Effects Of Fiber Volume Fraction Research Articles

Determination of the Piezoelectric Properties of Fine Scale PZT Fibres

Finite Element (FE) modelling is used to determine the effect of fibre volume fraction, aspect ratio and polymer matrix stiffness on the d(33) coefficients of 1-3 connectivity piezoelectric fibre composites. The aim is to use these observations as a means of determining the d(33) of fine scale lead zirconate titanate (PZT) fibres. Results from a I-D analytical model fit well with FE predictions for low aspect ratios. Two commercially available PZT-5A fibres, produced via the viscous suspension spinning process (VSSP) and an extrusion process, were fabricated into 1-3 composites with varying fibre volume fi-actions. The composite d(33) measurements are compared to the model predictions and used to determine the d(33) coefficients of the fibers. The d(33) of the VSSP fibres and extruded fibres is measured as 365 pCN(-1) and 235 pCN(-1) respectively using this method. The large difference in the piezoelectric coefficients is possibly linked to the grain size and porosity, which is examined using scanning electron microscopy.

Compressive Failure Mechanism and Impact Behavior of Unidirectional Carbon-Fiber/Vinyl Ester Composites

Compressive failure of carbon fiber reinforced unidirectional vinyl ester composites (CFRP) under impact is studied experimentally and analytically. Both impact and quasi-static compressive tests are carried out for CFRP with Vf= 10% to 60%. Stress-stain curves at strain rates of 10-3 s-1 and 10-3 s-1 are obtained. The compressive strength increases under impact loading. As the fiber volume fraction increases, the failure mode changes from shear failure to kinking. The local stress fields in the fiber and matrix are analysed to illustrate the deformation and compressive failure mechanisms for unidirectional composites. Based on analysing the local matrix yield at the fiber-matrix interface due to shear stress concentration, the compressive strength is predicted. Assuming that shear failure and kinking occurs on the plane of the maximum shear strain in composites, the angle of the plane of the maximum shear strain is determined. The analytical model is utilised to explain the various experimental observations of CFRP failure, as well as GFRP failure reported in Reference [17], such as, the compressive strength, the failure mode, the effects of fiber volume fractions and strain rates.

In-situ observations of titanium metal-matrix composites under transverse tensile loading

The transverse stress-strain behavior of several titanium metal-matrix composites (TiMMCs) has been studied in-situ. Debonding of 1140+/Ti-6-4 composites occurs over a range of stresses. The sharpness of the first “knee” is affected by the fiber volume fraction and by the relative moduli of the matrix regions and the reinforced composite. It has been observed that debonding occurs mainly at the interface between two sublayers of carbon/carbon coatings in 1140+/Ti-6-4 composites and mainly at the interface between the carbon/reaction zone in the as-processed and peak-aged 35 pct SCS-6/Tiβ21s composites. At surface positions, this process starts at very low stresses (≥50 MPa) from the positions with sharp changes of curvatures (or undulations), voids, or debris at the periphery of the interface. Cracking of the outermost carbon sublayer and of the reaction zone in the 1140+/Ti-6-4 composites and the reaction zone in the SCS-6/Tiβ21s composites occurs during elastic deformation of the matrix. This has been directly observed in a field-emission gun (FEG)-scanning electron microscope (SEM) under incremental loading. Although these cracks are arrested and blunted by the matrix material, they cause local stresses and, thus, stimulate local plastic deformation of the matrix and subsequent development of a second knee on the stress-strain curve. The in-situ observations are discussed in terms of the effects of fiber volume fraction and fiber type on the loci and dynamic processes of interfacial debonding, cracking of carbon coatings and reaction zones, and plastic deformation of the matrix.

The effect of fiber volume fraction on filament wound composite pressure vessel strength

This paper is a continuation of previous research reported in Ref. [1] . The previous paper discussed the relationship between fiber volume fraction in filament wound composite vessels and failure pressure. This research included a design of experiment investigation of manufacturing and design variables that affect composite vessel quality and strength. Statistical analysis of the data shows that composite vessel strength was affected by the manufacturing and design variables. In general, it was found that the laminate stacking sequence, winding tension, winding-tension gradient, winding time, and the interaction between winding-tension gradient and winding time significantly affected composite strength. The mechanism responsible for increases in composite strength was related to the strong correlation between fiber volume fraction in the composite and vessel strength. Cylinders with high-fiber volume in the hoop layers tended to deliver high-fiber strength. This paper further examines the relationship between fiber volume fraction and fiber strain to failure. Data from unidirectional strand tests and additional vessel tests are presented. A computer program that is based on the thermokinetics of the resin and processing conditions is used to calculate the fiber volume fraction distribution in the filament wound vessel. The strand's strength-versus-fiber volume data together with the computer program are used to predict composite vessel burst pressure. In general, good agreement with experimental data is observed.

