Application Of Fiber Reinforced Polymer Research Articles

A design methodology for fiber layup optimization of filament wound structural components

The applications of fiber-reinforced polymer (FRP) composites extend rapidly along with the development of new manufacturing techniques. However, due to the complexities introduced by the material and fabrication processes, the application of conventional structural design methods for construction members has been significantly challenging. This paper presents an alternative methodology to find optimum fiber layups for a given tube-shape geometry via a graphical optimization strategy based on structural performance requirements. The proposed technique employs simplified shell element models based on classical lamination theory (CLT) to avoid explicit fiber modeling in the FEA simulations. Lamination parameters are utilized to generate the reduced stiffness matrices for continuous multi-layer FRP lamination. The fiber layup of the component is retrieved from the optimal lamination parameters that maximize the structural performance. The case study results demonstrate that the developed method provides compact solutions, linking the structural design requirements with optimal fiber orientations and volumetric proportions. In addition, the determined solutions can be interpreted directly by the winding fabrication settings.

Bond between Fibre-Reinforced Polymer Tubes and Sea Water Sea Sand Concrete: Mechanisms and Effective Parameters: Critical Overview and Discussion

Using fibre-reinforced polymers (FRP) in construction avoids corrosion issues associated with the use of traditional steel reinforcement, while seawater and sea sand concrete (SWSSC) reduces environmental issues and resource shortages caused by the production of traditional concrete. The paper gives an overview of the current research on the bond performance between FRP tube and concrete with particular focus on SWSSC. The review follows a thematic broad-to-narrow approach. It reflects on the current research around the significance and application of FRP and SWSSC and discusses important issues around the bond strength and cyclic behaviour of tubular composites. A review of recent studies of bond strength between FRP and concrete and steel and concrete under static or cyclic loading using pushout tests is presented. In addition, the influence of different parameters on the pushout test results are summarised. Finally, recommendations for future studies are proposed.

Enhanced interlaminar fracture toughness of woven carbon fabric/epoxy composites by interleaving fluffy CNT veils

While fiber reinforced polymer (FRP) composites are widely utilized in structural components due to their favorable mechanical properties, delamination between reinforcing plies remains a major problem, weakening the composite structure and limiting more widespread applications of FRPs. Carbon nanotubes (CNTs) carry the promise of enhancing this poor out-of-plane mechanical performance, although their integration has been challenging. In this work, macroscopic CNT veils with controlled nano-meso structure were drawn from the gas-phase using a semi-industrial process and then integrated into woven carbon fiber/epoxy matrix composites utilizing a facile and scalable approach. Interlaminar fracture toughness (ILFT) of the resulting composites was determined in Mode-I (opening mode) test. Additionally, crack propagation and interlaminar toughening mechanisms were systematically analyzed by means of optical microscope, SEM, and Raman analysis. The results showed that mode I ILFT was improved as much as 60% when interleaving as-received fluffy CNT veils and also revealed that interlaminar crossing between CNT veil/CF interfaces is of paramount importance in toughening mechanism.

Comparative analysis of design guidelines for FRP contribution to shear capacity of strengthened RC beams

In the past few years, strengthening and retrofitting of reinforced concrete (RC) structures using externally bonded (EB) fiber-reinforced polymers (FRP) laminates has been deemed as a promising rehabilitation technique. Structural applications of FRP include flexural and shear strengthening of RC beams and confinement of columns. Many guidelines and standards were developed to predict the contribution of FRP to the strength of structural members. For shear strengthening applications, in particular, most of the design guidelines tend to underestimate the capacity of the strengthened members, whereas other models provide unsafe predictions. The accuracy of the models is dependent on many factors, such as but not limited to the wrapping scheme, amount of internal shear reinforcement, shear crack angle, concrete compressive strength, number of FRP layers, and FRP type. For this purpose, this paper focuses on comparing and evaluating the accuracy of the available FRP shear design guidelines. The design standards that are considered in this study are the ACI440.2R-17, CSA-S806.12 (R2017), fib bulletin 90, and TR55. The accuracy of the design models was assessed against an experimental database collected from the literature. The database included RC beams externally strengthened in shear with different FRP types, configurations, and wrapping schemes. In addition, the database included strengthened beams with varying types of anchors. Results showed that most design codes provide reasonable predictions to the FRP shear strength in case of U-wraps. However, the guidelines are significantly conservative in case of complete wraps and anchored specimens. Overall, the ACI440.2R-17 and TR55 predictions are very conservative while fib bulletin 90 and CSA-S806.12 predictions are accurate and can be safely used to design FRP shear strengthened members.

