Fiber Volume Ratio Research Articles

A comparative study of low cyclic loading effects on plastic strain, nonlinear damping, and strength softening in fiber-reinforced recycled aggregate concrete

The incorporation of fibers significantly enhances the properties and structural performance of recycled aggregate concrete. This study introduces Fiber-Reinforced Recycled Aggregate Concrete (FRAC) by integrating steel fibers (SF) and polypropylene fibers (PPF) into the recycled aggregate concrete (RAC) matrix. A comprehensive series of cyclic loading tests, including reload and unload sequences, were conducted to meticulously analyze the deterioration of strength and energy dissipation capabilities of SF/PPF-reinforced RAC. The research examines the effects of fiber characteristics, volume ratios, lengths, and diameters on strength degradation after the peak stress along the stress-strain curve. Degradation models based on plastic strain were proposed for both SF-reinforced RAC and PPF-reinforced RAC. The study further investigates the fluctuation of strain energy in FRAC under low cyclic loading, revealing the correlation between plastic strain energy and equivalent viscous damping ratio. A nonlinear viscous damping model that accounts for the influence of the reinforcing index (RI) is proposed. This model effectively predicts the degradation of strength, the evolution of plastic strain, and the dynamics of nonlinear viscous damping in composite materials with varying fiber content. Ultimately, this research provides essential technical insights for the practical engineering application of RAC.

MECHANICAL BEHAVIOUR OF ISTLE FIBRE COMPOSITE REINFORCED WITH EPOXY AND E-GLASS AT DIFFERENT FIBRE ORIENTATIONS

This paper was aimed to study the mechanical properties of Istle fibre composites. The process of fabrication was done by hand layup technique at three different fibre orientations i.e., unidirectional, bidirectional and 45 degrees inclined, and also its effect on tensile and flexural property that was studied in the Instron Testing Machine. The fibre volume ratio was kept uniform for the entire specimen as 50:50. The treatment of istle fibre was done with sodium hydroxide to increase the fibre matrix bonding. The effect of E-glass reinforcement has also been studied in both bending tests and flexural tests. The maximum tensile and bending modulus recorded were from unidirectional fibre specimen.

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.

Numerical Modeling of Steel Fiber Reinforced Recycled Concrete Filled Steel Tube Column Under Cyclic Loading

A finite element model (FEM) was created with the aim of analyzing the behavior of steel fiber reinforced recycled concrete (SFRRC)-filled steel tube columns under combined cyclic loading and monotonic axial load. The FEM considered the effect of steel tube confinement on the inner concrete behavior under cyclic loading. The numerical model was described in detail, with a focus on modeling the materials involved (normal concrete, SFRRC, and steel) under cyclic loading. A constitutive concrete model - with and without considering confinement - was based on utilizing a concrete damaged plasticity (CDP) model. The steel tube - concrete core interface was modeled by a surface-to-surface contact. A stress-strain constitutive concrete model, confined by circular steel tubes, was implemented, and validated using experimental results from the literature. The developed FEM considered various parameters: steel tube thickness, volume ratios of steel fibers, besides strengths of both concrete core and the steel tube. The FEM results showed great similarity to the under- cyclic- loading tested columns. The results indicated that the concrete confining pressure must be considered in CDP model. A good correlation between numerical and experimental findings was obvious, including failure modes, and hysteretic curves of load-displacement.

Research on the Performance of Steel Strand-Reinforced Reactive Powder Concrete with Mixed Steel Fibers and Basalt Fibers under the Salt Dry–Wet Erosion

