Increasing Fiber Volume Fraction Research Articles

PENGARUH KEKUATAN IMPAK DAN TARIK KOMPOSIT BERPENGUAT SERAT SEMBUKAN DENGAN MATRIK EPOXY

Composite is a combination of two or more elements arranged in a certain way to get new properties in matrial. Plants of Pukan (Peaderiafoetida L.) is a kind of wild grass that spreads and grows wild in nature. This study aims to determine the effect of the mechanical strength of the composite reinforced dying in the Healing with epoxy matrix. In this test, using Sembukan fiber as a reinforcement and epoxy as a composite matrial adhesive. The tests include: Tensile tests referring to ASTMD 3039, and Impact Tests referring to ASTMD 256. These tests use fiber volume fractions of 20%, 30%, and 40% with woven fiber orientation. The results showed, the greater the fiber volume fraction, the greater the toughness, the highest toughness was found in the fiber volume fraction variance of 40%, amounting to 0.10396 J/mm2. Same as Tensile testing, the stress increases with increasing fiber volume fraction, ie at 40% fiber at 9,1596 MPa. The influencing factor is none other than the percentage of fibers in the composite increasing the mechanical strength of the matrix. Keywords: Fiber Heal, toughness Impact, Tensile strength.

Micromechanics stiffness upscaling of plant fiber-reinforced composites

Fiber-reinforced green composites made from natural plant fibers are an increasingly popular sustainable alternative to conventional high-performance composite materials. Given the variety of natural fibers themselves, and the even larger variety of possible composites with specific fiber dosage, fiber orientation distribution, fiber length distribution, and fiber-matrix bond characteristics, micromechanics-based modeling is essential for characterizing the macroscopic response of these composites. Herein, an analytical multiscale micromechanics model for elastic homogenization is developed, capable of capturing the this variety. The model features (i) a nanoscopic representation of the natural fibers to predict the fiber stiffness from the universal stiffness of the fiber constituents, mainly cellulose, (ii) a spring-interface model to quantify the compliance of the fiber-matrix bond, and (iii) the ability to model any (and any combination of) orientation distribution and aspect ratio distribution. Validation is performed by comparing the predicted stiffness to experimental results for as many as 73 composites available in the literature. Extensive sensitivity analyses quantify the composite stiffening upon increasing fiber volume fraction, fiber alignment, fiber length, and fiber-matrix interface stiffness, respectively.

Compressive performance and analytical modeling of early strength seawater sea sand engineered cementitious composites

Early strength seawater and sea sand engineered cementitious composites (ESSECC) are novel fiber-reinforced cementitious composites that exhibit strain-hardening behavior and a high early strength. The compressive properties of ESSECC with different polyvinyl alcohol (PVA) fiber content, carbon nanotubes (CNTs) content, and water–binder ratios were investigated at different curing ages in this study. Experimental evaluations were conducted to assess compressive strength, elastic modulus, Poisson's ratio, peak strain, energy dissipation capacity, toughness index, and stress-strain curves. The experimental results showed that early strength of ESSECC reached 58.0 %, 81.6 %, and 86.7 % of its 28-day compressive strength after 2 h, 3 days, and 7 days of curing, respectively. An increase in the PVA fiber volume fraction from 0 to 2 % resulted in a 32.8 % increase in average peak strain. Incorporating 0.15 % CNTs into ESSECC led to an average enhancement of compressive strength by 7.2 %. Based on these experimental results, an analytical model considering the effects of curing age and the addition of PVA fibers and CNTs was developed to describe the compressive stress–strain behavior of ESSECC. This model showed strong consistency with the experimental results.

