Discrete Fiber Research Articles

A study for effect of steel fibre on strength of conventional concrete

Discrete discontinuous fibre reinforced concrete (FRC) is a composite material made up of Portland cement, aggregate, and discrete discontinuous fibres used to construct bridges and other structural components. Why would we want to put such fibres in concrete in the first place, anyway? Plain, unreinforced concrete is discouraged because it is a fragile, low-tensile-strength, low-strain-capacity material that should be avoided if possible. A random distribution of discontinuous fibres was intended to bridge over fractures as they expanded, restoring the material's “ductility” after the cracks had developed. Fibre reinforced concrete (FRC) can endure considerable pressures with a reasonably high strain capacity at the post-cracking stage due to the strength and connection of the fibres to the concrete, provided the fibres are sufficiently strong and well-bonded to the concrete. There are, however, other (and more cost-effective) ways to increase the strength of concrete than the ones listed above. The fibres' most significant contribution is to enhance the toughness of the concrete, regardless of the kind of force applied to it. As a consequence, although the fibres have a tendency to increase strain at peak load, they also absorb a significant amount of energy throughout operation in the post-peak section of the load vs. deflection curve. Fiber reinforcement in the form of short, discrete fibres functions as stiff inclusions in the concrete matrix and is a very efficient means of reinforcing concrete. In terms of particle size and number, they are comparable to aggregate inclusions. It is believed that conventionally reinforced structural elements will be more resistant to cracking, deflection, and other issues that impact serviceability.

OXIDE-CONTAINING MINERAL FIBERS: TYPES, METHODS OF PRODUCTION, APPLICATION AND MANUFACTURERS (REVIEW)

The article provides an overview of mineral oxide fibers of various chemical composition: aluminosilicate, alumina, silica, bio-soluble, zirconium oxide fibers and others. Methods for producing discrete and continuous fibers, such as spinning fibers from melts, sol-gel technology, spinning from solutions of metal salts, etc., are described. filtration for alumino-silicate and bio-soluble fibers; thermal insulation up to 1600 or 2000 C and reinforcement of composites used in the aerospace and defense industries for alumina fibers and fibers based on zirconium dioxide, etc. Producers of mineral oxide-containing fibers and products based on them abroad and in Russia are represented.

Shear strength of steel fiber reinforced concrete beam– A review

The use of randomly distributed and discrete steel fibers in concrete (SFRC) offers better resistance to early crack growth and possesses better post peak strain capacity. The crack bridging effect of steel fiber due to the fiber matrix interaction reduces the rate of crack growth and restricts spalling of concrete which improves the toughness characteristics. The deployment of SFRC in RC beams, columns and beam-column joints improves the shear resistance by acting as secondary shear reinforcement along with the optimum conventional confining reinforcement. The ductility enhancement and damping properties of SFRC becomes an effective solution for enhancing the seismic resistance of structural member. The shear resistance capacity of SFRC elements is mainly controlled by the volume of fiber, profile and steel fiber aspect ratio. Many studies have been conducted to examine the shear strength of RC beams with SFRC and empirical models have been proposed to estimate the contribution of steel fiber in shear resistance. This research article summarizes the different empirical models in shear strength evaluation of SFRC beams with and without stirrups.