Electrical Impedance Spectra to Monitor Damage during Tensile Loading of Cement Composites

Conductive fibers can reinforce concrete and monitor damage leading to the development of smart material. This research studied the correlation between the electrical and mechanical properties of cement composites reinforced with conductive carbon fibers. The tensile behavior and impedance behavior of extruded and notched composites with a fiber volume fraction of 0.5 and 3% were examined; mechanical load and electrical field were applied longitudinally. The crack growth of these composites during loading was observed and analyzed by digital image correlation. Impedance spectroscopy (IS) measurements were made under loaded and unloaded conditions to address the effect of specimen geometry, the manufacturing process, and the effect of fiber volume fraction. Using these IS measurements, along with numerical computation, the bridging area of the fibers could be extracted quantitatively from the tensile measurements. It is shown that such methods can be useful to elucidate the role of the reinforcing fibers during fracture.

Study on creep behavior of glass fiber reinforced polycarbonate

In this study, tests on creep behavior of glass fiber reinforced polycarbonate were carried out at elevated temperatures. The result showed that creep behavior of GFRPC composites represented good agreement with Arrhenius reciprocation law of time-temperature. The effect of fiber volume fraction on creep behavior was also been studied. Here two shift factors—a modulus shift factor and a time shift factor—were introduced to draw the grand master curve of the creep compliance curves of various fiber contents. It became possible to estimate the creep behavior of GFRPC composites with any fiber contents using the grand master curve of creep compliance master curves and time and modulus shift factors. So it became possible to design materials for creep by reinforcing quantity of fibers to obtain the required objectives.

Effect of fiber volume fraction on the stress intensity factors for multi layered composites under arbitrary anti-plane shear loading

A multi-layered orthotropic material with a center crack is subjected to an anti-plane shear loading. The problem is formulated as a mixed boundary value problem by using the Fourier integral transform method. This gives a Fredholm integral equation of the second kind. The integral equation is solved numerically and anti-plane shear stress intensity factors are analyzed in terms of the material orthotropy for each layer, number of layers, crack length to layer thickness and the order of the loading polynomial. Also, the case of monolithic and hybrid composites are investigated in terms of the local fiber volume fraction and the global fiber volume fraction.

Tensile properties of short-glass-fiber- and short-carbon-fiber-reinforced polypropylene composites

Composites of polypropylene (PP) reinforced with short glass fibers (SGF) and short carbon fibers (SCF) were prepared with extrusion compounding and injection molding techniques. The tensile properties of these composites were investigated. It was noted that an increase in fiber volume fraction led to a decrease in mean fiber length as observed previously. The relationship between mean fiber length and fiber volume fraction was described by a proper exponential function with an offset. The tensile strength and modulus of SGF/PP and SCF/PP composites were studied taking into account the combined effect of fiber volume fraction and mean fiber length. The results about the composite strength and modulus were interpreted using the modified rule of mixtures equations by introducing two fiber efficiency factors, respectively, for the composite strength and modulus. It was found that for both types of composites the fiber efficiency factors decreased with increasing fiber volume fraction and the more brittle fiber namely carbon fiber corresponded to the lower fiber efficiency factors than glass fiber. Meanwhile, it was noted that the fiber efficiency factor for the composite modulus was much higher than that for the composite strength. Moreover, it was observed that the tensile failure strain of the composites decreased with the increase of fiber volume fraction. An empirical but good relationship of the composite failure strain with fiber volume fraction, fiber length and fiber radius was established.

