Fiber Reinforcement Research Articles

Effect of multi-scale hybrid fiber reinforcement on mechanical properties of ultra-high performance concrete

An experimental investigation was conducted on the effect of multi-scale hybrid fiber reinforcement incorporating steel fiber and wollastonite fiber on mechanical properties (i.e. compressive strength, splitting tensile strength, flexural toughness and direct tensile properties) of ultra-high performance concrete (UHPC). The results indicate that, compared with macro-fiber, hybrid steel fiber composed of macro-fiber and meso-fiber improves the strength and toughness of UHPC significantly. The higher the dosage of meso-fiber, the better the effect of hybrid steel fiber. Meanwhile, longer meso-fiber provides a better performance in terms of interfacial bonding strength between the fiber and the matrix of UHPC, leading to an increase in the anti-cracking effect of hybrid steel fiber, and hence the improvement in the splitting tensile strength and flexural toughness of UHPC. Moreover, adding wollastonite fiber as micro-fiber is efficient to enhance the mechanical properties of UHPC incorporating with hybrid steel fiber. It may be related to the respective anti-cracking effect of three types of fiber and their synergistic snubbing effect, as well as the filling effect of wollastonite fiber and the chemical bonding effect caused by the reaction between wollastonite fiber and Ca(OH)2 in the paste.

Thermal Properties of Polypropylene Fibrillated Fibre Reinforced Lightweight Foamed Concrete

Thermal Properties of Polypropylene Fibrillated Fibre Reinforced Lightweight Foamed Concrete

Physical properties of recycled concrete powder and waste tyre fiber reinforced concrete

The environmental concerns of cement manufacturing prompted researchers to study other cementitious materials that are easily available, low cost, and also contribute to improved sustainability. This research was carried out for the utilization of RCP as cement replacement with different replacement ratios including 5%, 10%, and 15%. Furthermore, to improve the tensile behaviors, steel fiber was added (2.0%) as fiber reinforcement. This Part discussed the general back of demolishing construction waste, waste rubber tires, and the physical and chemical properties of RCP. Fresh properties were assessed through setting times, fresh density, and slump cone tests, and physical properties were evaluated through hardened density, water absorption, permeability, and ultrasonic pulse velocity. The change in internal structure and pozzolanic reactivity were evaluated through scanning electronic microscopy and an x-ray diffraction test. Results indicate that RCP decreased concrete workability, and increased setting time and fresh density. Furthermore, improvements in the physical properties of concrete were noted with 5.0% RCP substitution which shows 25% and 13.8% lower water absorption and permeability at 28 days. The SEM and XRD results reveal that RCP possesses micro-filling and cementitious properties.

Fatigue of SFRC in compression: Size effect & autogenous self-healing

This review synthesizes prior research on size effect and autogenous self-healing in steel fiber-reinforced concrete (SFRC) under compressive fatigue. It explores the fatigue behavior of SFRC, focusing on fiber reinforcement’s role in post-cracking toughness, crack propagation, and fatigue endurance. The review demonstrates that larger SFRC specimens have reduced fatigue lives, attributed to increased elastic energy driving microcrack growth, aligning with classical size effect theory. Additionally, it highlights autogenous self-healing, where fatigue-induced microcracks release occluded water, promoting rehydration and calcium carbonate precipitation, which enhances residual strength. The interaction between size effect, fiber content, and self-healing is examined, offering insights into improving SFRC’s durability under cyclic loading. These findings have practical implications for designing SFRC structures subjected to compressive fatigue, such as wind turbine towers and railway slabs.

Effect of Fiber Reinforcement on the Flexural Strength of Long-Span, 3D-Printed, Interim Fixed Dental Prosthesis.