In this study, the properties of steel strand-reinforced reactive powder concrete (RPC) with mixed steel fibers and basalt fibers were investigated. The volume ratios of steel fibers and basalt fibers ranged from 0% to 2%. The reinforcement ratio of steel strands was 1%. The flexural strength and toughness were measured. Moreover, the impact toughness was determined. The studies were carried out under an erosion environment with chlorides and sulfates. The electrical resistance and the ultrasonic velocity were obtained to assess the salt corrosion resistance performance of steel strand-reinforced RPC. The results show that the addition of basalt fibers and steel fibers can improve the mechanical strength, ultrasonic velocity, flexural toughness, and impact toughness and decrease the performance degradation of the steel strand-reinforced RPC under the conditions of dry–wet alternations of NaCl and Na2SO4 solutions. Basalt fibers and steel fibers can improve the steel strand-reinforced RPC’s flexural strength by rates of up to 13.1% and 28.7%, respectively. Moreover, the corresponding compressive strength increases by 10.3% and 18.3%. The flexural strength decreases by 11.2~33.6% and 7.3~22.7% after exposure to the NaCl and Na2SO4 dry–wet alternations. Meanwhile, the corresponding compressive strength decreases by 22.1~38.9% and 14.6~41.3%. The electrical resistance increases with the addition of basalt fibers and decreases with the increasing dosages of steel fibers. The steel strand-reinforced RPC with the assembly units of 1% steel fibers and 1% basalt fibers shows the optimal mechanical properties and salt resistance considering its wet–dry alternation performance. The properties of steel strand-reinforced RPC decrease more rapidly after undergoing NaCl erosion than Na2SO4 erosion.

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.

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.

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.

Experimental Study on the Bonding Performance between Shaped Steel and High-Strength Concrete

The integration of steel fibers into high-strength concrete (HSC) offers a solution to address the brittleness and limited ductility typically associated with conventional HSC structures. To investigate the bonding properties between shaped steel and high-strength concrete with steel fiber (SFRC), thirteen tests of the shaped steel/SFRC specimens are conducted to explore the effects of various factors such as steel fiber volume ratio, concrete strength grade, reinforcement ratio, steel embedment depth, and cover thickness on bond–slip behavior. Three distinct failure modes, such as pushout failure, bond splitting, and yielding failure of steel, are identified during the pushout tests. Three different types of bond strength, such as the initial bond strength, the ultimate bond strength, and the residual bond strength, are observed from the load–slip curves between the shaped steel and concrete. By incorporating nonlinear spring elements, a numerical model for accurately simulating the bond performance between the shaped steel and SFRC specimens is developed. The bond strength between the shaped steel and concrete increase as the concrete strength, cover thickness, steel fiber volume ratio, and stirrup ratio increase, while it decreases as the steel embedment depth increases. A model for the bond strength between shaped steel and SFRC is developed, and it agrees well with the test data.

Experimental and analytical study on eccentrically loaded Fiber concrete columns reinforced longitudinally with GFRP bars

In this paper, experiments were carried out to analyze the behavior of the square columns reinforced longitudinally by GFRP bars along with different ratios of hooked end fibers under eccentric compressive loading. Eight short square columns with a cross-section dimension of 150x150mm and a height of 1200 mm, were fabricated to conduct the experimental program. A 150 mm enlargement in column-cross at both ends was considered to develop an eccentric axial load. The columns were tested under different load eccentricity ratios (0.26, 0.5, 1). Different tie spacings (50, 100, 120) mm. Different ratios of steel fibers 0 %, 0.5 %, and 1 % were incorporated into the concrete mix. It was observed that columns with steel fibers demonstrated good characteristics, including higher ultimate load, increased ultimate deflection, and enhanced ductility and toughness compared to the columns without steel fibers due to multiple cracking behaviors. The ductility of the columns reinforced with GFRP bars was enhanced by 46.8 %, and 68 % for steel fiber volume ratios of 0.5 % and 1 %, respectively. The energy absorption was increased by 42 % and 77 % for steel fibers ratios of 0.5 % and 1 %, respectively. When GFRP bars were used as longitudinal reinforcement, there was an improvement in the bond behavior between the concrete and the GFRP bars. All concrete columns reinforced by GFRP bars failed due to flexure-compression failure. There was no observed rupture of GFRP bars during the experimental test and the maximum strain did not reach 40 % of their ultimate strain capacity. Nonlinear Finite Element analysis was conducted to simulate the behavior of tested columns. The equations from previous studies and the codes were established to predict the nominal peak capacity of columns considering all parameters. In general, there was a reasonable level of agreement observed between the experimental data and the theoretical results determined for seventy-column specimens in the current study and from previous studies in the literature.

