Showing papers on "Volume fraction published in 1978"
TL;DR: In this paper, Niobium-Nb wire composites with 0.105, 0.148, and 0.182 volume fraction of Nb filaments were produced in situ and their mechanical properties measured as a function of filament size and interfilament spacing.
Abstract: Cu‐Nb wire composites with 0.105, 0.148, and 0.182 volume fraction of Nb filaments were produced in situ and their mechanical properties measured as a function of filament size and interfilament spacing. The yield stress and the ultimate tensile strength increased with both niobium volume fraction and overall composite reduction. At room temperature, the ultimate tensile strength of the Cu–18.2 vol% Nb composite reduced by 99.999% in cross‐sectional area (100–200 A filament thickness) reached the value of 2230 MN/m2 (323 ksi) and further increased to 2850 MN/m2 (413 ksi) when measured at 77 °K. These values are higher by a factor of 4 than the values predicted by the rule of mixtures based on the highest reported strength of both niobium and copper. The composite strength is as high as that of the best copper whiskers and is shown to closely approach the theoretical strength of the material. The anomalous increase in strength despite the low volume fraction of reinforcing filaments suggests that the filam...
342 citations
TL;DR: In this paper, an attempt was made to relate the hardness of cemented tungsten carbide to its microstructure, and the concept of plastic limit analysis was used to evaluate the effect of the continous carbide phase on the hardness in WC-Co alloys.
328 citations
TL;DR: The relationship between relative viscosity and volume fraction of filler was represented by the equations derived byMaron andPierce orMooney as mentioned in this paper, and yield stresses were estimated, and found to increase exponentially in the range of volume fraction from 0.1 to 0.5.
Abstract: Viscosities of particle filled polymer melts were measured at fairly low shear rate. Particles were glass beads, glass balloons, and silas balloons. Polymers were polyethylene and polystyrene. Flow curves were superimposed with respect to concentration of filler. The relative viscosity defined as the ratio of viscosity of filled polymer to that of unfilled polymer at the same shear stress is obtained as an asymptotic value even for highly filled material. The relation between relative viscosity and volume fraction of filler was represented by the equations derived byMaron andPierce orMooney. Only the distribution of particle size had influence on relative viscosity at a defined filler concentration. Yield stresses were estimated, and found to increase exponentially in the range of volume fraction from 0.1 to 0.5.
158 citations
TL;DR: In this paper, the variation of electrical resistivity of an insulator-conductor composite, namely, waxgraphite composite, with parameters such as volume fraction, grain size, and temperature has been studied.
Abstract: The variation of electrical resistivity of an insulator‐conductor composite, namely, wax‐graphite composite, with parameters such as volume fraction, grain size, and temperature has been studied. A model is proposed to explain the observed variations, which assumes that the texture of the composite consists of insulator granules coated with conducting particles. The resistivity of these materials is controlled mainly by the contact resistance between the conducting particles and the number of contacts each particle has with its neighbors. The variation of resistivity with temperature has also been explained with the help of this model and it is attributed to the change in contact area.
103 citations
TL;DR: In this article, the second law of thermodynamics was applied to the thermomechanics of porous solids through application of a mixture theory, and the pore collapse relation should express the rate of change of either the volume fraction or the distention ratio as an odd function of the difference between the pressure and an equilibrium pressure.
73 citations
TL;DR: In this paper, the occurrence of deformation twins and the residual volume fraction were observed to depend upon peak pressure, P, pulse duration, Δt, and the average grain size of the initial sheet material, D.
62 citations
TL;DR: In this article, the authors examined the dimensional stability of fibrous composites under conditions of elevated temperature cycling and found that the growth of the matrix in the direction parallel to the reinforcing fibers increased with the number of cycles.
Abstract: Dimensional stability of fibrous composites under conditions of elevated temperature cycling has been examined with reference to the familiar model system, tungsten wirereinforced copper. Preferential growth of the matrix in the direction parallel to the reinforcing fibers, the amount of which increased with the number of cycles, was observed in specimens subjected to hundreds of repctitive thermal cycles in the temperature range between 0.35 and 0.8 of the matrix homologous temperature. The amount of growth per unit length after a given number of cycles was found to increase with increasing the holding time at the upper cycling temperature; it was also dependent on such composite variables as the fiber length, fiber diameter, and fiber volume fraction. This observation strongly suggests that interface sliding plays an important role in elevated temperature deformation of this class of material. On the basis of a model which assumes a viscous nature of the phase boundaries, the phenomenon observed is theoretically explained in terms of interfacial sliding-induced relaxation of the internal stress built up in the composite due to differential thermal expansion of the composite constituents.
