Effects Of Fiber Volume Fraction Research Articles

Finite element analysis of stress distribution and burst failure of SiCf/Ti–6Al–4V composite ring

A three-dimensional cyclic symmetry finite element model of titanium-matrix composites (TMCs) ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.

Effect of layer shift on the out-of-plane permeability of 0°/90° noncrimp fabrics

Layer shift has a great effect on the permeability which is a key parameter in resin transfer molding. In this paper, nine different unit cells were modeled based on the range of layer shift and decomposed into zones of characteristic yarn arrangement, respectively. For each unit cell, a set of equations was derived allowing description of the local permeability of each zone as a function of geometrical yarn parameters. The overall permeability was then modeled as a mixture of permeabilities of different zones with the electrical resistance analogy. Excellent agreement was found between predictions and experiment. Both results indicated that the channel flow had a dominant role in the whole flow through the fabrics. And the permeability values reached maximum when the empty regions were interconnected between upper and lower layers. In addition, the effect of fiber volume fraction on the differences of two extreme cases was also investigated.

Micro-mechanics of composite with SMA fibers embedded in metallic/polymeric matrix under off-axial loadings

Abstract In this article, micro-thermo-mechanical response of composites with shape memory alloy (SMA) fibers surrounded by the metallic/polymeric matrix under multi-axial proportional/non-proportional loadings is investigated. A three-dimensional constitutive model with capability of the simulation of martensite transformation, reorientation of martensite variants, pseudo-elasticity and shape memory effects of SMA fibers is implemented. Elastic and elastic–plastic constitute equations are also utilized to characterize the mechanical behavior of polymer and metal matrices. The solution domain includes a representative volume element (RVE) consists of an SMA fiber surrounded by corresponding matrix in a square array arrangement. Finite element modeling of the prescribed RVE is developed based on the virtual work in the state of the generalized plane strain. Governing equations are solved by means of an incremental and iterative procedure with satisfying periodic boundary conditions. The effects of fiber volume fraction, off-axis angle, matrix material and pre-strain on the micro-thermo-mechanical behavior of composites with embedded SMA fibers subjected to various multi-axial proportional/non-proportional loadings are examined and discussed in detail. The results are reported for the first time and can be served as benchmark for future studies dealing with the analysis of macro composite structures consist of SMA fibers.

Mechanical properties, fatigue damage and microstructure of carbon/epoxy laminates depending on fibre volume content

This paper investigates the effect of fibre volume fraction on the fatigue behaviour and damage mechanisms of carbon/epoxy laminates. Epoxy resin and unidirectional carbon/epoxy specimens with two different fibre volume fractions are tested under quasi-static tensile and tension–tension fatigue loads at angles of 0°, 45° and 90°. Fracture surfaces are studied with scanning electron microscopy. The results show that stiffness and strength increase with increasing fibre volume fractions. The damage behaviour of off-axis specimens changes with increasing fibre volume content and the height of the applied cyclic load. While matrix cracking and interfacial debonding are dominating damage mechanisms in specimens with low fibre content, fibre bridging and pull out are monitored with increasing fibre content. The higher the applied load in fatigue tests transverse to fibre direction, the more similar behave specimens with different fibre volume fractions.

Effect of Fiber Volume Fraction on Compressive and Flexural Properties of High-Strength Steel Fiber Reinforced Concrete

The purpose of this study is to investigate the compressive and flexural properties of high-strength steel fiber reinforced concrete (SFRC). For this purpose, a total of 5 mixture whose variable is fiber volume fraction, were made and tested in a range of high strength with 70MPa. In case of normal and ultra-high strength, experimental results were collected from existing literatures on the tests conducted in South Korea. Flexural behavior of SFRC is enhanced according to the fiber volume fraction and compressive strength. Experimental and collected data were applied to existing equations, so it was found that the distinctions occurred between experimental or collected data and calculated values. Thus, more efforts are required to predict the flexural behavior of SFRC manufactured in South Korea with respect to the fiber volume fraction.

Free vibration analysis of fiber reinforced composite conical shells resting on Pasternak-type elastic foundation using Ritz and Galerkin methods

In this paper, free vibration analysis of fiber reinforced composite (FRC) conical shells resting on Pasternak-type elastic foundation is investigated. Two kinds of fiber distribution in the thickness direction, namely, uniformly distributed and functionally graded are considered. The material properties of FRC conical shells are estimated through a volume fraction power law. The equations of motion are derived through variational formulation. The governing equations are developed based on the classical shells theory and Sanders assumptions. Galerkin and Ritz methods are employed to solve the governing equations and determine natural frequencies of the conical shell. The conical shell assumed to be clamped at the both ends. Results are presented on the effect of fiber volume fraction, semi-vertex angle, thickness to radius ratio and elastic foundation stiffness parameters on the frequency characteristics of the conical shells. A comparative study between Ritz and Galerkin methods is carried out. Validity of the present study is confirmed by comparing the results with the data available in the open literature for a special case. A good agreement is observed between them.