УЗК-ДОСЛІДЖЕННЯ ВПЛИВУ ВУГЛЕЦЕВИХ ВОЛОКОН НА ВЛАСТИВОСТІ ВУГЛЕПЛАСТИКІВ НА ОСНОВІ ПОЛІФЕНІЛЕНСУЛЬФІДУ

Polyphenylene sulfides are one of the plastics with truly outstanding characteristics. The introduction of carbon fibers into the composition of the matrix contributes to the expansion of their potential use. The main requirement for the obtainedmaterialsis to increase their strength indicators due to the reinforcement of the matrix frame with carbon fibers.Carbon plastics are distinguished among other composite materials by high specific strength and stiffness, low coeffi-cients of linear thermal expansion and friction, high wear resistance and resistance to aggressive environments. This allows their use in defense industries and, above all, in aviation and rocket engineering.The analysis of the latest research and publications showed that the issue of selection and distribution of carbon fiber has a strong influence on the final indicators of the material's properties. To improve the operational characteristics, discrete carbon fibers were introduced into the composition of polyphenylene sulfide. The main goal of this method of obtaining com-posites was the uniform distribution of fibers in the polymer matrix.The article presents the results of mechanical tests of polyphenylene sulfide and carbon plastics based on it, the main indicators are determined: strength, relative deformation and modulus of elasticity, microhardness. It is shown that the method of acoustic defectoscopy -ultrasonic control can be used to assess the strength characteristics of compositions based on poly-phenylene sulfide. A non-destructive approach to the study of carbon plastics based on polyphenylene sulfide is proposed, which results correlate with laboratory studies of material properties. The pulses of the reflected "bottom" signals are given and the speed of wave propagation in the material is determined.The analysis of the physical and mechanical properties showed that the resulting carbon-plastics are characterized by fairly high strength indicators, which makes it possible to recommend them for replacing thermoplastic and thermosetting polymers, especially in machine building.

Use of Discrete fiber in road pavement

Concrete roads are very linear, linear route meansa route that progresses from a starting to an ending point. The beginning and end of a linear route do not meet, but may connect to another route or a destination point and can provide a safe and smooth flow of traffic. Due to the use of concrete in roads it has become quite an advantage for a greater life span and low maintenance. But concrete roads may undergo cracking, spalling and concrete is weak in tension and also little ductility. So as to reduce these problems Inclusion of fiber can provide a great benefit to concrete pavement. This Research “The Use of Discrete Fiber in Road Pavements” is done so as to improve the quality of concrete pavement. In this research the fiber used is polypropylene fiber and polyester fiber. The concrete mix used is M25. (Nominal mix ratio of m25 grade of concrete is1:1:2, mixture of cement, sand, aggregate and water in which one part is cement, one part is sand and two part is aggregate and water cement ratio is 0.4 to 0.6.0). In one specimen only plain, concrete mix is tested for compressive strength, flexural strength and split tensile strength. In second specimen 1.8% of polypropylene fiber is added with the concrete mix and again tested for the same three tests. In the third sample 0.5% of polyester fiber is used in the concrete mix and tested for compressive strength, flexural strength and split tensile strength. In fourth specimen both 1.8% of polypropylene fiber and 0.5 % of polyester fiber is mixed with the concrete mix and tested for the three tests It was seen a large increment in the strength which showed the addition of fiber can improve the quality of concrete.

A Discrete Fiber Network Finite Element Model of Arterial Elastin Network Considering Inter-Fiber Crosslinking Property and Density

A Discrete Fiber Network Finite Element Model of Arterial Elastin Network Considering Inter-Fiber Crosslinking Property and Density

A review of the implementations of glass fiber in concrete technology

Concrete Technology is the science and art of proportioning raw materials in order to produce concrete that satisfies specified mechanical, stiffness, and workability specifications. That is, evaluating the properties of concrete and its components under a variety of conditions and mixtures. Fiber Reinforced Concrete (FRC) is reinforced by the irregular, isolated, and evenly distributed fibres. FRC is available in a variety of forms and qualities, offers numerous benefits, and is a one-of-a-kind reinforcing material. Fibrous material strengthens the structure of FRC. It is composed of thousands of tiny discrete fibres that are randomly oriented and dispersed. Cement and alkali-resistant glass fibres are used to make glass fibre reinforced concrete (GFRC). The fibres are used to reinforce reinforced concrete in place of steel reinforcing bars, adding flexural, tensile, and impact strength. This enables the production of structural concrete products such as wall panels that are both strong and lightweight. GFRC can also be used to create beautiful concrete products such as façade wall panels and concrete work surfaces. Due to its adaptability, durability, and light weight, the majority of concrete experts use GFRC. The article's primary objective is to educate the public about new, practical, and cost-effective technology. The article's primary objective is to inform readers about emerging low-cost technologies. Additionally, the paper discusses current GFRC applications.

