Fiber Volume Research Articles

A data-enhanced approach for early-age drying induced moisture transport analysis on in-situ casted textile fibre reinforced concrete

With the addition of textile fibres that alters pore structure, the novel Textile Fibre Reinforced Concrete (TFRC) exhibits great potential in reducing drying shrinkage and enhancing long-term durability. To advance material design, this study aims at developing a coupled experimental-numerical framework with a data-enhanced approach to identify the essential material properties that govern the moisture transportation in TFRC. The scope of analysis covers the TFRC manufactured with various fibre types and different fibre volumes, where the time-dependent effect associated with early age is investigated. An inverse analysis framework, coupling Particle Swarm Optimisation (PSO) and extended support vector regression (XSVR), is developed and validated against experimentation by monitoring moisture distribution. Results reveals that the incorporation of textile fibres leads to a substantial reduction in the moisture diffusivity of TFRC, as opposed to conventional concrete of identical w/b and aggregate content. Notably, TFRC mixtures with 0.4 % Nylon twist and PTT600 fibres showed a 95 % reduction in moisture diffusivity compared to the conventional concrete. This discovery illustrates the capability of textile fibres, when optimally introduced, to mitigate moisture loss from cementitious materials, reducing drying shrinkage of concrete building. The proposed approach is demonstrated to be able to robustly quantify the early-age moisture transportation in TFRC, which is of potential to guide future concrete design of using textile fibre reinforcement towards controlling early-age shrinkage in building industry.

Development of a 3D printer for long fiber-reinforced plastic and evaluation of the mechanical properties of printed parts

The field of three-dimensional (3D) printing, a technology that allows low-cost printing of complex 3D shapes with a high degree of modeling freedom, has exhibited significant growth over the last few years. This paper proposes a new 3D printing mechanism for long fiber-reinforced plastic as part of an effort to realize 3D-printed shapes with favorable mechanical properties and describes how prototype parts were printed using the new method. We also devise a method for modifying the fiber surface and other techniques for improving adhesion of fibers and UV resin. Mechanical testing of prototype parts printed using the proposed method indicates that the parts exhibit excellent mechanical properties as a result of filling with long fibers, indicating that the method yields a material with few voids and a high fiber volume fraction.

Strain-hardening ultra-high performance concrete (UHPC) with hybrid steel and ultra-high molecular weight polyethylene fibers

This study addresses the advancement of strain-hardening ultra-high performance concrete (UHPC) by investigating its tensile behavior with hybrid steel and ultra-high molecular weight polyethylene fibers. Through direct tensile testing of UHPC samples with varying volumes of steel and polyethylene fibers (totaling 2.0%), significant improvements in tensile strain capacity and energy absorption capacity (tensile toughness) were observed upon replacing steel fibers with polyethylene fibers. Despite marginal variations in first cracking strength and ultimate tensile strength, these properties could be finely tuned by tailing fiber length and hybrid ratio. Quantitative analysis established correlations between the hybrid fiber factor and key mechanical properties, advancing a deeper understanding of UHPC behavior. The findings underscore the benefits of multiscale fiber hybridization in UHPC, offering scientific insights into predicting and optimizing its performance for structural applications. This study helps close the gap in UHPC development, emphasizing the potential of multiscale fiber hybridization to achieve concurrently high tensile strength and strain capacity.

A material-structure coupled design method to study the impact response of CFRP apron board for railway vehicle

It is of great significance to improve the design efficiency and guide material selection for carbon fiber reinforced polymer (CFRP) vehicle structures, thereby, contributing to lightweight high-speed trains. This study proposes a material-structure integrated design approach that bridges the computational relationship between design variables across multiple scales and the impact responses of CFRP vehicle structures. Computational models are constructed at the micro-scale, meso-scale, and macro-scale to capture the multi-scale characteristics of the CFRP structures. At micro-scale, finite element simulations are used to determine the effective properties of fiber bundles using a representative volume element (RVE) model. This information is then transferred to the meso-scale RVE model to calculate the homogenized mechanical properties of the lamina. Finally, a macro-scale model is established to investigate the damage mechanisms and impact resistance of the CFRP apron board against the projectile impact. The influences of design variables, such as fiber type and volume fraction, are analyzed to provide further insights into the design of CFRP apron boards.