To inspect the impact of polyethylene fiber (Ribbond) on the long-span, 3D-printed, interim fixed dental prosthesis regarding fracture strength. A stainless steel platform was fabricated to replicate the partial edentulism for a maxillary four-unit fixed dental prosthesis. The prosthesis was fabricated by a Formlabs SLA 3D printer. The specimens were allocated into four groups of 20 each: experimental reinforced Group A (prosthesis with a slot reinforced with fiber); experimental Group B (prosthesis with a slot filled with 3D-printed material), negative control Group C (prosthesis with a slot); and control Group D (full-contour prosthesis). Fracture strength exams were performed with a universal tester. The fracture patterns were examined. A statistical analysis was conducted using one-way ANOVA and Tukey HSD test. The control group exhibited a significantly higher mean flexural load (D: 306.32 ± 50.76 N) compared to the other groups (A: 194.37 ± 68.02 N; B: 178.25 ± 42.67 N; and C: 156.68 ± 29.73 N; [P < .001]). No differences were identified among Groups A, B, and C. The fracture pattern differed between the nonreinforced Groups B, C, and D and reinforced Group A, with catastrophic failure observed in the nonreinforced group and unseparated failure observed in the reinforced group. The study findings demonstrate that the incorporation of Ribbond in 3D-printed, interim fixed dental prostheses does not significantly enhance their fracture strength. However, it does lead to a noticeable change in the fracture behavior, shifting from a complete failure to an incomplete fracture pattern.

Predicting the Tensile Properties of Carbon FRCM Using a LASSO Model

The use of Fibre Reinforced Cementitious Matrix (FRCM) for structural retrofitting requires prior assessment of the composite’s mechanical properties, particularly its tensile stress–strain response. This paper presents a LASSO regression model applied to 107 uniaxial tensile tests on Carbon FRCM in order to investigate the impact of both the material and testing parameters on FRCM performance. A highly effective LASSO regression model was trained using k-fold validation, resulting in concise and comprehensible models. Within the testing parameters, both the gripping system and load–speed ratio significantly affected the performance. A substantial impact on ultimate values was found for the load–speed ratio. From the material-related parameters, the most influential was the textile coating in terms of strength and the existence of bilinear or trilinear behaviour. It was also concluded that the combination of textile and matrix properties influenced the stress–strain response at all stages, with high-performance mortars resulting in better textile-to-matrix interaction.

Effects of discrete fibre reinforcements on the wear resistance behaviour of polyamide-based spur gears

Abstract In many situations, the polymer gears are the perfect replacement for traditional metal gears. Compared to metal gears, the polymer gears will generate more heat at the gear tooth contact surface and more wear loss. Hence, this study aims to decrease the wear loss and increase the load-carrying capacity of the polymer gears. To achieve this, the reinforcement materials were added to the base polymer gear material. In this study, Nylon-66 was chosen as the polymer matrix material and an isolated glass fibre and steel grid were used as the reinforcement materials. Three different types of polymer spur gears such as Polyamide Gear (Nylon-66), Reinforced Polyamide Gear (Nylon-66+Glass Fibre), and Hybrid Glass Fiber Steel Grid Gear (Nylon-66+Glass Fibre+Steel Grid) named PG, RPG and HGFSGG were fabricated using injection moulding machine and each type of gears were compared for wear loss and specific wear rate under the similar testing conditions. The wear test was performed in the Forschungsstelle fur Zahnrader und Getriebebau (FZG) test rig at 1500 rpm with an applied load of 20 N for 12.5 hours continuously. From the test results, it was identified that HGFSGG polymer spur gears have exhibited a lower surface temperature and better wear properties compared to the other two types of spur gears. From the Scanning Electron Microscope (SEM) analysis, it was noticed that the PG spur gear exhibited deep and uniform wear at the gear tooth surface. In contrast, RPG spur gear exhibited glass fibre distortion and abrasive-type wear. The SEM micrograph of HGFSGG spur gear reveals the presence of very few surface flaws in the gear tooth surface.

Tensile strength study of mensiang (scirpuss grossus) fibre composites with unsaturated polyester resin matrix

The mensiang (scirpuss grossus) is a plant that grows on moist and watery land. Mensiang plants are commonly used by the society to produce mats or bags that have a strong and durable texture. This mensiang plant has fibres that can be used as reinforcement in polymer composites as a substitute for synthetic fibres. In composite manufacturing, one of the important factors in determining strength is the fraction between fibre and matrix. This study was conducted to determine the effect of different volume fractions of composites on the tensile strength of mensiang fibre reinforcement. Extraction of fibre from the stem of the mensiang plant was done manually by combing, so that the fibre was obtained. The fibres were then naturally dried by the sun for 2-3 days. The composite manufacturing process was carried out by using the hand lay-up method. Specimens and tensile testing procedures refer to the ASTM D638 standard. Several specimens were made by varying the fibre and matrix fractions. The test results showed that the 12.5% fibre volume fraction had the highest tensile strength. In this study there was no chemical treatment on the fibres before the lamination process, thus, this can be suggested for future researchers to study on the effect of chemical treatment on mensiang fibres on fibre bonding with the matrix.

