Fiber Volume Percentage Research Articles

An investigation of clay percentage variation on composite materials sustainability identification by digital image correlation

ABSTRACT The study focuses on stress and strain evaluation of composite resin material with the reinforcement of clay in the glass-reinforced epoxy composite (GREC). The strain measurement used the DIC technique. The tensile test specimens were prepared from the laminate sheets as per ASTM D638 standard. The influence of nano clay weight percentage such as 2.5%, 3.5%, and 4.5% during preparation of GREC is studied in the article. The fibre orientation angles are 90°, and the fibre volume percentage is 45%. Hand lay-up methods are used to prepare the composite resin material. The samples were tested as per the standardised procedures. The specimen rupture at a localised strain reached a maximum value of 0.01293, 0.01571, and 0.0143 with 2.5%, 3.5% and 4.5% Nano clay, respectively. The material behaviour in terms of major strain (εyy), Poisson’s ratio (µ) and thickness strain (Δt) is evaluated at the gauge length of the specimen. DIC strain measurement clearly demonstrates the 3.5% percentage of clay addition as it yields better results as elastic modulus and tensile strength have improved. The composite resin with clay addition could be used in various applications, such as low-cost housing, structural works, medical devices, automotive panels, etc

Mechanical characteristics of optimized alkali-treated Similax Zelanica/glass fiber/nanosilica composites in an epoxy matrix: An experimental investigation and numerical study

The demand for environmentally conscious materials has led the research on natural fiber composites as an alternative to synthetic materials in various industries. This study focuses on the optimization and preparation of alkali-treated Similax Zelanica/glass fiber and nanosilica-reinforced epoxy composites. The weight % of Similax Zelanica/glass and nanosilica was optimized using the grey relational analysis (GRA) multiparameter optimization technique and DOE of L9 orthogonal was used. Mechanical properties including tensile, flexural, impact, rock well hardness, and dynamic mechanical analysis were evaluated. Results indicate that increasing fiber volume fraction up to 30% enhances mechanical properties, with subsequent declines beyond this threshold. Tensile strength peaked at 30% fiber volume (75 MPa), while flexural strength also peaked at 30% substrate (140 MPa). The impact test showed a maximum of 1.84 kJ/m2 at 30% volume fraction. Maximum hardness of 85 RHN is observed for 30% S and 60% E specimens. Weibull distribution plots results, aligned well with the expected distribution pattern, indicating consistent and reliable mechanical behavior. Water absorption rates increase with fiber volume percentage increase, but optimal alkali treatment improves, absorption resistance to some extent. Dynamic mechanical analysis reveals reduced glass transition temperature Tg (97° C) for composite due to their better interaction nature between fiber/silica nanoparticles and matrix. Further characterization reveals thermal stability (374°C), crystalline properties (crystalline index: 56.87%, crystalline size: 21.23 nm), and functional group composition. Numerical analysis using ANSYS validates experimental results, giving confidence in repeatability. Scanning electron microscope analysis confirms good interfacial bonding, crack propagation details, and absence of impurities in the composite. These results like Mechanical properties, thermal stability, crystalline properties, and functional group composition of the composite confirm its suitability for various applications.

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

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

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

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

A design methodology for fibre reinforced concrete elements in serviceability conditions integrating tension softening and stiffening effects

This paper proposes a design methodology to derive an analytical bilinear moment‒curvature diagram (Mana–χana) for the cross-section of fibre reinforced concrete (FRC) elements that also includes conventional steel flexural reinforcement (R/FRC). This bilinear diagram is obtained by determining the post-cracking tensile capacity of FRC (NtcFRC), which integrates not only the tensile stiffening capacity of the FRC surrounding the conventional flexural reinforcement due to the bond stress transference between this reinforcement and FRC, but also the tensile softening of the cracked FRC out of this zone. This Mana–χana is defined by two points, the first corresponding to the cracking moment and its corresponding curvature (Mcrana,χcrana), while the bending moment of the second point of this diagram (Muana) is a multiple of the analytical cracking moment (CuMcrana), where Cu is dependent on the fibre volume percentage (Vf). The curvature corresponding to Muana,χuana, is obtained by assuming the flexural stiffness of a fully cracked RC section. Therefore, the Mana–χana is determined by geometric and material properties of directly assessed by a designer.For demonstrating the applicability of the proposed design methodology, a database of beams of distinct cross-section aspect ratios and compressive strength classes, reinforced with different percentages of steel fibres and reinforcement ratios of conventional steel bars was established. By using the bilinear Mana–χana, and applying the principle of virtual work, the deflection of these beams was estimated with sufficient accuracy for design purposes, when compared to experimental records. Although the formulation has been applied to beams made by steel fibre reinforced concrete (SFRC), it is conceptually general and applicable to elements of concrete reinforced with other types of fibres.