58 citations
TL;DR: In this paper, the authors investigated the uniaxial tensile stress-strain behavior of longitudinal and transverse texture Zircaloy-2 and −4 specimens over the range of experimental conditions: temperature 700-1400°C, strain rate 10−6-10−1 s−1, oxygen concentration 0.11-2.0 wt.% and grain size 5-55 μm.
53 citations
TL;DR: The in vitro abrasion resistance of seven commercial composite resin restorative materials has been measured and analysis of the composite microstructures shows that abRasion rates are dependent upon the size, hardness, and volume fraction of particles in the material.
Abstract: The in vitro abrasion resistance of seven commercial composite resin restorative materials has been measured. Analysis of the composite microstructures shows that abrasion rates are dependent upon the size, hardness, and volume fraction of particles in the material. The most abrasion-resistant composites contain a high volume fraction of large, hard particles.
52 citations
46 citations
01 Jan 1978
TL;DR: In this article, a random plane section of a 2-phase 3-dimensional opaque specimen X is compared on the basis of bias, mean square error and likely feasibility in practice.
Abstract: It is desired to estimate, for a given phase Y of a 2-phase 3-dimensional opaque specimen X, its volume fraction VV, surface fraction SV and integral of mean curvature fraction KV. Various estimates of these resulting from a random plane section (or sections) of X itself (the RESTRICTED case) are compared on the basis of bias, mean square error and likely feasibility in practice.
TL;DR: In this article, the authors measured the effective thermal diffusivity at room temperature of composites consisting of one phase randomly dispersed in a second phase, based on the flash technique.
Abstract: Measurements have been made of the effective thermal diffusivity at room temperature of composites consisting of one phase randomly dispersed in a second phase. The method is based on the flash technique. Data are presented for four types of composites ranging in particle-to-matrix diffusivity ratios from 0.48 to 1137; in volume specific heat ratios 0.04 to 1.16 and in volume fraction of dispersed particle from zero up to 34%. The results show that the limitations of the concept of an effective thermal diffusivity are far beyond the stiuations to which it is currently applied in the transient state heat conduction problems. Values of effective diffusivities derived from values of the effective thermal conductivity calculated from the Bruggeman variable-dispersion equation are found to agree well with the measured diffusivity values.
TL;DR: In this article, the phase transition in concentrated polymer latex dispersions is discussed in terms of the packing of "effective spheres" consisting of the latex particle surrounded by its electrical double layer, which adds an amount λ/κ to the particle radius.
Abstract: The order/disorder phase transition in concentrated polymer latex dispersions in discussed in terms of the packing of “effective spheres” consisting of the latex particle surrounded by its electrical double layer, which adds an amount λ/κ to the particle radius. For the systems considered here, of 85 nm radius polystyrene particles in KCl, λ is approximately 1.9. The dependence of the Debye screening length 1/κ on particle concentration is examined in an Appendix: the effect is relatively small. If the onset of ordering of the spheres is supposed to commence when the volume fraction of “effective spheres” reaches 0.50, and ordering is complete at a volume fraction of 0.74, then the experimentally observed phase diagram is well reproduced. The effect of particle size on the phase diagram is predicted.
TL;DR: In this article, a cross-linked polystyrene composite whose conductive phase is mica has been measured in order to study in detail interfacial polarization (Maxwell-Wagner effect) in polymer composites with stratified structure.
Abstract: Thermal depolarization current (TDC) of a cross‐linked polystyrene composite whose conductive phase is mica has been measured in order to study in detail interfacial polarization (Maxwell‐Wagner effect) in polymer composites with stratified structure. The volume fraction of mica flakes in the composite was varied from 0.16 to 0.37. A peak characteristic of the composites is observed at a temperature above the Tg of the composites. The maximum current of the peak increases with the fraction of mica flakes. The behavior of the peak is different from that of TDC due to dipole polarization and the space‐charge polarization of injected electrons. The beginning of a dielectric dispersion corresponding to the peak is observed below 1 Hz at 164 °C. The TDC peak can be explained by Maxwell‐type interfacial polarization. It is proposed that the TDC peak is attributed to interfacial polarization due to trapping or localizing of conductive ions in mica flakes at boundaries between the polymer matrix and mica flakes.
TL;DR: In this article, the effects of the amount and distribution of the SiC crystallites on the room temperature properties of the composite were evaluated by measuring the properties of density, elastic modulus and fracture toughness.