Modeling and experimental evaluation of functional failure pressures in glass fiber reinforced polyester pipes

The main objective of this paper is to predict the functional failure pressure of Glass fiber Reinforced Polyester (GRP) pipes subjected to hydrostatic internal pressure. A progressive modeling procedure is developed to predict the internal pressure associated with weepage. The developed modeling consists of stress analysis, failure evaluation and material degradation. The influence of micromechanics rules for estimating mechanical properties of constructing layers and failure criteria for predicting failure occurrence are examined in comparison with experimental observations and the best combinations of them are identified. First-ply failure and functional failure pressures are determined and compared. A parametric study is conducted investigating the effect of fiber volume fractions and winding angles on the failure pressures. The study is performed on five different volume fractions of 52.5%, 55%, 57.5% and 60% and three different winding angles of 52.5°, 57.5° and 60.19°. The results show that the functional and first-ply failure pressures decrease by increasing fiber volume fractions; while the higher winding angles (measured from the axial axis of pipe) enhance functional failure pressures.

Prestressed FRP and new rigidity model on interfacial stresses analysis: an improved approach

In this study, the effect of fiber volume fraction and the prestressed laminates model on the interfacial stresses concentration was studied. This research investigates analytically the bond characteristics between high modulus FRP-strengthened steel members and the flexural behavior of these members. It has been suggested that the prestressed strengthening is more economic alternative to unstressed strengthening. Experiments and applications have shown the flexural stiffness and moment capacity of beams were improved significantly by the use of the prestressing FRP methods and the fiber volume fraction. In this paper, a solution is presented to calculate the interfacial stresses of beams strengthened with a new rigidity model coupled with the thermal and shear-lag effect, which are neglected by the previous studies. A parametric study was carried out to show how the stresses concentration and distribution are influenced by the dimensions of the adherends and the material properties of the strengthened beam.

Effect of fiber volume fraction on crack propagation rate of ultra-high toughness cementitious composites

An investigation on the fatigue crack propagation law and the effect of fiber volume fraction on crack propagation rate of ultra-high toughness cementitious composites is carried out in this paper. Three fiber fractions, 1.5%, 2.0% and 2.5% are adopted. The research result shows that multiple random cracks are generated for the fracture specimens of this material under fatigue load, while the crack number depends on fatigue stress level and fiber fraction. With the increase of fiber volume fraction, the crack growth threshold is improved, while the crack propagation rate is decelerated. Meanwhile, the crack propagation rate is obviously affected by the fatigue loads.

A Zener–Stroh crack in fiber-reinforced composites with generalized Irwin plastic zone correction

Abstract Elastic–plastic stress analysis on a matrix Zener–Stroh crack interacting with nearby inclusions (the fibers) in fiber-reinforced composites has been carried out. The Zener-Stroh crack is initiated near one of the inclusions, while the effect of other inclusions in the composite is considered through simulating the composite material by the cylindrical three-phase model. Plastic zone correction is introduced the first time for such a crack-inclusion interaction problem so that the fracture behavior can be analyzed more accurately. To determine the plastic zone sizes, a generalized Irwin model is proposed for the mixed-mode loading problem where the Von Mises stress yielding criterion is employed. Different to a Griffith crack, a Zener–Stroh crack propagation always occurs from the sharp tip whose relative position to the near-by fiber has great effect on the fracture behavior of the crack. In our study, the effective stress intensity factor (SIF), plastic zone size (PZS) and crack tip opening displacement (CTOD) are evaluated by solving the formulated singular integral equations. Through the numerical examples, the influence of the inclusion (fiber) shear modulus, inclusion volume fraction and the crack sharp tip position on the fracture behavior of the crack is discussed. It is found that the shear modulus ratio has great effect on the normalized values of PZS and CTOD, while the effect of fiber volume fraction depends highly on the conditions of the inclusion/matrix properties and the crack sharp tip position.