Numerical study on the flexural and shear behavior of steel fiber and high‐strength steel combination in ultra‐high‐performance fiber‐reinforced concrete beams under cyclic loading

AbstractFiber‐reinforced concrete consists of hydraulic cement, water, aggregate, and discrete fibers, making it a composite material. These fibers, available in different shapes, sizes, and materials such as steel, polymer, glass, and natural fibers, are commonly utilized in structural applications. The tensile strength of conventional concrete tends to decrease as micro‐cracks develop rapidly under applied stresses. However, incorporating closely spaced fibers can hinder the progression of micro‐cracks, leading to a substantial improvement in both tensile and flexural strengths of concrete. Furthermore, fibers can delay the initiation of tensile cracks, effectively enhancing concrete's ability to withstand tensile strains before failure. As a result, fiber‐reinforced concrete exhibits increased durability and enhanced resistance to impacts compared to plain concrete. This study aims to evaluate and compare the cyclic flexural behavior of a cantilever beam constructed from ultra‐high‐performance fiber‐reinforced concrete (UHPFRC) using reinforcing bars made of high‐strength steel (HSS). The beams contain varying relative proportions of longitudinal reinforcement and steel fibers. Various key performance parameters of the cantilever beam were thoroughly examined, such as load capacity, flexural ductility, failure mode, hysteresis response, energy dissipation, and hardness. The study demonstrated that UHPFRC beams with HSS exhibit good cyclic flexural performance prior to failure.

Design of a two-seater seaplane wing spar structure with composite materials

A two-seater, mono-wing seaplane was initially developed for survey and rescue operations, with an empty weight of 470 kg and a maximum takeoff weight of 650 kg. Fiber-reinforced composite materials, consisting of fiber reinforcement and thermosetting polymer, were used in this airframe to reduce weight because the structural properties can be customized by adjusting the orientation of the fiber fabric layup and removing redundant material, which is impossible with metal. This paper presents a comprehensive overview of the design process for the aircraft's primary I-beam wing spar, employing composite material. Before conducting design calculations, it is critical to consider the variability of characteristics of composite materials caused by fabrication conditions such as temperature, humidity, and defects. As a result, it is imperative to conduct thorough testing of carbon fiber-reinforced composites following many different testing requirements. The coupon tests capture critical characteristics such as strength, stiffness, and Poisson's ratio across several orientations. The wing spar I-beam structure was subsequently developed with three primary considerations: stiffness (maximum deflection), strength, and stability (structural buckling). Following preliminary sizing of the I-beam wing spar, a simple initial layup was recommended, with primary loading in each component. The initial design was then subjected to a more detailed calculation using classical lamination theory, which took into account distributed load along the wing, spar taper, ply-drops along the span, and composite layup guidelines in order to reduce structural weight while ensuring the main spar's ability to withstand operational loads effectively. The calculating results show that the spar with an optimized composite design has a lighter weight than the original design by around 43%, while it can withstand the same loads with no analytical failure.

Experimental and Simulation Study of Fiber-Reinforced and Foam-Filled Anti-Tetrachiral and Re-Entrant Structures

Negative Poisson's ratio (NPR) honeycomb structures exhibit excellent properties, including resistance to compression, impact resistance, and energy absorption. To better study NPR structures, this paper investigates two different methods to enhance the mechanical properties and energy absorption capabilities of re-entrant and anti-tetrachiral structures. Fiber reinforcement and polyurethane foam filling methods were used to address material enhancement issues, aiming to achieve structures with high specific energy absorption. Specimens were fabricated using selective laser sintering technology with three different material configurations, including nylon, carbon fiber-reinforced nylon, and glass fiber-reinforced nylon, for comparative analysis. Additionally, some specimens were filled with polyurethane foam. Quasi-static compression tests indicated that both glass fiber-reinforced nylon and foam filling significantly improved the material's stiffness, initial peak stress, and energy absorption, although the "auxetic" effect was weakened. Subsequently, finite element methods were used to simulate the deformation modes and mechanical properties of the two NPR structures, and the numerical results showed good agreement with the experimental results.