Nonlinear Analysis of Steel Fiber Reinforced Recycled Aggregate Concrete under Compression, Tension, and Elevated Temperatures

In this study, we report on experiments conducted to determine the compressive behaviour of steel fibre reinforced-recycled coarse aggregate concrete (SFRCAC). Many researchers are interested in exploring the utilize of recycled aggregate in concrete for its potential to reduce environmental impact. By using recycled materials in place of natural ones, Recycled Aggregate Concrete (RAC) represents a novel environmentally friendly construction material. Processing waste concrete with a high proportion of building waste yields recycled aggregates. Natural sand & gravel reserves have been drastically depleted, and natural resources used, as a result of the expansion of the construction sector. Fire damage caused by spalling is a major issue when considering the use of such concrete in construction. SFRAC could help with this. In this research, we provide the outcomes of an investigational study into the compressive properties, particularly the compressive strength, of SFRAC cylinders subjected to extreme temperatures. Compressive mechanical characteristics of concrete were studied as a function of temperature (room temperature, 200 ℃, 400 ℃, & 600 ℃) & steel fibre volume percentage (0%, 0.5%, 1%, 1.5%). Adding steel fibres to RAC that has been heated at high temperatures greatly improves its ductility & cracking behaviour, making it more appropriate for usage in building construction since it lessens the likelihood of spalling.

Experimental Investigation on Mechanical and Viscoelastic properties of Kenaf, Basalt and Carbon Fiber reinforced Hybrid Epoxy Polymer Composites

Abstract In this study, a hybrid polymer composite reinforced with natural fibers such as Kenaf and Basalt, as well as carbon fiber was developed and analyzed for mechanical properties of the composite with varying fiber content and orientation. The composites were made using a hand layup process in which the plies were alternately stacked. Further, specimens were cut from the fabricated laminate according to ASTM standards. For the tensile and flexural test was conducted using a Universal Testing Machine (UTM). It is noticed that a hybrid composite made up of both natural fibers and carbon fiber has shown greater strength than a composite made up of only natural fibers with the same volume percentage of fiber. Furthermore, it is observed that the hybrid fiber composite in equal proportion is shown maximized strength.

Viscoelastic modelling and analysis of two-dimensional woven CNT-based multiscale fibre reinforced composite material system

Carbon nanotube (CNT) has fostered research as a promising nanomaterial for a variety of applications due to its exceptional mechanical, optical, and electrical characteristics. The present article proposes a novel and comprehensive micromechanical framework to assess the viscoelastic properties of a multiscale CNT-reinforced two-dimensional (2D) woven hybrid composite. It also focuses on demonstrating the utilisation of the proposed micromechanics in the dynamic analysis of shell structure. First, the detailed constructional attributes of the proposed trans-scale composite material system are described in detail. Then, according to the nature of the constructional feature, mathematical modelling of each constituent phase or building block’s material properties is established to evaluate the homogenised viscoelastic properties of the proposed composite material system. To highlight the novelty of this study, the viscoelastic characteristics of the modified matrix are developed using the micromechanics method of Mori–Tanaka (MT) in combination with the weak viscoelastic interphase (WI) theory. In the entire micromechanical framework, the CNTs are considered to be randomly oriented. The strength of the material (SOM) approach is used to establish mathematical frameworks for the viscoelastic characteristics of yarns, whereas the unit cell method (UCM) is used to determine the viscoelastic properties of the representative unit cell (RUC). Different numerical results have been obtained by varying the CNT composition, interface conditions, agglomeration, carbon fibre volume percentage, excitation frequency, and temperature. The influences of geometrical parameters like yarn thickness, width, and the gap length to yarn width ratio on the viscoelasticity of such composite material systems are also explored. The current study also addresses the issue of resultant anisotropic viscoelastic properties due to the use of dissimilar yarn thickness. The results of this micromechanical analysis provide valuable insights into the viscoelastic properties of the proposed composite material system and suggest its potential applications in vibration damping. To demonstrate the application of developed novel micromechanics in vibration analysis, as one of the main contributions, comprehensive numerical experiments are conducted on a shell panel. The results show a significant reduction in vibration amplitudes compared to traditional composite materials in the frequency response and transient response analyses. To focus on the aspect of micromechanical behaviour on dynamic response and for the purpose of brevity, only linear strain displacement relationships are considered for dynamic analysis. These insights could inform future research and development in the field of composite materials.