A Review on the Mechanical Properties of Fiber-Reinforced Polymer Composites and their Application in the Transportation Industry

The application of fiber-reinforced polymer (FRP) composites has achieved significant attention in the industry of transportation, specifically as metal substitutes due to a need for fabricating stable and fuel-efficient airplanes, vehicles, and ships. Excellent strength, resistance to corrosion, lightweight, and suitable fatigue endurance are some of the desirable properties that would encourage the use of FRP composites in the transportation sector. Polymer-based composite materials, combining the favorable properties of both polymer matrix and reinforcing fibers, can contribute to several excellent behaviors of the obtained material. Epoxy, polyethylene, and polypropylene are the primary polymer matrices used in FRP composites. The main reinforcing fibers incorporated in fiber-reinforced composites are made out of glass, carbon, basalt, hemp, or natural resources (e.g., sisal and jute). Due to high cost, low Young's modulus, low durability, and linear stress?strain behavior to failure of the FRP materials, which are used in transportation infrastructure, the objective of this review article is to study the recent aspect of reinforced polymers with a close focus on their mechanical properties in order to evaluate their application in maritime, automotive, and aerospace.

Maintenance and Inspection of Fiber-Reinforced Polymer (FRP) Bridges: A Review of Methods.

Fiber-reinforced polymers (FRPs) are materials that comprise high-strength continuous fibers and resin polymer, and the resins comprise a matrix in which the fibers are embedded. As the technique of FRP production has advanced, FRPs have attained many incomparable advantages over traditional building materials such as concrete and steel, and thus they play a significant role in the strengthening and retrofitting of concrete structures. Bridges that are built out of FRPs have been widely used in overpasses of highways, railways and streets. However, damages in FRP bridges are inevitable due to long-term static and dynamic loads. The health of these bridges is important. Here, we review the maintenance and inspection methods for FRP structures of bridges and analyze the advantages, shortcomings and costs of these methods. The results show that two categories of methods should be used sequentially. First, simple methods such as visual inspection, knock and dragging-chain methods are used to determine the potential damage, and then radiation, modal analysis and load experiments are used to determine the damage mode and degree. The application of FRP is far beyond the refurbishment, consolidation and construction of bridges, and these methods should be effective to maintain and inspect the other FRP structures.

Efficiency of prestressed concrete joist reinforced by CFRP: Experimentation and analytical verification

AbstractIn this paper, the bending behavior of prestressed concrete joists strengthened by fiber‐reinforced polymer (FRP) laminates is described. An experimental investigation on 18 large‐scale beams is conducted, allowing determination of the strengthening influence of FRP in the general behavior of prestressed joists. The mechanical parameters considered in the study are the ultimate and elastics loads and the deflection or initial stiffness of joists. The analytical verification is done to calculate the design load values of the floor system. The results indicate that the application of FRP laminates significantly increases the response of prestressed concrete joists.

Preliminary Investigation of an Approach to Improve Water Impermeability in Concrete with Externally Bonded FRP Systems

Good bond and water impermeability in fiber-reinforced polymer (FRP) bonded/coated systems are essential if the durability of FRP-rehabilitated concrete structures is to be ensured. In addition, water impermeability is required in some special FRP applications, such as the strengthening of underground water pipes. So far, there has been no method in the literature guaranteeing water impermeability in FRP strengthening works. This paper studies the feasibility of using a waterproof coating as the initial primer on cementitious materials before applying externally bonded FRP. In this preliminary investigation, by examining the two most important indicators (i.e., pull-off bond tests and water penetration tests), it was found that the use of an initial waterproof layer in the proposed FRP bonding system did not influence the pull-off bond strength but significantly improved the system's water impermeability. It is, therefore, suggested that an initial waterproof layer can be included in method statements for externally bonded FRP systems to upgrade the effectiveness and durability of FRP systems.