Effects of dispersed fibres in myocardial mechanics, Part I: passive response.

It is widely acknowledged that an imbalanced biomechanical environment can have significant effects on myocardial pathology, leading to adverse remodelling of cardiac function if it persists. Accurate stress prediction essentially depends on the strain energy function which should have competent descriptive and predictive capabilities. Previous studies have focused on myofibre dispersion, but not on fibres along other directions. In this study, we will investigate how fibre dispersion affects myocardial biomechanical behaviours by taking into account both the myofibre dispersion and the sheet fibre dispersion, with a focus on the sheet fibre dispersion. Fibre dispersion is incorporated into a widely-used myocardial strain energy function using the discrete fibre bundle approach. We first study how different dispersion affects the descriptive capability of the strain energy function when fitting to ex vivo experimental data, and then the predictive capability in a human left ventricle during diastole. Our results show that the chosen strain energy function can achieve the best goodness-of-fit to the experimental data by including both fibre dispersion. Furthermore, noticeable differences in stress can be found in the LV model. Our results may suggest that it is necessary to include both dispersion for myofibres and the sheet fibres for the improved descriptive capability to the ex vivo experimental data and potentially more accurate stress prediction in cardiac mechanics.

Improving Bond Strength of Bonded Concrete Overlay by Adding Synthetic Discrete Fibers

Improving Bond Strength of Bonded Concrete Overlay by Adding Synthetic Discrete Fibers

STRUCTURE FORMATION OF DISPERSED-REINFORCED BUILDING COMPOSITES

Abstract. The results of the study of the mechanism of structure formation of cement compositions reinforced with finely dispersed monofilament are presented in the article. The mechanism of microstructure organization of construction composites was studied on models of dispersed systems, with different qualitative and quantitative composition of linear and dispersed particles. At the same time, restrictions had been placed on particle size – fiber diameter and diameter of dispersed particles are proportional to each other. Study of cracking formation kinetics was carried out on disk-shaped samples made of water-clay and water-cement compositions. Physical and mechanical characteristics of dispersed-reinforced cement stone, including non-reinforced stone, have been defined on prisms-shaped samples of square section with size 40×40×160 mm. The analysis of physical models showed that cluster structures filling with particles of various nature and shape increases structural diversity of entire dispersed system. An inserting of linear particles changes nature of system structure formation. Depending on the characteristics, structural components of the system, substructures are formed, which differ in the periods of their formation and geometric parameters. It has been established that dispersed particles of different nature are structured in different ways into clusters with discrete fibers of different length. Linear particles were more active in the creation of structural aggregates (clusters) comparing to dispersed grains. The impact of highly dispersed fibers on the structure organization of the binder compositions was quantified by the damage coefficient determined on samples of different types. The presence of discrete fibers in the composition of the material leads to modify the qualitative characteristic of compositions cracking formation. Improvement of physical and mechanical properties of the dispersed-reinforced composite confirms the ability of the fiber to change a mechanism of material destruction due to a probable deposition of hydration products on monofilaments, to densify and strengthen the interfacial transitional zone.

Application and Analysis of Discrete Fiber Probes in Determining Detonation Velocity of Microcharges.

This paper describes a method based on discrete fiber probes for measuring detonation velocity produced by microcharges. This method is simple to implement, scalable for multi-channel and requires minimal perturbation to the detonation wave. A simple experimental apparatus was established by using the oscilloscope, photodetectors, optical fibers, alignment device and initiation system. Four groups of experiments were carried out for analyzing the influence of probe spacing on detonation velocity. The experiment results suggest that a relatively appropriate distance between two adjacent fiber probes is 4 mm. In addition, the comparative experiments between ionization probes and fiber probes were performed, which shows that the standard deviation of detonation velocity obtained by fiber probes is smaller under the same measurement conditions. This research may be useful for the development of determining detonation velocity precisely of microcharges.

