Influence Of Fiber Volume Fraction Research Articles

Influence of fiber volume fraction and curing temperature on mechanical properties of jute/PLA green composites

Rising environmental concerns and depletion of petrochemical resources have resulted in an increased interest in biodegradable natural fiber-reinforced polymer composites. In this research work, jute fiber has been used as a reinforcement and polylactic acid (PLA) as the matrix material to develop jute/PLA green composites with the help of compression molding technique. The effect of fiber volume fraction ranging from 25% to 50% and curing temperature ranging from 160°C to 180°C on different samples were investigated for mechanical properties and water absorption. Results obtained from various tests indicate that with an increase in the fiber volume fraction, tensile and flexural strength increases till 30% fiber fraction, thereafter decreases with further increase in fiber content. Maximum tensile and flexural strength of jute/PLA composites was obtained with 30% fiber volume fraction at 160°C curing temperature. The trend obtained from mechanical properties is further justified through the study of surface morphology using scanning electron microscopy.

Fracture performance and numerical simulation of basalt fiber concrete using three-point bending test on notched beam

In this paper, three-point bending tests on precast notched beam and multiscale numerical simulation were used to evaluate and predict the effect of different Basalt Fiber (BF) dosages on the fracture resistance performance for Basalt Fiber Reinforced Concrete (BFRC). The three-point bending test was performed on a series of the notched beams in different sizes and volumetric fiber dosage to obtain the Load-Crack Mouth Opening Displacement (P-CMOD) curves during the loading process. The fracture energy and the double-K fracture parameters were calculated from P-CMOD curves to investigate the influences of fiber volume fraction and beam size on fracture parameters of BFRC. The results indicate that the numerical simulation results are in good coherence with the experimental results. The increase of BF dosage could markedly increase the peak load and the fracture energy of concrete. There was no size effect on fracture energy. Based on the two-parameter fracture theory, the initiation toughness had size effect and increased with the rise of specimen height, while size effect was not significant for unstable toughness. With the augment of fiber dosage, the initiation toughness increased linearly. The unstable toughness varied irregularly with the alteration of fiber dosage but higher than that of ordinary concrete. In addition, this paper developed a homogenization algorithm based on Mori-Tanaka and a multi-scale finite element simulation based on continuum progressive damage theory to evaluate and predict the fracture behavior of BFRC with different sizes and fiber volumetric dosages. The calculated P-CMOD curves from this algorithm were in good agreement with those from experiments and revealed the effects of fiber dosage and size effect on fracture behavior for BFRC.

Influence of Fiber Volume Fraction and Fiber Orientation on the Uniaxial Tensile Behavior of Rebar-Reinforced Ultra-High Performance Concrete

This paper studied the influence of fiber volume fraction ( V f ), fiber orientation, and type of reinforcement bar (rebar) on the uniaxial tensile behavior of rebar-reinforced strain-hardening ultra-high performance concrete (UHPC). It was observed that the tensile strength increased with the increase in V f . When V f was kept constant at 1%, rebar-reinforced UHPC with fibers aligned with the load direction registered the highest strength and that with fibers oriented perpendicular to the load direction recorded the lowest strength. The strength of the composite with random fibers laid in between. Moreover, the strength, as well as the ductility, increased when the normal strength grade 60 rebars embedded in UHPC were replaced with high strength grade 100 rebars with all other conditions remaining unchanged. In addition, this paper discusses the potential of sudden failure of rebar-reinforced strain hardening UHPC and it is suggested that the composite attains a minimum strain of 1% at the peak stress to enable the members to have sufficient ductility.