Compressive behaviour and modelling of CFRP-confined ultra-high performance concrete under cyclic loads

The application of fibre-reinforced polymer (FRP) composites to enhance the strength and deformability of confined concrete has attracted increasing interest. However, the confinement demand of concrete increases proportionally with its strength, resulting in higher confinement requirements for ultra-high performance concrete (UHPC). This paper presents an experimental study that investigated the compressive behaviour of confined UHPC with carbon FRP sheets under cyclic axial compression. A modelling study on the cyclic stress–strain response of FRP-confined UHPC was also performed. The influences of the confinement ratio and cyclic-loading mode on the stress–strain curve, plastic strain, stress deterioration ratio and secant modulus were analysed. The findings for the stress–strain behaviour of FRP-confined UHPC were compared to those of conventional concrete confined with FRP. Based on the interpretation of the test results from this study and a comprehensive assessment of cyclic stress–strain models developed for FRP-confined conventional concrete, a stress–strain model for FRP-confined UHPC under cyclic axial compression was proposed. The results show that the proposed model reasonably predicts the stress–strain responses of FRP-confined UHPC.

Review of Strain Rate Effects of Fiber-Reinforced Polymer Composites.

The application of fiber-reinforced polymer (FRP) composites is gaining increasing popularity in impact-resistant devices, automotives, biomedical devices and aircraft structures due to their high strength-to-weight ratios and their potential for impact energy absorption. Impact-induced high loading rates can result in significant changes of mechanical properties (e.g., elastic modulus and strength) before strain softening occurs and failure characteristics inside the strain localization zone (e.g., failure mechanisms and fracture energy) for fiber-reinforced polymer composites. In general, these phenomena are called the strain rate effects. The underlying mechanisms of the observed rate-dependent deformation and failure of composites take place among multiple length and time scales. The contributing mechanisms can be roughly classified as: the viscosity of composite constituents (polymer, fiber and interfaces), the rate-dependency of the fracture mechanisms, the inertia effects, the thermomechanical dissipation and the characteristic fracture time. Numerical models, including the viscosity type of constitutive models, rate-dependent cohesive zone models, enriched equation of motion and thermomechanical numerical models, are useful for a better understanding of these contributing factors of strain rate effects of FRP composites.

Durability of Externally Bonded Fiber-Reinforced Polymer Composites in Concrete Structures: A Critical Review.

Externally bonded fiber-reinforced polymer composites have been in use in civil infrastructure for decades, but their long-term performance is still difficult to predict due to many knowledge gaps in the understanding of degradation mechanisms. This paper summarizes critical durability issues associated with the application of fiber-reinforced polymer (FRP) composites for rehabilitation of concrete structures. A variety of factors that affect the longevity of FRP composites are discussed: installation, quality control, material selection, and environmental conditions. Critical review of design approaches currently used in various international design guidelines is presented to identify potential opportunities for refinement of design guidance with respect to durability. Interdisciplinary approaches that combine materials science and structural engineering are recognized as having potential to develop composites with improved durability.

Effect of Shape Modification on the Performance of Cfrp Confined Square Concrete Columns: A Review

Now a days fiber-reinforced polymer (FRP) confinement is one of the most important techniques used for the strengthening and repairing of concrete structures. In the case of columns, the square/rectangular columns show less effectiveness towards FRP confinement compared with circular columns due to their flat sides and sharp corners. So the strengthening of square/rectangular columns needs more attention than circular columns. The performance of square/rectangular columns can be improved by modifying the shape of columns before FRP wrapping. The researches show that varying the corner radius of non-circular columns improves the confinement area and thereby increase the confinement efficiency of FRP. Recently, curvilinearization technique was developed in which slightly curved sides are provided to existing square/rectangular sections before application of FRP. Circularization is also another shape modification method in which the existing square columns are modifying into circular sections by using segmental concrete covers before the FRP wrapping process. This paper mainly deals with these shape modification techniques in the carbon-fiber-reinforced polymer (CFRP) confined square columns.

Fiber Reinforced Polymer Composite as a Strengthening of Concrete Structures: A Review

For centuries, concrete is the main material most widely used in a building. The strength and durability of this material will decrease over time due to several factors that influence the mechanism of its structural characteristics. Although the compression strength is excellent, it is weak in tensile. Fiber reinforced polymer (FRP) composites are widely used as an alternative material to replace metal-based engineering materials. This material has properties such as lightweight products, low production costs, easy to form, high tensile and flexural strength, and elastic. The purpose of this review paper is to provide information about the application of FRP composites as reinforcement of concrete structures either as repairs or new structures. Initially, FRP composite materials were used as reinforcement structures for reinforced concrete column-beam joints. The resulting structure has increased the flexural ability due to the load given. The addition of natural fiber (jute) to concrete also increases in the hardness of concrete. Other investigations regarding the application of FRP composites in concrete to improve strength performance are discussed in this paper. Finally, the technique of wrapping FRP composites in concrete in an effort to improve the performance of the resulting structure is also discussed in the paper.