Sensitivity analysis of carbon fiber reinforced asphalt pavements: Experimental study and data driven predictive model using machine learning

It is well known that the impact of fibers on reinforcing asphalt pavement (AP) has been extensively investigated. However, the optimal fiber length and content considering various temperatures is still an unresolved issue in this field. To reach this goal, this research aims to study the impact of carbon fiber (CF) reinforcement on the fracture energy and toughness of AP under varying environmental conditions. Several mix designs considering different CF length (10–30 mm) and content (1–3.5 %) at 5 °C and ambient temperatures were evaluated to determine the optimal values. The results demonstrated that while increasing CF length and content generally improves fracture energy and toughness, there is an optimal threshold beyond which additional CF content yields diminishing returns. Notably, the sample with a 1.5 % replacement ratio and 15 mm CF length exhibited superior performance, significantly enhancing the AP’s resistance to fracture due to effective stress distribution and crack bridging. Conversely, samples with the higher fiber content and length showed decreased fracture toughness, due to fiber clustering and reduced workability. Additionally, experimental results indicated higher values at 5 °C for fracture energy and toughness. Advanced machine learning techniques were also utilized to develop predictive models to accurately simulate the fracture behavior of CF-reinforced AP mixtures. Among all models, Gaussian process regression demonstrated superior performance and exhibited lower error in predicting experimental data. Moreover, a sensitivity analysis of this model was conducted to determine how the length and content of CF, as well as temperature, influence fracture energy and toughness, guiding the optimization of CF integration in AP design. These findings provide valuable insights for engineering durable and resilient asphalt pavements capable of withstanding diverse climatic stresses, ultimately contributing to more sustainable and cost-effective infrastructuresolutions.

Machinability investigation on CNC milling of recycled short carbon fiber reinforced magnesium matrix composites

Abstract This study investigates the machinability of magnesium matrix composites reinforced with short carbon fibers, which represent novel materials in the field. AZ91 alloy and its composites containing 2.5 and 5 wt% recycled carbon fiber (rCF) reinforcements were used as workpieces. Face milling was conducted using uncoated carbide cutting tools under dry cutting conditions with varied cutting speeds (480–560–640 m min−1) and feed rates (0.65–0.8–0.95 mm min−1). The experimental design was based on the Taguchi L9 (33) orthogonal array. Analysis included cutting forces, surface roughness, wear on cutting inserts, and chip morphology to assess machinability. Taguchi, analysis of variance, and regression methods were employed to analyze cutting force and surface roughness results. Findings indicated satisfactory machinability for AZ91 alloy and comparatively poorer performance for the 5 wt% rCF reinforced composite, with increased reinforcement content correlating with higher cutting force and surface roughness. SEM and EDX analyses revealed significant built-up layer formation on cutting inserts, with predominantly spiral-shaped continuous chips observed in the experiments. Overall, the study affirmed the machinability of the composites and identified suitable cutting parameters for further investigations.

Economic and Sustainable UHPC at Scale: Material Variability Study and Application to Full Axial Columns

The high cost of robust UHPC of a proprietary nature and expensive constituents hinders mass production and expansion into full structural applications. This study provides experimental research and validation to support new initiatives in scalable, economical UHPC of a semi-proprietary nature that leverages local and sustainable materials and explores the use of raw recycled tire fibers. The study provides comprehensive material trials and mechanical characterization validated through the fabrication and testing of five full-scale axial UHPC columns with varying reinforcement ratios, fiber ratios, and types of fibers. Overall, the result shows that incorporating local and sustainable components into proprietary mixtures does not compromise the mechanical properties of UHPC with compressive strength of more than 150 MPa and modulus of elasticity ranging from 41.8-43.4 GPa. In addition, the axial strength capacity of economical UHPC columns, designed accordingly with ACI, performed better than non-ACI-compliant columns by up to 26.8%.