Effects of fiber volume fraction, hot pressing parameters and alloying elements on tensile strength of carbon fiber reinforced copper matrix composite prepared by continuous three-step electrodeposition

Carbon fiber reinforced copper matrix composites have been produced by continuous three-step electrodeposition plus hot pressing technique. Iron or nickel element was added to copper matrix to improve interfacial bonding of the composite. The effects of fiber volume fraction and hot pressing parameters (temperature, pressure and time) on the tensile strength of the composite were investigated. Emphasis was placed on the influence of alloying elements on the tensile strength of the composite. The composite was found to exhibit the highest strength at an optimum V f, hot pressing parameter temperature, pressure, or time by keeping other parameters constant. This optimum value was related to the alloying element incorporated in the copper matrix. It is observed that incorporation of alloying elements does not change the general trends, but changes the mechanism governing the decreasing trends of the tensile strength of the composites as the hot pressing temperature exceeds the optimum value. Further, the alloying elements affect the highest strength values ( σ max). C/Cu(Ni) composite with the medium interfacial bonding strength exhibits the highest σ max. It is concluded from our experiments that a diffusion bonding is preferable since the fiber–matrix interaction can be easily controlled and the fiber degradation is limited during hot pressing process.

An Investigation of the Effects of Fiber Volume Fraction on the Impact Properties of Fiber Reinforced Composite Laminated Plates

The effects of fiber volume fraction (Vf) on the impact properties of glass-epoxy laminated composite plates were studied. The plates had a constant amount of fiber, and the weight of epoxy was varied to produce a range of fiber volume fractions from 40-70%. The plates were impacted at low velocity in a drop tower impactor with energies varying from 10 J to 40 J. Load, deflection and energy absorbed data were analyzed with the purpose of determining the effects of fiber and void volume fractions on the impact response of the plates. Damage modes were also investigated.

Effect of fiber volume fraction on the fracture behavior of Nb-1 wt pct Zr/218W composites at elevated temperatures

Nb-1 wt pct Zr/218W long-fiber composite monotapes, nominally containing 0 to 70 vol pct of 218 tungsten fibers, were fabricated by arc spraying the Nb-1 pct Zr matrix onto the tungsten fibers. The monotapes were consolidated by hot pressing and hot isostatic pressing techniques. Tensile tests conducted between 1400 and 1600 K, under engineering strain rates varying between 1.5×10−5 and 1.5×10−3 s−1, demonstrated that composites containing 70 vol pct of fibers had the highest strength-to-density ratio. Microstructural observations of specimens tested at 1400 K revealed that composites containing less than 50 vol pct of fibers showed extensive matrix cavitation, fiber-matrix debonding, and necking of the fibers. Above 50 vol pct, the composite matrix was less prone to cavitation, with an increasing tendency toward shear deformation of the fibers as the fiber volume fraction increased. No fiber damage was observed at 1400 K away from the fractured end, but significant fiber damage was observed at higher temperatures. A phenomenological model is presented to rationalize these observations.

Effect of fiber volume fraction on the fracture behavior of Nb-1 Wt pct Zr/218W composites at elevated temperatures

Effect of fiber volume fraction on the fracture behavior of Nb-1 Wt pct Zr/218W composites at elevated temperatures

Polymer Matrix Composites Subjected to Low Velocity Impact: Effect of Fibre Volume Fraction

Article Polymer Matrix Composites Subjected to Low Velocity Impact: Effect of Fibre Volume Fraction was published on December 1, 2000 in the journal Science and Engineering of Composite Materials (volume 9, issue 4).

An Investigation of the Effects of Fiber Volume Fraction on the Impact Properties of Fiber Reinforced Composite Laminated Plates

An Investigation of the Effects of Fiber Volume Fraction on the Impact Properties of Fiber Reinforced Composite Laminated Plates

Fracture resistance of short-glass-fiber-reinforced and short-carbon-fiber-reinforced polypropylene under Charpy impact load and its dependence on processing

Abstract In this paper, short-glass-fiber-reinforced and short-carbon-fiber-reinforced polypropylene composites were investigated with respect to the work of fracture (WOF), here viz the notched Charpy impact energy. Short glass fibers and short carbon fibers were incorporated into polypropylene with a twin-screw extruder and all of the specimens were injection molded into dumbbell-shaped tensile bars in a twin-screw injection-molding machine. Rectangular impact bars were obtained from tensile bars by removing the two clamping parts. Charpy impact tests were performed with a Charpy impact tester on specimens with V-notches. The values of the notched Charpy impact energy were obtained from each group of eight specimens. The effects of glass and carbon fiber volume fractions on their lengths in single and hybrid short fiber composites were investigated. The composite WOF was studied qualitatively by taking into account the effects of fiber volume fraction and fiber length distributions using the total WOF theory. Fiber length distributions have been previously shown to depend on the processing conditions. On the other hand, the composite impact resistance was shown to depend on fiber length and hence on processing. The dependence of the composite impact energy on processing is discussed.

