Fiber Fractions Research Articles

ОТЗЫВЧИВОСТЬ ГИБРИДА КУКУРУЗЫ НУР НА ЛИСТОВЫЕ ПОДКОРМКИ КАРБАМИДОМ И СТИМУЛЯТОРОМ РОСТА ИЗАГРИ ВИТА В ПОЧВЕННО-КЛИМАТИЧЕСКИХ УСЛОВИЯХ РЕСПУБЛИКИ ТАТАРСТАН

The feed potential of the universal early-maturing hybrid corn Nur was studied in the conditions of the Ancestral region of the Republic of Tatarstan on gray forest heavy loamy soils. The content of humus in the arable layer was characterized as increased by 4.4 %, mobile phosphorus as very high - more than 377 mg/kg, exchangeable potassium increased – 124 mg/kg. The soil had a medium reaction close to neutral (pH 6.3). Meteorological conditions in 2023 were characterized as arid with a lack of precipitation during the growing season of corn. To obtain high-quality feed from corn, different corn nutrition systems were studied: without fertilizers, background N16P16K16, background N16P16K16 + urea leaf dressing in the 5-7 leaf phase, background N16P16K16 + Izagri Vita leaf dressing in the 5-7 leaf phase, background N16P16K16 + Izagri Vita leaf dressing in the 5-7 leaf phase and cob formation. Izagri Vita is a growth stimulant with trace elements. Improving the nutritional conditions of corn extends the growing season by 2-3 days. Corn responds positively to the application of mineral fertilizers and carrying out leaf fertilization with carbamide. This technique ensures the formation of the highest plant height (159.7 cm) and leaf area (42.19 thousand m2/ha). The largest aboveground mass was formed on the von NPK+ variant Izagri Vita 44.50 t/ha. Biometric indicators of corn also improved on fertilized food backgrounds. The highest yield of green mass was obtained on the variants background NPK and background NPK + Izagri Vita (2 phases) (45.81 and 41.88 t/ha). The increase in yield from the applied mineral fertilizers amounted to 16.25 and 12.31 t/ha. Better nutrition of corn provides a more nutritious feed from corn. The NPK background variant had the highest mass fraction of dry matter (86.3 %), crude fiber (35.0 %), and NPK background + From graphite, where the mass fraction of nitrogen was 20.5 g/kg, crude protein 128.2 g/kg, phosphorus 1.0%.

USING MACHINE LEARNING TO PREDICT THE MECHANICAL PROPERTIES OF PET FIBER-REINFORCED CONCRETE

Fiber-reinforced concrete enhances structural integrity by improving post-cracking behavior and ductility, yet traditional fibers can be costly and have a significant environmental impact. Recently, polyethylene terephthalate (PET) fiber, derived from recycled plastic bottles, has been used as a reinforcing material in concrete to enhance its mechanical properties. Utilizing advanced machine learning algorithms, this research analyzes a comprehensive dataset collected from existing literature on the mechanical properties of PET fiber-reinforced concrete (PFRC), including concrete density, water-to-binder ratio, fine and coarse aggregates, and fiber parameters such as volume fraction and aspect ratio of PET fibers. Through the application of Polynomial Regression, Exponential Gaussian Process Regression (GPR), and Cubic Support Vector Machine (SVM) models, the study effectively predicts PFRC’s mechanical behavior, showcasing high R² values indicating the models’ predictive strength: 0.93 for compressive, 0.92 for flexural, and 0.92 for tensile properties. This investigation highlights the exceptional accuracy of Exponential GPR and Cubic SVM models in capturing complex, non-linear relationships within the material, demonstrating machine learning’s capability to advance the sustainable development of construction materials. This study provides significant insights into optimizing the use of recycled fibers for concrete reinforcement.

