Showing papers on "Volume fraction published in 1987"
TL;DR: In this article, a Debye-Cole dual-dispersion dielectric model consisting of a component that accounts for the volume fraction occupied by water in free form and another component comprised of water molecules bound to bulk-vegetation molecules is presented.
Abstract: This paper is the second in a series evaluating the microwave dielectric behavior of vegetation material. It draws upon the data presented in Part I to develop a Debye-Cole dual-dispersion dielectric model consisting of a component that accounts for the volume fraction occupied by water in free form and another that accounts for the volume fraction occupied by the mixture comprised of water molecules bound to bulk-vegetation molecules. To determine the dielectric dispersion properties of the latter, measurements were made for sucrosewater solutions of known volume ratios. The proposed dielectric model is found to give excellent agreement with data over a wide range of moisture conditions and over the entire 0.2-20 GHz range examined in this study.
450 citations
TL;DR: Consolidation experiments conducted on special prepregs made of constant viscosity oils and aligned graphite fibers reveal that, to a first approximation, the fiber network can be modelled as a nonlinear elastic network, and a model based on bending beam behavior is shown to accurately fit the data.
Abstract: Consolidation experiments conducted on special prepregs made of constant viscosity oils and aligned graphite fibers are reported. Measurements of the deformation behavior of the fibers in the "drained" state (oil impregnated, but zero pressure in the oil) reveal that, to a first approximation, the fiber network can be modelled as a nonlinear elastic network, and a model based on bending beam behavior is shown to accurately fit the data. Further more, a finite load (> 3 psi) is required to compress the fibers to volume fractions equal to, and above the range of about 0.56 to 0.61. Sample to sample variation, and in a few cases inelastic effects are also noted. Measurements of the permeability of the fiber bundle indicate a strong anisotropy as well as a strong fiber volume fraction dependence. It is shown that the Carman-Kozeny equation gives a good approximation to the axial direction permeability with kxx = 0.7. Compared to this, the transverse permeability is smaller by a factor of 25 or more. Furthermo...
436 citations
TL;DR: In this article, the effects of such parameters as the filler volume fraction, particle size, aspect ratio, modulus and strength of filler, resin-filler adhesion and toughness of the matrix on the stiffness, strength and resilience of particulate filled epoxide resins have been evaluated.
Abstract: The effects of such parameters as the filler volume fraction, particle size, aspect ratio, modulus and strength of filler, resin-filler adhesion and toughness of the matrix on the stiffness, strength and toughness of particulate filled epoxide resins have been evaluated. The mechanisms of deformation and rupture in these multiphase materials are discussed, illustrated byin situ mechanical tests in the scanning electron microscope.
245 citations
TL;DR: In this paper, the authors investigated the rheology of strongly-flocculated dispersions of colloidal particles in a continuous network and showed that these networks possess a true yield stress in both shear and uniaxial compression (as realised in a centrifuge).
Abstract: The rheology of strongly-flocculated dispersions of colloidal particles has been investigated at particle concentrations where a continuous network is formed rather than a collection of discrete flocs. Such networks are shown to possess a true yield stress in both shear and in uniaxial compression (as realised in a centrifuge). Properties measured as a function of particle concentration and particle size include the yield stresses in shear (σ y ) and compression ( P y ); the limiting and strain-dependent, instantaneous shear moduli G O and G (γ); the elastic recovery at finite strains, and the rate of centrifugally-driven compaction. The yield stresses and moduli appear to show a power-law dependence on particle concentration with G O and P y , having the same power-law index and σ y a somewhat lower one. The data are in part consistent with predictions based on the idea that the networks have a heterogeneous structure comprising a collection of interconnected fractal aggregates. The behaviour as a function of particle size and concentration is however not completely scaleable as might be expected on this basis. Thus, whereas the shear yield stress could be scaled to remove its dependence on particle radius a and volume fraction φ (over the measured range 0.25 μm ⩽ a ⩽ 3.4 μm; 0.05 ⩽ φ ⩽ 0.25) as could the strain dependent modulus (0.25 ⩽ a ⩽ 1.3 μm; 0.08 ⩽ 0.25), the particle-size and concentration dependence of P y and G O could only be scaled for particles with radii between 0.16 and 0.5 μm, smaller and larger particles having different and much higher power-law index in respect of their concentration dependencies. In the case of the smaller particles the failure of the scaling is thought to be due to an anomaly since these particles distort significantly under the influence of the strong van der Waals forces and this causes the aggregates to be more compact then they otherwise would be. The reasons for the failure at larger sizes is not clear.
213 citations
TL;DR: In this paper, a mixture fraction approach was used to measure the volume fraction of a turbulent ethylene diffusion flame and compared with predictions, and the results showed that in the lower parts of the flame this formulation is not adequate.