Equivalent moisture diffusion coefficient of fiber reinforced composites

Total diffusion time and the total moisture absorption amount were proposed as the measurement standards of equivalent coefficients for composites moisture diffusion with impermeable fibers. Representative volume element (RVE) models and 2D transient finite element models of unidirectional fiber reinforced composites were established and the accuracy of the RVE model for calculating the equivalent diffusivity was verified. The influences of fiber volume fraction, fiber arrangement and interfaces on the equivalent moisture diffusivity were investigated using the RVE models. The results show that the equivalent moisture diffusivity decreases with the increase of fiber volume fraction. The equivalent moisture diffusivity of random fiber distribution is smaller than that of the periodic fibers distribution, and this difference can be neglected when the fiber volume fraction is relative small. The interfaces with higher diffusivity than matrix will apparently increase the composites diffusivity.

Vehicle Body of Ganesha Underwater Scooter: Toughness Characteristics of Polyester Matrix Composite Hybrid Reviewed from Variation of Rami Fiber Volume Fraction

This study aimed to determine the influence of fiber volume fraction towards composite toughness and the composite hybrid fracture pattern models reinforced by hemp fiber and fiberglass to find out the ratio of composite toughness from variation of hemp fiber volume fraction and fiberglass A1 (15 : 25), A2 (20 : 20), A3 (25 : 15)%. This research is an experimental method research with the dependent variable is composite toughness and the independent variable is the fiber volume fraction. Based on the test and data analysis, the results for fraction A1 (15 : 25)% have the greatest impact absorption of 10834.6 J/m2 compared to A2 (20 :20)% that have absorption of 8470.828 J/m2 and A3 (25 : 15)% is 7168.813 J/m2. The most prominent one of the three variations of volume fractions on this fracture pattern analysis is the existence of (delamination) or there are fibers which are not perfectly exposed to the matrix. The Delamination usually occurs due to overly tightening of the fibers.

Elastoplastic Residual Stress in Composite Beams

Composite materials have been widely used due to their lightweight capability. For different industrial applications, hybrid beams have been designed to combine the potential advantage of each layer; for instance, for aeronautical structures it is usual to combine Glass Fiber Reinforced Plastic (GFRP) and aluminum layers. In this article a three layer beam is considered, a medial layer is made of GFRP and the other layers are made of aluminum. A detailed discussion about a semi-analytic procedure to evaluate the residual stress in such structure is presented, analyzing the influence of fiber volume fraction on the GFRP layer and the layers thickness. The results indicate the possibility of growing up plastic residual stresses in the aluminum layers.

Computational stability analysis of periodic electroactive polymer composites across scales

This paper is devoted to the multiscale stability analysis of periodic electroactive polymer composites at finite deformations. A particular focus is on the investigation of macroscopic loss of strong ellipticity and microscopic bifurcation-type instabilities. Macroscopic homogenized quantities are determined by use of computational homogenization over selected representative volume elements (RVE). The quasi-incompressible nature of the electroactive polymers is taken into account by considering a four-field variational formulation at micro-level. This formulation includes continuous interpolations of displacement fields and electric vector potentials as well as discontinuous interpolations of pressure and dilatation terms, yielding a saddle-point principle for coupled problems. Static condensation of the terms related to the element-wise constant pressure and dilatation results in a positive definite global microscopic stiffness matrix until a microscopic instability occurs. The microstructure is embedded into a macroscopic driving procedure that imposes periodic mechanical and electrical boundary conditions on the surface of the RVEs. It is known that at certain finite deformations the initial periodicity of microstructures might be altered due to microscopic bifurcation-type instabilities. To incorporate microscopic instabilities and to determine the critical periodicity of microstructures, Bloch–Floquet wave analysis in the context of a finite element discretization is implemented. The macroscopic instabilities, which are related to the long-wavelength microscopic instabilities, are determined by checking the loss of strong ellipticity at macro-scale. The proposed setting is used to study the multiscale stability analysis of electroactive polymer composites with embedded fibers. The influence of fiber volume fraction and aspect ratio of fiber cross sections on instabilities are investigated in detail. Critical periodicities and bifurcation modes are demonstrated for selected boundary value problems.