USING MACHINE LEARNING TO PREDICT THE MECHANICAL PROPERTIES OF PET FIBER-REINFORCED CONCRETE

Fiber-reinforced concrete enhances structural integrity by improving post-cracking behavior and ductility, yet traditional fibers can be costly and have a significant environmental impact. Recently, polyethylene terephthalate (PET) fiber, derived from recycled plastic bottles, has been used as a reinforcing material in concrete to enhance its mechanical properties. Utilizing advanced machine learning algorithms, this research analyzes a comprehensive dataset collected from existing literature on the mechanical properties of PET fiber-reinforced concrete (PFRC), including concrete density, water-to-binder ratio, fine and coarse aggregates, and fiber parameters such as volume fraction and aspect ratio of PET fibers. Through the application of Polynomial Regression, Exponential Gaussian Process Regression (GPR), and Cubic Support Vector Machine (SVM) models, the study effectively predicts PFRC’s mechanical behavior, showcasing high R² values indicating the models’ predictive strength: 0.93 for compressive, 0.92 for flexural, and 0.92 for tensile properties. This investigation highlights the exceptional accuracy of Exponential GPR and Cubic SVM models in capturing complex, non-linear relationships within the material, demonstrating machine learning’s capability to advance the sustainable development of construction materials. This study provides significant insights into optimizing the use of recycled fibers for concrete reinforcement.

Feed intake, fiber fraction digestibility and milk yield of lactating goats fed banana peel in the diet

Feed intake, fiber fraction digestibility and milk yield of lactating goats fed banana peel in the diet

Study of the effective fraction of areca nut husk fibre composites based on mechanical properties

Areca nut husk fibers have the potential to be used as reinforcement in polymer composites as a substitute for synthetic fibres. In the manufacture of fibre composites, one of the important factors in determining the strength is the matrix to fibre ratio. This study aims to determine the effective ratio or fraction between areca nut husk fibre and orthophthalic polyester resin. Before using areca nut husk fibre, it was chemically treated so that only cellulose remained in the fibre. The areca nut husk fibre was processed into sheets. The composite was manufactured using the hand lay-up technique. Tensile and flexural tests were carried out to determine the mechanical properties. Based on the results of the tests conducted, there are differences in the mechanical properties of the composites. The tensile test results show that the 40% fibre fraction has the highest tensile strength and modulus values. On the other hand, in the flexure tests, the highest tensile strength and modulus values are found in the 30% fibre fraction.

Study on the bond properties between BFRP bars and hybrid fibers reinforced recycled concrete under freeze-thaw cycles

To study the bond properties between basalt fiber reinforced polymer (BFRP) bars and hybrid fibers which were basalt fiber (BF) and polypropylene fiber (PF) reinforced recycled concrete under freeze-thaw cycles, conducting center pull-out tests to study the effects of three factors on the bond properties: the number of freeze-thaw cycles, the volume fractions of single fiber, and the volume fractions of hybrid fibers. Based on the data obtained from the test, establishing a four-stage bond-slip constitutive relationship model. The results showed that the failure modes were pull-out failure and splitting failure. The bond strength decreased when adding the single fiber, with a maximum reduction of 13.18%, but the peak slip increased, with a maximum increase of 69.92%. When the volume fraction of BF was 0.3%, it achieved the optimal effect. The bond strength and peak slip increased when adding hybrid fibers, with maximum increases of 13.47 and 130.08%, respectively. However, excessive fiber content will reduce the increase of bond strength. The bond strength between BFRP bars and hybrid fiber-reinforced recycled aggregate concrete (HFRAC) increased when the number of freeze-thaw cycles increased but decreased when the number of freeze-thaw cycles exceeded 50. The four-stage bond-slip constitutive relationship model fitted well with the bond-slip curves. Compared with other fiber-reinforced recycled concrete specimens, this model fitted better with the curves of HFRAC specimens after freeze-thaw cycles and had the best fitting effect for the internal crack slip stage of the curves.

