Fiber Volume Research Articles

Experimental and Numerical Investigations on the Seismic Performance of High-Strength Exterior Beam-Column Joints with Steel Fibers.

Steel fiber reinforced high-strength concrete (SFRHSC) is a composite material composed of cement, coarse aggregate, and randomly distributed short steel fibers. The excellent tensile strength of steel fiber can significantly improve the crack resistance and ductility of high-strength concrete (HSC). In this study, experimental and numerical investigations were performed to study the cyclic behavior of the HSC beam-column joint. Three SFRHSC and one HSC beam-column joint were prepared and tested under cyclic load. Two different volume ratios of steel fibers and three stirrups ratios in the joint core area were experimentally studied. After verification of the experimental results, numerical simulations were further carried out to investigate the influence of steel fibers volume ratio and stirrups ratio in the joint core area on the seismic performance. Evaluation of the hysteretic response, ductility, energy dissipation, stiffness, and strength degradation were the main aims of this study. Results indicate that the optimal volume fraction of steel fibers is 1.5%, and the optimal stirrups ratio in the joint core area is 0.9% in terms of the enhancement of the seismic performance of the SFRHSC beam-column joint.

Study of the effect of void defects on the mechanical properties of fiber reinforced composites

This study is to investigate the mechanical properties of fiber-reinforced polymer (FRP) composites considering void defects by adopting a representative volume element model. The results reveal that initial damage always sprouts at the interface, the void defects affect the location of the initial damage and are the dominant factor in determining the stress required for damage sprouting. In addition, the void defects as well as the neighboring debonding interfaces together determine the direction of the main damage evolution zone. The transverse tensile properties are most affected by the void defects, while the longitudinal tensile properties are least affected. In particular, the strength is more sensitive to void defects than that of elastic constants. In addition, the mechanical properties of high Fiber Volume Fraction (FVF) FRP composites are significantly stronger affected by void defects than those of low FVF FRP composites.

Effect of High-Tenacity Polypropylene Fibers on the Carbonation Resistance of Expanded Polystyrene Concrete

Expanded polystyrene concrete (EPSC) is increasingly utilized in buildings as a green building material. To investigate the effect of high-tenacity polypropylene (HTPP) fibers on the carbonation resistance (CR) of EPSC, five groups of EPSC specimens with HTPP fiber volume fractions of 0%, 0.6%, 0.9%, 1.2%, and 1.5% were prepared. Rapid carbonation tests were conducted to measure the carbonation depth (CD) and uniaxial compression strength (UCS) of the specimens at different carbonation ages (3, 7, 14, and 28 days). The CD and UCS of the specimens were calculated and analyzed. The results indicated that the HTPP fibers dramatically improved the CR of EPSC, with a decrease in the CD of up to 29.5% at 28 days. A model for predicting the CD of EPSC was developed. The model for the strength after carbonation also showed good agreement with the experimental results. Scanning electron microscopy (SEM) was used to examine the microstructure of the HTPP-reinforced EPSC, while the mechanism of HTPP fibers to enhance the CR of EPSC was elucidated. The findings of this study provide valuable insights for the application of EPSC as a structural material.

A Review on the Performance of Fibers on Restrained Plastic Shrinkage Cracks

Multiple studies have investigated the use of steel, synthetic fibers, and natural fibers to reduce plastic shrinkage cracks in concrete, which are mostly caused by water evaporation from the surface of the material. This review used original published research articles from the Web of Science and Scopus database to evaluate the performance and relationship between the fiber volume, aspect ratio, compressive strength, and plastic shrinkage cracking. This review also discussed the most widely used technique for evaluating plastic shrinkage cracking, the ASTM C 1579, with two bottom restraints and a central stress riser to induce cracking, and its modified version with additional reinforcement for further restraining the ASTM C 1579 mold. Longer fibers function better than shorter fibers because of their larger surface area, which allows them to bridge fissures. It was also observed that crack initiation time is delayed when fibers are added to concrete. In addition, as the volume proportion of the fibers increased, the plastic shrinkage cracks decreased, but the compressive strength declined. Furthermore, the volume fraction of the fibers had a greater effect on reducing cracking than the aspect ratio. It was also concluded that a fiber volume inclusion below 1% is best.