Shear behavior of ultra-high performance concrete corbels：Experimental study and modified strut-and-tie model

In this study, a static loading test was performed to examine the shear behavior of twelve ultra-high performance concrete ( UHPC) corbels. The impact of key parameters, such as shear-span ratio, steel fiber volume ratio, and stirrup reinforcement ratio on corbels' mechanical behavior, were explored. The test findings reveal that the cracking load of UHPC corbels is significantly higher than that of the corbels without steel fiber, and the failure mode changes from shear failure to flexural failure. Reducing the shear-span ratio and increasing the stirrup reinforcement ratio substantially improved the shear capacity of the corbels. Furthermore, a modified strut-and-tie model was developed for predicting the shear capacity of UHPC corbels. A shear test database for UHPC corbels was compiled to validate the accuracy of the proposed method. The model showed strong agreement with the test results and demonstrated satisfactory adaptability. Finally, four other models from national standards and academic proposals were evaluated under the same conditions. The proposed model showed superior correlation with the experimental data, suggesting its potential to improve the design and application of UHPC corbels in practical engineering contexts.

Study on seismic performance of steel fiber reinforced concrete shear walls with hybrid steel strands and HRB400 bars in the boundary elements

The paper proposed a type of reinforced concrete (RC) shear walls both replacing steel bars in boundary elements with steel strands and adding steel fibers. Four specimens, including one RC specimen, one steel strands RC (SRC) specimen, and two SSFRC specimens referred to SRC specimens using SFRC, were designed and tested to investigate the influences of steel strands in the boundary elements and steel fiber volume ratios (SFVRs) on the seismic performance of proposed shear walls. The results showed adding steel fibers could significantly reduce the damage level of shear walls. Both reinforcing steel strands in the boundary elements and using SFRC could efficiently enhance the bearing capacity and resilient capacity of shear walls, and increased with the increasing SFVRs. Compared with RC shear wall, the peak loads of the SSFRC shear walls with 0%, 0.75% and 1.50% SFVRs increased by 15.8%, 27.7% and 34.5%, and the residual displacement of them decreased by 49.3%, 59.0% and 63.1% at 2.00% loading level, respectively. In addition, reinforcing steel strands in the boundary elements significantly reduced the energy dissipation of shear walls, but using SFRC could enhance the energy dissipation. As the SFVRs increased to 1.50%, the final cumulative energy dissipation of SSFRC shear walls was similar to that of RC shear walls. Finally, the calculation methods for cracking load, steel yielding load and peak load of the SSFRC shear walls were proposed, and the acceptable accuracy was verified by comparing the calculated and experimental results.

Study on the evolution patterns of concrete lining’s physical and mechanical properties under sulfuric acid corrosion conditions

During operation, deep water storage and drainage tunnels may face sulfuric acid corrosion resulting from microbiologically induced chemical reactions. In this study, sulfuric acid corrosion experiments were performed on C60 concrete specimens with steel fiber volume ratios of 0% (plain) and 1% using a sulfuric acid solution with an initial pH of 1. For one-face corrosion, five faces of cubic concrete samples were coated with exposed resin, leaving only one face exposed to sulfuric acid. For all-face corrosion, all faces were exposed to sulfuric acid. Concrete corrosion under different loading conditions was compared by adding weights on top of the concrete. Rate of mass change variations and uniaxial compressive strength at various corrosion time points were monitored. The results indicated that after sulfuric acid corrosion, there was an increase in the mass but an overall decrease in the strength of the specimens. Compared with all-face corrosion, one-face corrosion led to a smaller increase in the mass of the concrete specimens and a more substantial decrease in strength, primarily because of the slower corrosion rate and reduced gypsum formation. Compared to plain concrete, steel fiber-reinforced concrete experienced a lower increase in the mass of the concrete specimens because the steel fibers obstructed sulfuric acid infiltration. However, there was significant corrosion of the steel fibers and surrounding concrete owing to accumulation of sulfuric acid around the former, resulting in a more substantial decrease in the uniaxial compressive strength of the steel fiber-reinforced concrete. With increasing load, the rate of change in the concrete mass initially decreased and then increased; this could be because increased loads densify the concrete, hindering sulfuric acid infiltration and promoting the development of microcracks within the concrete, thereby enhancing the effects of sulfuric acid corrosion.