On the infiltration of cellular solids by sheet molding compound: process simulation and experimental validation

This study examines a numerical method to simulate the production of novel multi-material metal-composite components, where an additive-manufactured cellular solid is infiltrated by a sheet molding compound (SMC) in a single-step compression molding operation. A single-fiber numerical approach is adopted to predict microstructural changes, such as fiber orientation, fiber-matrix separation, and fiber volume content variations during molding. The accuracy of the numerical predictions is confirmed by physical samples using micro-computed tomography and optical microscopy investigations at both the qualitative and quantitative scales. From optical microscopy observations, there emerged a positive correlation between experimental outcomes and simulation results, accurately capturing fiber swirling, wrinkling, and draping that occurred during molding. At a quantitative scale, a 0.6% mismatch was observed when void volume and unfilled areas were compared, as measured by micro-computed tomography and numerical simulation.

Experimental Study of Mechanical Properties and Theoretical Models for Recycled Fine and Coarse Aggregate Concrete with Steel Fibers.

With diminishing natural aggregate resources and increasing environmental protection efforts, the use of recycled fine aggregate is a more sustainable approach, although challenges persist in achieving comparable mechanical properties. Exploration into the incorporation of steel fibers with recycled aggregate has led to the development of steel-fiber-reinforced recycled aggregate concrete. This study investigates the shrinkage performance and compressive constitutive relationship of steel fiber recycled concrete with different steel fibers and recycled aggregate dosages. Initially, based on different replacement rates of recycled coarse aggregate and different volume contents of steel fiber, experimental results demonstrate that as the replacement rate of recycled coarse aggregate increases, shrinkage also increases, while the addition of steel fiber can mitigate this effect. An empirical shrinkage model for steel fiber recycled concrete under natural curing conditions is also proposed. Subsequently, based on the uniaxial compression test, findings indicate that with an increasing replacement rate of recycled fine aggregate, the peak stress and elastic modulus of concrete decrease, accompanied by an increase in peak strain, and the addition of steel fiber limits concrete crack development and enhances its brittleness while the peak stress and strain of recycled fine aggregate concrete are enhanced. However, the steel fiber volume percentage has a negligible effect on the elastic modulus. A constitutive relationship for concrete considering the effects of recycled fine aggregate and steel fiber is also proposed. This finding provides foundational support for the influence patterns of steel fiber dosage and recycled aggregate ratio on the mechanical properties of steel fiber recycled concrete.

МЕХАНИЧЕСКИЕ СВОЙСТВА СВЕРХВЫСОКОПРОЧНОГО ФИБРОБЕТОНА С РАЗЛИЧНЫМ ВИДОМ СТАЛЬНОЙ ФИБРЫ

The article examines the influence of steel fiber type and volumetric content on the mechanical properties of UHPFRC. Five fiber types were used: corrugated 15/0.3 and 22/0.3 mm, straight 13/0.3 and 13/0.2 mm, and hooked-end 30/0.5 mm. The fiber volume content ranged from 0 to 3%. During the experimental studies, compressive strength, flexural strength, as well as the flexural fracture energy were determined. It has been discovered that an increase in the volumetric content of steel fiber results in an enhancement of all the properties under consideration, irrespective of the type of fiber. The fiber has the biggest effect on the bending fracture energy and the least on the compressive strength. Linear relationships between the mechanical characteristics of UHPFRC and the fiber factor were established, which reflects the volumetric content, length, and diameter of an individual fiber. The slope angle of the approximating lines of the “compressive strength-fiber factor” and “flexural strength-fiber factor” relationships takes on different values depending on the type of fiber used. The highest slope angle is found for corrugated fiber. It was discovered that there is a threshold value of the fiber factor, upon reaching which the steel fiber leads to an increase in the flexural strength of the UHPFRC. According to a generalized quality criterion it has been determined that corrugated fiber with dimensions of 22/0.3 mm is the optimal substitute for straight fiber 13/0.2 mm, which is widely utilized for the production of Ultra-High Performance Fiber-Reinforced Concrete