Functionally graded fibre concrete constitutive model considering fibre spacing effects and interfacial interactions

The purpose of this paper is to establish a new constitutive model for functionally graded concrete (FGC) with high fiber content, considering randomly distributed cylindrical fibers and spherical, ellipsoidal, and cubic aggregates. Considering the fiber spacing coefficient and adjusting for the reinforcing effect of the fibers, the new correction factors include the fiber orientation coefficient, the fiber inclination impact coefficient, and the fiber spacing coefficient. Moreover, the interaction between the upper and lower interfaces of the FGC and the interaction between the fibers and the matrix are also considered. The interface adopts a cohesive bond-slip model to define interface plastic damage. The interaction between the fibers and the matrix is based on the rigid body-spring concept, where the matrix block is first discretized into rigid body-spring elements, which then interact with the fibers to produce bond-slip forces. During model validation, the proposed constitutive model was introduced into Abaqus using Python code. Finite element models for FGC, including the conventional uniaxial tensile model, dog-bone model, and four-point bending model, were established. The results indicate that for the FGC numerical computation model, the critical fiber volume fraction ρs ranges between 6 % and 7 %. However, the exact value should be determined based on specific practical conditions. When ρs is within the range of 0 %–6 %, the mechanical properties of FGC, such as peak stress, tensile strength, and toughness, increase with the increase in ρs. However, when ρs exceeds 6 %–7 %, the growth trend begins to slow down. In some cases, peak stress and tensile strength may decrease with an increase in ρs. At this point, the influence of the fiber spacing coefficient must be considered. Finally, by comparing with the experimental results, it is proved that the proposed constitutive model is feasible for studying the mechanical properties of FGC.

Experimental Study on the Mechanical Properties of Steel Fiber Ferronickel Slag Powder Concrete

The use of ferronickel slag powder (FNSP) as a cementitious additional material has been supported by numerous reports. FNSP concrete has the same shortcomings as ordinary concrete, including low hardness. In this study, in order to make FNSP concrete more durable, end-hooked type steel fibers were incorporated. To understand how various elements affect the mechanical properties of steel fibers, an experiment was carried out on the mechanical properties of steel FNSP concrete (SFNSPC). FNSP’s principal ingredients, with a particle size distribution ranging from 0.5 to 100 μm and a sheet-like powder shape, are CaO, SiO2, Al2O3, MgO, and others, according to tests conducted on the material’s microstructure and composition. Then, eighteen mix proportions were developed, comprising six distinct FNSP replacement rate types and three distinct steel fiber content types. Crucial metrics were evaluated and analyzed, including the relationship among the toughness, tensile strength, and compressive strength as well as slump, splitting tensile strength, compressive strength, and uniaxial compressive stress–strain curve of SFNSPC. The results showed that the slump of SFNSPC under different FNSP replacement rates decreased with increasing steel fiber volume. Steel fibers have a small but positive effect on SFNSPC’s compressive strength; nonetheless, as FNSP replacement rates increased, SFNSPC’s slump gradually decreased, though not by much. These results show that FNSP is a viable alternative cementitious material in terms of strength. Specifically, the splitting tensile strength of SFNSPC improves with an increase in steel fiber content, and the pace at which SFNSPC strength drops with an increase in the FNSP replacement rate. With varying mix proportions, the stress–strain curve trend of SFNSPC remains mostly constant, and steel fibers improve the compressive toughness of SFNSPC. After adding 0.5% and 1.0% steel fibers, the toughness index of concrete with different FNSP replacement rates increased by 8–30% and 12–43%, respectively.

Investigation of two collinear cracks in fiber reinforced composites under thermal loading

The objective of this paper is to explore the transient behaviors of fiber reinforced composites with two embedded collinear cracks subject to a sudden thermal shock. The orthotropic composites with both the vertically oriented and horizontally aligned fibers are examined to present a systematic comparison. By means of the integral transform methodology and singular integral equations, the thermal and elastic governing equations are solved numerically to determine the transient thermal process and stress intensifications around the crack tips. Parametric investigations are carried out for fiber volume fractions and crack distances. The findings would be beneficial to a more thorough knowledge of fibrous composites’ fracture characteristics under thermal shocks, which helps material design and structural optimization of the composites with fiber reinforcements.