Drying Shrinkage Properties of Arched Steel Fiber Reinforced Concrete by Volume Fraction of Steel Fiber

Drying Shrinkage Properties of Arched Steel Fiber Reinforced Concrete by Volume Fraction of Steel Fiber

Investigation of the effects of volume fraction, aspect ratio and type of fibres on the mechanical properties of short fibre reinforced 3D printed composite materials

AbstractMechanical behaviour of 3D-printed composite parts is affected by the volume fraction, aspect ratio and type of fibre reinforcement. Although in the literature experimental approaches have been used to characterise the effects of the above factors on the mechanical properties of 3D printed parts, time and cost of the manufacturing process as well as the uncertainty associated with a large number of experimental techniques are the key issues. This study aims to address these challenges by developing a methodology based on a multi-scale Finite Element (FE) analysis of representative volume element (RVE) of 3D printed composite parts to predict the effective orthotropic properties. To account for the effects of fibre features, RVEs were modelled considering variables of volume fraction, aspect ratios and type of short fibres. To study the main and interaction effects of the above variables on the mechanical properties of 3D printed composite parts, a structured approach based on the Design of Experiments is used. The FE stress analysis of the RVE provides an understanding about the potential failure modes such as interfacial debonding between fibres and matrix, interlayer and intralayer delamination that may occur in load-bearing 3D printed composite parts. The FE computed mechanical properties are validated against experimental data through a series of mechanical testing of flexure, Iosipescu, and short beam shear which were conducted in conjunction with the Digital Image Correlation technique. As a result, certainty is obtained in using the proposed approach for a fast iterative design of 3D printed composite parts prior to industrial applications.

The influences of type, length, and volumetric fraction of fibers on the direct shear strength of the fiber-reinforced concretes

Besides the common modes of failure including compressive, tensile, and bending in concrete structures, cracking and failure due to the shear is also considered as a significant and hazardous mode of failure. The shear failure mode can be observed in structural elements such as deep beams, locations having high point loads, connection cores of beams and concrete columns, short columns, punching shear in slabs and foundations, etc. However, the direct shear strength of the fiber-reinforced concretes has seen limited studied. Hereupon, this study aims to experimentally investigate the influences of the type, length, and various volumetric fractions of the steel fiber (SF) and polypropylene (PP) fiber on the compressive strength, the tensile strength, and specifically on the direct shear strength of the fiber-reinforced concretes. To this end, four different mixture design schemes of the plain concrete were examined by adding PP and SF with lengths of 3 cm, 5 cm, and their half-half combination with volumetric fractions of 0.5 %, 1 %, and 1.5 % to measure the compressive strength (the cubic sample), the tensile strength (the cylindrical sample), and the direct shear strength (the prismatic sample) of the concrete specimens. In addition, the plain concrete specimens as the witness specimens were built to compare with fiber-reinforced ones. The experiments were not only performed for 20–25 MPa concrete strength category, but were also executed for 25–30 MPa. The constructed concrete specimens were exhaustively surveyed in terms of the contribution of the fibers, the failure patterns in various specimens, the force-displacement diagrams in shear, the maximum displacement in specimens, the aspect ratio of the fibers, and the shear ductility index in various specimens. The obtained results indicated that, with increasing the length and volumetric fraction of the fibers (i.e., the aspect ratios), the compressive, tensile, and direct shear strengths have been subsequently augmented in the concrete specimens. Moreover, the strain and ductility of the concrete specimens have also been enhanced. Remarkably, in most tests, the SF-reinforced specimens have excellent performance compared with other specimens. However, the specimens containing the PP fibers have not considerably improved the compressive and direct shear strengths of the concrete specimens.

Improving mechanical and thermal expansion properties of aluminum matrix composites reinforced by silicon carbide fiber

Combining the colloidal dispersion method with the squeeze melt infiltration technique, aluminum matrix composites with different volume fractions of silicon carbide fiber were fabricated at 680 °C under vacuum. Microstructure analysis found that composite presented a dense structure and fibers were homogeneously distributed in matrix. The hardness, yield strength and elastic modulus of the composite monotonically increased with increasing the volume fraction of fiber. The highest flexural strength for composite with 10 vol% SiC fiber was achieved. The improved mechanical properties could be attributed to the dispersion strengthening and enhanced load transferring ability by fibers as well as the dislocation strengthening. On the other hand, the coefficient of thermal expansion of composites was measured at temperature up to 400 °C. It was found that the uniform introduction of silicon carbide fiber could significantly low the CTE of aluminum matrix composite, which could be attributed to the low CTE of SiC fiber and good fiber–matrix interface bonding.