Bond Behavior of Cleaned Corroded Lap Spliced Beams Repaired with Carbon Fiber Reinforced Polymer Sheets and Partial Depth Repairs

The present research investigated the bond behavior of a cleaned corroded reinforcing bar repaired with a partial depth concrete repair and a partial depth concrete repair followed by the application of fiber-reinforced polymer (FRP) sheets. Twelve lap splice beams were cast and tested under static loading. The test variables considered were a partial depth repair with prepackaged self-consolidating concrete (SCC) for six lap splice beams and additional confinement with carbon fiber reinforced polymer (CFRP) sheets for another six beams. The test results for the repaired lap splice beams were compared with those for a monolithic lap splice beam. This research found that the average bond strength increased as the bar mass loss increased for all bonded lengths. The lap splice beams repaired with partial depth were able to repair concrete with similar properties to those of the monolithic concrete. However, they had higher concrete strength than the monolithic beams which showed a higher average bond strength than the monolithic lap splice beams. The beams confined with FRP sheets showed a rise in the bond strength and the equivalent slip by 34–49%, and 56–260% as compared to the unconfined beams, respectively.

Quasi-static and dynamic response of GFRP and BFRP bars under compression

The application of fiber-reinforced polymers (FRP) bars in the building industry has grown intensively over the years, due to their numerous advantages such as corrosion resistance. However, current guidelines in design codes disregard the contribution of FRP bars in compression. The need of investigation of compressive mechanical properties of FRP bars is important, while there is a lack of experimental tests under varying dynamic and quasi-static loading rates. The present paper aims to evaluate the compressive strength and failure modes of glass and basalt fiber-reinforced polymer (GFRP and BFRP) bars. A series of quasi-static and dynamic tests were performed on different FRP bar sizes. Dynamic tests were conducted using the drop hammer procedure and different loading rates were achieved through varying the weight of mass and height of fall. Results showed that GFRP bars attained higher compressive strengths than BFRP bars for the same loading conditions. GFRP bars exhibited compressive strength in the range of 300 MPa to 600 MPa while the maximum compressive strength of BFRP bars was 470 MPa. The increase in the bar diameter resulted in an increase in the compressive strength of most FRP bars. However, Some FRP bars showed different variation in their compressive strengths at high loading rates. Finite element (FE) models were also developed to simulate the FRP bars under dynamic tests by considering the orthotopic material nature of the FRP composites. The FE models were verified with the experiments and successfully described qualitatively the trends observed during the full-scale drop-hammer tests.

Experimental Study on One-Way BFRP Bar-Reinforced UHPC Slabs under Concentrated Load.

The application of fiber-reinforced polymer (FRP) bars and ultra-high performance concrete (UHPC) in the field of civil engineering is promising. An innovative FRP bar-reinforced UHPC short-ribbed bridge deck slab, with low self-weight and high structural performance, was proposed in this study. The behavior of one-way basalt FRP (BFRP) bar-reinforced UHPC slabs under concentrated load was experimentally investigated, and compared with that of a steel bar-reinforced UHPC slab. The ultimate capacity of the one-way BFRP bar-reinforced UHPC slab was 0.59 times that of the steel bar-reinforced UHPC slab, while its ductility was better. Increasing the reinforcement ratio and loading area was beneficial to the ductility of one-way BFRP bar-reinforced UHPC slabs. Moreover, the model proposed by EI-Gamal et al. was found to be suitable for evaluating the punching shear capacities of one-way BFRP bar-reinforced UHPC slabs. However, the model failed to consider the unique strain-hardening characteristics of UHPC, which led to conservative prediction.

FE stress analysis and prediction of the pull-out of FRP rods glued into glulam timber

ABSTRACT This paper focuses on the FE analysis of the mechanical behavior of glued composite fiber-reinforced polymer (FRP) rods into glulam timber, using a 3D-continuum damage mechanics. The application of FRP to the glulam timber beams, despite the fact of limited investigations to date, offers an interesting and economic solution for strengthening in timber construction. In particular, the use of glued-in FRP rods for timber connections instead of steel is of great interest, due to the improved durability of the joint systems compared to their equivalent counterparts made of steel rods. For pull-out tests, the estimation of the mechanical response of glued FRP rods into glulam timber is very complex because of the combination of the three different materials: FRP rods, epoxy resin and glulam timber as well as the complexity of the expected brittle modes of failure of the timber. On the other hand, the existing prescriptive approaches (standard design codes) did not cover all the modes of failure expected within timber material and their predictivity is highly depending on the loading direction and on the rod material. There is, therefore, still a need to establish a general and predictive FE model to simulate accurately and cost-effectively the glued-in rod timber connections. In this study, a FE model combining 3D continuum damage mechanics (CDM) and cohesive zone modeling approaches is presented and its effectiveness was verified by comparison to experimental results available in the literature.