Experimental Study on Evaluation of Replacing Minimum Web Reinforcement with Discrete Fibers in RC Deep Beams

This study investigates the possibility of replacing the minimum web reinforcement in deep beams with discrete fibers. Additionally, the equivalent dosage of fibers required to obtain similar performance of the deep beam with minimum web reinforcement is investigated. Deep beams made of plain concrete with no fibers, beams with minimum web reinforcement as per AASHTO LFRD recommendations (0.3% in both horizontal and vertical), and with a 0.5% volume fraction of steel, macro-synthetic and hybrid fibers are tested at a shear span to height ratio (a/h) of one. Test results show that the presence of 0.3% web reinforcement in horizontal and vertical directions increased the peak load by 25% compared to the plain concrete beams. However, it did not significantly change the first diagonal crack load. With the addition of 0.5% of steel, macro-synthetic and hybrid fibers, the peak load increased by 49%, 42%, and 63%, respectively, compared to the plain concrete specimen. The addition of steel fibers significantly improved the first cracking load. In contrast, macro-synthetic fibers did not affect the first cracking load but improved the ductility with higher deflections at peak. Hybridization of steel and macro synthetic fibers showed improved performance compared to the individual fibers of the same volume in peak load and ductility. Test results showed that a 0.5% volume fraction of discrete macro steel or synthetic or hybrid fibers can be used to completely replace the minimum web reinforcement (0.3% in both directions).

Efficient computational modelling of smooth muscle orientation and function in the aorta

Understanding the mechanical effects of smooth muscle cell (SMC) contraction on the initiation and the propagation of cardiovascular diseases such as aortic dissection is critical. Framed by elastic lamellar sheets in the lamellar unit, there are SMCs in the media with a distinct radial tilt, which indicates their contribution to the radial strength. However, the mechanical effects of this type of anisotropy have not been fully discussed. Therefore, in this study, we propose a constitutive framework that models the passive and active mechanics of the aorta, taking into account the dispersed nature of the aortic constituents by applying the discrete fibre dispersion method. We suggest an isoparametric approach by evaluating various numerical integration methods and introducing a non-uniform discretization of the unit hemisphere to increase its computational efficiency. Finally, the constitutive parameters are fitted to layer-specific experimental data and initial computational results are briefly presented. The radial tilt of SMCs is also analysed, which has a noticeable influence on the mechanical behaviour of the aorta. In the absence of sufficient experimental data, the results indicate that the active contribution of SMCs has a remarkable impact on the mechanics of the healthy aorta.

Mechanical Properties of Hybrid Structures Incorporating Nano-Silica and Basalt Fiber Pellets

Recently, developing a nonferrous reinforcement system (corrosion-free system) using durable and ductile cement-based materials that incorporate discrete fibers has been a promising option for exposed concrete structures in cold regions or marine environments. Therefore, in this study, properties of a novel type of cementitious composite comprising nano-silica and a high dosage of slag were investigated. The hybrid (layered) composites assessed in this study were composed of two layers of different types of cementitious composites. Normal concrete (NC) was used in the top layer combined with a layer of fiber-reinforced cementitious composite (FRCC) reinforced with either the recently developed basalt fiber (BF) pellets (basalt fiber strands encapsulated by a polymeric resin or steel fibers (SF)) that were used at different dosages. The post-cracking behavior in terms of residual strength, residual index, and toughness are presented and discussed. The analysis of results showed the effectiveness of the BF pellets in enhancing the post-cracking behavior of specimens, as they behaved comparably to counterpart specimens comprising SF, which makes them a good candidate for infrastructural applications including rehabilitation such as new bridge girders or overlays.