Study on the biaxial mechanical behavior of steel fiber reinforced recycled aggregate concrete

Steel fiber reinforced recycled aggregate concrete (SFRAC) was proposed considering the enhancement of mechanical properties by incorporating steel fibers and the reduction of environmental impacts and cost due to the addition of recycled aggregates. To better understand the mechanical properties of SFRAC under biaxial compression and its failure criteria, 150 SFRAC specimens were prepared with different replacement ratios of recycled coarse aggregate (50%, 75%, 100%) and volume fractions of steel fibers (0%, 0.6%, 1.2%, 1.8%). In addition, various stress ratios were considered in the biaxial compression test (σ1:σ2=0:1.0, 0.2:1.0, 0.5:1.0, 0.7:1.0, 1.0:1.0). The results indicated that the failure of SFRAC was observed as columnar and splitting modes depending on the biaxial stress ratio. The impacts of the considered variables on the biaxial peak strength were studied. The increasing volume fraction of steel fibers tended to improve the biaxial peak strength of SFRAC within a threshold beyond which the impact was negative. Similarly, the biaxial strength of most SFRAC samples showed a pessimum effect when the biaxial loading stress ratio was higher than 0.7, though they were still higher than the uniaxial compressive strength. A failure criterion for SFRAC under biaxial compression loading is proposed, in which four parameters are included. The calculations are in good agreement with the experimental results.

Dynamic mechanical behavior of steel fiber reinforced-recycled aggregate concrete subjected to uniaxial loading

The objective of this study was to investigate the dynamic mechanical performance of steel fiber reinforced-recycled aggregate concrete (SFRAC) under uniaxial loading. A total of 22 groups of cylindrical samples, each measuring 100 mm × 200 mm, were subjected to uniaxial compression. The investigation placed particular emphasis on examining the influence of variables such as the strain rate, volume fraction of steel fiber (Vsf), volume fraction of polyvinyl-alcohol (PVA) fiber (Vpf) and substitution ratio of recycled coarse aggregate (SRCA) on the failure modes, stress-strain curves and deformation ability. The results revealed that the incorporation of steel fibers and PVA fibers enhanced the overall integrity of fractured samples, and induced changes in the failure modes. In particular, the maximum increase in uniaxial compressive strength attributed to strain rate, Vsf and Vpf reached up to 15.0%, 23.57% and 8.57%, respectively. Although the inclusion of recycled aggregates had no significant influence on the failure mode, it decreased the compressive strength by up to 16.34%. Finally, a dynamic stress-strain theoretical constitutive model was established in this paper. The predictions derived from this model closely aligned with the experimental stress-strain curves obtained during the conducted tests. This study provides valuable insights for applications of SFRAC in structural engineering.

Effects of Palm Oil Deodorizer Distillate on the Ruminal Environment of Sheep.

This study aimed to assess the impact of palm oil deodorizer distillate (POD) on the ruminal environment, including (i) microbial community, (ii) ruminal degradability, and (iii) apparent digestibility in sheep. The data used were derived from twenty rumen-cannulated sheep fed five isoproteic and isofiber diets based on elephant grass (Pennisetum purpureum Schum. cv. Roxo) silage supplemented with 0, 25, 50, 75, or 100 g kg-1 POD on a dry matter (DM) basis. Rumen fluid samples were collected three hours after feeding directly from the ventral sac of the rumen via a cannula and then subjected to DNA extraction, which was subsequently used for 16S rDNA amplification, followed by sequencing and diversity analysis. In this study, the microbial diversity was dominated by Bacteroidetes and Firmicutes, followed by Euryarchaetoa, Actinobacteria, and Tenericutes, in the ruminal environment, and was slightly modified when supplemented with the POD up to 100 g/kg (10%), leading to only a slight decrease in the diversity index. The ruminal degradability, ruminal fermentation parameters, and apparent digestibility were slightly compromised by the inclusion of up to 25 g of POD per kg of DM, and larger inclusions interfered with the ruminal degradability of fibrous fractions and the apparent digestibility of dry matter. This lipid supplement showed good results for feeding sheep and is an inexpensive and abundant alternative in the regional market.

