Use Of Carbon Fiber Reinforced Polymer Research Articles

Bond-Damaged Prestressed AASHTO Type III Girder-Deck System with Retrofits: Parametric Study

This research describes an in-depth analysis of the flexural strength of a strengthened AASHTO Type III girder-deck system with debonding-damaged strands based on the finite element software ABAQUS 6.17. To investigate the stand-debonding impact and retrofit, two strengthening techniques by the separate use of carbon fiber-reinforced polymer (CFRP) and steel plate (SP) were proposed. A detailed finite element analysis (FEA) model considering strand debonding, material deterioration, and retrofitting systems was developed and verified against relevant experimental data obtained by other researchers. The proposed FEA model and the experimental data were in good agreement. The sensitivity of the numerical model to the mesh size, element type, dilation angle and coefficient of friction was also investigated. Based on the verified FEA model, 156 girder-deck systems were studied, considering the following variables: (1) debonding level, (2) span-to-depth ratio (L/d), (3) strengthening type, and (4) strengthening material amount. The results indicated that the debonding level and span-to-depth ratio had a major effect on both load–deflection behaviors and the ultimate strength. The relationships between the enhancement of the ultimate strength and the thickness of the strengthening material were obtained through regression equations with respect to the CFRP- and SP-strengthened specimens. The coefficient of determination (R2) was 0.9928 for the CFRP group and 0.9968 for the SP group.

Micromechanical Modelling of the Deformation Mechanisms of Friction-Spun Yarn from Recycled Carbon Fibres

The growing use of carbon fibre-reinforced polymers (CFRP) results in an increased amount of CF waste from offcuts or end-of-life components. A promising method to reuse the waste fibre materials in a structural component with excellent mechanical properties is the processing of recycled CF (rCF) and thermoplastic fibres into hybrid yarns. Spinning of friction spun yarns consisting of more than 90% rCF and containing almost no thermoplastic fibres that are suitable for thermoset composites, currently leads to high fibre damage and low yarn quality and is, therefore, addressed in this project. The technology is reported in another paper. One of the limiting factors for drapability of textiles is the stretchability of continuous fibres and draping of the semi-finished textile products for complex geometries is still error-prone. Friction spun yarns exhibit significantly higher yarn elongations due to sliding mechanisms between the fibres. The deformation properties of friction spun yarns are significantly influenced by fibre-fibre interactions and depend on a variety of process and material parameters. In the following, micromechanical finite element models of the spun yarns are created by using beam elements. Monte Carlo method is used to model local variabilities in the yarns. The models are then used to simulate yarn behaviour under deformation and to investigate the influence of various process parameters.

Carbon Fiber Reinforced Polymer Adoption for Structural Rehabilitation

ABSTRACT Flexural strengthening is essential when structures face increased loads or usage changes, requiring localized reinforcement. Carbon Fiber Reinforced Polymers (CFRP) are widely used for repairing deteriorating concrete elements, notably boosting their flexural and shear strength and prolonging their lifespan. However, CFRP applications may encounter challenges like delamination. Therefore, it is important to select a good product and adhesive to enhance the performance of the fiber. The purpose of this study is to propose proper composite strengthening for a reinforced concrete structure to increase its flexural and shear capacity. A case study of a small office building in Italy is selected and one sectional frame consisting of six beams is studied. The first step in this process is to assess the moment and shear forces due to the initial loads based on the existing longitudinal and shear reinforcement. Then, the moment and shear forces due to the upgraded loads are calculated using SAP 2000 to determine if flexural strengthening is needed for any of the six beams being analyzed to avoid ductile failure of the steel rebars and brittle failure of the concrete. The use of CFRP showed positive results in terms of structural rehabilitation for the building, particularly when subjected to elevated loads. This not only contributes to the building’s overall safety but also extends its service life, making it a valuable and sustainable solution for structural enhancement in the face of varying load conditions.