Abstract: Silicon/silicon carbide ceramic composites are made by infiltrating carbonaceous material with liquid silicon to form SiC crystallites dispersed in a silicon matrix. The present study was conducted to determine the effects on the room temperature properties of density, elastic modulus, strength, and fracture toughness by varying the amount and distribution of the SiC crystallites. Most of the work involved uniaxially aligned SiC crystals of varying volume fraction tested both longitudinally and transversely to the converted fibre axis.
TL;DR: In this paper, a two-phase microstructure for polycrystalline rutile with an initial second-phase particle size of about 50 A. The dependence of diffusivity and electrical conductivity upon particle size and volume fraction is explained in terms of the alteration of concentrations of transport-related point defects by the transfer of charged species to internal surfaces.
TL;DR: In this article, a selective etching technique was used to reveal the χ-phase in a cast of Type 316 steel (18Cr-12Ni-2.5Mo), and the volume fraction of the particles revealed by this technique was measured by using the Quantimet 720 image-analysing computer.
Abstract: A selective etching technique was used to reveal the χ-phase in a cast of Type 316 steel (18Cr-12Ni-2.5Mo). The volume fraction of the χ particles revealed by this technique was measured by using the Quantimet 720 image-analysing computer. The data obtained suggest that the precipitation of χ at 750°C and 815°C follows a law of the form V = f(t/τ), where V is the volume fraction of χ formed in a time t and τ is a ‘characteristic time’ dependent upon temperature. The kinetics of M23C6 precipitation in Type 316 steel at 625°C was also studied by a bulk extraction method. The data obtained obey the Johnson-Mehl equation with n ≃ 1
TL;DR: In this paper, the gel-effect influences the copolymerization of N-butylmethacrylamide with methylene-bis-acryamide similarly to other vinyl-divinyl copolymers.
01 Dec 1978-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, a spray-dispersion method was developed to produce a steel containing homogeneously dispersed fine oxide particles sprayed from outside into the molten steel stream, and conditions for the distribution of particles in solid steel, and the mechanical properties of A12O3- or ZrO2-dispersed steels were studied.
Abstract: A new technique, Spray-Dispersion Method, which produces a steel containing homogeneously dispersed fine oxide particles sprayed from outside into the molten steel stream has been developed. The conditions for the distribution of particles in solid steel, and the mechanical properties of A12O3- or ZrO2-dispersed steels were studied. The homogeneous distribution of fine oxide particles is obtained by the addition of a certain suitable controlling element which lowers the contact angle of molten steel on various oxides and the interfacial tension at the oxide—molten steel interface. Among others columbium (niobium) was found to be the most effective on decreasing the average particle size of sprayed oxides. Because of fine dispersion of particles of less than 120 nm, the strength of steels increased with their volume fractions; for example, 1.15 vol pct ZrO2 causes an increment of 79 MN/m2 in proof strength and 94 MN/m2 in tensile strength. For practical applications, the Spray Dispersion Method makes it possible to produce 18 chromium-8 nickel austenitic stainless steels dispersion-strengthened by A12O3 or ZrO2 particles, and ThO2-dispersed nickel with an average particle size of 61.4 nm and a volume fraction of 5.1 pct.
TL;DR: In this article, the critical flocculation temperature (c.f.T) of polystyrene latex particles in aqueous solution (2 M NaNO3), in the presence of various molecular weight fractions of poly(vinyl alcohol)(PVA), was studied.
TL;DR: In this article, the authors presented a complete calculational format for stiffness, expansion strain, and yield strength for high density polyethylene (HDPE) and showed that the results were within the necessary design accuracy.
Abstract: Crystalline polymers are heterogeneous materials consisting of two distinct phases. They may therefore be treated as molecular versions of engineering composite materials. This paper summarizes the physical model which, when used in conjunction with composite theory, yields a complete calculational format for stiffness, expansion strain, and yield strength. The important input parameters to the calculation are the mechanical properties of the individual constituent phases (crystalline and amorphous), the crystallite aspect ratios, the volume fraction crystallinity, allowable failure strains for a continuous crystal system, and a measure of stress concentrations and strength reduction caused by the discontinuous nature of the actual crystalline reinforcing phase. An expression for the strength reduction factor is developed and details of the stiffness and yield strength calculations are presented for high density polyethylene (HDPE). Comparison with experiment for HDPE yields excellent agreement well within the necessary design accuracy. Agreement with experiment in the case of low density polyethylene (LDPE) is not as good, but within expectations considering the degree of theory refinement and the poorer morphological data base for LDPE.
01 Sep 1978-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this article, an apparatus for continuous production of partially solidified slurries of Sn-15 pct Pb alloy is described, and the results of earlier fundamental studies carried out on a high temperature viscometer are verified by an extensive number of experiments carried out in this apparatus.