Impact of Molding Temperature, Fiber Loading and Chemical Modifications on the Physicomechanical, and Microstructural Morphology Properties of Woven Kenaf Fiber/PLA Composites for Non-Structural Applications

ABSTRACT These days, green composites are getting a lot of attention for their biodegradability, sustainability, and affordability. This study applies polylactic acid as the matrix and untreated and surface-treated kenaf fibers as reinforcement to fabricate kenaf-reinforced PLA-based composites. Kenaf fibers are exposed to three different chemical treatments (sodium hydroxide, potassium permanganate, and potassium dichromate) and investigate the effect of surface modifications on the mechanical properties of kenaf/PLA composites. The surface modified fibers were characterized by FTIR Spectroscopy. The consequences of processing variables such as fiber volume percent ranging from 25% to 50% and molding temperature range of 160°C to 180°C were also examined on the mechanical characteristics of developed composites and are validated using SEM analysis. Surface modifications result in improved tensile and flexural characteristics of developed treated kenaf/PLA composites. Alkali treated woven kenaf fiber composites with greater matrix adhesion have optimum tensile and flexural strength of 72.81 MPa and 94.45 MPa respectively. The present study revealed that composites (fabricated at 170°C molding temperature) have maximal tensile and flexural strength at 35% fiber volume fraction.

Karakteristik komposit sandwich dengan inti (core) open cell foam bambu berlubang

The sandwich composite employed in this study is made of bamboo open-cell foam with plywood skin. The fibre volume percentage in the bamboo foam core was 15%, and PVAc glue was used. The open-cell foam core has a square-shaped hollow in the centre with spacings of 30mm, 40mm, and 60mm. The goal of this study is to describe sandwich composites made using hollow bamboo open-cell foam cores. Density testing (ASTM C271), flatwise compression testing (ASTM C365-05), flexural testing (ASTM C393), and water absorption testing (ASTM C272) were among the tests performed. Sandwich composites with core-opened cell foam with holes had lower average density, specific flatwise compressive strength, and specific bending strength than sandwich composites without holes, according to the study's findings. The average density of the sandwich composite with core-opened cell foam with holes dropped by 6-13% as compared to the sandwich composite without holes. The average-specific flatwise compressive strength of the sandwich composite with a hollow core decreased by 2-20%. The sandwich composite's average specific bending strength was reduced by 40-50% when the core-opened cell foam with holes was used. The percentage of water absorption in the sandwich composite is the inverse. With this feature, it is believed that hollow bamboo open-cell foam would become more widely used.

Influence of nano-coated micro steel fibers on mechanical and self-healing properties of 3D printable concrete using graphene oxide and polyvinyl alcohol

High ductility cementitious composite is one of the proposed new generations of concrete for use in 3D concrete printing with a large dosage of microfibers. This large volume of fibers negatively affects printed layers’ fresh properties and durability. It also increases the porosity of concrete and is not cost-effective. Accordingly, through an experimental program, this article introduces a novel coating technique to reduce the required quantity of fibers for 3D concrete printing. Polyvinyl alcohol (PVA) is used in the present study to help in coating graphene oxide (GO) nanomaterials on the surface of micro steel fibers. Compressive, direct tensile, and bending tests are considered for the mechanical properties. The self-healing property of the proposed mixture is also checked by applying pre-loading on direct tension and bending samples and followingly putting for the healing period. The results show that the nano-coating method improves the compressive and direct tensile strength of cement mortar so that this technique can be used to reduce the volume percentage of steel fibers to achieve the same mechanical characteristics. Also, promising findings were obtained for the self-healing properties of cementitious composites containing nano-coated fibers.