Experimental Behavior of SIFCON Corbels

This study explores the performance of six Slurry Infiltrated Fiber Concrete (SIFCON) corbels with a constant steel fiber volume of 6%, under varying vertical loads. By altering the shear span-to-depth ratio (a/d) from 0.4 to 0.6 and utilizing different fiber types (hooked end and micro) and reinforcement configurations (2Ø12mm and 3Ø12mm), the research examines the impact on maximum and cracking load capacities of the corbels. Results indicate that the a/d ratio, along with fiber type and reinforcement choice, significantly influences the structural behavior, offering insights for enhancing SFRC corbels' design and efficiency in construction applications. Highlights: Shear Span Impact: Changing the shear span-to-depth ratio critically affects load capacity. Material Influence: Fiber types and reinforcement configurations alter load behavior. Design Implications: Results highlight the importance of design choices in enhancing SIFCON corbels' structural performance. Keywords: SIFCON, Corbels, Shear Span, Steel Fiber, Load Capacity

Multiscale damage and low-velocity impact study of three-dimensional woven composites

Three-dimensional woven composites address the limitation of weak interlaminar strength found in traditional laminated composites and offer superior resistance to out-of-plane impact. However, the complex material composition and structural intricacies necessitate investigation into their damage mechanisms. This study introduces novel and reliable microscale and mesoscale Representative Volume Element (RVE) models for three-dimensional woven composites, developed through advanced CT scanning and comprehensive multi-directional tensile and shear experiments. The research explores the impact of fiber volume fraction on yarn mechanical properties using the microscale RVE model, yielding precise macroscale homogenization parameters through the mesoscale RVE model. Furthermore, a macro-meso model tailored for low-velocity impact scenarios is established, significantly enhancing computational efficiency without compromising accuracy, thus providing support for further research on the impact properties of three-dimensional woven composites.

Viscosity‐coupled curing simulation model for L‐shaped composites considering flow and compaction

AbstractComputational methods provide effective tools for the prediction of the curing behavior of composites, especially for large‐scale complex composite structures. The flow‐compaction analysis during curing receives insufficient attention in current studies. In this work, an integrated framework considering the heat transfer, the cross‐linking reaction, the flow and compaction, and the stress–strain module is established. A comprehensive resin flow termination criterion is proposed. L‐shaped composites with a stacking layer of [45/90/−45/0]s were fabricated, and the good agreement between the experimentally measured and the numerically predicted contour data validated the current model. Compared with Hubert's model, the prediction accuracy of the thickness and fiber volume content increases by 4.24% and 3.92%, respectively. Correlation analysis between the fiber volume ratio predicted by numerical methods and experimental results (94% for this method, −41% for Hubert's model) demonstrates the well‐capture of nonuniform fiber distribution in curved composites for the current strategy. The overall framework provides an accurate and promising tool for the prediction of the curing behavior of complex composite components.Highlights An integrated numerical methodology is proposed considering the resin flow and compaction. The viscosity‐temperature coupled feature of resin is considered in the permeability coefficients. A comprehensive resin flow termination criterion is proposed for an accurate prediction. The resin content, thickness, and spring‐in angle of L‐shaped laminates are characterized. The good correlation between the experimental and numerical results validates this method. Compared with the model proposed by Hubert, the prediction accuracy improves.

Vine copulas for accelerated prediction of composite strength variability

Composite materials are essential for many advanced engineering applications, but numerical quantification of strength variability can be computationally expensive. This paper proposes a novel methodology that drastically reduces the number of finite element simulations required to characterise composite material strength variability using the concept of vine copulas. This concept provides a flexible tool for the representation of high-dimensional dependencies. The methodology considers spatial scatter of three material variabilities: fibre volume fraction, fibre misalignment and fibre strength. First, the cross-correlation between stress, fibre volume fraction and fibre misalignment is fitted by a vine copula using results from a limited number of finite element simulations. Next, the vine copula is used to predict new conditional stress realisations when given realisations for the fibre volume fraction and fibre misalignment. This effectively replaces the finite element simulations with a vine copula that is much faster to evaluate. The methodology is verified by predicting the tensile failure load of a unidirectional composite coupon. Predictions are very similar to an exclusively finite element-based approach, while reducing the number of finite element simulations by a factor of 200.