Improved Bond Stress-Slip Relationships for Carbon Fibre-Reinforced Polymer-Strengthened Masonry Triplets

Carbon fibre-reinforced polymer (CFRP) emerges as a viable solution for reinforcing unreinforced masonry (URM) walls subjected to shear loads. While masonry structures are straightforward to construct, the complexity of the construction materials, especially in terms of their mechanical properties, poses challenges for numerical studies of their structural behaviour. Walls, being fundamental components in masonry construction, play a crucial role in transferring both horizontal and vertical lateral forces. This study investigates the enhancement of masonry wall behaviour through the reinforcement of CFRP. CFRP reinforcement increases ductility and strength, reducing the risk of failure under shear conditions. Additionally, CFRP composites present a practical solution to strengthening masonry structures compared to traditional reinforcement. However, brick, mortar, and CFRP have not been thoroughly investigated. Experimental tests on the bond behaviour of different configurations of CFRP-retrofitted masonry triplets have not been performed before and are therefore presented in this paper. Triplet specimens, comprising three bricks and two mortar joints, both with and without CFRP strengthening, were subjected to bond testing. The study affirms that masonry triplets strengthened with CFRP under shear loads exhibit strength levels at least four to six times greater than those without CFRP. The experimental work was carried out with eight different CFRP configurations on triplet masonry, and each test was repeated four times. Further, the bond stress-slip relationship in the case of masonry triplets with and without CFRP was predicted with new mathematical equations based on the conducted test results. These equations were included in the commercial finite element software ANSYS and used to conduct simulations of CFRP-reinforced masonry triplets. The numerical results indicate good agreement between the finite element model and the test results. The outcome of this research improves the current knowledge on the use of CFRP to reinforce masonry walls with brick and mortar, which will contribute to the understanding of the effect of CFRP on masonry structures.

Finite element analysis and retrofit of the existing reinforced concrete columns in Iraqi schools by using CFRP as confining technique

Abstract There are many studies about the use of carbon fiber-reinforced polymer (CFRP) to strengthen concrete members such as columns, beams, and slabs. The effectiveness of these strengthening techniques has been proved by enhancing the mechanical properties of concrete structures. So, CFRP has been used to strengthen and repair existing concrete structures in Iraq. For example, in Al-Mosul city, the strengthening and repairing system is done for concrete members such as beams, columns, and slabs using the Near Surface Mounted or confinement technique. Therefore, the research aim is to use CFRP for maintenance as an alternative material to strengthen and repair concrete members in Iraqi schools. This article employs methods to enhance and repairing of some of concrete columns at Al-Abeer school in Najaf city by using modern materials as an alternative method of maintenance. In addition, finite element analysis was carried out using Abaqus software to verify the effectiveness of strengthening. The reinforced concrete (RC) column strengthened by using fiber-reinforced polymer as a confining technique increased compressive strength by about 91% compared to the control column. In addition, the value of strains increased to nearly 100% in the longitudinal direction with the stability of the value of the lateral strains, despite the occurrence of a significant increase in the compressive strength capacity. So, the values of vertical displacement at stress 4 MPa were 22.3 mm for the strengthened RC column and 5 mm for the control RC column. Thus, the strengthened RC column increases the values of compressive strength with a decrease in displacement to approximately 22%. Four years ago, the strength of the school building was assessed, thus the success of the strengthening.

Performance of reinforced concrete elements strengthened with carbon fiber CFRP at elevated temperatures

The importance of the research topic is established by the problems that occur in structural buildings when exposed to fire accidents, where the concrete loses much part of its mechanical properties and therefore becomes out of service. Because reconstruction of damaged buildings has a high financial cost, it is necessary to focus on the restoration of damaged concrete members with performant techniques and proven efficiency in terms of increasing the strength of concrete and its resistance to high temperatures. The authors conduct a numerical investigation on the use of carbon fiber-reinforced polymer sheeting CFRP to restore various structural concrete elements such as beams, columns, and slabs damaged in fire accidents for two types of normal and high-strength concrete, in addition to studying the behavior of concrete after strengthening it with CFRP sheets. The results by showed that load capacity, stiffness index, and absorption energy index have been improved

White LED induced photooxidation aging of epoxy / carbon fibre reinforced polymer and its implications for cleanroom cleanliness and contamination control

The alteration of an epoxy-based Carbon Fiber Reinforced Polymer (CFRP) by visible light is investigated by accelerating the aging process. Several parameters are studied such as the dose, the wavelength effect, or the atmospheric composition. The degradation is found to be led by a photooxidation process using light of wavelength up to typically 500 nm irradiation and affects the first microns of the irradiated surface. Besides, when the aged CFRP is gently rubbed, micrometric epoxy particles can be generated. Such particle formation might have important impact on some industries due to the wide use of CFRPs. The study is extended to other types of resins and includes results on non-accelerated aging. Recommendations are given to limit and control the risk of aging.