Abstract: Soot volume fraction measurements are made in turbulent ethylene diffusion flames and are compared with predictions. The theoretical model is based on mixture fraction distributions in the flame and measured soot volume fractions are correlated against predicted mixture fraction. The results show that in the lower parts of the flame this formulation is not adequate. However, the maximum soot concentrations further up the flame are less dependent on residence time and a mixture fraction approach may be useful here.
156 citations
TL;DR: In this paper, a novel method for enhancing the coercivity of magnetic materials has been demonstrated, where granular Fe solids have been fabricated over a wide volume fraction range from 15% to 100%.
Abstract: We demonstrate a novel method for enhancing the coercivity of magnetic materials. Granular Fe‐(SiO2) solids have been fabricated over a wide volume fraction range from 15% to 100%. Giant magnetic coercivity, as high as 2500 Oe, has been observed in granular solids in which the isolated Fe granules are only nanometers in size. Across the whole volume fraction range magnetic coercivity experiences dramatic variations due to the change of granular size and percolation effects.
151 citations
TL;DR: In this paper, optical and electronic properties of composites of soluble polythiophene derivatives and polystyrene over the full range of composition were reported, and the composite films were prepared by evaporating the solvent in an inert atmosphere from a solution containing both polymers.
141 citations
TL;DR: The dynamic mechanical properties of unidirectional glass-fiber-reinforced polyester measured along the fiber direction were recently investigated in this article, showing that the interfacial shear strength and the tan δ at the glass-transition temperature of the polyester showed good correlation suggesting that the latter can be used to characterize the quality of the interphase factors.
Abstract: The dynamic mechanical properties of unidirectional glass-fiber-reinforced polyester measured along the fiber direction were recently investigated In the same polyester, the type of organosilane coated on the glass fiber, the amount of organosilane, the fiber volume fraction, and the fiber diameter affect the value of the loss tangent, tan δ, at the glass-transition temperature of the glass-fiber-reinforced polyester The interfacial shear strength and the tan δ at the glass-transition temperature of the glass-fiber-reinforced polyester show good correlation suggesting that the latter can be used to characterize the quality of the interphase Factors affecting the glass-transition temperature and the application of Zorowski and Murayama's equation in the characterization of the interfacial adhesion are also discussed
138 citations
95 citations
TL;DR: In this paper, an analytical model that accounts for the different variation of the limiting grain radius with volume fraction of particles found in previous computer simulations as compared to the classic Zener predictions is presented.
93 citations
Journal Article•
TL;DR: In this article, the dependence of the shear modulus on the volume fraction φ was measured for volume-filling networks formed by Brownian flocculation of aqueous polystyrene latices.
TL;DR: In this paper, the effective thermal or electrical conductivity of a suspension of monodisperse spherical particles embedded in a matrix of different conductivity is computed for the case when there exists a finite resistance at the particle-matrix interface.
TL;DR: In this paper, the effective elasticity tensor of a composite medium consisting of spherical elastic particles firmly embedded in a periodic cubic arrangement into another elastic medium is characterized by three scalars α, β and γ.
Abstract: T he effective elasticity tensor of a composite medium consisting of spherical elastic particles firmly embedded in a periodic cubic arrangement into another elastic medium is characterized by three scalars α, β and γ. We employ a method of singularity distribution and determine these scalars for various values of volume fraction of the spheres and the Lameconstants of the particles and the matrix. The results, which are presented for the simple, body-centered and face-centered cubic arrays, are in agreement with the previously known results of Nunan and Keller (J. Mech. Phys. Solids32, 259, 1984) for the rigid particles and of Iwakuma and Nemat - Nasser (Computers and Structures16, 13, 1983) for the non-rigid particles.
TL;DR: The S values derived from the dependences of log k' on the volume fraction of the low ionic strength buffer, phi b, were of the same magnitude as reported for porous HIC silicas and showed a dependence on the molecular weight of the protein.
TL;DR: In this article, the authors consider the various adsorption regimes of flexible polymer chains in a good solvent when the bulk concentration is changed and calculate the interfacial tension in the different regimes.
Abstract: We consider the various adsorption regimes of flexible polymer chains in a good solvent when the bulk concentration is changed. As the latter is increased, first we find a very dilute bulk regime where the surface coverage increases fast. This is followed by a plateau with much slower increase for Γ, the bulk solution being still dilute. In the bulk semi-dilute regime, we consider the adsorption of blobs. For high bulk volume fraction, ϕ b > δ4/3, where δ is the dimensionless excess energy per monomer on the surface, the blobs are not adsorbed. The interfacial tension is calculated in the different regimes. Our approach closely follows the scaling theory of de Gennes and Pincus.