Creep Behavior of Metal Fiber-PPE Composites and Effect of Test Surroundings

The effect of environment on creep behavior of Poly-Phenylene Ether (PPE) composites with stainless steel fiber was investigated in this research. The results of creep behavior of PPE composites, carried out both in air and oil surroundings at elevated temperatures, show very good agreement with the Arrhenius reciprocation law of time-temperature. It was, however, observed that there was comparatively greater departure from good superposition in the creep compliance curve for oil surroundings in long period creep. The minute changes in activation energy for creep phenomena in different surroundings were observed. The effect of fiber volume fraction on creep behavior was also studied. In addition, a brief investigation of the effect of physical aging was done, with the results clearly showing that smoothness in the creep compliance master curve depends on the degree of physical aging of the matrix resin.

Compressive Properties of Slurry Infiltrated Fiber Concrete under Monotonic and Cyclic Loading

SIFCON (Slurry Infiltrated Fiber Concrete) is a type of high volume fiber reinforced concrete in which fibers are preplaced in the mold or on a substratum and infiltrated with cement-based slurry under vibration. The effect of fiber volume fraction on the compressive properties of SIFCON under monotonic loading is investigated in this paper. The compressive properties of SIFCON under cyclic loading are also studied and compared with that of SIFCON under monotonic loading.

Micromechanical Modelling Of Metal Matrix Composites Subjected To Combined Thermal And Shear Loading

Finite element micromechanical models have been developed to investigate the behaviour of unidirectional fibre reinforced composites with thermal residual stresses subjected to transverse and axial shear loading. Appropriate Representative Volume Elements (RVEs) have been chosen in order to apply both thermal and shear boundary conditions simultaneously. Effects of fibre volume fraction and fibre packing arrangement on effective shear moduli were studied. The state of stress was highly influenced by fibre packing, for both the transverse and axial shear cases. The predicted results for effective shear moduli show a good agreement with other analytical models. Elastic-plastic results demonstrate that initiation of yielding in the matrix is highly affected by the thermal stresses.

Effect of fiber fracture and interfacial debonding on the evolution of damage in metal matrix composites

Abstract A new approach for modeling the behavior of laminated composite structures using computational methods is presented, considering damage evolution at the micromechanical level. Micromechanical models are developed to predict the stress–strain response of a composite lamina explicitly accounting for the local damage mechanisms such as fiber fracture and interfacial bonding. The model is applied to metal matrix composites and hence the inelastic constitutive behavior of the matrix phase is included. The stochastic variation of the fiber properties is incorporated in this simulation using the two-parameter Weibull model. The effect of fiber volume fraction and the properties of the fiber, matrix and interface on the damage evolution is studied using this approach. A constitutive damage tensor for the composite lamina is developed from the micromechanical models which can be input into laminate structural analysis codes.

Rheological modelling of short fiber thermoplastic composites

Quantitative analysis of flows of fiber suspensions in viscoelastic matrices, which is the general situation for thermoplastic composites, requires constitutive equations which incorporate specific features of the system and its constituents. Matrix viscoelasticity, fiber orientation and fiber/matrix interactions are key parameters to model such systems. In this work, the constituents of the system are represented by two second order symmetric tensors: c(r, t) for the viscoelastic matrix and a(r, t) for the fiber orientation. The time evolution equation for c(r, t) is developed in the generalized Poisson bracket framework with a finitely extensible non-linear elastic (FENE-P) and a Hookean Helmholtz energy functions. Several expressions for the mobility tensor including expressions with fiber matrix interactions are used. The time evolution equation for a(r, t) is based on the classical Jeffery equation modified to include fiber/fiber interactions in the case of semi-dilute suspensions. The sensitivity of the model to the choice of the mobility tensor together with the effect of fiber volume fraction on the prediction of material functions in start up and steady shear flows are discussed.