Regional variations in discrete collagen fibre mechanics within intact intervertebral disc resolved using synchrotron computed tomography and digital volume correlation

Many soft tissues, such as the intervertebral disc (IVD), have a hierarchical fibrous composite structure which suffers from regional damage. We hypothesise that these tissue regions have distinct, inherent fibre structure and structural response upon loading. Here we used synchrotron computed tomography (sCT) to resolve collagen fibre bundles (∼5μm width) in 3D throughout an intact native rat lumbar IVD under increasing compressive load. Using intact samples meant that tissue boundaries (such as endplate-disc or nucleus-annulus) and residual strain were preserved; this is vital for characterising both the inherent structure and structural changes upon loading in tissue regions functioning in a near-native environment. Nano-scale displacement measurements along >10,000 individual fibres were tracked, and fibre orientation, curvature and strain changes were compared between the posterior-lateral region and the anterior region. These methods can be widely applied to other soft tissues, to identify fibre structures which cause tissue regions to be more susceptible to injury and degeneration. Our results demonstrate for the first time that highly-localised changes in fibre orientation, curvature and strain indicate differences in regional strain transfer and mechanical function (e.g. tissue compliance). This included decreased fibre reorientation at higher loads, specific tissue morphology which reduced capacity for flexibility and high strain at the disc-endplate boundary. Statement of significanceThe analyses presented here are applicable to many collagenous soft tissues which suffer from regional damage. We aimed to investigate regional intervertebral disc (IVD) structural and functional differences by characterising collagen fibre architecture and linking specific fibre- and tissue-level deformation behaviours. Synchrotron CT provided the first demonstration of tracking discrete fibres in 3D within an intact IVD. Detailed analysis of regions was performed using over 200k points, spaced every 8 μm along 10k individual fibres. Such comprehensive structural characterisation is significant in informing future computational models. Morphological indicators of tissue compliance (change in fibre curvature and orientation) and fibre strain measurements revealed localised and regional differences in tissue behaviour.

Predicting the mechanical properties of biopolymer gels using neural networks trained on discrete fiber network data

Biopolymer gels, such as those made out of fibrin or collagen, are widely used in tissue engineering applications and biomedical research. Moreover, fibrin naturally assembles into gels in vivo during wound healing and thrombus formation. The macroscale properties of fibrin and other biopolymer gels are dictated by the response of a microscale fiber network. Hence, accurate description of biopolymer gels can be achieved using representative volume elements (RVE) that explicitly model the discrete fiber networks of the microscale. These RVE models, however, cannot be efficiently used to model the macroscale due to the challenges and computational demands of multiscale coupling. Here, we propose the use of an artificial, fully connected neural network (FCNN) to efficiently capture the behavior of the RVE models. The FCNN was trained on 1100 fiber networks subjected to 121 biaxial deformations. The stress data from the RVE, together with the total energy on the fibers and the condition of incompressibility of the surrounding matrix, were used to determine the derivatives of an unknown strain energy function with respect to the deformation invariants. During training, the loss function was modified to ensure convexity of the strain energy function and symmetry of its Hessian. A general FCNN model was coded into a user material subroutine (UMAT) in the software Abaqus. The UMAT implementation takes in the structure and parameters of an arbitrary FCNN as material parameters from the input file. The inputs to the FCNN include the first two isochoric invariants of the deformation. The FCNN outputs the derivatives of the strain energy with respect to the isochoric invariants. In this work, the FCNN trained on the discrete fiber network data was used in finite element simulations of biopolymer gels using our UMAT. We anticipate that this work will enable further integration of machine learning tools with computational mechanics. It will also improve computational modeling of biological materials characterized by a multiscale structure.

Association of Mucoid Degeneration of the ACL with Medial Tibiofemoral Osteoarthritis Progression at MR Imaging

Abstract Background Using MRI, ACL mucoid degeneration is defined as a thickened ACL with increased signal intensity on all MR pulse sequences, with discrete fibers easily distinguished on fatsaturated T2-weighted or fat-saturated proton-density (PD)-weighted images but poorly differentiated on T1-weighted or non-fat-saturated PD-weighted images. Objective To assess the prevalence of ACL mucoid degeneration in a population of patients referred for routine knee MRI, and its association with age and structural joint damage. Patients and Methods Our study is a retrospective study conducted at the radiology department of Ain Shams University hospitals and Ain Shams University Specialized Hospital including 81 cases of knees with ACL mucoid degeneration by MRI and no sex predilection. Cases and controls were scored with respect to independent articular features: cartilage signal and morphology, subarticular bone marrow abnormality, subarticular cysts, subarticular bone attrition, marginal osteophytes and medial meniscal integrity. Results Patients with ACL mucoid degeneration were older than patients with a normal ACL, without statistically significant sex difference. Knees with ACL mucoid degeneration had statistically significant medial meniscal injuries and cartilage damage involving the central and posterior MTFC compared to control knees with a normal ACL frequency matched for age, sex and MR field strength. Conclusion Our study proved that there is a strong association between ACL mucoid degeneration and cartilage damage in MTFC.