TL;DR: In this article, a model for the restraining effect of second-phase inclusions on an advancing crack front in a brittle matrix is presented which incorporates a parameter characterizing the relative ease of cutting through or circumventing the second phase, compared with matrix cracking.
TL;DR: The mechanical behavior of composite gels consisting of spherical deformable filler particles (Sephadex beads) embedded in a gelatin gel matrix has been investigated in this article, where failure properties of the composite were controlled by altering the chemical affinity between filler and matrix.
Abstract: The mechanical behavior of composite gels consisting of spherical deformable filler particles (Sephadex beads) embedded in a gelatin gel matrix has been investigated. The shear modulus of composite gels is dependent on the shear modulus of the matrix, the deformability of the particles, and their volume fraction. Under uniaxial compression, at high strains, the importance of the filler‐matrix interface in influencing the strength of the composites was demonstrated. Failure properties of the composite were shown to be controlled by altering the chemical affinity between filler and matrix. Studies with a composite food starch gel showed similar dependence on the previously identified parameters.
TL;DR: In this article, the volume fraction, X, of the conducting phase in a granular structure defined in the carbon matrix and applicable to heat treated biomass carbons is calculated as a function of structural parameters obtained from X-ray diffraction and small-angle Xray scattering measurements.
TL;DR: In this article, the effects of such parameters as the filler volume fraction, particle size, aspect ratio, modulus and strength of filler, resin-filler adhesion, and toughness of the matrix on the stiffness, strength, and resilience of epoxy resins were evaluated.
Abstract: The effects of such parameters as the filler volume fraction, particle size, aspect ratio, modulus and strength of filler, resin-filler adhesion, and toughness of the matrix on the stiffness, strength, and toughness of particulate-filled epoxy resins were evaluated. The mechanisms of crack initiation and subsequent crack propagation in these multiphase materials are discussed and illustrated by scanning electron microscopy of fracture surfaces.
TL;DR: In this paper, the effect of particle volume fraction on the dielectric response of concentrated latices in the frequency range 1-10 MHz was investigated, and it was found that the measurements on suspensions with a volume fraction of 0.3 or more are in accordance with a result obtained using a cell model, but these may be due to errors in our measurement of the particle contribution to the complex conductivity at these low volume fractions.
TL;DR: In this article, a modification of Saito's formula is presented, in which a function of the volume fraction is added containing the effects due to correlations and the hydrodynamic interactions between the spheres.
TL;DR: In this article, the average drop size in a mixing vessel changes from breakup to coalescence when the average energy dissipation rate or the volumetric fraction of dispersed phase is increased.
Abstract: When two immiscible liquids are agitated, a dispersion is formed in which continuous breakup and coalescence of drops occur, and a dynamic equilibrium is attained between breakup and coalescence after a certain time. Effects of the volume fraction of dispersed phase, viscosity of liquid, impeller speed and impeller-to-vessel diameter ratio on the average drop size of a dispersion in a mixing vessel are discussed and correlative equations are proposed. It is also found that the dominant process in deciding average drop sizes in a mixing vessel changes from breakup to coalescence when the average energy dissipation rate or the volumetric fraction of dispersed phase is increased.
TL;DR: In this article, a sharp ultrasonic velocity maximum and compressibility minimum is observed at low BE concentration in mixtures of water-BE at all temperatures. But the authors attributed the formation of "clathrate-like" structures of water and alcohol.
Abstract: Ultrasonic velocity and density data of binary systems of water–2-butoxyethanol (BE), 2-butoxyethanol-benzene, and 2-butoxyethanol–decane are reported for temperatures of 25, 40, and 55 °C. Adiabatic compressibility coefficients, apparent molar volumes, and apparent molar compressibilities were calculated from these data. Excess adiabatic compressibility properties were evaluated using volume fraction weighting of the individual component properties to estimate ideal mixture behavior. These results are compared with the data obtained based on the use of mole fraction weighting of the individual component properties for the ideal behavior value. A sharp ultrasonic velocity maximum and compressibility minimum is observed at low BE concentration in mixtures of water–BE at all temperatures. These maxima in ultrasonic velocity and minima in adiabatic compressibility are attributed to the formation of "clathrate-like" structures of water and alcohol. A shift of the velocity maximum towards lower concentrations ...
01 Jan 1987
TL;DR: In this paper, the attenuation of a solid containing a distribution of voids was investigated and a physical model was developed for evaluating the average size and the volume fraction of porosity in cast aluminum.
Abstract: The ultrasonic attenuation of a solid containing a distribution of voids depends on the number of voids per unit volume and the ultrasonic scattering cross-section of the voids. This physical picture has been shown to provide an accurate description of the attenuation behavior of ultrasound in metals containing low level porosity. For example, methods developed from this model for evaluating the average size and the volume fraction of porosity in cast aluminum have yielded good results [1].