Mechanical and durability performance of concrete with recycled tire steel fibers

The increasing waste tire disposal and the related environmental pollution have led to the further exploration of utilizing recycled-tire steel fiber (RTSF) to replace industrial steel fiber (ISF) for better cost-effective concrete production. This study compares the workability, mechanical properties, and durability of RTSF-reinforced concrete (RSC) to those of commercial ISF-reinforced concrete (ISC). Plain concrete samples, ISC samples named IS05 and IS05R (with 0.5% of ISF by volume), and RSC samples named RS05, RS10, and RS15 with three-volume percentages of RTSF (0.5%, 1.0%, and 1.5%) were prepared accordingly. The results show that RSC has better flowability than ISC when adding the same volume percentage of fibers. In terms of mechanical properties, the addition of RTSF slightly increases the 28-day compressive strength. The splitting tensile strength is also increased by up to 15.4% with the added RTSF, which is very close to the ISF (16.9%). Regarding flexural performance, RS15 samples show a very close enhancing effect to IS05 samples with enlarged residual strength and fracture energy. The ultrasonic pulse velocity test results also indicate that both RTSF and ISF slightly increase the concrete modulus. In terms of durability, RS10 samples reduce drying shrinkage by up to 9.2%, which is better than IS05 samples (6.3%). RTSF also improves the freeze–thaw resistance by reducing the change percentage of relative dynamic modulus and increasing the durability factor by up to 4.6%. Overall, the RTSFs in concrete have a slightly lower mechanical reinforcement and better workability by comparing with one type of thin ISFs. These findings can facilitate the usage of RTSF in concrete mixes as mechanical reinforcements and provide another market for waste tire fiber recycling.

Experimental Analysis of Fiber Reinforcement Rings' Effect on Tensile and Flexural Properties of Onyx™-Kevlar® Composites Manufactured by Continuous Fiber Reinforcement.

Additive manufacturing of composite materials is progressing in the world of 3D printing technologies; composite materials allow the combination of the physical and mechanical properties of two or more constituents to create a new material that meets the required properties of several applications. In this research, the impact of adding Kevlar® reinforcement rings on the tensile and flexural properties of the Onyx™ (nylon with carbon fibers) matrix was analyzed. Parameters such as infill type, infill density and fiber volume percentage were controlled to determine the mechanical response in tensile and flexural tests of the additive manufactured composites. The tested composites showed an increment of four times the tensile modulus and 1.4 times the flexural modulus of pure Onyx™ matrix when compared with that of the Onyx™-Kevlar®. The experimental measurements demonstrated that Kevlar® reinforcement rings can increase the tensile and flexural modulus of Onyx™-Kevlar® composites using low fiber volume percentages (lower than 19% in both samples) and 50% of rectangular infill density. However, the appearance of some defects, such as delamination, was observed and should be further analyzed to obtain products that are errorless and can be reliable for real functions as in automotive or aeronautical industries.

Exploring the dynamic fracture performance of epoxy/cement based piezoelectric composites with complex interfaces

Dynamic intensity factors (IFs) are the key parameters in comprehending and forecasting dynamic fracture behavior of piezoelectric composites. A domain-independent interaction integral (DII-integral) is developed to extract the dynamic stress intensity factors (SIFs) and electric displacement intensity factor (EDIF). The DII-integral is theoretically proved that there is no need to consider the electromechanical material derivatives and complicated material interfaces have no effect on the application of the method. Evaluating the results with the published data yields a good agreement and good domain-independence of the proposed I-integral is checked for multi-interface piezoelectric composites. The numerical simulations show that the amplitudes of the dynamic IFs decrease as the size of piezoelectric particle increases and crack damage is prevented as the number of piezoelectric particles increases. The peak values of the dynamic IFs are not monotonically related to the distance between the particles due to the superposition of elastic waves. The dynamic IFs increase when the volume percentage of piezoelectric fiber rises, while the opposite change is observed in laminated composites. Generally, the dynamic IFs of fiber-reinforced composites are smaller (larger) than that of laminated composites when the volume fraction of piezoelectric ceramics is higher (lower) than 40 percent.

Redox cationic frontal polymerization: a new strategy towards fast and efficient curing of defect-free fiber reinforced polymer composites.