Techno-functional characteristics, mineral composition and antioxidant potential of dietary fiber extracted by sonication from different oat cultivars (Avena sativa)

Metabolic disorders including hypertension, diabetes and cardiovascular disease etc. are the major threats to public health and economy. Management and prevention of alarmingly increased aforementioned disorders has attracted researchers to explore their natural remedies. The objective of this study was to explore ultrasonically extracted dietary fibers from indigenous oat cultivars (SGD2011, Avon, SGD81, PD2LV65, and S2000) for their techno-functional characteristics, mineral composition and phytochemicals. These characteristics will find the way to ultimately use oats in food and feed industries to address consumer demand. Extraction of dietary fibers from oat cultivars was optimized by response surface methodology. These cultivars varied significantly (p < 0.05) for oil holding capacity, water saturation and water holding capacity. The SGD81 cultivar showed the highest oil holding capacity, water holding capacity and water saturation due to its highest fraction of dietary fiber. The highest values of total phenolic contents, total flavonoid contents, total flavonol contents, 2,2-Diphenyl-1-picrylhydrazyl radical scavenging activity, and anthocyanins were shown by SGD81, and SGD2011. All cultivars varied significantly (p < 0.05) with respect to phytochemical quantification. The cultivars SGD81 and SGD2011 showed the best phenolic acid profile and can be effectively used as source of nutraceutical. Beyond well-established nutritional properties of oat, these may also contribute dietary fibers for their nutraceutical properties. This approach can protect people from metabolic disorders. Moreover, extraction of dietary fibers through sonication can be considered an eco-friendly strategy.

Study on fracture characteristics of steel fiber reinforced manufactured sand concrete using DIC technique

Incorporation of steel fibers to improve the defects of manufactured sand concrete (MSC) has received a great deal of attention, while the fracture mechanism of the MSC by volume fraction of steel fibers (Vf) has been less studied. To investigate the effects of steel fibers on the fracture characteristics of the MSC, three-point bending tests were conducted on the MSC beams with different Vf (0, 0.5 %, 1.0 % and 1.5 %) using digital image correlation technique. The effects of Vf on the fracture parameters and crack propagation paths of steel fiber reinforced manufactured sand concrete (SFRMSC) were analyzed. In addition, fracture process zone (FPZ) of the SFRMSC was analyzed via the length of the FPZ (lFPZ) and area of the FPZ (AFPZ). The results indicated that the residual strength, initiation fracture toughness, unstable fracture toughness, fracture energy and characteristic length of the SFRMSC increased with the increase of Vf, whereas the crack propagation paths were not sensitive to the changes of Vf. The addition of steel fibers increased the interaction between the aggregate and the matrix, which led to an increase in the number of microcracks. Before approaching the Pc, both the lFPZ and AFPZ showed essentially stable changes. As Vf increased, the lFPZ and AFPZ developed faster to their corresponding maximum values. The AFPZ reached a maximum and increased with the Vf. At the Pc, the lFPZ and AFPZ changed in a similar trend when Vf ≤ 1.0 %. When Vf > 1.0 %, the lFPZ changed slightly while the AFPZ increases sharply.

Maximization of brackish water productivity for the sustainable production of striped catfish (Pangasianodon hypophthalmus) and grain sorghum (Sorghum bicolor (L.) Moench) cultivated under an integrated aquaculture–agriculture system

