Glass Fiber Reinforced Polymer Panels Research Articles

Sustainable repurpose of end-of-life fiber reinforced polymer composites: A new circular pedestrian bridge concept

In response to global challenges in resource supply, many industries are adopting the principles of the Circular Economy (CE) to improve their resource acquisition strategies. This paper introduces an innovative approach to address the environmental impact of waste Glass Fiber Reinforced-Polymer (GFRP) pipes and panels by repurposing them to manufacture structural components for new bicycle and pedestrian bridges. The study covers the entire process, including conceptualization, analysis, design, and testing of a deck system, with a focus on the manufacturing process for a 7-m-long prototype bridge. The study shows promising results in the concept of a sandwich structure utilizing discarded GFRP pipes and panels, which has the flexibility to account for variabilities in dimensions of incoming products while still meeting mechanical requirements. The LCA analysis shows that the transportation of materials is the governing contributing factor. It was concluded that further development of this concept should be accompanied by a business model that considers the importance of the contributions from the whole value chain.

Characterization of material, mechanical, static bending and vibration properties of glass fiber composite panels reinforced with graphene nanofillers

The present study investigates the material, mechanical, static bending and vibration characteristics of glass fiber reinforced polymer (GFRP) composites reinforced with graphene nanofillers. The crystallinity, functional groups, morphology, and tensile and flexural strengths of GFRP and graphene reinforced GFRP composites were examined using a variety of material and mechanical characterization techniques, including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and tensile and flexural tests. The first-order shear deformation theory (FSDT) based finite element (FE) model was developed to obtain the static bending and vibration characteristics of the graphene reinforced GFRP composite panels. The validity of the FE model is verified with numerical data published in the literature. Further research is conducted into the effects of the wt% of graphene, end conditions, curvature ratio, and aspect ratio on the static bending and vibration characteristics of graphene reinforced GFRP panels. The findings of this study indicate that graphene reinforced GFRP panels could be utilized in a variety of applications, particularly for parts used in the aerospace and automotive industries.

Design, fabrication, and construction of a freeform GFRP facade

ABSTRACT This paper demonstrates the application method of GFRP (glass fibre reinforced polymer) on freeform facades, including the design, fabrication, and construction based on an architectural oddment in Fuzhou. This architectural oddment, which covers a sunken plaza, is a sculptural-shaped structure inspired by three-morning glories, and its freeform facade is made up of 4 mm-thick GFRP panels. It is the first all-GFRP structure in China. Based on the construction plan adopted in this project, the final architectural aesthetics satisfy the original expectations of the design, indicating that GFRP panels can perform well as facade components. On the other hand, certain defects highlight problems for further investigation. The benefits and limitations of GFRP when applied on the freeform facade are discussed at the end of the paper, providing a reference for similar architectures.

Influence of Loading Direction on Impact Strength and Small Span Length Variation on Flexural Strength in GFRP Laminate

Abstract This experimental work focuses on the two aspects of glass fiber–reinforced polymer (GFRP) laminate. The first is the effect of GFRP plate thickness and impact loading direction on impact strength, and the second is the effect of GFRP panel thickness and small span length variation on flexure strength. The GFRP laminate thicknesses considered for experimentation were 2, 3, and 4 mm. Both Izod and Charpy impact tests were conducted by considering edgewise (lateral impact) and flatwise (normal impact) impact loading directions. The quasistatic flexural tests were conducted using a three-point bend method for two small span length variations, viz., 50.8 and 56 mm. Impact strength of 2-mm-thick GFRP laminate under the edgewise loading condition showed 13 and 134.1 % more for Charpy and Izod, respectively, compared with 4-mm GFRP samples. In contrast, under the flatwise loading condition, 2-mm-thick specimens showed 14 and 54 % more impact strength when compared with 4-mm-thick GFRP specimens. GFRP samples with 2-mm thickness showed 59.85 and 59.6 % enhancement in flexural strength for span lengths of 56 and 50.8 mm, respectively, when compared with 4-mm-thick GFRP panels. Improvement in flexural strength between span lengths 50.8 and 56 mm for thicknesses 4 and 2 mm is 26 and 42 MPa, respectively, which is a 10 % improvement. Analysis of variance statistical analysis showed that the loading conditions and thickness of GFRP panels in the case of impact and small span length variation, and thicknesses in the case of flexural strength, is the significantly influencing parameters.