Dynamic compressive behavior of steel fiber synergistically reinforced cellular concrete under high strain-rate loading

To better understand the reinforcement and toughness effects of steel fibers, a 75-mm split Hopkinson pressure bar (SHPB) device was used to test the uniaxial dynamic compression properties of steel fiber synergistically reinforced cellular concrete (SFSRCC) under high strain rates. The dynamic compression performance characteristics of the SFSRCC, including the stressstrain curve, dynamic strength, impact toughness and failure mode, were analyzed. The results showed that the dynamic strength, peak strain and impact toughness of SFSRCC increase with increasing strain rate. Compared with that of cellular concrete (SAP10S0), a higher steel fiber volume ratio corresponded to a greater enhancement in the dynamic performance characteristic indices of the SFRCC. The maximum increases were 138.4%, 180.0% and 280.0% for the DIF, peak strain, and impact toughness, respectively. The damage degree of the SFSRCC specimen decreased with increasing fiber content, and a larger area of residual "core retention" was observed, which indicated that the impact resistance of the SFSRCC with a high fiber content was improved. An empirical formula that can accurately characterize the dynamic strength increase factor (DIF) of SFSRCC with high strain rates was proposed, and the prediction results obtained by using the DIF of the SFSRCC were highly consistent with the test results, which confirmed its effectiveness. To further quantify the strain rate enhancement effect and fiber content for the reinforcement and toughening ability of SFSRCC, the relationships between the peak strength/peak strain/impact toughness and strain rate and between the DIF increment ratio/strain energy density increment ratio and fiber volume fraction were determined. In conclusion, the dynamic compression performance characteristics of SFSRCC can be enhanced by incorporating an appropriate quantity of steel fibers with a dynamic impact load.

Dynamic compressive behaviors of polyethylene terephthalate fiber reinforced recycled aggregate concrete

AbstractPolyethylene terephthalate (PET) fibers are green, environmentally friendly materials. They mainly come from recycled plastic bottles and other products. The addition of PET fibers to recycled aggregate concrete (RAC) has the potential to reduce concrete damage and increase specimen toughness. In this study, the influences of recycled coarse aggregate (RCA) replacement ratio and fiber volume ratio on the impact response of PET fiber reinforced RAC at various strain rates were experimentally investigated. It was found that the compressive strength, critical strain, and toughness grew with the increasing strain rate, followed by the aggravation of the concrete damage. Owing to the strain rate effect, the failure mode of concrete specimen at a high strain rate was different from that under a quasi‐static loading. This led to the reduction of differences in the dynamic compressive strength between the natural and recycled aggregate concrete at a high strain rate. Although the replacement of natural coarse aggregates with RCAs resulted in the decrease in the dynamic compressive strength, it increased the critical strain of the specimen. To reduce the brittleness of concrete materials, flexible fibers, PET fibers were added into the concrete matrix. It was found that the addition of PET fibers increased the critical strain and significantly reduced concrete damage. The empirical equations were proposed to describe the rate‐dependent dynamic compressive strength, critical strain, and toughness based on experimental data.

The Properties of High-Performance Concrete with Manganese Slag under Salt Action.

Manganese slag (MS) containing a certain amount of active hydration substances may be used as a kind of cementitious material. In the present study, we measured the mass, the relative dynamic modulus of elasticity (RDME), and the flexural and compressive strengths of MS high-performance concrete (MS-HPC) with added basalt fibers exposed to NaCl freeze-thaw cycles (N-FCs), NaCl dry-wet alternations (N-DAs), and Na2SO4 dry-wet alternations (NS-DAs). Scanning electron microscope energy-dispersive spectrometer (SEM-EDS) spectra, thermogravimetric analysis (TG) curves, and X-ray diffraction spectroscopy (XRD) curves were obtained. The mass ratio of MS ranged from 0% to 40%. The volume ratio of basalt fibers varied from 0% to 2%. We found that, as a result of salt action, the mass loss rate (MLR) exhibited linear functions which were inversely correlated with the mass ratio of MS and the volume ratio of basalt fibers. After salt action, MLR increased by rates of 0~56.3%, but this increase was attenuated by the addition of MS and basalt fibers. Corresponding increases in RDME exhibited a linear function which was positively correlated with MS mass ratios in a range of 0~55.1%. The addition of MS and basalt fibers also led to decreased attenuation of mechanical strength, while the addition of MS led to increased levels of flocculent hydration products and the elements Mn, Mg, and Fe. CaClOH and CaSO4 crystals were observed in XRD curves after N-DA and NS-DA actions, respectively. Finally, the addition of MS resulted in increased variation in TG values. However, the opposite result was obtained when dry-wet actions were exerted.