Study on mechanical properties of E-glass mat reinforced basic magnesium sulfate cement thin-slab

To achieve sustainable development and reduce the carbon footprint in building material production, the E-glass fiber mat was impregnated with basic magnesium sulfate cement (BMSC) by lamination impregnation. This process reduces environmental pollution from cement preparation, increases fiber volume content, and enhances the mechanical properties of cementitious composite materials. The study examined axial tensile, four-point bending resistance, drop weight impact resistance and pendulum impact resistance of BMSC thin-slab reinforced with dispersed short glass fiber (SGF), short glass fiber mat (SGFM) and continuous glass fiber mat (CGFM) of varying gram weights. The results show that the mechanical properties of BMSC thin-slab reinforced with fiber mat are much higher than those of SGF reinforced thin-slab. The tensile strength of BMSC thin-slab reinforced with CGFM is higher than that of BMSC thin-slab reinforced with SGFM at the same gram weight, and the tensile strength increases as the weight of CGFM increases. Specifically, the axial tensile strength of BMSC thin-slab reinforced with 450 g of CGFM is nearly 8 times higher than that of SGF reinforced BMSC thin-slab. BMSC thin-slab reinforced with 450 g of CGFM has the maximum proportional limit load and bending strength. The impact strength and toughness indexes of BMSC thin-slab reinforced with CGFM are the highest, followed by SGFM reinforced BMSC thin-slab. The addition of 300 g CGFM significantly enhanced flexural toughness during the early stage of thin-slab cracking, while 450 g CGFM showed significant improvement in flexural toughness during the middle and late stages of cracking. When comparing thin-slabs with the same glass fiber volume ratio, those reinforced with 450 g CGFM exhibited the best impact resistance. SEM results indicated superior adhesion between 450 g CGFM and the cement matrix, as well as between adjacent CGFM layers, with fiber breakage being the main cause of specimen failure.

Experimental study on the flexural fatigue performance of slag/fly ash geopolymer concrete reinforced with modified basalt and PVA hybrid fibers

Geopolymer, owing to its inherent low-carbon emission advantages, emerges as a potential substitute to diminish reliance on high-carbon-emitting Portland cement. Nonetheless, similar to ordinary Portland cement concrete, geopolymer concrete tends to exhibit brittle fracture under cyclic bending loads. To improve its flexural fatigue performance, this paper incorporated the modified basalt (MB) fiber and PVA fiber in hybrid form into the geopolymer concrete. The flexural fatigue behavior of hybrid fibers reinforced geopolymer concrete was investigated, with a focus on the influence of varying hybrid fibers volume fractions. Digital Image Correlation technology was utilized to accurately track the evolution of crack length and the local strain field during the fatigue failure process. The results revealed that the incorporation of both MB and PVA fibers effectively delayed the initiation and propagation of cracks, leading to a more complex path of fatigue cracks. The PVA fiber demonstrated significant efficacy in inhibiting microcracks, while the MB fiber played a crucial role in controlling the expansion of macroscopic cracks. When the proportion of MB fiber was predominant in the hybrid mix, the crack development pattern mirrored that of samples containing MB fiber alone, exhibiting a greater extent of crack length. At a volume fraction of 0.9% for MB fiber and 0.2% for PVA fiber, a significant improvement in the fatigue life of the concrete was observed, resulting in a remarkable 136.23% increase compared to the control. This study has developed geopolymer concrete featuring enhanced crack resistance and superior flexural fatigue endurance under cyclic loading, promoting the application of environmentally friendly building materials in practical engineering.

Ultrasonic and micrograph-based quantification of material characteristics for in-situ AFP composite structures

Achieving the maximum potential of parts manufactured with in-situ consolidation thermoplastic Automated Fiber Placement without a final bulk consolidation is a challenging task. This is due partially to the continual development of the technology itself and partially due to material defects which are not fully removed during part manufacturing. In this paper, a methodology is presented for the evaluation of prepreg tape and laminate quality relevant to the manufacturing process. A novel approach is presented to quantify tape quality and the fiber volume content distribution, porosity, all of which are identified as significant influences on laminate quality. A new approach to ultrasonic testing is applied for quantitative porosity analysis promising advantages over conventional methods. Laminate porosity was successfully measured using the proposed pulse-echo ultrasonic attenuation method. The fiber content distribution from the tape used in testing shows characteristics interpreted as unfavorable for high quality in-situ AFP.