Assessing compressive mechanical behavior of woven fabric green textile composite using finite element method

AbstractThe research aims to forecast the mechanical performance of a hybrid woven fabric natural composite subjected to compression, utilizing the three‐dimensional finite element method. A detailed finite element model of a plain woven fabric unit cell is created and analyzed for different materials like flax, basalt, and jute, and combinations of these materials (inter‐yarn hybrid basalt‐flax, jute‐flax and basalt‐jute fabrics). It is observed that fabric‘s response to compression is mainly influenced by the transverse longitudinal shear behaviour and the stiffness of the yarn cross‐section. Compression of single‐layer woven fabric involves yarn bending and compaction, resulting in varying fiber volume fractions in different areas due to compaction. The basalt‐jute hybrid plain woven fabric outperformed other plant‐based fiber fabrics with a polypropylene matrix in terms of mechanical performance under compression. Increase in yarn spacing and fabric thickness resulted in higher strain energy and displacement, attributed to changes in fiber volume fraction and crimp angle. Whereas, increasing yarn width led to a stiffer fabric due to increased contact area at the crossover region and higher bending rigidity, resulting in decreased strain energy and displacement. Importantly, this developed model can effectively simulate textile fabrics with diverse weaving patterns, material properties, and loading conditions.

Behaviour of steel-fibre-reinforced geopolymer concrete-filled square steel tubular stub column under axial compression

Resource utilisation of industrial waste has become a crucial issue in construction aiming for sustainable development. Research on geopolymer concrete-filled square steel tubular (GCFST) structures is limited. Moreover, methods for calculating the bearing capacity of steel-fibre-reinforced GCFST (SFRGCFST) structures require further investigation. This study presents an experimental and analytical investigation of the axial compression performance of SFRGCFST stub columns. Twenty-four specimens were tested to assess the effect of steel tube thickness, steel fibre (SF) volume fraction, SF aspect ratio, and concrete strength grade on failure modes, load–deformation behaviour, load–strain response, ultimate resistance, and ductility of SFRGCFST columns. The results indicated that the failure modes of SFRGCFST columns are influenced by the coefficient index, which varies with the test parameters. When the coefficient index exceeded 0.88, the failure mode of the specimens transitioned from shearing failure to waist-drum-shaped failure. The average ultimate bearing capacity of the SFRGCFST columns increased by 35.13 % compared with that of the plain concrete-filled steel tubes (CFSTs). When the SF volume fraction reached 0.9 %, the ultimate bearing capacity of the SFRGCFST columns increased by 21.85 % compared with that of steel-fibre-reinforced concrete-filled steel tube (SFRCFST) columns. The incorporation of SF significantly improved the deformation capacity and ductility of the SFRGCFST columns and moderated the slope of the post-peak load–displacement and load–strain curves, slowing the descent of the curve. Utilising the multi-axial strength criterion and mechanical equilibrium equation for square CFSTs, a formula for calculating the ultimate bearing capacity of SFRGCFST stub columns was developed. This formula enables accurate prediction of the axial compressive load capacity of SFRGCFST stub columns and provides a basis for revising relevant standards.

Mechanical performance study of PVA fiber-reinforced seawater and sea sand cement-based composite materials

Due to the swift progress in the construction sector, there is a global concern about the potential scarcity of river sand and freshwater resources. The development of new construction materials is considered an inevitable trend for industry growth. PVA fibers, known for their strong corrosion resistance, cost-effectiveness, and high toughness, have the potential to enhance the corrosion resistance and seismic performance of structures in marine environments. However, their mechanical properties and durability in the seawater and sea sand environment are not well understood. Therefore, the investigation of the impact of seawater and sea sand on the mechanical properties and durability of PVA fiber-reinforced cement composites is considered crucial. A mechanical performance analysis of PVA fiber-reinforced seawater and sea sand fiber cement composites was conducted in this study. PVA fiber volume fractions of 0%, 0.75%, and 1.5%, cement composite matrix strength grades of C30 and C50, and curing periods of 28 days, 90 days, and 180 days were examined, investigating their influence on the bending toughness of PVA fiber-reinforced seawater and sea sand cement composites. Specific conclusions include the addition of fibers increased the peak bending load, had a less corrosive effect in seawater, and improved the flexural toughness of the material. The most significant improvement was observed at 1.5% fiber content, where the load-deflection curve was fuller and the energy absorption capacity of the material increased by 33–109%, maintaining good bending toughness. Furthermore, higher fiber contents are required for high-strength cementitious composites to improve flexural toughness and durability. The formulation of calculation formulas for predicting bending strength and corresponding deflection, which fit well with the experimental results; and the development of a calculation model for the bending toughness index of PVA fiber-reinforced seawater and sea sand cement composites, providing an effective prediction of material bending toughness.

