Pultruded Glass Fiber-reinforced Polymer Profiles Research Articles

Non-uniform fiber-resin distributions of pultruded GFRP profiles

Pultruded fiber reinforced polymer (FRP) composite profiles are usually regarded as the transverse-isotropic material based on the assumption that the fiber and resin are uniformly distributed across the profile sections. However, this is practically not the case due to the limitations of the pultrusion technology. The non-uniform fiber-resin distribution (NUFRD), as a type of inherent initial imperfection for pultruded glass fiber reinforced polymer (GFRP) profiles, was investigated. The resin contents of 49 different pultruded GFRP sections were tested and analyzed. The standard calcination method was used to measure the resin content. The sections were provided by three different manufactures and included the I-sections, box-sections, angle-sections, circular tubes, channel-sections and flat plates. Multiple sampling locations were specified for each type of section. The test results showed that the degree of NUFRD for each type of section is different. In particular, the I-sections showed the most significant material non-uniformity. The largest COV (coefficient of variation) of the measured resin contents is 0.16. Additionally, the influence of NUFRD on the mechanical properties of GFRP members was addressed. The material non-uniformity would increase the initial section eccentricity. Finite element models were built to simulate the compressive GFRP members. It was found that the critical buckling loads of GFRP compressive members will be reduced due to NUFRD.

An Efficient Approach to Describe the Fiber Effect on Mechanical Performance of Pultruded GFRP Profiles

This study focuses on the flexural behavior of pultruded glass fiber-reinforced polymer (GFRP) profiles developed for structural applications. Fiber content is a commonly accepted measure for estimating the resistance of such components, and technical datasheets describe this essential parameter. However, its direct implementation to the numerical simulations can face substantial problems because of the limitations of standard test protocols. Furthermore, the fiber mass percentage understandable for producers is unsuitable for typical software considered the volumetric reinforcement content. This manuscript exemplifies the above situation both experimentally and analytically, investigating two GFRP square hollow section (SHS) profiles available at the market. A three-point bending test determines the mechanical performance of the profiles in this experimental program; a digital image correlation system captures deformations and failure mechanisms of the SHS specimens; a standard tensile test defines the material properties. A simplified finite element (FE) model is developed based on the smeared reinforcement concept to predict the stiffness and load-bearing capacity of the profiles. An efficient balance between the prediction accuracy and computation time characterizes the developed FE approach that does not require specific descriptions of reinforcement geometry and refined meshes necessary for modeling the discrete fibers. The proposed FE approach is also used to analyze the fiber efficiency in reinforcing the polymer matrix. The efficiency is understood as the model’s ability to resist mechanical load proportional to the dry filaments’ content and experimental elastic modulus value. Scanning electron microscopy relates the composite microstructure and the mechanical performance of the selected profiles in this study.

The effect of elevated temperatures on the compressive section capacity of pultruded GFRP profiles

The compressive performance of glass fiber reinforced polymer (GFRP) profiles subjected to elevated temperature was investigated through a large number of (3 0 0) tests. The effects of profile cross-sectional area, slenderness, and temperature on the behavior of the GFRP profiles at temperatures ranging from 25 to 400 °C were determined. It was observed that the compressive strength of the GFRP profiles has been decreased by half as the temperature exceeded 90 °C, i.e., close to the glass transition temperature of the matrix. The temperature and ratio of cross-sectional area to external perimeter were determined as two major parameters affecting section capacity.

Compressive Behavior of Concrete Filled Glass Fiber Reinforced Polymer (GFRP) Box Profiles

The use of concrete filled fiber reinforced polymer (FRP) profiles for beams and columns has been studied extensively in recent years. Glass Fiber Reinforced polymers (GFRP) profiles are one of these materials. GFRP box profiles serve as formwork, and provide shear and flexural reinforcement in novel hybrid GFRP–concrete structural system. GFRP box profiles also protect the concrete and increase the strength of hybrid materials. This study presents results of an experimental study using concrete filled pultruded GFRP profiles. A series of compression tests were carried out to study the compression behavior of the proposed hybrid GFRP-concrete materials. Hybrid compression samples were fabricated and tested in three different strength classes. The results showed that compressive strength of hybrid material significantly increased when compared to reference samples.

Member Capacity of Pultruded GFRP Tubular Profile with Bolted Sleeve Joints for Assembly of Latticed Structures

AbstractThe use of bolted sleeve joints has been proposed for assembling pultruded glass fiber-reinforced polymer (GFRP) tubular profiles into space lattice shell structures. Such joint configurations may introduce a semi-rigid end condition and further affect the capacity of the connecting members in compression. Three batches of specimens assembled with pultruded GFRP profiles of different lengths and bolted sleeve joints at both ends were prepared and tested under static axial compression. A detailed three-dimensional finite element model considering bolt geometry, contact behavior, bolt pretension, initial geometric imperfection, and failure criterion for fiber-reinforced polymer (FRP) composites was developed and validated with experimental results showing good comparisons. It was found that the bolted sleeve joints exhibited semi-rigid behavior and that the failure modes and the effective length factor were dependent on member slenderness. The relationship between effective length factor and member ...