Effect of Fiber Orientation and Volume Fraction on Young's Modulus for Unidirectional Carbon Fiber Reinforced Composites: A Numerical Investigation

The modulus of elasticity of unidirectional fiber-reinforced composites greatly depends on the fiber orientation and the fiber volume fraction. This paper investigates the effects of fiber orientation and fiber volume fraction using the commercially available Finite Element Analysis (FEA) software Abaqus. Carbon fiber is the reinforcing material, while epoxy is used as the matrix. Representative Volume Element (RVE) of the unidirectional carbon fiber reinforced composites are modeled in Abaqus, and the unidirectional tensile test is simulated to determine the modulus of elasticity for different fiber orientations and fiber volume fractions. The numerical results are verified by previously published results and by experimental results. It is found that the modulus of elasticity of the composite is maximum when the fiber inclination angle is 0°, i.e., the fibers are placed along the loading direction. As the fiber orientation angle increases, the modulus of elasticity also decreases and is almost constant after 45°. A linear increase in modulus of elasticity is observed for an increase in fiber volume fraction. This model will help the researcher to select the appropriate fiber orientation and volume fraction for a specific application.

Toughness of Natural Hydraulic Lime Fibre-Reinforced Mortars for Masonry Strengthening Overlay Systems

Masonry structures are susceptible to damage and collapse due to seismic actions, a problem in many urban areas. To address this issue, researchers are studying the use of fibre-reinforced mortars as overlay strengthening systems. This study assessed the use of synthetic polyacrylonitrile (PAN) fibres as reinforcement of natural hydraulic lime mortar, focusing on their influence on fresh behaviour and mechanical properties. Natural hydraulic lime (NHL) was chosen for its compatibility with typical older ceramic and natural stone structural masonry and contemporary ceramic brick infill masonry substrates, as well as for the sustainability benefits. The study also assessed the contribution of the PAN fibres to toughness enhancement in the developed formulations. The fresh behaviour of fibre-reinforced mortar (FRM) was found to be adequate for applications with fibre volume fractions below 0.50%. The compressive and flexural strengths were affected differently by the increase in fibre volume fraction, with compressive strength decreasing and flexural strength increasing. The maximum compressive strength of 13.3 MPa was obtained for 0.25% of fibres, while for flexural strength a maximum of 6.70 MPa was achieved with 1.00% of fibres. The compressive and flexural toughness, related to the post-cracking responses, increased with the fibre fraction, and even for fractions as low as 0.25%, an important increment of the capacity to dissipate energy was achieved.

Experimental study of the bond behavior of 400MPa grade hot-rolled ribbed steel bars in steel fibre reinforced concrete.

Present studies show that steel fibres can improve the bond of steel bar in steel fibre reinforced concrete (SFRC) with a correlation to the fibre factor and the fibre distribution uniformity. As a foundation of high-flowability SFRC working together with 400MPa grade hot-rolled ribbed (HRB400) steel bar in reinforced structures, the bond between them was evaluated through a series of pull-out testing on 48 specimens with a central arranged steel bar. The bond behaviours of steel bar were estimated with a constant bond length of 5d (d is the diameter of steel bar) embedded in high-flowability SFRC, the main research parameters included the ingot mill steel fibres with a fibre volume fraction varied from 0.8 to 2.0%, the strength grade C40 and C50 of SFRC or referenced conventional concrete, and the diameter of steel bars varied from 14 to 20 mm. Results showed that the high-flowability SFRC compacted with a slight vibration is beneficial to improve the bond failure pattern since steel fibres effectively eliminate the crack appeared on the SFRC blocks during the pulling out of steel bar, leading to all specimens failed with the steel bar pull out of SFRC blocks. The bond strength was dominant by the SFRC strength, and obviously strengthened with the increase of fibre volume fraction, while the peak-slip was slightly influenced by the diameter of steel bar. By conducting analyses of test data, equations for calculating the bond strength and the peak-slip are proposed accounting for the effect of steel fibres. Then the predicting method for the anchorage length is suggested linking with different design codes for concrete structures. Compared with test results of this study, a little shorter anchorage length of steel bar in SFRC is obtained from the specification of Chinese code JGJ/T46, which should be noticed to ensure a rational anchorage of ribbed steel bar in SFRC with ingot mill steel fibres.