Bi-axial behaviours of abraded and rehabilitated FRP decks as anisotropic plates under concentrated wheel loading

For in-service GFRP (glass fibre-reinforced polymer) cellular bridge decks, wheel loads can induce damage of the anti-skid surfacing-to-deck bond, thereby loosening fragments of surfacing that then cause abrasion of the deck’s top flange under further wheel loads. Indeed, over the last 20 years, wheel load-induced damage to the top flanges of FRP decks on the road network has been observed in different countries, after periods in service ranging from a few days to a few years, due to inadequate design. Bonding of uni-directional GFRP panels to the abraded multi-directional flange constitutes a potentially effective rehabilitation strategy, but it also influences the deck’s local wheel-load response by altering the anisotropy of the top flange. The present paper uses an experimental-numerical study to explore this role of anisotropy for both abraded and rehabilitated decks. The experiments captured the top flanges’ peak biaxial strains, using gauges installed on the flange soffits to avoid damage by the wheels. The numerical model captures the morphology of the deck, the actual spread of the tyre load over the contact zone and spatial variations in anisotropy of the abraded or built-up flanges and of the webs. The results show that the uni-axially dominated rehabilitation strategy strongly improves bi-axial response to static wheel loads. The numerical model encouragingly predicts the bi-axial strains for each of the abraded and rehabilitated decks, and reliably predicts the strain reductions due to rehabilitation. Refined meshes along the tyre-loaded local flange span, with coarser meshes in adjacent spans, enable these reasonable predictions of response. It is concluded that top flange soffit gauges installed via ad-hoc tooling inserted through holes in the bottom flange, in tandem with rigorous numerical modelling, constitutes an effective two-pronged approach for elucidating wheel load effects.

Sandwich assemblies of composites square hollow sections and thin-walled panels in compression

Abstract Sandwich structures were built up by two glass fibre reinforced polymer (GFRP) thin-walled panels and square hollow sections (SHS) in between through adhesive bonding or mechanical bolting. Experiments in compression were conducted in order to understand the failure modes including global and local buckling, load-bearing capacities, load-displacement curves and load-strain responses. Accordingly the effects of different connection methods and different spacing values between the SHS sections were clarified. Sudden debonding failure between GFRP panels and inner SHS columns was found on adhesively bonded specimens; while mechanically bolted specimens showed evident lateral deformation and progressive failure until the ultimate junction separation failure on the GFRP SHS columns. Local buckling was found on GFRP thin-walled panels of specimens with a larger spacing between the two SHS sections. Finite element analysis and analytical modelling were performed to estimate the load-displacement curves and the critical stress for the local buckling on GFRP thin-walled panels, where consistent agreements with experimental results were received.

Blast responses of pultruded GFRP fluted-core sandwich panels: Testing and analyzing

Abstract Pultruded glass fiber reinforced polymer (GFRP) fluted-core sandwich panel is easily made and may be a lightweight construction for protective structures. Blast resistance of the GFRP fluted-core sandwich panels are investigated by explosion testing. In current research, when the scaled distance is larger than 1.494 m/kg1/3, the panel exhibits excellent anti-blast ability without any damage. Decreasing the scaled distance to 1.357 m/kg1/3, fluted-core shear damage is observed. Decreasing the scaled distance to 1.186 m/kg1/3, fluted-core shear damage and dense longitudinal cracks at front face are observed. Longitudinal cracks are caused by the anisotropy of the pultruded GFRP panels and the local shock wave impact on the mono-cell panels of the front face. Damage degree is investigated quantitively through static three-point bending experiments. Equivalent static load method is developed to predict the damage mode and decide the permitted blast wave the panel can sustain. To improve the anti-blast ability of the pultruded GFRP fluted-core sandwich panel, the core density and the transverse strength of the GFRP should be strengthened.