Comparative analysis of flexural strength prediction in SFRC using frequentist, Bayesian, and Machine Learning approaches

Steel fiber reinforcement significantly enhances the flexural strength of concrete, which is vital for structural integrity. Annex L of the new Eurocode 2 classifies steel fiber-reinforced concrete by its flexural performance, aiding engineers in designing resilient structures. This study investigates the flexural behavior of steel fiber-reinforced concrete (SFRC) using three data-driven methodologies: Frequentist Inference (FI), Bayesian Inference (BI), and Machine Learning (ML). A comprehensive database was constructed from three-point bending tests on SFRC specimens, encompassing various compressive strengths, fiber quantities, and geometric parameters, to identify key factors influencing material properties.The findings indicate that all three methodologies yield comparable predictive capabilities for flexural responses in SFRC. Notably, FI models emphasize the importance of compressive strength and fiber volume fraction, along with fiber properties such as non-dimensional length and tensile strength. BI models enhance predictive stability by integrating prior knowledge and quantifying uncertainty, demonstrating their advantage, particularly in data-scarce situations. Additionally, ML analysis reveals that linear regression (LR) models can achieve accuracy similar to or greater than that of more complex models. This research provides novel insights into the application of BI and ML in concrete technology, emphasizing their potential to enhance predictive modeling. Additionally, it offers practical guidelines for optimizing SFRC design through a case study that compares residual flexural strengths obtained via Bayesian analysis, classifying the material in accordance with Annex L of the new Eurocode 2.

Implementation of multi-walled carbon nanotube incorporated GFRP as an alternative for CFRP in strengthening of concrete cylinders

Carbon fibre is the most widely utilized fibre for strengthening and retrofitting applications in the construction sector. The high cost of carbon fibre necessitates the identification of an alternative system for the retrofitting and repairing of concrete structures. In the current study, the characteristics of Glass Fibre Reinforced Polymer (GFRP), Carbon Fibre Reinforced Polymer (CFRP), and Multi-Walled Carbon Nanotube (MWCNT) incorporated GRFP are assessed with epoxy as a matrix for concrete cylinder confinement. The evaluation of one and two-layer CFRP confinement on concrete cylinders is carried out and outcomes are compared with the three-layer MWCNT incorporated GFRP confinement. A significant increase was observed in the axial compressive load-bearing capability of specimens with 1 wt percentage (wt%) MWCNT incorporated GFRP confined concrete cylinders. The axial load-carrying capability of concrete specimens with one layer of CFRP confinement was equivalent to that of specimens with 1 wt% MWCNT incorporated three-layer GFRP confinement. The axial strain of MWCNT incorporated three-layer GFRP confined specimens was 75 % more than one-layer and 12 % higher than two-layer CFRP confined specimens. According to observations, MWCNT-incorporated FRP confinement improves the energy absorption and ductility index. Ultrasonic pulse velocity test results confirmed the potency of three-layer GFRP confinement as a replacement for one and two layers of CFRP. A cost analysis is also carried out to validate the economic viability of the MWCNT-based GFRP compared to CFRP confinement.

Mechanical performance and self-sensing capability of an amorphous fiber-reinforced concrete for radioactive waste storage facilities

This study results from a research project initiated by the French National Radioactive Waste Management Agency (Andra) as a part of the Cigéo (Industrial Center for Geological Disposal) project. This project addresses many challenges related to sustainability, and health monitoring of confinement structures planned by Andra. In order to reduce issues related to corrosion in the tunnels, fiber reinforcement can be used to reduce the amount of steel reinforcement while maintaining high mechanical performance and durability. The fibers used in this study are named Fibraflex, metallic fibers provided by Saint Gobain SEVA. Various aspect ratios (82 and 123) and volume ratios (0.27% and 0.41%) of fibers were tested. These fibers feature high specific surface area (around 70 m2/m3), corrosion resistance, and high electrical conductivity. To characterize the contribution of fibers to concrete mechanical performances, European standard EN 14651 flexural tensile tests were conducted. Results show that fibers bring better performances, especially concerning the post-peak behavior. In fact, fibers effectively transfer stresses across cracks, resulting in better residual tensile strengths. Since these fibers are electrically conductive, tests were also conducted to design self-sensing concrete based on electrical measurements. Firstly, resistivity was monitored on saturated specimens with different mix design throughout the curing time. Results show that when fibers were added, concrete resistivity was reduced due to the ability of the fibers to transmit electrons. A relationship between reinforcement index and resistivity was thus revealed. The self-sensing capacity was investigated on specimens subjected to cyclic bending loading, with electrical properties measured by using a Wheatstone bridge. Results show a good agreement between the level of cracking in concrete and its electrical response.