Analysing the Influence of Fibers on Fresh Concrete Rheometry by the Use of Numerical Simulation

Measuring the flow properties of fiber-laden fresh concrete poses a substantial challenge because not only the fraction of fibers but also their orientation process during the measurement influence the measured quantities. Numerical simulations of the flow in a ball probe rheometer are used to determine the fiber orientation process during the measurement of the flow properties and its influence on the measured variables. Through analytical considerations and comparison with measurement results, it can be shown that the constitutive law applied can reproduce the real flow behavior very well, taking the fiber orientation into account. At the same time, it is investigated why no orientation influence on the torque is recognizable in the experimental measurement curves, although the orientation process demonstrably exceeds the duration of the measurement process. The results show that fluid inertia is overcome before the recognizable onset of fiber orientation, and the spatially inhomogeneous flow minimises the impact of the orientation process on torque. The simulation model aligns well with experimental outcomes, indicating a linear increase in effective viscosity with increasing fiber volume fraction. The findings can be used to accurately measure the objective material parameters of the orientation-considering constitutive law using ball probe rheometers, so that an accurate prediction of the flow process of fresh concrete with fibers is made possible, for example for the simulation of formwork fillings.

Analysis of transverse thermal conductivity for mesophase pitch-based carbon fibers and the through-thickness heat conduction of their composites

A quantitative analysis method for the transverse thermal conductivity (TC) of carbon fiber is developed, which consists of three steps including TC and morphology characterization of unidirectional composite laminate, fiber contour extraction, and finite element inverse analysis. Two different pitch-based carbon fibers with folded-radial and onion-skin microstructure are characterized, and the influences of fiber volume fraction and microstructure on the heat conduction of their composites are investigated. The equivalent transverse TCs of TC–HC–800 and PCF-1 carbon fibers are measured to be 9.27 and 2.87 W m−1 K−1, respectively. The through-thickness TC of unidirectional composite exhibits rapid growth with the increase in fiber volume fraction. The finite element analysis reveals that more continuous heat conduction paths are formed with the increase in fiber volume fraction. Benefited from the bigger graphitization degree, larger cross-sectional area, and bigger aspect ratio, TC–HC–800 unidirectional composite shows higher through-thickness TC than PCF-1 composite at the same fiber volume fraction.

Void formation and suppression in CFRP laminate using newly designed ultrasonic vibration assisted RTM technique

This study introduces an ultrasonic vibration assisted resin transfer molding (RTM) technique as an innovative approach to address the inherent challenges associated with traditional methods for producing CFRP laminates. It investigates the mechanism of void formation in CFRP composites under ultrasonic vibration using 3D X-ray microscopy. Numerical calculations and simulation analyses are also employed to validate the impact of ultrasonic vibration on mechanical properties of CFRP. The findings indicate that ultrasonic vibration results in CFRP laminates with more uniform thickness, leading to a substantial increase in fiber volume fraction up to ∼16 %. Concurrently, there are significant improvements in flexural strength (∼20 %) and fracture energy (∼90 %). Ultrasonic vibration also effectively reduces CFRP porosity by at least 25 %, resulting in a more consistent distribution of voids, primarily consisting of small circular voids. This porosity reduction is attributed to the cavitation effect and enhancing wettability, consequently improving the mechanical properties of CFRP. Moreover, simulations and numerical calculations demonstrate the significant occurrence of cavitation effect within the resin under specific process conditions. The intensity of cavitation is influenced by factors such as the initial bubble radius, acoustic pressure amplitude, and static pressure of the resin. The ultrasonic-assisted RTM process is proved as a promising method for producing CFRP laminates with superior properties.

Simulation Analysis of Composite Axial Tensile Failure Considering Fiber Strength Dispersion

The axial strength limit of composites exhibits obvious dispersed characteristics. Based on the finite element simulation, using the Weibull distribution to describe the fiber strength, and considering the random distribution of fibers within the matrix, a representative volume element of composites was established in this article. The axial tensile failure of T300/BSL914C composites was studied and the effects of fiber tensile strength and volume fraction on the axial tensile strength of composites were analyzed. Results show that considering the influence of fiber strength dispersion, the fracture of fiber bundles exhibits a progressive failure during the composite tensile failure process, and before the fiber fracture, the interface is not subjected to stress. Axial tensile strength increases linearly with the increase of fiber tensile strength and volume fraction. The composite axial tensile strength could be improved by selecting high-strength fibers or increasing fiber volume fraction.

