found to be more sensitive to irregularly shaped (e.g., triangular) defects, and reducing the number of defects was more effective in mitigating the reduction in joint capacity than reducing the total defect area was.

Homogenization effects on simulated pultruded glass fibre reinforced laminate under compression – from static to dynamic models

This study presents a numerical analysis of failure in pultruded glass fibre reinforced polymer (GFRP) with three reinforcement layers, subjected to out-of-plane compressive loadings at low and high strain rates (10-3 s-1 and 103 s-1). The simulations targets to a computationally efficient homogenization with different element types and sizes. A single-element model was created to demonstrate the highest level of homogenization. The material properties in the homogenized model were calculated using the ESAComp (Altair) software. The 3D Hashin failure criterion was implemented as a user-defined subroutine into the finite element method using Abaqus (Simulia/Dassault Systemes) to predict the failure. The comparison between different meshes and elements shows the sufficient accuracy of the homogenized model to predict the material response at the damage onset, but the location of the crack was not accurately predicted as expected. High-rate impact simulations of the Split Hopkinson Pressure Bar tests showed that the mesh does not significantly affect the failure (strain) predicted by the homogenized model.

Buckling Analysis of Pultruded Glass Fiber Reinforced Polymer (GFRP) Angle Sections.

Glass fiber reinforced polymers (GFRP), with their advantage of corrosion resistance, have potential to be used as structural members in civil engineering constructions. Pultruded GFRP angle section trusses could be used instead of steel sections in remote areas and in areas prone to corrosion. The objective of this paper is to study the strength of GFRP angle sections under concentric axial load. Glass fiber reinforced polymer (GFRP) made of E-glass and Isophthalic polyester resin and manufactured by pultrusion process was used for the experimental study. Two GFRP angle sections of size 50 × 50 × 6 mm and 50 × 50 × 4 mm and lengths 500 mm, 750 mm, and 1000 mm were chosen for the study. Further, finite experimental element analysis of the GFRP angle sections was done using ANSYS software and validated with the experimental results. The validated FE model was used for parametric studies varying the slenderness ratio and flange width to thickness ratio (b/t) ratio. It was observed that length of the specimen and thickness influenced the buckling load and buckling mode. An increase in b/t ratio from 8.3 to 12.5 decreases the load carrying capacity by almost 60% at a slenderness ratio of 50.

Flexural behaviour of pultruded GFRP beams infilled with HVFA ECC

This paper presents the experimental and analytical investigation carried out on the flexural behaviour of Pultruded Glass Fiber Reinforced Polymer (GFRP) beams infilled with High Volume Fly Ash Engineered Cementitious Composite (HVFAECC). Tests were conducted on two hollow GFRP beams and two GFRP beams infilled with HVFAECC. Load displacement behaviour and load strain behaviour of the beams were investigated. The load carrying capacity of Pultruded GFRP beams infilled with HVFAECC was significantly more than the hollow GFRP beams. Experimental results were also compared with the finite element analysis.

Influence of Bracing on Buckling Strength of Pultruded Glass Fiber Reinforced Polymer Frames

A numerical study of the influence of structural bracing on the buckling strength of pultruded Glass Fiber Reinforced Polymer (GFRP) frames is presented. Although the influence of bracing on frames made from other materials such as steel have been studied in the past, this paper investigates the performance of pultruded GFRP portal frames with pinned or fixed column bases. Each frame is constructed with pultruded GFRP I-section members. The influence of I-section column major and minor axis orientation is also investigated. The results demonstrate the practical significance of bracing pultruded GFRP frames. The results show that the buckling loads for braced frames are seven to nine times greater than those for unbraced frames when the column bases are pinned. The corresponding gain in the buckling load capacity due to the addition of bracing is more than three times if the column bases are fixed.