Effects of corrosive environments on properties of pultruded GFRP plates

Glass Fiber Reinforced Polymer (GFRP) composites have low permeability and high corrosion resistance. In recent years, as the use of GFRP in applications requiring high corrosion resistance has gradually expanded, its long-term performance in highly corrosive environments has caught public attention worldwide. Nevertheless, there is only limited theoretical research and accumulated test data on the corrosion resistance of GFRP. This paper analyses the long-term performance of GFRP in highly corrosive environments. Samples cut from pultruded GFRP profiles were exposed to alkaline, saline, and acidic solutions of different concentrations at 60°C. Additionally, the effects of acidic solutions at high temperature (90°C) were investigated. Flexural properties, changes in the flexural fracture mechanism, hardness, the rate of weight gain, changes in appearance, and scanning electron microscopy (SEM) images of fracture sections were analyzed over periods of 7, 15, 30 and 90days. Results indicate that flexural strength decreases with increased exposure time to both acidic and alkaline solutions. Under conditions of high concentration acidity and high temperature acidity, respectively, flexural strength decreases even more drastically. Additionally, it was found that saturated NaCl solution has little effect on GFRP.

Experimental Investigation of the Behavior of a Lattice Steel Column Repaired with Pultruded GFRP Profiles

AbstractIn this paper, a series of joint tests and full-scale structural tests were performed to assess the effectiveness of pultruded glass fiber-reinforced polymer (GFRP) profiles for rehabilitating lattice steel columns. The data for the displacements and strains of typical members were recorded. The experimental results showed that the failure modes are generally identical for the original column, the column restored using angles, and the column that adopted the stiffer GFRP-to-steel bolted joints (using steel cover plates, bolts, and nuts) repaired with pultruded GFRP sections. In contrast, the failure pattern of the column that used the ordinary GFRP-to-steel bolted joints (only using bolts and nuts) was not the same. Additionally, the ultimate strength of the specimen that employed the stiffer GFRP-to-steel connections was slightly higher than that of the specimen retrofitted by angles, and the ultimate capacity of the sample that adopted the ordinary GFRP-to-steel connections was significantly low...

Novel Joint for Assembly of All-Composite Space Truss Structures: Conceptual Design and Preliminary Study

A space truss is formed of interconnected structural components that transfer loads axially. Pultruded glass-fiber reinforced polymer (GFRP) composites exhibit their best material strength in the axial (pultrusion) direction, and their inherent lack of material stiffness can be compensated by the structural stiffness achieved by space configuration. A novel connector made of pultruded GFRP profiles is proposed in this paper to join diagonal and chord members and to form all-composite free-form space trusses. The proposed truss unit was assembled and tested statically, and the load-displacement responses were recorded. The final collapse of the structural unit evidenced a pull-out shear failure mode in the bolt connections, and the ultimate load can therefore bewell predicted by this mechanism. A detailed finite element (FE) analysis considering the interaction between the bolts and FRP profiles was conducted for the structural unit to investigate the effects of pretension force of bolted connections and the stress concentration at the joint region. A simplified FE approach was used to demonstrate one- and two-dimensional space trusses with satisfactory structural stiffnesses. DOI: 10.1061/(ASCE)CC.1943-5614 .0000304. © 2013 American Society of Civil Engineers. CE Database subject headings: Space truss; Fiber reinforced polymer; Pultrusion; Joints; Stiffness; Serviceability. Author keywords: Space truss; Glass-fiber reinforced polymer; Pultrusion; Joints; Stiffness; Serviceability.

Fire protection systems for building floors made of pultruded GFRP profiles – Part 2: Modeling of thermomechanical responses

A recently developed thermomechanical model to predict the time-dependent thermal and mechanical responses of pultruded glass fiber-reinforced polymer (GFRP) profiles subjected to fire was extended to include the beneficial effects of passive fire protection systems. The model extension was validated by comparing predicted and measured thermomechanical responses of pultruded GFRP tubes subjected to four-point bending and exposed to an ISO834 fire from their underside. The profiles were protected using passive and active methods, including a calcium silicate board, a vermiculite/perlite-based mortar, and a water-cooling system. Variations resulted mainly from the unavailability of accurate time-dependent thermophysical properties for the protection materials. The benefits provided by the fire protection systems could be quantified and the model therefore can be used for the selection and design of passive fire protection measures.

Shear Failure of Pultruded Fiber-Reinforced Polymer Composites under Axial Compression

When structural elements are subjected to compressive loads, the shear forces and stresses induced by second-order effects may lead to shear failure prior to compressive failure. This is particularly likely to occur in the case of pultruded glass fiber-reinforced polymer profiles, which normally exhibit low shear strength in relation to compressive strength. This paper analyzes the effects of initial imperfection, slenderness, shear-to-compressive strength ratio, shear coefficient, and type of shear failure criterion on ultimate load and failure mode (shear or compressive failure). A formulation for predicting ultimate load based on shear failure and second-order deformation is proposed. The results obtained compare well with similar results obtained using other methods and experimental data available in literature. The proposed method is based strictly on mechanics and thus requires no fitting to experimental data.