Effect of fiber section shape and volume fraction on the mechanical properties of steel-fiber reinforced concretes

This study presents the preparation of steel-fiber reinforced concretes (SFRCs) using straight navicular fibers with annular-sector-shaped sections and corrugated fiber with rectangular-shaped sections, respectively. The flexural and splitting tensile strengths of both the respective SFRCs increase with increasing fiber volume fraction, whereas their compressive strengths initially increase, then decrease, and then increase again. For the same fiber volume fraction, the mechanical properties of the navicular fiber-reinforced concrete are superior to those of the corrugated fiber-reinforced concretes. The introduction of steel fiber changes the failure mode of the plain concrete during bending from a typical brittle mode to a bimodal ductile failure mode. As compared to the corrugated fiber, the navicular fiber has stronger interface bonding to concrete and a higher friction resistance to fiber sliding and subsequent pullout. Furthermore, navicular fiber has a higher load-bearing capacity, which makes it more favorable for improving the mechanical properties of plain concrete.

Flexural behavior of high-strength steel bar reinforced UHPC beams with considering restrained shrinkage

Despite the excellent mechanical properties of ultra-high performance concrete (UHPC), UHPC beams with a conventional reinforcement ratio consistently demonstrate limited ductility. Therefore, this study aims to enhance the ductility of reinforced UHPC beams by regulating the tensile interaction between steel fibers and reinforcement. Six UHPC beams with varying fiber volume fractions and reinforcement ratios were tested under flexure. The effect of restrained shrinkage on flexural behavior was emphatically investigated. A cracked section analysis was also implemented to predict cracking behaviors of UHPC beams and was verified by experimental results. The test results revealed an increase in the ductility of UHPC beams with an increasing reinforcement ratio, while a decrease was observed with an increasing fiber volume fraction. The contribution of UHPC tensile capacity decreased significantly with the increase in the reinforcement ratio because of the restrained shrinkage. The stiffness and crack control capacity of reinforced UHPC beams reaches a plateau when the sum of reinforcement ratio and fiber volume fraction exceeds 3.1%. Increasing the fiber content is more effective than increasing the reinforcement ratio in limiting crack development, whereas the converse is true for improving the flexural capacity.

High‐velocity impact resistance and energy absorption behavior of Carbon‐Kevlar hybrid composite laminates

AbstractThis study investigated the high‐velocity impact behavior of composite plates with different hybrid ratios and structural configurations through experimental and numerical simulation studies. The results showed that the critical penetration velocity of the composite plate generally increases with an increase in the volume fraction of aramid fibers. The high‐velocity impact finite element model developed in this study accurately simulated the high‐velocity impact behavior of laminated fiber composite plates with various hybrid ratios and different structures. The impact failure patterns of the plates were analyzed, and it was observed that the carbon fibers on the back face were prone to tensile fracture, followed by the gradual fracture of aramid fibers. The numerical simulation results show significant differences in residual impact velocity and energy absorption when impacted from different sides and the impact from the aramid side resulted in better energy absorption, which is contrary to the findings in many existing research papers. These findings provide valuable insights into the impact resistance of composite materials and can guide the design and development of high‐performance composite structures for aero‐engine case designing.Highlights The high‐velocity impact behavior of C/K fiber epoxy resin matrix composite laminates are studied. The critical penetration velocity increases with the increase of aramid fiber volume fraction. The laminate absorbs most of the impact energy during the instantaneous impact time. Energy absorption ability is better when the impact surface is aramid fibers. Carbon fibers on the back side of the laminate are more prone to tensile fracture.

