Carbon Fibre Reinforced Research Articles

Enhancement of mechanical properties, durability and service life of low carbon cement paste with super low w/c ratio by incorporating carbon fiber

The high strength and durability of cement-based materials are pivotal for energy conservation and carbon emission reduction. By employing solid water mixing technology, a cement-based material with a significantly high compressive strength was developed. However, the concurrent increase in brittleness prompted the exploration of carbon fiber as a potential bridging agent to improve toughness. This paper investigates the role of carbon fiber reinforcement in enhancing the mechanical properties, durability, and service life of cement paste with a super low water-to-cement (w/c) ratio. The results demonstrated that the addition of 0.3 vol% carbon fiber led to an 18.4 % increase in 28-day flexural strength compared to the control group, as well as a 15.3 % increase in flexural compression ratio. Furthermore, under the same carbon fiber content, the drying shrinkage rate after 150-day exhibited a decrease of 20.3 %, and there was a notable decrease of 35.80 % in compressive strength loss rate after 200 freezing-thawing cycles. Service life was significantly improved. It showed that carbon fiber could improve the toughness and durability of hardened cement paste.

The effect of printing parameters on the mechanical properties of fiber-reinforced PA6 matrix composites in material extrusion-based additive manufacturing

PurposeThis study aims to understand the effect of the use of different proportions and types of fibers in the polyamide 6 (PA6) matrix during material extrusion-based additive manufacturing (MEX) and the effect of the manufacturing parameters on the mechanical properties. The mechanical, thermal and morphological properties of PA composites that are reinforced with carbon fiber (CF), glass fiber (GF) and as well as hybrid fiber (HF) were investigated.Design/methodology/approachIn this study, the effect of nozzle temperature and layer thickness on the mechanical properties of composite samples was investigated in terms of their behavior under tensile, impact and compression loads, manufacturing parameters as well as fiber ratio and type. The results were also consolidated by scanning electron microscopy.FindingsAt 20 Wt.% CF reinforcement PA6 samples, a tensile strength value of 125 MPa was obtained with a 60% increase in tensile strength value compared to neatPA6. The HF-reinforced ones also measured a tensile strength value of 106.69 MPa. This corresponds to an increase of 38% compared to neatPA6. The results also show that HF reinforcement can be an important component for many composites and a suitable material for use under compression loading.Originality/valuePA6, an engineering polymer, can be produced by MEX, which offers several advantages for complex geometries and customized designs. There are studies on different carbon and GF ratios in the PA6 matrix. Using these fibers together in a HF, the examination of their mechanical properties in the MEX method and the examination of the effect of GF reinforcement in the hybrid structure, which has a cost-reducing effect, has been an innovative approach. In this study, the results of the optimization of the parameters affecting the mechanical properties in the production of samples reinforced with different ratios and types of fibers in the PA6 matrix by the MEX method are presented.

Bending Strength of Continuous Fiber-Reinforced (CFR) Polyamide-Based Composite Additively Manufactured through Material Extrusion.

This paper shows the three-point bending strength analysis of a composite material consisting of polyamide doped with chopped carbon fiber and reinforced with continuous carbon fiber produced by means of the material extrusion (MEX) additive manufacturing technique. For a comparison, two types of specimens were produced: unreinforced and continuous fiber-reinforced (CFR) with the use of carbon fiber. The specimens were fabricated in two orientations that assure the highest strength properties. Strength analysis was supplemented by additional digital image correlation (DIC) analysis that allowed for the identification of regions with maximum strain within the specimens. The utilization of an optical microscope enabled a fractographic examination of the fracture surfaces of the specimens. The results of this study demonstrated a beneficial effect of continuous carbon fiber reinforcement on both the stiffness and strength of the material, with an increase in flexural strength from 77.34 MPa for the unreinforced composite to 147.03 MPa for the composite reinforced with continuous carbon fiber.

Study on the Bending-Shear Properties of Concrete-Filled Circular Carbon Fibre Reinforced Plastic Steel Tubes.