Hybrid glass-carbon fiber composites for solar greenhouse dryer trays: a 3D computational analysis

A 3D computational study was conducted to analyze the compressive load response of a glass-carbon hybrid composite. The study varied the volume percentage of glass fibers from 0% to 100% in a composite with an overall fiber volume fraction of 0.5. Compressive instability failure was examined using ABAQUS/CAE 3D finite element micro mechanical models. The analysis assessed the behavior of glass and carbon fiber models independently before evaluating the performance of the hybrid composite.The results revealed that hybrid models exhibited superior performance at specific volume fractions. It was observed that the matrix shear yield strength played a significant role in determining compressive instability failure. Furthermore, the study demonstrated that hybrid composite turnable trays enhanced moisture removal and heat transmission during drying processes. These trays were found to be particularly suitable for outdoor solar greenhouses owing to their high strength-to-weight ratio, mechanical properties, corrosion resistance, and dimensional stability.

New analytical models to predict the mechanical performance of steel fiber‐reinforced alkali‐activated concrete

AbstractThe use of alkali‐activated concrete (AAC) as an alternative construction material to Portland cement‐based concrete (PCC) has been widely encouraged by its enhanced mechanical and durability performance and environmental benefits. However, AAC exhibits low flexural and tensile strength, limiting its application in areas where high post‐cracking flexural and tensile load‐bearing capacity are needed. Steel fibers can be added to improve the composite ductility and toughness. Steel fiber‐reinforced alkali‐activated concrete (SFRAAC) is a new emerging technology with research studies evaluating the effect of fiber addition on its mechanical properties still in the early stages. To promote the application of SFRAAC, analytical models predicting their mechanical performance are needed. This study evaluates the applicability to SFRAAC of previously published analytical models developed for steel fiber‐reinforced cement‐based concrete (SFRPCC). Experimental data available in the literature have been collected to create an extensive database to validate and then calibrate these currently available correlations between mechanical properties for SFRAAC. The prediction models considered in this study correlate the mechanical performance of SFRAAC, that is, compressive strength, modulus of elasticity, splitting tensile strength, flexural and residual flexural strength, to the compressive strength of the reference concrete without fibers, the fiber volume fraction and the fiber reinforcing index. Thus, by knowing the performance of the AAC matrix and the fiber properties and dosage, it is possible to predict the overall mechanical behavior of the steel fiber‐reinforced composite.

Microstructure and mechanical properties of SiC fiber/Si-CoSi2 matrix composites fabricated by carbon chemical vapor infiltration and Si alloy melt infiltration process

For this study, orthogonal three dimensional (3D) woven silicon carbide (SiC) fiber (Hi-Nicalon, Hi-Nicalon Type S) -reinforced Si-CoSi2 matrix composites (SiC fiber/Si-CoSi2 composites) were fabricated and the microstructures and mechanical properties were characterized. The SiC fibers (28% fiber volume fraction) woven into orthogonal 3D fabrics and used as reinforcement were coated with chemical vapor infiltration (CVI)-carbon to control the fiber–matrix interface. The composite material infiltrated with Si-CoSi2 was produced using a melt-infiltration process. Four-point bending tests conducted at room temperature showed bending strength exceeding 300 MPa and tensile fracture strain exceeding 0.7%. Furthermore, bending strength greater than 400 MPa was found from a high-temperature four-point bending test under an Ar atmosphere. The failure mode was quasi-ductile. Fiber pull-out and fiber cross-linking were observed clearly. Melt infiltration of the Si-Co alloy caused little damage to the SiC fibers, confirming CVI-C layer protection of the fibers during melt infiltration and confirming that the layer can control mechanical properties at the fiber–matrix interface.

Laminated Steel Fiber-Reinforced Concrete Hingeless Arch: Research on Damage Evolution Laws

In the context of reinforced concrete (RC) arch bridges, while the incorporation of full sections of steel fibers can enhance the bridge’s toughness, cracking resilience, and bearing capacity, achieving an optimal balance between structural performance and economic viability in this manner remains challenging. This article introduces a novel computational approach—the distributed steel fiber concrete (LSFRC) arch—which considers the spatial distribution of damage in RC arches. The static performance of SFRC elements and LSFRC beams was compared and analyzed using the concrete plastic damage model (CDP) in ABAQUS software. This study validated the rationality of the model and investigated the impact of varying steel fiber volume ratios and steel fiber layer heights on the damage evolution of LSFRC arches. The results of this study demonstrate that the cracking load and bearing capacity of an RC arch can be effectively enhanced through the addition of steel fibers to a local area under static loading. Furthermore, the deflection and damage to the arch waist and arch roof can be significantly reduced. Furthermore, the incorporation of steel fibers at an increased volume rate and at a greater height within the doped section can effectively slow the rate of damage evolution within the section. This results in the inhibition of crack extensions and in an improvement in the ductility and reliability of the damage stage. The LSFRC arches offer superior economic and practical advantages over their full cross-section doped steel fiber (FRC) counterparts. This study offers novel insights and methodological guidance for the design and implementation of concrete arch bridges.