Energy evolution characteristics of engineered cementitious composites (ECC) under tensile and compressive loading

To more truly reflect the failure law of engineered cementitious composites (ECC), this research investigates the multiple cracking and failure process of ECC from the perspective of energy and reveals the energy evolution characteristics of this process. The mechanical properties and energy evolution characteristics of ECC under different water-binder ratios were studied by uniaxial compression test. The effects of water-binder ratios, fiber volume fractions, and fiber aspect ratio on the tensile properties, energy evolution characteristics, and fracture energy of ECC were systematically investigated. It was found that the increase in the water-binder ratios decreases the compressive strength and elastic strain energy release rate, but increases the dissipated energy. The increase of fiber volume fraction and fiber aspect ratio can effectively improve the tensile properties, elastic strain energy, dissipated energy, and fracture energy. The abrupt change in the elastic energy consumption ratio can be used as a criterion for ECC failure.

Mechanical characterization of high-strength carbon-epoxy composite laminates

High-strength carbon/epoxy composites (HSCEC) are known to exhibit comparably high specific strength and stiffness than high-strength steel alloys. Consequently, they have a range of applications in the automotive, aerospace, and ship-building industries But extensive studies on the mechanical properties of HSCECs, especially at the laminate level, are lacking in the literature. This study characterizes the tensile and compressive properties of HSCEC laminates with various uni-directional (UD) and bi-directional (BD) ply sequences. The ply sequence that best combines specific strength and modulus is identified. The effects of fiber volume fraction on load–displacement behavior are analyzed. An increase in the fiber volume fraction increases the stiffness and strength of the laminate but decreases its failure strain. Overall, this study highlights the sensitivity of the specific modulus, specific strength, and percentage elongation of the composite laminates to the stacking sequence and fiber volume fraction.

Effect of mold on curing deformation of resin transfer molding‐made textile composites

AbstractIn the process of preparing textile composites by resin transfer molding (RTM) method, both the upper and lower surface of the mold will interact with the composite parts due to the mismatch of thermal expansion coefficient between the mold and the part, resulting in warpage deformation. To address this key technical problem, this article first studied the effect of mold on the warpage deformation of composite material under different fiber volume fractions. Then a mold–part interaction modeling method for RTM process with nonthermoelastic deformation is proposed. By introducing shear layers between the upper and lower surfaces of the mold and the composite part, a finite element simulation model for predicting the curing deformation of the component is established and experimentally verified. The results show that the effect of mold–part interaction on the warpage deformation of the composite decreases with increasing fiber volume fraction. Meanwhile, the proposed modeling method can avoid complete material characterization, and the comparison between experimental and simulation results proves that the model can accurately simulate the curing deformation of composite components under the same process conditions. Finally, the analysis reveals that the interaction caused by thermal mismatch between the composites and the mold is less related to the intermediate layup, but mainly related to the fiber orientation of the layup layer in contact with the mold.Highlights The warpage deformation law of the mold on the composites with different fiber volume fractions is investigated. A mold–part interaction modeling method for a resin transfer molding process with nonthermoelastic deformation is proposed, where the mold stretching effect is represented by the cumulative effect of the interaction between the two layers on the upper and lower surfaces of the part.

Microstructure and mechanical properties of tungsten fiber reinforced tungsten composites prepared by Fe activated sintering

Tungsten fiber reinforced tungsten composites were fabricated by Fe activated sintering. The effect of Fe content (0.5% ∼ 1.0%(wt%)) and original fiber volume fraction (10% ∼ 50%(vol%)) on relative density, microstructure and mechanical properties were studied. The interaction between the Fe and tungsten fiber was analyzed. The fracture behavior as well as the strengthening and toughening mechanisms were revealed. The results indicated that the Fe not only promoted the sintering densification of the tungsten matrix, but also caused the recrystallization of tungsten fiber from the surface to the center due to the element diffusion. The (i) relative density, (ii) residual fiber diameter (or residual fiber volume fraction) and (iii) flexural strength were (i) increased, (ii) decreased and (iii) increased with Fe content increased, respectively, while were (i) decreased, and (ii, iii) first increased and then decreased with the original fiber volume fraction increased, respectively. As for the composites containing 1.0%Fe, the fracture toughness was monotonically increased with the increase of the original fiber volume fraction. The fracture mode of the matrix was intergranular. The strength and toughness of the composites were enhanced as a result of fiber fracture, crack deflection, interface debonding, and fiber pull-out.