Low-velocity impact responses and CAI properties of synthetic foam sandwiches

This paper presents experimental and analytical studies on impact and compression after impact (CAI) responses of sandwiches with glass fiber reinforced polymer (GFRP) skins and synthetic foam cores under low-velocity impacting. The impact test results showed that the penetration depth of GFRP panels with synthetic foam is much smaller than that of bare synthetic foam panels. The edgewise compression test results indicated the facesheet debonding dominates the failure mode of the sandwich panels without lattice webs, while the failure mode of the sandwich panels with lattice webs is predominated by the wrinkling and delamination of the facesheets and the crushing of foam core. The influences of applied impact energy, GFRP lay-up, synthetic foam density and the existence of webs on the impact and post impact behavior of sandwich panels are discussed herein. Analytical models are proposed to predict the residual ultimate edgewise compressive load capacity of sandwich panels with lattice webs after impacts, using energy principles and variational methods in applied mechanics. The influences from impact damage, the local buckling of the facesheets and the confined strength of the foam core are measured and compared well with proposed analytical models.

Mechanical and Fracture Properties of Steel/GFRP Hybrid Panels for an Improved Moveable Weir after Exposure to Accelerated Natural Environmental Conditions

This study evaluated the performance of a hybrid panel in an improved moveable weir after exposure to accelerated environmental climate conditions. When exposed to a river environment, corrosion problems on improved moveable weir steel panels can occur. To address this, a hybrid panel with structure layering glass fiber-reinforced polymer (GFRP) panels on both sides of the steel panel was used. The steel was, therefore, not exposed to the outside. However, this hybrid panel is a structure that uses a mixture of two materials with different properties and there is the possibility of performance degradation when the GFRP composite material, i.e., the structure that wraps around the bond interface, and the steel panel are exposed to a river environment. Thus, we evaluated the durability of the hybrid panels by repeated exposure to long-term high temperatures, dry–wet environmental cycling, long-term freezing, and freeze–thaw cycling in an accelerated climate deterioration environment. In the flexural tests, the surface processing of the steel panel was shown to be important, with sand-blasted test specimens showing higher flexural strength. For the control specimens, the flexural strength decreased as the thickness of the GFRP panels increased. However, for the sand-blasted specimens, the flexural strength increased as the thickness of the GFRP panels increased. After exposure to accelerated climate deterioration, the flexural strength tests showed that the residual strength increased with panel thickness and that the residual strengths were greater for specimens incorporating sand-blasted steel panels. The results of our testing show that hybrid panels incorporating sand-blasted steel were adequate for use in improved moveable weirs.

Ballistic impact behaviour of glass fibre reinforced polymer composite with 1D/2D nanomodified epoxy matrices

In this paper, experimental studies on the ballistic impact behaviour of nanomodified glass fibre-reinforced polymer (GFRP) are reported. The epoxy matrix of the GFRP was modified by the addition of graphene platelets (GNPs), carbon nanotubes (CNTs), combined hybrid hexagonal boron nitride nanosheets (BNNS)/CNT, and combined boron nitride nanotubes (BNNTs)/GNPs nanoparticles.Ballistic impact tests were carried out on GFRP laminates at two projectile velocities of 76 ± 1 m s−1 for full-field deformation measurements and 134.3 ± 1.7 m s−1 for perforation tests. The behaviour of the plates during impact was recorded using digital image correlation (DIC), in order to monitor strain and out-of-plane deformation in panels with nanoreinforced matrices. Following penetrative impact tests, pulse thermography was used to characterise the delamination of impacted plates. The results of full-field deformation, exit velocity and energy absorption measurements from the ballistic tests show significant improvements in impact resistance for the panels made from nanomodified epoxies relative to laminates with the unmodified epoxy matrix. The highest absolute absorbed energy was observed for the GFRP panels fabricated using the epoxy matrix loaded with BNNT/GNP at 255.7 J, 16.8% higher than the unmodified epoxy matrix.