Flexural response of high‐strength steel‐ultra‐high‐performance fiber reinforced concrete beams based on a mesoscale constitutive model: Experiment and theory

This paper presents the results of experimental and theoretical studies undertaken to assess the flexural performance of high‐strength steel‐ultra‐high‐performance fiber reinforced concrete (HSS‐UHPFRC) beams. A total of nine HSS‐UHPFRC beams were tested, and the influence of fiber volume fraction, fiber type, longitudinal reinforcement ratio, and concrete strength on the flexural response was evaluated. The results indicate that sufficient longitudinal reinforcement should be provided in a UHPFRC beam to avoid abrupt failure and possible catastrophic collapse. After the loss of the fiber bridging effect, corresponding to the fibers being pulled out from the matrix, which occurs one by one with audible sound which is sizzling, redistribution, and homogenization of the concrete stress beside cracks, induced by the dispersed fibers, takes place and more flexural cracks with small spacing appear besides the existing cracks. The beam stiffness was about 85% of the initial beam stiffness at flexural cracking state and was only approximately 25% of the initial beam stiffness at the ultimate state. A constitutive model is proposed, including a bilinear model for compression and a drop‐down model for tension, taking into account uniform distribution, embedment length, and orientation of fibers for the multi‐scale mechanics analysis. A flexural strength model was subsequently derived on the basis of the proposed mesoscale constitutive model; strain compatibility and force equilibrium were taken into account. The prediction of the ultimate flexural capacity and the overall post‐cracking response with the proposed model show a good agreement with the test results.

Theoretical and experimental study on multi-phase model of thermal conductivity for fiber reinforced concrete

In order to clarify the influence of fiber volume fraction on the thermal properties of cement concrete, and improve the calculated accuracy, thermal conductivities of steel fiber reinforced concrete (SFRC) and carbon fiber reinforced concrete (CFRC) were researched through experiments (the QTM-300 or the LFA457) and the composite theory’s models. The influence of fiber volume fraction and the water-cement (W/C) ratio on thermal conductivities of SFRC and CFRC was investigated. Afterwards, the thermal conductivities of fiber reinforced concrete (FRC) were calculated respectively via two-phase theoretical models, multi-phase theoretical models which were derived by composite material theory, and multi-phase prediction model which was proposed based on the different composition materials’ thermal conductivity (cement mortar, aggregate, different fiber) and their volume fraction. Additionally, the above three models were compared and verified by experimental results respectively. The results show that although the volume fraction of the fibers in the concrete is the smallest, the FRC should be still seen as three-phase composite materials. Therefore, the thermal conductivity of FRC will be better predicted by both of the three-phase serial-parallel model and multi-phase prediction model, and the calculated results of the prediction model are closer to experimental results.

Damage initiation and evolution in short fiber reinforced polyamide under fatigue loading: Influence of fiber volume fraction

Abstract This paper investigates the influence of fiber volume fraction on damage mechanisms in a short glass fiber reinforced polyamide (PA66) under fatigue loading. Uniaxial fatigue tests were carried out on notched specimens with different fiber contents (0%, 15%, 25%, 35%, 50% in weight). Some fatigue tests were interrupted before failure with the aim to analyze the crack path. Some other fatigue tests were carried out until specimen failure in order to analyze the fracture surface. Specific fractographic features were investigated: ductile/brittle appearance of the fracture surface, pulled-out/broken fibers, degree of fiber-matrix interfacial adhesion. The damage investigation was performed by using Field Emission Scanning Electron Microscopy (FESEM).

A homogenization model of the Voigt type for skeletal muscle

A three-dimensional constitutive model for skeletal muscle incorporating microstructural characteristics is developed and numerically implemented in a general purpose finite element program. The proposed model takes into account explicitly the volume fractions of muscle fibers and connective tissue by using the Voigt homogenization approach to bridge the different length scales of the muscle structure. The model is used to estimate the active and passive homogenized muscle response. Next, the model is validated by experimental data and periodic three-dimensional unit cell calculations comprising various fiber volume fractions and mechanical properties of the constituents. The model is found to be in very good agreement with both the experimental data and the finite element results for all the examined cases. The influence of fiber volume fraction and material properties of constituents on effective muscle response under several loading conditions is examined.