In order to study the bending-shear performance of CFRP concrete-filled steel tubes, static tests were conducted on 15 circular concrete-filled CFRP steel tube bending-shear specimens. For all specimens, Ds was 120 mm, ts was 2 mm, and ml was 1. The shear displacement (V-Δ) curve of the specimen and the collaborative work between the steel tube and CFRP are discussed. ABAQUS was applied to simulate the V-Δ curve and failure mode of the specimen. We explored the effects of CFRP layers, material strength, the steel ratio, and the shear span ratio on the bending-shear performance of components. The experimental results show that a steel tube and CFRP can work together. As the shear span ratio increased, the bearing capacity and stiffness of the specimen decreased. An increase in the number of transverse CFRP layers could improve the bearing capacity of the specimen, but it had no significant effect on the stiffness. Calculating the elastic stage stiffness and bearing capacity of 15 short columns of test and FE curves revealed an average error of 6.71% and a mean square error of 0.83 for the elastic stage stiffness. The simulation results of the established finite element model are in good agreement with the experimental results. The average error of the bearing capacity was 3.88%, with a mean square error of 0.94. Based on experimental and finite element results, the moment shear correlation equation for concrete-filled CFRP steel tube bending-shear members is presented.

Advanced analysis of intact, fire-damaged, and CFRP retrofitted bridge pier columns under vehicle collisions: Empirical equivalent static force equation and framework

A series of numerical simulations were completed to investigate the behavior of intact, fire-damaged, and Carbon Fiber-Reinforced Polymers (CFRP) retrofitted reinforced concrete (RC) bridge columns of varying sizes subjected to vehicle collisions. Three-dimensional finite element models of isolated RC columns and their foundation systems surrounded by soil volumes were developed using LS-DYNA. A comprehensive parametric study was carried out to investigate the effects of nine demand and design parameters on the performance of bridge columns. Studied parameters included: column diameter, column height, unconfined compressive strength, steel reinforcement ratio, fire duration, CFRP wrap thickness, wrapping configuration, vehicle’s mass, and vehicle’s speed. For each studied scenario, Peak Twenty-five Milli-second Moving Average (PTMSA) was employed to estimate the Equivalent Static Force (ESF) corresponding to each vehicle collision scenario. Resulting ESFs were then utilized to assess effectiveness of the current ESF approach available in the American Association of State Highway and Transportation Officials Load and Resistance Factor Design (AASHTO-LRFD) Bridge Design Specification for analyzing and helping design bridge columns under vehicle collision. Multivariate nonlinear regression analyses were used to derive an empirically based, simplified equation to predict the ESF that corresponds to a vehicle collision. Rather than constant design force, this equation established a correlation between ESF and kinetic energy, column axial capacity, and column height. Results indicated that the proposed equation is reliable and can accurately predict ESFs over a diverse range of collision scenarios that included intact, fire damaged, and CFRP retrofitted columns. To facilitate realistic implementation of the derived equation, an ESF assessment framework was also devised.

A Comparative Analysis on the Optimization of Carbon Fibre Reinforced Polymer and Glass Fiber Reinforced Polymers as Wrapping Structures on Defected Piping System using Computational Simulation Approach

This study examined the application of carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) as wrapping structures for defective pipe systems. The structural behavior and performance of the CFRP and GFRP wrapping structures were assessed using computational simulation methodologies. The goal of the study was to determine the best wrapping material for strengthening the integrity and reliability of piping systems with defects by comparing the results of the simulations. The study evaluated the capability of the proposed composite wrapping structure through CAD simulation. The simulations provided preliminary analysis and visually depicted deformations, aiding in the selection of an optimized lamination orientation for the composite wrapping structure in real-world applications. Eventually, this approach could have alleviated two primary failure modes that were common in composite repair: composite overloading due to excessive thickness and composite delamination from the substrate. The results of this study would have helped enhance effective and efficient pipe repair techniques in a variety of industries by offering useful insights into the selection and use of suitable wrapping structures for repairing defective pipes.