Freshwater scarcity, salinity, and poor soil fertility are the major challenges affecting both food and feed productions in arid and semi-arid regions of the world. Utilization of brackish water in the production of saline-tolerant fish and valuable field crops under an integrated system is promising in the maximization of yield per crop. The aim of this study, therefore, was to (1) assess the effect of saline aquaculture wastewater on the growth, yield, forage quality, and nutritive composition of sorghum seeds and (2) assess the effect of different water qualities on the survival, growth performance, and health status of Pangasianodon hypophthalmus. The experiment was conducted in a randomized completely block design of four salinity treatments with three replicates, i.e., control (freshwater mixed with inorganic fertilizers), 5000 ppm, 10,000 ppm, and 15,000 ppm. Our results indicated that although the control exhibited the highest growth (plant height, leaf number, internode number, leaf area, and soil–plant analysis development), grain, and forage yield, no significant differences were noted among the treatments. Likewise, no significant difference in the grain nutrient composition was noted among all the treatments. Assessment of the forage quality revealed improved crude protein content in the control compared to the saline treatments. However, no significant differences in the leaves and stalks fiber fractions were noted among all the treatments. Furthermore, rumen fermentation in terms of in vitro digestibility indicated no significant differences in the in vitro digestible dry matter, digestible organic matter, metabolic energy, net energy, microbial protein, short-chain fatty acids, and total dissolved nutrients among the treatments. However, rearing P. hypophthalmus in water salinities exceeding 10,000 ppm reduced the growth performance and health status of fish. Therefore, the integration of sorghum and P. hypophthalmus production in water salinities not exceeding 5000 ppm is a viable alternative to maximize brackish water productivity in freshwater-scarce regions.

The role of flexural particles in the shear flow of pine residue biomass: An experiment-informed DEM simulation study

An experiment-informed discrete particle simulation study was performed to investigate the role of flexural particles in the shear flow of milled pine residues. Physical pine anatomical fraction samples were tested in an FT4 powder rheometer. A chip model for bark/stem chips and a fiber model for needles were proposed for DEM. The FT4 simulations show mixed fibers/chips require higher force and torque to drive shear flow than pure chips or fibers. The mass fraction and flexibility of fibers reveal nonlinear inter-dependency on impacting the shear flow of mixed fibers/chips. Polydisperse fibers well match the needle-rich samples on the flow attributes, while polydisperse mixed fibers/chips agree reasonably with the bark/stem-rich samples. The DEM study indicates that the flowability of pine residue biomass is determined collectively by various material attributes of the anatomical fractions, which must be considered when developing preprocessing methods for conversion-ready biomass with adequate material handling performance.

A multiscale experimental study of CFRP-UHPFRC interfacial bond behaviour: Failure mechanisms and a fibre volume dependent bond-slip law

Carbon fiber reinforced polymer (CFRP) materials are being increasingly used with ultra high performance fiber reinforced concrete (UHPFRC) to construct composite structural members making use of their unique properties. As the interfacial bond behaviour between CFRP and UHPFRC plays a key role in the design of such members, it was investigated in detail by multiscale experiments of single shear pull-off tests of 26 CFRP-UHPFRC bonded joints with different bond lengths and widths of CFRP laminates and 0.5–4% volume fraction (Vsf) of straight high-strength steel fibers (length = 13 mm, diameter = 0.2 mm). 12 CFRP-normal strength concrete (NSC) bonded joints were also tested for comparison. The surface strain evolution and the interfacial debonding process were captured and analysed by the digital image correlation (DIC). The complex microscale failure mechanisms, such as the mortar cracking, the CFRP-UHPFRC interfacial debonding, and the steel fibers’ slipping and pulling out of the mortar, were visualised and analysed by the 3D micro X-ray Computed Tomography (μXCT) scanning. It was found that the debonded layer of mortar under the laminates was much thinner than that in the CFRP-NSC bonded joints, due to the lack of coarse aggregates in UHPFRC. The peak pulling forces for the specimens with Vsf = 0.5%, 1%, 2%, and 4% were 9%, 21%, 28%, and 29% higher than those without steel fibers, respectively. An empirical bond strength model and an interfacial bond-slip model were proposed based on the test results, accounting for Vsf, the material properties, and the laminate to UHPFRC width ratio. Finally, the proposed bond-slip model was applied in finite element modelling to simulate the flexural behaviour of an FRP-UHPFRC composite deck in the literature, with the interfacial debonding failure and the ultimate loads successfully predicted.