Experimental investigation of the tensile and bending behavior of multi-axial warp-knitted fabric composites

An experimental study was carried out on the tensile and bending behavior of multi-axial warp-knitted fabric composites. Five specimens reinforced with multi-axial warp-knitted fabric/epoxy were manufactured by a vacuum-assisted resin transfer molding method. Quasi-static tensile and three-point bending tests were carried out in a number of orientations relative to the stitching direction: quadriaxial, triaxial, biaxial (±45° and 0/90°) and unidirectional. The results of the tests revealed that the quadriaxial and biaxial (±45°) samples showed quasi-isotropic behavior, whereas the other laminates showed anisotropic behavior. The influence of fiber volume fraction and the orientation distribution of the constituent material on the tensile and bending behavior were also analyzed. The relationships between the stress and strain and the tensile and bending behavior of different multi-axial warp-knitted fabric composite were obtained by polynomial fitting.

The Influence of Fiber Volume Fraction on Thermal Conductivity of Pultruded Profile

The Influence of Fiber Volume Fraction on Thermal Conductivity of Pultruded Profile

Influence of fibre volume fraction and temperature on fatigue life of glass fibre reinforced plastics

The influence of fibre volume fraction and temperature on fatigue life of continuous glass fibre reinforced plastics is investigated in detail. The physical causes of the two effects on the slope of the S-N-curve in fibre direction at R = 0.1 are researched and can be explained with help of micrographs. A new phenomenological approach is presented to model both effects in fibre dominated laminates with different stacking sequences using only the static ultimate strength as an input. Static and fatigue tests of different layups and fibre volume fractions are performed at different temperatures to validate the fatigue life predictions. Additionally it is derived that there is an optimal fibre volume fraction regarding a minimum damage sum. This fibre volume fraction is dependent on a given loading spectra and can be calculated using the phenomenological model.

Micromechanics of shape memory alloy fiber–reinforced composites subjected to multi-axial non-proportional loadings

In this article, micromechanical behavior of metal matrix reinforced with shape memory alloy fibers under combined thermo-mechanical loadings is investigated. A representative volume element consisting of circular/rectangular cross-sectional shape memory alloy fibers surrounded with aluminum matrix is considered to model micromechanical behavior of shape memory alloy composites. In order to simulate main features of shape memory alloy fibers, especially under multi-axial non-proportional loadings, Panico–Brinson constitutive model is employed. This model is able to predict martensite transformation, shape memory effect, pseudo-elasticity, and in particular reorientation of martensite variants which is responsible for non-proportional loadings. Furthermore, the response of aluminum matrix is assumed as a thermo-elastic-plastic material with linear kinematic work hardening. A finite element formulation containing incremental and iterative processes is developed to analyze the representative volume element in the state of generalized plane strain. Convergence, cost, and comparative studies are conducted to examine efficiency and accuracy of the developed solution. Then, a set of parametric study is directed to provide an insight into the influence of fiber volume fraction, fiber cross-sectional shape, pre-strain, and temperature on the micromechanical behavior of shape memory alloy composites subjected to multi-axial loadings. A significant coupling is observed between normal–normal/normal–shear/shear–shear strains during non-proportional multi-axial loadings which confirms the importance of simulation of martensite reorientation.

Influence of Splitting Load and Polypropylene Fiber on Permeability of Chloride Ion in Concrete

Orthogonal experiment is used to study the influence of splitting load and mixing of polypropylene fiber of different volume fraction, different length and different mass ratio of long and short fiber on permeability of chloride ion in concrete. The results show that the chloride ion diffusion coefficient increases as the stress ratio increasing, and the relationship between them approximately agrees with exponential function. The influences of fiber volume fraction and fiber length on permeability of chloride ion in concrete are significant, and using shorter polypropylene fiber in the range of low volume fraction can lower permeability of chloride ion in concrete, whereas long fiber and large volume fraction will increase the permeability. The effect of lowering permeability of chloride ion in concrete is most obvious, when the fiber volume fraction is 0.1%, the fiber length is the combination of 6mm and 9mm, and the mass ratio of long and short fiber is 1:2.