Hybrid strengthening and flexural behaviour of post-tensioned laminated glass beams

The strengthening of glass for structural applications is challenging. EBR (External Bonded Reinforcement) reinforcement is often preferred, although limitations result from stress concentrations especially in the case of post-tensioning. This study explores the use of CFRP (Carbon Fiber Reinforced Polymers) and/or Fe-SMA (Iron-based Shape Memory Alloys) as reinforcement in hybrid and alternative configurations. Five full size laminated glass beams were tested in flexure, combining NSM (Near-Surface Mounted) and EBR techniques and exploring the efficiency of different alternative strengthening layouts (i.e. reinforcement material versus application technique) to overcome the current shortfalls of glass strengthening for structural applications. Even for lower reinforcement ratios, hybrid strengthening systems performed better and increased load-carrying capacity while delaying crack-induced deboning failure, when compared to conventional EBR systems. Residual strength ratio increased from 87 % to 160.8 % and ductility from 407 % to 971 %. The hybrid system combining NSM-CFRP and EBR-SMA reinforcements showed the best performance, increasing the initial fracture stress of glass and maintaining sufficient residual strength capacity, while allowing the safe post-tensioning.

The Effect of Diffrenet Types of Strengthening RC Columns Subjected to Eccentric Load

In many constructions, columns are subjected to eccentric loads. So, they are unable to withstand higher loading requirements. Ferrocement jacketing and fiber-reinforced polymer (FRP) have demonstrated exceptionally high efficacy in comparison to other strengthening techniques. This paper presents the results of experimental studies on reinforced concrete columns strengthened with carbon fiber reinforced polymer (CFRP) and ferrocement layer composites under an eccentric load. The new techniques depended on the combination of (CFRP) and Ferrocement to strengthen RC columns, which are subjected to eccentric loads. To get the average result for the model, ten tested models are patterned using two of each specimen, totaling twenty tested specimens. Models are divided into four groups in accordance with the method of strengthening. The specimen in the first group has not been strengthened. The second group consists of six specimens strengthened with one, two, or three successive layers of the wire mesh with an outer 15 mm thickened coating. The third group consists of four specimens strengthened with one or two successively wrapped layers of the (CFRP). The fifth group consists of six specimens strengthened with one or two layers of CFRP and one or two layers of concrete wire mesh. The purpose of the current study is to compare the use of CFRP, ferrocement layers, or a combination of carbon fibers and ferrocement to strengthen concrete columns that are subjected to eccentric loads (e/t = 0.5). The study has also shown that mixing GFRP with ferrocement is more effective than using ferrocement or carbon, but more expensive.

MILLING PARAMETERS’ INFLUENCE ON MACHINABILITY IN MILLING OF CFRP COMPOSITES FUNCTIONALIZED WITH G AND GO

The use of carbon fiber-reinforced polymer (CFRP) composites having low weight and high strength provides the substantial energy savings in space and aerospace industry. The disadvantage of these composites is that the carbon fiber is not firmly bonded to the epoxy resin and the toughness of the produced materials is low. Graphene (G) and Graphene Oxide (GO) nanoparticles are used to functionalize CFRP composites. The CFRP composites functionalized with G and GO improve the strength of these composites by improving the fiber/matrix interface bond. In this study, the effect of type of nanoparticles, feed rate, cutting speed and number of flutes on machinability (cutting force, delamination factor and surface roughness) were experimentally investigated in the milling of CFRP composites, G-CFRP (CFRP functionalized with G) and GO-CFRP (CFRP functionalized with GO) nanocomposites. Cutting force, delamination factor, and surface roughness were found to be strongly impacted by feed rate, cutting speed, number of flutes, and type of nanoparticles. The increase in the number of flutes contributed to decrease of cutting force, delamination factor and surface roughness, while the increase in the feed rate caused to increase of them. By increasing cutting speed, surface roughness reduced, delamination factor and cutting force increased. In addition, compared to the CFRP composite, the cutting forces and surface roughness were higher, and delamination factor was lower in the CFRP composites functionalized with G and GO.