Experiments and crushing mechanism analysis of hybrid square metal tubes with filament wound CFRP

Hybrid tubular members consisting of a metal tube externally reinforced with carbon fibre have been shown to be efficient energy absorbers. Several studies have used filament winding techniques to fabricate hybrid tubes, principally with circular cross-sections. Filament winding allows for a wide range of discrete fibre orientations. The present study develops an analytical technique to predict the mean crushing force of hybrid square tubes with arbitrary metal tube material and arbitrary carbon fibre orientations. Initially, an experimental study of the quasi-static axial crushing of 40 hybrid square tubes with a variety of metals (steel, aluminium and stainless steel), and a variety of filament winding angles (45°, 67° and 90°) and plies, is described. Comparisons of filament wound tubes are made with previous studies by the author and co-workers of nominally identical hybrid tubes fabricated with the hand-layup method. Previous crushing mechanism theories of bonded metal-fibre square tubes are extended to consider the different metals and fibre orientations. Based on the observations in the experimental program, a new theory is developed for the case where the metal and fibre become unbonded, and is shown to compare well with the experimental data. The analytical model indicates that when the carbon fibre remains bonded to the metal throughout the crushing process, the mean crush load is on average 54% higher than when the fibre becomes unbonded. This indicates the importance of the metal-fibre bond for optimum performance of hybrid tubes.

Mechanically strong and stiff supramolecular polymers enabled by fiber reinforced long‐chain alkane matrix

AbstractFiber‐reinforced‐concrete (FRC) mechanism refers short discrete fibers that are uniformly distributed and randomly oriented, which offers an effective way to improve the mechanical performance of concrete. In the design of supramolecular polymers, an analogous concept of FRC appears to have been considered very rarely‐although fibrous structure has been frequently observed/generated during the supramolecular polymerization. In this work, we apply the alkane thermosets, octadecane (C18H38) and tetracosane (C24H50), taking the role of “concrete”, and the low‐molecular‐weight monomer with long alkyl chains as the essential “fiber” component, to fabricate the “fiber reinforced supramolecular polymer”. Very much like FRC mechanism in material science, the resulting fiber reinforced supramolecular polymer thus exhibit unusually high mechanical strength and stiffness, which is unprecedented in the conventional supramolecular strategy.

The Influence of Discrete Fibers on Mechanical Responses of Reinforced Sand in Direct Shear Tests

To investigate the influences of discrete fiber strips on the mechanical properties of reinforced sand, a series of direct shear tests were conducted. A method to strictly control the initial orientation of fiber strips in specimen preparation was developed. Under the same normal pressure, the peak strength of sand specimens was proportional to the fiber content and was inversely proportional to the fiber initial orientation angle. The influences of initial fiber orientation on peak strength may depend on the stress mobilization in fibers. When the fiber strips distributed at a certain orientation angle were subjected to tensile stress in shearing, they could play an effective role in the peak strength gain of sand and vice versa. Due to the restriction of fibers on the volume dilation of sand specimens, the residual strength of reinforced sand also increased. However, the initial stiffness of reinforced sand was smaller than that of pure sand, which may be related to the precompression of flexible fiber strips and the density inhomogeneity of specimens induced in the specimen preparation process. In addition, the ductility of sand specimens was improved by the introduction of fiber strips, intuitively reflected by the increase in displacement failure. This may also be attributed to the restriction of fiber strips on the deformation of sand specimens.