Influence of fiber waviness on the effective properties of discontinuous fiber reinforced composites

In this study, 3D Representative Volume Element (RVE) models are used to investigate the effect of fiber waviness not only on the Young’s moduli but also on the shear moduli and Poisson’s ratios of unidirectional discontinuous fiber reinforced (DFR) composites. In order to measure the sole influence of fiber waviness, properties of the RVE model with curved fibers are compared with those of the RVE model with corresponding straight fibers. This comparison shows that fiber waviness significantly affects E11 and moderately affects all the other effective properties. Variation in E22 due to fiber waviness is contrary to general expectations. It is observed that E22 initially decreases and then increases with the increase in fiber waviness. Influence of fiber volume fraction (Vf), fiber/matrix material property mismatch, fiber spatial distribution and fiber/matrix interphase region on the effective properties of DFR composite with curved fibers is also numerically investigated. It is found that Vf, material property mismatch and interphase region have strong influence whereas spatial distribution has weak influence on the effective properties of unidirectional DFR composite containing curved fibers.

Influence of Fiber Volume Fraction, Fiber Angle and Hole Size on the Stress Concentration around the Circular Hole of an Orthotropic Lamina under unidirectional in Plane Loading

This work examines the effect of fiber angle, fiber volume fraction and hole size on the stress concentration around the circular hole of (AS4/3501-6) carbon/Epoxy lamina subjected to unidirectional in plane loading. Three independent fiber volume fractions and fiber orientations for three different hole sizes are considered. Both analytical and finite element solutions are presented using micro and macro mechanics approaches of analysis of orthotropic lamina and by using ANSYS10 finite element package. The analysis is initially carried out by fixing the hole size and by varying the other two parameters (fiber angle and fiber volume fraction). Next, the fixing parameter is interchanged in a cyclic fashion and the process is continued. It is found that the whole size and fiber orientation have greater influence on the stress intensity concentration around the hole vicinity compared to fiber volume fraction.

Analysis of FRP composites under frictional contact conditions

This work studies numerically the tribological behavior of fiber-reinforced plastics (FRP) under different frictional contact conditions, using a boundary element methodology. The formulation uses the Boundary Element Method (BEM) with an explicit approach for fundamental solutions evaluation, for computing the elastic influence coefficients. To enforce the contact constraints on the potential contact zone: Signorini’s contact conditions and an orthotropic law of friction, contact operators over the augmented Lagrangian are considered in the formulation. The methodology and the proposed algorithm are applied to study two types of glass FRP and two types of carbon FRP, with the same fiber volume fraction, under frictional contact. In these studies, it can be observed how the fiber orientation and sliding orientation affect the normal and tangential contact compliance, as well as the contact traction distribution. Furthermore, the formulation considers a micromechanics model for FRP that allows also to study the influence of fiber volume fraction on normal and tangential contact compliances.

Influence of Fiber Volume Fraction and Aggregate Size on Flexural Behavior of High Strength Steel Fiber-Reinforced Concrete (SFRC)

The effects of aggregate size and fiber volume fraction on the flexural behavior of 70MPa high strength steel fiber-reinforced concrete (SFRC) were investigated in this work. Test variables consist of fiber volume fraction (0, 1 and 2 %) and maximum aggregate size (8, 13 and 20 mm). The prism for flexural test was 100 x 100 x 400 mm and was tested under four points loading. Flexural toughness index was measured using ASTM C 1018 procedure. Test results indicated that the addition of steel fiber to 70MPa high strength concrete improves flexural and post-cracking behaviors. This phenomenon is remarkable for SFRC mixture with higher fiber content and smaller aggregate size. Also, the flexural toughness of high strength SFRC depends primarily on fiber content. The maximum aggregate sizes were secondary in importance.