Static and fatigue load performance of a pultruded GFRP deck panel reinforced with steel wires

This paper presents an experimental study of the quasi-static and fatigue load performance of a pultruded GFRP (glass fiber-reinforced polymer) deck panel that can be used to furnish the roadway surface of temporary detour bridges. The flanges of the GFRP deck panel were reinforced with uniformly spaced steel wires to increase the flexural stiffness of the panel. A total of nine full size GFRP deck panel specimens were tested under static and fatigue loadings. The load-deflection behavior and ultimate strength of the deck specimens were compared with those of the unreinforced specimens. The test results were also compared with the results of finite element analysis. The steel reinforcement of the steel reinforced GFRP panels was only 2.5% of the cross-sectional area of the GFRP composite. The test results indicated that, at the design load level, the flexural stiffness of the steel reinforced GFRP panels was approximately 12.3% greater than that of the unreinforced GFRP panels. The test results further revealed that the fatigue loading up to 120% of the design load did not influence the stiffness of the steel reinforced GFRP deck panel.

Blast resilience of composite sandwich panels with hybrid glass-fibre and carbon-fibre skins

The development of composite materials through hybridisation is receiving a lot of interest; due to the multiple benefits, this may bring to many industries. These benefits include decreased brittle behaviour, which is an inherent weakness for composite materials, and the enhancement of mechanical properties due to the hybrid effect, such as tensile and flexural strength. The effect of implementing hybrid composites as skins on composite sandwich panels is not well understood under high strain rate loading, including blast loading. This paper investigates the blast resilience of two types of hybrid composite sandwich panel against a full-scale explosive charge. Two hybrid composite sandwich panels were mounted at a 15 m stand-off distance from a 100 kg nitromethane charge. The samples were designed to reveal whether the fabric layup order of the skins influences blast response. Deflection of the sandwich panels was recorded using high-speed 3D digital image correlation (DIC) during the blast. It was concluded that the combination of glass-fibre reinforced polymer (GFRP) and carbon-fibre reinforced polymer (CFRP) layers in hybrid laminate skins of sandwich panels decreases the normalised deflection compared to both GFRP and CFRP panels by up to 41 and 23%, respectively. The position of the glass-fibre and carbon-fibre layers does not appear to affect the sandwich panel deflection and strain. A finite element model has successfully been developed to predict the elastic response of a hybrid panel under air blast loading. The difference between the maximum central displacement of the experimental data and numerical simulation was ca. 5% for the hybrid panel evaluated.

Damage and wave propagation characteristics in thin GFRP panels subjected to impact by steel balls at relatively low-velocities

An experimental investigation was conducted to determine the damage and wave propagation characteristics in Glass Fibre Reinforced Polymer (GFRP) panels subjected to impact by steel balls at relatively low-velocities up to 91 ms−1. While maintaining the same impact energy level, the influence of ball mass on panel response was studied. The effects of composite lay-up sequence and successive impacts were also investigated. The wave propagation characteristics, including wave types, wave velocities, wave attenuations, and strain rates, were extracted from dynamic strain records measured at various locations on the panels. The results showed that, for the same level of impact energy, the small ball mass produced larger deformation and delamination than the large ball mass. Additionally, the resistance to impact was influenced by the composite lay-up sequence of similar fibre weight fraction. Test panels subjected to successive impacts showed an increase in cumulative delamination areas, whereas the tests indicated that successive impacts had a little effect on the perforation limit of the test panels. The impact velocity showed a pronounced influence on the measured peak strains and strain rates. The flexural wave was the predominant wave system, propagating at different velocities in different directions. In proximity to the impact site, both flexural wave and indentation predominated over the transient response. In addition to the flexural wave, impact induced low amplitude tensile longitudinal waves of high velocity.