Real-Time Phased Array Ultrasonic Monitoring of Debonding Growth Under Cycling Loading in CFRP

Carbon Fibre Reinforced Polymer (CFRP) composites are widely employed in diverse industries due to their specific stiffness and strength, and corrosion resistance. However, over time, service-induced damage can initiate a failure that can threaten the operation’s safety and reliability, especially in critical industries like aerospace applications. The challenge lies in identifying and monitoring the defects before they escalate into serious issues. Non-Destructive Testing (NDT) methods play a pivotal role in this scenario, aiming to detect and evaluate defects without causing harm to the material. Detecting flaws in composite materials such as CFRP remains a complex task. Traditional NDT methods often struggle to effectively pinpoint and assess defects within these intricate structures. However, recent advancements in ultrasonic testing, especially Phased Array Ultrasonic Testing (PAUT), show promise in examining the internal composition of CFRP composites with higher accuracy and reliability. This study aims to demonstrate the applicability of PAUT for real-time monitoring of debond growth under dynamic loading. The loading was applied to the test specimens up to one million cycles, and 64 elements 2 MHz linear phased array probe was attached to the specimen. The acquired signals were analyzed and could also be recorded for offline processing or archiving. To validate the credibility of the findings, the performance of PAUT was compared to Acoustic Emission (AE), a well-established method for detecting and analysing high-frequency signals emitted by materials undergoing deformation or damage. Encouragingly, both methods exhibited similar trends in capturing the growth of debond. Furthermore, to verify the final defect lengths, post-test ultrasonic C-Scans utilizing the through transmission technique were conducted, complemented by visual inspections. These assessments served to confirm the accuracy and reliability of the results obtained through Phased Array Ultrasonic Testing. Real-time monitoring of composite structures using phased array technology comprises a valuable tool for real- time assessment of debonding in the composite. As industries continue to rely on Carbon Fibre Reinforced Polymer composites for multifaceted applications, the utilization of advanced Non-Destructive Testing methodologies like Phased Array Ultrasonic Testing emerges as a cornerstone in guaranteeing their continued integrity and performance.

Effect of ICCP on tensile performance and piezoresistive effect of CFRCM plates

Currently, extensive research has been conducted on carbon fabric−reinforced cementitious matrix (CFRCM) composites, impressed current cathodic protection (ICCP), and the piezoresistive effect in the field of strengthening of reinforced concrete (RC) structures, corrosion protection of steel reinforcement, and structural health monitoring, respectively. This study utilized two types of matrix materials: normal matrix (sand conforming to ISO standard) and seawater sea-sand matrix. The mechanism by which the ICCP procedure affects the degradation of tensile performance in CFRCM plates with these two types of matrix materials was investigated in the study. Additionally, the piezoresistive effects of CFRCM with the two types of matrix materials after the ICCP procedure were analyzed, and the impact of ICCP on the piezoresistive effect was also investigated. By observing the piezoresistive effect of each CFRCM segment, the sequence of crack propagation and an approximate crack location can be inferred. Finally, the tensile performance of CFRCM with charge density was investigated. Leveraging the dual functionality of carbon fiber reinforcement and sensing, this study lays the groundwork for the development of a triple-functional system encompassing impressed current cathodic protection, structural strengthening, and structural health monitoring (ICCP-SS-SHM). Seawater sea-sand has the potential to be used as an alternative to freshwater river sand, which is beneficial for addressing the shortage of freshwater river sand resources.

A Water-Soluble Thermoplastic Polyamide Acid Sizing Agents for Enhancing Interfacial Properties of Carbon Fibre Reinforced Polyimide Composites.