Influence of Bracing on Buckling Strength of Pultruded Glass Fiber Reinforced Polymer Frames

A numerical study of the influence of structural bracing on the buckling strength of pultruded Glass Fiber Reinforced Polymer (GFRP) frames is presented. Although the influence of bracing on frames made from other materials such as steel have been studied in the past, this paper investigates the performance of pultruded GFRP portal frames with pinned or fixed column bases. Each frame is constructed with pultruded GFRP I-section members. The influence of I-section column major and minor axis orientation is also investigated. The results demonstrate the practical significance of bracing pultruded GFRP frames. The results show that the buckling loads for braced frames are seven to nine times greater than those for unbraced frames when the column bases are pinned. The corresponding gain in the buckling load capacity due to the addition of bracing is more than three times if the column bases are fixed.

TENSILE AND COMPRESSIVE BEHAVIORS OF THE PULTRUDED GFRP LAMINA

The use of composite materials in civil engineering is increasing day by day due to their superior priorities such as high strength to weight ratio, high corrosion resistance, and durability. One of the recent materials used in the civil engineering application is pultruded glass fiber reinforced polymer (GFRP). Many studies are available in the literature related to the behavior of component (structural) level of the pultruded GFRP; however, very limited data is available related to the behavior of the lamina level of the pultruded GFRP. Since the behaviors of the pultruded GFRP in longitudinal and transverse directions are quite distinct, it is aimed to provide the tensile and compressive behavior of the pultruded GFRP in terms of stiffness, capacity and failure modes. Pursuant to this goal, longitudinal and transverse direction of the pultruded GFRP laminas were tested under both compressive and tensile forces according to ASTM standards. A total of 12 specimens, three replicates for each type, were tested. Moreover, these tests were modelled with the aid of Abaqus. The numerical and experimental results revealed that the transverse strength of pultruded GFRP is much weaker than its longitudinal strength for both compressive and tensile forces. While the damages in tensile tests started in micro dimension and continued as macro and the result of the damage was progressive damage, the rapid progression of damages in compression experiments led to the development of catastrophic damage.

Adiabatic heating and damage onset in a pultruded glass fiber reinforced composite under compressive loading at different strain rates.

Damage onset and adiabatic heating of a pultruded Glass Fiber-Reinforced Plastic (GFRP) composite was investigated using compression tests at low, intermediate and high strain rates (10−3 s−1, 1 s−1 and 103 s−1). Optical and infrared (IR) cameras monitored the specimens during testing, so that the mechanical response, damage onset, and damage evolution were obtained along with the adiabatic heating of the specimen due to plastic deformation and fracture. The results revealed clear strain rate effects on stiffness, strain softening and damage initiation. The simultaneous optical and IR imaging allowed quantitative description of thermomechanical response of the material and studying the formation and propagation of shear localizations and their temperature history. The maximum temperatures in the fracture zones exceed 80 °C at the strain rate of 103 s−1. Scanning Electron Microscopy (SEM) was used to identify the micro-scale crack paths at different strain rates. The findings allow more exact numerical predictions and design of tubular GFRP pipes for impact applications.

Improving the shear strength of bolted connections in pultruded GFRP using glass fiber sheets

Pultruded Glass Fiber Reinforced Polymers (PGFRPs) have been increasingly used in the field of engineering construction. In civil engineering structures, mechanical connections such as bolted connections are widely used because they are an easy way to connect the members. However, this kind of connection for PGFRP has low shear strength when the main part of the PGFRPs features unidirectional glass roving, and the shear strength of this part is determined by the shear strength of the matrix. This problem reduces the mechanical performance of the connections. In this study, the strengthening effects of three types of glass fiber sheets (GFSs) (0°/90°, ±45°, and a chopped strand mat (CSM)) on PGFRP connections were experimentally investigated under tensile loads. Based on the experimental results, GFSs could remarkably improve the ultimate loads and stiffness of PGFRP connections. Moreover, simple formulas were proposed to evaluate the ultimate loads of single PGFRP-bolted connection reinforced by multiaxial GFSs.