Testing and Evaluation of Polyurethane-Based GFRP Sandwich Bridge Deck Panels with Polyurethane Foam Core

AbstractThis paper presents the evaluation of an innovative low-cost small-scale prototype deck panel under monotonic and fatigue bending. This new system introduces a trapezoidal-shaped polyurethane foam core with a thermoset polyurethane resin that has a longer pot life to facilitate the infusion process. The proposed panel exhibited a higher structural performance in terms of flexural stiffness, strength, and shear stiffness. The panels consist of two glass fiber–reinforced polymer (GFRP) facings with webs of bidirectional E-glass–woven fabric that are separated by a trapezoidal-shaped low-density polyurethane foam. The GFRP panels were manufactured using a one-step vacuum-assisted resin transfer molding process. The specimens studied were constructed in the Composite Manufacturing Laboratory in the Mechanical and Aerospace Engineering Department at Missouri University of Science and Technology. Small-scale prototype deck panels were tested both statically and dynamically in four-point bending to inves...

Thermal Field Distributions of Girder Bridges with GFRP Panel Deck versus Concrete Deck

Temperature effects have always been considered to be one of the critical issues that affect the performance of traditional concrete and steel bridges. Currently, glass fiber-reinforced polymer (GFRP) composite panels, with the advantages of high strength, light weight, good corrosion resistance, long-term durability, etc., have been applied to slab replacements in bridge engineering. The thermal behaviors of these GFRP bridges, however, have not been fully understood. More specifically, the current temperature design specifications in the AASHTO LRFD may no longer be valid for GFRP bridges. Therefore, this paper presents the thermal field distribution behaviors through studying an as-built bridge with GFRP sandwich panels. First, a transient-state numerical modeling method is proposed. This method is capable of predicting the temperature field of a GFRP bridge based on local environmental conditions. Then, a parametric study is conducted to analyze the thermal responses of bridges with different structure combinations (i.e., GFRP panels, concrete slabs, concrete beams, and steel girders). The mechanical and physical properties of GFRP panels are predicted using the micro-macro mechanics theory and validated by a field measurement and an experimental study. Based on the results from the present study, the temperature distribution patterns for GFRP panel bridges are proposed, referring to the available AASHTO LRFD sign code. The thermal strains and stresses caused by temperature gradients along the depth of bridge superstructures are examined.

Thermal behaviors of concrete and steel bridges after slab replacements with GFRP honeycomb sandwich panels

During the last several decades, fiber-reinforced polymer (FRP) panels have been applied as one of the alternatives for slab retrofits and replacements in bridge engineering. Even though with many benefits, e.g., high strength, light weight, long-term durability, and good corrosion resistance, the FRP structures have not been widely adopted. It is partly due to the lack of national design guidelines and the uncertainties on long-term performances. Many studies have been conducted to investigate the static and dynamic performances of FRP bridges, while the studies on their thermal responses are not adequate. Therefore, the present study demonstrates an investigation on the thermal behavior of a FRP bridge based on a slab replacement project conducted by the Kansas State Department of Transportation, i.e., a steel deck replaced by glass FRP (GFRP) panels. The temperatures of the bridge and ambient air are recorded from December 2002 to July 2004. Firstly, a finite element model is developed using a sub-structuring method. This method is particularly efficient for modeling structures with complex configurations and subjected to the traffic and temperature loadings. Then, the model is verified by comparing the predicted live load distribution factors with that of a live load test; and it is further adopted to study the thermal responses using the measured temperatures from January 24 to July 13 in 2004. Finally, a parametric study is performed to study two general slab replacement cases, i.e., bridges with concrete beams and steel girders, respectively. Different loading conditions are considered, including the uniform temperature variations, temperature gradients, self-weights, and HS-20 live loads. Results from this study indicate that careful attentions should be paid to the thermal responses of bridges. The temperature gradients and uniform variations evidently affect the performance of bridges after replacing the concrete slabs with GFRP panels, such as the induced vertical deflections, horizontal movements, and stresses of steel girders or concrete beams.