Carbon-fiber-reinforced polyimide (PI) resin composites have gained significant attention in the field of continuous-fiber-reinforced polymers, in which the interfacial bonding between carbon fiber and matrix resin has been an important research direction. This study designed and prepared a water-soluble thermoplastic polyamide acid sizing agent to improve the wettability of carbon fiber, enhance the van der Waals forces between carbon fiber and resin and strengthen the chemical bonding between the sizing agent and the alkyne-capped polyimide resin by introducing alkyne-containing functional groups into the sizing agent. This study found that the addition of a sizing layer effectively bridged the large modulus difference between the fiber and resin regions, resulting in the formation of an interfacial layer approximately 85 nm thick. This layer facilitated the transfer of stress from the matrix to the reinforced carbon fiber, leading to a significant improvement in the interfacial properties of the composites. Adjusting the concentration of the sizing agent showed that composites treated with 3% had the best interfacial properties. The interfacial shear strength increased from 82.08 MPa to 108.62 MPa (32.33%) compared to unsized carbon fiber. This research is significant for developing sizing agents suitable for carbon-fiber-reinforced polyimide composites.

Bond performance of FRP bar reinforced concrete under monotonic load and fatigue effect

In order to investigate the bonding properties of FRP-reinforced concrete under different loads, a series of FRP-reinforced concrete specimens were subjected to pull-out tests. Three types of reinforcement were used in the experiment: ordinary steel reinforcement, carbon fiber reinforcement (CFRP), and glass fiber reinforcement (GFRP). Pull-out tests were first conducted under monotonic load to determine the effect of concrete strength and reinforcement diameter on the bond performance of FRP bar-reinforced concrete and steel-reinforced concrete. The investigation of the variation of bond performance under different reinforcement materials was made. Second, a fatigue test was done, followed by further pull-out tests to get the bond stress-slip curve between concrete and reinforcement, and the influence of fatigue action on the bond stress-slip curve was further examined. The formulae to calculate the stress were developed, which can be applied to determine the bond failure pattern, bond strength, and bond-slip curve.

Carbon vs. Titanium Nails in the Treatment of Impending and Pathological Fractures: A Literature Review.

Background: Long bones are commonly affected by musculoskeletal tumors, but they also represent one of the most frequent locations for metastases. The treatment is based on pain management and the prevention or stabilization of pathological fractures by intramedullary nailing. While titanium nails are probably the most used, carbon-fiber-reinforced (CFR) nails have emerged as a new option for oncological patients. The aim of this review is to compare titanium and CFR nails according to current findings. Methods: Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) standards were followed: a total of 1004 articles were identified and 10 were included. Results: Traditionally, titanium implants are highly valued for their optimal biomechanical properties and ease of insertion, facilitated by their radiopacity. However, the use of titanium poses challenges in radiotherapy due to interference with radiation dosage and the creation of ferromagnetic artifacts. Conversely, CFR implants have emerged as a recommended option for intramedullary fixation, due to their biomechanical and structural properties and their benefits during radiotherapy and follow-up monitoring X-ray. Conclusions: CFR nailing represents a promising advancement in the surgical management of oncological patients with long bone metastases. However, further studies are needed to increase surgeons' confidence in their use.

Sustainability and Circular Economy in Carbon Fiber-Reinforced Plastics

Sustainability and Circular Economy in Carbon Fiber-Reinforced Plastics

Finite element analysis of fibre reinforced timber beams under flexural loading

ABSTRACT Laminated Veneer Lumber (LVL) is a popular product used in the building and construction industry because of its high strength, serviceability, aesthetic characteristics, and cost-effectiveness. However, LVL has traditionally been limited to residential and small light commercial buildings. To expand the use of LVL and reduce the need for steel and reinforced concrete structural members, a comprehensive computational study is conducted to understand the material’s structural performance and find an optimal strengthening ratio. In this paper, a new 3-dimensional Finite Element model was introduced and evaluated to predict the structural behaviour, strength properties, and failure damage modes of LVL timber beams reinforced with a Carbon Fibre Reinforcement Polymer (CFRP) sheet. The model is validated with three experimental tests from the literature, with the reinforced timber model showing a 1.8% error compared to the plain timber model’s 7% error. Additionally, a parametric study is conducted to understand the effects of reinforcement length on the structural behaviour of the reinforced beam, with mathematical equations established to express the relationships. The study found that reinforcing 50% of the beam span generally resulted in the most significant strength improvement. This investigation is made for various strength and serviceability parameters.