Frontal polymerization of epoxy-based thermosets is a promising curing technique for the production of carbon fiber reinforced composites (CFRCs). It exploits the exothermicity of polymerization reactions to convert liquid monomers to a solid 3D network. A self-sustaining curing reaction is triggered by heat or UV-radiation, resulting in a localized thermal reaction zone that propagates through the resin formulation. To date, frontal polymerization is limited to CFRCs with a low fiber volume percent as heat losses compromise on the propagation of the heat front, which is crucial for this autocatalytic curing mechanism. In addition, the choice of suitable epoxy monomers and thermal radical initiators is limited, as highly reactive cycloaliphatic epoxies as well as peroxides decarboxylate during radical induced cationic frontal polymerization. The resulting networks suffer from high defect rates and inferior mechanical properties. Herein, we overcome these shortcomings by introducing redox cationic frontal polymerization (RCFP) as a new frontal curing concept. In the first part of this study, the influence of stannous octoate (reducing agent) was studied on a frontally cured bisphenol A diglycidyl ether resin and mechanical and thermal properties were compared to a conventional anhydride cured counterpart. In a subsequent step, a quasi-isotropic CFRC with a fiber volume of >50 vol%, was successfully cured via RCFP. The composite exhibited a glass transition temperature > 100 °C and a low number of defects. Finally, it was demonstrated that the redox agent effectively prevents decarboxylation during frontal polymerization of a cycloaliphatic epoxy, demonstrating the versatility of RCFP in future applications.

Mechanical Properties of Fly Ash-Based Geopolymer Concrete Incorporation Nylon66 Fiber.

This study was carried out to investigate the effect of the diamond-shaped Interlocking Chain Plastic Bead (ICPB) on fiber-reinforced fly ash-based geopolymer concrete. In this study, geopolymer concrete was produced using fly ash, NaOH, silicate, aggregate, and nylon66 fibers. Characterization of fly ash-based geopolymers (FGP) and fly ash-based geopolymer concrete (FRGPC) included chemical composition via XRF, functional group analysis via FTIR, compressive strength determination, flexural strength, density, slump test, and water absorption. The percentage of fiber volume added to FRGPC and FGP varied from 0% to 0.5%, and 1.5% to 2.0%. From the results obtained, it was found that ICBP fiber led to a negative result for FGP at 28 days but showed a better performance in FRGPC reinforced fiber at 28 and 90 days compared to plain geopolymer concrete. Meanwhile, NFRPGC showed that the optimum result was obtained with 0.5% of fiber addition due to the compressive strength performance at 28 days and 90 days, which were 67.7 MPa and 970.13 MPa, respectively. Similar results were observed for flexural strength, where 0.5% fiber addition resulted in the highest strength at 28 and 90 days (4.43 MPa and 4.99 MPa, respectively), and the strength performance began to decline after 0.5% fiber addition. According to the results of the slump test, an increase in fiber addition decreases the workability of geopolymer concrete. Density and water absorption, however, increase proportionally with the amount of fiber added. Therefore, diamond-shaped ICPB fiber in geopolymer concrete exhibits superior compressive and flexural strength.

The effect of sulfuric acid attack on mechanical properties of steel fiber-reinforced concrete containing waste nylon aggregates: Experiments and RSM-based optimization

Replacing natural aggregate with recycled plastic has been a strategy to reduce pollution associated with conventional concrete production and disposal of plastic materials. Due to the possibility of structures subject to acid attacks, it is of value to check the resistance of concrete against these attacks. The present study evaluates the behavior of concrete containing steel fibers and nylon granules under sulfuric acid attack. 9 batches of concrete containing 0, 10, and 20% (by volume) of nylon granules, replacing natural sand and three volume percentage of steel fibers (0, 0.75, and 1.25%) were prepared. First, concretes were placed in a 5% sulfuric acid solution for 0, 45, and 90 days, and then their ultrasonic pulse velocity (UPV) and compressive capacity were evaluated. The microstructural behavior of concretes was also investigated through scanning electron microscopy (SEM) and energy dispersive X-ray microanalysis (EDXMA). Finally, a model using the response surface method (RSM) was proposed to optimize the content of steel fibers and nylon granules in concrete to achieve the maximum strength of concrete in an acidic environment. The results show that increasing the acid exposure time decreases the compressive capacity and UPV of concrete. Concrete with a higher nylon granule content exhibits a lower strength and UPV decline rate due to acid immersion when compared to that with a lower nylon granule content. After optimization, it was found that the optimal volume percentage of steel fibers and nylon granules in concrete after 90 days of acid exposure is 0.11% and 20% to maximize the compressive strength, respectively. The findings of this study help to minimize the extraction of non-renewable natural resources and the environmental impact of waste nylons by developing cleaner and more sustainable concrete.

Data-Driven Techniques for Evaluating the Mechanical Strength and Raw Material Effects of Steel Fiber-Reinforced Concrete.