Experimental study on bonding performance of polypropylene fiber modified rubber concrete and deformed steel bar

In order to study the binding properties of deformed steel rods and rubber concrete modified with polypropylene fiber, four groups of bonding specimens were designed with polypropylene fiber volume ratio as a variable. The effect of polypropylene fiber on bond strength and bond slip curve was investigated by drawing test. It was found that the bond strength increased with the increase of polypropylene fiber volume fraction in the range of 0 ~ 1.5 %. Based on the experimental data, the constitutive relationship between deformed steel bar and polypropylene fiber modified rubber concrete was established. It provides a theoretical basis for further research on polypropylene fiber modified rubber concrete.

Mechanical Properties and Crack Resistance of Basalt Fiber Self-Compacting High Strength Concrete: An Experimental Study.

Pure self-compacting concrete has many disadvantages, such as early shrinkage and cracking. The addition of fibers can effectively improve the properties of resistance to tension and cracking of self-compacting concrete, thereby the effect of improving its strength and toughness can be achieved. Basalt fiber is a "new green industrial material" that has unique advantages, such as high crack resistance and being lightweight compared with other fiber materials. In order to study the mechanical properties and crack resistance of basalt fiber self-compacting high-strength concrete intensively, the self-compacting high-strength concrete of C50 was designed and obtained using the absolute volume method with multiple proportions. Orthogonal experimental methods were used to study the influence of the water binder ratio, fiber volume fraction, fiber length, and fly ash content on the mechanical properties of the basalt fiber self-compacting high-strength concrete. Meanwhile, the efficiency coefficient method was used to determine the best experiment plan (water binder ratio 0.3, fiber volume ratio 0.2%, fiber length 12 mm, fly ash content 30%), and the effect of fiber volume fraction and fiber length on the crack resistance of the self-compacting high-performance concrete was investigated using improved plate confinement experiments. The results show that (1) the water binder ratio had the greatest impact on the compressive strength of basalt fiber self-compacting high-strength concrete, and as the fiber volume fraction increased, the splitting tensile strength and flexural strength both increased; (2) there was an optimal value for the effect of the fiber length on the mechanical properties; (3) with the increase in fiber volume fraction, the total crack area of the fiber self-compacting high-strength concrete significantly decreased. When the fiber length increased, the maximum crack width first decreased and then slowly increased. The best crack resistance effect was achieved when the fiber volume fraction was 0.3% and the fiber length was 12 mm. Therefore, basalt fiber self-compacting high-strength concrete can be widely used in engineering fields, such as national defense construction, transportation, and building structure reinforcement and repair, due to its excellent mechanical and crack resistance properties.

Design and fabrication of high-performance 3D printed continuous flax fibre/PLA composites

The mechanical properties of 3D-printed continuous plant fibre-reinforced poly(lactic) acid (PLA) composites are insufficient due to the low fibre volume fraction (∼30 %). Further increase of fibre volume fraction of composites by reducing the line width may result in a composite with low fibre impregnation degree or the clogging of printer nozzle because of the twisted nature and uneven diameter of plant yarns, which also degrades the mechanical properties. This study proposed a method to obtain 3D printed continuous flax fibre reinforced composites (CFFRCs) with a high fibre volume fraction and excellent mechanical performance by statistical analysis of the dimensions of flax fibre yarns as well as surface modification. The CFFRCs were printed by a fibre prepreg-based 3D printing method, and an in-situ impregnation method was also used to prepare CFFRCs for comparison. The results showed that the CFFRCs by the fibre prepreg method had a fibre volume fraction of 44.1 % and a void content of ∼1.9 % due to the high impregnation degree. Correspondingly, the tensile modulus and strength of the CFFRCs were the highest among the existing reported values of the composites made by 3D printing and even greater than those of the CFFRCs with a fibre volume fraction of ∼51.4 % prepared by the in-situ impregnation method.