TL;DR: A small group of materials, incorporating substantial amounts of quartz or silicon nitride filler particles, exhibited high rates of thermal diffusion, up to three times the level exhibited by dentin.
Abstract: The substantial increases in the filler volume fraction of the current generation of composite resins, and the incorporation of radiopacifying heavy elements in many of these fillers, constitute significant changes which may affect thermal transport properties. Thermal diffusivity has been determined for 21 of these composite materials recommended for anterior and posterior applications. For radiopaque hybrid and for microfine composites, there was, however, only a gradual trend to increased thermal diffusivity with increasing volume fraction of inorganic filler. These diffusivity values were not greatly in excess of the level observed for dentin. Nevertheless, a small group of materials, incorporating substantial amounts of quartz or silicon nitride filler particles, exhibited high rates of thermal diffusion, up to three times the level exhibited by dentin.
TL;DR: In this article, the dynamics of a probe chain consisting of nP =100 segments in a matrix of chains of length of nM = 50 up to nM=800 at a total volume fraction of polymer φ = 0.5 have been simulated by means of cubic lattice Monte Carlo dynamics.
Abstract: The dynamics of a probe chain consisting of nP =100 segments in a matrix of chains of length of nM=50 up to nM=800 at a total volume fraction of polymer φ=0.5 have been simulated by means of cubic lattice Monte Carlo dynamics. The diffusion coefficient of the probe chain over the range of nM under consideration decreases by about 30%, a behavior rather similar to that seen in real melts of very long chains. Furthermore, the analysis of the probe chain motion shows that the mechanism of motion is not reptation‐like and that the cage effect of the matrix is negligible. That is, the local fluctuations of the topological constraints imposed by the long matrix chains (even for nM=800) are sufficiently large to provide for essentially isotropic, but somewhat slowed down, motion of the probe, nP =100, chains relative to the homopolymer melt. The results of these MC experiments are discussed in the context of theoretical predictions and experimental findings for related systems.
TL;DR: In this paper, the diffusion of water in carbon and glass reinforced epoxies was investigated over a range of humidities from about 33 to 97%, by immersion, and at temperatures in the range 23 to 100°C.
Abstract: The diffusion of water in carbon and glass reinforced epoxies was investigated over a range of humidities from about 33 to 97%, by immersion, and at temperatures in the range 23 to 100°C. (The water absorption properties of the resins themselves were described in the first paper of the series.) The composites obeyed Fick's law, that is, water absorbed was determined by the square root of the immersion time during the initial absorption. The volume of water absorbed at equilibrium by the composites was usually determined by the polymer matrix volume. Where there were exceptions to this, there was evidence of water being concentrated at the fiber-matrix interface. The results otherwise indicated that there was a linear relation between water absorbed at the interface and the temperature. Diffusivities decreased linearly with the square root of fiber volume fraction for both carbon and glass fibers, and under all conditions tested. The fibers thus appeared to act as barriers to diffusion. However, there was strong evidence that these composites had regions with enhanced diffusivity.
TL;DR: In this article, the phase transition of polystyrene latices is predicted by a statistical mechanical theory and the densities of each phase are measured by measuring the steady shear viscosity and linear viscoelastic response at fixed polymer concentration.
Abstract: We present an experimental study of the rheology of polystyrene latices phase separated by dissolved dextran polymer. Our phase‐transition experiments are guided by a statistical mechanical theory which predicts this phase transition and the densities of each phase. Measurements of the steady shear viscosity and the linear viscoelastic response at fixed polymer concentration well into the two‐phase region define the dependence on latex volume fraction. Viscoelastic properties of the separated dense phase near the phase boundary (at equilibrium) are also presented. A low frequency plateau in G′ and an apparent yield stress appear for samples in the two‐phase region and increase exponentially with volume fraction of particles.
TL;DR: In this article, magnetic particles of iron oxide were blended into portions of a high molecular weight sample of poly(dimethylsiloxane) which were then peroxide cured in a magnetic field.
Abstract: Magnetic particles of iron oxide were blended into portions of a high molecular weight sample of poly(dimethylsiloxane) which were then peroxide cured in a magnetic field. Strips cut from the resulting elastomers parallel and perpendicular to the magnetic lines of force were studied with respect to their equilibrium swelling and their stress–strain isotherms in elongation. Both resistance to swelling (as measured by the volume fraction of polymer in the network) and the elongation modulus increased with increase in the amount of filler. They were also generaly larger in the direction parallel to the field, and the differences increased both with increase in the amount of filler and with increase in the strength of the magnetic field. Stress relaxation also increased with amount of filler and field strength, thus illustrating the importance of adsorption of the polymer onto the filler particles, and its subsequent desorption under stress.