Study on mechanical properties and molecular simulation of nano‐SiO2‐modified hybrid fiber reinforced polymer bar under the dry and alkaline environment

AbstractFiber reinforced polymer (FRP) bars have received extensive promotion and application in the structural engineering. However, due to the limitations inherent in using single material, FRP reinforced concrete structures often encounter issues, such as brittle failure and inadequate energy dissipation, particularly in complex natural environments and under various loading conditions. In this study, the preparation of nano‐SiO2‐modified carbon/basalt hybrid FRP bars was carried out using the pultrusion‐winding process and ultrasonic treatment. The objective was to investigate the influence of the fiber volume ratio and mass fraction of nano‐SiO2 on the mechanical properties of FRP bars under drying and alkaline conditions. Molecular dynamics simulations were performed to construct interface models between fibers and epoxy resin in order to elucidate the toughening mechanism of nano‐SiO2 and the degradation mechanism in alkaline conditions. The research results show that elevating the substitution rate of carbon fibers and incorporating nano‐SiO2 doping bring about alterations in the brittle fracture characteristics of BFRP bars and enhance the post‐yield performance and interlaminar shear properties of hybrid FRP bars, concurrently mitigating the degradation of mechanical properties induced by exposure to alkaline solutions. MD simulations indicate that the addition of nano‐SiO2 improves the binding rate of hydrogen bonds between BF and epoxy resin, resulting in a higher interfacial energy between BF/epoxy resin compared to CF/epoxy resin. Moreover, nano‐SiO2 effectively mitigates the impact of alkaline solutions on the formation of interfacial hydrogen bonds. The findings of this study serve as a valuable reference for the design and application of FRP reinforced concrete structures.Highlights Nano‐SiO2 modified B/CFRP bars made via extrusion‐winding & ultrasonic treatment. Improved mechanical properties and plastic deformation in Nano‐SiO2 modified B/C FRP bars. Nano‐SiO2 inhibits B/CFRP bars degradation in alkaline solution. Nano‐SiO2 bind more at BF/epoxy than CF/epoxy interface. Nano‐SiO2 reduces alkaline solution effect on interfacial H‐bonding.

Additive Manufacturing of Continuous Fiber-Reinforced Polymer Composites via Fused Deposition Modelling: A Comprehensive Review.

Additive manufacturing (AM) has arisen as a transformative technology for manufacturing complex geometries with enhanced mechanical properties, particularly in the realm of continuous fiber-reinforced polymer composites (CFRPCs). Among various AM techniques, fused deposition modeling (FDM) stands out as a promising method for the fabrication of CFRPCs due to its versatility, ease of use, flexibility, and cost-effectiveness. Several research papers on the AM of CFRPs via FDM were summarized and therefore this review paper provides a critical examination of the process-printing parameters influencing the AM process, with a focus on their impact on mechanical properties. This review covers details of factors such as fiber orientation, layer thickness, nozzle diameter, fiber volume fraction, printing temperature, and infill design, extracted from the existing literature. Through a visual representation of the process parameters (printing and material) and properties (mechanical, physical, and thermal), this paper aims to separate out the optimal processing parameters that have been inferred from various research studies. Furthermore, this analysis critically evaluates the current state-of-the-art research, highlighting advancements, applications, filament production methods, challenges, and opportunities for further development in this field. In comparison to short fibers, continuous fiber filaments can render better strength; however, delamination issues persist. Various parameters affect the printing process differently, resulting in several limitations that need to be addressed. Signifying the relationship between printing parameters and mechanical properties is vital for optimizing CFRPC fabrication via FDM, enabling the realization of lightweight, high-strength components for various industrial applications.