Shear Behavior of Reinforced Concrete Beams with Different Arrangements of Externally Bonded Carbon Fiber-Reinforced Polymer

Carbonfiber-reinforced polymer (CFRP) composites are frequently utilized in the repair and reinforcement of reinforced concrete members because they are more corrosion-resistant, durable, and flexible than commonly used materials like steel plates. Many studies have demonstrated that the use of CFRP as an internal strengthening material has a substantial impact on the shear capacity of RC beams. This research looks into the possibility of using FRP material as an externally bonded reinforcement to increase the shear strength of RC beams. Because shear improvement and mode of failure are based on the right configuration of the CFRP sheets, the experimental work consisted of eight RC beams with various types, orientations, and configurations of CFRP sheets. All beams were examined under two-point bending. The test results show that the CFRP sheet significantly improved the beam’s shear strength and ductility and that it is advantageous to orient the FRP at 45 degrees to the beam’s longitudinal axis.

Behavior and Load Capacity of Concrete Slab Reinforced by CFRP Bar and Strengthening by CFRP Laminates

Abstract The most common FRP materials used are carbon fiber reinforced polymers (CFRPs), and glass fiber reinforced polymers (GFRPs). The use of CFRPs has grown rapidly in the construction industry, specifically in structural retrofitting, due to their strengthening property of CFRP. CFRPs are moreover high strength, lightweight, noncorrosive, and easy-to-install materials. In the present study, six reinforced concrete slab specimens included two control specimens reinforced by traditional steel reinforcements and the other reinforced by carbon fiber reinforced polymer CFRP bars without strengthening by laminated CFRP strips. The remaining four specimens are interiorly reinforced by CFRP bars and strengthened by CFRP laminates strips with different scheme layouts named Type 1 and Type 2. The specimens were tested under a uniformly distributed load applied at the top surface area of each specimen up to failure. The parameters considered in the present study are the amount of CFRP bars and CFRP laminates layout. Test results indicated that the strength carrying capacity and failure mode of tested specimens differ based on the steel reinforcement type and the presence of CFRP laminates layout.

Structural strengthening of a constructed timber bridge: Field application and numerical modeling

This paper presents the behavior of a timber bridge strengthened with lag bolts, carbon fiber reinforced polymer (CFRP) sheets, and hollow structural sections (HSS). The 83-old bridge is composed of three spans, supported by 14 Douglas Fir girders, and is tested employing truck loadings of 120 kN and 267 kN. Three-dimensional finite element models are formulated to study the flexural response of the bridge with and without the retrofit options. The magnitude of the truck load dominates the degree of dispersion in girder deflections and alters the shape of probability density functions, which are associated with behavioral uncertainty. The effectiveness of strengthening is apparent in terms of reducing the exceedance probability of deflection limits and increasing reliability indices above the design threshold of β = 3.5, stipulated in bridge specifications. Among the three methods, the stiffening efficiency of the HSS option is higher at the system level; however, the use of CFRP is most efficient at the member level. Live load distribution factors are examined and implementable recommendations are provided for practice. Parametric investigations clarify the efficacy of variable HSS sizes and the ramifications of a permit truck weighing 445 kN.

Residual compressive strength of seawater sea sand concrete filled hybrid carbon-glass fibre reinforced polymer tubes under seawater: Effects of fibre type and orientation

Despite the superior mechanical and durability properties, the higher cost of carbon, compared to other fibre options, remains a major concern in the widespread use of carbon fibre-reinforced polymer (CFRP) composites in construction applications. The hybrid formation of carbon fibres with other fibres could help reduce the cost while remaining appropriate structural properties. The present study examines the durability performance of Seawater Sea Sand Concrete (SWSSC) filled hybrid carbon-glass fibre-reinforced polymer (HFRP) tubes after exposure to seawater. Ninety-six samples filled with an alkaline solution simulating SWSSC were exposed to seawater for different durations and at different temperatures. The compressive mechanical properties of the conditioned samples were compared to the unconditioned reference samples to determine the level of mechanical degradation of the tubes. Based on Arrhenius's theory, long-term performance was predicted using the collected experimental data from short-term performance. Fibre type (i.e. carbon, glass, and hybrid carbon-glass) and fibre orientation (cross-ply and hoop) were considered as the material-based variables. When exposed to the most severe condition of 5 months at 60 °C, CFRP showed the highest average strength retention of 86.01%. The hybrid cross-ply tubes exhibited better strength retention than GFRP with strength retention of 64.84% for HFRP compared to 57.23% for GFRP. However, over the long term, the difference in performance between the two types of FRP tubes decreased and became more comparable. The onset of damage in GFRP tubes started sooner than that in HFRP. However, the long-term ultimate strength reduction of HFRP tubes was found similar to the weaker fibre type (i.e. GFRP tubes).