Performance of novolac resin‐ and resole resin‐based carbon/carbon composites in relation to their fabrication conditions

AbstractThe demands of cost‐driven industrial applications can be satisfied by manufacturing composites with a low volume fraction of carbon fibres as phenolic carbon fibre‐reinforced composites and C/C composites, both with acceptable performances, for low‐ or high‐temperature applications, respectively. Polymeric composites reinforced with a low volume fraction (7.5% v/v) of carbon fibres were fabricated using laboratory‐produced phenolic resins, novolac (N) and resole (R), as matrices after different curing/post‐curing temperature profiles. By optimising the manufacturing conditions, the N‐based polymeric composites exhibited higher flexural strength, whereas the R‐based composites showed higher shear strength. C/C composites, namely N‐based and R‐based, were manufactured by pyrolysis of the previously prepared polymeric composites up to 1000 °C. The pyrolysed composites were then densified by impregnation with an appropriate resin solution, followed by curing and new pyrolysis, and particularly by employing 1 up to 4 consecutive cycles of ‘impregnation–curing/pyrolysis’. Weight changes resulting from the impregnation–curing and pyrolysis stages were determined. The curing of both resins was verified by Fourier Transform Infrared Analysis. The apparent density and X‐ray diffraction data of the C/C composites were used to calculate their total percent porosities. The morphology and elemental composition of the C/C composites at their failure region (after flexural testing) were examined by Scanning Electron Microscopy/Energy‐Dispersive X‐ray Analyses. In comparison to the N‐based C/C composites, the R‐based ones exhibited: higher shear strength, lower flexural strength, higher Shore D hardness, slightly higher surface conductivity and lower volume conductivity. The optimum conditions for the manufacture of C/C composites were achieved by applying two consecutive cycles of ‘pyrolysis–impregnation–pyrolysis’ to the polymeric composites. © 2024 The Authors. Polymer International published by John Wiley &amp; Sons Ltd on behalf of Society of Industrial Chemistry.

Effect of steel fiber orientation on punching shear resistance of steel fiber reinforced cementitious composites round slabs

The slab-column structure is commonly used in civil engineering. At the slab-column joints, the load from the slab is transmitted to the column. In the extreme state, punching shear failure may occur at the joints, and the failure is brittle without warning. When the punching shear failure occurs at the joint of round slab and column, usually the cracking is a conical shape because the direction of tensile stress caused by punching shear is generally radial. By incorporating steel fibers into cementitious composites round slabs, the steel fibers can bridge the conical surface, and therefore enhance the punching shear resistance of round slabs. If the steel fibers in the round slab are dispersed in the direction conducive to the punching shear resistance, the steel fibers can take full effect of strengthening and toughening, thus improving the punching shear resistance of the slab. So, the purpose of this investigation is to improve the punching shear resistance of steel fiber reinforced cementitious composite slabs by maximizing the reinforcement of steel fibers on the composites. Firstly, a model of punching shear resistance of steel fiber reinforced cementitious composite round slabs was derived based on the Modified Compression Field Theory with consideration of the orientation of steel fibers. According to the model, the slab with radial distribution of steel fibers around the punching shear area shows the highest punching shear resistance. Secondly, the approach of radially aligning steel fibers in the slab around the punching area by magnetic driving is proposed using a self-developed magnetic device. And, radially dispersed steel fiber reinforced cementitious composites (JD-SFRC) round slabs were prepared. Thirdly, the punching shear resistance of JD-SFRC round slabs, as well as unidirectionally aligned (1D), two-dimensionally aligned (2D), and randomly distributed (RD) steel fiber reinforced cementitious composites round slabs were tested. At last, the effect of the orientation of steel fibers on the punching shear resistance and failure characteristics of the round slabs were analyzed by comparing the results from tests and the model. Meanwhile, the effect of the volume fraction of steel fibers on the punching shear resistance of the slab was examined. The results show that, When the volume fraction of steel fiber is 1.0 %, compared with RD-SFRC round slabs, the ultimate shear resistance of 1D-SFRC, 2D-SFRC and JD-SFRC round slabs is increased by 14 %, 15 %, and 24 %, respectively.