Effect of fiber volume and material property and nucleus pulposus area on intervertebral disc mechanical behavior

The material properties and volume proportion of the fibers as well as the cross-sectional area proportion of nucleus pulposus vary greatly in different studies. The effect of these factors on the mechanical behavior of intervertebral discs (IVDs) are uncertain. The IVDs finite element models with different parameters were created to investigate the pressure, height, rotation, stress, and strain of the IVDs under loads: pure compression, rotation after compression or axial moment after compression. The results showed that the material properties of fibers had great impact on the mechanical behavior of IVDs, especially on the rotation angle. When the fiber volume ratio was small, its changes had a significant impact on the rotation angle of the IVDs. The area proportions of nucleus pulposus had relatively little effect on the mechanical behavior of IVDs. The IVDs rotation should be observed when validating the model. By adjusting the elastic modulus or volume ratio of fibers within a reasonable range, a model that could simulate the mechanical behavior of normal IVDs could be obtained. It was reasonable to make the area proportion of nucleus pulposus within 25%-50% for the IVDs finite element model. This study provides guidance and reference for finite element modeling of the IVDs and the investigation of the IVDs degeneration mechanism.

Study on bending failure and crack characteristics in ductile fiber‐reinforced concrete beams

AbstractIn this study, we designed six polypropylene fiber‐reinforced concrete (PP‐FRC) beams and three reinforced concrete (RC) beams for experimental studies. Then, we analyzed the effects of incorporating PP fibers on the cracking performance of PP‐FRC beams from the perspectives of load‐displacement response, crack distribution, crack depth, crack width, crack spacing, and deformation coordination. The research results showed that the cracking load and number of cracks were positively correlated with the volume ratio of PP fibers, while the maximum crack width, average crack spacing, and average crack depth were negatively correlated with the volume ratio of PP fibers. Due to the bridging effect of fibers, the PP‐FRC beam body and reinforcement could deform in a coordinated manner within a specific loading range after cracking, which increased the deformation coordination ability between the body and reinforcement. In this study, the cracking mechanism of PP‐FRC beams was investigated. Firstly, the formula for calculating the cracking moment of PP‐FRC beams was derived from the perspective of equivalent bending tensile strength. Then, based on the fiber bridging law and the bond strength between PP‐FRC and reinforcement, theoretical formulas were proposed to predict the average crack spacing and maximum crack width of PP‐FRC beams. Finally, through comparison, it was found that the proposed formulas could be used for characteristic crack prediction.

An ICME framework for short fiber reinforced ceramic matrix composites via direct ink writing

A manufacturing-driven ICME framework is proposed to model short fiber reinforced ceramic matrix composites (CMCs) via direct ink writing. Currently, there lacks efforts to investigate the effects of properties of short fiber reinforced CMCs due to fiber alignment variance. A multi-scale modeling approach is presented to use representative volume elements to capture the homogenized mechanical behavior at various fiber aspect ratios and volume ratios. The orthotropic material properties are mapped to model the printing process. A series of tensile tests simulations show that with 20∘ standard deviation in fiber alignment, the fracture plane has the maximum local tensile stress range at a printing angle of 30∘ and has the minimum local tensile stress range at 90 ∘ . When the standard deviation increases from 20∘ to 40∘, the average tensile strength across the fracture plane decreases by 2%, but the stress variations increase 27.6%.