Enhancing self-healing performance of microbial mortar through carbon fiber reinforcement: An experimental analysis

The incorporation of fibers has been shown to be an effective means to enhance self-healing properties of biomass self-healers in cementitious materials. In this study, the mechanism of carbon fiber-enhanced self-healing ability for self-healing agent made by straw charcoal adsorbed bacteria in mortars was investigated. Mechanical properties, compressive strength restoration properties and permeability testing of microbial mortars were evaluated. Our findings reveal a synergistic effect between carbon fibers and the self-healing agent, notably in crack repair. Although fibers alone did not significantly increase compressive strength, can play a crucial role in promoting Ca2+ aggregation and facilitating the transformation of spores into bacteria, which resulted in the formation of structurally intact and layered calcium carbonate, result in significantly enhanced the self-healing efficacy of microbial mortars. The results of this study show for the first time that carbon fibers have a significant effect on the self-healing capacity of biomass mortar.

Study on the Permeability and Mechanical Properties of Sandy Soil Under Carbon Fiber-Based Urease Mineralization

In recent years, soil solidification by EICP method is a green and environmentally friendly foundation treatment technology that has become popular in the field of geotechnical engineering. Compared with the traditional chemical induction method and the MICP method, the EICP method is not easily restricted by environmental factors associated with engineering geological problems and is green and environmentally friendly with lower cost. In this paper, a study was carried out to improve the seepage-mechanical properties of sandy soils by the EICP method. First, soybean urease solution extraction and its performance optimization methods were explored. Tests were conducted to compare urease extraction and detect activity. The activity of urease was 7.1% higher in deionized water than Laoshan mineral water. Second, the EICP grouting mineralization test was performed by using the carbon fiber reinforcement method. The CaCO3 content, unconfined compressive strength, porosity, permeability and other indicators of the sandy soil were systematically analyzed, and microscopic tests were conducted. The test results showed that after carbon fibers were added to the sand, the mineralization effect of EICP led to the precipitation of CaCO3 that adhered to the surfaces of sand grains and fibers and filled and cemented the pores between sand grains, which improved the integrity of the spatial structure and formed a stable solid sand-fiber monolithic composite structure. When the carbon fiber content was 1.2%, all aspects of performance were optimum. The above test results showed that the carbon fiber-based EICP mineralization method could effectively inhibit the brittle failure and improve the permeability and mechanical properties of sandy soil. This method has good application prospects and development potential for use in engineering geology.

Cross-sectional shape effect of stay-in-place formwork column on axial compressive behaviour

Experimental and numerical studies on the behavior of composite columns with prefabricated self-compacting mortar (SCM) stay-in-place (SIP) formwork and post-cast normal-strength core concrete were presented.The axial compression of twenty-eight reinforcement concrete (RC) composite columns having square or circular cross-section shapes, with formwork thicknesses of 10 mm or 15 mm, and confined with one or two layers of Carbon Fibre Reinforced Polymer (CFRP (, were tested. A finite element (FE) model was generated to simulate the stress–strain relationship, and failure mode of the column using ABAQUS software. The results show that square cross-section-shaped columns exhibited lower axial load and displacement capacities than their counterparts of equivalent circular cross-section-shaped columns. This behavior maintained consistent regardless of the use of the SCM-SIP formworks or the wrapping with CFRP fabrics. Among the various confinement systems compared in this study, the efficiency of the CFRP was the greatest. Good bonding with no peeling failure was observed between SCM-SIP formwork and core concrete, indicating the good integrity of the composite columns. Consistency between the FE model and experimental results was observed for both cross-section shapes, indicating the precise and plausible characteristics of the model to sensibly estimate the stress-strain behaviors.