Environmental Impact Assessment of Natural Vs Synthetic Fiber Reinforcement in Polymer Composites

Environmental Impact Assessment of Natural Vs Synthetic Fiber Reinforcement in Polymer Composites

Assessment of fiber alignment through combined driven oscillatory and directional magnetic fields in matrix with similar rheological behavior to cementitious materials

In this paper a novel method to improve the effectiveness of the aligning of fibers used as reinforcement in Fiber Reinforced Cementitious Composites (FRCC) through directional homogeneous magnetic fields is proposed. A combination of homogeneous magnetic fields, oscillatory and directional, are assessed as a new method for fiber aligning which increase the aligning index and mechanical efficiency index of the fiber in cementitious composites. Fresh cementitious materials present a Static Yield Stress (T0s), which must be overpassed to allow the rotation of the fiber immersed in the matrix. To reduce the T0s of the matrix, oscillatory magnetic fields (OMF) are applied firstly, as they generate a vibrational strain of the fiber. Later, fibers are aligned through a directional magnetic field which finds a lower opposition of the rheological torque. The fibers are subjected to an orientation rotation caused by the magnetic field, which is caused by a magnetic torque. This torque is opposed by two torques, one of rheological origin (Yield stress and viscosity) and another of inertial type (geometry and mass distribution of the fiber). The rheological torque is the torque that opposes to the rotation of the fiber and is a function of the rheological properties of the matrix. Two pairs of Helmholt coils have been used in this research, to be able to generate orthogonal magnetic fields to directional magnetic fields. When the OMF was generated, one of the pair of coils were connected to the net, with a frequency of 50 Hz. OMF was performed in 0.64mT-1.25mT-2.18mT. To evaluate its effectiveness each of them was applied in periods of time of 2–5–7–10 seconds before the directional magnetic field of 30 mT. To assess the method steel fibers has been submerged in a metaphor fluid to reproduce the rheological properties of cement materials. The initial and final angles of the batch of fibers have been determined through photography and Computer-aided design. The results obtained shown that the use of OMF increases the alignment index up to 35 % and the mechanical efficiency rate up to 24.35 % in the batches studied. The research followed also showed that previous vibration can be applied during periods of 5 seconds, with the same pair of coils that for aligning but also the use of the two pair of coils can be used simultaneously.

Study and mechanism analysis on fracture mechanical properties of steel fiber reinforced recycled concrete (SF-R-RC)

Recycled concrete has deficiencies in its overall performance due to the deteriorated properties of the recycled aggregate (RA) used. Based on the RA characteristics and fiber reinforcement mechanism, designing recycled concrete by adding steel fiber (SF) and enhancing RAs in a coordinated manner can effectively improve the overall performance of recycled concrete. Therefore, this paper considers the SF content and RA enhancement to study the fracture mechanical properties of steel fiber reinforced recycled concrete (SF-R-RC), and the main conclusions are as follows: the fracture mechanical properties of SF-R-RC are significantly affected by aggregate enhancement and SF content. Without the SFs, the strengthened coated recycled aggregate concrete (CRAC) was better than unreinforced recycled aggregate concrete (RAC) in terms of the unstable fracture load, fracture energy, initial fracture toughness and unstable fracture toughness, but weaker than normal aggregate concrete (NAC). The increase in the unstable fracture load, fracture energy, initial fracture toughness and unstable fracture toughness of NAC, RAC and CRAC with the increase in SF content was observed, with CRAC showing the most significant increase in these fracture parameters. Applying digital image correlation (DIC) and acoustic emission (AE) techniques, the effect of SF content and RA enhancement method on the crack evolution process and damage distribution law of SF-R-RC was studied. Meanwhile, the microscopic testing technique was used to reveal the mechanism of the influence of SF and RA enhancement on the fracture mechanical properties of SF-R-RC. The research results of this paper provide a theoretical basis for the application of RA enhancement and SF reinforcement methods of recycled concrete in practical engineering.