The Use of Fiber-Reinforced Polymers in Wildlife Crossing Infrastructure

The proven effectiveness of highway crossing infrastructure to mitigate wildlife-vehicle collisions with large animals has made it a preferred method for increasing motorist and animal safety along road networks around the world. The crossing structures also provide safe passage for small- and medium-sized wildlife. Current methods to build these structures use concrete and steel, which often result in high costs due to the long duration of construction and the heavy machinery required to assemble the materials. Recently, engineers and architects are finding new applications of fiber-reinforced polymer (FRP) composites, due to their high strength-to-weight ratio and low life-cycle costs. This material is better suited to withstand environmental elements and the static and dynamic loads required of wildlife infrastructure. Although carbon and glass fibers along with new synthetic resins are most commonly used, current research suggests an increasing incorporation and use of bio-based and recycled materials. Since FRP bridges are corrosion resistant and hold their structural properties over time, owners of the bridge can benefit by reducing costly and time-consuming maintenance over its lifetime. Adapting FRP bridges for use as wildlife crossing structures can contribute to the long-term goals of improving motorist and passenger safety, conserving wildlife and increasing cost efficiency, while at the same time reducing plastics in landfills.

Diagnosis of the microstructural and mechanical properties of over century-old steel railway bridge components

The mechanical and microstructural properties as well as durability of more than century-old steel railway bridges that are still widely in use, among others in Poland, have not been well recognized. Ignoring the effect of material and mechanical properties on the operation of an old-steel bridge may eventually lead to the structure’s failure. This study investigates the reliability of a 100-year-old bridge made of wrought (puddled) iron. The aim of this study is to identify the microstructural and mechanical properties of over century-old steel bridge components in relation to the requirements for modern mild steel grades. The paper presents an analysis of the material and mechanical behaviour of a truss railway bridge that had been in operation for over a century. Laboratory tests were performed on samples taken from the component parts of a dismantled railway bridge, i.e. stringers, crossbars, lower belts, stringer bracings and wind bracing. Fatigue, fracture, hardness and tensile tests are performed to estimate the mechanical properties of the investigated steel bridge component parts. Spectroscopy is used to examine the chemical composition of every element. Light optical microscopy and scanning electron microscopy are employed to examine the microstructure of the steel component parts and its non-uniformities. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) are used to obtain data about the fracture mechanism and the chemical composition of non-metallic inclusions. Microstructural and mechanical results are discussed in relation to modern mild steel grades S355 and S235, which are widely used structural ferrous alloys. Based on the chemical composition analysis, the possibilities of increasing the strength of the bridge by welding methods and the application of fibre-reinforced polymer (FRP) composite materials are discussed. Obtained results add to the body of knowledge about the maintenance, reinforcement and demolition of bridge structures, which is crucial for preventing failure of over 100-year-old steel structures. This research is an introduction to the study on reinforcing old steel structures by FRP composite materials.

Interfacial performance of aramid, basalt and carbon fiber reinforced polymer bonded concrete exposed to high temperature

Externally bonding fiber reinforced polymer (FRP) is an effective approach to strengthen/retrofit concrete structures. However, little is known on bond performance of FRP-bonded concrete under high temperature, impeding the application of FRP in buildings potentially subjected to fire. In this paper, the bond performance of aramid, basalt and carbon FRP-concrete subjected to high temperature (80–300 °C) has been investigated through acoustic-laser technique, macroscale fracture tests and microscale characterization. Results have shown that the deterioration percentages of both peel and shear interface fracture toughness of aramid FRP-bonded concrete are largest under high temperature, followed by carbon FRP-bonded concrete and basalt FRP-bonded concrete. The mechanisms behind different bond performance have been revealed with variations of microscale morphology and chemical decomposition. The results and findings can provide a fair comparison of thermal susceptibility and residual bond performance of various FRP-bonded systems, and contribute to designing FRP strengthening/retrofitting systems under high temperature.