Comparative strength and stability analysis of conventional and lighter composite flexible risers in ultra-deep water subsea environment

The hybrid flexible risers have a multi-layered structure and use thermoplastic composite for the pressure and tensile armour. In contrast, a conventional flexible riser uses heavier carbon steel as armour which significantly contributes to its weight. For shallow-water applications, the conventional risers are widely used in offshore oil and gas industry due to their corrosion resistance properties and low transportation costs. However, the weight of conventional risers is a key limitation in ultra-deep-water applications. This shortcoming can be addressed by including a lightweight carbon fibre reinforced polymer (CFRP) composite as one of the individual layers. The use of CFRP reduces the effective tension at the hang off point which is a key limitation in extending the range of flexible risers. Here, the dynamic stability and functional load interactions of both risers (viz: a thermoplastic CFRP riser and a conventional flexible riser) at a water depth of 3000 m were studied. A global analysis was performed considering the onerous 1000-year hurricane wave with 100-year currents. The investigation considered ±150 m vessel offsets, three vessel headings (viz: 135, 180, 225°) and three vessel draughts (ballasted, empty, loaded). Additionally, a numerical model with a variable bending stiffness was used to capture the orthotropic material behaviour of a flexible riser. Results showed that the buoyancy requirement and effective tension were 2.1 times greater and 2% higher for the conventional riser compared to its composite counterpart. The most onerous case for a conventional riser was at zero offset whereas for its composite counterpart was at –150 m along the length of a riser. It was observed that the heavier masses of a conventional riser aid in aligning the weight vector with the upward direction of the buoyancy force. Contrarily, the composite risers undergo large displacements leading to misalignments and instability. Furthermore, the observed bending radius of the flexible riser was found to be within the allowable minimum bend radius at the hog bend location.

Static and Vibration Analyses of a Composite CFRP Robot Manipulator

This paper reports analyses of a 5-degrees-of-freedom (5-DOF) carbon fiber-reinforced polymer (CFRP) robot manipulator, which has been developed for farm applications. The manipulator was made of aluminum alloy (AA) and steel materials. However, to check the effectiveness of CFRP materials on the static and free-vibration performance of the manipulator, the AA parts were replaced with CFRP. For this purpose, the effects of various cross-sections and layups on three design criteria—deflection, load-carrying capacity, and natural frequency—were investigated. Two types of thin-walled laminated sections, specifically the I section and rectangular tubular sections, were used for the composite parts. These parts were made from three hollow square section (“SSS” section) beams and three I section (“III” section) beams. These multi-cell beams were modeled using the finite element (FE) method. Three configurations were selected for analysis based on the manipulator’s most common operating conditions. The results indicated that the use of CFRP increased the manipulator’s natural frequencies, increased the load-carrying capacity, and decreased the manipulator’s tip deflection when compared with its AA counterpart. An analysis showed that using CFRP in the manipulator’s structure could improve static and vibrational performances. It was observed that the “SSS” section beams were 1.17 times stiffer, could carry a 1.20 times higher load, and were 1.40 times heavier than the “III” section beams. Also, decreasing the fiber direction in angle-ply layups from 90° to 0° and adding 0° plies, while keeping the total number of layers constant, decreased the manipulator’s tip deflection and increased its natural frequencies.