Modelling the behaviour of composite sandwich structures when subject to air-blast loading

Large-scale glass fibre reinforced polymer (GFRP) and carbon fibre reinforced polymer (CFRP) sandwich structures (1.6 m x 1.3 m) were subject to explosive air blast (100 kg TNT equivalent) at stand-off distances of 14 m. Digital image correlation (DIC) was used to obtain full-field data for the rear-face of each deforming target. A steel plate of comparable mass per unit area was also subjected to the same blast conditions for comparison. The experimental data was then verified with finite element models generated in Abaqus/Explicit. Close agreement was obtained between the numerical and experimental results, confirming that the CFRP panels had a superior blast performance to the GFRP panels. Moreover all composite targets sustained localised failures (that were more severe in the GFRP targets) but retained their original shape post blast. The rear-skins remained intact for each composite target with core shear failure present.

Structural GFRP Permanent Forms with T-Shape Ribs for Bridge Decks Supported by Precast Concrete Girders

A new concrete bridge deck cast onto glass fiber–reinforced polymer (GFRP) stay-in-place (SIP) structural forms is studied. The forms, which replace the bottom layer of conventional rebar, are essentially flat plates with T-up ribs. They span between support girders spaced at 1,772 mm and are lap-spliced using adhesive and mechanical fasteners. Special attention was given to the detailing of monolithic connections between the deck and girders to simulate continuity. The flange of the supporting concrete girders had a rough surface finish and protruded steel stirrups and mimicked AASHTO Type III girders. Five full-scale decks were tested to (1) compare the novel system with a conventional RC deck, (2) examine the effect of eliminating a top layer of orthogonal GFRP rebar, (3) assess a practice commonly used in bridge deck tests of using simple spans resting on neoprene pads, neglecting connection to girders, and (4) examine a commercially available all-GFRP deck, using the same GFRP panels but with a top GFRP plate fastened to the T-up ribs. Four auxiliary flexural specimens were tested to examine the lap-splice. The concrete deck with GFRP SIP form showed 33% higher strength than the conventional RC deck. It also achieved a peak load 7.8 times higher than the service load plus impact. Deflection under the service load was less than span/1,600. Remarkable deformability and pseudoductility was achieved at ultimate load, beyond punching shear, because of the progressive failure of the lap-splice. The simply supported deck failed at a slightly lower strength than the monolithically cast one but had a much lower stiffness.

Thermal Compatibility and Durability of Wearing Surfaces on GFRP Bridge Decks

The paper investigates thermal compatibility between wearing surface (WS) materials and glass fiber reinforced polymer (GFRP) bridge decks, and proposes a more durable hybrid WS system for GFRP decks. Wearing surface delamination problems observed on many existing GFRP bridge decks motivated the investigation and the search for a durable WS material that could alleviate the problems. Several WS materials were bonded to GFRP panels, with and without surface preparation, and tested under various environmental conditions. In addition to the standard ASTM C884 method, the testing program included two new methods for thermal compatibility testing to reflect the in-service conditions of WSs on GFRP bridge decks. The proposed methods were developed to account for the influence of freeze–thaw–heat and submerge–freeze cycles on thermal compatibility and durability. The investigation concluded that a hybrid WS system, consisting of two-layered WS materials, has the best bond quality. Applied directly on top of a GFRP deck, the top layer of the hybrid WS system had the best tire resistance, forming a nonskid riding surface.