An experimental investigation of tensile residual strength of repaired composite laminates after low velocity impact

Low Velocity Impact (LVI) of Carbon Fibre Reinforced Polymer (CFRP) components are common during the manufacture and in-service life of aerostructures. However, the resulting effect on structural mechanical properties has not been extensively studied when the damage occurs on repaired components, which are already compromised to some degree. This research considers the relative mechanical performance of CFRP parts that are (1) pristine, (2) repaired using the stepped scarf method, and (3) repaired then impact damaged (low velocity impact at 5 J energy). For each case, subsurface damage was visually investigated and detailed measurements taken including impact load–time/energy–time behaviour, and post-impact tensile maximum force, stress and strain (and homogenised Young's modulus) before fracture. Further, three different repair patch sizes were considered. The experiments show that negligible surface impact damage was present in all repair cases but that delamination and debonding occurred for all but large repairs. For small and medium repair patches, 71% and 83% of the static strength of pristine samples were observed, with nearly full recovery for large repairs. After LVI, the strength of small repairs did not decrease whereas that of medium repairs declined to 77%. Interestingly, LVI did not have any impact on load bearing capability of large repairs. Stiffness measurements increased with repair size, even exceeding the value for pristine samples in some cases. The maximum stresses sustained were 67%, 77% and 85% that of a pristine sample for small, medium, and large repairs respectively.

Experimental Study on Repairing/Restoration and Reinforcement Methods of the Reinforced Concrete Structures Damaged by Earthquakes

For earthquake-damaged reinforced concrete structures, the static loading test method is adopted to carry out loading tests under cyclic loading on reinforced concrete beams with different reinforcement rates and columns with different axial compression ratios, and the effect of reinforcing and repairing the damaged reinforced concrete structure by using adhesive steel plates and carbon fiber cloth is investigated. Through comparative studies of structural hysteresis curves and skeleton curves under different reinforcement methods, it is concluded that reinforcement has significantly improved the hysteresis characteristics and ductility of members, and the seismic performance of the carbon fiber reinforcement method is better than that of the steel plate reinforcement. This study provides valuable references and suggestions for practical earthquake-damaged building reinforcement and repair works and seismic reinforcement works.

Mechanical properties of lightweight 3D-printed structures made with carbon-filled nylon

Material extrusion additive manufacturing is a widely used 3D-printing process involving depositing molten thermoplastic materials layer by layer to create a 3D object. Combining material extrusion with composites creates strong, lightweight, and functional parts with unique properties. This study uses chopped carbon fiber reinforcement to investigate polyamide's thermal, rheological, and mechanical properties. The study includes an analysis of the material's thermal properties via differential scanning calorimetry and its flow behavior via rotational rheometry. This study provides a comprehensive understanding of carbon-filled nylon PA material's economic and mechanical properties, which will help optimize its performance for various applications. Tensile and flexural tests were used to appraise the material's strength and stiffness under different loading conditions. A cost analysis was performed to compute the specimen cost as a function of orientation and infill density. The aim was to understand how the type and strategy of infill design impact the material's mechanical properties, helping optimize the performance of components and evaluating its cost.

Effect of anodic oxide layer on friction stir spot welding between anodized A5052 and CFRTP

Dissimilar joining between carbon fiber reinforced thermoplastic (CFRTP) and metal has attracted attention of transportation equipment industry for reduction of weight and cost by multi-material structure. Friction stir spot welding (FSSW) between anodized A5052 (AO-A5052) and carbon fiber reinforced thermoplastic (CFRTP) was investigated for the improvement of joining strength. Average tensile shear strength of AO-A5052/CFRTP joint was 2505 N and more than 500 N higher than that of untreated-A5052/CFRTP joint. In the AO-A5052/CFRTP joint, probe plunge induced cracks and microwrinkles in the anodic oxide layer on the weld surface. Matrix resin was immersed into the cracks and the microwrinkles underneath of the shoulder of the welding tool. Reinforced carbon fiber and matrix resin was immersed into large crack at the outer peripheral corner of probe. Thus, those increased the joining strength by mechanical anchoring effect. Thermal stress test and machining stress test were performed for revealing the mechanism of cracking of anodic oxide layer. Although thermal stress did not generate cracks in the anodic oxide layer, machining stress by probe plunge generated cracks in the anodic oxide layer. The generated cracks in anodic oxide layer underneath of the shoulder were distorted to the rotating direction of welding tool by the friction stirring.