On the homogenization of metal matrix composites using strain gradient plasticity

The homogenized response of metal matrix composites (MMC) is studied using strain gradient plasticity. The material model employed is a rate independent formulation of energetic strain gradient plasticity at the micro scale and conventional rate independent plasticity at the macro scale. Free energy inside the micro structure is included due to the elastic strains and plastic strain gradients. A unit cell containing a circular elastic fiber is analyzed under macroscopic simple shear in addition to transverse and longitudinal loading. The analyses are carried out under generalized plane strain condition. Micro-macro homogenization is performed observing the Hill-Mandel energy condition, and overall loading is considered such that the homogenized higher order terms vanish. The results highlight the intrinsic size-effects as well as the effect of fiber volume fraction on the overall response curves, plastic strain distributions and homogenized yield surfaces under different loading conditions. It is concluded that composites with smaller reinforcement size have larger initial yield surfaces and furthermore, they exhibit more kinematic hardening.

Modeling and experimental evaluation of functional failure pressures in glass fiber reinforced polyester pipes

The main objective of this paper is to predict the functional failure pressure of glass fiber reinforced polyester (GRP) pipes subjected to hydrostatic internal pressure. A progressive modeling procedure is developed to predict the internal pressure associated with weepage. The developed modeling consists of stress analysis, failure evaluation and material degradation. The influence of micromechanics rules for estimating mechanical properties of constructing layers and failure criteria for predicting failure occurrence are examined in comparison with experimental observations and the best combinations of them are identified. First-ply failure and functional failure pressures are determined and compared. A parametric study is conducted investigating the effect of fiber volume fractions and winding angles on the failure pressures. The study is performed on five different volume fractions of 52.5%, 55%, 57.5% and 60% and three different winding angles of 52.5°, 57.5° and 60.19°. The results show that the functional and first-ply failure pressures decrease by increasing fiber volume fractions; while the higher winding angles (measured from the axial axis of pipe) enhance functional failure pressures.

XFEM for the evaluation of elastic properties of CNT-based 3-D full five-directional braided composites

In the present work, a 3-D unit cell model is proposed to predict the elastic behavior of 3-D full five-directional braided composites. The model is analyzed by extended finite element method. An effective medium approximation scheme is used to evaluate the elastic properties of the composite. In the proposed unit cell model, the interface between the fiber and matrix is modeled by PU enrichment. The effects of fiber volume fraction and interior angle of braiding yarn on the elastic properties are analyzed in detail. To further enhance the elastic properties, the braided composite is enforced by randomly distributed carbon nanotubes (CNTs). A new method is proposed to evaluate the effect of CNTs on the effective properties of the composite. The present simulations show that the addition of 3% CNTs increases the effective elastic properties of 3-D braided composite nearly by 100%.

Effects of fibre volume fraction on the compressive and flexural experimental behaviour of SFRC

The purpose of this study is to analyse the effects of fibre volume fraction on the mechanical properties of SFRC (Steel Fibre Reinforced Concrete). The results obtained from compression and four-point bending tests carried out on concrete specimens with fibre volume fraction of 1%, 1.6%, 3% and 5% are critically examined. The experimental behaviour in terms of peak load, post-peak behaviour, and residual strength, are evaluated and compared. The fibre distribution and their contribution in Mode I fracture is also assessed. The effects of steel fibre volume fraction on the strength, ultimate strain and ductility index of SFRC are highlighted in order to give a guide for structural use.

A comparison of tensile properties of polyester composites reinforced with pineapple leaf fiber and pineapple peduncle fiber

Pineapple fiber which is rich in cellulose, relatively inexpensive, and abundantly available has the potential for polymer reinforcement. This research presents a study of the tensile properties of pineapple leaf fiber and pineapple peduncle fiber reinforced polyester composites. Composites were fabricated using leaf fiber and peduncle fiber with varying fiber length and fiber loading. Both fibers were mixed with polyester composites the various fiber volume fractions of 4, 8 and 12% and with three different fiber lengths of 10, 20 and 30 mm. The composites panels were fabricated using hand lay-out technique. The tensile test was carried out in accordance to ASTM D638. The result showed that pineapple peduncle fiber with 4% fiber volume fraction and fiber length of 30 mm give highest tensile properties. From the overall results, pineapple peduncle fiber shown the higher tensile properties compared to pineapple leaf fiber. It is found that by increasing the fiber volume fraction the tensile properties has significantly decreased but by increasing the fiber length, the tensile properties will be increased proportionally. Minitab software is used to perform the two-way ANOVA analysis to measure the significant. From the analysis done, there is a significant effect of fiber volume fraction and fiber length on the tensile properties.