Enhancing non-metallic gasket performance with shape memory fibers

This study aims to enhance the sealing performance of non-metallic gaskets by incorporating shape memory fibers. The analytical exploration focuses on analyzing the thermomechanical behavior of Nitinol fibers in their woven state within the gasket. Specifically, the investigation examines the variation of phase transformation zones across the wire cross-section with changes in temperature. Subsequently, a series of SMA fiber-reinforced gasket samples were fabricated, and experimental investigations were conducted to assess the impact of Nitinol fibers on composite gaskets using a helium gas leak test. The results demonstrate that the integration of shape memory alloy wires into the composition of gaskets can significantly improve their sealing performance. Moreover, this study examines a number of pivotal factors such as fiber volume fraction, temperature application, woven fiber arrangement, leakage rates, gasket deformation, contact stress, and structural bending. These comprehensive investigations may provide valuable insights into the efficacy of Nitinol fibers in enhancing gasket sealing performance.

THE EFFECT OF POLYPROPYLENE FIBERS ON COMPRESSIVE AND SPLIT TENSILE STRENGTH OF LIGHTWEIGHT CONCRETE

This study was carried out to design lightweight concrete, which is enriched with polypropylene fibers using coarse pumice and sand fine aggregates. Lightweight concrete specimens were classified into distinct groups based on fibers content employed, namely a control group with 0 kg/m³ and the experimental incorporating 0.1 kg/m³, 0.3 kg/m³, 0.5 kg/m³, and 0.7 kg/m³ varying quantities of polypropylene fibers. Subsequently, after a curing period of 28 days, the hardened concrete test was conducted on cylinder specimens measuring 150 mm x 300 mm. The consistency of the fresh concrete mixture was tested using the Abrams cone test, which revealed a decrease in the workability of fibers-reinforced concrete with an increase in fibers volume in the mixture. The test aimed to determine the effect of polypropylene fibers on compressive and tensile strength of lightweight concrete. The optimal compressive and split tensile strength was observed at fibers volume fraction of 0.5, to obtain 7.84 MPa, or 56.68% increase in compressive strength, and 2.12 MPa or 42.86% rise in tensile strength. Based on compressive and split tensile strength obtained from this study, concrete was classified as highly lightweight structural concrete, which served as an insulator.

Non-linear finite element analysis of SFRC beam-column joints under cyclic loading: enhancing ductility and structural integrity

Brittle shear failure of beam-column joints, especially during seismic events poses a significant threat to structural integrity. This study investigates the potential of steel fiber reinforced concrete (SFRC) in the joint core to enhance ductility and overcome construction challenges associated with traditional reinforcement. A non-linear finite element analysis (NLFEA) using ABAQUS software was conducted to simulate the behavior of SFRC beam-column joints subjected to cyclic loading. Ten simulated specimens were analyzed to discern the impact of varying steel fiber volume fraction and aspect ratio on joint performance. Key findings reveal that a 2% volume fraction of steel fibers in the joint core significantly improves post-cracking behavior by promoting ductile shear failure, thereby increasing joint toughness. While aspect ratio variations showed minimal impact on load capacity, long and thin steel fibers effectively bridge cracks, delaying their propagation. Furthermore, increasing steel fiber content resulted in higher peak-to-peak stiffness. This research suggests that strategically incorporating SFRC in the joint core can promote ductile shear failure, enhance joint toughness, and reduce construction complexities by eliminating the need for congested hoops. Overall, the developed NLFEA model proves to be a valuable tool for investigating design parameters in SFRC beam-column joints under cyclic loading.