Bond performance between FRP tubes and seawater sea sand concrete after exposure to seawater condition

In this study the durability of the bond between different fibre reinforced polymer (FRP) tubes and seawater sea sand concrete (SWSSC) under seawater condition is investigated. Concrete filled pultruded glass fibre reinforced polymer (GFRP) tubes and filament winding GFRP, carbon fibre reinforced polymer (CFRP) and basalt fibre reinforced polymer (BFRP) tubes were exposed to seawater at 25 °C and 40 °C for 1, 3 and 6 months. Push-out tests were carried out to study the bond performance of concrete filled FRP tubes (CFFT). The bond strength changes compared to the reference samples, in terms of the mechanical and chemical bonds, were calculated. The results showed that for all cases except one condition that had the same value as the reference, the maximum bond strength of the tubes increased due to the conditioning, however, the bond strength at the chemical adhesion breaking moment decreased by the conditioning. In other words, the friction coefficients of the samples increased due to conditioning, while the chemical adhesion decreased. Equations are proposed to predict the bond strength corresponding to slip initiations.

Tension analysis of bolted sleeve connection between pultruded GFRP tube and steel member considering adhesion

Pultruded Glass fibre reinforced polymer (GFRP)-steel hybrid structures have become increasingly popular in civil infrastructures. However, the connection between GFRP and steel members is one of the key issues limiting the development of the innovative structure. This paper presents tensile capacity of bolted sleeve connection between GFRP and steel members. With consideration of the pre-loaded bolt effect, the appropriate fastening torque was proposed by finite element investigation. The adhesive effect was also considered and investigated by cohesive zone method. The bolted sleeve connection provides a good solution for the tubular and large-span structures.

Compressive transverse fracture behaviour of pultruded GFRP materials: Experimental study and numerical calibration

This paper presents a study on the transverse fracture behaviour of pultruded glass fibre reinforced polymer (GFRP) materials in compression, namely the assessment of transverse compressive fracture toughness (G2−) and transverse compressive residual strength (σr). These properties were assessed through experimental Compact Compression (CC) tests of six different GFRP materials, which were coupled with a data reduction method to determine experimental predictions of G2− and numerically calibrated as a function of the experimental load vs. displacement curves. Through this process, the expected experimental overestimation of G2−, attributed to contact stresses behind the notch tip, was evaluated and accurate numerical estimates of G2− were determined. The numerical calibration considered both G2− and σr, by considering a bi-linear cohesive law. Through the numerical calibration, the G2− results ranged between 36 and 67 N/mm and σr values varied from 9% to 16% of transverse compressive strength (7.6 and 16.9 MPa, in absolute values). Finally, the G2− results were analysed as a function of transverse fibre reinforcement percentage and compared to transverse tensile fracture toughness results (G2+) determined in a previous work. This study showed that G2− is generally higher than G2+ and that the compressive-to-tensile ratio is inversely proportional to the transverse reinforcement percentage.

The gravity load simulator – Re-visited

A review of loading arrangements for lateral buckling tests on pultruded glass fibre reinforced polymer (GFRP) beams is presented. It is suggested that the Gravity Load Simulator (GLS), used for similar tests on steel beams could also be used for lateral buckling tests on GFRP beams and, moreover, it could be analysed and designed using exact calculations rather than the iterative method used more than 50 years ago. This conclusion is demonstrated by re-analysing the old iteratively designed GLS. The exact analysis is then used to analyse and design a new GLS for lateral buckling tests on pultruded GFRP beams. The new GLS was fabricated from aluminium bar and plate and details of its overall dimensions and layout and the types of bearings used in its pin joints are described. Thereafter, the test arrangement and instrumentation used to demonstrate the GLS’s accuracy, i.e. maintaining the horizontal translation of the jack’s base as the GLS sways in the lateral buckling plane, is presented. It is shown that the GLS performs extremely well and its use in laboratory testing is illustrated.