Abstract: An apparatus is described that permits continuous production of partially solidified slurries of Sn-15 pct Pb alloy. The slurries thus produced can be cast into ingots semi-continuously. Results of earlier fundamental studies carried out on a high temperature viscometer are verified by an extensive number of experiments carried out in this apparatus. The three important process variables affecting structure and viscosity of a slurry are: average shear and cooling rates during primary solidification and volume fraction solid in the slurry. Increasing the average cooling rate makes the primary solid particles smaller and more uniform in size, but increases the amount of entrapped liquid in each particle. Increasing the average shear rate affects particle size and uniformity of size similarly, except this effect is noted only at low cooling rates. Primary solid particle size in a vigorously agitated slurry is approximately the same as primary dendrite arm spacing in a conventional casting solidified at equivalent cooling rate. As the volume fraction solid in a slurry increases, so do its primary solid particle size and viscosity.
TL;DR: In this paper, an analysis of the steady one-dimensional flow behind a normal shock wave of a compressible gas containing small spherical particles of solid propellant is presented, and the results stress the importance of the Mach number of the strong shock and the energy content of the propellant (J/kg).
TL;DR: In this article, a lattice resolution TEM was used to study the fine structures of the Si films on (1 1 02) sapphire, where the Si was deposited by pyrolysis of silane in H 2 at 1000°C at a growth rate of 0.1μm/min.
TL;DR: In this paper, the authors compared the modeled conductivity variations with depth in the upper mantle obtained from geomagnetic induction and magnetotelluric results from laboratory measurements on dry material assumed to occur in the mantle.
TL;DR: In this paper, enthalpies of dilution of o-terphenyl in benzene were measured calorimetrically at 288.15, 293.15 and 298.15 K. The enthalpy parameter χH and its dependence on volume fraction calculated from experimental results are reproduced by the linear functions.
01 Jan 1978
TL;DR: In this paper, the authors characterized fracture morphology in B/Al(1100) and B /Al(6061) composite systems at a volume fraction of 0.55 and showed that failure occurs primarily by matrix shear, whereas in the 90 deg fiber orientation, fracture morphology is characterized by a mixture of fiber splitting, ductile matrix fracture and failure at fiber-matrix interfaces.
Abstract: Interfacial reactions, strength degradation, and fracture morphology have been characterized in B/Al(1100) and B/Al(6061) composite systems at a volume fraction of 0.55. Reaction was promoted by isothermal exposure at 350 C or 500 C for times up to 860,000 s. Tetragonal AlB12 was identified as the reaction product in the 6061 matrix and hexagonal AlB2 in the 1100 matrix. Interface development is analyzed based on a moving boundary model modified by the addition of ternary elements. While strength decreases in both systems, the time dependence of elevated-temperature exposure is different in the two matrix materials. In the 45 deg fiber orientation, failure occurs primarily by matrix shear, whereas in the 90 deg fiber orientation, fracture morphology is characterized by a mixture of fiber splitting, ductile matrix fracture, and failure at fiber-matrix interfaces.
TL;DR: In this paper, the volume fraction and distribution function for the case where an external field gives rise to motion of the particles are investigated. But the authors do not consider the effect of particle dissolution on the distribution function.
TL;DR: In this article, the effective coil dimensions with increasing polymer volume fraction φ2 have been measured by gel permeation chromatography for polystyrene standards (2 > 1, φ 2 ).
Abstract: Decrease of the effective coil dimensions 〈r2〉 with increasing polymer volume fraction φ2 has been measured by gel permeation chromatography for polystyrene standards (2 > 1, φ2
TL;DR: In this article, a tentative mechanism of crystalline phase nucleation and growth in supercooled polymer melts is proposed which takes account of density fluctuations in the melt, and a tentative model of the growth rate of spherulitic growth is proposed.
Abstract: Analysis of experimental data on the temperature dependence of spherulitic growth rate from the melt for a number of linear, flexible-chain polymers has shown that the values of surface free energy of basal (fold-containing) face of a crystallization nucleus, σ2, quantitatively correlate with polymer packing coefficient in the crystalline state, Kc in virtually the whole range of variation of these parameters known so far. Also the preexponential term, G0, qunatitatively correlates with the “effective” free volume fraction, (va−vc)/va, where va and vc are polymer specific volume in the amorphous and crystalline states, respectively. A tentative mechanism of crystalline phase nucleation and growth in supercooled polymer melts is proposed which takes account of density fluctuations in the melt.