Compaction behaviour of flax-preforms during forming for composites

Flax reinforced composites are becoming popular in automotive and civil industries due to their green production and recycling, and for good specific strength. To manufacture composites, firstly a multi-layer of flax preforms undergo compressive pressure before resin impregnation that causes nesting, wherein, fibres of one layer fit into the adjacent layers. This debulking of the preforms under compression is an important feature that determines the fibre volume fraction of composites. In this study, four flax structures such as: nonwoven tapes, unidirectional fabric, hopsack fabric, and nonwoven tape with glass veils were investigated for compaction behaviour under pressures between 1 and 10 bars, in single and multi-layer states, in dry and wet states, under different loading cycles, and in different ply orientations (0°/0° and 0°/90°). Nesting has been calculated for single- and multi-layer stacks. It was observed that the nonwoven structures shown greater thickness reduction compared to woven structures. Nesting factor was found to be higher than 1 for the nonwoven structures under compaction, indicating lower nesting, compared to the woven structures. In terms of thickness under repeated compaction, the reduction was the highest during first compressions, compared to the 2nd and 3rd compressions, for all the structures. When wettability was examined, thickness reduction for wet plies was higher for all the structures, compared to the dry phase. Finally, a comparative study was shown to evaluate fibre volume fractions of the composites.

Utilisation of Coir Fiber as Reinforcement in M20 Concrete Mix

Sustainability is a wide accepted concept in modern construction scenario. Even though the construction industry is revolutionizing in a significant manner in terms of both equipment and materials used, the cost of construction has skyrocketed along with the deteriorative impact on environment. This resulted in the adoption of a more balanced approach with the environment as its nerve centre to create a better world to live in. This has led to the adoption of a natural fiber like Coconut for the strength enhancement in concrete. Concrete needs to be reinforced in order to improve its engineering qualities. Coconut fibers were employed for this study since they are widely accessible and come in big numbers. The study includes a comparison of the qualities of regular concrete and concrete reinforced with coconut fiber based on laboratory experimentation. Concrete with different fiber contents was evaluated with conventional concrete or prestressed concrete and different strengths parameters such as bending, compression and tensile strength of coconut fiber of length 25, 50, and 75 mm were added with proportions (0.5%, 1%, 1.5% and 2%) of total weight of the volume of concrete coconut fibre is carried out. The various strength aspects analysed are the flexural, compressive and tensile strength of the coconut fibre reinforced concrete.

Multiscale verification method for prediction results of mechanical behaviors in unidirectional fiber reinforced composites

At present, there is almost no reliable multiscale experiment method that can be used to verify the multiscale mechanical behaviors of unidirectional (UD) fiber reinforced composites (FRC). Therefore, a multiscale method was developed for verifying the prediction results of the macro-mechanical properties and micro-damage modes in UD FRC. Firstly, the fiber volume fractions were determined using the fiber content test for three different FRC. Secondly, the random fiber distributed representative volume elements (RFDRVEs) were generated corresponding to these fiber volume fractions. Moreover, the RFDRVEs were used to predict the macro-mechanical properties and micro-damage modes of UD FRC. Ultimately, the standard mechanical tests and scanning electron microscopy (SEM) were applied to verify the accuracy of the prediction for the macro-mechanical properties and micro-damage modes of UD FRC. The results show that the proposed multiscale method is feasible for the verification of the multiscale prediction results based on RFDRVEs.

Experimental Investigation of the Behavior of SlFCON Column under Eccentric Monotonic Load