Estimating concrete properties using soft computing techniques has been shown to be a time and cost-efficient method in the construction industry. Thus, for the prediction of steel fiber-reinforced concrete (SFRC) strength under compressive and flexural loads, the current research employed advanced and effective soft computing techniques. In the current study, a single machine learning method known as multiple-layer perceptron neural network (MLPNN) and ensembled machine learning models known as MLPNN-adaptive boosting and MLPNN-bagging are used for this purpose. Water; cement; fine aggregate (FA); coarse aggregate (CA); super-plasticizer (SP); silica fume; and steel fiber volume percent (Vf SF), length (mm), and diameter were the factors considered (mm). This study also employed statistical analysis such as determination coefficient (R2), root mean square error (RMSE), and mean absolute error (MAE) to assess the performance of the algorithms. It was determined that the MLPNN-AdaBoost method is suitable for forecasting SFRC compressive and flexural strengths. The MLPNN technique’s higher R2, i.e., 0.94 and 0.95 for flexural and compressive strength, respectively, and lower error values result in more precision than other methods with lower R2 values. SHAP analysis demonstrated that the volume of cement and steel fibers have the greatest feature values for SFRC’s compressive and flexural strengths, respectively.

Mechanical behavior of steel-fiber-reinforced self-stressing concrete filled steel tube columns subjected to eccentric loading

Initial self-stress contributes to the pre-peak properties of concrete filled steel tube (CFST) columns, but brings salient brittleness at the post-peak stage. Adding steel fibers can alleviate the friability of concrete, helpful in the post-peak behavior of CFST columns. This study aims to investigate the coupling effect of initial self-stress and steel fibers on the mechanical behavior of CFST columns under eccentric loads. 42 eccentrically loaded specimens are conducted with various levels of self-stress, eccentricity ratio, steel fiber volume percentage, concrete strength grade and steel tube thickness. Moreover, a numerical analysis model is developed to capture the eccentrically loaded behavior of steel-fiber-reinforced self-stressing concrete filled steel tube (SSCFST) columns. The results show that the increases in the ultimate load (Nu) and the corresponding bending moment (Mu) are obtained by the self-stress. Adding steel fibers leads to a slight growth of Nu, but the bending moment shows an obvious growth after the ultimate state, indicating adequate safety margin. The axial-flexural interaction curves possess a more obvious convexity as steel fiber dosage is increased. Based on the numerical results, a new axial-flexural interaction model is proposed, which is capable of considering the influence of steel fiber dosage.

Maximum Bending Stress Analysis of Jute/Epoxy and Glass/Epoxy Polymer Composites

A surge inthe use of fibre reinforcedcomposites for biodegradable materials, which include both synthetic and natural fibres, to fulfil the strength requirements of composites while also being environmentally friendly has resulted in the use of these materials becoming increasingly popular. Researchers have been working to improve natural fibre qualities to partially replace synthetic fibre, even though not entirely. The research can be accomplished by modelling and simulation techniques, which are becoming more prevalent as technology advances. The approaches have the benefits of being efficient in addressing any material model, boundary conditions, and complicated form structure that may be encountered. This study uses ANSYS APDL, a finite element analysis tool, to carry out flexural test. These factors, as well as the fibre ply orientation, lay-up sequence, and fibre volume percentage, have an impact on the maximum stress of each composite, which are investigated in this study. In the lay-up sequence of [(+θ, -θ)2] s, with fibre ply orientation of 0 ̊ the maximum flexural stress obtains for glass/epoxy (vf=60%), glass epoxy (vf=30%), and jute/epoxy (vf=30%) is 214.64 MPa, 153.77 MPa, and 82.91 MPa and for fibre ply orientation of 90 ̊ the maximum bending stress is 55.41 MPa, 18.39 MPa and 8.37 MPa respectively. Furthermore, the impact of off-axis plies in the 0° fibre ply orientation can be observed in the maximum bending stress of the [θ4,04] s lay-up sequence, which is a function of the number of off-axis plies in the 0° fibre ply orientation. When using the lay-up sequence [904,04]s, the maximum flexural stress for glass/epoxy (vf=60%), glass/epoxy (vf=30%), and jute/epoxy (vf=30%) is 83.39 MPa, 23.04 MPa, and 17.92 MPa, respectively. When bending tests are performed, the 0° fibre ply orientation produces the highest maximum stress, followed by 45° and 90°. When comparing 0° plies composites with off-axis angles to plies composites, the lay-up sequence of 0° plies with off-axis angles exhibits the highest maximum stress.