Evaluation of prestress relaxation loss and harping characteristics of prestressing CFRP systems

This paper presents partial results of an investigation about the use of prestressing carbon fiber reinforced polymer (CFRP) systems in prestressed bridge girders. First, stress relaxation tests were conducted on prestressing CFRP cables and bars and continued over a period of one year from the initial prestressing process. Stress relaxation loss found to be linearly related to logarithm of the time and invariant of the length of the specimen. The effect of CFRP anchor loss was also evaluated and used to develop equations for predicting prestress relaxation in both pre- and post-tensioning applications. Then, harping applications of CFRP systems under various harping angles and deviator sizes were experimentally investigated. Higher harping capacity for CFRP cable compared to bar was observed. Premature failure of the CFRP due to localized shear/contact stresses at deviaor location redulted in a significat harping capacity reduction. To maximize the contact surface and reduce the localized shear stress, new deviators were developed, which improved the results. Finally, a finite element (FE) model was developed and calibrated to better understand the harping behavior of CFRP. By performing parametric study on different harping profiles, jacking stress limitations were obtained for the use of CFRP in practical range of harping angles.

CFST columns strengthened with CFRP textile grid-reinforced engineered cementitious composites under eccentric compression

This study proposes a novel technique involving the use of carbon fibre-reinforced polymer (CFRP) textile grid-reinforced engineered cementitious composites for strengthening concrete-filled steel tube (CFST) columns. In this study, the behaviour of composite columns subjected to eccentric loading was investigated. The experimental results proved that the strengthening technique was effective, particularly as the load-bearing capacities of the strengthened columns increased by 11.6%–38.2% when compared with those of the un-strengthened columns. Moreover, the enhancing effect increased with an increase in the number of the CFRP textile layers. Compared with the specimens subjected to axial loading, the eccentric-loaded specimens exhibited a lower load-bearing capacity and stiffness. Besides, the decrease in the diameter–thickness ratio and increase in concrete strength significantly enhanced the load-bearing capacity of the strengthened columns. However, a higher concrete strength increased the brittleness. A model was proposed to predict the load-bearing capacity and N–M curves. The calculation results conform with the test results.

Effect of partial replacement of E-waste as a fine aggregate on compressive behavior of concrete specimens having different geometry with and without CFRP confinement

Nowadays, the improper disposal of electronic waste (E-waste) is leading to environmental pollution and health problems majorly in developing countries. The current research examines the behavior of shredded E-waste fine aggregate concrete strengthened by the use of carbon fiber-reinforced polymer (CFRP) confinement under axial compressive load. The main objective of this study is to investigate the structural behavior of circular and non-circular concrete specimens by partial replacement of E-waste as fine aggregates and confined with CFRP sheets. Tests were performed on a total of 36 concrete specimens. The parameters considered were cross-sectional geometry of circular, rectangular and square concrete specimens, 20% partial replacement of fine aggregates by E-waste, the effect of the corner in case of non-circular specimens, and the number of CFRP sheets. These tests portrayed that the partial replacement of fine aggregates by E-waste aggregates results in decreasing axial compressive strength of concrete specimens. However, the external CFRP confinement increases the axial strength of specimens (a maximum of 71% for circular specimens, 33% for square specimens, and 25% for rectangular specimens). It was also observed that partial replacement of natural fine aggregates by E-waste increased the failure time. For the case of square and rectangular concrete specimens, the ultimate strength was lower than circular specimens for both (with and without CFRP confinement) specimens. Finally, existing strength and strain models developed for FRP-confined concrete were used for theoretical calculations. The theoretical declaration of the existing models indicates that a few of the ultimate strain models lie on the high side and few of the ultimate strain models on the low side in comparison with the experimental findings.

Stress Concentration in Open Hole Laminate Composites Under Bending: Potential Application in Dental Implant Prosthesis

Carbon fiber reinforced polymer (CFRP) have been gaining prominence in replacing metallic alloys for infrastructure in prostheses, with the possibility of edentulous patients to acquire fixed prostheses. For this, procedures are required to connect these implants to the implant-supported fixed prosthesis, such as holes and notches that can reduce their mechanical properties. In addition, the infrastructure requires longer cantilevers, causing greater stress on the prosthetic system. Then, the objective is to analyze the stress concentration in the CFRP subjected to bending loads with holes (4 and 6 mm diameter to verify the influence of the diameter-to-width ratio) in four-point-bending test. Two composite laminates were evaluated: one with thermoplastic matrix of poly(phenylene sulphide) PPS; and another with epoxy matrix combined with carbon fibers fabric. The presence of holes in the studied dimensions did not present significant differences in the flexural modulus and maximum bending strength. Therefore, the use of CFRP showed some advantage regarding the reduced effect of stress concentration compared to metallic alloys.