Abstract This research delves into the performance of Slurry Infiltrated Fibrous Concrete (SIFCON) columns when subjected to eccentric monotonic loading, through the examination of twenty columns until their point of failure. The research addresses gaps in existing literature by examining the effects of various parameters, including fiber type, volume fraction, and eccentricity ratio, on SIFCON column performance. Results reveal significant correlations between the studied parameters and the structural behavior of SIFCON columns. The investigation shows how the ultimate load affect by the eccentricity ratio, for instance, the hook end steel fiber with a volume fraction of 6%, where the ultimate load decreased by a factor of 0.25 when the eccentricity ratio changed from 0.1 to 0.5. Furthermore, increasing the volume fraction of steel fibers significantly enhances the energy absorption of SIFCON columns. For instance, with the hook-end steel fiber and an eccentricity ratio of 0.3, the energy absorption increased by a factor of 2.76 when the volume fraction of steel fiber changed from 4% to 9%. The type of fibers used plays a pivotal role in the material behavior of SIFCON, with the straight micro fiber exhibiting an ultimate load 2.17 times greater than flat crimped steel fiber types when the volume fraction was 9% and the eccentricity ratio was 0.3. Finally, based on the experimental results, an interaction diagram has been established for three types of SIFCON: straight micro steel fiber with a volume fraction of 12%, hook end steel fiber with volume fractions of 6% and 4%.

Computational modeling and statistical analysis of buckling characteristics of polysilicon reinforced fiber

The purpose of this study is to evaluate the effect of volume fraction of continuous carbon fiber and sample length on buckling characteristics of polysilicon. A statistical design of 12 samples were formulated with constant cross-section area of 2500 mm2 using Design of Experiment software (DOE). The samples were sketched using ABAQUS 2019 software, and the total buckling force each sample was estimated. The estimated buckling forces were statically evaluated as a response using DOE. The estimated forces of 3.48776e07, 4.00652e07 and 5.78142e07 newton for the simulated samples of 100 mm in length and 0,15, and 25% volume fraction respectively, is an indication of positive effect of fiber volume fraction on the necessary force for buckling. In addition, similar tendency was found in other samples (the higher fiber volume fractions the higher buckling force). However, the estimated buckling force for each sample was negatively affected with length of the sample. The result indicated a value of 4.00652E+07, 5.00447E+06 and 1.80390E+06 newton at a constant fiber volume fraction and different length of 100, 300 and 500 mm respectively. The statistical analysis of the simulated buckling force showed a signification design, and the date of one factor effect is highly supported by the simulated buckling forces. The equation of a significant design can be used to estimate the buckling force at any fiber volume fraction and sample length.

Microstructure, interfacial and mechanical properties of SiC interphase modified C/C-SiC composites prepared by reactive melt infiltration

Interfacial modification can effectively regulate the interfacial properties of ceramic matrix composites. This paper reports on the effect of SiC interphase thickness on the microstructure, interfacial and mechanical properties of C/C-SiC composites. As the SiC interphase thickness increased to 2 μm, the flexural strength and modulus of the C/C-SiC composites increased up to 252 MPa and 40 GPa, an increase of 36 % and 40 %, respectively. Because the SiC interphase protected the carbon fibers from the corrosion of liquid silicon, thereby increasing the effective fiber volume fraction. Furthermore, the increased interfacial shear strength (IFSS) measured by the fiber push-in test improved the load transfer efficiency. Raman spectrum and transmission electron microscopy indicated that the damage process of the interface with high IFSS after the fiber push-in test showed fiber/pyrolytic carbon interface debonding, release of thermal residual stress, and larger upward rebound protrusion of carbon fibers without interface crushing.

Ultracompact 3D Splitter for Single‐Core to Multi‐Core Optical Fiber Connections Fabricated Through Direct Laser Writing in Polymer

AbstractThe deployment and advancement of high‐bandwidth communication networks, quantum information systems, and sensing platforms relying on multi‐core optical fibers (MCFs) are challenged by the scarcity of cost‐effective, compact, and efficient optical interfacing components. This study introduces an unprecedented 3D‐printed 1 × 4 splitter for MCFs fabricated with 2‐photon polymerization‐based direct laser writing. The pivotal element is a triangular cross‐section 3D multimode interference (MMI) coupler, supplemented with S‐bends and adiabatic tapers to facilitate the splitting of a signal from a single core of a single‐mode fiber into four cores of a multi‐core fiber. All components are initially designed and assessed to minimize loss and polarization dependence across the C‐ and L‐bands using optical simulation. Subsequently, a proof‐of‐concept model of the splitter, compactly integrated within the fiber volume, featuring a remarkably short length of 180 µm and insertion loss of ≈−3 dB, is fabricated. The manufacturing speed, minimal loss, component compactness, and flexibility of the approach, collectively present promising avenues for pioneering developments in MCF‐coupling components.