Predicting the elastic properties of sisal fiber reinforced polypropylene composites by a new method based on generalized method of cells and laminate analogy approach

Abstract In this paper, a new method based on generalized method of cells and laminate analogy approach was used to predict the elastic properties of short sisal fiber reinforced polypropylene composites. The effects of fiber volume fractions and fiber aspect ratios on the elastic properties of composites were studied by the new model and other models. Continuous fiber composite and layered composite, as two special cases were analyzed in detail by this new model. The results show that both fiber volume fraction and fiber aspect ratio have significant effects on the axial Young’s modulus. However, the fiber volume fraction has very small effects on the transverse Young’s modulus, axial shear modulus and axial Poisson’s ratio. The new model agrees better than other models with the experimental data. The elastic properties of composites with complex microstructures can be predicted efficiently by this new model.

Micromechanical Analysis of Heterogeneous Composites using Hybrid Trefftz FEM and Hybrid Fundamental Solution Based FEM

ABSTRACTIn this paper, a new algorithm is developed based on the homogenization method integrating with the newly developed Hybrid Treffe FEM (HT-FEM) and Hybrid Fundamental Solution based FEM (HFS-FEM). The algorithm can be used to evaluate effective elastic properties of heterogeneous composites. The representative volume element (RVE) of fiber reinforced composites with periodic boundary conditions is introduced and used in our numerical analysis. The proposed algorithm is assessed through two numerical examples with different mesh density and element geometry and used to investigate the effect of fiber volume fraction, fiber shape and configuration on the effective properties of composites. It is found that the proposed algorithm is insensitive to element geometry and mesh density compared with the traditional FEM (e.g. ABAQUS). The numerical results indicate that the HT-FEM and HFS-FEM are promising in micromechanical modeling of heterogeneous materials containing inclusions of various shapes and distributions. They are potential to be used for future application in multiscale simulation.

Flexural Toughness of Hybrid Fiber Reinforced High-Performance Concrete under Three-Point Bending

A set of new hybrid fiber reinforced high-performance concrete was developed and studied by experiment. The fibers incorporated the concrete are the collection of the steel fiber, modified polypropylene fiber and polypropylene with total fiber content not more than 1%. And the compressive test, splitting tensile test and the flexural toughness test were performed on eight groups of specimens. Based on the load-deflection and load-CMOD curves and the equivalent flexural tensile strength, the effect of fiber volume fraction and hybrid mode upon concrete's mechanical properties and post-peak behavior were investigated. The test results show that the mixing of the three different fibers can increase concrete's splitting tensile strength and flexural toughness more effectively with no significantly effect on compressive strength. The mixture of the three different fibers exist the optimization problem. Based on the results of the analysis, the compatible proportion of the three fibers is 0.7% steel fiber, 0.19% modified polypropylene fiber and 0.11% polypropylene fiber.

Material properties of a new hybrid fibre-reinforced engineered cementitious composite

This paper explores experimentally the mechanical properties of a new hybrid fibre-reinforced engineered cementitious composite (ECC) material reinforced with 1.75% polyvinyl alcohol (PVA) fibre and 0.58% steel (SE) fibre. The development of this new ECC aims to achieve better impact resistance. A series of experiments were carried out to determine the compressive strength, Young’s modulus, modulus of rupture, and tensile characteristics of the new material. In the direct tensile test, tensile characteristics of the new material with varying strain rate from 1×10−5 to 1×10−1 per second were investigated to determine the rate dependence of the material. Material properties of the ECC reinforced with 1.5% PVA fibre and 0.5% SE fibre, which is denoted as the reference mix in this paper and has been claimed to be the most promising composition of fibres for impact resistance was also tested in this study for comparison and for determination of effect of fibre volume fraction on the material properties. It was concluded that the new ECC reinforced with 1.75% polyvinyl alcohol (PVA) fibre and 0.58% steel (SE) fibre exhibits improved strength and strain capability than the reference ECC, which are both essential for improving impact resistance.

Multi-scale simulation and finite-element-assisted computation of elastic properties of braided textile reinforced composites

This article deals with the computation of effective elastic properties of braided textile composites assisted by finite element analysis. In this approach, dynamic representative unit cells are first constructed to model typical geometry of braided textile preform. After establishing the elastic properties of braiding yarns, the effective Young’s moduli, shear moduli and Poisson’s ratios corresponding to varying braiding angles are obtained by analysing these geometric models of preform with the help of the commercial finite element analysis code Abaqus. Effects of fibre volume fraction on the elastic properties of both biaxial and triaxial composite unit cells are also examined. Finally, the bending behaviour of a simply supported beam with braided composite skin is evaluated via the finite element analysis assisted multi-scale modelling, which is further verified experimentally. The predicted results were compared favourably with the experiment, backing the accuracy of the proposed modelling approach.